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We measure exclusive $\pi^+\pi^-$ production in proton-antiproton collisionsat center-of-mass energies $\sqrt{s}$ = 0.9 and 1.96 TeV in the ColliderDetector at Fermilab. We select events with two oppositely charged particles,assumed to be pions, with pseudorapidity $|\eta| < 1.3$ and with no otherparticles detected in $|\eta| < 5.9$. We require the $\pi^+\pi^-$ system tohave rapidity $|y|<$ 1.0. The production mechanism of these events is expectedto be dominated by double pomeron exchange, which constrains the quantumnumbers of the central state. The data are potentially valuable for isoscalarmeson spectroscopy and for understanding the pomeron in a region of transitionbetween nonperturbative and perturbative quantum chromodynamics. The dataextend up to dipion mass $M(\pi^+\pi^-)$ = 5000 MeV/$c^2$ and show resonancestructures attributed to $f_0$ and $f_2(1270)$ mesons. From the $\pi^+\pi^-$and $K^+K^-$ spectra, we place upper limits on exclusive $\chi_{c0}(3415)$production.

Measurement of central exclusive pi+pi- production in p-pbar collisions at sqrt(s) = 0.9 and 1.96 TeV at CDF