Triangle Singularity in the Production of T⁺_cc(3875) and a Soft Pion at Hadron Colliders

¹ Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universität Bonn, D-53115 Bonn, Germany
² Department of Physics, The Ohio State University, Columbus, OH 43210, USA
³ School of Physics, Shandong University, Jinan, Shandong 250100, China

^* e-mail: heliping@hiskp.uni-bonn.de
^** e-mail: braaten.1@osu.edu
^*** e-mail: ingles.27@buckeyemail.osu.edu
^**** e-mail: jiangjun87@sdu.edu.cn

Published online: 22 December 2022

Abstract

If the double-charm tetraquark meson T⁺_cc(3875) is a loosely bound molecule, it can be produced in high-energy proton-proton collisions by the creation of the charm mesons D^∗+D⁰ at short distances followed by their binding into T⁺_cc. It can also be produced by the creation of D^∗+D^∗+ at short distances followed by their rescattering into T⁺_ccπ⁺ through a charm-meson triangle loop. A charm-meson triangle singularity produces a narrow peak in the T⁺_ccπ⁺ invariant mass distribution 6.1 MeV above the threshold with a width of about 1 MeV. The fraction of T⁺_cc that are accompanied by π⁺ with E < m_π is estimated to be roughly 3%. The fraction of T⁺_cc events with T⁺_ccπ⁺ in the narrow peak from the triangle singularity could be comparable.