Hunting the Last Missing Particle of the Standard Model
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Transcript of Hunting the Last Missing Particle of the Standard Model
Hunting the Last Missing Particle of the Standard Model
Hunting the Last Missing Particle of the Standard Model
Shufang Su • CaltechShufang Su • CaltechShufang Su • CaltechShufang Su • Caltech
S. Su U. Arizona - Colloquium 2
Particles and Forces Particles and Forces
• Fundamental interactionsFundamental interactions – GravityGravity– Electromagnetic forceElectromagnetic force– Weak interaction Weak interaction nuclear nuclear -decay, burning of the sun …-decay, burning of the sun …– Strong interaction Strong interaction -decay, holds proton and neutron …-decay, holds proton and neutron …
forcesforces
• Building blocks of matter -- elementary particlesBuilding blocks of matter -- elementary particles
smaller distance : higher energysmaller distance : higher energy
??
S. Su U. Arizona - Colloquium 3
Exp Discovery and Theory Development
Exp Discovery and Theory Development
e
ma
ss (
Ge
V) e
u
sd
c
bt
ZW
g
1 GeV = 109 eV=1.8x10-24 g
pp nn
theorytheory
• Electromagnetic Electromagnetic • Weak interaction Weak interaction Z,WZ,W
• Strong interaction Strong interaction gg
Standard ModelStandard Model
S. Su U. Arizona - Colloquium 4
Standard Model Standard Model
mmWW=80 GeV m=80 GeV mZZ=91 =91 GeVGeV
Is there anything Is there anything missing ?missing ?
Simply impose massSimply impose mass
theory not self-theory not self-consistentconsistent
Create mass for “gauge Create mass for “gauge boson”boson”
predict a predict a HiggsHiggs particle particleHowever, we have not However, we have not find this particle yet …find this particle yet …
S. Su U. Arizona - Colloquium 5
Outline Outline
• Why need a Higgs ? Why need a Higgs ?
• How to search the Higgs ?How to search the Higgs ?
• Is it really a (Standard Model) Higgs ? Is it really a (Standard Model) Higgs ?
• How to probe new physics using Higgs How to probe new physics using Higgs
study ?study ?
prediction prediction
evidenceevidence
confirmation confirmation
establishmentestablishment
S. Su U. Arizona - Colloquium 6
Why need a Higgs ? Why need a Higgs ?
S. Su U. Arizona - Colloquium 7
Electroweak Symmetry Breaking Electroweak Symmetry Breaking
EMEM Photon Photon
m=0m=0
WeakWeak WW++,W,W--
ZZmmWW=80 =80 GeVGeV
mmZZ=91 GeV=91 GeVBegin with a unified theory of EM and weak interactionBegin with a unified theory of EM and weak interaction
We want something thatWe want something that not disturb electromagnetic forcenot disturb electromagnetic force make weak interaction short-rangemake weak interaction short-range
• How to give mass to W and Z boson ? How to give mass to W and Z boson ? • How to give mass to quarks and leptons ?How to give mass to quarks and leptons ?
2x102x10-18-18 m m
Higgs mechanismHiggs mechanism• P.W. Higgs (1964, 1966)• Weinberg(1967), Salam (1968)
• Universe filled with Universe filled with backgroundbackground Higgs fieldHiggs field• Particle get mass via Particle get mass via interactioninteraction with the background Higgs with the background Higgs fieldfield
S. Su U. Arizona - Colloquium 10
Higgs Mechanism (Particle Physics) Higgs Mechanism (Particle Physics)
HiggsHiggs
Potential Potential V= - mV= - m22 H H22 + ½ + ½ H H44
HH00=v=v left-over degree of freedomleft-over degree of freedom physical Higgs particlephysical Higgs particle
minimize the potential minimize the potential mmHSMHSM
22 vv2 2 (100 GeV) (100 GeV)22
gauge transformationgauge transformation
degree of freedom eaten bydegree of freedom eaten byWW and Z and Z longitudinal modeslongitudinal modes WW ,Z obtain mass ,Z obtain mass
WW,Z mass,Z mass
WW
WW
HHgg
XXHH00=v=v
mmW W gv gv v=246 GeVv=246 GeV
S. Su U. Arizona - Colloquium 11
Higgs Property Higgs Property
Advantage of Higgs mechanismAdvantage of Higgs mechanism
• quark and lepton massquark and lepton mass • SM (with Higgs) agrees well SM (with Higgs) agrees well with experiments with experiments
Other model:Other model: composite Higgscomposite Higgs
• hard to fit with hard to fit with experimental dataexperimental data• hard to build modelhard to build model
ff
ff
HHyy
XXHH00=v=v
mmf f y v y v
However, However, Higgs is still missing ...Higgs is still missing ...
Go look for it!Go look for it!
Higgs propertyHiggs property v=246 GeVv=246 GeV• CP even scalarCP even scalar• coupling coupling mass mass
- fermion fermion mmff/v/v - gauge boson gauge boson mmWW/v , m/v , mZZ/v/v
• mass : mass : mmHSMHSM22 vv2 2 (100 GeV) (100 GeV)22
mass not predictedmass not predicted
S. Su U. Arizona - Colloquium 13
Theoretical Constraint on mHSM Theoretical Constraint on mHSM
Landau poleLandau pole
potential unbounded from belowpotential unbounded from below
101055 GeV GeV
116 GeV116 GeV
SM valid up to scale SM valid up to scale
K. Riesselmann (1997) V= - mV= - m22 H H22 + ½ + ½ H H44
mmHH22= = vv22
= M= Mpl pl 10 101919 GeV GeV 130 GeV < m130 GeV < mHH < 180 GeV < 180 GeV
((yyttyytt
… …
S. Su U. Arizona - Colloquium 14
Indirect Constraint from Electroweak Data
Indirect Constraint from Electroweak Data
LEP EWWG
mmHSMHSM=81=81+52 +52 GeVGeV
mmHSMHSM<193 GeV at 95% C.L.<193 GeV at 95% C.L.-33-33
indirect bounds: mindirect bounds: mtt= 171= 171-9-9 GeV GeVdirect search: mdirect search: mtt=174.3 =174.3 5.1 GeV 5.1 GeV
+11+11
indirectdirect
without NuTeV
S. Su U. Arizona - Colloquium 15
How to search the Higgs ? How to search the Higgs ?
Decay right after it is producedDecay right after it is produced
does not exist in nature anymoredoes not exist in nature anymore produced it at high-energy collidersproduced it at high-energy colliders look for its decay products at detectorslook for its decay products at detectors
S. Su U. Arizona - Colloquium 16
Higgs Decay (SM) Higgs Decay (SM)
M. Spira (1998) mHSM (GeV)
gold-plated gold-plated mode for LHC mode for LHC seaches:seaches: ZZee++ee-- / / ++--
mmHSMHSM 135 GeV 135 GeV mmHSM HSM 135 GeV 135 GeV
Bra
nch
ing
rat
io
BrBrHSM HSM = = (H (HSMSM final state) final state)
(H(HSMSM everything) everything)
S. Su U. Arizona - Colloquium 18
LEP Search : Current mHSM Limit LEP Search : Current mHSM Limit
LLarge arge EElectron lectron PPositron Collider (ositron Collider (CERNCERN))
Ecm Ecm 189 GeV 189 GeV 2461 Pb2461 Pb-1-1
Ecm Ecm 206 GeV 206 GeV 536 Pb536 Pb-1-1
Add plotAdd plot
exclusion boundexclusion bound
mmHSMHSM 114.4 GeV 95% C.L. 114.4 GeV 95% C.L.
possible signal possible signal mmHSMHSM 116 GeV 116 GeV– signal+background 37% C.L.signal+background 37% C.L.– backgroundbackground 8% C.L.8% C.L.
ee--ee++
1 pb= 10-12 b; 1b=10-28 m2
ee++ee-- ZH ZHSMSMfour jets Hbb, Zqq
missing energy
Hbb, Z
leptonic Hbb, Zll
tau lepton Hbb, ZH, Zqq
S. Su U. Arizona - Colloquium 19
Higgs Prodcution at Tevatron (Run II) Higgs Prodcution at Tevatron (Run II)
Tevatron Tevatron (Fermilab) (Fermilab) pp collider pp collider CDF, D0CDF, D0
huge huge backgroundbackground
W,Z W,Z leptons leptons
mmHSM HSM 135 GeV 135 GeV
HHSMSM bb bb
mmHSMHSM 135 GeV 135 GeV
HHSMSM W W++WW--
Ecm = 2 TeVEcm = 2 TeV
L=L= 2 fb2 fb-1 -1 / year/ year
cros
s se
ctio
n (
pb)
events/year
2x104
2x102
2
M. Spira (1998)
-- //
S. Su U. Arizona - Colloquium 20
Higgs Search at Tevatron (Run II)
Higgs Search at Tevatron (Run II)
Tevatron Tevatron (Fermilab)(Fermilab) Ecm = 2 TeV, L= 2 fbEcm = 2 TeV, L= 2 fb-1-1 / year / year
Run II Higgs working group
(1 year)
(15 year)
(5 year)
If no Higgs is foundIf no Higgs is found95% C.L. exclusion limit95% C.L. exclusion limit
S. Su U. Arizona - Colloquium 21
Higgs Search at Tevatron (Run II) Higgs Search at Tevatron (Run II)
Tevatron Tevatron (Fermilab)(Fermilab) Ecm = 2 TeV, L= 2 fb-1 / yearEcm = 2 TeV, L= 2 fb-1 / year
Run II Higgs working group130130
20 fb20 fb-1-1
(1 year)
(5 year)
(15 year)
Discovery reachDiscovery reach
S. Su U. Arizona - Colloquium 22
Higgs Producction at LHC Higgs Producction at LHC
LLarge arge HHadron adron CCollider ollider (CERN) (CERN) pp pp ATLAS, CMSATLAS, CMSEcm = 14 TeVEcm = 14 TeV
L=L= 10 fb10 fb-1 -1 / year/ year
cros
s se
ctio
n (
pb)
mHSM (GeV)
ggH mmHSM HSM 135 GeV 135 GeV
HHSMSM
mmHSMHSM 135 GeV 135 GeV
HHSMSM W W++WW--, ZZ, ZZ
HHSMSM , , ,,WW++WW--, ZZ, ZZ
120 GeV120 GeV H HSMSM 180 180 GeVGeV
events/year
106
104
102
1M. Spira (1998)
pppp
102
10
10-4
10-3
10-2
10-1
1
S. Su U. Arizona - Colloquium 23
Higgs Search at LHC Higgs Search at LHC
LLarge arge HHadron adron CCollider ollider (CERN) (CERN) pppp
ggHggHtt
cover entire Higgs mass region of SM with cover entire Higgs mass region of SM with more than 5 more than 5 significance. significance.
L=10 fbL=10 fb-1 -1 / year/ year
CMS, ATLAS (2002)
5 5
S. Su U. Arizona - Colloquium 25
Need precise study of Higgs properties at a e+e- colliderNeed precise study of Higgs properties at a e+e- collider
• basic properties: basic properties: mass, width, spin and CP quantum mass, width, spin and CP quantum numbernumber
• origin of particle mass origin of particle mass Higgs coupling Higgs coupling particle particle massmass
• reconstruct Higgs potential: reconstruct Higgs potential: Higgs self-couplingHiggs self-coupling
Is it really a Higgs ? Is it really a Higgs ?
If we see something at LHC looks like a If we see something at LHC looks like a Higgs …Higgs …
Is it the Standard Model Higgs ?Is it the Standard Model Higgs ?
S. Su U. Arizona - Colloquium 27
Higgs Prodcution at LC Higgs Prodcution at LC
LLinear inear CCollider e+e- ollider e+e- clean environmentclean environment Ecm = 500 GeV / 1 TeV ; L= 500 / 1000 fbEcm = 500 GeV / 1 TeV ; L= 500 / 1000 fb-1 -1 / year/ year
LC source book
cros
s se
ctio
n (
fb)
mHSM (GeV)
HeeHee
HHZ
H
HZ
copiously produced, thousands of eventscopiously produced, thousands of events
S. Su U. Arizona - Colloquium 28
Higgs Mass, Decay Width and JPC Higgs Mass, Decay Width and JPC
• final state angular distributionfinal state angular distribution• angular and polarization angular and polarization
asymmetryasymmetry
Higgs mass:Higgs mass: mmHSM HSM = 40 MeV= 40 MeV• reconstruct Higgs in ZH productionreconstruct Higgs in ZH production• compare with indirect bounds from compare with indirect bounds from global fitglobal fit
Miller et. al. (2001)Garcia et al. (2001)
ee++ee-- Z Z
Higgs decay width:Higgs decay width: HSMHSM// HSM HSM = 6%= 6%
HSM HSM = = (H (HSMSM W W++WW--))
Br (HBr (HSMSM W W++WW--))
Higgs production HHiggs production H
Higgs decay HHiggs decay HSMSM W W++WW--
ee++ee--
ZZ
HH
S. Su U. Arizona - Colloquium 29
Higgs Coupling Higgs Coupling
mmHSM HSM 150 GeV 150 GeV • Higgs decay branching ratioHiggs decay branching ratio• Higgs production cross sectionHiggs production cross section
Carena et. Al. (2002) mmHSM HSM = 120 GeV= 120 GeV
mmHSM HSM 150 GeV 150 GeV • HHSMSM cc, gg, cc, gg, too small too small • HHSMSM W W++WW--,ZZ ,ZZ precisely measuredprecisely measured• HHSMSM bb bb precision reduced when precision reduced when mmHSM HSM 200 GeV 200 GeV • HHSMSM tt tt possible when mpossible when mHSM HSM 2 m 2 mtt
reconstruct Higgs potentialreconstruct Higgs potential
vv
S. Su U. Arizona - Colloquium 30
Photon Collider Photon Collider
ee++ee--collider operating in collider operating in mode mode EcmEcm=0.8 Ecm=0.8 Ecmeeee
• measure measure (H (HSMSM ) )
bb (H (HSMSM ) Br(H) Br(HSMSM bb) bb)
sensitive to heavy statessensitive to heavy states
• Higgs decay width Higgs decay width HSM HSM = = (H (HSMSM ) / Br(H) / Br(HSM SM ) )
• mmHSM HSM 200 GeV , directly measure 200 GeV , directly measure HSM HSM
• photon polarization photon polarization CP quantum number CP quantum number
every particle (get mass every particle (get mass from Higgs) contributesfrom Higgs) contributes
S. Su U. Arizona - Colloquium 31
There must be new physics beyond minimal There must be new physics beyond minimal Standard ModelStandard Model
• What is it ? What is it ? • How to probe it using Higgs How to probe it using Higgs
study ? study ?
What can we learn ? What can we learn ?
If we find deviation from Standard Model If we find deviation from Standard Model prediction … prediction …
S. Su U. Arizona - Colloquium 32
What New Physics ? What New Physics ?
• SM is an effective theory below some energy scale SM is an effective theory below some energy scale
Hierarchy problem:Hierarchy problem: MMEWEW100 GeV , M100 GeV , Mplankplank 10101919 GeV ? GeV ? Naturalness problem:Naturalness problem: mass of a fundamental scalar mass of a fundamental scalar (like (like Higgs) receive Higgs) receive huge huge quantum corrections: quantum corrections:
(m(mHH22))physicalphysical (m (mHH
22))0 0 + + 22 (100 GeV)(100 GeV)22
-(10-(101919 GeV) GeV)22precise cancellation precise cancellation up to 10up to 1034 34 orderorder
• SupersymmetrySupersymmetry SM particle superpartnerSM particle superpartner Spin differ by 1/2Spin differ by 1/2
MMinimal inimal SSupersymmetric upersymmetric SStandard tandard MModel (MSSM)odel (MSSM)
(10(101919 GeV) GeV)22
HH
- - 22
HH
S. Su U. Arizona - Colloquium 33
Higgs Sector in MSSM Higgs Sector in MSSM
SMSM MSSMMSSM
HHSMSM HHdd, H, Huu
HHSMSM00=v=v
v=246 GeVv=246 GeV
HHdd00=v=v1 1 ,,HHuu
00=v=v
22
vv22=v=v112 2 +v+v22
22
tantan=v=v22/v/v11
HH44 gg1122+g+g22
22
HHSMSM
(m(mHSMHSM22
vv22))
hh0 0 (m(mh0h0))
HH0 0 ,A,A0 0 ,H,H
((mmA0A0))
CP-even Higgs hCP-even Higgs h00
• decoupling limit: decoupling limit: mmA0 A0 m mZZ
hh00 similar to SM Higgs similar to SM Higgs
• hh00 mass mass tree level: mtree level: mh0h0mmZZ
loop corrections: loop corrections: mmh0h0 135 GeV 135 GeV
MSSM Higgs sector determined MSSM Higgs sector determined byby tantan andand m mA0A0
SM Higgs searches at low massSM Higgs searches at low massregion could be applied to the region could be applied to the light MSSM Higgs hlight MSSM Higgs h00
gauge gauge
couplingcoupling
S. Su U. Arizona - Colloquium 34
LEP Search Limit (MSSM) LEP Search Limit (MSSM)
AA00hh00
ZhZh00
0.5 0.5 tan tan 2.42.4
mmh0h0 91.0 91.0 GeVGeV
mmA0A0 91.9 91.9 GeVGeV
sinsin22((--effeff))
ee++ee-- Zh Zh00 ee++ee-- A A00hh00
coscos22((--effeff))
S. Su U. Arizona - Colloquium 35
Bounds on mA0 From Higgs Coupling
Measurements Bounds on mA0 From Higgs Coupling
Measurements
Br(HBr(HWW++WW--)=5%)=5%
Carena et. al. (2002)
hh00 coupling m coupling mZZ22
HHSMSM coupling m coupling mA0A022
-1 -1
• non-zero deviationnon-zero deviation
constraints on mconstraints on mA0A0
mmA0A0 650-800 650-800 GeVGeV
mmA0 A0 controls the degree of controls the degree of decouplingdecoupling
• mmA0 A0 m mZZ
decoupling regiondecoupling region no deviationno deviation
S. Su U. Arizona - Colloquium 36
Three SUSY Breaking Scenarios Three SUSY Breaking Scenarios
• supersymmetry must be brokensupersymmetry must be broken electron: m=0.511 MeV, electron: m=0.511 MeV, nono scalar-electron scalar-electron
• MSSM:MSSM: 105 new SUSY breaking parameters105 new SUSY breaking parameters out of out of controlcontrol
• mechanism for SUSY breaking: mechanism for SUSY breaking: (flavor blind)(flavor blind)
greatly reduce SUSY parametersgreatly reduce SUSY parameters
low energy MSSMlow energy MSSM(visible sector)(visible sector)105 parameters105 parameters
SUSY-breakingSUSY-breaking(hidden sector)(hidden sector)
a few parametersa few parameters
somethingsomething gravity gravity
gravity-mediated SUSY breaking gravity-mediated SUSY breaking (SUGRA)(SUGRA) gauge-mediated SUSY breaking (GMSB)gauge-mediated SUSY breaking (GMSB)
gauge interactiongauge interaction
anomaly-mediated SUSY breaking (AMSB)anomaly-mediated SUSY breaking (AMSB)
anomaly anomaly
S. Su U. Arizona - Colloquium 37
• LEP search bound LEP search bound
MSSMMSSM SUGRASUGRA GMSGMSBB
AMSAMSBB
mmh0h0max max
(GeV)(GeV)135135 127127 123123 125125
tantanminmin 0.5 or 0.5 or 2.42.4
2.92.9 3.13.1 3.83.8
Distinguish SUSY Breaking Scenario Distinguish SUSY Breaking Scenario
• deviation from SM Higgs coupling deviation from SM Higgs coupling constrains on constrains on mmA0A0
Dedes, Heinemeyer, SS, weiglein (2001, 2002)
mmA0A0 1000 GeV 1000 GeV
mmA0A0 500 GeV 500 GeV
S. Su U. Arizona - Colloquium 38
GMSB and AMSB GMSB and AMSB
mmA0A0 1100 1100 GeVGeV
mmA0A0 1300 1300 GeVGeV
S. Su U. Arizona - Colloquium 39
500 GeV 500 GeV m mA0 A0 600 GeV , tan 600 GeV , tan 30 30
Distinguish SUSY Breaking Scenario Distinguish SUSY Breaking Scenario
• if we know ranges if we know ranges of of mmA0A0, tan, tan from LHC from LHC • if we see if we see deviations deviations of coupling at LCof coupling at LC
Can we distinguish Can we distinguish various SUSY various SUSY
breaking scenario? breaking scenario?
SUGRASUGRA
GMSBGMSB
AMSBAMSB
S. Su U. Arizona - Colloquium 46
Conclusion Conclusion
• Why need a Higgs ? Why need a Higgs ?
• How to search the Higgs ?How to search the Higgs ?
• Is it really a (Standard Model) Higgs ? Is it really a (Standard Model) Higgs ?
• How to probe new physics using Higgs study ?How to probe new physics using Higgs study ?
Higgs mechanism provides a simple and elegant wayHiggs mechanism provides a simple and elegant way
to explain the origin of the massto explain the origin of the mass
- Tevatron Run II exclude Higgs up to 180 GeV (10 fbTevatron Run II exclude Higgs up to 180 GeV (10 fb-1-1))- LHC would find the Higgs if it is thereLHC would find the Higgs if it is there
- detail study at Linear Colliderdetail study at Linear Collider- measure Higgs mass, decay width, coupling… at high precisionmeasure Higgs mass, decay width, coupling… at high precision
Minimal Supersymmetric Standard Model (MSSM)Minimal Supersymmetric Standard Model (MSSM)
- constrain parameter space (mconstrain parameter space (mA0A0))
- distinguish various SUSY breaking scenariosdistinguish various SUSY breaking scenarios Heavy Higgs searchHeavy Higgs search
S. Su U. Arizona - Colloquium 47
The hunting is The hunting is continuing …continuing …
pppp
LHCLHC
2007--2007--
TevatronTevatron
Now --Now --
pp--
pp