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Md. Naimuddin (on behalf of CDF and D0 collaboration) Fermi National Accl . Lab Recontres de Moriond 09 th March, 2008. Masses, Lifetimes and Mixings of B and D hadrons. OUTLINE. B physics at the Tevatron Fermilab Tevatron CDF and D0 Detectors Mass measurement Lifetimes
(on behalf of CDF and D0 collaboration)
Fermi National Accl. Lab
Recontres de Moriond
09th March, 2008
Masses, Lifetimes and Mixings of B and D hadrons
B hadrons – Produced as a result of hadronization of b quark
B+( ) = 38%
B0( ) = 38%
Bs( ) = 10%
Bc( ) = 0.001%
Rest b baryons
Highest Luminosity achieved:
Expected: ~7 fb-1 by end of 2009
Theoretical prediction of the masses
Predicted mass hierarchy:
M(Λb)< M(b) < M(b)
E. Jenkins, PRD 55 ,
Searching for b in b-→J/+-
Natural constraints in b-→J/+-
Reconstruction strategy for b
- The final state particles
(p, -, ) have significant
Impact parameter with
respect to the interaction
- - has a decay length of few
- has a decay length of few
- b has a decay length of few
hundred microns, PV
- Reconstruct J/→+-
- Reconstruct →p
- Combine J/+
- Improve mass resolution
by using an event-by
event mass difference
Number of signal events: 15.2 ± 4.4
Mean of the Gaussian: 5.774 ± 0.011(stat) GeV
Width of the Gaussian: 0.037 ± 0.008 GeV
PRL 99, 052001 (2007)
M(Ξb-) = 5792.9 ± 2.5 (stat.) ± 1.7(syst.) MeV/c2
Significance of the observed signal: >7.0
PRL 99, 052002 (2007)
Significance of the observed signal: 5.5
F. Allison et. al, PRL 94, 172001 (2005)
Mass measurement in Bc → J/
The distribution was fitted with a Gaussian for signal and fit returns a total of 5412 signal candidates.
A total of 137 events with invariant mass between 6240 and 6300 MeV/c2 observed. 80.4 are attributed to Bc signal and rest to background.
D0: m(Bc) = 630014 (stat)5 (sys) MeV/c2
From the negative log-likelihood of S+B and background only hypothesis, the signal significance was extracted to be 5.2.
CDF: m(Bc) = 6274.13.2 (stat)2.6 (sys) MeV/c2
Using toy MC the signal significance was extracted to be larger than 8.
Theory: 0.48 0.05 ps (QCD sum rules)
Lifetime measurement in Bc → J/
Most precise measurement to date
Using an unbinned likelihood simultaneous fit to J/ invariant mass and lifetime distributions, a signal of 85680 candidates estimated.
(Bs) = 1.5450.051 ps
(Bs) = 1.5180.025 ps
(Bs) = 1.4560.067 ps
c(Bs) = 455.012.2 (stat) 7.4 (syst) m
CDF: (Bs) = 1.520.040.02 ps
D0: (Bs) = 1.520.060.01 ps
Characterized by mixing parameter:
Measure mixing in D*→D0; D0→K
x’ = x cosK + y sinK
y’ = y cosK - x sinK
y’ = 0.0085 and x’2 = 0.00012
Bayesian probability contour excludes no mixing point at 3.8.
y’ = 0.0097, x’2 = -0.00022
y’ = 0.0006, x’2 = 0.00018
Alternate checks of the significance also resulted in 3.8
Excellent performance by the Tevatron and anti-proton stacking rate.
Total data will be doubled in the next couple of years.
M(Bs2*) = 5839.6±1.1(stat.)±0.7 (syst.)
B1 → B*+-; B*+ → B+
B2* → B*+-; B*+ → B+
B2* → B+-
B0*(J=0), B1*(J=1): Jq = ½, decay via S-wave too broad ( ~ 100 MeV) to be observable.
B1(J=1), B2*(J=2): Jq =3/2, D-wave decay, ~ 10 MeV
m(B2*)-m(B1) 14 MeV
m(B10) = 5720.6±2.4(stat.) ±1.4(syst.) MeV/c2m(B2*0) = 5746.8±2.4 (stat.) ±1.7(syst.) MeV/c2
Significant improvement since
then, theory has included NLO
calculations, but experiments still have large uncertainties
• important to revisit this with data sets now available at the Tevatron
b →J/ ~ 10-4
Combined Semileptonic and hadronic
(LB ) = 1.251- 0.096 + 0.102 ps