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Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data

Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data. N. Chanon, S. Gascon, M. Lethuillier (IPNL – Université Claude Bernard Lyon 1) ‏ 05/03/10. I – Results in H->ZZ* 10 TeV paper II – Inner brem recovery in CRAFT III – Fake rate studies.

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Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data

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  1. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data N. Chanon, S. Gascon, M. Lethuillier (IPNL – Université Claude Bernard Lyon 1)‏ 05/03/10 I – Results in H->ZZ* 10 TeV paper II – Inner brem recovery in CRAFT III – Fake rate studies

  2. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data The MultiBrem IB recovery technique Recovery technique « MultiBrem4l » (one of many techniques tried)‏ Idea : recovering a variable number of IB per event Parameters : Cone R<0.25 (best results, with 0,1<R<0,5 tested)‏ 2 photons max per lepton (1<N<3 tested)‏ 3 photons max per event (1<N<8 tested)‏ Photons with pt>3GeV (1,3,5,10,15 tested)‏ Algorithm (described in CMS AN 2008-50): - Select the four leptons - Same flavour leptons must be of opposite charge. - Sort the possible lepton-photon pairs by R. Recover the photons in order of increasing R. - We select at maximum 2 photons per lepton, and 3 photons per event. - The algorithm stops when there is no photon left or when R>0,25.

  3. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data The MultiBrem IB recovery technique • Photoncleaning : • - |<2.5 • - Re-run the photon producer changing the SC Et threshold to 1 GeV • - Remove photons duplicata of the electron collection (those having the same supercluster)‏ • Inner Brem Recovery : • « PTDR technique » : • At maximum 1 photon per event, the closest inside a cone R=0.3 • « MultiBrem technique » : • At maximum 3 photons per event, 2 per lepton max, the closest to leptons inside a cone R=0.25 having pt>3 GeV • « MultiBrem KeepCloseToZ » technique : • The same as MultiBrem, but the recovery is not applied to Z with |Mll-Mz|< SigmaZ, SigmaZ = 3 GeV. Idea is avoiding overcorrection, do not throw out of peak events which already have a good reconstructed Z mass. SigmaZ is a parameter determined experimentally (SigmaZ=0..5 tried)‏

  4. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data I – Results in H->ZZ* 10 TeV paper after preselection Rcut=0,25 Height/Sigma : -3.7% +1.8% +6.0% Generator level, 18 Higgs nominal mass. Pt_>3, Pt_e>5, Pt_>5 GeV IB are often collinear to the parent lepton Among the 3 techniques of IB recovery, Multi-Brem KeepCloseToZ technique gives the best results

  5. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data I – Results in H->ZZ* 10 TeV paper after complete selection background ZZ, Zbb and TT only In mean : +6.01% +2.29% +9.20% The improvement on significance due to IB recovery reaches 5% for mH>180 GeV. The performance is the best in 4mu channel, followed by 2e2mu. Improvement is at best very small in 4e channel.

  6. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data II – Inner brem recovery in CRAFT Magnetic field on : 3.8T Data CRAFT 08 used : /Cosmics/Commissioning08_CRAFT_ALL_V4_ecalSkim_fromRECO_ecalSkim_fromRECO_v3/RECO Gain 50 69912, 69902, 69892, 69874, 69850, 69800, 69788, 69750, 69491, 69482, 69475, 69464, 69438, 69364, 69357, 69351, 69343, 68958, 68949, 68926, 68665, 68500, 68483, 68288, 68286, 68279, 68276, 68264, 68141, 68129, 68124, 68100, 68094, 68021, 68000, 67977, 67818, 67810, 67645, 67573, 67557, 67548, 67544, 67541 Gain 200 66612, 66613, 66615, 66621, 66627, 66637, 66644, 66656, 66657, 66662, 66668, 66676, 66692, 66703, 66706,66709, 66711, 66714, 66716, 66720, 66722, 66732, 66733, 66739, 66740, 66746, 66748, 66752, 66756, 66757, 67128, 67139, 67141, 67145, 67147, 67838 MC CRAFT 09 used : Gain 50 : /CosmicMC_BON_10GeV_AllCMS/Winter09_COSMMC_22X_V6_v1/RECO Gain 200 : /CosmicMC_BON_10GeV_EcalG200/Winter09_COSMMC_G200V3_v1/RECO

  7. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data II – Inner brem recovery in CRAFT Photon selection Software : CMSSW_2_2_9 + EcalCosmicsTree in CaloOnlineTools/EcalTools/ Collections : RECO Objects : => global muons, CosmicBarrelSuperClusters, CosmicEndcapSuperClusters Selection on muons : - Pt > 10 GeV (required for consistency with generator level)‏ - phi < 0 (to have a good reconstruction of muons and photons in cosmics events)‏ - if several muons closer than dR<0.05 to each other, take the first - Assume muon is coming from interaction point (0,0,0)‏. To calculate the 4-momentum, compute the hit of the muons at entrance in ECAL (using TrackAssociator)‏ Selection on superclusters : - phi < 0 (to have a good reconstruction of muons and photons in cosmics events)‏ - Et > 1 GeV (SC requirement), E > 2 GeV (required by ECAL skim)‏ - If several photons with the same pt, take the first

  8. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data II – Inner brem recovery in CRAFT Photon selection APD200, Before matching Good agreement here also APD50, Before matching Good agreement between data and MC Matching muons-superclusters : - Match all muons and superclusters by increasing R - Loop on the pairs, starting from R=0. Then go to the next pair by increasing R. Keep the pair if the photon has not been already selected. - Then ask the muon to have |dz| < 50, |d0| < 100 The remaining photon/muon pairs are kept.

  9. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data II – Inner brem recovery in CRAFT Photon selection APD50 Before matching APD200 Before matching APD50 After matching APD200 After matching

  10. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data II – Inner brem recovery in CRAFT Results : APD50 APD 50 APD 50 (pt>10 because of a cut at gen level in MC sample)‏ Reasonnable agreement between data and MC. MC : /CosmicMC_BON_10GeV_AllCMS/Winter09_COSMMC_22X_V6_v1/RECO Lack of statistic. Pt of muons and photons is OK. The tail of dR distribution not reproduced by MC. APD 50 Small disagreement for dR>0.4, but OK elsewhere (very good for dR<0.4)‏

  11. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data II – Inner brem recovery in CRAFT Results : APD200 APD 200 APD 200 (pt>10 because of a cut at gen level in MC sample)‏ Good agreement, but lack of stat in the tail APD 200 Disagreement in the tail, but OK for dR<0.3 (not all the stat used for the data, because of a bug in EcalCosmicsTree)‏ MC : /CosmicMC_BON_10GeV_EcalG200/Winter09_COSMMC_G200V3_v1/RECO

  12. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data II – Inner brem recovery in CRAFT Conclusions for IB recovery in CRAFT - Pt of muons in data agrees with MC. - There is a quite good agreement for Pt of photons between data and MC. - R(,) is well reproduced by MC at small R, but there are not enough events in MC for R>0.5, and small disagreement starting from R>0.4. - IB recovery is applied in Z and ZZ samples with R<0.25, so that for our purpose the distribution is fine

  13. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data III – Fake rate studies Goal : evaluate inner brem fake rate from data Idea : use random cone direction technique MC used : H->ZZ samples at 10 TeV (reco objects in CMSSW_2_2_13)‏. Fake photons : - Monte-Carlo : a fake photon is defined as a photon obtained from IB recovery on 4-leptons chosen by H->ZZ analysis, which is not matched to a generator level IB photon inside a cone R(gen,reco) (R cones are function of , see next slide). - Random cone direction technique : a fake photon is defined as a photon obtained by IB recovery on 4 “fake” leptons with random direction. For R(random , real )>0.8, it is indeed expected that we are fare away from real IB which are mainly close to real photons.

  14. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data III – Fake rate studies R reconstruction resolution Determination of the cone size : - Use diphoton sample with no underlying event in CMSSW_3XX, privately produced thanks to H. Brun. Plot R(_gen,_reco closest) and get the angular resolution of the reconstruction as a function of . X % X % Not gaussian... Use effective sigma

  15. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data III – Fake rate studies R between superclusters resolution - Matched gen IBs can be already reconstructed in the electron cluster (remember most of FSR photons are emitted collinear to the lepton)‏ - To quantify this effect, look at 100 < HT < 250 QCD sample. Plot R(SC1,SC2) for all combinations, with pt_SC1>5 GeV and pt_SC2>1 GeV. X % There is a treeshold below which both SC are gathered in one. Use this treeshold to tag as fake the gen photons close from reco electrons

  16. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data III – Fake rate studies Fake rate definition : Number of fake photons (known by random cone technique or by MC truth) divided by the number of recovered photons with leptons chosen by the HZZ standard analysis. Cone size for MC truth matching : - Take Rcone() corresponding to 99.994% matching efficiency (~4s)‏ Cone size to tag as fake photons those which are too close from electrons : - Take Rveto() corresponding to the value for which 95% of superclusters pairs have a greater R (~2s)

  17. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data III – Fake rate studies Results : ZZ* background - The main background at the end of the analysis is ZZ*. It has the same kind of underlying event as H->ZZ*, and this is all what we will have in the beginning in term of events yields. - Random cone and MC almost agrees in the central barrel - Random cone and MC does not match in endcap...

  18. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data III – Fake rate studies Results : ZZ*->2e2 - Still problems with 2e2m

  19. Inner bremsstrahlung recovery for H->ZZ(*)->4l : control from data III – Fake rate studies Conclusions for the fake rate studies - With random cone direction technique, it is possible to estimate the IB fake rate from data. - H->ZZ and ZZ have the same IB fake rate obtained from random cone. - There are still problems with 2e2m. - Problems to understand what's going on in endcaps - One possibility : try (Dh,Df) instead of DR Conclusions for the control of IB recovery from data - The IB fake rate can be estimated from data with random cone technique - Data and MC are in agreement for inner brems in CRAFT data - Random cone could also be used on Minimum Bias events to estimate the impact of Pile-Up on inner brem recovery. - With 10pb-1, Look at R(,) in Z+ samples. Tune the « KeepCloseToZ » parameter SigmaZ from Z-> and Z->ee data.

  20. BACK-UP SLIDES

  21. Inner bremsstrahlung recovery for the process H->ZZ(*)->4l in CMSSW_2_2_X IB recovery at 10 TeV on signal and backgrounds Reconstructed Higgs mass (backgrounds)‏ After preselection, ZBB and TT higgs reconstructed mass are shifted to the right, but not ZZ. But remember that after the complete analysis, ZBB and TT are almost totally suppressed... Recovery on reprocessed photon with Et>1 GeV

  22. II – Inner brem recovery in CRAFT Photons energy in CRAFT data APD200 Before matching APD50 Before matching APD200 After matching APD50 After matching

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