Double J/psi production at DØ experiment

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1 Double J/psi production at DØ experiment 1/24 Double J/psi production at DØ experiment INTERNATIONAL SCHOOL OF SUBNUCLEAR PHYSICS 51st Course: REFLECTIONS ON THE NEXT STEP FOR LHC Erice, 24 June 3 July 213 O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Taras Shevchenko National University of Kyiv, DØ Experiment, Fermilab O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

2 Double J/psi production at DØ experiment 2/24 1 Motivation 2 Tevatron & DØ detector 3 MC and DATA selection 4 Combinatorial background 5 Prompt fraction 6 Systematics 7 Total cross section 8 Summary 9 Backup O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

3 Double J/psi production at DØ experiment 3/24 Motivation Motivation Measurement of double J/ψ production cross section in the single and double parton scattering event: extraction of σ eff at low energy scale; Test of σ eff energy dependence Prediction for the Tevatron: pt (J/ψ) > 4GeV, η(j/ψ) < 6,J/ψ 2µ Predicted DP fraction is -15% σ DP (ψψ) = σ SP(ψ) 2 2σ eff LHCb J/psi cross section measurement: 56± 11 nb Theoretical predictions: SP: 4nb DP: 2nb O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

4 Double J/psi production at DØ experiment 4/24 Motivation Motivation Two mechanisms of SP production: color singlet(a) color octet(b) The differential cross-section of J/ψ pair production versus p T at the Tevatron a - color-octet and b - color-singlet O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

5 Double J/psi production at DØ experiment 5/24 Tevatron & DØ detector Tevatron & DØ detector Luminosity of 86fb 1 p p collisions s = 196TeV Tracker and Magnet Calorimeter Muon System O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

6 Double J/psi production at DØ experiment 6/24 MC and DATA selection MC and DATA selection DjpsiFDC generator interfaced to Pythia was used for signal MC It has two models implemented: CS and CO Background MC actually is non-prompt J/ψ from b-bbar generated with Pythia Data:run2b data HAS 2MU 1 5 subskim of Muinclusive skim:2 loose muons with pt central > 15GeV Offline cuts: pt µ > 2GeV if η µ < 135 OR pt µ > 4GeV if η µ 135 (note #681); η µ < 2; #SMT &#CFThits 2; nseg = 1 or 3; each muon in pair should be at least Loose ; opposite charges of muons in pair; r DCA < 5cm,z DCA < 2cm; different ID for all muons in both J/ψ s muon pair should be at mass window GeV J/ψ: pt > 4GeV η < 2 O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

7 Double J/psi production at DØ experiment 7/24 Combinatorial background Combinatorial background For calculation combinatoric background, we fit 2D mass distribution (excluding peak region) by plane Data was rebinned and normalized on bin size ψψ, GeV/c 2 M 1 2 χ / ndf 6197 / 86 Slope X ± 114 Slope Y ± 1288 Pedestal 43 ± ψψ M 2, GeV/c Peak region was defined in two ways (see table in bottom) First one was used, which gave us N data = 284 ± 157 stat ± 21 sys Second window was used for systematic Peak region (GeV) N events in peak Signal events Comb Bg fraction (%) signal to bg ratio ± ± 8 72 O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

8 Double J/psi production at DØ experiment 8/24 Prompt fraction Prompt fraction Events D, log scale L xy, σ sig =, σ bckg = L xy (cm) 1D : χ 2 /ndf = 121,P = 581 ± 51 2D : χ 2 /ndf = 169,P = 637 ± 82 Data Prompt J/ψ Non-prompt J/ψ MC sum Events D, linear scale L xy, σ sig =, σ bckg = Data Prompt J/ψ Non-prompt J/ψ MC sum L xy (cm) Not so good description at small Lxy, so Refitted with optimized Gaussian Smearing L xy = L xy (1 + σ grandom Gaus(,1)), σ is variated O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

9 Double J/psi production at DØ experiment 9/24 Prompt fraction Variation of smearing Refitted L xy with optimized Gaussian Smearing L xy = L xy (1 + σ grandom Gaus(,1)), σ is variated 1D L xy, σ sig =, σ bckg = 2D L xy, σ sig =, σ bckg = Events 4 3 Data Prompt J/ψ Non-prompt J/ψ MC sum 7 6 Data Prompt J/ψ Non-prompt J/ψ MC sum L xy (cm) Finall prompt fraction: P = 538 ± 61% O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

10 Double J/psi production at DØ experiment /24 Systematics Systematics σ = (N data P)/(ε L A) Component Value Statistical error (%) Systematic error (%) N data Purity ε Luminosity 865fb 1 61 Acceptance Total uncertainties: σ sys = 2% σ stat = 88% O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

11 Double J/psi production at DØ experiment 11/24 Total cross section Total cross section σ = (N data P)/(ε L A) σ(j/ψ J/ψ) Br(J/ψ µ + µ ) = 139 ± 12(stat) ± 28(syst) fb The predicted cross section within k T factorization approach is σ kt = (PDF ) 17 (scale) fb The prediction from NRQCD model is σ NRQCD = 55 +X Y (PDF ) fb O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

12 Double J/psi production at DØ experiment 12/24 Total cross section Estimation of DP fraction from Prompt signal We applied additional cuts on data on Lxy on both J/ψ Tail on distribution is dominated by DP events Events 5 Data Prompt SP J/ψ DP J/ψ Fit 4 MC sum 3 2 Fractions of SP and DP from fit with cut L xy < 25cm P SP = 467 ± 111 P DP = 533 ± Y(J/ψ J/ψ) σ SP = (Ndata new P SP)/(ε L A εp SP ) σ DP = (Ndata new P DP)/(ε L A εp DP ) σ SP (J/ψ J/ψ) Br(J/ψ µ + µ ) = 543 ± 62(stat) ± 157(syst) fb σ DP (J/ψ J/ψ) Br(J/ψ µ + µ ) = 698 ± 91(stat) ± 19(syst) fb O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

13 Double J/psi production at DØ experiment 13/24 Summary Summary Total cross section of prompt double J/ψ events was estimated It has discrepancy with theoretical predictions, but looks reasonable DP and SP fractions are estimated Separate cross section are estimated Thank You!!! O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

14 Double J/psi production at DØ experiment 14/24 Backup Backup O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

15 Double J/psi production at DØ experiment 15/24 Backup Comparison DATA vs MC Comparison DATA vs MC Data (blue) to Monte-Carlo (red) comparison for: a) pt (1stJ/ψ); b) pt (2dJ/ψ); c) η(1stj/ψ); d) η(2dj/ψ) a) b) Events 8 7 Data MC Events Data MC pt, GeV pt, GeV c) d) Events 45 Data 4 MC Events 35 Data MC η, Rad η, Rad O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

16 Double J/psi production at DØ experiment 16/24 Backup Acceptance and efficiency Efficiency To estimate muon ID efficiencies Loose we used single J/ψ DATA and MC Data/MC scale factors are calculated as functions of pt (left) and η (right) ( QCD meeting 4/25/212) Tag&Probe method is used: 1 Tight muon, muon pairs should be at GeV, and Probe with cuts mentioned on slide 4 O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

17 Double J/psi production at DØ experiment 17/24 Backup Acceptance and efficiency Efficiency To estimate muon ID efficiencies Loose we used single J/ψ DATA and MC Data/MC scale factors are calculated as functions of pt (left) and η (right) ( QCD meeting 4/25/212) Tag&Probe method is used: 1 Tight muon, muon pairs should be at GeV, and Probe with cuts mentioned on slide 4 SF 1 SF (a) 6 (b) muon p, GeV/c T muon η O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

18 Double J/psi production at DØ experiment 18/24 Backup Acceptance and efficiency Acceptance and efficiency Acceptance ε sel is a ratio between the number of double Jpsi events with Loose muons on reconstruction and particle/generator levels Including muon ID scale factor: Without reweighting : 14± 2; Rew on pt 1 J/ψ : 143± 2; Rew on pt 2 J/ψ : 139± 2; A ε sel = 141± 13 sys ± 2 stat (see QCD meeting 9/12/212) a)without reweighting b)with reweighting on pt J/ψ Acceptance 5 4 (a) Acceptance 5 4 (b) p, GeV/c T p, GeV/c T O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

19 Double J/psi production at DØ experiment 19/24 Backup Triggers & mass window Triggers & mass window DiMu triggers in different versions: V 15: DMU1 1L1MM2; DMU2 1L1MM2; DMU4 2TAML VX V 155: DMU1 1L1MM2; DMU2 1L1MM2; DMU4 1L1MM2 V 1684: DMU1 2MM2V; DMU2 2MM2V; DMU4 1L1MM2V; DMU5 1L1MM2V 23 GeV mass J/ψ 42 GeV - full mass window (for combinatorial bg study); 285 GeV mass J/ψ 335 GeV - peak mass window (24 events in DATA) JxJ passed cuts All hjaj Entries 855 Mean x 37 Mean y 357 RMS x 4354 RMS y M J x J in MassWin hjxj Entries 22 Mean x 389 Mean y 384 RMS x 5 RMS y O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

20 Double J/psi production at DØ experiment 2/24 Backup Trigger efficiency Trigger efficiency Trigger efficiency was estimated by two methods 1) First used double J/ψ final state with our selection cuts (QCD meeting 2/21/212) ε = n 2 n 1 where n 2 is number of events where at least one of DiMu triggers was fired (logical OR ), and n 1 - number of all events Using this method we get ε trig = 83 ± 28 stat ± 55 sys % 2) Second method used ZBMB data skim (single J/ψ) Efficiency is calculated by same formula, where n 2 is number of events where one of DiMu triggers and ZBMB or ZB trigger was fired, and n 2 - number of all events, where ZB or ZBMB triggers was fired Efficiency by this method: ε trig = 16 ± 45% (one muon pair!) This efficiency was corrected on small prescale factors for DiMu triggers and recalculated for 6 possible combinations of muon pairs in double J/ψ final state Taking into account combinatorics, we get (QCD meeting 6/27/212): ε trig = 648 ± 113% Final efficiency (averaging of the two): ε trig = 726 ± 28 stat ± 95 sys % Error is combination of error on trigger efficiency from first method and error of averaging O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

21 Double J/psi production at DØ experiment 21/24 Backup Variation of smearing Variation of smearing Fraction in 1D case with variation of σ σ sig σ bckg χ2/ndf Fraction Fraction Prompt J/ψ Non-Prompt J/ψ ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 59 Fraction in 2D case with variation of σ σ sig σ bckg χ2/ndf Fraction Fraction Prompt J/ψ Non-Prompt J/ψ ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 71 Weighted average in 1D fit, prompt fraction: P = 522 ± 19% Weighted average in 2D fit, prompt fraction: P = 58 ± 3% Weighted average of fractions in 1D and 2D fit without variations, prompt fraction: P = 597 ± 43% Weighted average in 1D and 2D fit with variations, prompt fraction : P = 538 ± 16% Finall prompt fraction will be: P = 538 ± 61% O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

22 Double J/psi production at DØ experiment 22/24 Backup Estimation of DP fraction from Prompt signal Estimation of DP fraction from Prompt signal We applied additional cuts on data on Lxy on both J/ψ Tail on distribution is dominated by DP events Non-prompt estimation of Purity of Prompt: P p ε p P newp = P p ε p + (1 P p ) ε non p L xy <x, cm εp SP εp SP, Herwig εp DP ε non p P newp P newp, Herwig x=3 971± 4 955±9 964±9 274± 4 85 ± ±39 x=25 966± 3 947±9 96±9 217± ± 33,835 ±34 x=2 958± 3 933± 953± 162± ± 27,87 ±28 x= 915± 5 871±13 94±14 64± ± 13,941 ±14 O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

23 Double J/psi production at DØ experiment 23/24 Backup Estimation of DP fraction from Prompt signal Estimation of DP fraction from Prompt signal DjpsiFDC Lxy <x, cm χ 2 /Ndf Purity, SP Purity, DP x= ± ±148 x= ± ±145 x= ± ±149 x= ± ± 161 Herwig++ Lxy <x, cm χ 2 /Ndf Purity, SP Purity, DP x= ± ±15 x= ± ±145 x= ± ±15 x= ±154 56± 159 Events 5 Data Prompt SP J/ψ DP J/ψ Fit 4 MC sum Events 5 Data Prompt SP J/ψ DP J/ψ Fit 4 MC sum Y(J/ψ J/ψ) Y(J/ψ J/ψ) O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment

24 Double J/psi production at DØ experiment 24/24 Backup Estimation of DP fraction from Prompt signal Estimation of DP fraction from Prompt signal Weighted average for Fractions of SP and DP from fit with cut L xy < 25cm P SP = 467 ± 111 P DP = 533 ± 115 σ SP = (N new data P SP )/(ε L A ε SP p ) σ DP = (N new data P DP )/(ε L A ε DP p ) σ SP (J/ψ J/ψ) Br(J/ψ µ + µ ) = 543 ± 62(stat) ± 157(syst) fb σ DP (J/ψ J/ψ) Br(J/ψ µ + µ ) = 698 ± 91(stat) ± 19(syst) fb O Gogota, D Bandurin, Y Scheglov, Y Yatsunenko, P Svoisky Double J/psi production at DØ experiment