2025/01/16 by Luigi Cappiello, Josef Leutgeb, Cappiello, Luigi +5 · 5 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.2501.09699
openalex publication_date 2025/01/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Despite the prominence of tensor mesons in photon-photon collisions, until recently their contribution to the hadronic light-by-light (HLbL) scattering part of the anomalous magnetic moment of the muon has been estimated to be at the level of only a few 10-12. A recent reanalysis within the dispersive approach has found that after resolving the issue of kinematic singularities in previous approaches, a larger result is obtained, a few 10-11, and with opposite sign as in previous results, when a simple quark model for the transition form factors is employed. In this paper, we present the first complete evaluation of tensor meson contributions within a hard-wall model in holographic QCD, which reproduces surprisingly well mass, two-photon width, and the observed singly virtual transition form factors of the dominant f2(1270). Due to a second structure function that is absent in the quark model and in lowest-order resonance chiral theory, the result for aμ turns out to be positive instead of negative, and also with a magnitude of a few 10-11. We find that the infinite tower of tensor mesons permits to fill the gap in the symmetric longitudinal short-distance constraint on the HLbL amplitude left by the contribution of axial vector mesons. Matching the corresponding leading-order OPE result leads to two-photon couplings consistent with the observed combined effects of the ground-state f2,a2,f2' multiplet and a total aμTensor contribution of +12.4× 10-11; with an Fρ fit this is reduced slightly to +11.1× 10-11. A contribution of this size from the tensor sector could explain the tension between the most recent dispersive and lattice results for aμHLbL.