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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
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(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