Higgs and SUSY at the LHC

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.