Multivariate analysis of H b b in associated production of H with t t-pair using full simulation of ATLAS detector

Transcription

1 Mulivariae analysis of H b b in associaed producion of H wih -pair using full simulaion of ATLAS deecor Sergey Koov MPI für Physik, München ATLAS-D Top meeing, May 19, 26 Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 1 / 24

2 1 Channel overview 2 General reconsrucion sraegy Building and raining of he neural nework 4 Analysis resuls 5 Conclusions and plans Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 2 / 24

3 Low mass SM Higgs boson overview LEP2 experimenal bounds on Higgs mass precision measuremens of EW observables: m H = GeV direc searches: m H > 114 GeV Signaure channels for low mass SM Higgs H τ + τ in vecor boson fusion H γγ in gluon fusion H W W lνlν in vecor boson fusion H ZZ 4l in gluon fusion H b b in H associaed producion wih Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 / 24

4 Channel descripion Feaures of H, H b b channel Complex final sae 6 jes: 4 b-jes and 2 ligh jes 1 high-p lepon (rigger) missing energy from neurino addiional jes from ISR/FSR Large backgrounds combinaorial from mis-pairing of jes irreducible from b b evens reducible from + jes evens Full reconsrucion of even is required, good je reconsrucion and good b-agging are needed Expeced number of evens a LHC H, H b b signal b b background jj background Process σ LO, LHC evens for L of MC FasSim FullSim BR pb fb 1 1 fb 1 generaor sample sample H (blν)(bjj)(b b) k 1.5k Pyhia 1M 42k b b (blν)(bjj)b b (QCD) 8.1 a k 25k AcerMC 1.8M 72k b b (blν)(bjj)b b (EW) k 26k AcerMC 2k (blν)(bjj) + jj M 12M Alpgen 1M K a Srongly depends upon facorizaion scale (up o a facor of 2). Here, µ = (m + m H )/2 Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 4 / 24

5 Even reconsrucion: preselecion Preselecion cus 1 isolaed lepons b b H b + W + l ν AOD conainers MuonCollecion, ElecronCollecion p >2 GeV and η <2.7 E < 1 GeV wihin he isolaion cone of R =.4 e-id: EM cluser has a mached rack in ID and he cluser shape is consisen wih e-hypohesis µ-id: he combined fi of muon rack has has good qualiy 4 b-jes b - W q q AOD conainer BJeCollecion p >15 GeV and η < sandard ATLAS b-agging cu: jew eigh > 2 ligh jes AOD conainer BJeCollecion p >15 GeV and η < b-agging cu (ani-b-ag): jew eigh <.1 several je reconsrucion algorihms are available (Cone4, Cone7, K) Cone4 and Cone7 algorihms will be compared hroughou his alk Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 5 / 24

6 Even reconsrucion: making combinaions Making 4 b-je + 2 ligh jes + 1 lepon combinaions and selecing he bes one use evens which pass preselecion crieria (1 isolaed lepon, 4 b-jes, 2 ligh jes) deermine p ν from p l and p miss using m W consrain (if fails, use approximaion p z ν = pz l ) reconsruc leponic W lν from lepon and neurinos reconsruc hadronic W jj from jj combinaions wih m jj m W < 5 GeV (he jes 4-momena rescaled o ge he nominal W mass) permue over all combinaions of reconsruced W lep, W had, and 4 b-jes calculae he evaluaion parameer for each combinaion from each even selec he combinaion wih he highes value of his parameer plo invarian mass disribuions from hese bes combinaions and look for a Higgs peak Various evaluaion parameers of -pair reconsrucion ATLAS TDR: m = (m blν m ) 2 + (m bjj m ) 2 -pair likelihood in ATL-PHYS-2-24 analysis his analysis uses neural nework evaluaion parameer Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 6 / 24

7 Reconsrucion efficiency and resoluion: elecrons Reconsruced p for elecrons Enries 1998 Efficiency vs p for elecrons Enries e e+5 12 Efficiency.685e e+4.9 Fake rae Mached Fakes Efficiency = 61.9% p resoluion for elecrons Enries 1998 p /p vs p for elecrons Enries e y χ / Consan e+4.4 y.516 Sigma p mean value 64 GeV average efficiency 62% mean p shif.4% p resoluion 2.5% /p p p /p Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 7 / 24

8 Reconsrucion efficiency and resoluion: muons Reconsruced p for muons Enries Efficiency vs p for muons Enries e e+5 Efficiency.62e e Fake rae Mached Fakes Efficiency = 65.7% p resoluion for muons Enries p /p vs p for muons Enries e χ 2.2 y /.62e+4 Consan y Sigma.2552 /p p p mean value 6 GeV average efficiency 66% mean p shif.5% p resoluion 2.5% p /p Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 8 / 24

9 Reconsrucion efficiency and resoluion: b-jes, JeCone=.7 Reconsruced p for b-jes Enries Efficiency vs p for b-jes Enries e e Mached Fakes 5.946e Efficiency Efficiency Fake rae = 42.9% 7.558e p resoluion for b-jes Enries p /p vs p for b-jes Enries e χ 912 / y Consan 1.665e e y 14 Sigma p mean value 16 GeV average efficiency 4% mean p shif.4% p resoluion 17% p /p /p p Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 9 / 24

10 Reconsrucion efficiency and resoluion: b-jes, JeCone=.4 Reconsruced p for b-jes Enries Efficiency vs p for b-jes Enries e e Mached Fakes 5.449e Efficiency Efficiency Fake rae = 52.% 8.251e p resoluion for b-jes Enries p /p vs p for b-jes Enries e y χ 1457 / e+4 Consan 2.421e y Sigma p mean value 89 GeV average efficiency 52% mean p shif 1% p resoluion 15% p /p /p p Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 1 / 24

11 Reconsrucion efficiency and resoluion: ligh jes, JeCone=.7 Reconsruced p for ligh jes Enries 4172 Efficiency vs p for ligh jes Enries e e e e Efficiency = 52.2% p resoluion for ligh jes Enries 4172 p /p vs p for ligh jes Enries e y χ 27.1 / 2 4 Consan 1.122e e y 1.59 Sigma.1481 p mean value 8 GeV average efficiency 52% mean p shif 4% p resoluion 15% p /p /p p Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, / 24

12 Reconsrucion efficiency and resoluion: ligh jes, JeCone=.4 Reconsruced p for ligh jes Enries 522 Efficiency vs p for ligh jes Enries e e e e Efficiency = 69.8% p resoluion for ligh jes Enries 522 p /p vs p for ligh jes Enries e y χ / 2 18 Consan 1.75e e y.86 Sigma /p p -1 p mean value 68 GeV average efficiency 7% mean p shif 8% p resoluion 14% p /p Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, / 24

13 Reconsrucion efficiencies Preselecion efficiencies for JeCone=.4 (JeCone=.7) H b b Paricle Kinemaical Reconsrucion Kinemaical Reconsrucion accepance, % efficiency, % accepance, % efficiency, % e 88.1 (88.4) 61.9 (61.8) 88. (88.4) 65.9 (66.2) µ 88.1 (88.) 65.7 (65.8) 88. (88.) 69.1 (69.1) b-je 9.4 (9.4) 52. (42.9) 75.7 (75.7) 47.5 (41.1) ligh je 48.7 (48.6) 69.8 (52.2) 59.6 (59.6) 76. (61.9) 15 GeV p cu on ligh jes required by ani-b-agging algorihm considerably decreases kinemaical accepance sandard ATLAS b-agging algorihm has 6% efficiency on average using Cone4 over Cone7 algorihm increases average je mulipliciy from 5.7 o 7.1 which means an overall improvemen facor of in je reconsrucion efficiencies on he oher hand, jes reconsruced wih Cone4 algorihm have heir p underesimaed by 1% which means negaive shifs in invarian mass disribuions Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 1 / 24

14 The neural nework srucure and performance Due o limied size of he full simulaion sample, fas simulaion sample was used o rain he ANN ANN variables TDR s evaluaor, m = (m blν m ) 2 + (m bjj m ) 2 invarian mass of wo ligh jes from W had invarian mass of -H sysem R beween wo ligh jes from W had R beween b-je and W had from he same -quark R beween b-je and W lep from he same -quark R beween sysem and Higgs Fas simulaion no-mached and H Full simulaion mached, no-mached H.9. no-mached, mached H.8 mached and H.25.7 HDelaRdNN HMassNN Dela2MassNN bwhdelardnn jjdelardnn jjmassnn bwldelardnn HTruhKineTag no-mached and H mached, no-mached H no-mached, mached H mached and H ANN oupu value ANN oupu value Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, / 24

15 ANN variables: Full simulaion vs Fas simulaion signal samples Dela2Mass.5 jjmass.45 Fas, mached Fas, no-mached jjdelard Full, mached Full, no-mached m, MeV m jj, MeV R jj bwhdelard bwldelard HMass.4.4 Fas, mached Fas, no-mached Full, mached Full, no-mached R bw R bw m, MeV H mos powerful discriminaing variables are m and R jj in full simulaion m variable has less power han in fas simulaion Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, / 24

16 Reconsruced -pair invarian mass disribuions: JeCone=.4 H signal, JeCone=.4 H signal, JeCone=.4 Enries 124 Enries e e+5 Evens 1.6e+4 18 χ / 7 16 Consan 18.1 ± 7.2 all e+5 ± 472 mached Sigma 1.5e+4 ± Evens 1.65e+4 18 χ / 7 16 Consan ± 6.9 all e+5 ± 51 mached Sigma 1.475e+4 ± m bjj, MeV m blν, MeV bb background, JeCone=.4 bb background, JeCone=.4 Enries 71 Enries e e+5 Evens e+4 χ / 7 12 Consan ± e+5 ± Sigma 1.42e+4 ± 71 Evens e+4 2 χ 2.6 / 7 12 Consan 85 ± e+5 ± 94 1 Sigma 1.721e+4 ± m bjj, MeV m blν, MeV shif in he reconsruced m 5 GeV reconsruced m widh 14 GeV Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, / 24

17 Reconsruced -pair invarian mass disribuions: JeCone=.7 H signal, JeCone=.7 H signal, JeCone=.7 Enries 64 Enries e e+5 Evens 1.84e χ 1.58 / 7 Consan ±.58 6 all 1.71e+5 ± 118 mached 5 Sigma 1.55e+4 ± 115 Evens 1.555e+4 7 χ / 7 Consan 54.7 ±.99 6 all 1.719e+5 ± 849 mached 5 Sigma 1.25e+4 ± m bjj, MeV m blν, MeV bb background, JeCone=.7 bb background, JeCone=.7 Enries 18 Enries e e Evens 1.684e χ / 7 Consan ± e+5 ± 298 Sigma e+4 ± 241 Evens 1.861e χ / 7 Consan 14.6 ± e+5 ± 18 Sigma e+4 ± m bjj, MeV m blν, MeV shif in he reconsruced m GeV reconsruced m widh 15 GeV Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, / 24

18 Reconsruced Higgs invarian mass disribuions: JeCone=.4 Enries 124 H signal, JeCone= e+5 Evens all 5.167e+4 χ / 2 mached p ±.61 p1.42e-11 ± 9.18e-4 p2 9.17e-8 ± 1.16e-8 p e-5 ± 7.e-7 p ± p e+4 ± 296 p6 1.86e+4 ± N=277/ m bb, MeV Enries 71 bb background, JeCone= e+5 Evens e+4 χ / 26 8 p ± p1.288 ±.27 p e-1 ± 1.94e-8 6 p 1.746e-5 ± 5.276e m bb, MeV Efficiencies H sample b b sample ɛ, % Evens ɛ, % Evens W lep W had b-jes fi area he shape of disribuions reasonably well described by funcion (a + a 1 x + a 2 x 2 )e bx + Gaussian he reconsruced Higgs mass is shifed from he nominal by 22 GeV Higgs mass widh is 18 GeV Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, / 24

19 Reconsruced Higgs invarian mass disribuions: JeCone=.7 Evens H signal, JeCone=.7 6 all mached 5 4 Enries e e+4 χ / 22 p ± p e-14 ± 1.862e-4 p2 1.52e-8 ± 2.46e-9 p 2.72e-5 ± 1.162e-6 p ±.2 p5 1.25e+5 ± 4219 p6 2e+4 ± 5 bb background, JeCone= Evens Enries e e+4 χ / 25 p.74 ± p1 2.84e-17 ± 8.56e-5 p e-9 ± 5.678e-1 p 1.471e-5 ± 1.698e N=92/ m bb, MeV m bb, MeV Efficiencies H sample b b sample ɛ, % Evens ɛ, % Evens W lep W had b-jes fi area (a + a 1 x + a 2 x 2 )e bx + Gaussian funcion sill describes disribuions quie well he reconsruced Higgs mass is close o he nominal Higgs mass widh is 2 GeV Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, / 24

20 Expeced signal afer fb 1 of luminosiy Real daa, JeCone=.4 evens/15 GeV L= fb, M =12 GeV H H+bb H H mached Enries e+5 χ / 1 p ± 2.8 p1.415 ±.166 p2 p 9.571e-9 ± 1.89e-5 ± 4.69e-8 6.8e-6 p4 1.4 ± 1.8 p5 9e+4 ± 249 p6 2.5e+4 ± 929 Real daa, JeCone=.7 evens/15 GeV L= fb, M =12 GeV H H+bb H H mached Enries e+5 χ / 12 p ± p1 p2 p 2.482e-12 ± 5.751e-9 ± 1.499e-5 ± 6.252e e e-6 p4 5 ± 5.1 p5 1.25e+5 ± 4671 p6 1.5e+4 ± M, MeV bb M, MeV bb i s hard o exrac he signal, unless he background shape is well known from MC, so ha one can consrain background conribuion o he fi Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 2 / 24

21 Conclusions and plans final even reconsrucion efficiency srongly depends upon je reconsrucion algorihm (a facor of beween JeCone4 and JeCone7) sandard ATLAS b-agging algorihm performance is saisfacory i would be difficul o exrac he H b b signal from daa wihou good undersanding of he background shape hings o do deermine he shape of reducable jj background (sill no enough full simulaion samples) rerun he analysis wih K and TopoCluser je reconsrucion wih more saisics, rerain he neural nework on full simulaion daa Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, / 24

22 Efficiencies and resoluions: JeCone=.4 vs JeCone=.7 Reconsruced p for b-jes H, JeCone=.7 bb, JeCone=.7 H, JeCone=.4 bb, JeCone= Reconsruced p for ligh jes H, JeCone=.7 bb, JeCone=.7 H, JeCone=.4 bb, JeCone= Efficiency Efficiency Efficiency vs p for b-jes H, JeCone=.7 bb, JeCone=.7 H, JeCone=.4 bb, JeCone= Efficiency vs p for ligh jes H, JeCone=.7 bb, JeCone=.7 H, JeCone=.4 bb, JeCone= p /p vs p for b-jes /p p /p p H, JeCone=.7 bb, JeCone=.7 H, JeCone=.4 bb, JeCone= p /p vs p for ligh jes H, JeCone=.7 bb, JeCone=.7 H, JeCone=.4 bb, JeCone= Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, / 24

23 Disribuions of he ANN variables in signal sample: Fas simulaion bwlmass.5.4 mached no-mached mc ruh bwldelard.4.5. mached no-mached mc ruh jjmass.5.4 mached no-mached mc ruh jjdelard.4.5. mached no-mached mc ruh bwhmass.8 mached no-mached bwhdelard.4 mached no-mached Dela2Mass.5 mached no-mached Mass mached no-mached.7 mc ruh.5 mc ruh mc ruh.7 mc ruh DelaRd SumP HMass HDelaRd.1 mached no-mached.8 mached no-mached mached no-mached mached no-mached mc ruh.7 mc ruh.6 mc ruh.12 mc ruh Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, 26 2 / 24

24 Neural nework basics Mulilayer Percerpron Combinaion inpu variables Inpu layer TMuliLayerPercepron ROOT buil-in class is used as neural nework (1 hidden layer wih 1 nodes) 115 of mached and 125 of non-mached combinaions were used o rain he neural nework Hidden layer h j = f(σ x i w ij +θ j ) f = 1 -x 1+e Oupu layer O = Σ h j w j +θ o Probabiliy of being a signal combinaion E = 1 N (O-T) 2 Sergey Koov (MPI für Physik, München) Mulivariae analysis of H b b in H producion ATLAS-D Top meeing, May 19, / 24