1 / 16

Takahiro Matsumoto, Belle Collaboration Tokyo Metropolitan University Dec 03 11:50-12:10

Tagging with fully reconstructed B’s in B-factory experiments. Takahiro Matsumoto, Belle Collaboration Tokyo Metropolitan University Dec 03 11:50-12:10. Interesting decays B → ul n B → tn, Knn B → D tn etc. B. e- (8GeV). e + (3.5GeV). Υ(4S). p. B. Full Recon.

clinton-gomez
Download Presentation

Takahiro Matsumoto, Belle Collaboration Tokyo Metropolitan University Dec 03 11:50-12:10

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Tagging with fully reconstructedB’s in B-factory experiments Takahiro Matsumoto, Belle Collaboration Tokyo Metropolitan University Dec 03 11:50-12:10

  2. Interesting decays • B → uln • B → tn, Knn • B → Dtn • etc B e- (8GeV) e+(3.5GeV) Υ(4S) p B Full Recon. Fully reconstructed B tagging －Offline single B meson beams with known p（B）, flavor. －Large advantage to study decays including n and t Full reconstruction efficiency = O(0.1%) Need large data sample ⇒unique at B factories

  3. The KEKB Collider (8 x 3.5 GeV, X angle) World record: L=(1.0 x 1034)/cm2/sec Accumulated 158/fb by this summer • 152 million BBbar pairs KEKB Collider

  4. Event display for fully reconstructed two B’s

  5. Kinematicvariables for the Υ(4S) Energy difference: Beam-constrained mass:

  6. Fully reconstructed B tagging • B decay patterns • Hadronic : ~ 80% • A lot of decay modes with Br ≤ O(1%) • Semileptonic : ~20% • Mainly for BD*(e,m)n (~10%), B momentum unknown • Reconstruction • Hadronic : Collect as many modes as possible • Requires many CPU time due to multiple combination • Semileptoic : • Neutrino reconstruction with assumption of rest B at U(4s) CM frame

  7. B’s Reconstruction [Hadronic] • Collect known major modes [Belle] [ low efficiency, but high purity ] BD(*)(p,r,a1)-, D(*)DS(*), (J/Y, Y(2s), cc1)K(*) • Semi-inclusive reconstruction, BD(*)X [BaBar] [ high efficiency, but low purity ] X=n1p±n2K±n3KSn4p0, total charge ±1 n1 + n2≤ 5, n3≤2, n4≤2 Treatment of the multiple candidates • Select the best reduced c2 events to each mode ( from M(D), M(D*)-M(D), DE etc.) • Select the mode with the best purity

  8. BD(*)(p,r,a1)- • Main hadronic B decay sample [ Br ~ 1% ] • D(*) is D0, D+, D*0 or D*+ [ recon. from D*D(p,g) and DKnp ] • Recon. eff. : ~0.17% for B±, ~0.07% for B0 • High purity ~0.8 w/ 152 million BBbar

  9. BD(*)Ds(*) • Br ~1%, but low yield due to D and Ds reconstruction • Ds(*)+ is recon. from Ds*+Ds+g, Ds+K+K-p+,KsK+p+p-,KSK+ • ~7% yield of BD(*)(p,r,a1)- • Moderate purity ~ 0.6 Neutral B Charged B S= 4390 S= 8700 w/ 152 million BBbar

  10. BCharmonium • Color suppressed modes [ Br ~ 0.1% ] • Reconstructed modes • B-J/YK-, B0 (J/Y, Y(2s), cc1)KS, J/YK*0 • ~9% yield of BD(*)(p,r,a1)- • Very high purity ~0.95 [ due to clean recon. of J/Y l+l- ] Charged B Neutral B S= 9373 S= 7275 (CP modes= 3119) w/ 152 million BBbar

  11. BD(*)X [ semi-inclusive , BaBar ] • BD(*)（n1p±n2K±n3KSn4p0）± • In total, 1097 combinations! • c.f. 64 combinations for BD(*)(p,r,a1)- Mbc w/ lepton (Pl*>1 GeV/c) • High eff. • ~0.5% for B±, ~0.3% for B0 • Low purity: ~ 0.25 • ~0.67 w/ lepton (P*l>1 GeV/c) in recoil B side S ~30k BD(*)X is categorized by Mx region depending on purity and select the best purity mode for each event ( also mode dep. threshold cut on purity is applied ). *hep-ex/0307062 for Vub paper with BXuln w/ 89 million BBbar

  12. BHadronic, Summary • BD(*)(p,r,a1)-, D(*)DS(*), (J/Y, Y(2s), cc1)K(*) • eff. ~ 0.2% (0.1%) for charged (neutral) B • 150k B±, 69k B0 in 152 million BBbar sample • High purity ~ 0.81 • BD(*)X • eff. ~ 0.5 % (0.3%) for charged (neutral) B • Low purity ~ 0.25 How to improve eff. and quality? • Add more decay modes • ex. D+ K-p+p+, KSp+ add ~50% with D+K-p+p+p0 • Study BD(*)X in detail. By understanding structure of X, we can optimize the selection criteria further • Further cut tuning • etc. Steady improvement will be possible

  13. B’s reconstruction [Semileptonic] • Reconstructed modes • B-D0l-n ( Br=2.15±0.22% ) • D0K-p+, K-p+p0, K-p+p+p-, KSp0 *B-D*0l-n ( Br= 6.5 ±0.5%) is automatically included in the sample

  14. B-D(*)0l-n • B± tagged events = 714k, eff. = 1.7% • Purity for B-D(*)0l-n = 13.9% (Missing mass)2 for neutrino Large eff., but Large combinatoric backgrounds w/ 85 million BBbar

  15. Application to physics analysis • Fully reconstructed B tag sample is widely used for physics analysis since B-factory experiments succeeded to accumulate large sample of BBbar pairs • BXuln ( for Vub analysis ) • hep-ex/030762 [BaBar] • BKnn, tn • PRL86(2001)2950 [CLEO], BaBar conference paper • For the decays with low multiplicity (BKnn, tn etc.), we can suppress combinatoric background significantly, then semileptonic B tag ( ~1% eff. ) sample can be also utilized • Other interesting physics analyses are also expected • BD(*)tn, Btt etc. or detailed study of inclusive B decays

  16. Conclusions • A large number of fully reconstructed B sample is already available in B-factory  Provide tools for innovative B physics analysis • Reco. eff. • ~ 0.15%(0.4%) for Hadronic B tag [ () is for BD(*)X ] • ~ 1.7% for Semileptonic B tag* * useful for low multiplicity B decays • We already have a sample of more than 105 fully reconstructed B mesons. We expect a lot of interesting physics results with these sample in near future

More Related