Measurement of central exclusive $\pi^+ \pi^-$ production in $p\bar{p}$ collisions at $\sqrt{s} = 0.9$ and 1.96 TeV at CDF

We measure exclusive pi(+)pi(-) production in proton-antiproton collisions at center-of-mass energies root s = 0.9 and 1.96 TeV in the Collider Detector at Fermilab. We select events with two oppositely charged particles, assumed to be pions, with pseudorapidity vertical bar eta vertical bar < 1.3 and with no other particles detected in vertical bar eta vertical bar < 5.9. We require the pi(+)pi(-) system to have rapidity vertical bar y vertical bar < 1.0. The production mechanism of these events is expected to be dominated by double pomeron exchange, which constrains the quantum numbers of the central state. The data are potentially valuable for isoscalar meson spectroscopy and for understanding the pomeron in a region of transition between nonperturbative and perturbative quantum chromodynamics. The data extend up to dipion mass M(pi(+)pi(-)) = 5000 MeV/c(2) and show resonance structures 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.