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LHC Prospects on Higgs and LHC Prospects on Higgs and physics beyond the Standard physics beyond the Standard
Model (SUSY)Model (SUSY)Riccardo Ranieri
INFN and Università degli Studi di FirenzeINFN and Università degli Studi di Firenzeon behalf of ATLAS and CMS Collaborationson behalf of ATLAS and CMS Collaborations
DIS2006 DIS2006 XIV International Workshop XIV International Workshop on Deep Inelastic Scatteringon Deep Inelastic Scattering
Tsukuba (Japan), 20-24 April 2006Tsukuba (Japan), 20-24 April 2006
DIS2006Tsukuba, 20-24 April 2006
LHC Prospects on Higgs and BSM Physics
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ATLAS & CMS at LHCATLAS & CMS at LHC– Detectors optimised for Higgs boson
and SUSY searches very high energy: LHCLHC pp √s=14 TeVpp √s=14 TeV
– inelastic cross section: σσpppp=55 mb=55 mb
– interaction rate: 40 MHz40 MHz high luminosity: (2x)10(2x)1033 33 cmcm-2-2ss-1-1101034 34 cmcm--
22ss-1-1
– per year: 20 fb20 fb-1-1100 fb100 fb-1-1
BIG detectors– CMS: 15 m x 21.5 mCMS: 15 m x 21.5 m– ATLAS: 25 mATLAS: 25 m x 46 mx 46 m
CMS = Compact Muon CMS = Compact Muon SolenoidSolenoid
LHC = LHC = Large Large Hadron Hadron ColliderCollider
ATLAS = A Toroidal LHC ATLAS = A Toroidal LHC ApparatuSApparatuS
first collisions in Autumn first collisions in Autumn 20072007
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LHCLHC
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ATLASATLAS
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CMSCMS
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Expected LHC scheduleExpected LHC schedule
11stst July 2007 July 2007LHC closed and set up for beams
August 2007August 2007first beam in machine
October / October / November 2007November 2007first collision followed by a short pilot run (~10 pb–1)
someday in 2008someday in 2008first physics run (few fb–1)
from 2009from 2009physics run 10/20 fb–1 to 100 fb–1 per year
M.Lamont @ TeV4LHC, April 2005http://lhc-commissioning.web.cern.ch/lhc-commissioning/presentations/lamont-comm-tev4lhc.ppt
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Where will we be at LHC Where will we be at LHC startup?startup?
mH>114.4 GeV/c2 @ 95% CL
¿ Higgs boson signal mmHH=115 GeV/c=115 GeV/c22 from LEP2 data ?
CERN-EP/2003-011
LHWG Note/2002-01
Searches at TeVatron up to LHC startup…
year 2007: ~2 fbyear 2007: ~2 fb-1-1
mmHH<125 GeV/c<125 GeV/c22 covered to exclusion covered to exclusion
year 2008: ~4 fbyear 2008: ~4 fb-1-1
mmHH<130 GeV/c<130 GeV/c22 covered to exclusion covered to exclusion
33σσ evidence up to m evidence up to mHH=125 GeV/c=125 GeV/c22FERMILAB-PUB-03/320-E
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Associated Associated productionproduction ttHttH and and bbHbbH
– high-pT lepton, top reconstruction,b-tag
-- --
SM Higgs Production at SM Higgs Production at LHCLHC
Gluon FusionGluon Fusion– the highest
cross section
Vector Boson FusionVector Boson Fusion– two high-pT
forward jets
Associated ProductionAssociated Production WHWH and and ZHZH
– one or two high-pT leptons useful for the trigger
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SM Higgs DecaysSM Higgs Decays
“light” Higgs
2mZ
– decays into Vector bosons W and Z
» “golden” channels
– two-photon decays» extremely
“clean” but rare and difficult to detect
LEP excluded
– hadronic and decays are favourite
» …but difficult to select
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Low Mass Higgs: HLow Mass Higgs: H→→This decay is very rare (Br≈10-3)
σ(pp→H115)xBr(H→)=76 fb (NLO)
S/B≈1/20– good resolution mass peakmass peak– Electromagnetic Calorimetres crucialcrucial
for H→: σσ(m(m)/m)/m≈1%≈1% needed
motivation for LAr (ATLAS) and PbWO4 (CMS) calorimetres
– high granularity– response uniformity
CERN/LHCC 96-40 ATLAS TDR 1
CERN/LHCC 96-41 ATLAS TDR 2
CERN/LHCC 97-33 CMS TDR 4
– 3 main background processes:» irreducibile: gg/qq→
81 pb81 pb
+jet (with “real” or “fake” second photon)9x109x104 4 pbpb
» hadronic QCD jets (π0 decays)
101088pbpb
» ATLAS reach with 10 fb10 fb-1-1 and mmHH=115 GeV/c=115 GeV/c22:» Signal Significance: SS//√B√B=2.0=2.0 (K-factors not included)
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Low Mass Higgs: ttH(Low Mass Higgs: ttH(→→bb)bb)This is the favourite decay σ(pp→H115)xBr(H→bb)=28 pb
S/B<10-7
tagging the top quarks helps a lot– t→bW(→μν)– t→bW(→jj)
“crowded” final state– 6 jets (4 of them are b-jets) 6 jets (4 of them are b-jets)
+ additional ISR/FSR jets+ additional ISR/FSR jets» 4 b-tagged jets needed to
reduce combinatorics
– 1 isolated lepton1 isolated lepton» it’s the key for trigger
optimised analysis– pz from W-mass constraints
– likelihood pairing of jets
----
-
ATL-PHYS-2003-024
ν
»Final result for Final result for likelihood analysis likelihood analysis ((mmHH=115 GeV/c=115 GeV/c22):):
»30 fb-1: S/√B=3.4»10 fb10 fb-1-1: S/√B=2.0: S/√B=2.0
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– The “goldengolden” channel well defined peaks ZZ→→μμ++μμ--
– mmHH>2m>2mZZ: real Z’s
main backgrounds– reducible: tt, Zbb
» μ isolation
» Z reconstruction (mZ)
– irreducible: ZZ» qq production mechanism
dominates softer muons Luminosity required for a 55σσ
discovery:– 1010-30 fb-30 fb-1-1 if m if mHH>2m>2mZZ
» 2-3 low luminosity LHC years
– up to 100 fbup to 100 fb-1-1 if m if mHH<2m<2mZZ
» only one reconstructed Z» high luminosity runs
High mass Higgs: High mass Higgs: HH→→ZZZZ(*)(*)→→44μμ
CMS AN 2003-005
CMS AN 2003-007
- -
-
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ATLAS & CMS Discovery ATLAS & CMS Discovery PotentialPotential
After detector calibration and LHC pilot run…
– …almost all the “allowed” mass range can be explored during the first year first year (10 fb-1)
– ...after 2 years 2 years (≈30 fb-
1) 77σσ significance over the whole mass spectrum, covered by more than onemore than one channel
» LEP excess is near…
CMS NOTE 2003/033CERN/LHCC 99-15 ATLAS TDR 15
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4 neutral fermions: 4 neutral fermions: Neutralinos: Neutralinos: 1,2.3,41,2.3,4
4 neutral fermions: 4 neutral fermions: Neutralinos: Neutralinos: 1,2.3,41,2.3,4
~~00
4 charged fermions: 4 charged fermions: Charginos: Charginos: 1,21,2
4 charged fermions: 4 charged fermions: Charginos: Charginos: 1,21,2
~~±±
MSSM - mSUGRAMSSM - mSUGRA
5 Higgs bosons:5 Higgs bosons:
2 neutral CP-even: 2 neutral CP-even: hh, , HH
1 neutral CP-odd: 1 neutral CP-odd: AA
2 charged: 2 charged: HH++,,HH--
5 Higgs bosons:5 Higgs bosons:
2 neutral CP-even: 2 neutral CP-even: hh, , HH
1 neutral CP-odd: 1 neutral CP-odd: AA
2 charged: 2 charged: HH++,,HH--
mSUGRA 5 parameters: mSUGRA 5 parameters: mm½½, , mm00, , tantanββ, , AA00, , sign(sign(μμ))mSUGRA 5 parameters: mSUGRA 5 parameters: mm½½, , mm00, , tantanββ, , AA00, , sign(sign(μμ))
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MSSM Higgs boson massesMSSM Higgs boson masses
– Born level mmhh<m<mZZ
mmAA<<mmHH
mmWW<<mmHH±±
mmAA=(mmHH±±2-mmWW
2)½
– Loop corrections depend on top and stop
masses, mixing, … modify previous
sequence, important for hh
Phys.Rev.D66:055004,2002
hep-ph/0205160
Hig
gs M
ass
[GeV
/c2]
mh increases with mA up to asymptote: mh<130 GeV/c2
mH, mA and mH±
degenerate for mA>140 GeV/c2
when mmAA/m/mZZ>>1>>1 MSSM hMSSM h behaves as a SMSM HiggsHiggs
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Neutral MSSM Higgs at LHCNeutral MSSM Higgs at LHC– Production:
» gggg→→A/HA/H» pppp→→A/HbbA/Hbb
– Neutral Higgs mixing (α) modifies couplings to bosons and fermions with respect to the Standard Model
– high tanβ» enhanced decays
h/H/A→bb,ττ
– low mixing α» h→bb,ττ
suppressed
-
-
--
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– A lot of decay channels
– “SM like”» h→,bb» H→4ℓ
– purely MSSM » A/H→μμ,ττ,bb» H→hh» A→Zh» H±→τν,tb
– if decay into SUSY sparticles are allowed
» H/A→22
» 2→h1
– Complete coverageComplete coverage of (mA,tanβ) plane with 30 fb30 fb-1-1
» high tanβ-mA region is the more accessible
» only h detectable in most of the plane
H and A searchesH and A searches
-
-
~ 0~0
~0 ~0
hep-ex/0602042
(LHWG Note 2005-001)
95% CL Limitsmt=174.3 GeV/c2
mh [GeV/c2
]
mA [GeV/c2
]tanβ
No mixing(2005) >93.6 >93.6 0.4÷10.2
mh max(2005) >92.8 >93.4 0.7÷2.0
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h/H/Ah/H/A→→μμ++μμ--
Enhancement of BR(h/A/H→μ+μ-) for high tanβ
– Main backgrounds:» Drell-Yan Z/*→μ+μ-
» tt (both t→bW→bμνμ), Zbb
– Background suppression» b-tagging (suppresses DY)» central jet veto (reduces tt,
Zbb)
» ETmiss cut (reduces tt)
Three regions (mhmax<135 GeV/c2):
1. Decoupling regime mmAA>>m>>mhhmaxmax
» h similar to SM, A/H indistinguishable
2. Low mA regime mmAA<m<mhhmaxmax
» H similar to SM, h/A degenerate» Z peak, high luminosity needed
3. Intense coupling regime mmAA≈m≈mhhmaxmax
» h/H/A not degenerate in mass» indistinguishable (detector resolution)
-
-- -
-
55σσ
without without systematic systematic uncertaintieuncertaintiess
CMS AN 2005-033
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MSSM Charged HiggsMSSM Charged Higgs
H± production– if mH
±<mt: tt→→HH±±bb
– if mH±>mt: gbgb→→tHtH±±
Decays:– if mH
±<mt: HH±±→→τντν
– if mH±>mt: HH±±→→tbtb
LEP 95% CL limit:– mH
±>78.6 GeV/c2
» decay channels: H±→τν,csLHWG Note 2001-005
hep-ex/0107031
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HH±± searches searches mmHH
±±<m<mtt
– search in tt events» lepton from top quark
» τ from H±→τντ
– excess of τ’s in tt events
» H± mass can not be reconstructed
mmHH±±>m>mtt
– associated production with top
» gb→tH±(→τντ,tb)
– background from tt and Wt
» final states with τ leptons
CMS NOTE 2000/039
CMS NOTE 2000/045
CMS NOTE 2002/024
CMS AN 2005-067
CMS AN 2006-028-
-
-
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SUSY LHC discovery reachSUSY LHC discovery reach 1 fb-1 of data should allow
discovery if squark or gluino mass < 1.5 TeV/c2.
ATLAS and CMS potentials similar
Those studies assumed a perfectly known SM physicsperfectly known SM physics (only statistical errors on background rate) and ideal detectors (perfectlyaligned, nominalasymptotic performance)
SUSY discovery likely todepend not on statistics buton the understanding of SM background and detector systematics: excess of events
1 fb-1
q (1 TeV/c2)~
g (1 TeV/c2)~
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It is not enough to observe the excess over the Standard Model…
Fix a set of points in the parameter space
Get information on the spectrum (end-points)
Reconstruct sparticles
DISCOVERYDISCOVERY SUSY SPECTROSCOPYSUSY SPECTROSCOPY
This requires a different approach…This requires a different approach…
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∫L=30 fb-1
tanβ=2.1
m0=100 GeV/c2
m½=300 GeV/c2
A0=-300 GeVsign(μ)=+
Mll (GeV/c2)
Edge accuracy with 30 fb-1: 0.5%
e+e- + +-
The golden decayThe golden decay The neutralino leptonic decay is the starting
point for reconstruction of the sparticle masses
lqq
l
g~ q~ l~
~
~
p p
∫L=5 fb-1
tanβ=6.0
CERN/LHCC 99-14 ATLAS TDR 14
CERN/LHCC 99-15 ATLAS TDR 15
hep-ph/0007009
The measurement of the missing transverse energy EETT
missmiss is the key key pointpoint
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b~
g~
Sparticle reconstructionSparticle reconstruction
– Lepton scale:» LHC goal: 0.1%» material budget,
alignment, magnetic field
– Jet energy scale:» LHC goal: 1%» FSR, jet cone
– Reconstruction can be done with only 1-10 fb-1
– Statistical uncertainties <<1% with 300 fb-1
– Main uncertainty: energy scale and LSP mass
p
M
M1p
01
02
~
~
p
p
g~
b~
b
b
01
~
02
~ ~
300 fb-1
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The earliest discovery?The earliest discovery?
A new resonance decays into two leptons…
ZZ′′ (new gauge boson) ? (new gauge boson) ?ZZ′′ (new gauge boson) ? (new gauge boson) ?
AAHH, Z, ZHH (Little Higgs) ? (Little Higgs) ?AAHH, Z, ZHH (Little Higgs) ? (Little Higgs) ?
GG(1)(1) (Randall-Sundrum) ? (Randall-Sundrum) ?GG(1)(1) (Randall-Sundrum) ? (Randall-Sundrum) ? (1)(1)/Z/Z(1)(1) (TeV (TeV-1-1 Extra Extra Dimensions) ?Dimensions) ?(1)(1)/Z/Z(1)(1) (TeV (TeV-1-1 Extra Extra Dimensions) ?Dimensions) ?
GG(KK) (KK) (ADD) ?(ADD) ?GG(KK) (KK) (ADD) ?(ADD) ?
… … ??… … ??
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ConclusionConclusion– LHC has potential for Higgs boson(s) and SUSY
particles discovery already in the first yearalready in the first year (months?) of operation 1 LHC day at 1033 cm-2s-1 ≡ 10 years at previous machines
BUTBUT– At the beginning a lot of timea lot of time (whole first year?) will be
needed to understand the detectors, reach the desired performance, optimize physics selection and precisely measure SM backgrounds
HOWEVERHOWEVER– The ATLASATLAS and CMSCMS detectors are designeddesigned for new
physics searches, no surpriseno surprise that they can cover most of the spectrum of HiggsHiggs and sparticle masses within 1 1 yearyear of start of physics collisions