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

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 *. Only Λ b 0 Directly Observed Before Heavy Quark Effective Theory (HQET) Heavy Quark: m Q →Infinity

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

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  1. An Investigation on Part of the Work Done by the B Physics Group at CDF Ye Li Graduate Student UW – Madison

  2. 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)

  3. Spins • Spin - 3/2: Σ* ( complete flavor symmetry of three quarks ) • Spin - 1/2: Σ& Λ ( partially antisymmetric configuration ) • Theoretical Prediction:

  4. 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.)

  5. 2. Measurement of BLifetime 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)

  6. 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

  7. 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?

  8. Likelihood Scan

  9. 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

  10. 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

  11. ?

  12. 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

  13. 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?

  14. Thank You All data and plots acquired from CDF B physics group internal webpage

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