Hunting the Last Missing Particle of the Standard Model Shufang Su • Caltech

Particles and Forces Building blocks of matter -- elementary particles smaller distance : higher energy Fundamental interactions Gravity Electromagnetic force Weak interaction nuclear -decay, burning of the sun … Strong interaction -decay, holds proton and neutron … forces ? S. Su U. Arizona - Colloquium

Exp Discovery and Theory Development - c b t 1 GeV = 109 eV=1.8x10-24 g  p n  Z W s d Electromagnetic  Weak interaction Z,W Strong interaction g Standard Model u e mass (GeV) e    g theory S. Su U. Arizona - Colloquium

Standard Model mW=80 GeV mZ=91 GeV Simply impose mass - mW=80 GeV mZ=91 GeV Simply impose mass  theory not self-consistent Create mass for “gauge boson”  predict a Higgs particle However, we have not find this particle yet … Is there anything missing ? S. Su U. Arizona - Colloquium

Outline prediction  evidence confirmation establishment - prediction  evidence confirmation establishment Why need a Higgs ? How to search the Higgs ? Is it really a (Standard Model) Higgs ? How to probe new physics using Higgs study ? S. Su U. Arizona - Colloquium

Why need a Higgs ? S. Su U. Arizona - Colloquium

Electroweak Symmetry Breaking - EM Photon  m=0 Weak W+,W- Z mW=80 GeV mZ=91 GeV 2x10-18 m Begin with a unified theory of EM and weak interaction We want something that not disturb electromagnetic force make weak interaction short-range Higgs mechanism P.W. Higgs (1964, 1966) Weinberg(1967), Salam (1968) Universe filled with background Higgs field Particle get mass via interaction with the background Higgs field How to give mass to W and Z boson ? How to give mass to quarks and leptons ? S. Su U. Arizona - Colloquium

Higgs Mechanism (Particle Physics) - Potential V= - m2 H2 + ½  H4 left-over degree of freedom  physical Higgs particle minimize the potential mHSM2 v2  (100 GeV)2 H0=v Higgs degree of freedom eaten by W and Z  longitudinal modes  W ,Z obtain mass W,Z mass W H g X H0=v mW  gv  v=246 GeV gauge transformation S. Su U. Arizona - Colloquium

Higgs Property However, Higgs is still missing ... Go look for it! - Advantage of Higgs mechanism quark and lepton mass SM (with Higgs) agrees well with experiments f H y X H0=v mf  y v Higgs property v=246 GeV CP even scalar coupling  mass fermion mf/v gauge boson mW/v , mZ/v mass : mHSM2 v2  (100 GeV)2 mass not predicted Other model: composite Higgs hard to fit with experimental data hard to build model However, Higgs is still missing ... Go look for it! S. Su U. Arizona - Colloquium

Theoretical Constraint on mHSM - V= - m2 H2 + ½  H4 mH2= v2 K. Riesselmann (1997) 105 GeV (ytyt  … Landau pole  = Mpl  1019 GeV 130 GeV < mH < 180 GeV 116 GeV potential unbounded from below SM valid up to scale  S. Su U. Arizona - Colloquium

Indirect Constraint from Electroweak Data - indirect direct without NuTeV LEP EWWG indirect bounds: mt= 171-9 GeV direct search: mt=174.3  5.1 GeV +11 mHSM=81+52 GeV mHSM<193 GeV at 95% C.L. -33 S. Su U. Arizona - Colloquium

How to search the Higgs ? Decay right after it is produced does not exist in nature anymore produced it at high-energy colliders look for its decay products at detectors S. Su U. Arizona - Colloquium

Higgs Decay (SM) mHSM (GeV) mHSM  135 GeV mHSM  135 GeV - mHSM  135 GeV mHSM  135 GeV Branching ratio gold-plated mode for LHC seaches: Ze+e- / +- BrHSM =  (HSM  final state)  (HSM  everything) mHSM (GeV) M. Spira (1998) S. Su U. Arizona - Colloquium

LEP Search : Current mHSM Limit - Large Electron Positron Collider (CERN) Ecm  189 GeV 2461 Pb-1 Ecm  206 GeV 536 Pb-1 1 pb= 10-12 b; 1b=10-28 m2 e- e+ four jets Hbb, Zqq missing energy Hbb, Z leptonic Hbb, Zll tau lepton Hbb, Z H, Zqq e+e- ZHSM Add plot possible signal mHSM  116 GeV signal+background 37% C.L. background 8% C.L. exclusion bound mHSM  114.4 GeV 95% C.L. S. Su U. Arizona - Colloquium

Higgs Prodcution at Tevatron (Run II) - - Tevatron (Fermilab) pp collider CDF, D0 / Ecm = 2 TeV L= 2 fb-1 / year events/year 2x104 huge background W,Z  leptons mHSM  135 GeV HSM  bb mHSM  135 GeV HSM  W+W- cross section (pb) 2x102 2 M. Spira (1998) S. Su U. Arizona - Colloquium

Higgs Search at Tevatron (Run II) - Tevatron (Fermilab) Ecm = 2 TeV, L= 2 fb-1 / year If no Higgs is found 95% C.L. exclusion limit (15 year) (5 year) (1 year) Run II Higgs working group S. Su U. Arizona - Colloquium

Higgs Search at Tevatron (Run II) - Tevatron (Fermilab) Ecm = 2 TeV, L= 2 fb-1 / year Discovery reach (15 year) 130 20 fb-1 (5 year) (1 year) Run II Higgs working group S. Su U. Arizona - Colloquium

Higgs Producction at LHC - Large Hadron Collider (CERN) pp ATLAS, CMS events/year Ecm = 14 TeV L= 10 fb-1 / year 102 106 mHSM  135 GeV HSM   mHSM  135 GeV HSM  W+W-, ZZ ggH 10 p 1 104 cross section (pb) HSM  , , W+W-, ZZ 120 GeV HSM  180 GeV 10-1 10-2 102 10-3 M. Spira (1998) 10-4 1 mHSM (GeV) S. Su U. Arizona - Colloquium

Higgs Search at LHC Large Hadron Collider (CERN) pp - Large Hadron Collider (CERN) pp L=10 fb-1 / year ggH ggHtt 5  cover entire Higgs mass region of SM with more than 5  significance. CMS, ATLAS (2002) S. Su U. Arizona - Colloquium

Need precise study of Higgs properties at a e+e- collider If we see something at LHC looks like a Higgs … Is it really a Higgs ? Is it the Standard Model Higgs ? Need precise study of Higgs properties at a e+e- collider basic properties: mass, width, spin and CP quantum number origin of particle mass  Higgs coupling  particle mass reconstruct Higgs potential: Higgs self-coupling S. Su U. Arizona - Colloquium

Higgs Prodcution at LC Linear Collider e+e- clean environment Ecm = 500 GeV / 1 TeV ; L= 500 / 1000 fb-1 / year H HZ H cross section (fb) HZ Hee Hee mHSM (GeV) LC source book copiously produced, thousands of events S. Su U. Arizona - Colloquium

Higgs Mass, Decay Width and JPC - Miller et. al. (2001) Garcia et al. (2001) Higgs mass: mHSM = 40 MeV reconstruct Higgs in ZH production compare with indirect bounds from global fit e+ e- Z H Higgs decay width: HSM/ HSM = 6% HSM =  (HSM  W+W-) Br (HSM  W+W-) Higgs production H Higgs decay HSM  W+W- e+e-  Z final state angular distribution angular and polarization asymmetry S. Su U. Arizona - Colloquium

Higgs Coupling mHSM  150 GeV Higgs decay branching ratio - mHSM  150 GeV Higgs decay branching ratio Higgs production cross section mHSM  150 GeV HSM  cc, gg,  too small HSM  W+W-,ZZ precisely measured HSM  bb precision reduced when mHSM  200 GeV HSM  tt possible when mHSM  2 mt reconstruct Higgs potential v Carena et. Al. (2002) mHSM = 120 GeV S. Su U. Arizona - Colloquium

Photon Collider e+e-collider operating in  mode Ecm=0.8 Ecmee measure  (HSM  )  bb  (HSM  ) Br(HSM  bb) sensitive to heavy states Higgs decay width HSM =  (HSM  ) / Br(HSM   ) mHSM  200 GeV , directly measure HSM photon polarization  CP quantum number every particle (get mass from Higgs) contributes S. Su U. Arizona - Colloquium

There must be new physics beyond minimal Standard Model If we find deviation from Standard Model prediction … What can we learn ? There must be new physics beyond minimal Standard Model What is it ? How to probe it using Higgs study ? S. Su U. Arizona - Colloquium

What New Physics ? Minimal Supersymmetric Standard Model (MSSM) - SM is an effective theory below some energy scale  Hierarchy problem: MEW100 GeV , Mplank 1019 GeV ? Naturalness problem: mass of a fundamental scalar (like Higgs) receive huge quantum corrections: (mH2)physical  (mH2)0 + 2 (100 GeV)2 H - 2 H -(1019 GeV)2 precise cancellation up to 1034 order (1019 GeV)2 Supersymmetry SM particle superpartner Spin differ by 1/2 Minimal Supersymmetric Standard Model (MSSM) S. Su U. Arizona - Colloquium

Higgs Sector in MSSM CP-even Higgs h0 decoupling limit: mA0  mZ h0 similar to SM Higgs h0 mass tree level: mh0mZ loop corrections: mh0 135 GeV SM MSSM HSM Hd, Hu HSM0=v v=246 GeV Hd0=v1 ,Hu0=v2 v2=v12 +v22 tan=v2/v1  H4 g12+g22 (mHSM2 v2) h0 (mh0) H0 ,A0 ,H (mA0) gauge coupling SM Higgs searches at low mass region could be applied to the light MSSM Higgs h0 MSSM Higgs sector determined by tan and mA0 S. Su U. Arizona - Colloquium

LEP Search Limit (MSSM) - e+e- Zh0 e+e- A0h0 cos2(-eff)  sin2(-eff) A0h0 mA0  91.9 GeV mh0  91.0 GeV Zh0 0.5  tan  2.4 S. Su U. Arizona - Colloquium

Bounds on mA0 From Higgs Coupling Measurements -  Br(HW+W-)=5% mA0 controls the degree of decoupling h0 coupling mZ2 HSM coupling mA02 -1  mA0  mZ decoupling region no deviation mA0  650-800 GeV non-zero deviation  constraints on mA0 Carena et. al. (2002) S. Su U. Arizona - Colloquium

Three SUSY Breaking Scenarios - supersymmetry must be broken electron: m=0.511 MeV, no scalar-electron MSSM: 105 new SUSY breaking parameters out of control mechanism for SUSY breaking: (flavor blind) greatly reduce SUSY parameters low energy MSSM (visible sector) 105 parameters SUSY-breaking (hidden sector) a few parameters gravity gravity-mediated SUSY breaking (SUGRA) gauge-mediated SUSY breaking (GMSB) gauge interaction anomaly-mediated SUSY breaking (AMSB) anomaly something S. Su U. Arizona - Colloquium

Distinguish SUSY Breaking Scenario - LEP search bound Dedes, Heinemeyer, SS, weiglein (2001, 2002) MSSM SUGRA GMSB AMSB mh0max (GeV) 135 127 123 125 tanmin 0.5 or 2.4 2.9 3.1 3.8 deviation from SM Higgs coupling  constrains on mA0 mA0  500 GeV mA0  1000 GeV S. Su U. Arizona - Colloquium

GMSB and AMSB mA0  1300 GeV mA0  1100 GeV S. Su - mA0  1300 GeV mA0  1100 GeV S. Su U. Arizona - Colloquium

Can we distinguish various SUSY breaking scenario? Distinguish SUSY Breaking Scenario - 500 GeV  mA0  600 GeV , tan  30 AMSB if we know ranges of mA0, tan from LHC if we see deviations of coupling at LC Can we distinguish various SUSY breaking scenario? GMSB SUGRA S. Su U. Arizona - Colloquium

Conclusion Why need a Higgs ? - Why need a Higgs ? How to search the Higgs ? Is it really a (Standard Model) Higgs ? How to probe new physics using Higgs study ? Higgs mechanism provides a simple and elegant way to explain the origin of the mass Tevatron Run II exclude Higgs up to 180 GeV (10 fb-1) LHC would find the Higgs if it is there detail study at Linear Collider measure Higgs mass, decay width, coupling… at high precision Minimal Supersymmetric Standard Model (MSSM) constrain parameter space (mA0) distinguish various SUSY breaking scenarios Heavy Higgs search S. Su U. Arizona - Colloquium

The hunting is continuing … Tevatron p LHC p - p 2007-- Now -- S. Su U. Arizona - Colloquium