Abstract:
We present a study in CDF of \(p\bar{p}\) collisions at the Tevatron that have 2 charged hadrons in the central region, \(\eta < 1.3\) with large rapidity gaps (no hadrons) on either side. The reaction is \(p + \bar{p} \rightarrow p + X + \bar{p}\), where the "+" stands for a rapidity gap \(G\); we use the notation \(GXG\). Here we present a study of events with exactly two charged hadron tracks in the central detector, which we show to be often the result of the decay of a single neutral resonance, such as \(f_0^0\) or \(f_2^0\) states, or (rarely) the \(\chi_c\). These events are expected to be dominated by double pomeron, \(\pom\), exchange in the \(t\)channel; hence \(\pom + \pom\rightarrow X\). Only specific quantum numbers for \(X\) are allowed. Additionally, we see a signal for photoproduction of the \(J/ψ\) stats, which provides a check of our mass scale, resolution, and cross section calculation. We also place limits on exclusive production of \(\chi_c\) production and decay in the \(π^+π^\) and \(K^+K^\) channels.
We use data taken at \(\sqrt{s}\) = 1960 GeV and 900 GeV. This data provides a useful window on hadron spectroscopy, as well as providing benchmarks for testing pomeron models.
More information is available in CDF public note 11034.
Figures:

Interaction / noninteraction samples' signals in different subdetectors of CDF detector.

Interaction / noninteraction samples' signals for maximal em Et in central CDF detector.

Single track acceptance as a function of transverse momentum and pseudorapidity

Twotrack event acceptance as a function of dipion mass and transverse momentum

Probability for a track to leave a triggerable signal in 0 calorimeter towers

Probability for a track to leave a triggerable signal in 1 calorimeter tower

Probability for a track to leave a triggerable signal in 2 calorimeter towers

Exclusive efficiency for \(1960~\mathrm{GeV}\) data

Exclusive efficiency for 900GeV data.

Invariant mass not corrected for acceptance, for 1960GeV data.

Invariant mass not corrected for acceptance, for 900GeV data.

Inverse ratio of cross sections measured at 1960 GeV and 900 GeV.

Invariant Mass vs Pt distribution

Invariant mass corrected for acceptance in log scale, for 1960GeV data.

Comparison of invariant mass distributions at 1960GeV and 900GeV.

Comparison of invariant mass distributions at 1960GeV and 900GeV in the region of most significant peaks.

Top: Tail of invariant mass distribution with 4th order polynomial fit. Bottom: Residuals of the fit.

Invariant mass distributions at 1960GeV for Pt(X) > 1GeV/c.

Invariant mass distributions at 900GeV for Pt(X) > 1GeV/c.

Invariant mass distributions at 1960GeV with marked contributions from identified particles.

Mass of identified particles with ToF vs momentum.

Invariant mass corrected for acceptance for 1960GeV data for same charge and oposite charge sample.

Mean Pt distribution as a function of invariant mass for 1960GeV data.

Mean Pt distribution as a function of invariant mass for 900GeV data.

Pt distribution in different bands of invariant mass for 1960 GeV data.

Continuum exponential fit in high mass range  estimate of the background in search of chi_c or J/psi (with blind regions at their possible apperance).

Continuum exponential fit in J/psi and chi_c region.

Distribution of restframe production angle \(\cos θ\) in various ranges of dipion mass

Distribution of restframe production angle \(\cos θ\) in various ranges of dipion mass, with comparison to pure \(S\)wave MC

Distribution of restframe production angle \(\cos θ\) vs dipion mass

Comparison of \(\cos θ\) distribution to pure \(S\)wave using KolmogorovSmirnov test. Large \(p\)values indicate that we cannot reject the pure \(S\)wave hypothesis. Small \(p\)values indicate rejection of the pure \(S\)wave hypothesis with rejection strength given by the \(p\)value.

Comparison of \(\cos θ\) distribution to pure \(S\)wave using KolmogorovSmirnov test with larger yaxis range

Trajectory of 0th degree Legendre moment as a function of dipion mass

Trajectory of 1st degree Legendre moment as a function of dipion mass

Trajectory of 2nd degree Legendre moment as a function of dipion mass

Trajectory of 3rd degree Legendre moment as a function of dipion mass

Trajectory of 4th degree Legendre moment as a function of dipion mass

Trajectory of 5th degree Legendre moment as a function of dipion mass

Trajectory of 6th degree Legendre moment as a function of dipion mass

Trajectory of 7th degree Legendre moment as a function of dipion mass

Trajectory of 8th degree Legendre moment as a function of dipion mass