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B S  D S (KK p ) K Selection

B S  D S (KK p ) K Selection. Liming Zhang 05/21/08. DC04 Results. Ref: CERN-LHCb-2007-017. MC Samples (DC06). From Bookkeeping 15.4k B S D S - K + , D S - K + K - p - 938k B S D S - p + , D S - K + K - p - 22M bb inclusive. Signal Background. Distribution of D S daughter.

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B S  D S (KK p ) K Selection

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  1. BS DS (KKp) K Selection Liming Zhang 05/21/08

  2. DC04 Results Ref: CERN-LHCb-2007-017

  3. MC Samples (DC06) • From Bookkeeping • 15.4k BSDS-K+, DS-K+K-p- • 938k BSDS-p+, DS-K+K-p- • 22M bb inclusive

  4. Signal Background Distribution of DS daughter • Reconstruct Bs  DsK • Signal spectrums from DsK MC • Background from b inclusive MC >2 GeV >2.5 >300 MeV

  5. for kaon PID of DS daughter for kaon Will study this background Bd D-K+, D- Kpp, where one p misID to K, to tune thiscut >0 for pion > -10 > -10

  6. Signal Background Distribution for Bachelor Kaon > 0.6 GeV >4 GeV >3

  7. Signal Background Distribution for DS >3 > 2 GeV  21 MeV s ~ 7 MeV < 15

  8. Signal Background Distribution for BS < 4 > 6  50 MeV < 4 s ~ 17 MeV

  9. Signal Background Distribution for BS (cnt’) >0 mm >0.99997

  10. S/B Signal Ds p BG FOM Signal eff. Dsp BG eff. PID on the Bachelor Kaon Optimize FOM=S/sqrt(S+B) for DL(Kp) after the above cuts discussed are applied, where Br(Bs  Ds-+K+-) = 2.2x10-4 and Br(Dsp) = 3.4 x 10-3 used In B mass  50 MeV S/B ~ 6 DL(Kp)>4 Choose >4, signal reduction of 19%, while Dsp background reduced by 95%, S/B ~6

  11. All pions and kaons Kaons : DLL K/pi > 0 : DLL K/proton > -10 Pions : DLL K/pi < 10 DS daughters P > 2000 MeV Pt > 300 MeV sIPS > 2.5 Bachelor Kaon P > 4000 MeV Pt > 600 MeV sIPS > 3 DLL K/pi > 4 DS Mass window 21 MeV Pt > 2000 MeV sIPS > 3 c2 < 15 BS Mass window 50 MeV FSPV > 6 sIPS < 4 c2 < 4 cos > 0.99997 Vz(Ds) – Vz(Ds) >0 mm Selection Criteria Summary

  12. Efficiency (Brunel v30) • Dsp uses the same cuts expect DLL K/pi <4 on the bachelor pion • The cuts applied here are slighter looser than the LHCb note • But the efficiency is lower comparing with the note’s 0.32% • V. Gligorov showed selection study for this mode at CPWG meeting on 3rd April 2008. My efficiency can match with his if using his cuts, which are much looser. • Selection criteria should be re-optimized by Neural Network (NN) or a combined likelihood which includes the correlation b/w the variables

  13. Inclusive b MC (22M) • 6 events (before trigger) in  50 MeV • 2 signal, expect 1.3 • 3 Bs  Ds p, expect 0.2 • 1 combination from bb • 19 events in  500 MeV • 2 signal, expect 1.3 • 3 Bs  Ds p, expect ~0.5 • 4 Bs  Ds m n, m misID to kaon • 1 Lb  Ds* p, p misID to kaon • 1 ghost, ghost means track is not real • 4 Bs  Ds*K in lower mass region • 2 combination from bb • 2 B to final states with K np, one or more p’s misID to kaon Using Tool BackgroundCategory for this study

  14. To Do • To understand BG from specific MCs • To do additional Ds modes • Selection criteria optimization when we have enough BG statistics

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