1 / 23

Heavy Flavor Physics At the Tevatron Cheng-Ju S. Lin (Fermilab ) Aspen Winter Conference

Heavy Flavor Physics At the Tevatron Cheng-Ju S. Lin (Fermilab ) Aspen Winter Conference Aspen, Colorado 13 February 2006. Gold Mine for Heavy Flavor Physics. New particles: X(3872), X b , Pentaquarks, …. B and D Branching ratios. Lifetimes: DG, L b , B s , B c ,

quon-blevins
Download Presentation

Heavy Flavor Physics At the Tevatron Cheng-Ju S. Lin (Fermilab ) Aspen Winter Conference

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. Heavy Flavor Physics At the Tevatron Cheng-Ju S. Lin (Fermilab) Aspen Winter Conference Aspen, Colorado 13 February 2006

  2. Gold Mine for Heavy Flavor Physics New particles: X(3872), Xb, Pentaquarks, … B and D Branching ratios Lifetimes: DG, Lb, Bs, Bc, B+, Bd … Mixing: Bs, Bd, D0 Production properties: s(b), s(J/y), s(D0), … Mass measurements: Bc, Lb, Bs, … CP Violation: Acp(Bhh), Acp(D0Kp), … Rare decay searches: Bsm+m-, D0m+m- , … SURPRISES!? Exciting time at the Tevatron for heavy flavor physics!!!

  3. Heavy Flavor Physics In Hadron Environment b b g g b g q b b b b b q g g g q q Flavor Excitation Flavor Creation (gluon fusion) Flavor Creation (annihilation) Gluon Splitting b’s produced via strong interaction decay via weak interaction • Tevatron is great for heavy flavor: • Enormous b production cross-section, • x1000 times larger than e+e- B factories • All B species are produced (B0, B+,Lb, • Bs, etc…) • However, • Inelastic (QCD) background is about • x1000 larger than b cross-section • Online triggering and reconstruction is • a challenge: collision rate ~1MHz  • tape writing limit ~100Hz

  4. CDF and D0 Detectors • CDF: • Excellent silicon vertex detector • Good particle identification (K,p) • Good momentum and mass • resolutions • D0: • Extended tracking and • muon coverage • Good electron identification • New innermost-layer silicon • detector will be installed in • March

  5. Lb Lifetime • Lifetime measurements are important tests of • Heavy Quark Expansion (HQE) • Long standing ~2s effect between theory and experiment • on t(Lb)/t(B0). Experiment on the low side • CDF + D0 has measured the Lb • lifetime using fully reconstructed • Lb J/y L • Better proper time resolution than • semileptonic mode • Combine with Lcp channel, Tev • has the largest fully reconstructed • Lb sample in the world

  6. Lb Lifetime Experiment (world avg) NLO Tarantino, et al. hep-ph/0203089 CDF Result • Active theoretical work to • accommodate data • CDF’s new result sits in the • theory preferred region • Need more experimental • inputs to resolve the issue CDF (370pb-1): D0 (250pb-1): PRL 94 102001 (2005)

  7. Bs Lifetime CDF: t(Bs)=1.381±0.055(stat) ± (syst) ps 0.052 0.046 D0 and CDF measure Bs lifetime in semileptonic decay: Bsl+n Ds- X 400pb-1 D0: t(Bs)=1.420±0.043(stat) ±0.057(syst) ps (Best in the world)

  8. Bc Mass Measurement u d p b c c c Bc J/y • Bc has short lifetime and small production rate • Full reconstruction allows for precise mass measurement • New CDF analysis • Tune Bc selection on reference B+ J/y K+ data • After selection cuts are fixed, “open box” • Wait for events to become a significant excess • Measure properties of the Bc Bc: change K to a p

  9. Bc Mass Measurement Num(events)FIT= 38.9 sig 26.1 bkg between 6.24-6.3 Significance > 6s over search area 0.36 fb-1 ~0.5 fb-1 ~0.6 fb-1 ~0.7 fb-1 ~0.8 fb-1 Mass(Bc) = 6275.2 +/- 4.3 +/- 2.3 MeV/c2 Most precise measurement of Bc mass

  10. Bc Lattice Calculations • Recent lattice calculations predict Bc mass with ~20 MeV precision !! M(Bc)CDF = 6275.2 ± 4.3 ± 2.3 MeV/c2 (hadronic) M(Bc)D0 = 5950 ± 140 ± 340 MeV/c2(semileptonic) +18 -0 M(Bc)LAT = 6304 ± 12 MeV/c2 I.F. Allison et al., PRL 94 172001 (2005)

  11. Bc Lifetime • Bc lifetime extracted from Bc J/y e n sample • More stat than • hadronic mode • But also more • background too • CDF Bc lifetime measured with J/y+e channel (360pb-1) 0.474 +0.074/-0.066 0.033 ps (Best in the world) • D0 Bc lifetime measured with J/y+m channel (210pb-1) 0.448 +0.123/-0.096 0.121 ps • Theoretical prediction: 0.55  0.15 ps V. Kiselev, hep-ph/0308214

  12. Review of B0 System } where:  = H- L (lifetime difference)  = (H+ L)/2 m = mH- mL (mass difference) oscillation frequency (Bdmd , Bsms) • In the B0 system: physical mass eigenstates flavor eigenstates (ignoring CP violation) • Time evolution of the two states is governed by the time-dependent • Schrödinger equation and in the limit << m: ms=10ps-1

  13. Extract DG from Bs K+ K-Lifetime • Measurement of Bs -> K+K- lifetime (=tL) in 360pb-1 • Mass fit as in BR and CP measurements • Lifetime fit: • Extraction of DG(CP)/G(CP) • This measurement gives ctL = 458  53  6 mm • HFAG average gives weighted average: (tL2 +tH2) /(tL + tH) • Extract tH • Thus derive DG/G =-0.080  0.23 (stat) 0.03 (syst)

  14. Summary of DGs / Gs Measurements • CDF BsK+K- (measure tL): 360pb-1 DG/G =-0.080  0.23 (stat) 0.03 (syst) • D0 BsJ/y f (measure tH, tBs):220pb-1 • DG/G =0.24  (stat)  (syst) • CDF BsJ/yf (measure tL and tH): 210pb-1 • DG/G =0.65  (stat) 0.01 (syst) 0.28 0.38 0.03 0.04 PRL 95 171801 (2005) 0.25 0.33 PRL 94 102001 (2005) Both CDF and D0 have >x2 more data to analyze

  15. Bs0 – Bs0 Oscillations a Im  Vub/Vcb  Vtd l (,) n c b Vcb g b l n u b Vub Re (0,1) (0,0) BJ/ Ks,D+D-, etc… • In the Standard Model B mixing occurs via the box diagram: • Study of B0 oscillation provides an important test of SM and probes • the origin of CP violation • A measurement of B0oscillation frequency, • specifically md, is the most direct way • to extract |Vtd| Study semileptonic B decays

  16. Bs0 – Bs0 Oscillations ~15% uncertainty on • md has been measured to within ~1% (md =0.507±0.004ps-1, HFAG2005) • However, extraction of |Vtd| is severely limited by theoretical • uncertainties: • The problem can be circumvented by measuring Bs mixing. • Dominant theoretical uncertainties cancel in the ratio: (assume Vts=Vcb) New lattice result (~3% uncertainty) • Sounds like a good approach to measure |Vtd|, but… • Dms is expected to be large (much larger than Dmd)

  17. Key Ingredients of Bs Mixing Analysis • Enriched sample of Bs0 decays • Determine the flavor of Bs0 at production and decay • Reconstruct the decay length & boost of the Bs0proper decay time The significance of the analysis can be estimated using the Moser formula: ms =10ps-1 N = # of events fBs= Bs fraction eD2= flavor tagging power t = proper time resolution Proper time resolution has contribution from decay length and boost grows linearly with proper time constant

  18. Bs Signal Sample CDF Preliminary (350pb-1) Ds mass peak MKKp (GeV/c) Bs Dsm n (where Dsfp, K* K) Bs Dsp (where Dsfp, K* K, 3p) Bs Ds 3p (where Dsfp, K* K) ~34K semileptonic Bs (610pb-1) ~1100 fully reconstructed Bs ~17K semileptonic Bs (350pb-1)

  19. Amplitude Fit Primer • A modified form of Fourier analysis is used to search for periodic signal •  Amplitude Fit ( NIM A384, 491 (1997) ) • Amplitude fit : - - Fit for oscillation amplitude “A” for a given ms value - Expect “A” = 1 for frequency = true ms Expect “A” = 0 for frequency  true ms Bd mixing signal HFAG 2004 World • If no signal is observed: - Exclude ms value at 95% C.L. in regions where A+1.65A< 1 - Sensitivity at 95 % C.L. is at ms value for which 1.65A=1 No Bs mixing signal

  20. Amplitude Fit Results D0 Result: Sensitivity = 9.5 ps-1 Exclusion: Dms < 7.3 ps-1 @95%CL CDF Result: Sensitivity = 13.0 ps-1 Exclusion: Dms < 8.6 ps-1 @95%CL

  21. World Average New Tevatron results improved the world Dms limit from 14.5 to 16.6 ps-1 @ 95%CL Tevatron contribution

  22. Bs Mixing Projection Fall 2005 stretched Baseline Spring 2005 D0 Projections Fall 2005 yield • CDF projections were made ~ 1year ago • CDF has surpassed the baseline projection • Goal is to reach “stretched” by Sum 2006: • - Same-side kaon tag • - Partially reconstructed Bs*Bs • At “stretched”, CDF will be probing SM • region at 3-sigma level this summer • D0 has an aggressive plan • to improve sensitivity: • - additional modes • - electron flavor tag • - evt-by-evt likelihood

  23. Summary • With 1fb-1 of data/experiment, heavy flavor physics • at the Tevatron is in full swing. In this talk, I have only • touched the “tip of the iceberg” • Tevatron is entering precision era on measuring a broad • spectrum of B and Charm properties. Many measurements • are unique to Tevatron and some are complementary to • the B-factory physics program • One exciting prospect this summer: Tevatron will start • probing the SM Dms regions at 3-sigma level. Tevatron • is finally “in the game” • Stay tuned!!!

More Related