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

Aaltonen, Timo Antero and others (CDF)
### 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 $\pi\pi$ 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.

Publication

In: *Phys. Rev. D (Rapid Communications)* 91