An Investigation on Part of the Work Done by the B Physics Group at - PowerPoint PPT Presentation

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 Σ b and Σ b * 0 Directly Observed Before • Only Λ b • Heavy Quark Effective Theory (HQET) – Heavy Quark: m Q → 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 – Σ b * ± →Λ b0 π ± ; Σ b ± →Λ b0 π ± ; – Λ b0 →Λ c+ π ¯ , Λ c+ → p K ¯ π + • Measurement Result (Unit: Mev/c 2 ) – m( Σ b+ ) = 5808+2.0-2.3(stat.) ± 1.7(syst.) – m( Σ b¯ ) = 5816+1.0-1.0(stat.) ± 1.7(syst.) – m( Σ b * + ) = 5829+1.6-1.8(stat.) ± 1.7(syst.) – m( Σ b * ¯ ) = 5837+2.1-1.9(stat.) ± 1.7(syst.)

2. Measurement of B Lifetime and Extraction of ΔΓ CP / Γ CP • Two-body Charmless Decays of B s and B d – B s → K + K - – B s → K + π - – B d → K + π - – B d → π + π - • First measurement of Their Lifetimes • Measurement (Unit: ps) – τ (B d ) = 1.51 ± 0.08(stat) ± 0.02(syst) – τ (B s → K + K - ) = 1.53 ± 0.18(stat) ± 0.02(syst)

• Combine the Latest HFAG Average of the Bs Lifetime in Flavor Specific Decays: τ (B s FS)= 1.454 ± 0.040 ps • Result ΔΓ CP / Γ CP (B s → K + K - ) = -0.08 ± 0.23 ± 0.03

• My Question: – Does flavor specific decay here refer to the decays of pure B s or B s -bar? – Is ΔΓ CP the decay width with CP breaking, and Γ CP the decay width with CP conserved? – What is q 1 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 B s(d) → μ + μ - • Powerful Tool to Probe for Physics beyond the SM • SM prediction: BR( B s → 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 χ c1 & χ c2 • Based on 1.1 fb -1 • χ c → J/ ψ γ • Measurement (B.F.= Branching Fraction) – σ ( χ c2 )/ σ ( χ c1 ) = 0.70 ± 0.04 (stat.) ± 0.04 (sys.) ± 0.06 (B.F.), for prompt production – σ ( χ c2 )/ σ ( χ c1 ) = 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 P T 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