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B physics at the Tevatron

B physics at the Tevatron. UK HEP Forum “ From the Tevatron to the LHC ” The Cosener's House, Abingdon,UK April 24-25, 2004 Rick Jesik Imperial College London Representing the D Ø and CDF collaborations. at 2 TeV. at Z 0. at (4S). B physics at hadron colliders. Pros

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B physics at the Tevatron

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  1. B physics at the Tevatron UK HEP Forum “From the Tevatron to the LHC” The Cosener's House, Abingdon,UK April 24-25, 2004 Rick Jesik Imperial College London Representing the DØ and CDF collaborations

  2. at 2 TeV at Z0 at (4S) B physics at hadron colliders • Pros • Large production cross section • All b species produced • B, B0, Bs, Bc, b, b • Cons • Inelastic cross section is a factor of 103 larger with roughly the same pT spectrum • Many decays of interest have BR’s of the order 10-6 • Large combinatorics and messy events

  3. The CDF Run II detector • The CDF detector has undergone extensive upgrades • New silicon vertex detector • inner layer at 1.35 cm • New central tracker • Extended m coverage • Time of flight detector • Second level impact parameter trigger • Allows all hadronic b triggers

  4. The DØ Run II detector • The DØ detector has undergone very extensive upgrades • Silicon vertex detector • |h| < 3.0 • Central fiber tracker and pre-shower detectors • 2 T solenoid magnet • Low pT central muon trigger scintilators • New forward m system • L2 silicon track trigger commissioning now

  5. DØ extended tracking coverage Data from semileptonic decays (B  m D X) pT spectrum of soft pion from D*D0 || for kaons from D*D0 • Tracks are reconstructed • over a wide  range • starting from pT = 200 MeV

  6. B triggers at the Tevatron • Dimuons • pT> 1.5 - 3.0 GeV • CDF central, DØ out to eta of 2 • Single muons • DØ: very pure central track matched muons with pT > 4 GeV, presence of additional tracks used at medium lums, impact parameters only used at high lums • CDF: pT > 4 GeV/c, 120 m < d0(Trk) < 1mm, pT(Trk) > 2 GeV/c • Two displaced vertex tracks - hadronic sample • CDF: pT(Trk) >2 GeV/c, 120 m < d0(Trk) < 1mm, SpT > 5.5 GeV/c

  7. Hadroproduction of heavy quarks flavor creation flavor excitation gluon splitting • NLO processes contribute with the same magnitude as LO ones • Lead to different kinematic correlations • DR, Df, pT1 vs. pT2 R.D. Field - hep-ph/0201112

  8. b-quark cross sections at the Tevatron • Run 1 measured x-sections were a factor of two or three higher than the central values of the theory at the time.

  9. Large uncertainties • Experimental uncertainties • We don’t measure b-quarks, only B-hadrons • Fragmentation uncertainty – Peterson is not correct • B decay products often not fully reconstructed • Must extrapolate to B-hadron, then b-quark pT • Theoretical uncertainties • hard scatter really needs NNLO – scale factors (x2) • quark mass (10%), PDF’s (20%) • kT effects and fragmentation • Correlations between the above often not included in theory vs. experiment comparisons • Was this merely a 2 s discrepancy? – or more?

  10. An exotic explanation • SUSY gluino production and decay to b-quarks • Berger, Tait, Wagner • Also produce like sign BB hadrons and influence mixing measurements

  11. New LO and NLO B-meson fragmentation functions determined from recent data Binnewies, Kniehl, Kramer Next to leading log resumation and re-tuned frag. functions: FONLL Cacciari, Nason Improvements in theory

  12. Open charm cross sections • Charm production probes the same hard scatter processes as beauty, but has different fragmentation – good cross check of theory

  13. Kpp D0p Open charm cross sections • Same level of agreement or disagreement between data and theory (FONLL) as for beauty

  14. Inclusive J/y cross section • CDF’s new muon trigger capabilities extend the J/y pT acceptance down to 0 – was 5 GeV in Run I.

  15. Differential B J/ycross section Assume a b-hadron pT spectrum Unfold pT(Hb) from pT(J/y) using MC New b-hadron pT spectrum Iterate to obtain the correct pT spectrum b-hadron x-section d/dpT(Hb)

  16. Differential ds/dpT(B) as function of pT(B) • (ppB, |y|<0.6)* BR(B J/y)* BR(J/ym+m-)= 24.5  0.5(stat)  4.7(syst) nb • (ppb, |y|<0.6)= 18.0  0.4  3.8 mb

  17. Comparison to theory • FONLL, a la Cacciari, Frixione, Mangano, Nason, Ridolfi • Impressive agreement with new data! • But…the measured inclusive x-section is at the same level as the Run I exclusive one – it should be 10-15% higher, due to the increase in beam energy.

  18. Fully reconstructed B’s • Better for cross section measurement – no missing decay product extrapolation uncertainties • Also very nice for correlations – hadron vs. other lepton or jet, or even other hadron!

  19. More fully reconstructed B’s • These states are not accessible at B-factories • CP violation in Bs, very small in SM – good place to look for new physics • Bc coming soon

  20. b and BS masses M(Bs) = 5365.50  1.29 (stat)  0.94 (sys) MeV/c2 M(B) = 5620.4  1.6 (stat)  1.2 (sys) MeV/c2 World’s best measurements

  21. Excited B hadrons

  22. The X(3872) particle 220 pb-1 • CDF has confirmed BELLE’s discovery of the X particle • 730  90 candidates • ~12 s effect MX = 3871.3  0.7 (stat)  0.4 (sys) MeV/c2

  23. DØ has also confirmed the X(3872) • DØ results: • 300  61 candidates • 4.4s effect • DM = 0.768  0.004 (stat)  0.004 (sys) GeV/ c2 • Direct (non-B) production

  24. X mass range decay length (cm) X(3872) production properties D0 Run II Preliminary dl < 0.02 cm 230 ± 59 evts dl > 0.02 cm 77 ± 25 evts

  25. Is the X charmonium, or an exotic meson molecule? No significant differences between y(2S) and X have been observed yet X(3872) – y(2S) comparison

  26. B+ Lifetimes • 2 D mass, decay length fits CDF: (B+) = 1.66 +/- 0.04 +/- 0.02 ps DØ: (B+) = 1.65 +/- 0.08 +/- 0.12* ps *systematics will be better soon

  27. Bs Lifetime Bs/0=0.89  0.10 Bs/0=0.79  0.14

  28. bJ/  Lifetime B0 J/ K0s bJ/  (Lb) = 1.25 +/- 0.26 +/- 0.10 ps

  29. B lifetimes • Same agreement for DØ • Tevatron B+,B0 lifetimes are competitive • Tevatron b ,Bs are the best

  30. (B+)/(B0) from semileptonic decays Sample compositions: “D0 sample”: + K+ - + (anything except slow ) B+ 82 % B0 16 % Bs 2 % “D* sample”: + D0 - + anything B+ 12 % B0 86 % Bs 2 % Estimates based on measured branching fractions and isospin

  31. (B+)/(B0): results (B+)/(B0) = 1.093  0.021 (stat)  0.022 (syst) Syst. dominated by: - time dependence of slow  reconstruction efficiency - relative reconstruction efficiencies CY - Br(B+ +  D*- + X) - K-factors - decay length resolution differences D0 D*

  32. Bs Mixing World average limit • Measures least known side of unitary triangle • Can not be done at B factories • Difficult measurement – requires: • High yield, good S/B • Oscillations are rapid, so we need excellent lifetime resolution • Flavor tagging

  33. Flavor tagging Opposite jet charge Muon charge Q of the highest pT muon in the event separated in f from the signal B by 2.2 rads. Same side track charge Q of the highest pT (or lowest pTrel) track in a cone (dR < 0.7) around the B Require |Q| > 0.2

  34. Same side tags on 1k BJ/yK events (update with 4k events coming soon) Same side track flavor tag

  35. Flavor Tagging • For hadronic final states, DØ triggers on muon from other B – self tagging (e=1) with even cleaner dilution due to higher pT threshold: ε D2 ~ 80% • Both experiments plan to use electron tags, and CDF will use kaons

  36. B0 mixing: results 250 pb-1 md = 0.506  0.055 (stat)  0.049 (syst) ps-1

  37. Easy trigger on lepton in signal – good statistics DØ: 38 events/pb-1 CDF: 8 events/pb-1 Degraded proper time resolution due to missing neutrino DØ: s(t) ~ 125 – 150 fs CDF: s(t) ~ slightly better Tagging Power DØ: ε D2 ~ 9 - 12% CDF: ε D2 ~ 3 - 8% Bs mixing -semileptonic decays If Dms ~ 15 ps-1 expect a measurement with 500 pb-1

  38. Difficult trigger, small BR’s CDF: uses hadronic trigger 0.7 events/pb-1 DØ: triggers on muon from other B in event: ~ 5 less events, but is starting to see Bd all hadronic events Excelent proper time resolution CDF: s(t) = 67 fs 50 fs using inner silicon layer D0: s(t) ~ 90 - 110 fs will add inner silicon layer in 2005 Tagging Power DØ: ε D2 ~ 80%, self tagging trigger CDF: ε D2 ~ 3 – 8 % Ds D*s and others Bs mixing -hadronic decays Need a few fb-1 of data to reach Dms > 18 ps-1

  39. MC Lumi ~ 180 pb-1 a, g, and direct CPV Resolve the signal composition. Admixture of (at least): B0d  and Charge Conjugate B0d K+ -and C. C. B0s KK-and C. C. B0s K- +and C. C. pT > 2 GeV/c: TOF doesn’t help Combine kinematics with dE/dx to achieve statistical separation Expect ~ 6500 evts / fb-1

  40. Conclusions • Since the 2003 fall shutdown, the Tevatron has shown substantial improvements • Spring is here, and the Tevatron is blooming with beautiful B results • Some have already been published, many are close • B cross sections, masses, and lifetimes • X production studies • Both Experiments are poised to attack Bs mixing in semi-leptonic and hadronic decays. • Bd mixing measured • Expect first Bs results this Fall/Winter • Longer term, many CKM measurements (and other interesting analyses) are in the works.

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