Abstract: | We measure exclusive $pi^+pi^-$ production in proton-antiproton collisions
at center-of-mass energies $sqrt{s}$ = 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 $|eta| < 1.3$ and with no other
particles detected in $|eta| < 5.9$. We require the pipi system to have
rapidity $|y|<$ 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. |