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 Σb and Σb*
• Only Λb

0 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