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A preliminary study of the Vector Boson Fusion Process with FAMOS

Sara Bolognesi (TORINO). PRS/Higgs meeting 06/08/05. A preliminary study of the Vector Boson Fusion Process with FAMOS. Sara Bolognesi (TORINO). PRS/Higgs meeting 06/08/05. Signal and background definition. Vector Boson Fusion in PHASE. W mn.

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A preliminary study of the Vector Boson Fusion Process with FAMOS

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  1. Sara Bolognesi (TORINO) PRS/Higgs meeting 06/08/05 A preliminary study of the Vector Boson Fusion Process with FAMOS

  2. Sara Bolognesi (TORINO) PRS/Higgs meeting 06/08/05 Signal and background definition

  3. Vector Boson Fusion in PHASE W mn pp qq qqVW qqVW qqqqmn where The signal is V= Z\W qq • PREVIOUS EXISTING MC MadEvent PYTHIA pp qq qqVLWL qqVLWL qqqqmn pp qq qqVW qqqqmn production and decay approximation (i.e. only diagrams with on shell bosons outgoing) • only boson fusion diagrams • EVBA approximation • only longitudinal bosons • NEW MC DEVELOPED BY TURIN GROUP (Accomando, Ballestrero, Maina) PHASE exact calculation of all the processes pp->qqqqmn O(aEW6) xsec = | fusion diagrams + irreducible background |2 huge interference effects Reference for PHASE hep-ph/0404236 C.Mariotti talk (12/08/04) at PRS session of CMS Week E. Maina talk (05/14/05) at LesHouches Workshop

  4. t b b W W V q q’ [ 80 < M(qq) < 100 (GeV) || 70 < M(qq’) < 90 (GeV) ] [ 80 < M(qq) < 100 (GeV) || 70 < M(qq’) < 90 (GeV) ] Signal definition: cut Because of the presence of the irreducible background, we need a definition for signal “a posteriori” (i.e. after events generation) • Cut against the top contribution* 160 < M(bqq’,bmn) < 190 (GeV) • Ask for two bosons in the final state* [ 70 < M(mn) < 90 (GeV) ] && • Cut against three bosons in the final state* for the other 2 quarks * the right quarks flavours are always requested

  5. Signal definition: xsec M(H) (GeV) 300 500 700 no Higgs total 0.794 pb 0.718 pb 0.699 pb 0.689 pb signal 0.247 pb 0.184 pb 0.169 pb 0.158 pb top (EW) 0.495 pb 0.494 pb 0.493 pb 0.495 pb other irr. backg. 0.052 pb 0.040 pb 0.037 pb 0.036 pb TOP (EW) • big contribution (at low invariant mass VV) OTHER IRREDUCIBLE BACKGROUND: - NON RESONANT - THREE BOSONS OUTGOING • little contribution (~ constant over all the spectrum) • Higgs mass dependence (because of the Higgsstrahlung diagrams) 2 central q + mn ~ 2 outgoing bosons

  6. No Higgs sample q tag n p m W V q p q q V V q’ q tag Signal kinematics 2 central bosons with high pT high MET central muon with high pT 2 q from boson decay: central, little Dh, high pT 2 q tag: high h and big Dh, very high energy

  7. Backgrounds • Irreducible background (i.e. background with the same final state of the signal and at the same perturbative order aEW6) • single and double top (pure EW), (xsec in a previous slide: ~ 0.5 pb) • non resonant diagrams, • events with three bosons outgoing 2. Background with the same final state of the signal but at a different perturbative order • pp t t 1m+XaS2aEW4 622 pb PYTHIA pp qqZW qqqqmn still missing (but xsec ~ 3 fb) • pp qqWW qqqqmnaS2 aEW4 9.1 pb MadEvent • pp qqqqW qqqqmnaS4aEW2 359 pb AlpGen q = u,d,c,s,g 3. Background with lower multiplicity of quarks in the final state (e.g.: Wqq, Wqqq, single W) not considered to avoid multiple counting due to initial/final state gluon radiation during the parton shower evolution q g q g Wqq Wqqqq q g q We are waiting for the new AlpGen version: it will generate W + n jets without multiple counting W

  8. Reco with FAMOS_1_2_0 NO PILE-UP !! • GlobalMuons • We try to reconstruct jets with different algorithms ConeCut =0.5 Iterative Cone Algo ConeSeedEtCut = 0.5 JetCalibration = GammaJet JetRecom = 1 MidPointConeRadius= 1 MidPoint Cone Algo JetInput = EcalPlusHcalTower MidPointConeSeedThreshold = 0.5 EcalPlusHcalTowerEt = 0.5 KtJet RParameter Algo RParameter = 1 DCut = 400 KtJet DCut Algo KtJetAngle = 2 KtJet NJet Algo NJet = 4 • We try to reconstruct MET with different algorithms FamosMETfromCaloTower Tower Correction = true TowerEtCut = 0.5 JetCorrection = true FamosMETfromJet JetUnclusterTower = true JetUnclusterCorrection = true Primary Vertex Finder • Combined Btagging Algo Iterative Cone Algo for jets (with the previous parameters)

  9. Sara Bolognesi (TORINO) PRS/Higgs meeting 06/08/05 “MC” resolution reconstructed value – generated value • resolution (%) = generated value • absolute resolution = reconstructed value – generated value (No Higgs sample used as reference in the following)

  10. Resolution: m and n We choose the closest muon to the generated one (only if DR<0.2) • resolution < 10% in 86% of the events • transverse momentum underestimated FWHM ~ 1.6 GeV absolute resolution: peak at ~ -0.3 GeV resolution peaked at -1.3 % Total generated MET ~ pT of signal n • METfromJets more precise • resolution < 10% in 19 % of the events • MET underestimated FWHM ~ 43 GeV absolute resolution: peak at ~ -3 GeV resolution peaked at -15 % In order to reconstruct pzn we ask for (pm + pn)2 = mW2

  11. Resolution: leptonic W muonpTand neutrino pT underestimated (previous slide) W pT underestimated • resolution peaked at -12.5 % • absolute resolution (gaussian fit): std. deviation ~ 24 GeV mean ~ -7 GeV W pseudorapidity overestimated (absval) resolution with asymmetric shape

  12. Resolution: jets hadronic W/Z JETS RESOLUTION Resolution calculated for selected events with only 4 jets: each of them has been matched with the closest generated quark (DR < 1) Calibration only for ICA !!! HADRONIC BOSON MASS RESOLUTION • mV resolution peaked at +10% (ICA) • mV absolute resolution (gaussian fit): std. deviation ~ 18 GeV mean at ~ 10 GeV

  13. Sara Bolognesi (TORINO) PRS/Higgs meeting 06/08/05 Data analysis Work in progress Considered Higgs masses: 300 GeV, 500 GeV, 700 GeV, no Higgs case

  14. Cuts (1) Signal reconstruction signal (NoHiggs) background (considered only jets with pT > 30 GeV) muon with maximum pT ( > 20 GeV) pTn = MET ( > 20 GeV) • leptonic W 74 % 50 % pzn (pm+pn)2 =mW2 (no cut on mW!) |hj1|, |hj2| <3 • hadronic V 50 < M(j1,j2) <125 (GeV) 52 % 36 % |hj1-hj2| < 2 (if more then one, the most central has been chosen) 44 % 25 % • ask for other 2 tag jets = 2 most energetic remaining jets

  15. Cuts (2) Background rejection signal (NoHiggs) background (considered only jets with pT > 30 GeV) • cut against top 100 < M(W,q), M(V,q) < 300 (GeV) 14 % 38 % for any jet with |h| > 3 (out of B-tag algo acceptance) 100 < M(W,b), M(V,b) < 300 (GeV) b = jet with maximum probability of b-tagging (only if P(b)>1) pTjtag1,pTjtag2 > 50 GeV 14 % 1.1 % • cuts on tag jets M(jtag1,jtag2) > 600 GeV |hjtag1-hjtag2| > 1.5 hjtag1*hjtag2 < -1 |hW| < 2 12 % 0.8 % • some other cuts M(V,W,jtag1, jtag2) > 1 TeV (Njet with |hj|<2) < 12 considered also jets with pT < 30 GeV

  16. Analysis resolution • resolution on the signal after the previous analysis cuts Comparison between • resolution on the signal using the MC truth (histos normalized to 1) With the previous cuts we keep a resolution roughly equal to the “MC” resolution… … but …

  17. Efficiency and significance … the bad reconstruction resolution affects our efficiency on the signal remember: we loose 50% of the signal only by asking pTm, pTn > 20 GeV and the presence of an hadronic boson !!! We would like to be more efficient at high M(VW) (too many fluctuation: we need more statistic) 100 fb-1 100 fb-1 No Higgs - 100 fb-1 different backgrounds already summed The biggest background at high M(VW) after our analysis cuts is Wjjjj

  18. Events Number of events and significance at the Higgs peak ± 30 % ( = our analysis resolution) 100 fb-1 M(H) ± 30% (GeV) 500 ± 150 NoH (> 1 TeV) 300 ± 90 700 ± 210 signal events 1893 1023 473 26 background events 437297 243833 124172 10932 significance 2.1 1.3 0.2 2.9 500 fb-1 M(H) ± 30% (GeV) 500 ± 150 NoH (> 1 TeV) 300 ± 90 700 ± 210 signal events 9463 5113 2364 128 54662 background events 2.186×106 1.219×106 620858 significance 4.6 3.0 0.5 6.4 With this resolution some years are necessary to discover a heavy Higgs boson

  19. Problems Generate W + n jets without double counting with the future AlpGen version Bad resolution (also when we use the MC truth) first of all for the jets Not a FAMOS problem (I think) something similar for top and W mass in ORCA / R.Chierici talk (03/14/05) at PRS Session of CMS Week Is it a problem related with our reconstruction program (e.g. ConeSeedEtCut too low)? we have to check, more deeply, different values for the parameter our hint ! Is it a software problem? (i.e. we have to wait for a more realistic resolution because the software is still in development?) Or maybe is it a detector problem? Is this the best that we can do with our detector? We are investigating on… Plans: to apply the same analysis cuts to the MC truth to “quantify” the resolution problem on the signal efficiency

  20. Good news • We have for the first time a MC (PHASE) able to generate the signal in an exact way (without any approximation) and the irreducible background For a comparison of the different MC see R.Bellan talk (03/15/05) at PRS Session of CMS Week • The background and signal samples we are producing in Turin, are being submitted to the official production The production status is reported at http://www.to.infn.it/~bellan/works/status_produzione.html • An analysis with FAMOS is not only possible but also reliable and VERY fast • In 1 day we have processed 500.000 events of signal (via LSF) • An ENOURMOUS help from developers always available at cms-sw-fastsimul@cern.ch Next-to-next step = to perform the same analysis in ORCA to compare the results

  21. Backup slides • Generated statistic • MV, M(VW) distributions • pzn reconstruction • Detailed efficiency of the cuts • Events and significance integrated over all the spectrum

  22. xsec and generated events signal and irreducible background M(H) = 300 GeV 0.794 pb 500.000 M(H) = 500 GeV 0.718 pb 500.000 M(H)= 700 GeV 0.699 pb 500.000 no Higgs 0.689 pb 500.000 other backgrounds pp t t 1m+X 622 pb 200.000 pp qqWW qqqqmn 9.1 pb 253736 pp qqqqW qqqqmn 359 pb 180006 pp qqW+W- qqqqmn 9.04 pb 249231 pp qqW+W+ qqqqmn 0.05 pb 1996 pp qqW-W- qqqqmn 0.02 pb 2509

  23. M(V), M(VW) distributions impossible to distinguish W and Z peaks 100 fb-1 100 fb-1 background histrograms superimposed (not stacked)

  24. Neutrino reconstruction • pTn = MET (METFromJets algorithm) second degree equation with two solutions • pzn calculated with (pm + pn)2 = mW2 we chose the biggest solution and we take the real part if the discriminant is negative ( 30 % of the events )

  25. Detailed efficiency of the cuts cuts on tag jets some other cuts 2 tag jets cut top leptonic W hadronic V signal 75 % 56 % 46 % 39 % 13 % 12 % 300 GeV irred. backg. 72 % 57 % 37 % 17 % 1 % 0.8 % signal 75 % 55 % 46 % 40 % 14 % 12 % 500 GeV irred. backg. 71 % 57 % 38 % 17 % 1 % 0.8 % signal 74 % 53 % 45 % 39 % 14 % 12 % 700 GeV irred. backg. 72 % 57 % 38 % 17 % 1 % 0.7 % signal 73 % 52 % 44 % 38 % 14 % 12 % no Higgs irred. backg. 72 % 57 % 38 % 17 % 1 % 0.8 % pp t t 1m+X 43 % 34 % 24 % 9 % 0.4 % 0.3 % pp qqWW qqqqmn 56 % 34 % 15 % 13 % 0.6 % 0.4 % pp qqqqW qqqqmn62 % 40 % 26 % 23 % 2.2 % 1.6 % For a description of the cuts see slides “Cuts(1)” and “Cuts(2)”

  26. Events Events and significance integrated over all the M(VW) spectrum 100 fb-1 M(H) = 300 GeV M(H) = 500 GeV M(H)=700 GeV No Higgs signal events 2860 2303 2064 1898 background events 771689 771633 771596 771594 significance 2.6 2.3 2.2 3.2 irreducible background depends on the Higgs mass 500 fb-1 M(H) = 300 GeV M(H) = 500 GeV M(H)=700 GeV No Higgs signal events 14289 11510 10320 9493 background events ~ 3.858 × 106 significance 5.9 5.2 4.8 7.3 With this resolution some years are necessary to discover a heavy Higgs boson

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