B → K and D → K form factors from fully relativistic lattice QCD

Parrott, W.G., Bouchard, C. and Davies, C.T.H. (2023) B → K and D → K form factors from fully relativistic lattice QCD. Physical Review D, 107(1), 014510. (doi: 10.1103/PhysRevD.107.014510)

Abstract

We present the result of lattice QCD calculation of the scalar, vector and tensor form factors for the B → K ℓ + ℓ − decay, across the full physical range of momentum transfer. We use the highly improved staggered quark (HISQ) formalism for all valence quarks on eight ensembles of gluon-field configurations generated by the MILC collaboration. These include four flavors of HISQ quarks in the sea, with three ensembles having the light u / d quarks at physical masses. In the first fully relativistic calculation of these form factors, we use the heavy-HISQ method. This allows us to determine the form factors as a function of heavy-quark mass from the c to the b , and so we also obtain new results for the D → K tensor form factor. The advantage of the relativistic formalism is that we can match the lattice weak currents to their continuum counterparts much more accurately than in previous calculations; our scalar and vector currents are renormalized fully nonperturbatively and we use a well-matched intermediate momentum-subtraction scheme for our tensor current. Our scalar and vector B → K form factors have uncertainties of less than 4% across the entire physical q 2 range and the uncertainty in our tensor form factor is less than 7%. Our heavy-HISQ method allows us to map out the dependence on heavy-quark mass of the form factors and we can also see the impact of changing spectator quark mass by comparing to earlier HPQCD results for the same quark weak transition but for heavier mesons.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Parrott, Mr William and Davies, Professor Christine and Bouchard, Dr Chris
• Authors: Parrott, W.G., Bouchard, C., and Davies, C.T.H.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Physical Review D
• Publisher: American Physical Society
• ISSN: 2470-0010
• ISSN (Online): 2470-0029
• Published Online: 24 January 2023
• Copyright Holders: Copyright © 2023 American Physical Society
• First Published: First published in Physical Review D 107(1): 014510
• Publisher Policy: Reproduced under a Creative Commons License

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
306883		Research in Particle Physics Theory - Phenomenology from lattice QCD and collider physics	Christine Davies	Science and Technology Facilities Council (STFC)	ST/T000945/1	P&S - Physics & Astronomy