# The 34th International Symposium on Lattice Field Theory (Lattice 2016)

24-30 July 2016
Highfield Campus, University of Southampton
Europe/London timezone

## Calculation of hadronic matrix elements contributing to the $B_s-\bar{B}_s$ width difference

27 Jul 2016, 10:40
20m
Building B2a Room 2065 (Highfield Campus, University of Southampton)

### Building B2a Room 2065

#### Highfield Campus, University of Southampton

Talk Weak Decays and Matrix Elements

### Speaker

Dr Matthew Wingate (University of Cambridge)

### Description

The width difference $\Delta \Gamma_s$ is one of three observables, along with the mass splitting $\Delta M_s$ and the semileptonic CP asymmetry $a^s_{\mathrm{SL}}$, whose measurements completely constrain the physics of $B_s-\bar{B}_s$ oscillations. One of the dominant uncertainties in theoretical calculations of the width difference is due to not knowing matrix elements of dimension-7 operators beyond the vacuum saturation approximation. In particular, progress requires a first-principles calculation of the matrix element of $R_2$, a $\Delta B = 2$ operator with a derivative acting on the strange quark field. We discuss our methodology and present preliminary results of a calculation of $\langle B_s | R_2 | \bar{B}_s\rangle$ using nonrelativistic $b$ quarks and highly-improved staggered $s$ quarks on the MILC Collaboration's $n_f = 2+1+1$ configurations.

### Primary author

Dr Matthew Wingate (University of Cambridge)

### Co-authors

Prof. Christine Davies (University of Glasgow) Dr Christopher Monahan (Rutgers University) Prof. G. Peter Lepage (Cornell University) Prof. Junko Shigemitsu (Ohio State University)

 Slides