Hadronic Decays Group Report

Transcription

1 Carlo Schiavi on behalf of the Hadronic Decays Group 14 July 211 (B-physics meeting) Carlo Schiavi on behalf of the Hadronic Decays Group Page 1

2 Outlook Cross-section news: D ( )± meson measurements Spectroscopy news: prospect of η c (1S) observation Flavour measurement news: b/c ratio in D samples Carlo Schiavi on behalf of the Hadronic Decays Group Page 2

3 TeV DATA, EF_mbMbts_2_NoAlg,.65 nb D ± production cross section: 2.76 TeV results L. Gladilin D ± production at 2.76 TeV with MBTS 2 Combinations per.5 MeV right charge combinations wrong charge combinations ± fit : N(D* ) = 677 ± " M = ± mod # (" M) =.47 ± "M = M(K!! s ) - M(K!) [GeV] 72.5 MeV.5 MeV Combinations per.5 MeV TeV MC, & 151 combined right charge combinations wrong charge combinations ± fit : N(D* ) = 5981 ± " M = ± mod # (" M) =.42 ± "M = M(K!! s ) - M(K!) (GeV) MeV.1 MeV kinematic range: pt > 3. GeV, η < 2.1 Acc =25.6 ±.5% σ =167± 18 µb (42% of the value at 7 TeV) signal: Gauss mod backgr: A (x m π +) B exp C (x m π +) D ( ) 2.76 and 7 TeV L. Gladilin 7 Carlo Schiavi on behalf of the Hadronic Decays Group Page 3

4 TeV DATA, EF_mbMbts_2_NoAlg,.65 nb 2.76 TeV MC, & 151 combined D ± production cross section: 2.76 TeV results L. Gladilin D ± production at 2.76 TeV with MBTS 2 Combinations per 1 MeV ± fit : N(D ) = 669 ± ± M(D ) = ± mod " (M) = 11.9 ± MeV 1.6 MeV M(K!!) [GeV] Combinations per 1 MeV ± fit : N(D ) = 5124 ± + M(D ) = ± mod "(M) = 13.8 ± M(K!!) (GeV) MeV.4 MeV kinematic range: pt > 3. GeV, η < 2.1 Acc =7.8 ±.2% σ =156± 17 µb (45% of the value at 7 TeV) signal: Gauss mod backgr: exp D ( ) 2.76 and 7 TeV L. Gladilin 8 Carlo Schiavi on behalf of the Hadronic Decays Group Page 4

5 D ( )± production!"#$%&'(")*"+*",&*$,-.'/*1 cross section: 7 TeV %)2* results /&"((* L. Gladilin (3/4'")(*5'46*789::*%)2*;<=>79? Carlo Schiavi on behalf of the Hadronic Decays Group Page

6 Our private MC for η c (1S) Observation prospects for η c (1S): first MC tests L. Gladilin, V. Lyubushkin η mass resolution c Entries 14 Mean ± RMS ± Underflow 1 Overflow [MeV] M sim -M rec based on PYTHIA MinBias use HeavyFlavorHadronFilter to filter out events with η c η c K ± π K via EvtGen S 319 events with η c simulated and reconstructed found 18 events with 4 reconstructed tracks, those tracks were transported to cascade fitter cascade fit was successful in 16 events 14 events pass through loose quality criteria: (npix> && nsct>3) nsct>5 for K S tracks (npix> && nsct>3) for K and π + Will now try to observe η c signal in periods A-B-C of 21 7 TeV data and measure its production cross section Carlo Schiavi on behalf of the Hadronic Decays Group Page 6

7 D flavour ratio: measurement ingredients A. Coccaro, P. Dondero, A. Ferretto, F. Parodi, L. Rossi, C. Schiavi We need a tool for b/c fraction measurement in D samples Many reasons why: b b to c c cross section ratio measurement systematic error reduction in D µ measurement b-tagging efficiency on charm jets (analysis approved, note in preparation) Inclusive cross section ratio measurement presented in the past: trigger request: minimum bias beauty fraction measurement based on D pseudo proper time Most recent news: trigger request: added L1 1 trigger alternative beauty fraction measurement based on D impact parameter Carlo Schiavi on behalf of the Hadronic Decays Group Page 7

8 D flavour ratio: trigger selection A. Coccaro, P. Dondero, A. Ferretto, F. Parodi, L. Rossi, C. Schiavi Complementing MinimumBias with the addition of other triggers (L1 J1) Study bias vs p T (D ) (all D, D in events which passed L1 J1) Full acceptance for p T 25 GeV MinimumBias for p T < 25GeV, L1 J1 otherwise Carlo Schiavi on behalf of the Hadronic Decays Group Page 8

9 D flavour ratio: trigger selection, 21 data A. Coccaro, P. Dondero, A. Ferretto, F. Parodi, L. Rossi, C. Schiavi Entries /.5 MeV 4 3 ATLAS Preliminary s = 7 TeV Entries /.5 MeV 8 6 ATLAS Preliminary s = 7 TeV fit: N(D*) = 68 ± p (D*) T 7 [6,1] GeV (MinBias, A+B) 2 fit: N(D*) = 185 ± 28 p (D*) [1,25] GeV (MinBias, A+B) T M(Kππ s )-M(Kπ) [MeV] M(Kππ s )-M(Kπ) [MeV] Entries /.5 MeV 1 ATLAS Preliminary s = 7 TeV Entries /.5 MeV 4 3 ATLAS Preliminary s = 7 TeV 5 2 fit: N(D*) = 275 ± 26 p (D*) [25,35] GeV (L1_J1, C+D) T 1 fit: N(D*) = 12 ± 19 p (D*) [35,12] GeV (L1_J1, C+D) T M(Kππ s )-M(Kπ) [MeV] M(Kππ s )-M(Kπ) [MeV] High p T bins: need extension to other L1 JX and L1 EMX items Carlo Schiavi on behalf of the Hadronic Decays Group Page 9

10 D flavour ratio: impact parameter fit A. Coccaro, P. Dondero, A. Ferretto, F. Parodi, L. Rossi, C. Schiavi Results of MC pull tests and real data fits have been already presented for the method based on D pseudo-proper time An alternative method has been developed within the same framework, for cross-checks and complementarity, based on D impact parameter The template models: model for resolution: Res = Modified Gauss + Gauss model for charm: Charm = Res model for beauty: Beauty = (Exp + Exp) Res The fit procedure: fix resolution model with fit on MC D sample fix beauty time constants with fit on MC D sample fit b fraction on sideband-subtracted D candidates data or MC signal Carlo Schiavi on behalf of the Hadronic Decays Group Page 1

11 D flavour ratio: impact parameter fit, test on MC A. Coccaro, P. Dondero, A. Ferretto, F. Parodi, L. Rossi, C. Schiavi Minimum bias trigger all candidates with p T (D ) > 4.5 GeV True MC fraction value:.121±.8 (slightly different selection) Carlo Schiavi on behalf of the Hadronic Decays Group Page 11

12 D flavour ratio: impact parameter fit, resolution J. Metcalfe, I. Gorelov, S. Seidel, K. Toms The idea is to get the detector resolution (F D ) from K S π+ π decays data Selection and reconstruction of K S π+ π candidates: vertexing done with VKalVrtFitter track cuts: p T > 1 MeV, N pix > 1, N sct > 6 candidate cut: pointing angle >.999, vertex χ 2 < 15 still working on cleaning up background Resolution parametrization: using a gauss + exp function (same as in CDF study) F D (d ) = α exp d2 2σ 2 + (1 α) exp d λ instead of fixing all variables in the final charm fraction fit on D signal, the ratio of λ/σ is fixed (same as CDF study) First results being finalized! Carlo Schiavi on behalf of the Hadronic Decays Group Page 12