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Higgs self-coupling at photon collider (AA->HH Study)

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Higgs self-coupling at photon collider (AA->HH Study). Shin- ichi Kawada AdSM , Hiroshima University. Outline. almost same contents @ LCWS11. Motivation Signal & Background Simulation & Analysis Result Summary & Next plan. Motivation. - PowerPoint PPT Presentation

Feasibility study of measurement of Higgs pair creation in a gamma-gamma collider

Higgs self-coupling at photon collider(AA->HH Study)Shin-ichi KawadaAdSM, Hiroshima University23rd General Meeting @ KEK (2011/11/5)1OutlineMotivationSignal & BackgroundSimulation & AnalysisResultSummary & Next plan23rd General Meeting @ KEK (2011/11/5)2almost same contents @ LCWS11Motivation23rd General Meeting @ KEK (2011/11/5)3Final goal : measuring Higgs self-coupling constant Before the final goalWe have to investigate the feasibility ofmeasurement of Higgs pair creation in a PLC.Higgs self-coupling constantin the SMdeviation parameterfrom the SMOptimizing collision energy4

Ldt = 1000fb-1 = = 1, BG = 0270GeVmH = 120GeVBeam parameters5x3.76x4.8Ee(GeV)210195n(1010)22z(mm)0.350.35x/y(mrad)2.5/0.032.5/0.03x/y(mm) @ IP1.5/0.31.5/0.3x/y(nm)96/4.799/5.5L(nm)1054770x = 4Ee/me23.764.8Pulse Energy(J)1010Lgeo(e-e-)[1034cm-2s-1]8.78.1Lpeak()[1034cm-2s-1]1.20.7Ltot() [1034cm-2s-1]12.65.88x=3.76in this studybased on TESLA optimistic parameter

Luminosity distribution6simulated with CAIN6Signal & Backgrounds7

270GeV->WW->ZZtt threshold# of events23rd General Meeting @ KEK (2011/11/5)8Signal->HH : 16 events/year

Main backgrounds->WW : 1.462*107 events/year->ZZ : 1.187*104 events/year->4b : 1.37*105 events/yearEvent signature (1)->HHHH->4bMbb = MH (120GeV)23rd General Meeting @ KEK (2011/11/5)9

Mbb (GeV)b-jet b-jetmass distributionEvent signature (2)->WW->WW ~ 106->HHsuppressed by b-tagging->ZZZZ->4b same as HH->4bdiscriminate only by mass difference->4bMass distribution is different from signal, but still have events near signal region (~120GeV).Angular distribution is different from signal.23rd General Meeting @ KEK (2011/11/5)10Simulation & AnalysisEvent generation & Detector simulationEvent reconstructionjet clusteringb-taggingnsig methodjet pairingEvent selectionpre-selectionNeural Network (NN)23rd General Meeting @ KEK (2011/11/5)11Event reconstruction (1)23rd General Meeting @ KEK (2011/11/5)12information of massM1, M2 : reconstructed massi : H, W, Z, bb2j : mass resolution

ex:H2 distributionH2Event reconstruction (2) : b-tagging23rd General Meeting @ KEK (2011/11/5)13

When there are noffv tracks which satisfy this equation,we regarded this quark as a b-quark.can be improved by further studyrelatively simple b-tagging methodnsig methodEvent selection by Neural Network (NN)3 stepsW filter4b filterZ filterMaximize statistical significance23rd General Meeting @ KEK (2011/11/5)14N : # of eventsDistribution of NN inputs : WW23rd General Meeting @ KEK (2011/11/5)15

H2# of b-flavor jet with(nsig = 3.5, noffv = 2)analysisHHHHWWWW

Distribution of NN inputs : 4b23rd General Meeting @ KEK (2011/11/5)16# of tracks

HH4bHH4bmaximum |cos of jet|Distribution of NN inputs : ZZ23rd General Meeting @ KEK (2011/11/5)17


HHZZHHZZZ2Cut summary (training sample) = (test sample)18HHWWZZ4bexpected events(# of MC samples)80(50000)73100000(75000000)59350(1000000)293600(1000000)pre-selection47.93(29958)81655(83777)5167(87057)84491(287776)W filter12.34(7713)8.772(9)193.4(3259)568.4(1936)4b filter8.238(5149)0(0)84.40(1422)13.21(45)Z filter4.994(3121)0(0)7.359(124)5.872(20)Cut summary (training sample) (test sample)19HHWWZZ4bexpected events(# of MC samples)80(50000)73100000(75000000)59350(1000000)293600(1000000)pre-selection47.72(29823)81313(83426)5172(87142)84538(287935)W filter12.30(7685)21.44(22)191.6(3228)591.9(2016)4b filter6.038(3774)5.848(6)62.61(1055)26.72(91)Z filter3.546(2216)3.899(4)4.926(83)12.62(43)Further improvementWW BG : almost completely suppressed!4b & ZZ BG remainedPossible improvement --- jet clustering23rd General Meeting @ KEK (2011/11/5)20We investigated using generator information forHH, WW, ZZ (not for 4b).improve mass resolution, b-tagging efficiencycorrect color singlet informationImprove mass resolution23rd General Meeting @ KEK (2011/11/5)21

perfect jet clusteringJADE clusteringHHHHZZZZEx:mass distribution ofHH & ZZ BGCut summary with perfect jet clustering(training sample) = (test sample)22HHWWZZ4bexpected events(# of MC samples)80(50000)73100000(75000000)59350(1000000)293600(1000000)pre-selection46.64(29152)55836(57287)4172(70292)84491(287776)W filter38.58(24115)4.873(5)98.84(1667)2179(7422)4b filter34.50(21562)2.924(3)27.66(466)2.642(9)Z filter33.06(20662)2.924(3)5.935(100)2.642(9)Cut summary with perfect jet clustering(training sample) (test sample)23HHWWZZ4bexpected events(# of MC samples)80(50000)73100000(75000000)59350(1000000)293600(1000000)pre-selection46.64(29152)55613(57058)4191(70615)84538(287935)W filter34.54(21587)1.949(2)56.68(955)1639(5583)4b filter31.36(19600)0.9747(1)20.36(343)4.110(14)Z filter29.94(18710)0.9747(1)4.807(81)4.110(14)SummaryWe investigated ->HH in a gamma-gamma collider based on TESLA optimistic parameters.Possible to suppress huge backgrounds with improved jet clustering.Significance ~ 5 with 5 year PLC runNext planWriting a paper -> now updating Ver.0 -> Ver.123rd General Meeting @ KEK (2011/11/5)24Backup slides23rd General Meeting @ KEK (2011/11/5)25About PLC23rd General Meeting @ KEK (2011/11/5)26

ElectronsbackwardComptonscatteringgamma-gamma collisionComparison of and e+e- process23rd General Meeting @ KEK (2011/11/5)27

: Higgs self-couplingContribution of self-coupling is different way.Energy threshold of process is lower than e+e- process.->bbbb (4b) events23rd General Meeting @ KEK (2011/11/5)28bbbbbb: color stringbb(2-jet invariant mass) < 15GeV were cut.We assume that we can cut these events.--> 5.872*104 events/yearCalculation of 4b BG29ELWK = 2QCD = 2Calculated withGRACE

d -> bJet clustering23rd General Meeting @ KEK (2011/11/5)30JADE clusteringpi : 4-momentum of particle iEvis : visible energyYcut : Ycut value of jet clusteringEvent selection --- pre-selection23rd General Meeting @ KEK (2011/11/5)31>0.05, |cos|

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