Triangle singularity in the production of T cc+ (3875) and a soft pion

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*+D0 at short distances followed by their binding into T-cc(+). TheT(cc)(+) can also be produced by the creation of D*+D*+ 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.

Automated summary

The double-charm tetraquark meson T-cc(+)(3875) can be produced in high-energy proton-proton collisions. It can be formed by the creation of charm mesons D*+D0 at short distances followed by their binding, or by the creation of D*+D*+ at short distances followed by their rescattering. A narrow peak is observed in the T-cc(+)pi(+) invariant mass distribution, 6.1 MeV above the threshold, with a width of about 1 MeV, due to a charm-meson triangle singularity. 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)(+) events accompanied by pi+ with energy less than the mass of 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.