Measurement of B_s→J/ψf₀(980) Branching Fraction

Introduction

Since the B_s mixing observation in 2006 particle physics community is excited by searches for CP violation in B_s→J/ψφ decays. The first results, which used flavor tagging to separate B_s and anti-B_s, showed about 1.5σ deviations from the standard model. In the initial measurements of both Tevatron experiments as well as in the subsequent CDF update a possible contribution from the so-called S-wave contribution was neglected. The S-wave component itself can be non-resonant B_s→J/ψ K⁺K^- decay or decay B_s→J/ψf₀(980) with f₀(980)→K⁺K^-. It was argued that the mild deviation from the SM could have been due to ignoring the S-wave contribution rather than real genuine effect. A summary of the discussion can be find in work of Stone (arXiv:1009.4939). It is also suggested that sufficient signal for the decay B_s→J/ψf₀(980) with f₀(980)→π⁺π- can be used to measure CP violating phase βs^J/ψφ without need of angular analysis. All this generated interest in the decay B_s→J/ψf₀(980).

Several estimations for R_f0/φ, the ratio of branching fractions between B_s→J/ψf₀(980) and B_s→J/ψφ, exist based on theoretical calculations as well as on comparison to D_s decays. They vary in wide range of 0.1 to 0.5. Here we present observation of the B_s→J/ψf₀(980) decay with f₀(980)→π⁺π- in CDF data and a measurement of R_f0/φ. The analysis is based on 3.8 fb^-1 of data collected by dimuon trigger.

Further information can be found in the arXiv:1106.3682.

Results

List of Figures

• Figure 1: J/ψπ⁺π- invariant mass spectrum (eps) (png)
• Figure 2: J/ψK⁺K- invariant mass spectrum (eps) (png)
• Figure 3: Physics backgrounds derived from simulated events (eps) (png)
• Figure 4: J/ψπ⁺π- invariant mass spectrum with fit projection (eps) (png)
• Figure 5: Likehood profile for number of B_s→J/ψf₀(980) candidates (eps) (png)
• Figure 6: J/ψK⁺K- invariant mass spectrum with fit projection (eps) (png)
• Figure 7: Likehood profile for number of B_s→J/ψφ candidates (eps) (png)
• Figure 8: Dipion invariant mass for B_s→J/ψf₀(980) signal (eps) (png)
• Figure 9: Helicity angle distribution of positive muon (eps) (png)
• Figure 10: Distribution of absolute value of cosine of helicity angle of positive muon (eps) (png)
• Figure 11: Helicity angle distribution of positive pion (eps) (png)
• Figure 12: Distribution of absolute value of cosine of helicity angle of positive pion (eps) (png)
• Figure 13: Comparison of R_f0/φ measurements (eps) (png)