A/H and A/H decays at the LHC Outline of the talk: The LHC and ATLAS,CMS MSSM A/H Higgs production...

A/H and A/H decays at the LHC

Outline of the talk:

• The LHC and ATLAS,CMS

• MSSM A/H Higgs production

• A/H

• A/H

• Conclusions

HEP2003 Europhysics Conference Aachen, Germany, 17-23 July 2003

Silvia ArcelliUniv. of Bologna and INFN

for the ATLAS and CMS Collaborations

Covering Abstracts: Abs 674: “Search for A/Hwith CMS” Abs 421: “Studies of Lepton Flavor Violation with ATLAS”

EPS03 Meeting, 17 July 2003, Aachen 2A/H and A/H at LHC, S.Arcelli

The LHC and ATLAS,CMS detectorspp at 14 TeV, collision rate 40 MHz , with a design luminosity L= 1034 cm-2 s-1.First physics run planned for Aug 2007 at L= 2 x1033 cm-2 s-1

ATLAS and CMS detectors equipped with high precision tracking systems,high resolution ECAL and hermetic calorimetry , large acceptance muon spectrometers to ensure:• Efficient b-tagging and identification

• Good jet and missing ET resolution

• Precise muon ID & reconstruction


MSSM A/H Production

Golden channel at LHC is A/H (BR ~10%), but other rare/non-standard decays can be effective probes of the MSSM Higgs sector and of physics beyond the SM:

• A/H: very small branching ratio (~3 ×10-4) but very clean signature

• A/H: search for LFV effects involving the 2nd and 3rd generation

• Predominantly via gluon fusion and bbA/H associated production

• bbA/H production and decays to down type fermions dominant at high tan • A/H degenerate over most MA-tan plane


A/H

Decay hardly observable at LHC in case of SM Higgs (s,vLHC), but low branching ratio is compensated by the cross-section enhancement in the MSSM : • Although BR(A/H)/BR(A/H)~ 2 10-3 , discovery potential in channel enhanced by very efficient muon ID+reconstruction (>90%) and invariant massresolution M )= 1-2% , ~10 times better than in

• Excellent di-muon mass resolution allows for a precise measurement of the Higgs mass and a direct measurement of the Higgs width for high tanFeasibility studies:

ATLAS: ATLAS physics TDR

CMS: CMS-NOTE-98-039, and full simulation+realistic reconstruction study, results presented in this talk (CMS preliminary) (L. Bellucci, “MSSM Neutral Higgs Bosons Search with CMS in the channel”, PHD Dissertation, Universita’degli Studi di Firenze)


bbA/H associated production channel, assuming low luminosity conditions. Search strategy based on clean signature from:

• high Pt, isolated muons

• Sharp di-muon mass peak

• b-tag of the associated production

Main Background processes:

Drell-Yan production Z/*

bbZ/* bb(~ 2% of inclusive Drell-Yan )

other potential backgrounds like bb,cc, WW,ZZ +X negligible.

top pair production ttbb

bbA/Hbb in CMS


• Two isolated muons with PT >10 GeV, efficiency ~ 87 %

• Mass resolution 1.5 %, H,A ~ O(1-10 GeV) depending on MA,tan

M(GeV)

MA=150 GeVtan= 30

H,A ~ 3 GeV

Di-muon system:

•With cuts on the di-muon system alone, 5signal observable only with integrated luminosity >100 fb-1

•b-tagging allows to substantially improve the S/B ratio!

M(GeV)

MA=150 GeVtan= 30

L= 20 fb-1

CMS preliminary

CMS preliminary


b-jets from associated production are soft, low efficiency for jet reconstruction (typical efficiency for 1 jet ID+b-tag ~ 20%)

Event b-tag used, relaying on a combination of different variables:

• Number of secondary vertices• 2,3-d track impact parameter• impact parameter significance

b-tag ~40%, factor ~10 rejection on Z/*

B-jet ET(GeV)

N. Of secondary vertices

B-Tagging: MA=150 GeVtan= 30

CMS preliminary

CMS preliminary


b tagging not effective against top background, which contains 2 hard central jets from b’s ; use a jet veto and require small missing ET:

• No jet with ET>30 GeV

• ETmiss < 40 GeV

Top background suppressed by factor ~ 20, signal ~ 70%

Top Rejection:

Missing ET(GeV)

jet ET(GeV)

Pro

babi

lity/

dET je

t

Eve

nts/

dET je

t

CMS Preliminary

CMS Preliminary


• Precise measurement of A/H mass, expect dM/M~0.2 % for L=60 fb-1

• For tan>20, where the natural Higgs width dominates over the detector resolution, can directly measure and have an independent constraint on tan in addition to that from event rates

L= 20 fb-1

M(GeV)

• Final selection efficiency ~ 22%~ independent on the Higgs mass.

• Fitting with a gaussian (for signal)+ exponential (for background):

Mean = 150.7±0.6 GeVWidth= 3.7±0.7 GeV

With full di-muon mass resolution/calibration this channel should allow for :

S / (S+B) ~ 7

Eve

nts/

GeV

M(GeV)

MA=150 GeVtan= 30

CMS preliminary


• Substantial portion of the MA-tan plane covered already with 20 fb-1. Comparable results obtained in ATLAS TDR study

• Same strategy can be extended to h/A search for MA [105-125] GeV (h,A degenerate), requires maximal luminosities (recent studies by ATLAS, ATL- PHYS- 2002- 021, ATL- PHYS- 2003- 013)

M(GeV)

ATLAS

A/H, 5 discovery reachta

n

CMS preliminary


A/H

M(GeV)

BR

Observation of atmosferic neutrino oscillations with maximal mixing and implies lepton number non-conservation expect LFV decays

One possibility to search for LFV effects at the LHCis the decay A/Hstudy done by ATLAS.(ATLAS-COM-PHYS-2002-031)

Two different (Type III) 2-Higgs doublet models (a,b) were considered:

BR(A/H 2 2mmBR(HSM

• depends on LFV coupling , and widths H

SM,A/HModel a,b

• BR(A/H for = 1


• Jet veto against W+jets, b-jet veto against tt (gluon fusion production is considered)

• In hadronic channel select 1-prong decays (collimated jet with single energetic hadron) to suppres W+jets background

ETmiss

hadron (tau jet), electron

Search performed using hadronic and e tau decays. Background expected from Z/* , tt, WW,WZ production and W+jets (hadronic channel):

• High pT ,isolated , muon harder than tau decay product with large opening angle in transverse plane (2-body decay).

• Tau higly boosted, require Etmiss collinear

to visible tau decay product and pT >50 GeV

pT = pT

-jet,e + ETmiss (p can also be derived)


A/H, jet +

L= 30 fb-1

MA=130 GeVtan= 45

K=1

A/H, e

L= 30 fb-1

MA=130 GeVtan= 45

K=1

Signal in 30 fb-1

MA=130 GeV, tan=30, = 1

Significance>5 up to MA 150 GeV

•Comparable significance in jet +, e

•Analysis efficiently differentiates A/H and A/H (A/H ), separation depends on on ,

M(GeV) M(GeV)

M(GeV)

L= 30 fb-1

Eve

nts/

2 G

eV


•5bounds on range from 0depending on tan

•95% C.L. exclusion limits for 1 can be set with very low integrated luminosities (< 10 fb-1)

• Range 10-2 –1 in explored with L=100 fb-1

• About 10-100 better reach than current limits from g-2 data, ~10 times better than Tevatron

Limits on depend on the Model:

M(GeV)


Conclusions

Despite low BR~2x10-4, A/H is a quite powerful channel for the detection and the study of the MSSM heavy neutral Higgs bosons:

● Complements “golden channel” A/H in A/H discovery.

● Allows for a precise measurement of Higgs mass and provides the unique possibility to directly measure the A/H natural width at high tan

● May allow to disentangle all neutral Higgs states in regions where h,H,A are non-degenerate, possibility under investigation (“ Intense-Coupling Regime”, MA~ 130 GeV, high tan, E.Boss, A.Djouadi, A.Nikitenko, hep-ph/0307079)

Within the framework of 2HDM models, the search for A/Hdecays at the LHC will allow to test Lepton Flavour Violation with a much better sensitivity compared to current constraints from muon g-2 data, and to the bounds achievable at the Tevatron in the same search channel.

Many thanks to my colleagues in CMS and ATLAS for providing material and help in preparing this talk, in particular K.Assamagan, R.Kinnunen, S.Nikitenko, M.Vos

A/H and A/H decays at the LHC Outline of the talk: The LHC and ATLAS,CMS MSSM A/H Higgs production...

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