arXiv:hep-ex/0110086v1 31 Oct 2001 acltos a ea es shr oetmt eibyas reliably estimate to hard as least at be ex can co and usually calculations, uncertainties, theoretical theoretical that The is comparable. year measurements are the many in to developments common new status theme on current se placed The electroweak emphasis experiments. with the of report, of range tests wide experimental a encompasses precise of field The Introduction 1. prtn ic 97 aymaueet aebe aei th in made been have measurements 2 collider Many range electron-positron 1997. BEPC since the operating at detector BES-II The and R 2. details. for consulted be should References space. of the for test prospects global Finally, a from into summarised. results is results these fit recent of comprehensive many with of synthesis together The reviewed, SLD. Results are sample calculations. Model data Standard Bro recent at moment with magnetic compared anomalous the of measurement new ai Charlton David Model Standard the of Tests Experimental E-mail: UK 2TT, B15 BIRMINGHAM Birmingham of University Astronomy The & of School Fellow Research University Society Royal ∗ Speaker. tlweege,nwhdoi rs-eto eut ne in results cross-section hadronic new energies, low At ayrslspeetdhr r rlmnr:te r o la not are they preliminary: are here presented results Many tnadMdli reviewed. is Model Standard Abstract: PROCEEDINGS < [email protected] √ α < s ( M ∗ h urn ttso xeietltsso h lcrwa se electroweak the of tests experimental of status current The e,bto eeac oeetoekpyisaetoeo th of those are physics electroweak to relevance of but GeV, 5 Z 2 ) R = σ σ (e 0 (e + e + − nentoa uohsc ofrneo HEP on Conference Europhysics International e − → → hadrons) µ + µ − ) igfo h ako higher-order of lack the from ming + e h xeietlerrors. experimental the etfwyasaeconsidered. are years few next − rmtenwcmlt LEP complete now the from tro h tnadModel Standard the of ctor fteSadr oe i a via Model Standard the of nBiig hn,hsbeen has China, Beijing, in olsosaedsusd The discussed. are collisions rcdn umr20.A 2001. this summer in preceding reviewed is these of h earn EAand HERA Tevatron, the eietluncertainties perimental eldepiil o lack for explicitly belled eteo-asenergy centre-of-mass e kae srpre and reported is okhaven BHAM-HEP/01-02 1Otbr2001 October 31

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ratio e PrHEP hep2001 PrHEP PrHEP hep2001 generator, c resonance 4 GeV. Many . David Charlton 1 LUARLW (b) (a) s < √ ediction of the value of (GeV) (GeV) the detector acceptance sample from CMD-2 [2] of the cm cm < E E e 1, where the improvement 36 range; (b) in the c 6% is obtained at each of the . to be as low as 2-3%. clear. Around 1000 hadronic es in the range 50 to 87% from s ion to the overall cross-section ), is the lowest-order QED pre- timated to be 3.3%, providing a √ s (3 / is of most concern. Good descriptions (0) s 2 √ πα – 2 – ) = 4 − µ + µ → 2 3 4 5 were made, in collaboration with the Lund Monte Carlo − e s BESII (1998) BESII (1999) Gamma2 MarkI pluto + 3.8 4 4.2 4.4 4.6 √ (e 0 σ collider at Novosibirsk taken over 0 − e 5 4 3 2 6 5 4 3 2 1 + production.

− R Value R R Value R π + π Measurements of R from BES: (a) Over the full A key application of the low energy R measurements is in the pr In order to achieve such an improvement, detailed studies of At even lower energies, analysis continues of the large data Figure 1: International Europhysics Conference on HEP exclusive final-states are studied,arising with from the main contribut region[1]. where the denominator, of the hadronic event data were obtained from a tuned version team. The experimental acceptance for hadronic events vari diction. The BES measurements [1]in of quality R are over presented previous, inevents Figur often are very used at early, each measurements85 energy, is energy and points. an average The precisionfactor point-to-point of of correlated 6. 2 error to is 3 es improvement over earlier measurements. 2 to 4.8 GeV respectively, so the modelling at low for hadronic events at low at the VEPP-2M e and the hadronic model-dependent uncertainty is estimated PrHEP hep2001 , of a decay ω τ is measured a term contains ω David Charlton . , respectively) are (5) had ) α 2 top Z red using two sets of adronic cross-section . α s the low energy range ontinuous monitoring, M ) ( ew measurement of the also be made of iǫ vered region between 1.4 should give substantially top round the evacuated beam e new BES-II data. With ergy ring to work together − this integral. More sophis- α ) lation [3] using minimal as- and ∆ 2 of-mass energies than before ersion integral: Z ructed to have an extremely s s. The ∆ ∆ ( rons above a fixed energy cut- sion frequency erms of the mean proton NMR M R − eµτ ) − α 00020 may be obtained [4]. 2 Z . s c ( 0 i µ M s ± ( B m h ds 00036, approximately a factor two more a . e (5) had 2 π (0) R ω 0 α ∞ m α R ± − 4 = ∆ Z λ 2 − ℜ – 3 – ) = 2 2 − Z 2 Z 02761 π µ . g 3 a , by measuring the spin-precession frequency, M mass scale. This is modified from its zero-momentum αM ( µ ≡ a 0 − µ ) = 0 eµτ a 2 Z α )= ∆ M 2 Z ( − M (5) had 1 ( α (5) had )= α extracted from: 2 Z ∆ µ 03599976(50), by vacuum polarisation loop corrections: . M a ( α 137 / , and p ω (0) = 1 α Prospects for further improvements in measurements of the h the electromagnetic coupling at the Z International Europhysics Conference on HEP value, spectral function data viasumptions has isospin obtained symmetry. ∆ A recent calcu The contributions from leptonic and loops (∆ The circulate inuniform a magnetic special-purpose field across storage its ring aperture. const The spin-preces The R data pointsticated must, methods at are least, employed be by interpolated different to authors, evaluate and use may by observing the time variationoff of (2 production GeV), of as decayNMR shown elect probes: in Figure one 2. fixedand set The another mounted mean set around bending placed the onchamber. field ring a is In and trolley practice, measu used which the for can magneticfrequency, c field be is pulled re-expressed right in a t sufficiently well calculated knowing only the particle masse precise than a previous similar estimate which did not use th extra theory-driven assumptions, an error as low as at low energiesincreased are luminosity; good: CLEO proposes anto to examine upgraded run the region at accelerator from lower in 3with centre- to radiative Beijing 5 GeV; events; DAΦNE and maywith finally be the able the to present concept acces PEP-II ofand LER a 2 could very GeV. give low access en to the poorly co 3. The Muon Anomalous Magnetic MomentThe g-2 Brookhaven E821muon experiment anomalous has magnetic moment, recently reported [5] a n low-energy hadronic loops, and must be calculated via a disp polarised muons in a magnetic field: PrHEP hep2001 , 10 are − . To − µ ectro- 10 a µ × 9 ] 10 s 29) . × s vertex, which [µ 0 µ David Charlton s ± µ µµγ and 3 57 Time . + 32-82 µ t and higher-order vac- 467-700 9 and possible new physics e of loops. The QED and ear future. ) 10 s nty on the predicted er vacuum polarisation term ( 10 × s ˆ 2GeV in E821[5]. The periodicity illion: 1.2 ppm from statistics e calculated using a dispersion 2 − K µ imple QED s ) decays is [5]: s 10 terms. The lowest-order (vacuum ( + E > × ), optional additional theory-driven ) = (11 657 470 R µ 2 Z 9 6) ds M 2 π ( 10 ± ∞ QED m 233-467 α ( 4 × 14 µ Z a 95 ± . 2 (0) π s – 4 – 2 3 µ α . The hadronic corrections, although much smaller )= 10 − LO 32-233 32-233 10 ; = (11 659 202 × + had µ s ( 4) µ a . µ 0 a is the ratio of muon to proton magnetic moments. ± λ 2 . 650-700 = 2 at lowest order. The corrections may be subdivided into el and g p 0 50 100 150 200 7 6 5 4 3 2 /ω ) = (15 a

ω

10 10 10 10 10 10 10 ) is a known bounded function. As for Number of Positrons/150ns of Number Time spectrum of positrons observed with energy s = ( weak ˆ ( R K µ ), the dominant corrections may be subdivided into the lowes a The latest E821 result, obtained using 0 Interpretation of this result in terms of the 3 α ( assumptions may be made. Recent estimates of the lowest-ord Figure 2: International Europhysics Conference on HEP where from spin precession is observed over more than ten muon lifetimes. where uum polarisation terms and higher-orderpolarisation) “light-on-light” term is numerically muchrelation: the largest. It can b magnetic (QED), weak andweak hadronic terms parts according are to respectively the calculated typ to be O The overall precision obtainedand is 0.5 relatively ppm 1.3 from parts systematic per errors. m Data from a further 4 requires detailed calculations of loop corrections to the s in hand, and should result in a factor two improvement in the n than the QED correction, provide the main source of uncertai and gives the original PrHEP hep2001 led to µ a 10 − . µ predictions. 15 a ± David Charlton about the treat- 6 9 9 8 6 8 16 15 11 10 ± ± ± ± ± ± − ± ± ± the new and previous 10 iations [5]. More recent 695 700 701 695 692 702 × 703 695 699 5 ∼ 821 publication was that of her the input experimental n too optimistic. At present tandard deviation level, thus ployed is mostly in common. m the new E821 measurement owest of the calculations. ilable calculation of s agree with each other within (LO; hadronic) / 10 ns, as it may be included either µ a 10 x 10 µ a – 5 – data data, QCD sum rules data data data data τ τ τ τ τ τ & & & & & data & data − − − − − − − − e e e e e e e e + + + + + + + + e e e e e e QCD+renormalons & data Based on e e Recent calculations of the lowest-order hadronic correction to + + + µ µ µ 11659000 11659200 11659400 − + Measurements of the muon anomalous magnetic moment and recent µ µ Table 1: Authors BW(96) [6] CLS(01) [13] DH(98/1) [8] DH(98/2) [9] N(01) [10] J(01) [11] ADH(98) [7] ADH(98) [7] dTY(01) [12] The summed corrections are shown in figure 3 and compared with E821 (99) CERN E821 (98) Recent calculations Narison, Jegerlehner, de Troconiz+Yndurain, Davier+Hocker Cvetic+Lee+Schmidt World average 11659203 CERN E821 (97) Figure 3: ment of further photon radiationhere in some or of as these calculatio adata higher-order includes final-states correction, with dependingthe extra also photons. overall errors, on The which estimate whet It is is not notable surprising that sinceDavier the the and best (“DH(98/2)”), H¨ocker data value which available is em at numerically the the time l of the E are shown in Table 1. There is some ambiguity at the level of International Europhysics Conference on HEP measurements [14]. The major experimentalis improvement fro striking. At the time of publication, the most precise ava a difference between datacalculations and reduce theory that of difference, around inalso some 2.6 suggesting cases that standard to the dev the error one on s the prediction may have bee PrHEP hep2001 ) b FB A for many surements of David Charlton ts from LEP and SLD lised [15, 16]. Recently w has a comparable preci- or, as expected in the near 0.0012 gging techniques and various -backward asymmetry ( 0.00036 ven more severely challenged ± 0.00041 0.00053 0.00026 0.00031 0.00079 0.00017 fetime results are compatible, ± ained over earlier lifetime-tag ± ± ± ± ± ± 0.0021 GeV um physics return from such a ± Preliminary 5.1 GeV ± . 0.2324 = 0.02761 /d.o.f.: 12.8 / 5 0.23099 0.23226 0.23272 2 = 91.1875 (5) had 0017 = 174.3 Z t χ . ∆α∆α m m 0 lept eff ± θ 2 – 6 – sin 0990 . as giving evidence of physics beyond the Standard . In doing this, it is effectively assumed that the b µ a = 0 lept eff b θ , Pole 0 FB 2 0 A 2 3 0.23 0.232 0.234

) 0.23159

>

τ

H 10 10 fb

GeV cross-section, width, and asymmetries have been available m ] (P (SLD) 0.23098 [ fb fb fb l l 0,b 0,c 0,l Q 0 A A A A < Average 0.23152 A in terms of sin b FB A Comparison of asymmetry measurements interpreted simply as mea . lept eff This result may be compared with other asymmetry measuremen θ 2 from ALEPH and DELPHI, using inclusivequark lifetime-based charge b-ta indicators.measurements, Substantial so improvements that are this obt typesion of to that asymmetry using measurement a no and traditional together lepton give tag. a The LEP lepton average and Z li pole asymmetry of Measurements of the Z years from LEP and SLDnew data, results and [17] most have results become have available now on been the fina b quark forward by an experimental measurement withfuture. a Theoretical factor progress two is smallerprecise essential err measurement. to obtain a maxim 4. Recent News from the Z Model. The accuracy of the theoretical predictions will be e sin Figure 4: there is therefore no reason to consider International Europhysics Conference on HEP by interpreting PrHEP hep2001 differ ) [20]. 0 ry from fb bosons in Q ′ 1.89 0.678 0.463 0.436 0.800 , as indicated 0 Limit (TeV) David Charlton , differ at the level 95% CL lower limits vements in b quark b FB these data [21]. As an η A χ ψ o around 500 GeV (see may help elucidate this LR ) [18]; from the left-right d Model expectations de- r hadronic, muon and tau Model τ backward asymmetry [19]; e presented at this confer- ation is not compelling at described by the Standard P Sequential e result is shown in figure 4, and rk couplings to the Z try measurements ( s for non-radiative events at at the Tevatron, in the Drell- various models [21]. Table 2: on the mass of new Z [21]. Analogous measurements ty to new physics models, and sed forward-backward b quark LR A , from per exper- lept eff θ 1 2 − – 7 – bosons which do not mix with the Z ′ from the entire LEP 1 polarisation measurements ( − τ values derived from the leptonic forward-backward asymmet lept eff θ 2 ) [15]; that from the l , 0 fb A With the completion of LEP-2 data-taking at the end comparing to sin quark couplings are given by their Standard Model values. Th International Europhysics Conference on HEP the full range of LEP-2pair final energies states, are averaged shown between all inhave four Figures been LEP 5 experiments made and for 6scribe electrons, fo b the and data c well.example, quarks limits [21]. may Limits be The can placed Standar on be new placed Z on new physics from programme. Following on fromLEP-1 the Z measurements lineshape ofstudies the and of fermion-pair forward-backward production have asymmetries, continued2. at LEP- At thesesubdivided higher into energies, those fermion-pair where“radiatively events the returned” may to pair be the invariant Zradiative mass region events has or with below, close andergy. to non- the The full cross-sections centre-of-mass and en- forward-backward asymmetrie LEP ( polarisation asymmetry at SLDand [16]; from inclusive from hadronic the event charm forward-backward asymme forward- in Table 2. 6. Z’s and W’s at Colliders withElectroweak fermion-pair Hadrons production hasYan also process. been studied Updatedence results on [22, high 23]: massModel electron both expectations, pairs cross-sections and wer and extendFigure asymmetries 7). beyond As are the indicated LEP-2 well improvements in on mass the that reach figure, of there t LEP is should some come sensitivi with the Run 2 data. The two most precise determinations of sin from the Standard Modelpresent, expectations, and direct but measurements suchasymmetry via an at the interpret SLD left-rightasymmetry are polari measurements not using precise theissue, enough but existing scope to LEP for data help. such samples improvement is Future limited. impro 5. LEP-2 and Fermion-Pair Production of 3.2 standard deviations. This might suggest that the b qua of 2000, theof integrated 161 luminosity GeV collected and at above has energies reached 700 pb iment, in total giving each 1 fb PrHEP hep2001 2 Q ng all 0.370 0.180 0.089 0.270 0.084 0.060 ± ± ± ± ± ± ia t-channel LEP preliminary Mass (GeV) David Charlton 80.360 80.410 80.470 80.350 80.498 80.454 ν e (GeV) sed their Run 1 result ) s )  γ γ → ( √ ( − e lepton-missing momen- − µ τ + + 0.85 -sections as a function of > →µ →τ

− − LEP combined fermion pair W mass from the Tevatron are p data s e e  + +  Â/ e e s  W mass measurements from hadron √ All p D0D0 Run 1A Run 1B 120 140 160 180 200 220 UA2 W 1 0 0 CDFCDF Run 1A Run 1B

0.8 0.6 0.4 0.2 0.2

FB FB -0.2

Forward-Backward Asymmetry Forward-Backward

A -A Experiment Sample

meas SM Figure 6: forward-backward asymmetries in the LEP-2 energy region[21]. Table 3: colliders. – 8 – 17 GeV, at this conference [23]. LEP . 0 preliminary ± ) γ (GeV) = 2.23 p collisions provided, ) s )  γ γ ( √ ( − W − µ τ + + hadrons( 0.85 > →τ → →µ

− − − 13 GeV) [25] some time ago. D0 presented a new measurement usi s e e e .  + + +  0 Â/ e e e LEP combined fermion pair cross- s  ± √ 2 120 140 160 180 200 220 1

1

0.9 0.8 1.2 1.1

10 10

Cross section (pb) section Cross = 2.05

SM meas

/ The high tail of the distribution of the transverse mass of th W production in p The presence of the is primarily probed at HERA v σ σ Figure 5: sections in the LEP-2 energy region[21]. W International Europhysics Conference on HEP summarised in Table 3. tum system provides information(Γ about the W width. CDF finali before LEP-2, the only directof measurements the W mass, usingand muon reconstructed momenta and electron inferred missing mo- mentum information. The main resultsCDF from and D0available from for Run some 1cently time data updated [24]. have their been new Run D0 analysis 1 have making results re- to use with calorimeter of a cell electrons edgesportance [23]. close of The the extra main data im- iscalorimeter to calibration allow a from better Z events. Measurements of the the Run 1 data, of Γ exchange. The charged and neutral current differential cross PrHEP hep2001 2 ∨ neutral /GeV 2 2 Q 4 p 94-97 Q p prel. + - 10 p 94-00 prel. p − + David Charlton H1 e H1 e ZEUS e ZEUS e 3 10 Neutral Current rm (and also, indirectly, via t process proceeds only by W 0.9 < Standard Model (H1 97 PDF Fit) y Neutral-current differential cross- -1 -2 -3 -4 -5 -6 -7 1

10

10 10 10 10 10 10 10

NC

/ pb GeV pb / /dQ d

σ

-2 2 Figure 9: sections measured at HERA[27]. exchange can be seen in the high- 0 2 – 9 – /GeV 2 Q 4 p 94-00 prel. p 10 − + H1 e H1 e Measurements of Drell-Yan lepton-pair production by CDF. p 94-97 p prel. + - 3 Charged Current 10 Charged-current differential ZEUS e ZEUS e 0.9 s=320 GeV < Standard Model (H1 97 PDF Fit) √ y Figure 7: -5 -6 -7 -8 -1 -2 -3 -4 1

10 10 10 10 10 10 10 10

CC

/dQ d pb GeV pb

σ

2 -2 cross-sections measured at HERA[26]. Figure 8: International Europhysics Conference on HEP are shown in Figures 8 andexchange, 9 and respectively. is The sensitive charged tothe curren the overall W normalisation). mass via The the propagator effect te of Z PrHEP hep2001 ]. decays being ing for events τ David Charlton p cross-sections. ents from the full + se events have been o an expectation of W [31] Monte Carlo ecoiling hadronic system perimental and predicted p and e nnels with 9] is shown in Figure 10, ransverse momentum, and − nd have needed only minor t by between two and three mately 2% lower than earlier new calculations describe the the framework of the Standard on performances give efficiencies Preliminary ] ) corrections to the doubly-resonant W- YFSWW 1.14 RacoonWW α GeV ( [

O cm E – 10 – 18 17 16 RacoonWW / YFSWW 1.14 160 170 180 190 200 210 LEP

5 0

20 15 10

pb

] [ σ LEP averaged W-pair production cross-section measurements[29 WW Figure 10: 0.3, which is 90% composed of W production and decay [28]. The Real W production may also have been observed at HERA, by look Each LEP experiment now has a sample of around 12000 W-pair ev ± interpreted as possible evidence ofModel new their physics, natural but interpretation within is as W production. 7. W Physics at LEP-2 current region where it gives rise to a difference between the e International Europhysics Conference on HEP with high transverse momentuma electrons recoiling or muons, hadronic missingabove system. t 40 GeV, For H1 transverse2.0 and momenta ZEUS of together the observe r 6 events compared t LEP-2 data sample.optimisations Event for selections the are highestand energy well data. purities established, in Typical a selecti the 80-90% range for almost all channels – cha predictions. The agreementcross-sections can as be a tested by functionnormalisation comparing of of the centre-of-mass the ex energy. datastandard deviations The well, of the the old experimental error ones [29]. over-estimate i pair production diagrams, and give a cross-section approxi the most challenging.and compared The to measured theprograms. predictions W-pair of These cross-section the programs [2 RacoonWW incorporate [30] full and YFSW PrHEP hep2001 ± 43 . 0.032 0.049 0.051 0.038 0.028 0.054 results ”), are qqqq”), ± ± ± ± ± ± ℓν 0.21 0.039 ℓν → ± ± ) = 10 qq qq 0.038 0.045 0.048 0.053 0.033 0.030 ℓν ± ± ± ± ± ± → → David Charlton 80.40 → er. Other, more 80.450 t LEP-2 by direct W Mass (GeV) y branching ratios. ount of information 091 GeV is found. 80.477 80.399 80.389 80.491 80.448 80.457 . 0 ic results are consistent ructed event quantities, W mass measurement is ± by the four LEP experi- lepton momenta and jet y (“WW good consistency between s very similar for the two g W’s (“WW roves significantly on the Tevatron W and Z cross- expectation of 10.83%. It he LEP beam energy, and average leptonic branching olliding beam particles, thus ich is Br(W nstructed mass distributions 150 ion from the fitted events are . ment now has a better than nt between the two channels: leptonic decay events. This fit W mass measurements from = 2 (161 GeV) ℓν W qq qqqq WW σ → → Table 5: LEP [33, 34].reconstruction technique Results unless indicated. are from the direct From LEP combined ALEPH (1997-2000) WW DELPHI (1997-2000) L3 (1997-2000) OPAL (1997-1999) WW Sample – 11 – 0.17 0.16 0.22 0.09 0.27 ± ± ± ± ± events, which has been included in the WW 10.54 10.54 11.09 10.69 67.92 ℓνℓν Branching ratio (%) → ν e ℓν τν µν W decay branching ratio measure- hadrons → → → → → W W W W Decay mode W The selected W-pair events are also used to measure the W deca The W mass and width are measured above the W-pair threshold a After the kinematic fit, the W mass statistical sensitivity i Table 4: ments from LEP[29]. 25% [32]. . International Europhysics Conference on HEP used by all experiments.constraining the total A energy and kinematic momentumreconstructing fit to be the is that unobserved of made the neutrino c tosignificantly in improves the mixed the reconst hadronic- resolution oncan the W be mass. fitted Thecomplicated, to reco techniques obtain to extract the the Wused most W by mass, mass some or informat experiments. thecontained ALEPH in W and WW mass OPAL also and use width the togeth small am The combined LEP resultswith [29] lepton are universality, shown and inratio, so Table are 4. corrected combined to The to lepton massless1% measure relative charged the error, leptons. andis This is significantly measure consistent more with precisesection the data, than Standard assuming Standard a Model Model value production extracted of W’s, from wh the or where one W decays hadronically and the other leptonicall reconstruction of themomenta W and decay energies. products [33], Events using with measured two hadronically decayin 0 quoted. event types. The systematicthe error main sources correlated are systematics largelyhadronisation come differe modelling. from the The knowledgements, W and of mass averaged t by measurements channel,all obtained are the shown in measurements, table60 5. and MeV There the from is hadron overallessentially colliders. precision unchanged, If and [34] the a now W LEP width imp combined value is of also Γ fitted, the PrHEP hep2001 ) (see text) q decays may Q q ( David Charlton D → qqqq channel (see 0 data 98-2000 (++,--) inter+intra BEC intra BEC tistical and 30 MeV → cally, the decay distance ble effects of FSI models. as follows [34]: The LEP eriments, has focused on nergy, where a concerted ty over final-state interac- MeV; detector-related un- ents that are expected be- ed to study possible effects, t 27%, in the average. With he statistical error would be ate interactions. uned to Z en different experiments, and MeV to all channels; hadroni- ute 10 MeV; and uncertainties ation of the two systems may “final-state interactions” (FSI) the WW Distribution of dentical particles formed in the shower phase of the Monte Carlo Figure 12: for DELPHI data,Monte Carlo compared models[37]:correlations to within “intra” different one refers Wthose decay, to between “inter” W decays. to – 12 – ) resc φ L3 data 189-207 GeV N R rescaled angle ( % Particle flow ratio for parti- No CR SKI SKI 100 Particle flow (all clusters) 0 0.2 0.4 0.6 0.8 1 1

0.8 0.6 0.4 1.4 1.2 The 39 MeV error on the combined LEP result includes 26 MeV sta The basic physical problem which gives rise to the uncertain A substantial effort has been spent in understanding the possi

(A+B)/dn/d dn/d (C+D) φ φ Figure 11: cles between jets comingrelative from to the those sameent between W W’s[35]. jets Datawith from are no differ- compared colour reconnection, tomodel[36]. and models to the SKI International Europhysics Conference on HEP not properly describe them.subdividing them Phenomenological into “colour models reconnection” are inmodels, the us parton- and possible Bose-Einsteinhadronisation correlations process. between i systematic contributions. Systematic errors are larger in Table 5), having the effectno of systematic deweighting errors that this channel,22 to deweighting MeV. jus would The not main occur, systematicbeam and energy errors t measurement on contributes the a highly combinedsation correlated result modelling 17 are uncertainties contribute anotherbetween 17 the MeV; hadronic decay productscertainties – of different two for W’s the contributeon different 13 photonic experiments corrections – contribute contrib 8fore MeV. the The results main are improvem programme finalised is lie in in progress to the reduce areas the of error, the andtions LEP the is beam final-st that e when twois W’s smaller in than the typical sametherefore event hadronisation not both scales. be decay independent, hadroni The and hadronis so hadronisation models t Recent work, in adetermining collaborative the effort common sensitivity between to all different models four betwe LEP exp PrHEP hep2001 p Q → t low decays, and ℓν David Charlton qq → at LEP-2 [45] in the 033 GeV is obtained. . iments to improve the 0 resent constraints from ng vertex in two of the en obtained by studying ± ibed by Standard Model 069 GeV. ) uplings therefore provides . lings of the vector bosons, ectroweak gauge couplings 0], but no combined LEP models. es from different W decays 0 Q d decay angle distributions. ( imental precision [42]. tions between particles from e colour reconnection models, 38], in this case by comparing 451 ρ erved of such an effect. As for ± -order corrections, previously LEP results in order better to . also been made at LEP-2, and . erence [46]. ) 134 Q y to possible anomalous couplings . ( )+∆ ). This may be expressed as [39]: Q ) may be examined: ) = 2 ( WW mix Q Q ρ ( ( W WW production. The cross-section measured ρ WW mix D 0 ρ )+ Z WW 0 ρ Q ( )+ – 13 – W Q qqqq events [36]. This is illustrated in Figure 11. , given in Table 5 is combined with that from p ( ρ , for single hadronically decaying W’s in WW 2 and Z ρ W W → ρ γ m ≡ 0 ) qqqq events ( Q ) = 2 ( → Q D ( WW ρ ) distribution is shown in Figure 12: a deviation from unity a Q ), and for WW ( W D ρ is evaluated from mixing hadronic W decays from WW qqqq events. Alternatively the ratio → WW mix ρ events ( When the LEP measurement of Sensitivity to the effect of colour reconnection models has be Bose-Einstein correlations are also being studied in data [ W-pair production at LEP-2 involves the triple gauge coupli Other measurements of triple gauge boson couplings are made is any extra part arising from correlations between particl ℓν ρ in WW would most clearly signaldifferent the W’s. effect As illustrated of incolour Bose-Einstein this reconnection, correla figure, work no is evidence inconstrain is progress the obs to possible derive effect combined on the W mass measurement. An observed on developing ways to measure visible effects predicted by the International Europhysics Conference on HEP the particle flow between jets in WW colliders as given in Table 3, a world average W mass of 80 The data show some sensitivity to theand effects as work predicted continues in th tosensitivity. combine results from the four LEPthe two-particle exper correlation functions, ∆ qq where A similar combination of W width results gives Γ for the latterpredictions. process Measurements is of quartic shownwere gauge in discussed couplings in have Figure detail 13 in other and contributions is to this well-descr conf 8. Tests of the Gauge CouplingsThe of gauge Vector group Bosons ofboth the in Standard form Model and dictatesa strength. the fundamental The test self-coup direct of measurementhave the of been Standard these measured Model co directly gaugeLEP at structure. are both more El LEP stringent. and the Tevatron: atthree p lowest-order doubly-resonant diagrams.is Sensitivit found in the W-pairMeasurements cross-section, have and been the Wresults reported production have an at been previous releasedneglected, conferences are recently [4 thought because to be [30, comparable 41] to higher the currentneutral exper vector boson processes of Z PrHEP hep2001 , p top m 1 GeV . ontour. 5 ± . The LEP 3 . H m David Charlton = 174 ] compared to Standard top [50] and, new this year, m s boson, [51] during the final stage of 1 LEP and SLD can be used . If consistency with the andard Model parameters. troweak data are included, ramework of the Standard in the Standard Model for TOPAZ0 version 4.4 [48] to 2]. d out such global tests via a ns may be used together to ur) of tainties are included following s conference. These global fits top ctions and their interplay with m Preliminary and N”) scattering W ] ν m GeV [

033 GeV obtained by combining LEP and p . cm 0 E – 14 – ± result obtained differs from the expected value by three W uncertainty θ 451 . 2 % 2.0 ± YFSZZ ZZTO = 80 W LEP m N and APV results to predict the masses of the top quark, ν 170 180 190 200 0 1

0.5 1.5

NC02

pb ] [ σ ZZ ), the . The result obtained is shown in Figure 14 by the solid (red) c 2 Z W M ( m as measured in neutrino-nucleon (“ α W LEP averaged Z-pair production cross-section measurements[43 N scattering result was reported by the NuTeV Collaboration θ ν 2 Before making the full fit, the precise electroweak data from A new 1 electroweak working group has,combined for fit a to number a of largeThese years, number results carrie of are measurements reported sensitiveuse here to the for St the electroweak libraries dataprovide available ZFITTER at the version thi Standard 6.36 Model [47]detailed predictions. and studies Theoretical of uncer missingQCD higher corrections [49]. order The electroweakas precise corre are LEP, SLD sin and Tevatron elec Figure 13: International Europhysics Conference on HEP results; and the expected relationship between Model predictions[44]. 9. Global Electroweak Tests Many of theprovide individual a results global reportedmodel test in is of preceding observed, consistency sectio itModel, with is the the justifiable unknown Standard to remaining go Model parameter, on the to mass deduce, of in the the Higg f atomic parity violation (“APV”) measurements in caesium [5 together with and of the W, Also shown are the direct measurements (dotted/green conto preparation of this contribution. The sin standard deviations. from the Tevatron [53] and PrHEP hep2001 g but W n 8.6% m es. ctions depend measurements. redict values of David Charlton ne. ndard deviations W , the best-fit value m 2 χ and the pull calculated , which is a reflection of and n the shape of the curve. rement is twice as precise as a function of the mass b FB he measurement error. The 2 top A use of the inclusion of a new st fit value of the Higgs mass to this Standard Model fit is similar χ , but it is currently included m ecise input data and the direct ctly predict the mass of heavy Preliminary ] ). This latter effect is controversial, 2 Z [54]. This has little effect via ∆α W /m GeV m 2 W [ N, APV Data

m t ν 1000 − m – 15 – Data (1 − ] W 300 κ CL = % GeV [

68 LEP1, SLD, LEP2, pp 114 lept eff H θ m 2 130 150 170 190 210 , is shown in Figure 16. The darker shaded/blue band enclosin H

80.6 80.5 80.4 80.3 80.2 m

W

GeV m ] [ Comparison of direct and indirect constraints on the top and W mass of the fit is 22.9 for 15 degrees of freedom, corresponding to a GeV, where the error is asymmetric because the leading corre 2 consistent with those observed – in both cases within two sta (shaded/yellow). It can be seen that the precise input data p χ 35 W H +53 − measurements favour a light rather than a heavy o . The variation above the minimum value of the m m H top curve provides an estimate of the theoretical uncertainty o m = 88 Figure 14: 2 and m Going further, the full fit is made including also the H / χ m top W probability. To provide an impression of the contributions different International Europhysics Conference on HEP The overall m – demonstrating that theparticles. electroweak corrections For can the corre W,to the that precision of of the theas direct prediction the measurement. via prediction. For the It the ism top observed mass, in the addition that measu both the pr of each input datumas is the difference compared between with observationresults the and are actual best-fit shown divided measurement, in by Figure t 15. The poorest description is of on log the same disagreement discussed earlieris in Section 4. The be of the Higgs boson, This band is ahigher-order little (fermionic broader two-loop) than calculation of previously estimated beca the and may well overestimate the true theoretical uncertainty does have an impact via sin PrHEP hep2001 ) [4] 2 Z Higgs M ( (5) had α David Charlton ugh luminosities are so 1 data, taken from 1989- the contributions of SLD, tive mixing angle are not ts can be expected over the moves to 222 GeV with this he W mass measurement, from H rticular, and in gauge-coupling c corrections to ∆ s describe precision electroweak m in the next couple of years, which 1 − -3 -2 -1 0 1 2 3 -3 -2 -1 0 1 2 3 – 16 – prediction is sizable compared to the theoretical 0.00036 -.35 0.0012 .86 0.037 1.60 0.0021 1.22 0.0023 -.48 0.039 1.32 0.060 .93 0.025 1.11 0.00065 1.12 0.0031 -.12 0.0021 1.47 0.00095 .69 0.0017 -2.90 0.0034 -1.71 0.020 0.026 -.64 .06 5.1 -.30 0.70 .56 0.0021 .03 0.0033 -.54 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± H Summer 2001 Summer m 0.922 0.922 0.670 174.3 174.3 Pulls from the global electroweak fit. Measurement Pull Pull 41.540 41.540 2.4952 2.4952 80.454 80.454 80.450 80.450 20.767 20.767 0.1719 0.0990 0.0990 0.0685 0.02761 0.02761 0.21646 0.21646 0.01714 0.01714 91.1875 91.1875 ] ] ) 0.2324 fb ) ] ] N) 0.2255 N) ] ] ] ] Z ] (Q GeV GeV ν ν 196 GeV at 95% C.L. Also shown in the Figure is the effect of [ [ ( (

(m nb lept W eff W )) 0.1465 [ GeV GeV ττ

< θ θ θ θ GeV GeV GeV GeV [ [ (Cs) -72.50 (Cs) [ [ [ [ 2 2 2 2

(5) had

Z t Z (LEP) (TEV) W W t (SLD) (P(P (SLD) 0.1513 W W ll bb cc 0,c fb bb cc l 0,l fb ll 0,b fb l 0 Z Z had H sin ∆α σ sin Q Γ m AA AA AA A sin m m m sin Q ∆α m Γ σ RR AA AA RR RR AA A m m m Figure 15: m curve may be used to derive a constraint on the Standard Model 2 χ estimate. At the Tevatron, Run 2 data-taking has recently begun. Altho (5) had α boson mass, namely as equivalent two-loop calculations for Z widths and the effec available. The using an alternative theory-driven estimate of the hadroni International Europhysics Conference on HEP ∆ far low, the expectation remains of accumulating 2 fb 10. A Forward Look, and Conclusions The eleven years of data-taking by the LEP experiments, plus have established that Standard Modelmeasurements. radiative correction Data analysis1995. is Work close continues to to complete finishnext couple LEP-2 on of analyses, the years. and Improvements LEP- final canbetter still resul understanding be of expected in final-state t measurements interaction where effects the in full pa data sample is not yet included. (dashed curve). The effect on the uncertainty, for example. The 95% C.L. upper limit on PrHEP hep2001 W as a m 2 χ ee standard for the global H David Charlton m ass precisions by a ach experiment [55], the global fit ∆ urement error close to in muon decays to LEP employed for the future wait for the LHC and a andard Model have been H ossible cracks in the Stan- ome from a discovery of the r example the measurement m to radiative corrections, and Further improvements in the lest Standard Model particle. y have to await an improved tical uncertainty, and the lighter n particular further elucidation Preliminary ions for some processes, and more blished. Two and three-loop calcu- ] curve as a function of 2 χ 0.00036 0.00020 ± ± GeV 100 = [

(5) had H ∆α∆α 0.02761 0.02738 – 17 – m theory uncertainty 3 GeV. Combining the former result with the final ± Excluded

20 400

6 4 2 0

∆χ 2 , are shown in Figure 17 (the central value of H from the b forward-backward asymmetry at LEP, show two or thr m Constraining the Standard Model Higgs: ∆ lept eff θ 2 Further substantial improvements in precision will have to In summary, precise tests of the electroweak sector of the St deviation differences from expectationdard which Model might description, point but nonequality to of are p compelling tests will at arrive present. of slowly the over the electroweak next symmetry-breaking few mechanism years: will i likel is, of course, arbitrarily selected). made by a wideand range the of Tevatron. experiments, Many from ofthe the these radiative g-2 tests correction measurement structure have a is now highlations rather sensitivity are well-esta essential in makingprogress sufficiently precise is predict still needed.of A sin small number of measurements, fo future linear collider.further factor The two. LHC TheHiggs main should boson, improvement would, improve and of a the course, direct W c indication of and whether it top is m the simp function of results from LEP-2 should20 provide MeV. The a effect world such average improvements W could have, mass for meas example on electroweak fit. The shadedshaded band area shows shows an the estimate region of excluded the by theore direct searches. should allow a Wand mass a measurement top with mass 30 measured MeV precision to from e Figure 16: International Europhysics Conference on HEP PrHEP hep2001 et (2000) Preliminary ] A 675 2 David Charlton 10 curve obtained with GeV [

2 H χ Summer 2001 Future (Run 2a) m Nucl. Phys. (2001) 2227; I.Logashenko, (2000) 69. (1999) 1632; H.N. Brown appear in Physics Letters. measurements of 20 MeV and 86 82 Typical ∆ top (1998) 123. m Excluded B 492 6 4 2 0

.

C 2 and

; J.C. Chen, these proceedings.

∆χ 2 . (1996) 3237. W Figure 17: 3 GeV precision,compared to respectively the current fit (dashed) result(solid). central and value m (2000) 091101. Phys. Lett. (1998) 419. (1998) 427. Phys. Rev. Lett. Phys. Rev. Lett. D 54 – 18 – D 62 , CMD-2 Collaboration, Eur. Phys. J. B 419 B 435 hep-ph/0106025 (1979) 1; et al. hep-ex/0102003 hep-ph/0107069 Phys. Rev. . (2001) 53. Phys. Rev. B 150 Phys. Lett. Phys. Lett. B 513 , Muon g-2 Collaboration, , Muon g-2 Collaboration, Nucl. Phys. hep-ph/0104304 ., , BES Collaboration, et al. et al. Phys. Lett. et al. et al. , Muon g-2 Collaboration, 424c. these proceedings. R.M. Carey al. [5] H.N. Brown [4] A.D. Martin, J. Outhwaite and M.G. Ryskin, [3] H.Burkhardt and B.Pietrzyk, preprint LAPP-EXP 2001-03, to [2] See, for example, R.R. Akhmetshin [8] M. Davier and A. H¨ocker, [7] R. Alemany, M. Davier and A. H¨ocker, [6] D.H. Brown and W.A. Worstell, [1] J.Z. Bai [9] M. Davier and A. H¨ocker, discovery reach for a Higgs boson. Acknowledgments International Europhysics Conference on HEP The preparation of this talkby was greatly the eased working of group, the and cross-LEP LEPthe working W electroweak groups mass, work- on gauge couplingmeasurements. and In fermion-pair particular, for IGr¨unewald his thank unstinting Martin help, andHawkes Chris for comments onalso this benefitted manuscript. from thetilogus, I assistance E. Barberio, of A. P. Bodek,Chiarelli, An- D. G. Cavalli, G. Cvetic, Y.S.C. Chung, Gerber, M. F. Elsing, Hi, Gianotti, J. R. Holt,gashenko, F. Hawkings, K. Jegerlehner, G.S. Long, W. M. Menges,Moutoussi, Kuze, K. A. I. M¨onig, C. Lo- Parkes,chini, B. J. Pietrzyk, Timmermans, A. R.H. Valassi, Voss, Ten- W. P. Wells, Venus, F. Yndurain and Z.G. Zhao. References [11] F. Jegerlehner, [12] J.F. de Troconiz and F.J. Yndurain, [13] G. Cvetic, T. Lee and I. Schmidt, [14] J. Bailey [10] S. Narison, PrHEP hep2001 , SLD David Charlton et al. (2000) 67; M. Roth, mitted to this conference. mitted to this conference. B 587 rence. (2001) 1; (2001) 587; (2000) 585; (2000) 371; (2000) 1; (1992) 371; (1992) 436. (2000) 3347. (2001) 131802. (1996) 357; (1996) 183; ALEPH Collaboration, (2000) 1; (2001) 052001; (1998) 225; (1998) 387; C 21 C 19 85 (2000) 222. 87 (2001) 269; H1 Collaboration, paper (2001) 269; H1 Collaboration, paper C 14 C 16 C 14 (2000) 5945; K.Abe Nucl. Phys. C 71 C 69 B 277 84 B 294 84 C 16 D 64 C 19 C 19 B 439 B 429 (2001) 432. 140 Z. Physik Z. Physik Eur. Phys. J. Eur. Phys. J. – 19 – Phys. Lett. Eur. Phys. J. Eur. Phys. J. Eur. Phys. J. f subgroup, note LEP2FF/01-02. Phys. Lett. Phys. Rev. Lett. Phys. Rev. Lett. Phys. Rev. Phys. Lett. Phys. Lett. Eur. Phys. J. (2001) 1162; V.Serbo, these proceedings. Phys. Rev. Lett. Eur. Phys. J. Eur. Phys. J. Phys. Rev. Lett. 86 , OPAL Collaboration, , OPAL Collaboration, , ALEPH Collaboration, , ALEPH Collaboration, , L3 Collaboration, , L3 Collaboration, , L3 Collaboration, , OPAL Collaboration, Comput. Phys. Commun. , CDF Collaboration, , CDF Collaboration, , CDF Collaboration, , ALEPH Collaboration, , D0 Collaboration, Phys. Rev. Lett. , , H1 Collaboration, , H1 Collaboration, , DELPHI Collaboration, , DELPHI Collaboration, , DELPHI Collaboration, , note CDF/ANAL/ELECTROWEAK/CDFR/5139, D0note 3693. , SLD Collaboration, et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. M. Acciarri P. Abreu P.D. Acton M.Casado, these proceedings. M. Acciarri ALEPH 96-097 CONF 98-037; P. Abreu M. Paganoni, these proceedings. Collaboration, G. Abbiendi G. Abbiendi DELPHI Collaboration, DELPHI 2001-027P. CONF Hansen, 468; these proceedings. these proceedings. EPS-2001-787 submitted to thisZEUS conference; Collaboration, papers EPS-2001-630 and EPS-2001-632 sub LEPEWWG/XSEC/2001-03; R. Chierici, these proceedings. M. Acciarri P. Abreu EPS-2001-787 submitted to thisZEUS conference; Collaboration, papers EPS-2001-631 and EPS-2001-633 sub S. Abachi [19] See, for example, P.Hansen, these[20] proceedings. D. Buskulic [16] K. Abe [21] JHolt, these proceedings; LEPEWWG f [17] ALEPH Collaboration, ALEPH 2001-026 CONF 2001-020; [18] D. Buskulic [32] S. Eno [31] S. Jadach [28] H1 Collaboration, paper EPS-2001-802 submitted[29] to The this LEP confe Collaborations and the LEP WW Working Group,[30] note A. Denner, S. Dittmaier, M. Roth and D. Wackeroth, [25] T. Affolder [27] C. Adloff [15] R.Barate International Europhysics Conference on HEP [26] C. Adloff [22] T. Affolder [23] C. Gerber, these proceedings. [24] T. Affolder PrHEP hep2001 int , Ed. David Charlton WG/MASS/2001-02; (1998) 509; ino; D. Bardin, C 1 (2000) 338. (2001) 3260. (1999) 403. . 86 C 6 (1997) 6939; B 495 (1999) 2484; D 56 Eur. Phys. J. (1999) 278. (2001) 229. . 82 (2001) 475. 117 Phys. Lett. 133 hep-ex/9806013 Eur. Phys. J. Phys. Rev. Lett. 140 – 20 – Phys. Rev. (2000) 1618; . . hep-ph/9902452 30th International Conference on High Energy Physics Phys. Rev. Lett. 85 (1997) 1759; 275 Comput. Phys. Commun. , CCFR/NuTeV Collaboration, Comput. Phys. Commun. , , The Top Averaging Group for the CDF and D0 Collaborations, prepr . Science hep-ex/0110059 Comput. Phys. Commun. hep-ph/0005309 , , Phys. Rev. Lett. , et al. et al. et al. et al. et al. et al. et al. FERMILAB-TM-2084. H. Ruiz, these proceedings. DELPHI Collaboration, DELPHI 2001-103L3 CONF Collaboration, 531; L3 NoteOPAL 2637; Collaboration, OPAL Physics NotesH. Ruiz, PN422 these and proceedings. PN480; M.G. Kozlov, S.G. Porsev and I.I. Tupitsyn, A. Derevianko, G. Passarino, in S.C. Bennett and C.E. Wieman, LEPEWWG/XSEC/2001-03; H. Rick, these proceedings. by C.Lim and T.Yamanaka. . G¨nwl andM. Gr¨unewald G. Passarino, K. McFarland for the NuTeV Collaboration, [54] A. Freitas, W. Hollik, W. Walter, G. Weiglein, [55] See, for example, G. Chiarelli, these proceedings. [53] L. Demortier [35] L3 Collaboration, L3 Note[36] 2683. D. Duchesneau, these proceedings. [37] DELPHI Collaboration, DELPHI 2001-060[38] CONF 488. O. Pooth, these proceedings. [39] S.V. Chekanov, E.A. de Wolf and W. Kittel, [33] ALEPH Collaboration, ALEPH 2001-020 CONF 2001-017; [34] The LEP Collaborations and the LEP W Working Group, note LEPEW International Europhysics Conference on HEP [45] A. Oh, these proceedings. [46] F. Piccinini, these proceedings; M.[47] Biglietti, these D.Y. proceedings. Bardin [48] G. Montagna [42] S. Villa, these proceedings. [43] The LEP Collaborations and the LEP WW Working Group,[44] note S. Jadach, W. Placzek and B.F.L. Ward, [40] See, for example, S. Jezequel, in [41] S. Jadach [49] CERN Yellow Report 95-03, eds. D. Bardin, W. Hollik and G. Passar [50] K. McFarland [51] G.P. Zeller [52] C.S. Wood