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 Mixing: B s, B d, D 0 Lifetimes:  b, B s, B c, B +, B d … New particles: X(3872), X b, Pentaquarks, … Mass measurements: B c,  b, B s, … Rare decay searches: B s     , D 0     , … Production properties:  (b),  (J/  ),  (D 0 ), … CP Violation: Acp(B  hh), Acp(D 0  K  ), … B and D Branching ratios SURPRISES!? Exciting time at the Tevatron for heavy flavor physics!!!

3 Flavor Creation (annihilation) qb q b Flavor Creation (gluon fusion) b g g b Flavor Excitation q q b g b Gluon Splitting b g g g b b’s produced via strong interaction decay via weak interaction Heavy Flavor Physics In Hadron Environment Tevatron is great for heavy flavor: Enormous b production cross-section, x1000 times larger than e + e - B factories All B species are produced (B 0, B +,  b, B s, 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,  ) 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  b Lifetime Lifetime measurements are important tests of Heavy Quark Expansion (HQE) Long standing ~2  effect between theory and experiment on  (  b )/  (B 0 ). Experiment on the low side CDF + D0 has measured the  b lifetime using fully reconstructed  b  J/  Better proper time resolution than semileptonic mode Combine with  c  channel, Tev has the largest fully reconstructed  b sample in the world

6  b Lifetime CDF (370pb -1 ): Tarantino, et al. hep-ph/ NLO Experiment (world avg) 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 D0 (250pb -1 ): PRL (2005)

7  s Lifetime D0 and CDF measure B s lifetime in semileptonic decay: B s  l + D s - X 400pb -1 D0:  (B s )=1.420±0.043(stat) ±0.057(syst) ps (Best in the world) CDF:  (B s )=1.381±0.055(stat) ± (syst) ps

8 B c has short lifetime and small production rate Full reconstruction allows for precise mass measurement New CDF analysis –Tune B c selection on reference B +  J/  K + data –After selection cuts are fixed, “open box” –Wait for events to become a significant excess –Measure properties of the B c bcbc udud cccc  J/  Bc Bc: change K to a   c Mass Measurement

9 Mass(Bc) = / /- 2.3 MeV/c 2 Num(events) FIT = 38.9 sig 26.1 bkg between Significance > 6  over search area 0.36 fb -1 ~0.8 fb -1 ~0.7 fb -1 ~0.6 fb -1 ~0.5 fb -1 Most precise measurement of Bc mass  c Mass Measurement

Recent lattice calculations predict B c mass with ~20 MeV precision !! M(Bc) CDF = ± 4.3 ± 2.3 MeV/c 2 (hadronic) M(Bc) LAT = 6304 ± 12 MeV/c  c Lattice Calculations I.F. Allison et al., PRL (2005) M(Bc) D0 = 5950 ± 140 ± 340 MeV/c 2 (semileptonic)

11  c Lifetime Bc lifetime extracted from B c  J/  e sample More stat than hadronic mode But also more background too CDF B c lifetime measured with J/  +e channel (360pb -1 ) /  ps (Best in the world) D0 B c lifetime measured with J/  +  channel (210pb -1 ) /  ps Theoretical prediction: 0.55  0.15 ps V. Kiselev, hep-ph/

12 In the B 0 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: where:  =  H -  L (lifetime difference)  = (  H +  L )/2  m = m H - m L (mass difference) oscillation frequency (B d   m d, B s   m s ) }  m s =10ps -1 Review of B 0 System

13 Measurement of B s -> K + K - lifetime (=  L ) in 360pb -1 Mass fit as in BR and CP measurements Lifetime fit: Extraction of  (CP)/  (CP) This measurement gives c  L = 458  53  6  m HFAG average gives weighted average: (  L 2 +  H 2 ) /(  L +  H ) Extract  H Thus derive  =  0.23 (stat)  0.03 (syst) Extract  from  s  K + K - Lifetime

14 Summary of  s /  s Measurements PRL (2005) PRL (2005) CDF B s  K + K - (measure  L ): 360pb -1  =  0.23 (stat)  0.03 (syst) D0 B s  J/  (measure  H,  B s ): 220pb -1  =0.24  (stat)  (syst) CDF B s  J/  (measure  L and  H ): 210pb -1  =0.65  (stat)  0.01 (syst) Both CDF and D0 have >x2 more data to analyze

In the Standard Model B mixing occurs via the box diagram: A measurement of B 0 oscillation frequency, specifically  m d, is the most direct way to extract |V td | Study semileptonic B decays b c V cb l l b u V ub       V td  V ub /V cb Im Re (,)(,) B  J/  K s,D + D -, etc… Study of B 0 oscillation provides an important test of SM and probes the origin of CP violation B s 0 – B s 0 Oscillations

16  m d has been measured to within ~1% (  m d =0.507 ± 0.004ps -1, HFAG2005) However, extraction of |V td | is severely limited by theoretical uncertainties: ~15% uncertainty on The problem can be circumvented by measuring Bs mixing. Dominant theoretical uncertainties cancel in the ratio: New lattice result (assume V ts =V cb ) Sounds like a good approach to measure |V td |, but…  m s is expected to be large (much larger than  m d ) B s 0 – B s 0 Oscillations (~3% uncertainty)

N = # of events f Bs = Bs fraction  D 2 = flavor tagging power  t = proper time resolution 1.Enriched sample of B s 0 decays 2.Determine the flavor of B s 0 at production and decay 3.Reconstruct the decay length & boost of the B s 0  proper decay time The significance of the analysis can be estimated using the Moser formula: Proper time resolution has contribution from decay length and boost constant grows linearly with proper time  m s =10ps-1 Key Ingredients of Bs Mixing Analysis

B s Signal Sample B s  D s  (where D s  , K* K, 3  ) B s  Ds 3  (where D s  , K* K) ~1100 fully reconstructed B s ~17K semileptonic B s CDF Preliminary (350pb -1 ) B s  D s  (where D s  , K* K) ~34K semileptonic B s (610pb -1 ) Ds mass peak M KK  (GeV/c) (350pb -1 )

Exclude  ms value at 95% C.L. in regions where A+1.65  A < 1 - Sensitivity at 95 % C.L. is at  m s value for which 1.65  A =1 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 If no signal is observed: A modified form of Fourier analysis is used to search for periodic signal  Amplitude Fit ( NIM A384, 491 (1997) ) Amplitude Fit Primer Bd mixing signal No B s mixing signal HFAG 2004 World

20 Amplitude Fit Results D0 Result: Sensitivity = 9.5 ps -1 Exclusion:  m s < 7.3 ps CDF Result: Sensitivity = 13.0 ps -1 Exclusion:  m s < 8.6 ps

21 World Average New Tevatron results improved the world  m s limit from 14.5 to 16.6 ps 95%CL Tevatron contribution

22 stretched Fall 2005 Baseline Spring 2005 B s Mixing Projection 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 Fall 2005 yield D0 Projections 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  m s regions at 3-sigma level. Tevatron is finally “in the game” Stay tuned!!!