Measurement of total and differential cross sections of central exclusive $\pi^+\pi^-$ production in proton-proton collisions at $5.02$ and $13~\mathrm{TeV}$

Central exclusive production of $\pi^+\pi^-$ pairs is investigated with the CMS detector in proton-proton collisions at the LHC at center-of-mass energies of $5.02$ and $13~\mathrm{TeV}$. The theoretical description of these non-perturbative processes, which are not sufficiently explored experimentally at the LHC, pose a significant challenge to models. The two exclusive pions are identified in the CMS silicon tracker based on specific energy loss, while the absence of other particles is ensured by calorimeter information. The total and differential cross sections of exclusive central $\pi^+\pi^-$ production are measured as functions of invariant mass, transverse momentum, and rapidity of the $\pi^+\pi^-$ system in the fiducial region defined as $p_{\rm T}(\pi) > 0.2~\mathrm{GeV}$ and $|\eta(\pi)| < 2.4$. The production cross sections in the four resonant channels f$_0(500)$, $\rho^0(770)$, f$_0(980)$, and f$_2(1270)$ are also measured. These results represent the first measurement of this process at the top LHC collision energy.