Evidence for X(3872)→J/ψπ+π−

We report the first evidence for X(3872) production in two-photon interactions by tagging either the electron or the positron in the final state, exploring the highly virtual photon region. The search is performed in e+e−→e+e−J/ψπ+π−, using 825 fb−1 of data collected by the Belle detector operated at the KEKB e+e− collider. We observe three X(3872) candidates, where the expected background is 0.11±0.10 events, with a significance of 3.2σ. We obtain an estimated value for ˜ΓγγB(X(3872)→J/ψπ+π−) assuming the Q2 dependence predicted by a c¯c meson model, where −Q2 is the invariant mass squared of the virtual photon. No X(3915)→J/ψπ+π− candidates are found.Received 11 July 2020Revised 14 December 2020Accepted 22 February 2021DOI:https://doi.org/10.1103/PhysRevLett.126.122001Published 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 productionParticles & Fields