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Study of B s  mmf fK + K -

Study of B s  mmf fK + K -. Supreet Pal Singh Prof. Kajari Mazumdar Prof. J.B.Singh. Introduction to Bs  mmf. B s mass = 5.369 GeV. m +. m +. B 0 s. SV. K +. PV. K -. B s decays in Secondary vertex 2 m 2 tracks from f ( f K + K - BR ~ 50 %).

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Study of B s  mmf fK + K -

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  1. Study of BsmmffK+ K- Supreet Pal Singh Prof. KajariMazumdar Prof. J.B.Singh India-CMS Meeting 27th-28th March 2009

  2. Introduction to Bs mmf Bs mass = 5.369 GeV m+ m+ . B0s . SV K+ PV K- • Bs decays in Secondary vertex • 2 m • 2 tracks from f (fK+ K- BR ~ 50 %) India-CMS Meeting 27th-28th March 2009

  3. The branching ratio has been predicted to be 1.6 x 10-6 in Standard Model. source : C. Q. Geng and C. C. Liu, J. Phys. G 29, 1103 (2003). • The latest update on the Upper limit is from D0 experiment which gives the upper limit as 3.2 x 10-6 • So ,for 10 pb-1 luminosity corresponding we expect to see about 1000 events of the type Bs mmf. India-CMS Meeting 27th-28th March 2009

  4. Work Done • Signal events have been generated through full reconstruction chain in CMSSW_2_2_3 on the line of official data production. • EvtGenLHC generator has been used to generate the signal sample with standard user_decay_file : “GeneratorInterface/EvtGenInterface/data/Bs_phimumu_KK.dec” • The analysis has been done using PAT in CMSSW_2_2_5. India-CMS Meeting 27th-28th March 2009

  5. Signal events • Criteria: 1) MSEL =1, no pt thresholds. 2) 2 muons in the event with PT > 2.5 GeV and |h| < 2.5 • Generator efficiency = 1.85 x 10 -4 • No. of events analyzed = 8607 No. of reconstructed events with 0 muons = 351 No. of reconstructed events with 1 muons = 2098 No. of reconstructed events with 2 muons = 4364 No. of rec. events with more than 2muons = 1794 India-CMS Meeting 27th-28th March 2009

  6. Background events • Main source of background  QCD events. • Not being able to submit the jobs for the dataset : “/InclusivePPmuX/Summer08_IDEAL_V9_v4/GEN-SIM-RECO “ • For the present work the analysis has been done on : “/InclusiveBBmu_Pt20/Summer08_IDEAL_V9_v1/GEN-SIM-RECO “. • For this dataset: MSEL=1 At least one m in the event with PT > 5 GeV and |h| < 2.5 and b-bbar filter. No. of Background events analyzed = 775032 No. of reconstructed events with 0 muons = 13641 No. of reconstructed events with 1 muons = 531322 No. of reconstructed events with 2 muons = 152681 No. of rec. events with more than 2muons = 77388 India-CMS Meeting 27th-28th March 2009

  7. Generator level plots for Bs0 Bs0 h vs PT India-CMS Meeting 27th-28th March 2009

  8. ΔR between Generated and Reconstructed muons For ΔR < 0.01 signal efficiency = 87 % ΔR < 0.01 India-CMS Meeting 27th-28th March 2009

  9. PT & h of reconstructed muons PTm hm Leading pair of muons with opposite charge is selected for the analysis We are loosing the muons in Central region due to low energy India-CMS Meeting 27th-28th March 2009

  10. ΔR between leading pair of muons with opposite charge Signal efficiency = 93 % Bkgd. Efficiency = 59 % ΔR < 1.5 India-CMS Meeting 27th-28th March 2009

  11. Invariant mass of dimuon after ΔR <1.5 cut J/ For mass veto of 3.1 GeV: Signal efficiency = 92 % Bkgd. efficiency = 90 % India-CMS Meeting 27th-28th March 2009

  12. Track Analysis India-CMS Meeting 27th-28th March 2009

  13. Selection of tracks • In the event those tracks (other than muons) are selected which lies in the opposite hemisphere of the leading jet (hjet.htrack < 0) • Kinematic constraint on tracks: Track PT > 400 MeV Track |h| < 2.4 • Tracks assigned mass = 0.493 GeV • The two tracks having opposite charge with invariant mass closest to Mf(1.019 GeV) are chosen. India-CMS Meeting 27th-28th March 2009

  14. Track PT and h distributions PTtrack htrack |h| < 2.4 PT >0.4 GeV The tracks are for signal (Bsmmf) events India-CMS Meeting 27th-28th March 2009

  15. Invariant mass of track1 and track2 Efficiency ~ 67 % Two tracks with opp. charge and 1.005 < M(tk+tk-) < 1.035 GeV are selected. India-CMS Meeting 27th-28th March 2009

  16. Invariant mass of m+m-K+K- India-CMS Meeting 27th-28th March 2009

  17. Future Plans • Study the signal and QCD background simultaneously. • Generate more signal events for high statistics. • Study secondary vertex properties for Bs meson by kinematical fitting of the vertex for dimuon and the Kaons. • Put the kinematic selection cuts to increase the quality of the analysis and check the variation for both signal and background. India-CMS Meeting 27th-28th March 2009

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