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Higgs associated production at L H C :. The. case. Olivier Ravat , Morgan Lethuillier IPN Lyon. Les Houches 2003 : Physics at TeV Colliders. Production at L H C. Small NLO Corrections: According to V2HV (M.Spira) a K factor of 1.3 can be applied. σ (pb). NLO LO. MH.

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Higgs associated production at l h c

Higgs associated production at LHC :

The

case

Olivier Ravat, Morgan Lethuillier

IPN Lyon

Les Houches 2003 : Physics at TeV Colliders

Les Houches/June 3rd 2003


Higgs associated production at l h c

Production at LHC

Small NLO Corrections:

According to V2HV (M.Spira) a K factor of 1.3 can be applied.

σ (pb)

NLO

LO

MH

Les Houches/June 3rd 2003


Higgs associated production at l h c

The pp lνγγchannel

Signature :2 hard photonsreconstructing to the Higgs mass

1 charged leptonandmissing PT

Processes with such a final state :

Signal

Les Houches/June 3rd 2003


Higgs associated production at l h c

Motivations

  • This channel is far cleaner than the usual H γγ.

    Less dependant on calorimeter resolution.

  • Vertex reconstruction is easy, thanks to the charged lepton better measurement of MH

  • Increases the coverage of MSSM(MA,tgβ) parameter space (D.Denegri, R.Kinnunen CMS-NOTE 96-091); interesting for the 2HDM(I).

  • History : A study has been performed in 1997 at the generator level (M.Dubinin et Al. CMS NOTE 1997/101) and we would like to update the study with a detector simulation.

Les Houches/June 3rd 2003


Higgs associated production at l h c

Generation of the physics events

  • MH = 120 GeV

  • Structure function: CTEQ 5L

  • Signal generatedwithPythia 6.2andCompHEP 41.10in order to perform some cross-checks,

  • Backgrounds generated with CompHEP 41.10

Les Houches/June 3rd 2003


Higgs associated production at l h c

Cross-sections of signal and irreducible background

Total NLO cross-section for WH production : 2 pb

In order to assure an efficient production we imposed some generator level cuts :

Les Houches/June 3rd 2003


Higgs associated production at l h c

Kinematics for the signal, Pythia and CompHEP

Pythia

CompHEP

Pythia

CompHEP

Pythia

CompHEP

Pythia

CompHEP

Les Houches/June 3rd 2003


Higgs associated production at l h c

Kinematics for the signal, Pythia and CompHEP

Pythia

CompHEP

Pythia

CompHEP

Les Houches/June 3rd 2003


Higgs associated production at l h c

From CompHEP 4-vectors to a simulated final state

  • Using cpyth_for_CMSIM (A. Sherstnev) : hadronization and fragmentation with Pythia.

  • Output : HEPEVT ntuple compatible with CMSJET and CMSIM.

  • Pythia tuned to fit the underlying event and the minimum bias using the CDF data, then extrapolation to LHC energies.

Les Houches/June 3rd 2003


Higgs associated production at l h c

Tuning Pythia parameters

(Rick Field settings)

Les Houches/June 3rd 2003


Higgs associated production at l h c

CMSJET parameters

30 MeV

Noise in the ECAL barrel :

Noise in the ECAL endcaps:

0.5% of dead cells.

150 MeV

0.5%

pT cut for photons :

20 GeV

pT cut for electron :

20 GeV

pT cut for muon :

10 GeV

Les Houches/June 3rd 2003


Higgs associated production at l h c

CMSJET parameters

No charged particle with in a cone ΔR =0.3 around leptons and photons.

No cluster with more than in the calorimeters around leptons and photons.

Number of selected eventsfor 1 year at HL:

pT>2 GeV

ΔR =0.3

5 GeV

Signal : 14

Background : 214

Les Houches/June 3rd 2003


Higgs associated production at l h c

Results with ~17.3 events/bunch crossing

CMS : 100 fb-1

CMS : 100 fb-1

Les Houches/June 3rd 2003


Higgs associated production at l h c

Results with ~17.3 events/bunch crossing

CMS : 100 fb-1

CMS : 100 fb-1

Cut

Cut

Les Houches/June 3rd 2003


Higgs associated production at l h c

Results with ~17.3 events/bunch crossing

After one year at high luminosity, cuts of 55 GeV on the hard photon and 30 GeV on the soft one :

CMS : 100 fb-1

In a mass window of 118.6<Mγγ<121.4 we get

Nice, but does not yet include reducible background…

Les Houches/June 3rd 2003


Higgs associated production at l h c

Conclusions and perspectives

The WHlνγγ channel can hardly be considered as a discovery channel but it’s very clean (almost free from background!)

It also allows a more precise measurement of MH : the charged lepton kills the pointing contribution on ΔMH;

It would be a “rescue channel” in case of maximal stop mixing.

Les Houches/June 3rd 2003


Higgs associated production at l h c

What’s next?

The processing of 4-vectors with CMSIM is on its way in view of full simulation and reconstruction with ORCA.

The generation of the ZH and ttH cases is performed both for signal and background (analysis still to be done).

Reducible backgrounds are being produced

Les Houches/June 3rd 2003


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