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

TL;DR

This study measures exclusive pion pair production in proton-antiproton collisions at two energies, revealing resonance structures and setting limits on certain charmonium states, aiding meson spectroscopy and QCD understanding.

Contribution

First measurement of exclusive $^+^-$ production at these energies, providing new data on resonance structures and pomeron exchange mechanisms.

Findings

Resonance structures consistent with $f_0$ and $f_2(1270)$ mesons.

Extended dipion mass spectrum up to 5000 MeV/$c^2$.

Upper limits on exclusive $_{c0}(3415)$ production.

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.