Abstract
This Letter presents a search for a hidden-beauty counterpart of the X(3872) in the mass ranges of 10.05–10.31 GeV and 10.40–11.00 GeV, in the channel Xb→π+π−ϒ(1S)(→μ+μ−), using 16.2 fb−1 of s=8 TeVpp 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 Xb cross section and branching fraction, relative to those of the ϒ(2S), at the 95% confidence level using the CLS 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 ϒ(13DJ), ϒ(10860), and ϒ(11020) states also reveal no significant signals.
Highlights
The X(3872) is the first and the best-studied of the new hidden-charm states seen in the last decade
A simultaneous fit to the analysis bins is performed in a range m ± 8σec, where σec(m) is the width of the narrow signal component in the endcap: the window varies from ±72 MeV at GeV to ±224 MeV at 10.9 GeV; near GeV, m − 8σec < m < 11.2 GeV is used
Assuming that J = 2 production dominates, or that the mass splitting is larger than the experimental resolution, the upper limit on R can be read from Fig. 4; combined with the measured Υ (13D2) → π +π −Υ (1S) branching fraction [19], this yields an upper limit on the relative cross section σ (pp → Υ (13D2))/σ (pp → Υ (2S)) ≤ 0.55
Summary
The X(3872) is the first and the best-studied of the new hidden-charm states seen in the last decade. The molecular model of Swanson [12,16] predicts an Xb mass of 10561 MeV, while tetraquark predictions vary: for example, Ref. The π +π −Υ (1S) channel provides the opportunity to measure the production of the Υ (13D J ) states These have not been observed at the Tevatron; their production cross sections in pp collisions are unknown, but an early colour-octet calculation [17] gives values comparable to that of the Υ (2S). Π +π −Υ (1S)(→ μ+μ−), finding no evidence for narrow states in the 10.06–10.31 GeV and 10.40–10.99 GeV mass ranges They set upper limits on the product of cross section and branching fraction at values between 0.9% and 5.4% of the Υ (2S) rate. ATLAS Collaboration / Physics Letters B 740 (2015) 199–217 presented in terms of the product of production cross section and π +π −Υ (1S) branching fraction, relative to that for the Υ (2S)
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