Penn CDF B Physics Overview

Joseph Kroll – Penn DOE Site Visit – 8 August 2005

Topics

• Bs & B0 Flavor oscillations (ms)– 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

Heijboer

Kroll, Jones, Oldeman

Jones, Usynin, Kroll

Oldeman

Chen, Oldeman, Kroll

Usynin, Jones, Kroll

Yu, Lockyer

Heijboer

Experimental Steps for Measuring Bs Mixing

1. Extract B0s 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 Bs 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 md

to validate procedure

For Bs Mixing Limits – Measure Amplitude

@ true ms

Amplitude A = 1 if not actual ms

Amplitude A = 0

CDF preliminary result for Winter 2005

Hadronic & semileptonic modes combined: ms > 7.9 ps-1 @ 95% CL

Contributions to Uncertainty in Amplitude

Flavor tag effectiveness

Signal to noise

Proper decay timeresolution

Two Types of Flavor Tags

Opposite side

Same side Based on fragmentation tracks or B**

+ Applicable to both B0 and B0s

− other b not always in the acceptance

− Results for B+ and B0 not applicable to B0s

+ better acceptance for frag. tracks than opp. side b

Reminder: for limit on ms must know D

Produce bb pairs: find 2nd b, determine flavor,infer flavor of 1st b

Same Side Flavor Tags

Based on correlation betweencharge of fragmentation particleand flavor of b in B meson

Decay of P-wave mesonsB** also contributesto B0, B+ (not B0

s)

Expected correlationsdifferent for B+, B0, B0

sTOF

Penn Contribution to CDF B Mixing Effort

• B Mixing Leadership– J. Kroll w F. Bedeschi leading effort of 70 physicists, 20 institutions

– 1st preliminary result on ms from CDF II in Winter 2005

– Working towards update & publication for Fall 2005

• B flavor identification– developed 1st 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

– 1st step is to measure rate of kaons around B+, B0, B0s (thesis of

D.Usynin) – using both dE/dx and TOF for kaon identification

– crucial for reliable prediction of dilution – need for limit on ms

• B decay time resolution – see talk by A. Heijboer

CDF II, D. Acosta et al., PRL 91, 241804 (2003) & C. Chen (UPenn) Ph. D. Dissertation, fermilab-thesis-2003-14

Data above theory – much less discrepancy than Run I B cross-section vs. theory

Measurement of Prompt Charm Production

1st PRL fromTevatron in Run II

Kp

Measure Kaon Multiplicity around B’s

Example: Bs! Ds candidates

dE/dx TOF

K

p

Can we see a difference in K multiplicity around B0, B+, B0s?

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 mode Hadronic decay mode

Unknown B baryon production fraction cancels in ratioB ! 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 Bs

• Continue lifetime resolution studies

• Pursue additional tagged channels such as dilepton

• Play a major role in 1st publication of Bs mixing results

• Ultimately measure Bs mixing (a discovery!)

Backup Slides

The Beauty Unitary Triangle

of Chau & Keungparametrization is

Neutral B Meson Flavor Oscillations

Flavor oscillations occur through2nd order weak interactions

e.g.

Same diagrams and formula for ms for Bs except replace “d” with “s”

All factors known well except “bag factor” £ “decay constant”

md = 0.489 § 0.008 ps-1 (2%) (PDG 2002) from Lattice QCD calculations – see hep-ph/0406184

From measurement of md derive |V*tbVtd|2

B Meson Flavor Oscillations (cont)

If we measure ms then we would know the ratio ms/md

Many theoretical quantities cancel in this ratio, we are left with

from Lattice QCD calculations – see hep-ph/0406184

Since Vts ¼ Vcb this gives us our side Rt

This is why ms ishigh 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 D2