Cross-section measurement of two-photon in-flight annihilation of positrons at s=20 MeV with the PADME detector

Abstract

A measurement of the inclusive cross section of in-flight electron-positron annihilation to photons, e+e−→γγ, is presented using the PADME detector at the Laboratori Nazionali di Frascati. A beam of 430 MeV positrons, corresponding to a center-of-mass energy of 20 MeV, strikes a thin diamond target. The two photons produced in the interaction are detected by an electromagnetic calorimeter made of BGO crystals. The measurement is the first based on direct detection of the photon pair and one of the most precise for positron energies below 1 GeV. It represents an intermediate step in the ultimate PADME goal of searching for dark sector particles and mediators weakly coupled to photons and electrons, with masses ranging from 1 to 20 MeV. The final value, σe+e−→γγ=(1.977±0.018(stat)±0.119(syst)) mb, agrees with next-to-leading-order QED predictions within the 6% experimental uncertainty.6 MoreReceived 8 November 2022Accepted 20 December 2022DOI:https://doi.org/10.1103/PhysRevD.107.012008Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasParticle interactionsGeneral PhysicsParticles & Fields