Flavoured axions in the tail of Bq → μ+μ− and B → γ form factors

• Published in: The journal of high energy physics Vol. 2021; no. 9; pp. 1 - 46
• Main Authors: Albrecht, Johannes, Stamou, Emmanuel, Ziegler, Robert, Zwicky, Roman
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2021; Springer Nature B.V; Springer Nature; SpringerOpen
• Subjects: Atoms & subatomic particles; Beyond Standard Model; Classical and Quantum Gravitation; Couplings; Decay rate; Elementary Particles; Flavor (particle physics); Form factors; High energy physics; Kinematics; Perturbative QCD; Physics; Physics and Astronomy; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Quantum chromodynamics; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Quarks; Regular Article - Theoretical Physics; Relativity Theory; Standard model (particle physics); String Theory; Sum rules; Symmetry; Beyond Standard Model; Perturbative QCD
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP09(2021)139

A bstract We discuss how LHC di-muon data collected to study B q → μμ can be used to constrain light particles with flavour-violating couplings to b -quarks. Focussing on the case of a flavoured QCD axion, a , we compute the decay rates for B q → μμa and the SM background process B q → μμγ near the kinematic endpoint. These rates depend on non-perturbative B q → γ (*) form factors with on- or off-shell photons. The off-shell form factors — relevant for generic searches for beyond-the-SM particles — are discussed in full generality and computed with QCD sum rules for the first time. This includes an extension to the low-lying resonance region using a multiple subtracted dispersion relation. With these results, we analyse available LHCb data to obtain the sensitivity on B q → μμa at present and future runs. We find that the full LHCb dataset alone will allow to probe axion-coupling scales of the order of 10 6 GeV for both b → d and b → s transitions. As a spin-off application of the off-shell form factors we further analyse the case of light, Beyond the Standard Model, vectors.