Discovery Potential for MSSM Higgs Bosons
with ATLAS

Johannes Haller (CERN)

on behalf of the ATLAS collaboration

International Europhysics Conference on High Energy Physics,
July 21st-27th 2005, Lisbon, Portugal

large loop corrections to masses	and couplings

mainly dependent on t/ t sector

parameters:

Mtop and Xt, MSUSY, M2, , Mgluino

mass prediction Mh < 133 GeV

(for Mt = 175GeV)

MSSM Higgs Sector

MSSM: 2 Higgs doublets  5 physical bosons: h, H, A, H+, H-

phenomenology at Born level described by tan, m A

mass prediction: Mh < MZ

couplings: gMSSM = ξ · gSM

no coupling of A to W/Z

large tan large BR(h,H,A,bb)

-----

tan

cot

A

cos(-)

cos/cos

sin/sin

H

sin(-)

-sin/cos

cos/sin

h

W/Z

b/

t

ξ

: mixing angle between CP even Higgs bosons

(calculable from tanand MA)

for exclusion bounds

and discovery potential:

fix the 5 parameters in

benchmark scenarios

and scan (tan, MA)- plane

~

current exclusion in (tan,MA)-plane:

LEP excludes low tan and	low MA region

note: no exclusion from LEP

for Mt larger ~183 GeV

main questions for LHC/ ATLAS:

Can at least 1 Higgs be discovered in the allowed parameter space?

How many Higgs bosons can be observed ?

Can the SM be discriminated from models with extended Higgs	sectors	(like MSSM) ?

The (tan, MA)-Plane

Benchmark Scenarios

MHMAX scenario maximal Mh < 133 GeV

Nomixing scenario small Mh < 116 GeV

Gluophobic scenario	Mh < 119 GeV

coupling of h to gluons suppressed

designed to affect discovery via

gg h, h and hZZ 4l

Small  scenario	Mh < 123 GeV

coupling of h to b () suppressed

(for large tan and MA 150500GeV)

designed to affect discovery via

VBF, hand tth, hbb

4 CP conserving scenarios considered

to examplify the discovery potential

mainly influence on phenomenology of h

masses, coupling and BRs calculated with FeynHiggs (Heinemeyer et al.)

500

-1100

500

2000

800

small 

500

-750

300

300

350

gluophobic

800

0

200

200

2000

no mixing

800

2000

200

200

1000

mh-max

Mgluino (GeV)

Xt (GeV)

M2 (GeV)

(GeV)

MSUSY (GeV)

Name

suggested by Carena et al.,

EPJ C26, 601(2003)

eff. hg - coupling

hbb - coupling

already

at LEP

Newly

designed

for

hadron

colliders

Technical Issues

combination of latest results from (MSSM corrected) studies for SM Higgs boson (see talk of P.Conde) and dedicated MSSM Higgs analysis (heavy higgs states)

key performance numbers obtained from full simulation: (e.g. trigger efficiencies, b-tagging, -	identification, mass resolutions ...)

signal efficiencies and background expectations from fast simulations

developments/ improvements:

new and updated search channels:

new: VBF with Higgs decay to , WW, .

new: ttbW+bHbqq+b

updated: ttH, Hbb (better simulation of bgr.)

updated/ new: bbHHnow also had. decay

improved theoretical calculations:

FeynHiggs: full one-loop corrections and dominant two-loop corrections included (increase of Mh by several GeV)

 considered to give most accurate calculations at present

two expected data sets: 30 fb-1 and 300 fb-1

discovery = 5  excess using Poisson statistics

no systematics included

LO SM prod. cross section (M. Spira) corrected with FeynHiggs

 conservative!

most important channels: VBF

differences mainly due to Mh

almost entire (tan, MA)-	plane covered

Light Higgs Boson (30 fb-1)

h observable in entire parameter space and for all benchmark scenarios?

ATLAS (prel.)

ATLAS (prel.)

ATLAS (prel.)

See talk of P. Conde for SM Higgs searches with ATLAS

hole due to reduced BR for H 

Light Higgs in Small  Scenario (30 fb-1)

Complementarity of search

channels almost guarantees

the discovery of h

ATLAS (prel.)

ATLAS (prel.)

covered by enhanced BR to

gauge bosons

Light Higgs Boson (300 fb-1)

VBF:

only

30 fb-1

also h, hZZ4 leptons, tthbb contribute

large area covered by several channels

 stable discovery and parameter determination possible

small area uncovered (Mh = 90 to 100 GeV)

ATLAS (prel.)

ATLAS (prel.)

rec. mass for had.had.

Neutral Heavy Higgs Bosons (H/A)

prod ~ (tan)2; important at large tan

new analysis:  had. had.

BR(H/A) ~ 10 % , rest is bb

example: bbH/A, H/A  

bb H/A bb  covers large tanregion

other scenarios similar

intermediate tan region not covered

New: take running b-

quark mass for prod

30fb-1

discovery reach for H/A:

ATLAS

(prel.)

ATLAS

(prel.)

only very few events remain after cuts (acceptance ~10-3)

LVL1 trigger performance crucial

detailed study: >90% LVL1 efficiency for MA>450GeV via “jet+ET,miss” and “+ ET,miss” triggers with a rate of ~1.4 kHz (within rate limit)

VBF channels, H/A only 30fb-1

300 fb-1

Overall Discovery Potential (300 fb-1)

ATLAS (prel.)

at least one Higgs boson is observable for all parameter points (in all four benchmark scenarios)

in some parts: >1 Higgs bosons observable

 distinguish between SM and extended Higgs sector

but: significant area where only h is observable.

basic conclusions independent of mtop

ongoing:

including SUSY decay modes to increase areas for heavy

Higgs bosons , e.g. H  3l + ET,miss

can SM be discriminated from extended Higgs sector by

parameter determination e.g. via rate measurements?

Summary

A consistent investigation of the ATLAS discovery potential in the MSSM Higgs sector with new MC studies and new theoretical calculations has been performed.

In all 4 CP conserving MSSM benchmark scenarios at least one Higgs boson can be discovered.

In some areas of the parameter space more than one Higgs bosons can be discovered.

direct discrimination between SM and	extended Higgs sector

Back-up slides

SM or extended Higgs Sector ?

BR(h WW) BR(h )

estimate of sensitivity from rate measurements in VBF channels (30 fb-1)

only statistical errors

assume Mh exactly known

potential for discrimination

seems promising

needs further study incl. sys. errors

compare expected measurement of R in MSSM with prediction from SM

=|RMSSM-RSM|exp

R =

ATLAS

(prel.)

ATLAS

(prel.)

Charged Higgs Bosons

SUSY04 HERA searches

Johannes Haller

The first level trigger of ATLAS

Johannes Haller

2003-08-16T18:40:24

Frank Merritt