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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
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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!!!