PrHEP hep2001 = s -pair √ W each at 1 − per experiment at the highest ’s produced in association with 1 W − International Europhysics Conference on HEP eve 23, Switzerland per experiment at a centre-of-mass energy above the 1 − 208 GeV. ' s per experiment, of which about 8 pb ∗ √ Most recent results from the searches for new particles at LEP, Tevatron and 1 − fabiola.gianotti@cern.ch PROCEEDINGS HERA, presented at themachines 2001 (LHC Summer Conferences, and are Linearquest reviewed. Colliders) for are Prospects Higgs also at bosons,tral discussed. future Supersymmetry, Current Extra-dimensions processes. and The In Flavour-Changing emphasis eachstrategies, Neu- is case, and the put the phenomenological on analysis framework, thevarious the methods experimental machines are are described, compared. and the sensitivity and reach of the Abstract: The Tevatron experiments CDF and D0 have collected about 110 pb Since 1996, i.e. since the beginning of its phase two, LEP has delivered an integrated Speaker. hint in the search for a Standard Model (SM) Higgs boson of mass about 115 GeV, and ∗ CERN, EP Division, 1211E-mail: Gen` 8 TeV during Run 1. Run 2 has started in Spring 2001 at a centre-of-mass energy of . σ 1 useful energy of production threshold. Thewent machine beyond performance any in optimistic termsin expectation. of the Most both year relevant energy 2000 toabout and searches (the 130 luminosity are last pb the year data of recorded operation) at centre-of-mass energies above 206 GeV, a high transverse momentum hadronic system. luminosity of about 700 pb the H1 experiment at HERA has observed an excess of 1. Introduction The search forfields new in particles today’s is high-energytheoretical scenarios one experimental and physics, of predictions. motivated Over theColliders, the also LEP, last Tevatron most and by years, HERA, exciting, the have a three exploredset rich operational the rapidly-evolving stringent few high-energy spectrum bounds hundred and on GeV of various energy prolific models. range2 and In addition, recently LEP has reported an exciting Fabiola Gianotti Searches for new particles at Colliders PrHEP hep2001 . until 75%) 1 − 1 s ∼ − 2 ; two jets 115 GeV, − ν ν ∼ cm . It should be boson through 206.6 GeV. In → . Prospects at q 31 1 Fabiola Gianotti q Z Z ≥ 10 · → s and Z √ b b (branching ratio and → b ; and two jets and two taus b H ττ → . Only results from Run 1 have 1 → − ee, µµ ), if H s 2 H → − Hνν or Z , which is the channel with the largest cm q q ττ 32 . If the Higgs mass is indeed and 10 → b → · ZH b –2– Z Z → → ∗ H and and Z b b b b → ), if 7%). Therefore Higgs production at LEP should give rise − → → e ∼ H`` + H H e [1]. Before discussing the updates to this result at the time of σ ), if Hqq ), if either (branching ratio qqττ ττ → H Most recent results from the searches for new particles at LEP, Tevatron and HERA, This paper is organised as follows. The quest for the SM Higgs boson, in particular At HERA, the H1 and ZEUS experiments have both collected about 135 pb At LEP, a SM Higgs boson is mainly produced in association with a It would be impossible to describe in one paper the impressive amount of search studies and results 1 115 GeV. At the end of data taking, on November 3rd 2000, the four experiments reported presented at the 2001 Summer Conferences, are reviewed in this paper September 2000, at a centre-of-mass energyin of Autumn up 2001 to 318 with GeV. an Data taking upgraded has machine started and again a luminosity goal of 7 reported at this Conference. The reader is therefore referred to other contributions to these Proceedings. the CERN Large Hadron Colliderbriefly. (LHC) For and each at topic, future thethe Linear phenomenological analysis Colliders framework, methods the are are also experimental described,are discussed strategies and compared. and the sensitivity and reach of the variousthe machines recent LEP hint,nism is and described possible in solutions sectionthe searches beyond 2; for the Supersymmetry problems (SUSY), Standard related Extra-dimensionsCurrent and Model to (FCNC) Flavour-Changing processes Neutral the are are SM briefly presentedof Higgs in recalled sections the mecha- in 4 H1 section to excess 6, 3; in and section are followed 7, by and a by discussion some conclusions in section 8. this mass range, the dominant Higgs decay modes are been presented at this Conference. and two leptons final states ( about 35 events have been produced at LEP in the year 2000 at noticed that LEP isunlike sensitive to Hadron most Colliders topologies where arising fully from hadronic Higgs final production states and are decay, difficult to extract from the the Higgsstrahlung process the 2001 Summer Conferences,are the briefly Higgs recalled. phenomenology at LEP and the search methods 2. Search for the Standard ModelAs Higgs of boson today, theLEP. only Using relevant the results dataexperiments from collected were the able until to search 1999, setthe for a in year a lower 2000, which limit SM when on no Higgs thean the signal Higgs excess machine boson had mass was of come of running events been 107.9 from was at∼ found, GeV observed, a at consistent the centre-of-mass 95% with energy LEP C.L.. the abovea In production 205 combined of GeV, excess a of Higgs 2.9 boson of mass International Europhysics Conference on HEP 2 TeV and with a luminosity goal of up to 5 and to four main final(indicated states, here addressed as by as many dedicated searches: four jets final states sensitivity; two jets and missing energy final states ( final states ( PrHEP hep2001 must 7 Fabiola Gianotti production, which WW -quark content of an event b and Reconstructed Higgs boson mass, ZZ Figure 2: as obtained from(dots the with year error 2000(top), bars) LEP a by data medium applying (middle)tom) a and selection loose a [2]. tightground (bot- The (light-shaded expected histogram) SM andsignal back- Higgs for a masshistogram) are of also 115 shown. GeV (dark-shaded –3– L3 preliminary -boson in the final state and the event kinematics. Z , unlike at Hadron Colliders where rejections of up to 10 3 (GeV)  s − √ ) γ W ( + − qq W ZZ HZ 0.85 >

→ → → → s   ´/ − − − −  s e e e e √ = 115 GeV e + + + + H e e e m Cross-sections of several SM pro- -jets and of a b 80 100 120 140 160 180 200 3 2 4 -1 1

10 10 10 10 Cross section (pb) section Cross 10 Figure 2 shows the reconstructed Higgs mass spectra from the data collected by the four Although the reconstructed mass spectra are graphically intuitive and simple to un- production is dangerous in two cases: when final-state gluon radiation gives rise to a Figure 1: cesses, as a function of theergy, centre-of-mass as en- measured by L3 (dots).show The the full theoretical lines prediction.line The indicates dotted the expecteda Higgs cross-section boson for of mass 115 GeV. q be achieved. Suchpresence a of rejection is obtained at LEP by using several handles, such as the LEP experiments in thea year loose 2000 selection, [2], after amore applying signal-like medium sample three selection, is special selected, andmagnitude non-biasing and a of a selections: tight slight this excess selection. excess becomesalso is shown visible When compatible in at cuts high with the are masses. figure. the tightened, low The rate a expected fromderstand, they a are possible only signal, all one the of information several discriminating whichprocesses. variables can and be Other by used discriminating farand to do features its distinguish not are topology. contain a for In Higgs particular, instance for signal the a from signal the at the background limit of the kinematic reach of a machine, four-jet topology, and whenbeam initial-state pipe photon mimics radiation theprocesses, with two measured jet the by plus the photon(s) L3together missing lost experiment with energy as in the topology. a cross-section the function expected Thethat of for cross-sections energy, the a are for Higgs main displayed boson these in backgroundsis of figure are at mass 1 115 globally most GeV. a well It factor can understood, be of and seen 10 that the needed rejection yield events containing fourq jets, jets and leptons, jets and missing energy. In addition, International Europhysics Conference on HEP background. At LEP, backgrounds arise mainly from PrHEP hep2001 Q for Q 2ln to the for two − is small, 2ln Q Q −∞ − 2ln . distribution for − i Fabiola Gianotti Q in the data. , as expected from i 2ln Q − Examples of probability : Q 2ln ) observed in the data, and  i i − b s cand ,seetext. b )istheintegralofthe N b + 1+ s  CL Figure 3: distributions fortimator thesimulated background-only statistical experiments es- (light-shaded) andsignal+background experiments fromtogram). (his- The simulated dark-shadedCL area defines ln − indicates a signal-like observation. The =1 cand b i X N 2 i CL is large, and the distribution of b − i ) is the integral of the − b s + b –4– Q i + s ,whichal- s for background-only experiments peaks at positive Q Q 115 GeV at LEP, the number of events expected is )=2 CL =1 cand H i Y ∼ N 2ln m ) ( is simply the ratio b − b + s Q Q − ( e − e 2ln − = ) observed by an experiment is positive, then the background-only b ) b + Q ( s L ( ): L 2ln b ) and for the signal+background hy- b − + ( )= s L ( H are the numbers of signal and background events expected with all the features , the likelihood ratio L i m H b ( m where the ratio in theFigure parenthesis 3 is called is the a “weight” of schematic candidate illustration of the expected distributions of Numerically, it is more convenient to take the logarithm of Here the product runs over the number of candidates ( For this reason the LEP experiments use a sta- Q and -tagging, kinematics, reconstructed Higgs mass, etc.) of candidate i b s and therefore the distribution of values. If there is a signal in the data, classes of simulated experiments: experiments observingobserving only a background, and signal experiments on top of the background. If there is no signal in the data, distribution for an ensembleobserved of value simulated background-only in experimentssignal-like the from than data, the observation. and A gives small the 1 probability that such experiments are more signal+background confidence level ( an ensemble of simulated signal+background experiments from the observed value in the ( of the Poisson probabilities for thehypothesis background-only pothesis lows all the relevant features ofdates the in observed the candi- data to beses: compared with that two hypothe- theseonly, candidates and come that they fromand come background background. from a mixture Formass a of signal given hypothetical Higgs tistical estimator, the likelihood ratio International Europhysics Conference on HEP as is the case for a Higgs of mass small and clear massbest peaks all can the not informationpotential be contained signal. observed. in the It data, is in therefore order important to to maximise use the at sensitivity the to a signal+background experiments isthe expected value to of be in the negative region. Therefore, if hypothesis is favoured, otherwise thequantify signal+background the hypothesis compatibility is of favoured. thedefined. To observation better with The these background-only two confidence hypotheses, two level numbers (1 are PrHEP hep2001 . b σ Q σ σ σ CL 2 3 4 ) 2ln 2 − − (GeV/c H m LEP Fabiola Gianotti of the LEP data as a function of Observed Expected for signal+background Expected for background The background-only confidence b CL − 100 102 104 106 108 110 112 114 116 118 120

-1 -2 -3 -4 -5

1 b 1-CL 10 10 10 10 10 the Higgs test mass. Theobservation, solid the line dashed line shows the the background- only expectation, andthe the signal+background expectation dash-dotted [2]. line Figure 5: level 1 –5– ) 2 indicates a signal-like observation. b + s (GeV/c H m CL ) spread of the back- σ 2 ± ( ) is 43%. Both figures show that the excess is not a sharp minimum, but b σ . For this same mass value, the confidence level of the signal+background 1 + of data, which were not yet analysed on November 3rd, and only one new s σ as a function of the Higgs test ± 1 LEP Observed Expected background Expected signal + background Distribution of the log-likelihood Q , and gives the probability that such experiments are more background-like − CL ∞ 2ln as a function of the Higgs test mass shows a minimum in the signal+background − Q 100 102 104 106 108 110 112 114 116 118 120 reported on November 3rd 2000, which was based on preliminary analyses, to the 2.1

5 0 There are several reasons why the significance of the excess has decreased from the The results obtained at LEP are summarised in figure 4. The observed distribution of

-5 25 20 15 10 -2 ln(Q) -2 σ -10 -15 Figure 4: ratio mass for the LEP data.the The observation, solid line thedian shows background dashed expectation, and linedotted the dash- the line the me- expectation. median signal+background The darkindicates (light) the shaded band ground expectation [2]. 2ln presented at the 2001 Summerabout Conferences 15 (table 1). pb The four experiments have included 2.9 extends at lower masses.from mass This resolution behaviour effects is [2]. expected in the signal hypothesis and comes significant candidate has beenthe found correlation (by between OPAL). ALEPH the has discriminating improved variables the used treatment of for the calculation of L3 has optimised thehas search produced analyses for more the Montesequence, four-jet Carlo the and events weight missing-energy at of final the the states best correct and L3 centre-of-mass candidate, energies. a missing-energy As event, a has con- decreased from region, thereby indicating aminimum deviation is from found the forHiggs background-only signal hypothesis. a of mass the The of same exact mass. 115.6 The GeV excess and is coincides also visible with from the the expectation small values from of a 1 − (figure 5). In particular, forhypothesis, a mass i.e. of 115.6 the GeV probability thean confidence of level excess a of of the background 2.1 background-only fluctuation, is 3.5%, which corresponds to hypothesis ( International Europhysics Conference on HEP data to + than the observation. A large PrHEP hep2001 b + s 0.94 0.02 0.47 0.83 0.47 0.43 0.07 CL ratio. The b s/b CL Fabiola Gianotti 0.87 0.22 0.49 0.24 − 0.002 0.035 0.0037 1 For a Higgs test mass [2] [3] [6] [5] =0.77 [4] σ σ σ σ b L3 LEP ALO DLO 2.1 3.0 1.3 1.0 OPAL CL ALEPH DELPHI Table 2: of 115.6 GeV,the confidence background-only and levels of of thenal+background sig- hypotheses for the individual experimentscombination. and The their resultsby obtained combinining DELPHI,OPAL (DLO) L3 and and ALEPH,OPAL L3 (ALO) and are also shown. − 1 σ 2001 Summer Conferences 114.8 GeV –6– > =0.68 σ σ σ σ b H m 2.9 3.4 1.3 1.8 CL − 1 November 3rd 2000 115.6 GeV. If the most background-like experiment (DELPHI) is ∼ L3 OPAL ALEPH DELPHI =0.7 between November 2000 and Summer 2001. In addition, the data of all LEP combined s/b . It is therefore not surprising that one of σ Significance of the events observed by the individual LEP experiments, and their combi- Some features of the fifteen most significant candidates for a Higgs test mass of 115 GeV The sharing of the excessALEPH among the is experiments signal-like, can with be an deduced from excess tables of 1 about and 2. 3 =1.6 to at the 95% C.L., iscess not at able to a exclude mass the ALEPH of ex- are listed in table 3. ALEPH has three very pure four-jet events with a large ignored, the combination offrom the a other background three fluctuation experiments of (ALO) 0.4%. has a probability to come first two contribute aboutis half of due the to observed smaller LEP excess, weight whereas events the distributed rest among of the the excess four experiments and the decay obtained with both a neurala network based simpler analysis cut-based and analysis [3].hand, DELPHI, is on background-like, the other fer whereas L3 slightly and the OPALbackground-only hypothesis. signal+background pre- This spread hypothesis of results among tothe four the experiments is notence incompatible with of the a pres- signalshown with in these figure small 5,not statistics. each the of Indeed, four them as experiments individually,level have together, a of sensitivity and 2 at the them is signal-likeTable and 2 another also shows onement that (ALEPH) background-like. is if ignored, the thethree most combination of signal-like experiments the experi- other (DLO)background-only is hypothesis. well However, compatible theon with lower the limit the Higgs mass obtained by DLO, Table 1: nation, for a Higgs massConferences. of 115 GeV, as reported on November 3rd 2000 and ats/b the 2001 Summer experiments have been reprocessedties with (related, refined e.g., calibrations, tohave many the been systematic detector scrutinised performance uncertain- and andHiggs studied to working in the group knowledge detail, [2], ofshould and in the be a particular backgrounds) noticed lot many that of cross-checks only work among the has the L3 been four result done experiments. in in table It the 1 LEP is final. International Europhysics Conference on HEP PrHEP hep2001 Q 2ln − to s/b 45 GeV) and -quarks in the b ∼ Fabiola Gianotti probability of the 2 4.7 2.3 0.9 0.6 0.6 0.5 0.5 0.5 0.4 0.3 0.3 0.3 0.7 0.7 0.4 χ channel is consistent at 115 GeV probability for the fit of s/b 2 Hqq χ decay. Z in the data collected in the year σ (GeV) 97.2 114.3 112.9 110.0 110.7 114.3 118.1 115.4 114.5 112.6 114.4 103.0 104.0 115.0 108.3 rec H -tagged have energies ( hypothesis gives a m b mass. The event energy flow is very well HZ Z . The best background explanation would be hypothesis gives a Z –7– -jets, which come from the Higgs boson candidate, H`` Hqq Hqq Hqq Hqq Hqq Hqq Hqq Hqq Hqq Hqq Hqq Hνν Hνν qqττ b ZZ 1 GeV at the 95% C.L., i.e., taking into account also Final state . 114 -jets, where also a muon is observed, thereby indicating a b > L3 L3 H OPAL OPAL OPAL ALEPH ALEPH ALEPH ALEPH ALEPH ALEPH ALEPH ALEPH m DELPHI DELPHI Experiment production, where the two gluons are radiated by the -tagged (two well-reconstructed displaced vertices can be seen in figure 6). bgg decay. A kinematic fit to the b b 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 b 0 GeV, whereas the reconstructed mass of the two other jets before kinematic → . 3 b Candidate Properties of the fifteen candidates contributing with the highest weight b ± 3 → . In conclusion, LEP has observed an excess of about 2 A graphical display of the event with the largest weight is shown in figure 6. It was The reconstructed mass of the two − e + for a Higgsreconstructed mass Higgs of mass 115 and GeV. the weight For are each listed. candidate, the experiment, the final state topology, the fit of about 53%, whereas a fit to the 1% and a mass of 102 GeV for one of the e invariant mass (92.1 GeV) compatible with coming from a 2000 at a centre-of-mass energylike above Higgs 205 boson, GeV. If the thisfluctuation preferred excess is mass is value due 3.5%. is toexperiments a 115.6 The signal together GeV. lower from is The a limit probability SM- on of the a background Higgs mass obtained by combining the four final state. However, the two jets which are not fit, 92.1 GeV, is very close to the nominal collected by ALEPH at awhich centre-of-mass are energy well of 206.7 GeV, and contains four jets, twois of 114 reconstructed, as demonstrated alsoin by the the fact direction that of thesemileptonic one missing momentum of vector the points Table 3: International Europhysics Conference on HEP channels. The large number of significant candidates in the with the signal hypothesis,sensitivity. since the four-jet final state provides the largest experimental PrHEP hep2001 θ per sin 1 φ − − (dots), θ 1 3 σ 5 − 10 (triangles) (GeV) H 1 m − Fabiola Gianotti ATLAS + CMS (no K-factors) ) θ o o − −−47)*SIN( o o o x − φ o 0.3cm x − − x o o x o o o x o − o 0 − o -1 o x − -1 -1 x x o o o 2 o − o 10 − L = 10 fb L = 30 fb L = 100 fb o o o o x − x µ − x o x o o o x − Expected signal significance as a o o x o −o o x o x 2 −0.3cm (squares) and 100 fb x 1

− 10 10 1cm 0

P>.20 Z0<5 D0<2 NT=4 man.cut

− YX 1 Signal significance Signal x − =180 =0 ( θ θ Figure 8: function of the Higgsfor mass integrated luminosities at of the 10 LHC fb [8], per experiment. Thethe vertical LEP limit. line indicates 30 fb –8– Run=54698 Evt=4881 Run=54698 Evt=4881 level (middle σ ALEPH level (upper band), as a σ The integrated luminosities per Display of the most significant LEP Higgs boson candidate, collected by ALEPH [3] on The Tevatron experiments CDF and D0 had little sensitivity to a SM Higgs signal in band) and at the 5 function of mass [7]. Theindicates width the of systematic each uncertainty. band experiment needed at the Tevatron Runexclude a 2 SM to Higgs boson atband), 95% C.L. to (lower discover it at the 3 Figure 7: view and in zoom of the vertex region. 115 GeV can be excluded at the 95% C.L. with an integrated luminosity of 2 fb previous LEP results, theshould be mass noted range that betweenbound in zero on 1989, the and when SM this LEP Higgs started limit boson to is mass. collect excluded data,Run today. there 1, was but It in no Run compelling opens 2 interesting the luminosity prospects is [7]. expected to These be are larger summarised by a in factor figure of 7. up to Higgs 100, which masses close to Figure 6: June 14th 2000. The event is shown in the view transverse to the beam direction, in the International Europhysics Conference on HEP PrHEP hep2001 1 − ,which ,which b 120 GeV 115 GeV, b γγ ∼ significance ∼ → → σ H beam is needed H H m Fabiola Gianotti p . As shown in figure 8, 1 ) the discovery potential . − 1 b − `νb and looks therefore difficult. 1 observation for → − final state. production with σ ` Linear Collider [9]. 4 WH discovery up to masses of tH − t e → σ + e H 185 GeV. Discovery for masses larger than ∼ needed for a 3 –9– 1 − for the above-mentioned Higgs mass and luminosity. required for a 5 σ 1 − to about 7 σ ) at both machines. However, the LHC studies are quite conservative [8] σ 5 ∼ values close to the LEP limit. In this mass region, which is the most difficult one discovery. Although it is obviously not easy to tell today who will discover the Higgs σ H The year 2007 could therefore be a very exciting one since, if the Higgs mass is indeed As already mentioned, for masses larger than 120 GeV the LHC has no competition On the time scale of 2007 the LHC should become fully operational. The most recent m and, by the end of 2007, the 15 fb with this integrated luminosity the twofor experiments could obtain a combined 5 On the other hand, itand will CMS. take Finally a the lot mainwill of questions indeed time are, be to for the ready understand LHC complex by if detectors 2006, the like and machine ATLAS for and the the experiments Tevatron if the discovery luminosity of 15 fb is similar ( in terms of assumed cross-sections,optimistic analysis approach methods, of detector performance. thewould increase Had Tevatron from the studies 5 more been adopted, the LHC discovery potential The most sensitive search channel at the Tevatron is close to 115 GeV, bothfor a machines, 5 the Tevatron and thefirst, LHC, some may comparison have enough ofthe luminosity the expected potential signal rate of isTevatron, these but a the two factor signal-to-background Colliders ratio of is 10-100 can aHiggs (depending be factor mass on of (e.g. made. the about 115 channel) five At smaller. GeV) larger the and than For the integrated LHC at same luminosity the (e.g. 10 fb requires mainly excellent b-tagging capabilities.unlike For at larger the masses Tevatron, Higgs thanks discovery to is the easier, very clean to achieve this goal. and should also be able toHowever, perform a precise detailed measurements of investigation somevarious of of branching the the ratios Higgs properties and Higgs [8]. couplings sector,of to the including the spin, the percent require level, measurements a of cleaner of the machine the Higgs such self-couplings as an and requires excellent electromagnetic calorimetry, and at the LHC, the sensitivity is provided by two complementary channels: 3. Physics beyond the Standard Model It is well known thatthe the door SM to Higgs New mechanism PhysicsModel [10]. entails is some Figure valid, problems 9 as and showsthese the therefore a predictions energy opens function scale [11], of Λ one up the to can Higgs which qualitatively mass. the Standard conclude Although that, there if are the big Higgs uncertainties mass in is close to will indeed be obtained by 2007, given that a three times more intense International Europhysics Conference on HEP experiment, which should becould collected deliver, by by the 2003. end of After 2004, the a 5 luminosity fb upgrade, the machine schedule foresees a first physicsallow run the between ATLAS August and CMS 2006 experiments and to February collect 2007, both which about should 10 fb or for a 95% C.L. exclusion up to masses of 120 GeV would require much more luminosity than 15 fb PrHEP hep2001

400 GeV is

light SUSY light heavy SUSY heavy ≤ Heinemeyer, Weiglein ’01 Fabiola Gianotti MSSM H m [GeV] t m mass versus top mass. SM W

LEP2/Tevatron (today)

= 113 GeV 113 = GeV 400 =

H H

The 68% C.L. experimental con-

M M experimental errors 68% CL: experimental errors 160 165 170 175 180 185 190

80.70 80.60 80.50 80.40 80.30 80.20

W

[GeV] M Figure 10: tour in the plane The SUSY prediction(lighter) is band, whose given sizethe by is allowed the range determined top of by the SUSY SM particle prediction masses; for given by the bottom (darker) band. –10– GeV, which means that New Physics should appear at this scale or below. Theoretical bounds on the Higgs 6 Extra-dimension theories predict the existence of additional spatial dimensions. In Technicolour predicts newtroweak strong symmetry. interactions The whichremoved. naturalness break problem The dynamically is hierarchy problembetween solved the the is because Technicolour elec- scale also the and solvedis a scalar because, more exponential. Higgs like fundamental New (higher) is in particles scale QCD, in are the the predicted theory relation at the TeV scale. Supersymmetry predicts newradiative particles corrections at stabilise the thesolved, Higgs TeV but mass. the scale hierarchy Therefore or problembig the is gap below, naturalness between a the which problem priori SUSY is scale not through No and solved new a because more interactions fundamental there are (higher) can scale introduced of still in the be addition theory. a to the SM gauge interactions. Three main solutions [10] have been proposed to solve, at least in part, the hierarchy • • • Figure 9: boson mass (inergy GeV) (Λ). as The a regionforbidden above because function the the of top Higgs curve self-coupling en- verges, di- is the region below theforbidden because bottom the curve electroweak is vacuumunstable. is On the otherModel hand, technically if works the upexperimentally Higgs to mass very the attractive, is Grand Unificationbetween in introduces the scale. the two electroweak scale additional range This and“hierarchy scenario, 130-180 problems: the problem”; which GeV, Planck and the is scale the then (17 not huge factboson, the orders that, difference of Standard which due magnitude), to is the radiativefine-tuning so-called the corrections, is the only needed mass scalar of toproblem”. the bring of Higgs it the down theory, to can the electroweak become scale, as theand heavy so-called the as “naturalness naturalness Λ, problems, which and are a related lot (but not of exactly identical) issues: the LEP limit,of then about the 10 Standard Model is expected to break down at an energy scale International Europhysics Conference on HEP PrHEP hep2001 , A β m )have 4 , and )havea 3 , ˜ ` 0 2 , 0 1 )andtan m A and ,χ m 2 , q Fabiola Gianotti ± 1 ). 0 1 g, χ χ ). At the tree level the Higgs sector µ ), which are the scalar partners of quarks ˜ ` is free. . mass (mainly from LEP and Tevatron) are in –11– ± µ W ), which are mixtures of the fermionic partners of the 4 , 3 , ) and sleptons ( 2 , q 0 1 h, H, A, H χ ), which is the fermionic partner of the gluon; two charginos g 1 for SUSY particles (sparticles). If R-parity is conserved, as it at the Grand Unification scale. There are also a common trilinear − 2 ) and a Higgsino mass parameter ( / 1 0 at the Grand Unification scale, and all gauginos (˜ A m 0 m some models, these additional dimensionsto allow the the gravity scale electroweak to scale,New be particles, lowered thereby down e.g. solving, excited at gravitons, should least appear in at part, the the TeV scale hierarchy or problem. below. ) and four neutralinos ( In order to reduce the number of parameters of the theory, a more constrained frame- In all the above cases NewIn Physics this paper, is only experimental predicted results from at searches for the SUSY TeV and Extra-dimensions scale, which strongly Many SUSY models exist, e.g. Supergravity, Gauge-Mediated SUSY-Breaking, Anomaly- In the Minimal Supersymmetric extension of the Standard Model (MSSM) the physical There is a quantum number in the theory, R-parity, which takes the values of +1 2 , ± 1 χ a common mass which is the ratioconstrained of models the than vacuum the expectation CMSSM, values like of mininal the SUGRA, two the Higgs parameters doublets. In more work is often usedcommon mass (constrained MSSM, CMSSM), where all sfermions (˜ electroweak and Higgs fields.to There five physical are Higgs two Higgs states: doublets in the theory, which give rise mass paramater ( is described by two parameters, the mass of one of the Higgs bosons (e.g. motivates machines like the LHC able to explore thisare energy presented. range. are not independent and only the sign of and leptons; the gluino (˜ The numerous motivationsdiscussed and here. indications It in istop however favour mass worth of mentioning (from that these Tevatron) the and theories present of measurements [10] [12] the will of not the be 4. Supersymmetry excellent agreement with the SUSY prediction, as shown inMediated figure SUSY-Breaking, 10. which differworld, in and the which wayonly predict SUSY results different breaking obtained in phenomenologies is the transmitted and framework of to experimental Supergravity our models signatures. arespectrum discussed. consists Here of: squarks (˜ ( for SM particles and is assumed here, SUSYric particles Particle are (LSP), produced toalso in which required pairs, all and to SUSYfore the be particles escapes Lightest neutral experimental eventually Supersymmet- and detection decay,Supersymmetry. leading weakly-interacting is In to stable. for most the cosmological models celebrated The the missing reasons, LSP LSP energy and is is signature the there- for lightest neutralino ( International Europhysics Conference on HEP PrHEP hep2001 , L ˜ t hZ - -jets A b m process hA 91.9 GeV at 100 GeV, and at the LHC < > mass range [14]. Fabiola Gianotti σ A mass is predicted A 5 h . m h β m ≥ mass, thereby leading to h has been almost fully ruled and tan R A ˜ t m Regions of the MSSM plane -jets and two taus. As shown in ” scenario [8]. b and boson is light. Indeed, irrespective max L h ˜ t where the various SUSY Higgs bosons − β h m through their decays into SM particles,“ in the Figure 12: can be discovered at tan –12– production in the Standard Model. The pairs) or with two b b ” scenario. For this case, the most recent LEP results . The other SUSY Higgs bosons are in most cases too HZ hA process is relevant mainly in the region max 100 GeV, and gives rise mainly to final states with four < − mass increases (through radiative corrections) with increasing hZ h production at LEP have excluded the region 115 GeV in this case. On the other hand, the SUSY parameters A h m m < 135 GeV, except in very general models with additional fields [13] hA 190 GeV. Hence, a light Higgs boson, as favoured by the electroweak h ” scenario [14]. The ex- ∼ m ≤ max h The region of the MSSM plane − m h excluded by LEP at the 95% C.L. m β -tan A Searches at LEP have already excluded a good part of the allowed At LEP, only two SUSY Higgs channels are accesible: the associated production in the ‘ Figure 11: m clusion obtained by theRun CDF 1 experiment is in also shown [15]. ), the scenario where there is no mixing between R ˜ t gives rise to similar final states as out by LEP since (when both Higgs bosons decay to are presented in figure 11 as a function of the parameters can be chosen in such a way as to maximise the value of the the more conservative “ data [12], is natural in Supersymmetry. More precisely, since the mixing between the SUSY partners of the left-handed and right-handed top quarks ( heavy to be produced. The and the associated production of the model, i.e. irrespective of the SUSY-breaking mechanism, the where (still) International Europhysics Conference on HEP 4.1 Searches for the MSSMA Higgs distinctive bosons feature of Supersymmetry is thatto the be smaller than figure 11, searches for is relevant in the region PrHEP hep2001 β → ˜ ` searches exchange. , and could hZ β . Namely, the γ/Z β ,justabovethe , which is medi- Fabiola Gianotti β ˜ g ˜ q ˜ ” scenario and for the g, ˜ g ) up to masses of about -jets, to which only the b b -tagging is required. The b ˜ =179 GeV (corresponding q, max level should be granted at Ab q per experiment). Figure 12 -channel with − top σ s 5 1 h m and − m ≥ mass obtained from b h and moderate tan Hb , A b m hb pair ( b –13– b mass increases with increasing tan h , the limit on the A m 114.1 GeV. The latter can be translated into a lower limit on can be discovered at the LHC unless the heavier Higgs bosons 1.9 in the more conservative case > h h m 2.4 is excluded at 95% C.L. in the “ pairs, the expected final states contain four β< b . Therefore the main topology arising from the pair production of b 0 1 tan β< qχ 2 TeV). < ≥ tan → s < ˜ q √ , from the central measured value). The experimental exclusion of the low tan 0 1 σ sparticles should be quite simple: two acoplanar objects (e.g. leptons, jets) plus At the Tevatron, on the other hand, the production of ˜ At LEP, all kinematicallypair-produced accessible more or sparticles less (except democratically through gluinos) the are expected to be At the LEP energies, direct decays to the LSP are expected to dominate, e.g. ated by strong interactions,processes. is expected to dominate by far over other (electroweak) `χ , as shown in the figure, since the Discovery of at least one SUSY Higgs boson at the As shown in figure 11, the CDF results from Run 1 [15] are complementary to the • • β CDF experiment was sensitive inregion Run between 1, because the a CDFnot very enough and efficient centre-of-mass the energy LEP andRun CDF contours 2 not is enough the luminosity. not Tevatron On experimentsleast excluded the at should today other 95% be hand, because C.L. in able [7]. LEP to has explore the full MSSM Higgs plane at the LHC, even with a small amount of luminosity (10 fb region of the MSSM parameter space is anLEP important exclusion. legacy Indeed, from Tevatron LEP. hasMSSM enough Higgs centre-of-mass boson energy in to association produce with any a neutral to +1 shows that over aat good the LHC. part The of exception the is parameter the space region several at Higgs large bosons are accessible central value of thereduces measured to top 0.6 mass (174.3 GeV). In the same scenario, this exclusion have observable decays intomay therefore SUSY miss particles the (e.g.independent heavy observation of part this charginos part of of orCollider the the ( spectrum neutralinos). MSSM may Higgs require a The spectrum. very high-energy LHC Lepton Complete and model- LEP limit, where only is, as in the SM case, tan 4.2 Searches for SUSY particles The expected SUSY phenomenology andstrategies the physics and environment, and the thereforeLepton physics the Colliders) search potential, and at are the quite Tevatron (or, different more at generally, at LEP Hadron (or, Colliders): more generally, at International Europhysics Conference on HEP 95% C.L.. In the region at large 300 GeV. These processes havetherefore rates been which are observed strongly withdecay enhanced the mainly at data large into sample tan collected in Run 1. Since the Higgs bosons region 0.5 PrHEP hep2001 interac- γγ Fabiola Gianotti between the produced values), and therefore production, m m GeV) energy depositions in ZZ ∼ region is not accessible, because and m WW production). A 20% excess of acoplanar `ν`ν 10 GeV) is needed to trigger the experiments → –14– >> WW . These cascade decays give rise to very crowded final states 0 1 jets and leptons, plus large missing transverse energy. 208 GeV have found no significant deviations from the SM expec- qqZχ T ' p → s 0 2 +jets, etc.). Furthermore, the low ∆ √ qqχ 300 GeV in Run 1), but the kinematically accessible parameter space can not W/Z → ∼ ˜ q q → ˜ with many high- At LEP, Standard Model backgrounds (e.g. tions) are notalmost a all big kinematically concern. accessiblefully hadronic sparticles, As final to a states), almost consequence,the and detector, all even the such decay to as experiments modes very thosesparticle modest are expected (including and if ( sensitive the the to mass LSPmainly difference is sensitive ∆ to small. squarks and Theto gluinos, Tevatron which spectacular experiments, have signatures a on large usedduction, cross-section the to and other give reject hand, rise the are huge backgrounds (QCD multijet pro- missing energy produced byother the hand, squarks escaping and neutralinos. gluinos,imental which must At limits be Hadron (see quite Colliders, heavy below), giveng on the are present the expected exper- to decay through multi-step cascades, e.g. absolute mass limits can not be established. a large amount of visible energy ( be fully covered (e.g. there is no sensitivity to the small ∆ As a consequenceby of the the available above centre-of-massenvironment. points, In energy addition, at by and combining LEP severalall luminosity searches it the corners rather is of mass possible than to the reachabsolute cover by almost kinematically mass is the accessible limits limited physics (i.e. parametermodels. mainly valid space, Tevatron, for on and any the therefore choice other(up to hand, of to has the derive a parameters) huge within mass reach constrained for squarks and gluinos and reject the backgrounds. A few examples which illustrate the above points are discussed below. More details • • events observed in the ’98 and ’99 data [16] has not been confirmed by the year 2000 tation (the dominant background is International Europhysics Conference on HEP can be found in references [16, 17, 18]. 4.2.1 Sleptons Despite the simplecompanied topology by expected missing in energy,because slepton the of pair final the production small state, is signal-to-backgroundcome not i.e. ratio. mainly observable Therefore from at two the LEP. theexperiments present acoplanar Searches up experimental Tevatron to for leptons limits acoplanar ac- leptons in the data collected by the four ττ data. The derived massabout limits, 100 shown GeV in for figure selectronsof 13, (which these range benefit limits from from will about a remain 80 larger valid GeV production until for cross-section). the staus Some LHC to era. PrHEP hep2001 ) 2 ∼ χ M LEP < Fabiola Gianotti q ∼ M

mass. However, unlike

g ∼ gluino mass (GeV/c

q

q = M =

∼ CDF M D0

Regions of the plane squark

UA2 UA1 & LEP 1 0 200 400 600 0

400 300 200 100 ) (GeV/c mass squark 2 Figure 14: mass versus95% C.L. by gluino CDF [19], D0The [20] hatched and mass region LEP [16]. at thener excluded bottom is right theoretically cor- forbidden. at masses, shown in figure 14, come from a recent g –15– values occur for large values of the gluino mass m R and ˜ l ˜ M q ADLO Preliminary CL % =1.5) β , tan 2 300 GeV, is obtained if squarks and gluinos are mass-degenerate. The lower χ Regions of the plane LSP mass Observed Expected M < R

∼ l ˜ =-200 GeV/c µ 50 60 70 80 90 100 Excluded at 95 M ( Selectrons Smuons Staus s = 183-208 GeV s = 183-208 √ 0

80 60 40 20

χ

) (GeV/c 100 M 2 The most stringent limits on the ˜ Figure 13: versus slepton massby excluded LEP at [16]. 95%perimental limits C.L. on The (fromstau left full mass, to the lines right) smuon the mass give andmass. the the selectron The ex- dashedsponding lines expected limits. indicate The the shadedis region corre- theoretically forbidden. the Tevatron experiments, theythe are LSP sensitive below to 25 mass GeV differences (such between small the ∆ squark and limit on the gluino massthat valid the for LEP any experiments value of have a the squark much more mass limited is reach 195 on GeV. the Figure14 shows ˜ CDF search for events withreach, multijet up plus to missing transverse energy [19]. The highest mass and small values of thethe squark two machines. mass). This is a nice example4.2.3 of Charginos complementarity between LEP has the largest and most model-independent sensitivity to the production of these 4.2.2 Squarks and gluinos In contrast to theand slepton gluinos. case, The Tevatron signatureof has large expected the missing from transverse largest the energycoming discovery pair (from from production potential the the escaping more-or-less of for long LSP) these cascade squarks in plus decays. sparticles several these jets One consists searches of and/or is the leptons towhich main can experimental understand receive difficulties the large missing contributionsin transverse from instrumental energy QCD effects multijet distribution such events. in as the badly-measured data, jets International Europhysics Conference on HEP PrHEP hep2001 ,is 0 1 .As region β `νχ m → region. At ˜ ν 20 and small exchange. β ` 85.9 GeV ≥ Fabiola Gianotti L3 preliminary → β γ/Z is small, sneutrinos ± (GeV) 1 + pairs, and charginos ~ χ 0 χ M value (85.9 GeV in the ˜ ν m ` or m 0 1 χ searches become ineffective The 95% C.L. lower limit on ∗ standard ISR stable −

W

χ between the chargino and the LSP LEP I LEP + -channel with m → χ s 40 60 80 100 -1 -2 1 ±

10 10

χ m (GeV) (GeV) m ∆ Figure 15: the chargino mass obtainedperiment by [21], the as L3ence a ∆ ex- function ofmasses, in the the differ- most difficult low-∆ (see text). –16– , followed by pairs is not observable, an indirect limit is obtained − 0 1 χ χ + χ 5 GeV the stan- → − − e 4 + e m> 6 GeV at 95% C.L., is found asymptotically for tan . , charginos decay into very soft 45 m -channel with sneutrino exchange and the > t bounds from chargino and slepton searches also contribute. The absolute ) 0 1 β values sleptons should be accessible at LEP, and the negative results from slepton χ ( 0 100 MeV, charginos are stable, and there- m m between the chargino and the LSP is small The second case is when the mass difference Since the direct production of , in the region (named “corridor”) where charginos decay into 0 m m< expected to give riselepton plus to missing final energy, states orexperiments acoplanar containing have leptons. jets been By plus looking ablea missing for bound to these energy, which rule topologies, or is out theproduction. jets only LEP charginos plus a with This one few masses bound,deteriorated hundreds by smaller MeV which a below than few is the GeV 103.6 valid in kinematic GeV, over two limit cases. a for If large chargino the pair common region scalar of mass the parameter space, is are light, and the charginobetween production the cross-section is reduced by the negative interference because the two leptons in thesmall final state are too soft to be efficiently detected. However, for limit, larger tan from the interplaysearches. of This the is possible exclusion because withinhere, domains constrained models, the such in as various the the CMSSMshows sparticle discussed parameter the masses space lower are provided limit related. by on other the The neutralino result mass is as given a in function figure of 16, the which parameter tan previously mentioned, SUSY Higgs searches at LEP rule out the low tan m and sneutrinos are almost mass-degenerate. In this case ∆ (figure 15).dard For searches ∆ mentioned above∆ are used.fore can For be discovered or excludedanomalous by looking ionisation for (asstable expected charged from particles) heavy intors the of tracking the detec- ate LEP values of experiments. ∆ For intermedi- hadrons, and a dedicated searchoped has which been requires devel- a hard(ISR) initial-sate photon, radiation to triggerject the the experiment background, accompanied and by a re- smallshows amount that of the additional lower limit visible on energy. the Figure chargino 15 mass obtained for any ∆ International Europhysics Conference on HEP sparticles. The process case of the L3that experiment) LEP is is only able 20 to GeV address below the the most4.2.4 difficult kinematic Limit topologies. limit, on thus the demonstrating LSPA mass very important legacytralino, from which LEP has is important cosmological thetoday implications the absolute because best limit this candidate on sparticle for the is the mass considered universe of cold the dark lightest matter. neu- PrHEP hep2001 4 10 3 ) 2 10 Fabiola Gianotti DAMA NaI CDMS Edelweiss 2 10 plane. 2 WIMP Mass (GeV/c 10 / 1 Region of the plane WIMP mass level by the Dama experiment m - σ 0 1 -3 -4 -5 -6 -7 m

10 10 10 10 10 WIMP-Nucleon Cross-Section (pb) Cross-Section WIMP-Nucleon Figure 17: versus WIMP-nucleon cross-section favoured at the 3 (closed contour, [23]). Theat regions 90% excluded C.L.(solide by line, the Edelweiss(dashed line, [24]), experiment [25]), and the asult previous CDMS DAMA (dash-dotted re- experiment line, [26]) are also shown. –17– decays can proceed through SUSY loops involving β ) tan sγ 0 2 → 2 } b (large m 10 1 TeV/c in the corridor ≤ Higgs Sleptons = 175 GeV/c

0 top Charginos = 175 GeV. More details on the method used to derive the LSP 5 m m { top C.L. m Higgs % 2 95% C.L. lower limit on the mass regions are indicated. β Excluded at 95 LEP preliminary 1 , as obtained in the constrained MSSM

40 45 50 55

β

χ (GeV/c m ) If SUSY particles are light, The LEP bound on the LSP mass can be compared to the results of direct searches for 2 Figure 16: of the lightesttan neutralino, as a function of by combining the four LEP experimentsThe [16]. searches used to setious the tan limit in the var- for instance squarks and charginos. The measurements [28] of the branching ratio for this limit, as well as a discussion of the impact of mixing in the stau sector, can be found in [22]. cold dark matter. These areor, performed by more underground experiments generally, looking for forgalactic neutralinos Weakly-Interacting halo Massive and Particles interacting (WIMP’s), withexperiments, the coming the detectors DAMA from experiment via the atthe WIMP-nuclei Gran scattering. rate Sasso, of One has nuclear of reportedThe these recoils an region [23], annual favoured modulation which by in could theexperiments DAMA be of observation, interpreted similar as as wellquoted scope, due as above, is to the galactic which negative shown results neutralinos. doesabout in from half not figure other of depend 17. the on region It the preferred can by4.2.5 neutralino-nucleon the be Indirect cross-section, DAMA seen constraints data. rules that out theMore model-dependent LEP limit constraints onarguments other Supersymmetry than can direct beminimal searches SUGRA obtained at [27] from Colliders. are results shown Examples in and derived figure in 18 the in framework the of International Europhysics Conference on HEP searches provide exclusion ofon part the LSP of mass. theseabout In regions the 60 and more GeV constrained hence for minimal the SUGRA above-mentioned model, limit this limit improves to PrHEP hep2001 has 4 is the (re- − 3 h 10 M · 5) = 190 GeV, . = 550 GeV, 2 0 0 / 1 Fabiola Gianotti A ± 3, where . m 2 0 . ≤ = 30, is the neutralino density 2 β (which are related to the h )=(3 2 χ χ M sγ Ω , 1 Evolution of the gaugino mass ≤ → M b 1 ( . comes from SUSY contributions, e.g. BR 2 0. = 200 GeV, tan 0 Figure 19: parameters neutralino and chargino masses) and m µ< lated to the gluino mass)values from at the the measured electroweakimental scale (with accuracies exper- reflectedof by the the bands) widths scale up [32]. to The the chosenSUGRA Grand parameter point space Unification is in the minimal - –18– 0 2 by the BNL E821 experiment [29], assuming that m 0 10001000

− > -boson

µ 0000 h µ =0 [27]. 99 g

, 0

,andthe 0 A 0000 88 sγ = 1 β

0000 ) 77 → tan (the dashed lines . 0and b 0000 GeV σ 66 σ (

6 . /2 1 0000 55 m µ> to 1 GeV = 113 GeV = 113 0000 .5 44 h σ contour). 3 6 0 m deviation from the SM prediction . σ 0000 = 1 33 =10,

σ 1 ± χ β ± The minimal SUGRA plane m 0000 22 100100 00

0000 0000 0000 0000 0000 0000 0000

88 77 66 55 44 33 22 100100 for tan

0 2 measurement at 2 ) GeV ( m 2 / − 1 Finally, the region preferred by cosmology (cold dark matter) has been derived assum- Also shown in figure 18 is the region preferred by the recent measurement of the anoma- µ It should be noted that very recently, after the 2001 Summer Conferences, the theoretical calculations 2 indicate the light-shaded (light green) regionby is cosmology. favoured The shaded (pink)ited region lim- by solid blackg lines is favoured by the Figure 18: m searches at LEPthe and limit the from dot-dashed sleptondark-shaded curve searches at (brown) LEP. region The forbidden, is the theoretically medium-shaded (darkregion green) is disfavoured by The vertical dashedfrom chargino line searches at showsdot-dashed LEP, the line the vertical an limit old limit from been used to derivedisfavour the regions limit of the in parameter figure space 18), characterised in by good small sparticle agreement masses. with the SM expectation, have been revisited [30]. Ashas a decreased consequence, from the 2 deviation of the BNL measurement from the SM expectation present Hubble expansion rate (in units 100 km/s/Mpc) and Ω normalised to the critical density of the universe. loops involving charginos and sneutrinos. ing that the neutralino relic density be in the range 0 the reported 2.6 lous magnetic moment of the muon International Europhysics Conference on HEP decay from CLEO and BELLE (a combined value PrHEP hep2001 n Fabiola Gianotti 1 TeV, i.e. of the same order as the ∼ 800 GeV, and are therefore accessible at future –19– ∼ . As shown in figure 19, this should be possible by 2 scale Extra-dimensions, Randall-Sundrum models) will / 1 ) can be as low as 1 S − m M additional spatial dimensions, and gravity is allowed to propagate in 4 + n dimensions has to be equal to the standard 4-dimensional law at the (large) distances The basic idea of ADD theories (see [10] for a more rigorous discussion) is that, if A first constraint to this scenario comes from the requirement that Newton’s law in Figure 18 should not be considered as a collection of stringent limits, since it is based The LHC discovery potential extends up to squark and gluino masses of 2.5-3 TeV. On the other hand, if SUSY will be found at the Tevatron or at the LHC, then a Linear n starting from theevolving values them of up the toEquations the gaugino [32]. Grand masses Unification measured scale by at means the of the electroweak Renormalisation scale Group and dimensions whereas the Standard Modelthe world gravity is scale confined (here in called a 4-dimensional “wall”, then not be discussed here. there exist that are experimentally tested. This implies that the following relation must be satisfied electroweak scale, thereby solving the hierarchy problem. 4+ on many specific assumptions.searches, However, precise it measurements illustrates ofinteresting nicely to propagator the notice physics that interplay there and betweeners, is cosmology. direct which a region, is For not favoured instance, excludedIn by by it all this present is the search region, results above-mentioned squarks atmachines. indirect are Collid- measurements lighter and than predictions. 4.2.6 The future The ultimate mass reachcharginos of and the for CDF and stopfor D0 squarks, gluinos experiments about [31]. in 250 Run GeV 2 for is sbottom about squarks 200Therefore, GeV and if for up nothing to willof 450 be its GeV found motivation, at for themuch instance fine-tuning. LHC the low-energy possibility Supersymmetry of will stabilising lose the most HiggsCollider boson of mass sufficient without centre-of-mass energyof should be almost able to all performmasses kinematically precise should measurements accessible be sparticles. measuredthe to gluino In 0.1% mass at [9]. particular, thethe LHC chargino These structure with results, and of an combined the accuracy neutralino with theory atof the at a percent the high measurement level, energy, of common should allowing for provide gaugino insight instance of mass an accurate reconstruction 5. Extra-dimensions These theories have raisedtheoretical a papers large published on interest thehave over subject. been the Since derived last most in of three[33]), the the years, existing other framework with experimental scenarios of results more (e.g. ADD than models TeV 700 (Arkani-Hamed, Dimopoulos, Dvali, International Europhysics Conference on HEP PrHEP hep2001 n =2 (5.2) (5.1) n of the 1TeV, R of extra- ∼ n = 2 becomes n Fabiola Gianotti and equation 5.1, /R 1 ∼ ,thenumber is the number of gravitons S 31 TeV (2.7 TeV) for increases, the size cm from the above formula, n +2 δm M n kk = 3), these gravitons give rise 1 TeV, then only one extra- > n s S 13 N n √ S ≈ M 10 M S kk ≈ ≈ N n M n R R 2 Pl R 1 n M s +2 n S vertex, and √ ≈ M ) 2 Pl 1 G –20– ≈ M , e.g. 400 eV for ffG 2 → . Using the relation Pl ≈ . Assuming /R n 1 ) ) M R ff , the new gravity scale G ( ∼ is required to be of the order of 1 TeV. Pl σ → S s/δm M δm M √ ff ( ( acquire, by virtue of the Heisenberg principle, a quantised mass σ ∼ R kk N is an integer number. And since the spacing between adjacent energy k is the coupling at the 1 mm. This shows that the gravity scale could be as low as Pl ≈ /M ,where 1 TeV in the above formula). This scenario is very attractive because it implies k/R ∼ That is, due to the large number of available Kaluza-Klein gravitons, the effective between the Planck scale An important consequence of these theories is that gravitons propagating in compact Astrophysical bounds [33] can be derived for instance from the cooling of the Supernova Present constraints on Extra-dimension theories come from astrophysics and cosmol- where 1 The graviton production cross-section, for instance for two incoming fermions, can ∼ S =3). Although there are in general large uncertainties on these astrophysical bounds, = 2 is clearly disfavoured if k M n coupling between SM particles( and gravitons becomes of detectable electroweak strength dimensions and their physical size which can be produced inand the is interaction. therefore The proportional latterKaluza-Klein to depends the levels: on centre-of-mass the energy available divided phase by space the spacing between which is ruled out by macroscopic observations. But when m extra-dimensions must decrease accordingsmaller to than equation the 5.1, sensitivity and oflaw present already gravity down for experiments, to which arewithout able to contradicting test the Newton’s existingextra-dimensions compactified experimental at constraints, the sub-mm provided level. that there exist extra-dimensions of size n ( dimension is excluded, because its size should be one obtains: ogy, table-top gravity experiments and Colliders. SN1987A, which is due to neutrinoexperiments emission, in as measured agreement by with the the IMBvia and predictions. graviton Superkamiokande This emission, sets which constraints translates on into additional the cooling limits there is onlypossible one to scale test in quantum gravity particle and the physics, geometry the of the electroweak universe scale, in our and laboratories. that it should be levels is predicted to be small ( International Europhysics Conference on HEP to a continuous tower of massive states called “Kaluza-Kleintherefore excitations”. be written as PrHEP hep2001 , 1 − =6. n , i.e. much 4 − Fabiola Gianotti 6TeVfor . 0 ∼ =2to n = 2 has been set. n m. No deviations have been observed of integrated luminosity, and TESLA µ 1 2 this factor is of order 10 − 1TeVfor ≥ 200 ∼ n ∼ –21– 1.9 TeV for .For > +2 n S ) with only 2 fb S . The LHC has a sensitivity of up to 9 TeV for 100 fb M S 1 − /M M Z m = 3. For the same number of extra-dimensions, the Tevatron Run 2 n . The expected signature is a single photon plus missing energy, since γG have been set which range from → S ∗ M γ → On the other hand, direct searches for graviton production at high-energy Colliders Smaller distances can only be explored by high-energy Colliders. It should be noted, The most stringent constraints from gravity tests at short distances come from the The approximate potential of future Colliders for the investigation of ADD Extra- − e + thanks to the strong enhancement ofat graviton the effects at LHC, high also energy. theseappeal, If theories, nothing although like will it Supersymmetry, be is will found loseof possible most extra-dimensions. to of evade their the motivation experimental and limits by increasing the number smaller than e.g. the typical contributions expected fromare SUSY powerful loops. because, ascentre-of-mass shown in energy. equation 5.2, Only themachine, results cross-section gravitons from increases LEP can withe increasing are be available produced for in the association time being. with a At photon this through the process can achieve 5-6 TeV with 500 fb however, that no constraintstroweak are observables provided at LEP, by because precision theare measurements contribution suppressed of for by graviton instance loops a of to factor these elec- ( observables gravitons escape detection. Forthe this event type missing of mass final asshow state, obtained up figure at by large 20 DELPHI. values shows Ano of the signal the excess distribution from missing has graviton of mass been production sincelimits gravitons found, would on are neither expected by to DELPHI be nor heavy. by Since the other LEP experiments, lower Seattle experiment [34], which has recentlyand measured a the rotating force attractor between down a to torsion distances pendulum of from Newton’s law, and the limit 6. Flavour-changing neutral current processes One of the challenges oflow any observed theory beyond rate the of Standardtree Model FCNC level. is processes, At to the account thatsince for same in there the time very the the these SM processes Standardthe background are Model is amplitude an small. are obvious of place The forbidden FCNCtherefore to top processes at deviations look sector is the from for is the related New particularly Standardthe to Physics, interesting Model top the because could quark. mass be first differences observed between in quarks, channels involving and International Europhysics Conference on HEP hasareachofabout2TeVon Similar bounds have beenlooking set for at deviations LEP, from Tevatron theangular and SM HERA distributions expectation by of in indirect thevirtual various measured searches, gravitons cross-sections final i.e. between and the states. particle by incoming and Deviations the outgoing could particles. bedimension a theories is sign summarised of inis figure exchange about 21. of 1 The TeV present for lower limit on the gravity scale PrHEP hep2001 . γ k tqZ final t t ), large 0.2 and and µ < or Z tqγ k e vertex, through Fabiola Gianotti tuγ in the SM) in lepton ( T 10 p -quark of a few percent. − c = 3) at present and future n In the framework of ADD mod- respectively. CDF has looked for the -quark and , and therefore can only constrain from indirect searches and from direct t u Z ± k S e Figure 21: els, the 95% C.L.M reach on the gravity scale Colliders. searches (for → and u γ –22– ± k hadronic system, a topology expected for instance e T p (branching ratio smaller than 10 production), the ν γν Zq, γq =2. -exchange process n → γ t (an example is shown in figure 22). The amplitudes at the The distribution of the missing ”excessinH1 Z W production [12], as well as from single-top production. plane (figure 23). The presently unexcluded region (approximately Z =0.75 TeV and W k 0.3) corresponds to top branching ratios into S For these reasons all three machines, LEP, Tevatron and HERA, have looked for the - < mass in events with photonsergy plus missing from en- DELPHI [35].ror bars The dots are withgion the er- shows data, the the expectationnant light-shaded from SM re- background the ( domi- Figure 20: dark-shaded region theother backgrounds, and contribution the solid from pected line the signal ex- fromM graviton production for γ γ states. The LEP experimentscharm have or looked a for upproduction single-top quark but, production (figure unlike the 22). in LEP associationthe The experiments, with they neutral-current HERA can a experiments only have probe also the looked for single-top The negative results ofk these searches have been translated into exclusion regions in the k missing transverse energy and a high- FCNC top decays from FCNC vertices where aphoton top or quark a transformsvertices into are a governed charm by or the a parameters up quark by emitting a The HERA limit onH1 single-top has production also performed shownbecause a in similar H1 figure search, observes 23 but an is the that excess resulting obtained bound of is by events less ZEUS. [38] stringent. containing This a is high- 7. The “ International Europhysics Conference on HEP PrHEP hep2001 H1 2 T (GeV) W 10 p (GeV) T µν M M WWZ 10 γ κ plane ex- , as a func- and b) X T Z p k

p data 94-00

0

+

80 T 60 40 20 -

(GeV) (GeV) P

e P -1 X Fabiola Gianotti excluded by CDF excluded by LEP γ k WWγ 2 (GeV) 10 (GeV) ν e T M M The distribution of the DATA 10 LEP Preliminary 2 2 =500*L a) MC Regions of the H1 PRELIMINARY 101.6pb L

0

80 T 60 40 20

(GeV) (GeV) P

of the measured value is also in- P =179 GeV/c =169 GeV/c t t X m m Figure 24: of the hadronic system tion of the transverse mass ofmissing the lepton- energy system, forsample”. the H1 The “ whereas crosses the show dotstation the show for data, the an SM integratedtimes luminosity expec- larger 500 than that of the data [38]. 00000 0.2 0.2 0.2 0.2 0.2 0.4 0.4 0.4 0.4 0.4 0.6 0.6 0.6 0.6 0.6 0.8 0.8 0.8 0.8 0.8 1 1 1 1 1 σ

11111 00000

1 Z 0.80.80.80.80.8 0.60.60.60.60.6 0.40.40.40.40.4 0.20.20.20.20.2 κ . PrHEP hep2001 ± 1 − Figure 23: cluded at 95%top C.L. couplings. by searchescluded for The by FCNC hatched CDF [36]by region LEP and is (the the ex- effectby shaded of region varying thedicated) top mass [37].bound The from vertical ZEUS [38]. line shows the ,the X T p of data, production diagrams involve –23– 1 − ver- e e W

· production. On 25 GeV (40 GeV), tqγ/tqZ W ;Z ­; > ¼ final states. Anomalous X T p 28) expected from SM pro- . Ø bjj 0 ± → t 99 Ï . c b ´ Ù , is unlikely, because the excess in ;Ð Õ;  Õ; Feynman diagram for single-top µ 73 (0 . b`ν Ð 0 0.5 expected) and no excess is observed in ± tails of the distribution in figure 24, besides ± → 82 X T . t p The origin of the spectacular H1 events in the Figure 24 shows that, for high values of of the hadronic system, more events are observed Figure 22: production at LEP. The FCNC tex is shown as a blob (courtesy of A. Leins). T It should be notedtheir that estimates both for the experiments Standard agree Model on expectation. high- the other hand, no excessin has these been final found states by in ZEUS a data sample of 130 pb cesses. The dominant SM80% contribution of (more the than total) comes from with 2 ten (six) events are observed in 102 pb a statistical fluctuation, isgation. presently under Single-top investi- production,a which gives similar rise signature to cally if the top decays semileptoni- Triple Gauge Couplings (some of the this channel is notwith significant 1.8 (five events observed the fully-hadronic in the data than theyModel. are predicted by For the instance, Standard for p International Europhysics Conference on HEP PrHEP hep2001 120 GeV or to 1TeVinsome ∼ Fabiola Gianotti ∼ ). Second, in general 0 Z 100 GeV, if pair-produced will be collected, CDF and 1 ∼ − 15 fb 300 GeV from direct searches, and ∼ ∼ 185 GeV, thereby covering most of the range ∼ –24– 196 GeV at 95% C.L., [12]), suggest that the Higgs < 500 GeV) can technically still be consistent with the 200 GeV if singly-produced. Third, by combining and H ∼ ∼ m H m boson). If an integrated luminosity of hint and a few beautiful candidates at a mass of about 115 GeV, as well as 0 σ Z The Tevatron Run 2 will pursue, with increased sensitivity, the exploration of the few The upgraded HERA has a mass reach of up to At the end of the decade, the LHC will explore in depth the highly-motivated energy direct searches have excluded newlike particles SUSY with masses particles, up and to interpreting up the to results ofput several searches very (e.g. stringent Higgs constraintsa and in lower SUSY), the limit it of parameter hasthe about space been outcomes 45 possible of of GeV to minimal tenPhysics. on models, years the of and LSP experimentation to mass at derive within LEP the represent CMSSM. ahundred For real GeV these region challenge reasons, started forcases in New (e.g. Run a 1, with a discovery reach of up to D0 will have goodexclude chances to it discover (at a 95% SMpreferred C.L.) Higgs by up boson the to electroweak up data. to masses masses of of is complementary to Tevatron into some R-parity respects, violating e.g. SUSY.be There in understood. is the an sensitivity to intriguing leptoquarks excess and in therange H1 of data up which needs toSM to a Higgs few boson (if TeV, not andpredictions. yet therefore discovered will at say that time), the Supersymmetry, final and word other about TeV-scale the existence of a could be just arounda the heavy corner. Higgs boson It (e.g. should be noted that, although theories predicting electroweak data [39], thisdata requires from an the “ad Higgs sector hoc” and compensation from between other new the particles impact (e.g. on a the new Acknowledgments The results presented in thisimpossible paper are to based thank on them the all.and work the of I LEP many am people, SUSY particularly and Working grateful Group, it to would and be the to LEP their Higgs convenors P. Working Igo-Kemenes Group and L. Pape. The exceptional LEP era,main results which in has the recentlyHowever, domain a come of 2 searches. to a First,the the conclusion, fit Higgs to has the boson produced electroweak is data heavier three ( than 114.1 GeV. 8. Conclusions International Europhysics Conference on HEP vertices) are excluded byOther interpretations LEP, in which terms has ofparticles New a or Physics, excited much e.g. quarks, larger R-parity arethe violating sensitivity being upgraded production evaluated. to machine of The these starting SUSY new in couplings. data which fall will 2001 be should collected shed with light on this question. PrHEP hep2001 , Fabiola Gianotti Report of the Higgs Working Group (2001) 387. B 609 (2001) 23. (2000) 1. (2001) 67; (2001) 38. –25– (2001) 4472. (2000) 5699. (1995) 618. (2000) 23. (1996) 757. 86 (2001) 319. B 499 84 75 B 495 B 499 Nucl. Phys. B 499 B 480 B 389 B 517 (1998) 352. , [hep-ph/0010338]. Phys. Lett. Phys. Lett. Phys. Lett. Detector and physics performance Technical Design Report B 444 Phys. Lett. Phys. Rev. Lett. Phys. Lett. Phys. Lett. Phys. Rev. Lett. Phys. Rev. Lett. Phys. Lett. Phys. Lett. http://lephiggs.web.cern.ch/LEPHIGGS/talks/index.html. P. Azzurri, these Proceedings. for Run 2 of the Tevatron CERN/LHCC/99-15. [2] LEP Higgs working group, CERN-EP/2001-005,[3] [hep-ex/0107029]. ALEPH Collaboration, [4] DELPHI Collaboration, [1] P. Igo-Kemenes, LEPC Open Session, 3 November 2000, [5] L3 Collaboration, [6] OPAL Collaboration, [8] ATLAS Collaboration, [7] M. Carena, J.S. Conway, H.E. Haber, J.D. Hobbs, et al., [9] R. Heuer et al., TESLA Technical Design Report, [hep-ph/0106351]. References International Europhysics Conference on HEP I would also like toM. thank Kuze, F. E. Cerutti, Perez, B. M. Clerbaux, Spiropulu M. and Felcini, P. S. Janot, Wynhoff. T. Junk, M. Kado, [21] L3 Collaboration, L3 note 2644,[22] March 2001. ALEPH Collaboration, [23] R. Bernabei et al., [26] R. Bernabei et al., [16] LEP SUSY working group, http://lepsusy.web.cern.ch/lepsusy/. [17] CDF Exotics Physics group, http://www-cdf.fnal.gov/physics/exotic/exotic.html. [18] D0 Physics group on Searches[19] for New CDF Phenomena, Collaboration, http://www-d0.fnal.gov. FERMILAB-PUB-01/084-E, submitted to[20] Phys. Rev. D0 Lett.. Collaboration, [24] A. Benoit et al., [astro-ph/0106094]. [25] R. Abusaidi et al., [27] M. Battaglia et al., CERN-TH/2001-150, [hep-ph/0106204]. [10] P. Binetruy, these Proceedings. [11] G. Isidori, G. Ridolfi, A. Strumia, [12] D. Charlton, these Proceedings. [13] M. Masip, [14] LEP Higgs working group, LHWG[15] Note/2001-04, [hep-ex/0107030]. CDF Collaboration, PrHEP hep2001 Fabiola Gianotti (1998) 263. B 429 (2001) 017703. D63 Phys. Lett. (2001) 093003. (2001) 1418. –26– (1998) 2525. Phys. Rev. (2001) 2227. 86 80 86 D64 Report of the SUGRA Working Group for Run 2 of the Phys. Rev. Phys. Rev. Lett. Phys. Rev. Lett. Phys. Rev. Lett. , [hep-ph/0003154]. ee, these Proceedings. Tevatron BELLE Collaboration, BELLE-CONF-0003. [37] M. Pimenta, these Proceedings. [38] C. Vall´ [39] M. Peskin and J. Wells, [35] DELPHI Collaboration, A. Anashkin et[36] al., DELPHI CDF 2001-011 Collaboration, CONF 452. [33] N. Arkani-Hamed, S. Dimopoulos and C. Dvali, [32] G.A. Blair, W. Porod and P.M. Zerwas, [30] M. Hayakawa and T. Kinoshita, KEK-TH-793,[31] [hep-ph/0112102]. V. Barger, C.E.M. Wagner, et al., [34] E. Adelberger et al., International Europhysics Conference on HEP [28] S. Ahmed et al., CLEO CONF 99-10; [29] H. N. Brown et al.,