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Heavy Flavor PhysicsAt the Tevatron

Cheng-Ju S. Lin(Fermilab)

Aspen Winter Conference

Aspen, Colorado 13 February 2006

CDF

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Gold Mine for Heavy Flavor Physics

Mixing:Bs, Bd, D0

Lifetimes:b, Bs, Bc,

B+, Bd …

New particles:X(3872), Xb,

Pentaquarks, …

Mass measurements:Bc, b, Bs, …

Rare decay searches:Bs,

D0 , …

Production properties:(b), (J/), (D0), …

CP Violation:Acp(Bhh),

Acp(D0K), …

B and D Branching ratios

SURPRISES!?

Exciting time at the Tevatron for heavy flavor physics!!!

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Flavor Creation (annihilation)

q b

q b

Flavor Creation (gluon fusion)

bg

g b

Flavor Excitationq q

bg

b

Gluon Splitting

bg

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 (B0, B+, b, Bs, 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

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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

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b Lifetime

• Lifetime measurements are important tests of Heavy Quark Expansion (HQE)

• Long standing ~2 effect between theory and experiment on (b)/(B0). Experiment on the low side

• CDF + D0 has measured the b

lifetime using fully reconstructedb J/

• Better proper time resolution than semileptonic mode

• Combine with c channel, Tev has the largest fully reconstructed b sample in the world

CDF

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b LifetimeCDF

CDF (370pb-1):

pssyststatb )(02.0)(45.1)( 14.013.0

Tarantino, et al.hep-ph/0203089

NLO

Experiment(world avg)

CDFResult

• Active theoretical work to accommodate data• CDF’s new result sits in the theory preferred region• Need more experimental inputs to resolve the issueD0 (250pb-1):

pssyststatb )(04.0)(22.1)( 22.018.0

PRL 94 102001 (2005)

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s LifetimeCDF

D0 and CDF measure Bs lifetime in semileptonicdecay: Bsl+ Ds

- X

400pb-1

D0:(Bs)=1.420±0.043(stat) ±0.057(syst) ps (Best in the world) CDF:

(Bs)=1.381±0.055(stat) ± (syst) ps0.0520.046

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• Bc has short lifetime and small production rate

• Full reconstruction allows for precise mass measurement• New CDF analysis

– Tune Bc 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 Bc

bc

udcc

J/Bc

Bc: changeK to a

c Mass MeasurementCDF

9Mass(Bc) = 6275.2 +/- 4.3 +/- 2.3 MeV/c2

Num(events)FIT=38.9 sig 26.1 bkgbetween 6.24-6.3Significance > 6over 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

CDFc Mass Measurement

• Recent lattice calculations predict Bc mass with

~20 MeV precision !!

M(Bc)CDF = 6275.2 ± 4.3 ± 2.3 MeV/c2 (hadronic)

M(Bc)LAT = 6304 ± 12 MeV/c2+18-0

c Lattice Calculations

I.F. Allison et al., PRL 94 172001 (2005)

M(Bc)D0 = 5950 ± 140 ± 340 MeV/c2 (semileptonic)

CDF

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CDFc Lifetime

• Bc lifetime extracted from Bc J/ e sample

• More stat than hadronic mode

• But also more background too

• CDF Bc lifetime measured with J/+e channel (360pb-1)

0.474 +0.074/-0.066 0.033 ps (Best in the world)• D0 Bc lifetime measured with J/+ channel (210pb-1)

0.448 +0.123/-0.096 0.121 ps • Theoretical prediction: 0.55 0.15 ps

V. Kiselev, hep-ph/0308214

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• In the B0 system: physical mass eigenstates flavor eigenstates

00

00

BBB

BBB

H

L

(ignoring CP violation)

• Time evolution of the two states is governed by the time-dependent Schrödinger equation and in the limit << m:

mte)B ob (B

mte) Bob (B

Γt

Γt

cos1Pr

cos1Pr

21002100

where: = H- L (lifetime difference) = (H+ L)/2 m = mH- mL (mass difference)

oscillation frequency(Bd md , Bs ms)

} ms=10ps-1

Review of B0 System

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• Measurement of Bs -> K+K- lifetime (=L) in 360pb-1

• Mass fit as in BR and CP measurements• Lifetime fit:

•Extraction of (CP)/(CP)•This measurement gives cL = 458 53 6 m•HFAG average gives weighted average: (L

2 +H2) /(L + H)

•Extract H•Thus derive =-0.080 0.23 (stat) 0.03 (syst)

Extract froms K+ K- LifetimeCDF

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Summary of s / s Measurements

PRL 95 171801 (2005)

PRL 94 102001 (2005)

• CDF BsK+K- (measure L): 360pb-1

=-0.080 0.23 (stat) 0.03 (syst)

•D0 BsJ/(measure H, Bs): 220pb-1

=0.24 (stat) (syst)

• CDF BsJ/ (measure L and H): 210pb-1

=0.65 (stat) 0.01 (syst)0.250.33

0.280.38

0.030.04

Both CDF and D0 have >x2 more data to analyze

• In the Standard Model B mixing occurs via the box diagram:

• A measurement of B0 oscillation frequency,

specifically md, is the most direct way to extract |Vtd|

Study semileptonic B decays

b cVcb

l

l

b uVub

Vtd

V ub/Vcb

Im

Re

(,)

BJ/ Ks,D+D-, etc…

• Study of B0 oscillation provides an important test of SM and probes the origin of CP violation

Bs0 – Bs

0 Oscillations

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• md has been measured to within ~1% (md =0.507±0.004ps-1, HFAG2005) However, extraction of |Vtd| is severely limited by theoretical uncertainties:

222

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2

2

6 )( tdtbQCDBB

W

ttB

Fd VVfB

m

mFmm

Gm

ddd

~15% uncertainty on dd BB fB

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2

2

2

td

ts

Bd

Bs

td

ts

BBB

BBB

d

s

VV

mm

VV

BfmBfm

mm

ddd

sss

• The problem can be circumvented by measuring Bs mixing. Dominant theoretical uncertainties cancel in the ratio:

New lattice result

(assume Vts=Vcb)

• Sounds like a good approach to measure |Vtd|, but… ms is expected to be large (much larger than md)

Bs0 – Bs

0 Oscillations

041.0026.021.1

(~3% uncertainty)

N = # of eventsfBs= Bs fractionD2 = flavor tagging powert = proper time resolution

1. Enriched sample of Bs0 decays

2. Determine the flavor of Bs0 at production and decay

3. Reconstruct the decay length & boost of the Bs0proper decay time

The significance of the analysis can be estimated using the Moser formula:

2)tσsm(21

B

2

ef 2DNceSignifican

s

Proper time resolution has contribution from decay length and boost

222

t

pcpL

t

constant grows linearly with proper time

ms =10ps-1

c

Lt

Key Ingredients of Bs Mixing Analysis

Bs Signal Sample CDF

Bs Ds (where Ds, K* K, 3)Bs Ds 3 (where Ds, K* K)

~1100 fully reconstructed Bs

~17K semileptonic Bs

CDF Preliminary (350pb-1)

Bs Ds (where Ds, K* K)

~34K semileptonic Bs (610pb-1)

Ds mass peak

MKK (GeV/c)

(350pb-1)

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-

- Exclude ms value at 95% C.L. in regions where A+1.65A< 1

- Sensitivity at 95 % C.L. is at

ms value for which 1.65A=1

• Amplitude fit : tme

tme

st

st

cosA1)B (B Prob

cosA1)B (B Prob

210

s0s

210

s0s

- 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 Bs mixing signal

HFAG 2004 World

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Amplitude Fit Results CDF

D0 Result: Sensitivity = 9.5 ps-1

Exclusion: ms < 7.3 ps-1 @95%CL

CDF Result: Sensitivity = 13.0 ps-1

Exclusion: ms < 8.6 ps-1 @95%CL

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World Average CDF

New Tevatron results improved the worldms limit from 14.5 to 16.6 ps-1 @ 95%CL

Tevatron contribution

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stretched Fall 2005

Baseline

Spring 2005

Bs Mixing ProjectionCDF

• 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

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Summary CDF

• 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 ms regions at 3-sigma level. Tevatron is finally “in the game”

• Stay tuned!!!