Triangle Singularity in the Production of $T_{cc}^{+}$(3875) and a Soft Pion

Abstract

The double-charm tetraquark meson $T_{cc}^{+}(3875)$ can be produced in high-energy proton-proton collisions by the creation of the charm mesons $D^{\ast +}{D}^0$ at short distances followed by their binding into $T_{cc}^{+}$. The $T_{cc}^{+}$ can also be produced by the creation of $D^{\ast +}{D}^{\ast +}$ at short distances followed by their rescattering into $T_{cc}^{+}{\pi }^{+}$. A charm-meson triangle singularity produces a narrow peak in the $T_{cc}^{+}{\pi }^{+}$ invariant mass distribution 6.1 MeV above the threshold with a width of about 1 MeV. Well beyond the peak, the differential cross section decreases with the invariant kinetic energy $E$ of $T_{cc}^{+}{\pi }^{+}$ as $E^{-1/2}$. The fraction of $T_{cc}^{+}$ that are accompanied by ${\pi }^{+}$ with $E<m_{\pi }$ is estimated to be roughly 3%. The fraction of $T_{cc}^{+}$ events with $T_{cc}^{+}{\pi }^{+}$ in the narrow peak from the triangle singularity could be comparable.

Comments: 44 pages, 13 figures