Abstract
| We report a measurement of the exclusive production of pairs of charged pions in proton-proton collisions,
dominated by the process $pp \rightarrow p^{(*)} \pi^{+}\pi^{-} p^{(*)}$, where $\rm p^{(*)}$
stands for a diffractively dissociated proton, the $\pi^{+} \pi^{-}$ pair is emitted at central
rapidities $y$, and the incident protons stay intact or dissociate without detection ${\rm p^{(*)}}$.
The measurement is performed with the CMS detector at the LHC, using a data sample corresponding to an integrated luminosity
of 450 $\mu$b$^{-1}$ collected at a center-of-mass energy of $\sqrt{s}$ = 7 TeV in 2010.
The cross section measured in the phase space defined by pion transverse momentum $p_{\rm T}>0.2$ GeV/c and rapidity $y$ less than 2 is
found to be $20.5 \pm 0.3 (\rm {stat}) (\pm 3.1 \rm {syst}) \pm$ 0.8 (lumi) $\mu$b.
The differential cross sections for $\pi^{+}\pi^{-}$ pairs
as a function of the pion pair invariant mass, $p_{\rm T}$, and $y$, as well as a single-pion differential
cross section as a function of pion $p_{\rm T}$ are also measured and compared to several phenomenological predictions. } |