higgs and susy at the lhc
DESCRIPTION
ATLAS. Higgs and SUSY at the LHC. Alan Barr on behalf of the ATLAS and CMS collaborations. ICHEP-17 Aug 2004, Beijing. Outline. Discovery and measurement of: Higgs sector of MSSM SUSY partners of SM particles . SUSY and Higgs discovery reviewed Reach, channels - PowerPoint PPT PresentationTRANSCRIPT
Higgs and SUSY at the LHCAlan Barr
on behalf of the ATLAS and CMS collaborations
ICHEP-17 Aug 2004, Beijing
ATLAS
• SUSY and Higgs discovery reviewed– Reach, channels
• Focus on some recent work: – Determination of higgs v.e.v. ratio (tan )– SUSY spin measurement– Mixed Higgs + SUSY cascade decays
• Discovery and measurement of:– Higgs sector of MSSM– SUSY partners of SM particles
Outline
(S)particle reminderSM+ MSSM Higgs SUSY
quarks (L&R)leptons (L&R) neutrinos (L&?)
squarks (L&R)sleptons (L&R)sneutrinos (L&?)
Z0
W±
gluon
BW0
h0
H0
A0
H±
H0
H±
4 x neutralino
2 x chargino
AfterMixing
gluino
Spin-1/2
Spin-1
Spin-0
Spin-1/2
Spin-0
BinoWino0
Wino±
gluino
~~
Extended higgs sector(2 doublets)
Neutral Higgs production
Mass of H or h
fb-1
1 year @1033
1 month @1033
1 year @1034
SM-like higgs discovery
ATLAS
Values for single experiment
h → requiresexcellent low-pT lepton + tau jet trigger
time
h: Number of observable final states 1 channel
2 channels3 channels
4 channels5 channels
several channelsobservable allows parameter determination ?
300 fb-1
Excluded by LEP
Suppressed b, Suppressed g coupling
Conservative in tan
Heavy neutral higgs (H,A)
Measuring tan
• For large (>5) tan – b Yukawa dominates – tan2 – Measure – Compare to NLO
bbHAgg 00 ,
• Ratio of v.e.v.s of the 2 MSSM Higgs doublets
• Important for understanding EWSB
~
• Errors dominated by theoretical uncertainty on NLO cross-section
• With signal discovery at 5σ, tan measurable to 35%.
Measuring tan (2)
N.B. , M2 kept fixed here
Charged higgs production/decay
• Associated production with t and b quarks
• Decay H± → – Very complicated
final state!– Combinatorial BG
• Also H± → – BR decreases as
mA increases~6 jet + lepton + missing energySM background uncertain?
• When H+ is close to top mass:– H+ -> tb
or– t -> H+b
• Revised analyses in progress
ATLAS
Charged higgs
Overall Discovery Potential: 300 fb-1
Can we distinguish between SM and extended Higgs sectors by parameter measurements?
ATLAS
• Whole plane covered for at least one Higgs
• Large wedge area (intermediate tan ) where only h is observed
• No direct evidence for higgs beyond SM
SM or Extended Higgs Sectors?
First look using rate measurements from VBF channels (30fb-1)
R = BR(h) BR(hWW)
=|RMSSM-RSM|exp
only statistical errors consideredassumes Higgs mass exactly known
Deviation from SM expectation
potential for discrimination seems promising!
ATLAS
Searching for SUSY• If SUSY was exact we’d have seen it
already• Variety of ways to induce SUSY masses:
– Minimal super-gravity (mSUGRA)– Anomaly mediated SUSY breaking (AMSB)– Gauge mediated SUSY breaking (GMSB)
• Experimental emphasis is on building general toolkit of techniques based on types of signatures of above
• Generally search reach ~2 TeV.
• Finial discovery limit ~ 2.5 TeV squark or gluino
• Initially will be limited by detector uncertainties, not SUSY stats!
• Also need to understand SM backgrounds
SUSY Discovery - mSUGRA
Scalar mass term
Gaug
ino
mas
s ter
m
Slepton, squark, neutralino masses
~~
~
l ll
qL
q
~
Apply corrections for electron and muon energy scale and efficiency
Flavor Subtracted mass to remove the contribution from uncorrelated SUSY decays:e+e- + +- - e+- - e-+
M(2)-M(1) ≈ 105 GeV
5 fb-1
SUSY measurements - mass• Mass measurements
from exclusive cascade decays
• Mass differences well measured– Typically limited by
detector performance• Of order 1%
• Error in overall mass scale– Unknown missing energy
• Of order 10%
ATLASSquark – neutralino1mass difference5 fb-1
q
qR~
qR~
q
p p
SUSY SPIN @ LHC• SUSY particles
have spin differing by ½ from SM
• “Discovering SUSY” means measuring spins of new particles
• Possible at LHC?• Investigation of
mSUGRA “Point 5”
Spin-½, mostly wino Spin-0
Spin-½
Spin-0
Spin-½, mostly bino
Final state = jet + l+ + l- + ET( + decay of other sparticle)
},{ el
Polarise
MeasureAngle (or inv mass)
Chiral coupling
Similar technique allows measurement of tan from muon/electron asymmetry
l+
l- parton-level
-> Measure spin-1/2 nature of neutralino-2-> Also can measure scalar nature of slepton-> Success at several distinct points in parameter space
detector-level
Lepton+jet invariant massCh
arge
asy
mm
etry
,
spin-0
Even
ts
llllA
SUSY spin – observable distributions
0* 1*
ATLAS
ATLAS
SUSY produces Higgsg (600 GeV)~
q (720 GeV)~
~ 0
2
~ 0
1
~ 0
4 ~
2
h0, H0, A0, H±
(170 GeV)
(95 GeV)
0
3
~(340 GeV)
1
~
• Provided Heavy higgs are <150 GeV -> produced• Missing energy + jet/lepton + higgs decay->bb• Apply very simple (general) analysis
Strongly interacting, so high rate
g (1200 GeV)~
q (800 GeV)~
~ 0
2
~ 0
1
(400 GeV)
(200 GeV)
1
~
h0, H0, A0, H±
0
4 ~
2
0
3
~ (1000 GeV)~
Other points & combinations also investigated
~
SUSY -> h,H,A -> bb : susy signal: susy bkg: SM tt bkg
30 fb-1h H,A h
H,A
H0, A0 -> SUSY -> leptons
hep-ph/0303095
SUSY -> light higgs• Region of
parameter space where h is discoverable
• ~ cosmological “bulk region”
CMS note 2003-033 for summary
H± -> SUSY • Harder!• Works in
restricted area of , M2 space
• Complements tau, tb analysis.
hep-ph/0303093H 2,3
0 1,2 3l + ET
miss
Conclusions (1)• LHC SUSY and Higgs search strategies
well developed– Constantly being reviewed / developed
• New techniques in Higgs sector– Production via Vector Boson Fusion
• Improves reach for MSSM benchmarks– Couplings if only lightest higgs accessible
• Infer non-SM Higgs sector– Measurement of tan
Conclusions (2)• New SUSY techniques
– Lepton asymmetry• Charge -> spin determination• Flavour -> tan
– Full likelihood event reconstruction• 3rd generation squarks + heavy gauginos
– (not covered in this talk)• Combined SUSY + Higgs
– Complimentary to standard Higgs searches– Could help dis-entangle complex SUSY
chains• Much work going on for trigger,
calibration, systematics.
Backup slides
ATLAS
SM-like higgs discovery
h → requires multi-object t-jet, lepton trigger
Charged higgs
SUSY spin – lepton asymmetry
m/mmax = sin ½θ*
Back to backin 2
0 frame
θ*
quark
lepton
Phase space -> factor of sin ½θ*Spin projection factor in |M|2: l+q -> sin2 ½θ* l-q -> cos2 ½θ*
l+
l-
Phase space
Prob
abilit
y
Lq~ Lq
Rl
~02
~Rl
Invariant mass
In presence of spin-correlations, lq invariant mass is different for l+ and l-
mSUGRA Dilepton edge reach
SM-like higgs rate measurement
Overall Summary
Two experiments, 30 fb-1, charged and neutral higgs.