MSSM Higgs Bosons decaying in SUSY cascade with ATLAS

Simonetta Gentile, Charged Higgs, 2008,Uppsala, Sweden.

MSSM Higgs Bosons decaying in SUSY

cascade with ATLAS

Simonetta Gentile Università di Roma, La Sapienza, INFN

on Behalf of ATLAS Collaboration


OutlineMotivationMSSM Higgs in SUSY cascade search

limits at LHCBench mark pointsDetection MSSM Higgs in ATLASAnalysis: first results on neutral & charged

Higgs discovery potentialConclusionsThe results presented are preliminary.


SUSY & Higgs interplayIf SUSY kinematically accessible, then real production of

sparticles.

Higgs can decay directly to or come from decay of SUSY particles

Associated production modes: e.g, squark-squark-Higgs SUSY particles suppress or enhance loop induced

production or decays Higgs into sparticle decay modes can compete with SM modes:

H/A →0

202→ 4 ± X

H± →±

1→ 3 ± X

[1] ATLAS Coll., ATLAS detector and Physics Perfomance, Vol.2 p766[2] F. Moortgat, S. Abdullin, D. Denegri”. hep-ph/0112046[3] M.Bisset, F. Moortgat and S. Moretti “Eur.Phys.J.C30:419-434,2003.[4] C. Hansen, N. Gollub, K. Assamagan, T. Ekelof Eur.Phys.J.C44S2:1-9,2005.

[5] CMS Coll., CMS detector and Physics Perfomance, Vol.1

Pioneering papers:


Signature

4 isolated leptons (e,)+ ET miss

powerful signature against theSM + SUSY backgrounds at LHC

Assume a classical production Mechanism

Decays


A/H susy decaysA,H →

2,3,4 0

2,3,4→4 ±+ Emiss T

A,H →+2-

1,2 →4 ±+ Emiss T

M.Bisset,N.Kersting,F.Moortgat,S.Moretti,arXi:0709.10029[hep –ph]

=eμ

(pp →H/A) Br(A,H →4 ±+N)

tan = 20 MA=500GeV

M2[

GeV

]

[GEV]

202

0

3,403,4

0


Search in a LHC detector

Representive points studied: MSSM representative Points MSugra representative Points

Discovery potential in a typical LCH detector investigated with this selections:

4 leptons > 7.4 GeV

lepton Isolation 2pairs of opposite sign |MZ ±10 GeV| veto GeV

< 80 GeV

jet < 50 GeV

Point A M0=125 GeV tan=20Point B M0=400 GeV tan=20M½=165GeV sign()=+1 A0=0


Reach for MSSM Higgs bosons in 0

2,3,402,3,4or 1,2

+2- pairs

Point 1 MA=500 GeV tan=20M1=90GeV M2=180 GeV =-500GeVMl=M= 250GeV mg=Mq=1000GeV

Point 2 MA=600 GeV tan=35M1=100GeV M2=200 GeV =-200GeVMl=150GeVM= 250GeV mg=800GeV Mq=1000GeV

M.Bisset,N.Kersting,F.Moortgat,S.Moretti,arXi:0709.10029[hep –ph]


Choice of Bench mark points

mtop= 175 GeV mb= 4.25 GeV tan β= 10 mA= 500 GeV Msquark= 1 TeV Atau= 0 Aℓ= 0 mℓ=mτsoft= 250 GeV

“High” branching ratio in

02,3,4

“High” branching ratio in0

2 → 01 + -

To choose representative points in the search A/H→i

0i0→ 4

The following characteristics


Branching ratio

M2 = 180 GeV = -500 GeV

Point1

M2 = 200 GeV = -200 GeV

Point2 Point2

<0


Br( 2

0 →

10 2

)

Br( 2

0 →

10 2

)

Br(

A/H

→ 2

0 20 )

Br(

A/H

→ 2

0 20 )

A/H→202

0→101

0 4 negative


Sample of events

~

~,~

Standard Model Background•bbZ → 4 • tt → 4 •ZZ → 4

Reference points: ( same BKMM)1) MSSM Point 1 MA=500 GeV tan=202) MSSM Point 2 MA=600 GeV tan=353) MSUGRA Point A tan=204) MSUGRA Point B tan=20

Signal H → 4 A → 4

MSSM Background

• → 4

..

~~/~,~~

~,~

~,~

cctH

gq

gq


Point 1 [GeV]

Point 2 [GeV]

Point A [GeV]

Point B [GeV]

MA 500.0 600.0 257.4 439.5

MH 503.4 603.9 259.1 442.5

89.7 93.9 61.1 62.3

176.3 155.5 109.4 111.9

507.0 211.9 235.9 241.9

511.0 262.6 259.8 265.4

176.3 153.1 108.7 111.6

514.0 263.6 260.2 265.9

01

~02

~03

~04

~

1~

2

~

MSSM particle masses


ATLAS detector response has been full simulated taking into account the effetcts of energy loss, multiple scattering and showering in the detector through ATHENA interface.

SM background cross section , as signal are considered at LO approximation

Study at Lint =300 fb-1 scenario .( → Lint =100 fb-1 ) The statistics used corrisponds to AT LEAST this

luminosity. In some delicate points the statistics is increased up a factor 2, with exception tt background.

Simulation & reconstruction in ATLAS detector


Muons

For A Sample in events A/H→2

020→ .......

preliminary

preliminary

preliminary


Electrons & E Tmiss

For A Sample in events A/H→2

020→ e...... preliminary

preliminarypreliminary

preliminary


ZZ and tt samplepreliminary

preliminary

preliminary


Selection 1 part

Preselection cuts: Trigger one:1 electron isolated E > 22 GeV or a isolated > 20 GeV (120i or 1e22i)pT

> 5GeVIsolation pT< 6 GeV in cone R=0.2Medium electron definition considered

Selection Lepton pair charge and flavour constrains 1

-1+2 2

+

Generation Event Filter: 4 → and || < 2.7, pT > 5GeV

reconstru

ction


Selection 2 part

~~/~,~~

~,~

gq

gq

~~/~,~~

~,~

gq

gq ~,~

Selection cuts:Impact significance parameter for 4 and e > 6pT

1 > 8 GeV 35 GeV< ET

miss < 130 GeVZ veto : |Minv (+ -) –Mz| > 6 GeV

Zbb, ZZ

1st high energy lepton pT1, 2nd high energy lepton pT

2 25 GeV < pT

1 < 110 GeV pT

1 < 100 GeV and pT2 > 60 GeV

pT2 > 60 GeV ( only Set2 & SetA)

tt

PTMin > 20 GeV

Njet 5 PTjet >20 GeV (with 1 track)

Minv (+ - + -) < 125 GeV (SetA)

~~/~,~~

~,~

gq


Reference Point 1 Sample Particle e

[pb]

BR4lepNev

(300 fb-1)

Sample

Used

00)

N Sel

(300 fb-1)

A 1.18 0.0051 1800 2250

30

H 1.16 0.0049 1700 2500

14

Zbb 60.5 0.00942 171000 44500 2

tt 500 0.00728 1092000 570555 82

ZZ 0.21 0.219* 13500 115700 10

1.49 0.034 15000 17000 1

0.15 0.15 1100 1500 44

2.97 0.019 1700 2500 7

0.136 0.0078 315 500 0

SM

MS

SM

Back

SIG

NA

L

* x br without box diagram 34.8 fb (weight 1.49)

..

~~/~,~~

~,~

~,~

cctH

gq

gq


Set1:Cross Section & Br A,H

Br4

( || < 2.5, pT > 5GeV) x Br 4

A A A

H H H

preliminary preliminary preliminary


Background effective cross section x Br 4

x Br 4

x Br 4

x Br 4

gq ~,~~,~

~~/~,~~ gq..cctH

preliminary preliminary


Set 1-MSSM Background

..

~~/~,~~

~,~

~,~

cctH

gq

gq

x Br 4 not depending from MA, as

expected. The events processed at each tan at MA= 500 GeV are used.

tH events studied at each point (tan,MA)

Explored region:

•tan 5,8 and 10-40 step 5•MA 375-900 GeVstep 25 GeV


Set 1 Discovery plots at L = 300 fb-1

02

02

~~ 0

20

2~~



Set 1 Discovery plots at L = 100 fb-1

02

02

~~ The discovery region for A/H→2

020→4 + ET

miss

can be accessible only after L=300fb-1.

No clear discovery possibilty at lower luminosity

The background are mainly ZZ and slepton pair and tt pair.

preliminary


Set 2 :Cross Section & Br A,H

Br4

( || < 2.5, pT > 5GeV) x Br 4

A A A

H H H

preliminary preliminary preliminary


Background effective cross section

• low tan regionSignal dominated A→2

020

tH background not anymore neglegible LL background neglegible

x Br 4

..cctH A

H

x Br 4

x Br 4

tan =3

tan =3

preliminary

preliminary

preliminary

Explored region:•Tan 3 and 5-50 step 5•MA 375-900 GeVstep 25 GeV


Set2 Discovery plots at L = 300 fb-1

02

02

~~ 043

0 ~~ 043

0 ~~ 0

20

2~~



Set2 Discovery plots at L = 100 fb-1

02

02

~~ 043

0 ~~ 0

20

2~~ 0

430 ~~



Conclusion of Set2The detection region ofA/H→0

2,3,4 02,3,4→4 + ET

miss

andA,H →+

2 -1,2 →4 ±+ E T

miss

is accessible also with L=100fb-1.The remaing background are mainly ZZ and tt pair,

direct tH± production is not neglegible.

Preliminary study also on MSUGRA has been performed, SetA, In this scenario the copious background is tt pair

The point at MA= 257 GeV and tan = 20

has been studied . The significance achieved is after L =300fb-1 is 5 .

~~/~,~~,~,~

gq


Charged Higgs involvement

Final state: Only 3 lepton +another lepton from a top decay

Is not the best final state for a dedicated H- search…..


Charged Higgs role

The range of discovery is enlarged, extending the search to all MSSM Higgs(H/A/H±) respect to neutral H/A..

preliminary


Charged Higgs role

The range of discovery is enlarged, extending the search to all MSSM Higgs(H/A/H±) respect to neutral H/A..



Conclusion Discover potential study in MSSM neutral Higgs boson, A/H→

4 + ETmiss in ATLAS has provided the first results.

A scan in (MA,tan plane with the the points dominated by 2

020 decays (Set1) and 2,3

02,3,40

decays (Set2) has been performed using full simulation of ATLAS detector

With Set1 parameters the possibilty of discovery of neutral MSSM Higgs are after L=300 fb-1,

With Set 2 the perspective are more encouraging even with L=100fb-1

The inclusion of charged Higgs decay extends the possibility of discovery a MSSM Higgs even with L=100fb-1.

I would like to thank Stefano Moretti and Filip Mortgart for discussions and informations.

Many thanks to Karl Jakobs , who coming back from Uppsala2006 suggested me this interesting topic. MANY THANKS to JUNICHI TANAKA

Documents

MSSM Higgs Bosons decaying in SUSY cascade with ATLAS