Why B Physics is Interesting (with a CDF focus)

1. Why B Physics is Interesting(with a CDF focus) Manchester Seminar, March 24, 2004 Dr. B. Todd HuffmanOxford University

2. Outline • B physics areas can probe BSM • Tevatron Status • The CDF B triggers • Some initial experimental results • Show we are doing charm and Bottom physics • Rare Decays • Pentaquark Search (add-on)

3. W+ Vcs W+ Vcd An Experimenter’s eye view on what makes B Physics interesting If Electroweak eigenstates matched QCD eigenstatesthis number, VCS, would equal 1.0

4. Interest in B Physics The CKM matrix, which is expected to be Unitary from CPTinvariance governs these diagonal and off-diagonal transitions. ALL CP violation in the SM resides in those two complex terms. Cabbibo angle d s b u Unitary Matrix: (V11)*(V21) + (V12)*(V22)+ (V13)*(V23) = 0 c There are six of these row-column relations. They formtriangles in the complex plane. t

5. Important CKM triangles 1st and 3rd column (bd)Sides of similar length BIG TRIANGLE d s b g b B0 But Isn’t it reasonable to believe that physics beyond the standardmodel might be small on this scale?

6. Current Constraints on UT(Mainly Babar and Belle, for now) Seems pretty well constrained.At this stage, no one would believe any small mismatch in angles without extremely high precision.

7. Important CKM triangles 2nd and 3rd column (bs)Base is REALLY long! l2 vsl4 Thin Triangle f g d s b BS SM predicts very little CP violation in BS sector.Well Worth Checking!

8. f g t W m- b s b n W W t Bs0 Bs0 Bs0 m+ s b s t W Likely locations for new physics Bs CP violation Mixing D, Bu,d, Bs Rare decays WHY New Physics?

9. t W m- b s b n W W t Bs0 Bs0 Bs0 m- b m+ s b s A,H t W c m+ s t Likely locations for new physics f g Bs CP violation Mixing BR ~ tan6b/m4A (2HDM)

10. 2004 - Tevatron has achieved the initial goal of 5 times the Run-I luminosity (though a bit later than originally hoped). - Expect a Core dataset of 2fb-1 by the end of 2005. - Larger dataset (8 fb-1), which was considered difficult to achieve is now looking possible. Certainly the minimum final integrated Luminosity of 4 fb-1 should be achievable. Post-2000 1995-2000 : substantial ($350m) upgrade - main injector - anti-proton recycler - new synchrotron - upgraded pbar source - Peak Luminosity of 6.8x1031cm-2s-1 have been achieved, 6x1031cm-2s-1 is common.

11. The detector CDF-II COT Plug Calorimeter silicon Muon Chambers

12. The CDF Detector in Run-II CDF Detector New: Time of Flight (TOF): some hadron ID New: Silicon (SVT) online Si tracker: Select high IP tracks from b and c @ trigger level(First time at a hadron collider !) Improvements over Run-I -Silicon Detector : 3-D tracking, 5 layers: B vertex, track IP resolution, -Faster Drift Chamber : Momentum measurement -Greater muon coverage : Select b, c m

13. Level 1 Hardware 2.5MHz in 50KHz out Rejection ~50 Level 3 Software 500Hz in 75Hz out Rejection ~5-10 A Trigger is Required • Level 2 • Hardware – ish • 50KHz in • 500Hz out • Rejection ~100 Note:These are ‘in principle’ upper limits on rates.

14. 396ns CLK 14 in all R 4 storage buffers hold events that are waiting for Read-out. Once data is read out, buffer is Empty and is released. Pass L1? Yes F E No E Pipelined TriggerAnd Buffered (deadtimeless) Amp. & Dig. Shift Registers (the pipeline) Det. Dump

15. Deadtimeless Trigger Buys CDF • Ability to take data while reading out into Level 2 • Well, as long as there’s a free buffer anyway • What does this do for the rate? • Takes 20ms for Level 2 to make up its mind. • With no buffer you just have to wait, meanwhile, every 396ns, an event passes you by. • Deadtime  10%; then L1 trigger rate must be 5KHz • With enough buffers, L1 can take data while L2 decides…so rate can potentially equal the L2 decision rate of 50KHz.

16. D d0 B d0 Impact parameter Trigger If we have B mesons, we get tracks with high impact parameter.

17. Data Samples: B and Charm Using the high Impact Parameter (IP) (Hadronic) trigger Select events by requiring : -2 tracks with IP>100 mm - Opposite charge - track PT > 2GeV/c - sum 2-track PT > 5.5 GeV/c 35mm  33mm resol  beam  s = 48mm 0.5M Charm decays at CDF 10-20% come from B: Great Potential for B and Charm Physics, opens at least as many avenues as J/y trigger

18. m J/y m mm Trigger (includes J/y) • Two muons of at least 1.5-2.0 GeV/c Transverse Momentum • Muons are mainly central (|h|<1.1) • Good match between muon chamber and COT track. • Silicon used to distinguish prompt from B production.

19. B±/B0 Lifetime Ratio

20. B Hadron Lifetimes: Expectations and Existing CDF Data • In the naive quark spectator model, the decay is a three body decay common to all b hadrons. • (NLO) QCD predicted deviations in ≈ agreement with data Heavy Quark Expansion Experiment • τ(B+)/τ(Bd) = 1.06± 0.021.074± 0.014 • τ(Bs)/τ(Bd) = 1.00± 0.01 0.948 ± 0.038 • ΔΓs/ Γs≈ 0.1 <0.54 (CL=95%) • τ(Λb)/τ(Bd) = 0.90 ± 0.05 0.796 ±0.052 The main goal is to measure the ratios accurately.

21. B±/B0 Lifetime • Method I • Define ‘signal’ region • Define background region • Fit Background to short-lived gauss. and long-lived exponential parts • Use unbinned Loglikelihoood fits • Fix Background fit parameters • Fit (UB likelihood) to the signal region with exp convol. with resolution • Method used as Check and for systematic studies

22. B±/B0 Lifetime Ratio • Method II • Multivariate fit to mass and lifetime in each decay channel. • Using the J/y and the B vertex were tested against pull distributions in Monte Carlo. • J/y vertex is better estimator. • Good for combined results • Goodness of fit determined by running Toy Monte Carlo experiments • CL’s are 3.4%, 35.2%, 25.6%, and 26.3% in the 4 cases. • Used for final numbers.

23. Bs: t = 1.330 + 0.148(stat)-0.129(stat) ± 0.02 (syst) ps Heavy Quark Effective Theory predicts lifetime differences. Difference in lifetime between CP-even and CP-odd states of the Bs meson (DG/G) is a measurement related to mixing in SM. Total Data = 140pb-1 CDF Run-II Preliminary BS-> J/yf

24. B±/B0 Lifetime Ratio Signal and Sideband fit (method I) • Results are combined as weighted averages with correlations between mass, ct, and resolution scale factor included. • Results: CDF Run-II Preliminary B+: ct = 499 ± 12(stat) ± 6 (sys) mm B0: ct = 446 ± 15(stat) ± 8(sys) mm t+/t0 = 1.119 ± 0.046(stat) ± 0.014(sys)

26. m- W b m- b A,H Bs0 u,c,t n c m+ m+ s t W Limits on B and D mm(uses the TTT) s

27. Limits on Bs,dmm • Blind Analysis • uses the di-Muon trigger. • NBsd = 2*sB*BR(Bs,dm+m-)*L*e*acc. • L is the integrated Luminosity • The factor of 2 includes both particle and antiparticle • Efficiency and acceptance use a Monte Carlo estimate. • This is checked by doing the same for J/y K± . • Background estimate comes from MC simulations of Bpp, Kp, and KK decays. • Cuts are significance-optimised using MC of signal and a high background data sample.

28. Limits on Bs,dmm • Loose cut on lifetime generates background sample for determining background shape vs. Isolation cuts. • Expected Background ~ 0.59 ± 0.22 and 0.54 ± 0.20 events • One event seen in signal overlap region. • Current limit: • Bd < 1.5x10-7 @ 90% CL • Bs < 5.8x10-7 @ 90% CL

29. Limits on Bs,dmm Assumes no increases in muon coverage (uses central muons only) or changes in the analysis optimisation. SM BR predicts ~ 3.8x10-9

30. Limits on D mm • Blind Analyses that use the Two Track Trigger (the SVT) • Comparison can then be made to the Cabbibo suppressed D0p+p- decay mode in the same data sample, removing trigger bias and most efficiency differences in the ratio. • NCL is 90% Confidence Level limit on the number of signal events seen.

31. MisIdentified Kaon fraction Limits on D mm Fit to data used to determinethe Number of D0pp. Fit variations to estimate systematics. Use ‘normal’ D0 K p to estimate fake muon rates. High sideband used as well. Expected Background = 1.7 events

32. Limits on D mm CDF Preliminary: BR(D0mm) < 2.4x10-6@ 90% Previous best measurement: E771 < 4.1x10-6 Standard Model: ~ 10-13

33. The Effect on SUGRA. CurrentCDF Limit 2fb-1 Reach based on simple extrapolation of previous plot Current limits for BS->m m are already ruling outsome SUGRA paramter space. Ref: hep-ph/0310042 v1

34. The effect on SUGRA. Current CDF limitBr(BS->m m) Ref: hep-ph/0108037 v3 Values of the other SUGRAparameters used: M1/2 = 450 GeV/c2 M0 = 350 GeV/c2 A0 = 0 m > 0 Top mass = 175 GeV/c2 2fb-1 reach? SM Prediction Difference in anomalous muon mag. Moment between theory and the SM

35. Pentaquark search • Bound state of 5 quarks • Several possible states are predicted and some have claims to being found • LEPS at Spring-8 (Japan), Phys. Rev. Lett., 92, 012002 (2003). • ITEP DIANA Collaboration, hep-ex/0304040. • CLAS Collaboration at JLAB, hep-ex/0307018. • These report on the state.

36. Pentaquark Search NA49 also claimed observations ofthe pentaquark cascade (X) states.(hep-ex/0310014) CDF New Search: Search conducted in:Hadronic Two Track & Jet20 triggers Trig. tracks not explicitly required Decay Chains for Search: X--X-p- and X0X-p+X-Lp- with LppX- leaves hits in the silicon detector.

37. All opposite sign trackswithin 5MeV/c2 of L mass Lxy > 1cm Combination combined with a pion track candidate3-track Combination used to seed a search for X- hits in the silicon detector. L p- p Lxy>1cm FindingX- X Can Leave Hits in the Silicon Detectors p-

38. No. of X:19,150±244 No. of X:16,736±218 Combine the X- candidates with another pion to look for the X(1860) Pentaquark state. We also expect to see the standard X(1530). Yield of X(1860) relative to X(1530) yield could be used to calibrate yields unless there is severe penalty in production mechanism for X(1860) in p-pbar collisions at 2 TeV vs low energy (18 GeV ) pp collisions of CERN SPS.

39. Pentaquark Search – TTT Data From peak below and No. of X- previously shown. N(X(1530))=2,182±82

40. Pentaquark Search – Jet20 Data No equivalent signal found. CDF cannot confirm NA49 observation More Jet 20 data Also looking for Q butsearch is not complete.

41. Pentaquark Production Limits • Yields quoted relative to the production of the X(1530) which is seen in both data sets.

42. Conclusions • Low Energy measurements of B meson properties are likely first indicators of new physics in our accelerators. • Seen CDF detector operating • Appreciate the unique ability of the Trigger • Results on Rare Decays • Non-result in Pentaquarks…but still interesting and puzzling. • Much more to come this year!

43. Back-up Slides Oxford Seminar

44. 3.0 GeV/c cut on p+ momentum removes X0(1530) state due to phase space.

46. Limit Determination Fit to Gaussian + background, float only the background. Find Likelihood for N X(1860)’s where N is varied from -1000 to +1000 and plot that Likelihood (see above).90% and 95% CL’s are then taken from this plot.If you don’t like this: talk to Louis Lyons, Chairman of the CDF Statistics

47. LBJ/yL Lifetime: Separate fits to sig. and sideband. B0J/y KS acts as a contol sample due to very similar decay geometry. Largest systematic is from an asymmetric track reconstruction in the COT ~26mm. Work is in progress to add more data and use better track reconstruction.

48. B±/B0 Lifetime RatioSystematic Uncertainties

49. What we need to measure CP violation. • Identify a CP eigenstate • Identify particle flavour at creation. • Particle ID at creation involves an efficiency and whether or not you guess the correct flavour….the ‘Dilution’ D=(R-W)/(R+W).

50. D0 Mixing(work in progress) • Quick look at box diagram reveals why SM predicts essentially no Mixing • Virtual Quarks give main mixing contribution • ‘b’ quark vertex is suppressed on all corners W W