1 / 18

Recent B Physics results from D Ø

Recent B Physics results from D Ø. The B Physics program in D Ø Run II Current analyses – First results Conclusions. Chicago . p. p. 1.96 TeV. Booster. p. CDF. DØ. Tevatron. p. p sou rce. Main Injector & Recycler. Tevatron at FermiLab. 1992-1996: Run I (125 pb -1 )

ramona-chapman
Download Presentation

Recent B Physics results from D Ø

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. Recent B Physics results from DØ • The B Physics program in DØ Run II • Current analyses – First results • Conclusions

  2. Chicago  p p 1.96 TeV Booster p CDF DØ Tevatron p p source Main Injector & Recycler Tevatron at FermiLab • 1992-1996: Run I (125 pb-1) • Discovered top • 2001-2005: Run IIa (2 fb-1) • E=1.8 TeV •  1.96 TeV • L = 2 x 1031cm-2 s-1 •  1 x 1032 cm-2 s-1 • 2005-2008: Run IIb (~10 fb-1)

  3. DØ: one of the two major detectors at Tevatron • New in Run IIa: • Solenoid • Si + fiber tracker • Preshowers • Forward muon system

  4. DØ as a place to do B physics • s (pp  bb) = 150 mb at 2 TeV (~10 kHz) • Lots of B’s of all kinds (Bd, Bs, Lb, Bc, …) • Rich B physics program • Cross section measurements • Bs mixing • B lifetime • CP violation in Bd and Bs • Rare decays • In many cases Tevatron is complementary to B factories

  5. Triggers • Have to go down from 2.5 MHz crossing rate to 50 Hz writing to disk (0.25 MB/event) • Sophisticated 3-level trigger system • Most useful triggers for B physics so far: dimuon triggers (simple and unprescaled) • Central (||<1): pT>3.5 GeV • Forward (1<||<2): pT>2-2.5 GeV • Coming soon (this summer): • L2 track trigger (track match to m/e) • L2 silicon trigger (displaced vertices)

  6. B jet cross section (1) • Step 1: Begin with m in jet cross section • Unlike most of the other analyses, this one is based on a relatively small data set (3.4 pb-1)

  7. m+jet T m B jet cross section (2) • Step 2: Extract b content via fit to pTrel distribution • Large b mass  high pTrel

  8. B jet cross section (3) • Step 3: Unfold jet energy resolution (unsmearing) • Measured cross section consistent with Run I results (2-3 times higher than predictions) • Dominant error due to jet energy scale corrections

  9. J/ data sample • Exploit J/  m+m– mode • Results based on 40 pb-1 collected data (75k J/) • Calibration not finalized, mass not in good agreement with PDG

  10. c reconstruction • Observe cin c J/ g • Low energy photons visible through ge+e– conversions • Cannot (yet?) separate c1 and c2mass peaks

  11. B Zoo • We are able to reconstruct exclusive B decays • The first step towards CP violation measurements

  12. B hadrons not produced at B factories • Observe BsJ/  and Lb J/ L • Can do B physics complementary to e+e– B factories

  13. Inclusive B lifetime • Begin with J/ transverse decay length • ctJ/y = Lxy M J/ / pTJ/ • Infer ctB from ctJ/ by applying average MC correction ctB = ctJ/y / <F(pTJ/)> F: correction factor BJ/ X : 17 % Prompt fraction : 83 % Systematic uncertainties: correction factor, fit bias <tB> = 1.561  0.023(stat)  0.073(sys) ps (PDG : 1.564  0.014)

  14. Charged B lifetime • Full reconstruction (B±  J/ K ±): no hadronization or momentum uncertainties • ctB = Lxy M B / pTB <tB> = 1.76  0.24(stat) ps (PDG : 1.674  0.018)

  15. B flavor tagging • Method 1: soft muon tagging • Charge of highest pT muon in the event (excluding those from reconstructed B) gives (opposite-side) b-tag • Method 2: jet charge tagging • Q=S qi pTi / S pTi, count events with |Q|>0.2 • Tagging performance measure: eD2 e = (N right + N wrong) / N all: efficiency D = (N right – N wrong)/(N right + N wrong): dilution

  16. Conclusions • Latest Run IIa D0 B physics results • b-jet cross section • B lifetime • Exclusive B decays • Understanding flavor tagging • Improvements in the future • Track and silicon triggers • More calibration, data understanding underway • Awaiting for large sets of data, lots of Physics ahead !

  17. Summary slide

  18. Recent B physics results from DØ • With the DØ detector upgraded for Run II, our B physics program has started. • Our first results based on 40 pb-1of data include: • B-jet cross section measurement • Observation of B exclusive decays • B lifetime measurements • Understanding of the flavor tagging • In the near future, we’ll have our trigger improved, and we are awaiting for large data sets

More Related