lhc prospects on higgs and physics beyond the standard model (susy)

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

http://www.cern.ch/lhc/



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LHCLHC

http://www.cern.ch/lhc/



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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 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



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

lhc prospects on higgs and physics beyond the standard model (susy)

Documents

high mass higgs

atlas cms

higgs boson signal mh

detectlow mass higgs

includedlow mass higgs

lhcatlascmsexpected

lhc startupyear

lhc prospects