Penn CDF B Physics Overview Joseph Kroll – Penn DOE Site Visit – 8 August 2005

Topics B s & B 0 Flavor oscillations (  m s ) –leadership –flavor tagging –lifetime resolution –trigger monitoring & innovations –semileptonic analysis in dilepton triggered events D meson cross-section measurement B hadron fragmentation properties  b properties –semileptonic branching fractions –J/   (1520) Heijboer Kroll, Jones, Oldeman Jones, Usynin, Kroll Oldeman Chen, Oldeman, Kroll Usynin, Jones, Kroll Yu, Lockyer Heijboer

Experimental Steps for Measuring B s Mixing 1. Extract B 0 s signal – decay mode must identify b-flavor at decay (TTT) Examples: 2. Measure decay time (t) in B rest frame (L = distance travelled) (L00) 3. Determine b-flavor at production “flavor tagging” (TOF) “unmixed” means production and decay flavor are the same “mixed” means flavor at production opposite flavor at decay Flavor tag quantified by dilution D = 1 – 2w, w = mistag probability

Measuring B s Mixing (cont.) 4. Measure asymmetry these formulas assume perfect resolution for t Asymmetry is conceptual: actually perform likelihood fit to expected “unmixed” and “mixed” distributions Measure  m d to validate procedure

For B s Mixing Limits – Measure true  m s Amplitude A = 1 if not actual  m s Amplitude A = 0 CDF preliminary result for Winter 2005 Hadronic & semileptonic modes combined:  m s > 7.9 ps 95% CL

Contributions to Uncertainty in Amplitude Flavor tag effectiveness Signal to noise Proper decay time resolution

Two Types of Flavor Tags Opposite side Same sideBased on fragmentation tracks or B ** + Applicable to both B 0 and B 0 s − other b not always in the acceptance − Results for B + and B 0 not applicable to B 0 s + better acceptance for frag. tracks than opp. side b Reminder: for limit on  m s must know D Produce bb pairs: find 2 nd b, determine flavor, infer flavor of 1 st b

Same Side Flavor Tags Based on correlation between charge of fragmentation particle and flavor of b in B meson Decay of P-wave mesons B ** also contributes to B 0, B + (not B 0 s ) Expected correlations different for B +, B 0, B 0 s TOF

Penn Contribution to CDF B Mixing Effort B Mixing Leadership –J. Kroll w F. Bedeschi leading effort of 70 physicists, 20 institutions –1 st preliminary result on  m s from CDF II in Winter 2005 –Working towards update & publication for Fall 2005 B flavor identification –developed 1 st Run II flavor tag (opposite side muons from b !  ) –required understanding sample composition of “lepton+SVT” data, used by all members of the B group studying opposite side flavor tags –currently pursuing understanding same-side kaon tagging –1 st step is to measure rate of kaons around B +, B 0, B 0 s (thesis of D.Usynin) – using both dE/dx and TOF for kaon identification –crucial for reliable prediction of dilution – need for limit on  m s B decay time resolution – see talk by A. Heijboer

CDF II, D. Acosta et al., PRL 91, (2003) & C. Chen (UPenn) Ph. D. Dissertation, fermilab-thesis Data above theory – much less discrepancy than Run I B cross-section vs. theory Measurement of Prompt Charm Production 1 st PRL from Tevatron in Run II

 K p Measure Kaon Multiplicity around B’s Example: B s ! D s  candidates dE/dxTOF  K p Can we see a difference in K multiplicity around B 0, B +, B 0 s ?

B Baryon Branching Fractions Compare semileptonic rates to hadronic rates for  b At present Tevatron is the unique accelerator to study B Baryons Current World average  b lifetime lower than expected vs. Use same trigger (two track hadronic) to cancel trigger efficiencies Check with topologically similar B meson decays Thesis: Shin Shan Yu Paper draft in preparation

B Baryon Signals Semileptonic decay modeHadronic decay mode Unknown B baryon production fraction cancels in ratio  B ! D  ) =  b !  c  )  can determine absolute BFs

Future Plans for B Physics Continue leadership role in CDF B Mixing effort Publish measurement of particle species fraction & multiplicity produced in association with B hadrons –apply this measurement to estimate of D for same side tag in B s Continue lifetime resolution studies Pursue additional tagged channels such as dilepton Play a major role in 1 st publication of B s mixing results Ultimately measure B s mixing (a discovery!)

Backup Slides

The Beauty Unitary Triangle  of Chau & Keung parametrization is 

Neutral B Meson Flavor Oscillations Flavor oscillations occur through 2 nd order weak interactions e.g. Same diagrams and formula for  m s for B s except replace “d” with “s” All factors known well except “bag factor” £ “decay constant”  m d = § ps -1 (2%) (PDG 2002) from Lattice QCD calculations – see hep-ph/ From measurement of  m d derive |V * tb V td | 2

B Meson Flavor Oscillations (cont) If we measure  m s then we would know the ratio  m s /  m d Many theoretical quantities cancel in this ratio, we are left with from Lattice QCD calculations – see hep-ph/ Since V ts ¼ V cb this gives us our side R t This is why  m s is high priority in Run II

B Flavor Tagging We quantify performance with efficiency  and dilution D  = fraction of signal with flavor tag D = 1-2w, w = probability that tag is incorrect (mistag) Statistical error  A on asymmetry A (N is number of signal) statistical error scales with  D 2