Detect MSSM neutral Higgs bosons at LHC
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Detect MSSM neutral Higgs bosons at LHC. Simonetta Gentile Università di Roma, La Sapienza, INFN. Outline. Motivation Supersymmetric (SUSY) Higgs Experimental status Search at LHC,what can be done: few examples Conclusions. Minimal Super Symmetric Model.

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Detect MSSM neutral Higgs bosons at LHC

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Detect mssm neutral higgs bosons at lhc

Detect MSSM neutral Higgs bosons at LHC

Simonetta Gentile

Università di Roma, La Sapienza, INFN

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Outline

Outline

  • Motivation

  • Supersymmetric (SUSY) Higgs

  • Experimental status

  • Search at LHC,what can be done:

    few examples

  • Conclusions

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Detect mssm neutral higgs bosons at lhc

Minimal Super Symmetric Model

The MSSM is the most investigated extension of SM provides:

  • The unification of coupling constants

  • SUSY provides a ColdDarkMatter candidate

  • Three neutral Higgs bosons: A, CP-odd, andCP-evenH,hthe lightest. Two charged H+, and H-.

  • Large loop corrections depend on SUSYparameters

  • Unconstrained MSSM has huge number (105) of parameters

  • in addition SM ones, making any phenomenogical analysis

  • very complicated

  • A simplified version at some GUT scale: CMSSM/mSUGRA

    Most of phenomenogical analysis models are based on that.

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Mssm parameters constrains

MSSM parameters constrains

Phenomenology decribed at Born level bytan b ,mA

  • Msusy,sfermion mass at EW scale

  • M2, SU(2)L gaugino mass at EW scale

  • m, supersymmetric Higgs boson mass parameter.

  • tan b, the ratio of the two Higgs fields doublets

  • A0, a universal trilinear higgs-squarks coupling at EW scale. It is assumed to be the same for up-type squarks and for down types quarks.

  • mA, mass of CP-odd Higgs boson.

  • Mgluino, it affects loop corrections for stop and bottom

  • couplings: gMSSM = ξ · gSM

    • no coupling of A to W/Z

    • large tanb: large BR(h,H,Att,bb)

a: mixing angle between CP even Higgs bosons

(calculable from tanb and MA)

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Masses

  • For MA< 135 GeV (Mhmax scenario)

  • The ligth MSSM Higgs is SM-like

    MA≈ Mh

Masses

  • For MA> 150 GeV (decoupling limit)

    The heavy MSSM Higgsess:

    MA≈ MH ≈MH±

Pythia 6.226

FeynHiggs2.2

Pythia 6.226

S.G, H.Bilokon,V.Chiarella,G.Nicoletti

ATL-PHYS-PUB-2007-001

Sven Heinemeyer

Atlas meeting 29.01.2008

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Detect mssm neutral higgs bosons at lhc

MSSM Higgs Production

V*=W/Z

  • Main production mechanism ~SM

  • For high and moderate tanb theproduction with b quarks is enhanced

  • For mA >>mZ A/H behave very similar →decoupling region

  • A, H, H± cross section ~tanb2

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Production cross section

Production cross section

  • At small tanb gg→h,H,A dominant

  • Vector boson fusion process

  • pp→qq→qq+WW/ZZ→qq+h/H

  • important at m h~ m hmax

  • Higgsstrahlung neglegible

  • At high tanb associatedb quarks production dominates

  • pp → bb →h/H/A+ bb

=h,H,A

Abdelhak Djouadi arXiv:hep-ph/0503173v2 (2005)

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Branching ratio

Branching ratio

  • Decoupling region

  • MA≥ 150 GeV tanb ≈30

  • or MA≥ 400-500 GeV tanb=3

Production rate

  • Decay bb dominates,

  • tt lower background

  • weaker sensitivy on

  • SUSY parameters

Abdelhak Djouadi arXiv:hep-ph/0503173v2 (2005)

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Branching ratio1

Branching ratio

  • Intense coupling region tanb ≈30 MA~ 120-140 GeV

  • Coupling to W,Z up quarks suppressed

  • Coupling down quark (b) and t enhanced

  • Decay bb,tt dominates

  • Decay mm possible

Abdelhak Djouadi arXiv:hep-ph/0503173v2 (2005)

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Benchmark scenarios

Benchmark scenarios

  • mhmax scenario

    It allows the maximum value for mh(Xt =2MSUSY).

    It can be obtained conservative tanb exclusion bounds

  • no-mixing scenario

    No mixing in scalar top sector (Xt =0)

  • small aeff scenario

    Hb coupling~ sinaeff/ cos b can be zero: aeff→0:

    Main decay mode vanishes, important search channel vanishes

  • gluophobic Higgs scenario

    hgg coupling is small: main LHC production mode vanishes.

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Detect mssm neutral higgs bosons at lhc

MSSM

Constrained:

  • Two Higgs doublets →h0, H, A, H+, H-

  • Three neutral Higgs bosons: H,A, CP-odd, andh

    the lightest CP-even.

  • Large loop corrections depend on SUSYparameters (expecially stop): Msusy, M2, m, tan b, A,mA,mgluino

  • Xt~ A= 61/2 Msusy, |m|<< Msusy for maximal top mixing

  • Xt=0 no mixing scenario

  • Measurement of Higgs masses, coupling and Br  test of theory

  • Varying mAtanβ,keeping all other SUSY parameters fixed.

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Lep legacy

Low tanb is not completely

excluded: search for LHC

with pp->A; A->Zh, gg, tt

LEP legacy

Mt [GeV]=

169.3

174.3

179.3

183.0

Excluded:

(mhmaxscenario)

mh>92.8 GeV mA>93.4 GeV

tanb 0.7 2.0

Excluded

MH±>78.6 GeV

High tanb area for search at LHC

with pp->bb h/ H/A

h/H/A->mm, tt decays

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.

Eur.Phys. J C 47, 547


Exclusion limits @ 95 cl

Tevatron results

Exclusion Limits @ 95% CL

CDF & D0 have not observed a Higgs signal yet

Interpretation of the limits

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.

Anton Anastassov Aspen 2008


Quest strategy

Quest & strategy

Look for MSSM bosons in the entire parameter space.

  • Using the same analysis strategy for SM ,MSSM

  • Among all channels studied from ATLAS and CMS focus on:

  • pp→bb h/ H/ A– moderate and high tanb

    • h/ H/ A ->mm

    • h/ H/ A ->tt

  • pp→A at low tanb

    • A→Zh

      • Z→  (=e, m)

      • h→bb

  • pp→A/H→ c02,3,4 c02,3,4

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Light higgs boson

Light higgs boson

L =30fb-1

h

  • VBF dominates at low luminosity

  • Large space covered by several

  • channel

  • Region around mh~ 95GeV

  • difficult

  • h→mm channel at low masses

h/A/H

CMS TDR

L =300fb-1

NOT UPDATED

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.

ATLAS


Bb h a bb mm

bb h/A→bbmm

  • Associated h/A/H production with b-jets → large s

  • The adavange of tt channel due to the mass is counterbalanced by difficulty of identify t decays

  • (smaller detector acceptance, n in final state)

  • Excellent m resolution of detectors

Production rate

h→mm and h →tt

signal

background

S.G., H.Bilokon, V.Chiarella,G.Nicoletti, Eur.Phys. J. C. 52, 229-245 (2007)

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Bb h a mm

Atlas

bb→h/Amm

MA=110.31 GeV, Mh= 110 GeV, tanb=45

Atlas : tanb 15-50

mA 95-130 GeV

  • 2 m pT>20GeV

  • 2 jets pT>10GeV

  • 1 b-jet (pT>15GeV)

  • Mmm

  • m-isolation,no hadronic

  • activity

  • Background bbZ→bbmm

  • tt →bbmm

  • ZZ→bbmm

Full detector simulation

Corresponding to L=300fb-1

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Background evaluation

Atlas

Background evaluation

  • bbZ→bbmmlarge cross section (s≈ 22.8 pb) large

    theoretical uncertainties (≈ 25%)

    Proposed data driven method based on bbZ→bbee

  • Rate of signal suppresed by

    Background same rate:

    same production diagram, and lepton universality

    different inner bremsstrahlung and detector reconstruction

Ratio stable & without large corrections factor

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Detect mssm neutral higgs bosons at lhc

Atlas

h/A/H significance reach

L=300 fb-1

L=10 fb-1

L=30 fb-1

Mhmax scenario

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Discovery contours

Atlas

Discovery contours

5 s at L =30 fb-1

---- no systematic

H+A

h+A

h+H+A

ATLAS

CMS TDR

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Others channel t decays

Others channel:t decays

  • Full leptonic: bbH→bbtt→em+ETmiss

  • Lower rate than full hadronic or hadronic/lepton Br(t→lnn) ~0.17

  • Clean signal and easy trigger

  • Higgs mass reconstruction using collinear approxomation

  • Approssimation method requires excellent missing ETresolution

  • Main background:Z+jet,ttbar,Zbb

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Higgs search in a zh channel

Higgs Search in A→ Zh channel

  • Low tanb region

  • Final state Z→ ll (l = e,m) h →bb

  • Low tanb Mz+mh≤ MA≤2mtop (highest Br)

  • Depends strongly on MSSM parameters

  • Main backgrounds: Zbb,ttbar and Z+jet

  • Systematic can be important

At Large value of M2 and m

can dominate A→cc

L=30fb-1

Z+jet

tt

5s contour

Zbb

signal

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Summary of cms reach in m a tan b

Summary of CMS reach in MA-tanb

Associated production

Inclusiveproduction

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Detect mssm neutral higgs bosons at lhc

ATLAS reach for MSSM Higgs bosons

Atlas

L=300fb-1

Not updated

  • whole plane covered in CP conserving benchmark scenarios

  • significant area where only h is observable

  • At least one Higgs boson observable

  • significant area where only h is observable

  • Difficult to distinguish from SM

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Lhc searches for mssm higgses

LHCsearches for MSSM higgses

Other discovery channels possible .. :

  • h→ gg inclusive production and production in association tth final states

  • h,A,H → mm inclusive and bb associated

  • H →bb in association with bb

  • h,A,H →tt with 2 ,  +t-jet and 2 t-jet final states.

  • .....

  • gb → t H±, H± →tn

  • gg →tt → H± bWb

  • Note:

  • They only include SM-particles to Higgs interactions

  • This assumes no interaction between Higgs & sparticle sectors:

  • i.e., SUSY mass scales are heavy

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Susy higgs interplay

SUSY & Higgs interplay

If 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 →c02c02→ 4 ± X

H± →c02c±1→ 3 ± X

Pioneering papers:

[1] F. Moortgat, S. Abdullin, D. Denegri”. hep-ph/0112046

[2] M.Bisset, F. Moortgat and S. Moretti “Eur.Phys.J.C30:419-434,2003.

[3] C. Hansen, N. Gollub, K. Assamagan, T. EkelofEur.Phys.J.C44S2:1-9,2005.

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Access to low tan b with a h c 2 0 c 2 0 4 e t miss

A/H susy decays

Access to low tanb with A/H->c20c20->4  + ETmiss

CMS

Chosen points in mSUGRA

  • Background

    • SUSY, SM: tt, ZZ, Zbb

  • Selections:

    • Lepton isolation

    • Jet veto

    • ETmiss, pT4l < 80 GeV

    • Z veto

Point C after selections

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Access to low tan b with a h c 2 0 c 2 0 4

A/H susy decays

Access to low tanb with A/H->c20c20->4 

CMS

tanb = 5 150<m½ <250

30<m0 <120

tanb = 10 150<m½ <250

m0 <120

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


A h susy decays

A/H susy decays

A,H →c02,3,4 c02,3,4→4 ±+ EmissT

A,H →c+2 c-1,2 →4 ±+ EmissT

=eμ

s(pp →H/A) Br(A,H →4 ±+ N)

tanb = 20

MA=500GeV

M2[GeV]

c20c20

c3,40c3,40

m [GEV]

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

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Search in a lhc detector

Search in a LHC detector

Point A M0=125 GeV tanb=20

Point B M0=400 GeV tanb=20

M½=165GeV sign(m)=+1 A0=0

  • Representive points studied:

  • MSSM representative Points

  • MSugra representative Points

  • Discovery potential in a typical LCH detector investigatedwith this selections:

  • 4 leptons |h |< 2.4 ,ET > 7.4 GeV

  • lepton Isolation

  • 2pairs of opposite sign

  • |MZ ±10 GeV| veto

  • 20 GeV<ET < 80 GeV

  • ETjet < 50 GeV

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Reach for mssm higgs bosons in c 0 2 3 4 c 0 2 3 4 or c 1 2 c 2 pairs

Reach for MSSM Higgs bosons in c02,3,4c02,3,4or c1,2+c2- pairs

Point 2 MA=600 GeV tanb=35

M1=100GeV M2=200 GeV m=-200GeV

Ml=150GeVMt= 250Gev mg=800GeV

Mq=1000GeV

Point 1 MA=500 GeV tanb=20

M1=90GeV M2=180 GeV m=-500GeV

Ml=Mt= 250GeV mg=Mq=1000GeV

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Detect mssm neutral higgs bosons at lhc

Discovery region for H/A →c02,3,4c02,3,4c1,2+c2- Set 1 superimposed to Atlas discovery reach with SM particles

1.H → ZZ* →4 

2.tH →bH+,H+ →tn +cc

3.tth ,h →bb

4.h →gg

5.bbH/A, H/A →bb

6.H+ →tb +c.c.

7.H/A →m+m-

8.H/A →t+t-

9.gb →tH+, H+ →t+n

10.H →hh →bbgg

11. A →Zh →-bb

12.H/A →tt

SM decays limit derived with hypotesis that H/A can’t decay in SUSY particles.DIFFERENT parameter!!

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Detect mssm neutral higgs bosons at lhc

Discovery region for H/A →c02,3,4c02,3,4c1,2+c2- Set 2 superimposed to Atlas discovery reach with SM particles

1.H → ZZ* →4

2.tH →bH+,H+ →tn +cc

3.tth ,h →bb

4.h →gg

5.bbH/A, H/A →bb

6.H+ →tb +c.c.

7.H/A →m+m-

8.H/A →t+t-

9.gb →tH+, H+ →t+n

10.H →hh →bbgg

11. A →Zh →bb

12.H/A →tt

SM decays limit derived with hypotesis that H/A can’t decay in SUSY particles.DIFFERENT parameter!!

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


Conclusions

Conclusions

  • Atlas & CMS are preparing for first collision data

  • Discovery potential of MSSM Higgs boson

    has been estimated by ATLAS and CMS.

  • A early discovery of a neutral MSSM boson in some

    channels (e.g.bb h/A→mm ) looks possible with integrated luminosity =10 fb-1 , i.e. after only one year of data taking.

  • First data has the possibilty to exclude/or confirm the entire MSSM

  • Others decay channel (as c20 c20) can be explored later for

    unexplored region of parameter plane.

Simonetta Gentile, Les Rencontres de Physique de la Vallée d’Aoste, 29 February.


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