Search for the $X_b$ and other hidden-beauty states in the $\pi^+ \pi^- \Upsilon(1 \rm S)$ channel at ATLAS

TL;DR

This study searched for hidden-beauty states similar to the X(3872) in proton-proton collision data from ATLAS but found no evidence, setting the most restrictive upper limits to date on their production rates.

Contribution

First search for $X_b$ and other hidden-beauty states in the specified mass ranges using ATLAS data, establishing new upper limits on their production.

Findings

No evidence for new narrow states was observed.

Upper limits on production cross section times branching fraction range from 0.8% to 4.0%.

Most restrictive upper limits for masses above 10.1 GeV to date.

Abstract

This Letter presents a search for a hidden-beauty counterpart of the $X(3872)$ in the mass ranges 10.05--10.31 GeV and 10.40--11.00 GeV, in the channel $X_b \to \pi^{+} \pi^{-} \Upsilon(1 \rm S)(\rightarrow\mu^+\mu^-)$, using 16.2 fb$^{-1}$ of $\sqrt{s}=8$ TeV $pp$ collision data collected by the ATLAS detector at the LHC. No evidence for new narrow states is found, and upper limits are set on the product of the $X_b$ cross section and branching fraction, relative to those of the $\Upsilon(2 \rm S)$, at the 95% confidence level using the CL$_S$ approach. These limits range from 0.8% to 4.0%, depending on mass. For masses above 10.1 GeV, the expected upper limits from this analysis are the most restrictive to date. Searches for production of the $\Upsilon(1^3 \rm{D}$$_J)$, $\Upsilon(10860)$, and $\Upsilon(11020)$ states also reveal no significant signals.