Transcript An Investigation on Part of the Work Done by the B Physics Group at

An Investigation on Part of the
Work Done by the B Physics
Group at CDF
Ye Li
Graduate Student
UW – Madison
1. New Heavy Baryons Σb and Σb*
• Only Λb0 Directly Observed Before
• Heavy Quark Effective Theory (HQET)
– Heavy Quark: mQ→Infinity
– Good Quantum Numbers: Angular Momentum
& Flavors ( of light quarks )
– Two Light Quarks: Diquark ( 3×3 = 3 + 6 )
• Antisymmetric Λ- type (Isospin I=0)
• Symmetric Σ- type (Isospin I=1)
• Spins
– Spin - 3/2: Σ* ( complete flavor symmetry of
three quarks )
– Spin - 1/2: Σ & Λ ( partially antisymmetric
configuration )
• Theoretical Prediction:
• The Fully Reconstructed Decay Mode
– Σb*±→Λb0π±; Σb±→Λb0π±;
– Λb0→Λc+π¯, Λc+→p K¯ π+
• Measurement Result (Unit: Mev/c2)
– m(Σb+) = 5808+2.0-2.3(stat.) ± 1.7(syst.)
– m(Σb¯) = 5816+1.0-1.0(stat.) ± 1.7(syst.)
– m(Σb*+) = 5829+1.6-1.8(stat.) ± 1.7(syst.)
– m(Σb*¯) = 5837+2.1-1.9(stat.) ± 1.7(syst.)
2. Measurement of B Lifetime and
Extraction of ΔΓCP/ΓCP
• Two-body Charmless Decays of Bs and Bd
– Bs → K+ K– Bs → K+ π– Bd → K+ π– Bd → π+ π-
• First measurement of Their Lifetimes
• Measurement (Unit: ps)
– τ(Bd) = 1.51 ± 0.08(stat) ± 0.02(syst)
– τ(Bs→K+K-) = 1.53 ± 0.18(stat) ± 0.02(syst)
• Combine the Latest HFAG Average of the
Bs Lifetime in Flavor Specific Decays:
τ(Bs FS)= 1.454 ± 0.040 ps
• Result
ΔΓCP/ΓCP (Bs→ K+K-) = -0.08 ± 0.23 ± 0.03
• My Question:
– Does flavor specific decay here refer to the
decays of pure Bs or Bs-bar?
– Is ΔΓCP the decay width with CP breaking, and
ΓCP the decay width with CP conserved?
– What is q1 in the expression of α parameter?
(see the diagram on the next slide)
– How to read the Likelihood scans on the next
slide?
• Likelihood Scan
3. The Rare Decays Bs(d)→ μ+ μ• Powerful Tool to Probe for Physics beyond
the SM
• SM prediction: BR( Bs → μμ ) ≈ 3.8x10-9
• Branching Ratio Enhanced in Various
Extensions to the SM
• Result: World's best limits
– BR( Bs → μμ ) < 1.0 x 10-7 @ 95% CL
BR( Bd → μμ ) < 3.0 x 10-8 @ 95% CL
– BR( Bs → μμ ) < 8.0 x 10-8 @ 90% CL
BR( Bd → μμ ) < 2.3 x 10-8 @ 90% CL
• ?
4. Measurement of the relative
cross sections of χc1 & χc2
• Based on 1.1 fb-1
• χc → J/ψ γ
• Measurement (B.F.= Branching Fraction)
– σ(χc2)/σ(χc1) = 0.70 ± 0.04 (stat.)± 0.04
(sys.)± 0.06 (B.F.), for prompt production
– σ(χc2)/σ(χc1) = 0.25 ± 0.07 (stat.)± 0.01
(sys.)± 0.02 (B.F.), for B decay production
• My Questions:
– Can we measure the cross section directly,
not just the ratio between two cross sections?
– Why PT is so important? Why we never
consider the momentum in the longitudinal
direction, just because it’s hard to measure?
– What is the prompt production?
•Thank You
All data and plots acquired from CDF B physics group internal webpage