Measurement of Central Exclusive Hadron Pair Production in CDF

M. Albrow1, J. Lewis1, M. Żurek2,3, D. Lontkovskyi4, I. Makarenko4, J.S. Wilson5
1Fermilab, 2University of Cologne, 3Research Center Juelich, 4University of Kyiv, 5University of Michigan

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.

Figures:

• Interaction / non-interaction samples' signals in different subdetectors of CDF detector.

• Interaction / non-interaction samples' signals for maximal em Et in central CDF detector.

• Single track acceptance as a function of transverse momentum and pseudorapidity

• Two-track 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 rest-frame production angle $$\cos θ$$ in various ranges of dipion mass

• Distribution of rest-frame production angle $$\cos θ$$ in various ranges of dipion mass, with comparison to pure $$S$$-wave MC

• Distribution of rest-frame production angle $$\cos θ$$ vs dipion mass

• Comparison of $$\cos θ$$ distribution to pure $$S$$-wave using Kolmogorov-Smirnov 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 Kolmogorov-Smirnov test with larger y-axis 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