Observation of Diffractive $J/\psi$ Production at the Fermilab Tevatron

TL;DR

This paper reports the first observation of diffractive $J/$ production in proton-antiproton collisions at 1.8 TeV, measuring the diffractive to total production ratio and analyzing the gluon content of the diffractive structure function.

Contribution

It provides the first measurement of diffractive $J/$ production rates and determines the gluon fraction of the diffractive structure function of the proton.

Findings

Diffractive $J/$ production ratio is approximately 1.45%.

The gluon fraction of the diffractive structure function is about 0.59.

First observation of this diffractive process at the Tevatron.

Abstract

We report the first observation of diffractive $J/\psi(\to \mu^+\mu^-)$ production in $\bar pp$ collisions at $\sqrt{s}$=1.8 TeV. Diffractive events are identified by their rapidity gap signature. In a sample of events with two muons of transverse momentum $p_T^{\mu}>2$ GeV/$c$ within the pseudorapidity region $|\eta|<$1.0, the ratio of diffractive to total $J/\psi$ production rates is found to be $R_{J/\psi}= [1.45\pm 0.25]%$. The ratio $R_{J/\psi}(x)$ is presented as a function of $x$-Bjorken. By combining it with our previously measured corresponding ratio $R_{jj}(x)$ for diffractive dijet production, we extract a value of $0.59\pm 0.15$ for the gluon fraction of the diffractive structure function of the proton.