Search for narrow resonances below the Upsilon mesons

TL;DR

This study searches for narrow resonances below the Upsilon mesons using dimuon data from the Fermilab Tevatron, setting upper limits on their production relative to the Y(1S) meson, and noting an excess near 7.2 GeV/c^2.

Contribution

It provides new upper limits on narrow resonance production in the 6.3-9.0 GeV/c^2 range, improving previous constraints and identifying an excess at 7.2 GeV/c^2.

Findings

Upper limits on resonance production vary from 1.7% to 0.5%.

An excess of events at 7.2 GeV/c^2 suggests a possible resonance.

Limits are significantly worse at 7.2 GeV/c^2 due to excess events.

Abstract

We have investigated the invariant mass spectrum of dimuons collected by the CDF experiment during the 1992-1995 run of the Fermilab Tevatron collider to improve the limit on the existence of narrow resonances set by the experiments at the SPEAR e+e- collider. In the mass range 6.3-9.0 GeV/c^2, we derive 90% upper credible limits to the ratio of the production cross section times muonic branching fraction of possible narrow resonances to that of the Y(1S) meson. In this mass range, the average limit varies from 1.7 to 0.5%. This limit is much worse at the mass of 7.2 GeV/c^2 due to an excess of 250+-61 events with a width consistent with the detector resolution.