Theory Perspectives

Goran Senjanovic ICTP

talks by Altarelli, Djouadi, Fayet, Nesti,...

Saturday, October 9, 2010 Message:

NO theory that predicts new physics at LHC energies Connected with NO problem in the SM (except neutrino mass -but that can be higher energy)

Thank you !

Saturday, October 9, 2010 Well, I mean...

SM: in spite of great success No Higgs yet

LHC is a Higgs machine

One could wait to see if it exists...

Saturday, October 9, 2010 instead, one imagines it is there

then ask: why mH MGUT (MPl) ? ￿

Funny question, • GUT never seen since: • M Pl not a physical scale

M 1/ G 1019GeV Pl ≡ N ￿ ￿

Saturday, October 9, 2010 g2 Maybe GN = 2 (g = MF /MPl) MF

g 1 MF MPl Glashow, ‘85 ￿ ⇒ ￿ Realization: Large Extra Dimensions (LED) 2 2+n n n/2 M = M R g =(M R)− Pl F ￿ F 1 1 g 1 R M − (TeV)− ￿ ￿ F ∼ Arkani-Hamed⇐, Dimopoulos, Dvali (ADD), ‘98

Saturday, October 9, 2010 Large number of species 2 n MPl # of states : N =(MF R) = M ￿ F ￿ 1 2 3 N , , ,... M the tower: R R R R ￿ F

32 MF TeV N 10 ￿ ⇒ ￿ Dvali, ’07 - ’10 MPl all that matters : large # of species MF ￿ √N MF the scale of strong gravity

Saturday, October 9, 2010 Large number of species 2 n MPl # of states : N =(MF R) = M ￿ F ￿ 1 2 3 N , , ,... M the tower: R R R R ￿ F

32 MF TeV N 10 ￿ ⇒ ￿ Dvali, ’07 - ’10 MPl all that matters : large # of species MF ￿ √N MF the scale of strong gravity

Saturday, October 9, 2010 Black holes @ LHC ? M TeV F ￿ ADD, ‘98

no hierarchy problem

Physics of black holes not well understood: how to distinguish from particles ? Dvali, Gomez, Mukhanov ’10

Saturday, October 9, 2010 but the question was:

Why is Higgs light?

Saturday, October 9, 2010 Hierarchy problem: SUSY@LHC ? talk by Fayet t y2 δm2 = t Λ2 + m2 H H H 16π2 t yt yt ￿ ￿ t M ,M + GUT Pl t˜ y2 δm2 = t Λ2 + m2 H H H −16π2 t˜ 2 2 ￿ ￿ yt y δm2 = t m2 m2 H −16π2 t˜ − t Maiani; Fayet;￿ Witten ’79￿

Saturday, October 9, 2010 large cutoff: Λ 1016 GeV ≥

low energy supersymmetry tailor fit for GUT

Saturday, October 9, 2010 m˜ TeV t ≤ y2 δm2 = t m2 m2 H −16π2 t˜ − t ￿ ￿ small

2 δmH < 0 Higgs mechanism y 1 ⇒ for t ￿

Alvarez-Gaume, Polchinski, Wise, ‘82 Inoue, Kakuto, Komatsu, Takeshita, ‘82

Saturday, October 9, 2010 Low energy supersymmetry Unification of gauge couplings

Ibáñez , Ross, ’80 Dimopoulos, Rabi, Wilczek, ’80 Einhorn, Jones ’81 sin2θ 0.23 * W ￿ Marciano, G.S., ’81 *

needed m 200GeV t ￿ 2 2 α mt mb ρ 1+ −2 ￿ 2π MW

(sin2θ ) 0.21 In order to boost W exp ￿

Saturday, October 9, 2010 The light Higgs mass in the MSSM:

4 2 2 2 3α mt mt˜ mh0 MZ + 2 ln 2 +3 ≤ 4π MW ￿ mt ￿

mt˜ TeV mh0 135 GeV ￿ ⇒ ≤ talk by Altarelli

Saturday, October 9, 2010 Electro-weak baryogenesis:

needs a light stop, lighter than a top

neutrino mass:

R-parity violating couplings

dark matter: or stable neutralino long lived gravitino new physics of neutrino mass

Saturday, October 9, 2010 R-parity and neutrino mass

￿￿ec + q￿dc + ucdcdc product small

neutrino mass proton decay all vanish (symmetry)

add νc neutrino massless ￿hνc symmetry?

Saturday, October 9, 2010 Neutralino DM?

not so convincing in MSSM: symmetry no guarantee for vanishing couplings

gravitino necessarily long lived, DM for m 10 100 GeV 3/2 ￿ −

Saturday, October 9, 2010 Is this convincing ?

SUSY @ LHC ?

Saturday, October 9, 2010 In Grand Unification 2 2 2 2 m 0 (tree) = m + M M there is fine tuning: h − 0 GUT ￿ W only loops are OK

If fine-tuning is a sin, SUSY helps you to sin only once - and at tree level

There are solutions, but more like exercises in Group Theory

Comment by Carl Sagan: A. Ozpinaci ’10

Saturday, October 9, 2010 Saturday, October 9, 2010 “...I can’t see a thing on the surface of Venus. Why not? Because it’s covered with a dense layer of clouds. Well, what are clouds made of? Water, of course. Therefore Venus must have an awful lot of water on it, therefore the surface must be wet. If the surface is wet there’s probably a swamp, if there’s a swamp there’s ferns, if there’s ferns... maybe there’s even dinosaurs. Observation: you couldn’t see a thing. Conclusion: Dinosaurs “

Saturday, October 9, 2010 Is our motivation somewhat metaphysical?

We have seen nothing : No Higgs No new physics

...and yet we speculate on for every particle a superpartner the end of field theory at TeV: black holes and such at LHC

Saturday, October 9, 2010 Well, there is new physics :

Neutrino oscillations

Neutrino masses and mixings

touches into the heart of an old are neutrinos massive and fundamental question: and `real’ particles?

Majorana, ’37

Saturday, October 9, 2010 Well, there is new physics :

Neutrino oscillations

Neutrino masses and mixings

touches into the heart of an old are neutrinos massive and fundamental question: and `real’ particles?

Majorana, ’37

Saturday, October 9, 2010 Well, there is new physics :

Neutrino oscillations

Neutrino masses and mixings

touches into the heart of an old are neutrinos massive and fundamental question: and `real’ particles?

Majorana, ’37 last paper before his disappearance

Saturday, October 9, 2010 The Majorana Program:

M νM = νL + νL∗ m (νLνL + h.c.) ⇔ ν ∆L =2 violation of Lepton number ⇒

neutrinoless double-beta decay (0ν2β)

Majorana, ’37 Racah, ’37 - Furry, ’38

Saturday, October 9, 2010 Double-beta decay

76Ge 76As + e +¯ν ￿→ e Göppert-Mayer, ’35 76Ge 76Se + e + e +¯ν +¯ν → e e n p

W e

νe

νe e

W n p

Saturday, October 9, 2010 Double-beta decay

76Ge 76As + e +¯ν ￿→ e Göppert-Mayer, ’35 76Ge 76Se + e + e +¯ν +¯ν → e e n p

W electrons created e out of “nothing”

νe 76 76 M Ge Se + e + e mν → ⊗ νe e 24 M t1/2 10 yr mν ￿ 1 eV W ≥ n p ⇒

Saturday, October 9, 2010 Why is this relevant for LHC ?

Majorana mass forbidden in the SM

Window to new physics Conventional wisdom: add νR see-saw

νL 0 mD ν R mD MR ⇒ ￿ ￿ M m R ￿ D

Saturday, October 9, 2010 Why is this relevant for LHC ?

Majorana mass forbidden in the SM

Window to new physics Conventional wisdom: add νR see-saw

2 νL 0 mD mD mν ν R mD MR ⇒ ￿−MR ￿ ￿ M m R ￿ D Majorana mass

Saturday, October 9, 2010 Why ν R ?

Saturday, October 9, 2010 Left - Right symmetry Pati, Salam ‘ 74 SU(2) U(1) SU(2) Mohapatra, G.S. ’75 L × × R talk by Nesti νL νR ⇒ SM limit 2 mν MW m m /M R ∝ R ν ∝ D WR 0 ⇒ →MWR →∞

neutrino Parity Minkowski ’77 mass violation Mohapatra, G.S. ’79

Saturday, October 9, 2010 νR 3 mν 1eV MWR 10 GeV νL ≤ ≥

see-saw mechanism

Minimal model:

theoretical limit MWR 2500 GeV ≥ Beall, Bander, Soni ’81 Maiezza, Nemevsek, Nesti, G.S. ‘10

Saturday, October 9, 2010 New source for 0ν2β Mohapatra, GS ’81

n p

WL e

νe

LL mν ⊗ νe e

WL n p

1 m LL ν M 4 p2 ∝ WL p 100MeV ￿

Saturday, October 9, 2010 New source for 0ν2β Mohapatra, GS ’81

n p n p

W L WR e e

νe Ne LL mν + RR mN ⊗ ν ⊗ e Ne e e

W W L R n p n p

1 mν 1 1 LL RR 4 4 2 ∝ M m M p WR N ∝ WL p 100MeV ￿

Saturday, October 9, 2010 New source for 0ν2β Mohapatra, GS ’81

n p n p

W L WR e e

νe Ne LL mν + RR mN ⊗ ν ⊗ e Ne e e

W W L R n p n p

1 1 1 mν RR LL RR 4 4 2 O(1) ∝ M m M p LL ￿ WR N ∝ WL M m 10M WR ￿ N ￿ WL p 100MeV m 1 eV ￿ ν ￿

Saturday, October 9, 2010 d u¯

WR e

Ne

mN ⊗ Ne e

W d¯ R u

Saturday, October 9, 2010 u¯ e

W R d

e N e

e N N m ⊗ u W R

¯d

Saturday, October 9, 2010 e

e

¯

u u

e

e

R

R

N

N

W

W

⊗

N

m

d

¯

d

Saturday, October 9, 2010 e e

u¯ u

WR Ne Ne WR

⊗

mN d d¯

Saturday, October 9, 2010 WR production @ colliders

e e (anti) proton jet u¯ u

WR Ne Ne WR

⊗

mN d d¯ proton jet

• Parity restoration • same-sign dileptons + jets Keung, G.S. ’83

Saturday, October 9, 2010 # of events as a function of energy (GeV) for L = 8fb−1 talk by Nesti MR (TeV): 1.8; 2, 0; 2.4; 2.6; 3, 0; 3.4

Saturday, October 9, 2010 Spectacular signatures

BUT

Scale not predicted

Typical of most Beyond Standard Model physics

Saturday, October 9, 2010 Example of a predictive theory

SU(5) grand unified theory: minimal Georgi, Glashow ‘74

• massless neutrinos • no unification

talk by Doršner

Saturday, October 9, 2010 Simple predictive extension: add 24F G. Senjanovi´c Bajc, GS ‘06 • one ν R one massless Seesaw at LHC • one fermion triplet - light neutrino

+ 0 (T ,T ,T−): weak triplet

l

YT j mT

j W − + d W j T 0 Bajc, Nemevšek, GS ‘07

YT

l

Planck 2010 23 Saturday, October 9, 2010 @ LHC: triplet decays through Yukawas probe of neutrino masses and mixings

FIG. 10: Normalized branching versus Majorana phase for NH (left) and IH (right). Im(z) 2. ≥ Arhrib, Bajc, Ghosh, Han, Huang, Puljak, G.S. ’09

Saturday, October 9, 2010

FIG. 11: Normalized branching versus Majorana phases for NH (left) and IH (right). Im(z)=1.

E. Determining the leptonic mixing matrix

The message of the above discussion is that while one cannot make predictions yet for the various branching fractions, the collider signatures can shed light on the lepton mixing

parameters. The theory in question has only two real parameters on top of the UPMNS: Re(z)andIm(z). Since we can measure in principle two branching fractions and the total

lifetime, one can get information on the yet unknown mixing angle θ13 and the Dirac and

17 Message

LHC: Higgs Hunter Machine

can probe the origin of neutrino mass

Saturday, October 9, 2010 Still, are we seeing dinosaurs ? lots of important physics within SM - as discussed amply at LHC days

• how many generations? • limit on Higgs mass? • Higgs structure: how many doublets?

until a few years ago PDG claimed no new families from high precision: S, T, U

Saturday, October 9, 2010 strong impact on the Higgs

high precision physics (& direct search}:

upper limit on the Higgs mass mh ￿ 180 GeV

talk by Djouadi

Saturday, October 9, 2010 Fourth generation? talk by Dorigo

m4 500 GeV perturbativity limit ￿ ⇒ 700 GeV ? Marciano, Valencia, Willenbrock ’89

parameter set mu4 md4 mH ∆Stot ∆Ttot 0.4 (a) 310 260 115 0.15 0.19 U = 0 (b) 320 260 200 0.19 0.20 LHC (c) 330 260 300 0.21 0.22 0.3 (d) 400 350 115 0.15 0.19 (e) 400 340 200 0.19 0.20 direct0.2 CDF limits: (a) (f) 400 325 300 0.21 0.25 m = 115 GeV m40.1 300h GeV ? ! ≥ TABLE I: Examples of the total contributions to ∆S and Hung and Sher ’07 ∆T from a fourth generation. Kribs, The et leptonal ’07 masses are fixed T ? m m S -0 to ν4 =100GeVand "4 =155GeV,giving∆ ν" = Flacco et al ’10 ! (b) (f) 0.00 and ∆Tν" =0.05. The best fit to data is (S, T )= (0.06, 0.11) [28]. The Standard Model is normalized to (0, 0) Saturday, October 9, 2010 -0.1 for mt =170.9GeVandmH =115GeV.Allpointsarewithin m = 200 GeV the 68% CL contour defined by the LEP EWWG [28]. h m = 300 GeV -0.2 h

mh = 1 TeV fer slightly between each group, presumably due to slight -0.3 updates of data (the S-T plot generated by the 2006 -0.2 -0.1 0 0.1 0.2 0.3 LEP EWWG is one year newer than the plot included S in the 2006 PDG). A larger difference concerns the use of the Z partial widths and σh.TheLEPEWWGad- vocate using just Γ ,sinceitisinsensitivetoα .This ! s FIG. 2: The 68% and 95% CL constraints on the (S, T )pa- leads to a flatter constraint in the S-T plane. The PDG rameters obtained by the LEP Electroweak Working Group include the αs-sensitive quantities ΓZ , σh, Rq as well as [27, 28]. The shift in (S, T )resultingfromincreasingthe R!,andobtainalessflat,moreoval-shapedconstraint. Higgs mass is shown in red. The shifts in ∆S and ∆T from a Additional lower–energy data can also be used to (much fourth generation with several of the parameter sets given in more weakly) constrain S and T ,althoughtherearesys- Table I are shown in blue. tematic uncertainties (and some persistent discrepancies in the measurements themselves). The LEP EWWG do not include lower–energy data in their fit, whereas the contribution to the electroweak parameters with a Majo- PDG appear to include some of it. In light of these sub- rana mass. Given the current direct–search bounds from tleties, we choose to use the LEP EWWG results when LEP II on unstable neutral and charged leptons, we find quoting levels of confidence of our calculated shifts in the aMajoranamassisunfortunatelynotparticularlyhelp- S-T plane. We remind the reader, however, that the ac- ful in significantly lowering S.AMajoranamassdoes, however, enlarge the parameter space where S 0. For tual level of confidence is obviously a sensitive function ! of the precise nature of the fit to electroweak data. example, given the lepton Dirac and Majorana masses (mD,M44)=(141, 100) GeV, the lepton mass eigen- In Table I we provide several examples of fourth– states are (mν1 ,mν2 ,m!)=(100, 200, 200) GeV, and con- generation fermion masses which yield contributions to tributions to the oblique parameters of (∆Sν , ∆Tν )= the oblique parameters that are within the 68% CL el- (0.01, 0.04). It is difficult to find parameter regions with ∆S < 0withouteithercontributingto∆U ∆S , lipse of the electroweak precision constraints. We illus- ! ! !− ! trate the effect of increasing Higgs mass with compen- contributing significantly more to ∆T!,ortakingmν1 < sating contributions from a fourth generation in Fig. 2. 100 GeV which violates the LEP II bound for unstable More precisely, the fit to electroweak data is in agree- neutrinos. ment with the existence of a fourth generation and a light Higgs about as well as the fit to the Standard Model alone Let us summarize our results thus far. We have with mH =115GeV.Usingsuitablecontributionsfrom identified a region of fourth–generation parameter space the fourth–generation quarks, heavier Higgs masses up in agreement with all experimental constraints and to 315 GeV remain in agreement with the 68% CL limits with minimal contributions to the electroweak precision derived from electroweak data. Heavier Higgs masses up oblique parameters. This parameter space is character- to 750 GeV are permitted if the agreement with data is ized by relaxed to the 95% CL limits. m m 30 60 GeV !4 − ν4 ! − Until now we have focused on purely Dirac neutri- 1 mH mu4 md4 1+ ln 50 GeV nos. However, there is also a possible reduction of Stot − ! ! 5 115 GeV" × when the fourth–generation neutrino has a Majorana V , V ! 0.04 mass comparable to the Dirac mass [29, 30]. Using the | ud4 | | u4d| U 4 , U 4 ! 0.02 , (9) exact one-loop expressions of Ref. [30], we calculated the | e | | µ |

4 0.4 Kribs, et al ’07 U = 0

0.3

0.2 heavier Higgs OK (a)

m = 115 GeV 0.1 h

T -0 (b) (f) 315 (750) GeV

-0.1 @68(95)% CL

mh = 200 GeV m = 300 GeV -0.2 h changes: mh = 1 TeV

-0.3 production, -0.2 -0.1 0 0.1 0.2 0.3 S decay rates

Saturday, October 9, 2010 more on 4th

• detailed study of masses and mixings Eberhardt, Lenz, Rohrwild ’10

• CP Eilam, Melic, Trampetic ’09

•hierarchy problem Hung, Xiong ’10

Saturday, October 9, 2010 new limits

gluon fusion heavy quark loops strongly affected ⇐ recent Tevatron CDF & D0 ’10

excludes the region: 131 GeV ￿ mh ￿ 204 GeV @95% CL

Saturday, October 9, 2010 MSSM? Dawson, Jaiswal ’10

• the mass of d4 tanβ 1 (perturbativity) ⇒ ￿ •Higgs mass limit dramatically changed heavy quark

4 2 2 2 3α mt mt˜ mh0 MZ + 2 ln 2 +3 ≤ 4π MW ￿ mt ￿

Saturday, October 9, 2010 Dawson, Jaiswal ’10 Carpenter, tan ! = 1 m =250 GeV, m =230 GeV e’ "’ Rajaraman, 1500 Whiteson, Thursday

1000 e4 250 GeV [GeV] h,H M LHC@7 TeV 500 Mh M (M =300 GeV) 1 H A 1 ftp MH (MA=1 TeV) −

0 (current around 300 350 400 450 500 550 600 m = m [GeV] t’ b’ 100 GeV)

Saturday, October 9, 2010 Mirror families? restore parity Lee, Yang ’56

ν e e R ￿ ￿L

u u d d R R ￿ ￿L

Saturday, October 9, 2010 Mirror families? restore parity Lee, Yang ’56

ν N e e R EL E ￿ ￿L ￿ ￿R

u U u d D U d R R L L D ￿ ￿L ￿ ￿R

Saturday, October 9, 2010 • gauge B, L - required to cancel anomalies

• Kaluza-Klein theories • N=2 supersymmetry • SO(10+2N) unification

perfectly OK - if two Higgs

He, Polonsky, Su ’01 update?

Saturday, October 9, 2010 Message experimentalist’s task:

hard to see a black cat in a dark room, ...especially if it is not there

physics not only: your turn why we are here, why three dimensions, why are numbers what they are ...

Saturday, October 9, 2010