1. Olivier RavatLes Houches/June 3rd 20031 Higgs associated production at LHC : Thecase Olivier Ravat, Morgan Lethuillier IPN Lyon Les Houches 2003 : Physics at TeV Colliders

2. Olivier RavatLes Houches/June 3rd 20032 Production at LHC Production at LHC Small NLO Corrections: According to V2HV (M.Spira) a K factor of 1.3 can be applied. NLOLO MH σ (pb)

3. Olivier RavatLes Houches/June 3rd 20033 The pp lνγγ channel Signal Signature :2 hard photons reconstructing to the Higgs mass Signature : 2 hard photons reconstructing to the Higgs mass 1 charged lepton and missing P T 1 charged lepton and missing P T Processes with such a final state :

4. Olivier RavatLes Houches/June 3rd 20034  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 M H  Increases the coverage of MSSM(M A,tg β ) 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. Motivations

5. Olivier RavatLes Houches/June 3rd 20035 Generation of the physics events  M H = 120 GeV  Structure function: CTEQ 5L  Signal generated with Pythia 6.2 and CompHEP 41.10 in order to perform some cross-checks,  Backgrounds generated with CompHEP 41.10

6. Olivier RavatLes Houches/June 3rd 20036 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 : Cuts pTγ1pTγ1pTγ1pTγ1 > 20 GeV P T γ 2 > 20 GeV pTlpTlpTlpTl ΔR(γ,l) >0.3 |η(γ,l)| <2.7 σ(pp γ γlυ).10 5 pb Signal35.96 Background1174.5

7. Olivier RavatLes Houches/June 3rd 20037 Kinematics for the signal, Pythia and CompHEP PythiaCompHEP PythiaCompHEP PythiaCompHEP PythiaCompHEP

8. Olivier RavatLes Houches/June 3rd 20038 Kinematics for the signal, Pythia and CompHEP PythiaCompHEP PythiaCompHEP

9. Olivier RavatLes Houches/June 3rd 20039 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.

10. Olivier RavatLes Houches/June 3rd 200310 Tuning Pythia parameters ParameterMeaningDefaultTune MSTP(81) Multiple parton interaction : on 11 MSTP(82) Varying impact parameter; hadronic matter overlap consistent with a double gaussian distribution, with a smooth turn-off=PARP(82) 14 PARP(82) 1.9 GeV 2.0 GeV PARP(83) Double Gaussian : fraction of hadronic matter within PARP(84) 0.50.5 PARP(84) Double Gaussian : fraction of the overall hadron radius containing the fraction PARP(83) of the total hadronic matter. 0.20.4 PARP(85) Probability that the MPI produces 2 gluons with color connections to the nearest neighbour. 0.330.9 PARP(86) Probability that the MPI produces 2 gluons either as in PARP(85) or as a closed gluon loop. 0.660.95 PARP(89) Reference energy E 0 1 TeV 1.8 TeV PARP(90) Determines the energy dependance of the cut-off P T0 as follows : P T0 (E CUT )=P T0 (E CM /E 0 )ε with E=PARP(90) 0.160.25 PARP(67) Scale factor that determines the maximum parton virtuality for space-like showers. 14 (Rick Field settings)

11. Olivier RavatLes Houches/June 3rd 200311 CMSJET parameters Noise in the ECAL barrel : Noise in the ECAL endcaps: 0.5% of dead cells. 30 MeV 0.5% 150 MeV p T cut for photons : 20 GeV p T cut for electron : p T cut for muon : 10 GeV

12. Olivier RavatLes Houches/June 3rd 200312 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 events for 1 year at HL: 5 GeV p T >2 GeV Signal : 14 Background : 214 Signal : 14 Background : 214 ΔR =0.3

13. Olivier RavatLes Houches/June 3rd 200313 Results with ~17.3 events/bunch crossing CMS : 100 fb -1

14. Olivier RavatLes Houches/June 3rd 200314 Results with ~17.3 events/bunch crossing CutCut CMS : 100 fb -1

15. Olivier RavatLes Houches/June 3rd 200315 Results with ~17.3 events/bunch crossing Nice, but does not yet include reducible background… After one year at high luminosity, cuts of 55 GeV on the hard photon and 30 GeV on the soft one : In a mass window of 118.6<M γγ <121.4 we get CMS : 100 fb -1

16. Olivier RavatLes Houches/June 3rd 200316 Conclusions and perspectives The WH lνγγ 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 M H : the charged lepton kills the pointing contribution on ΔM H ; It would be a “rescue channel” in case of maximal stop mixing.

17. Olivier RavatLes Houches/June 3rd 200317 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