Evidence of the \Theta^+ in the \gamma d \to K^+K^-pn reaction
T. Nakano, N. Muramatsu, D.S. Ahn, J.K. Ahn, H. Akimune, Y. Asano,, W.C. Chang, S. Dat\'e,, H. Ejiri, H. Fujimura, M. Fujiwara, S. Fukui, H., Hasegawa, K. Hicks, K. Horie, T. Hotta, K. Imai, T. Ishikawa, T. Iwata, Y., Kato, H. Kawai, Z.Y. Kim, K. Kino, H. Kohri, N. Kumagai
TL;DR
This study provides experimental evidence for the ^+ pentaquark state in the d reaction, observing a narrow peak with high statistical significance, supporting its existence in the specified energy range.
Contribution
First experimental observation of the ^+ pentaquark in the d reaction with a statistically significant peak at 1.524 GeV/c^2.
Findings
Narrow peak at 1.524 GeV/c^2 in nK^+ invariant mass
Peak significance of 5.1
Estimated differential cross-section of 12 b1 2 nb/sr
Abstract
The \gamma d \to K^+K^-pn reaction has been studied to search for the evidence of the \Theta^+ by detecting K^+K^- pairs at forward angles. The Fermi-motion corrected nK^+ invariant mass distribution shows a narrow peak at 1.524 +- 0.002 + 0.003 GeV/c^2. The statistical significance of the peak calculated from a shape analysis is 5.1 \sigma, and the differential cross-section for the \gamma n \to K^- \Theta^+ reaction is estimated to be 12 +- 2 nb/sr in the photon energy range from 2.0 GeV to 2.4 GeV in the LEPS angular range by assuming the isotropic production of the \Theta^+ in the \gamma n center-of-mass system. The obtained results support the existence of the \Theta^+.
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Taxonomy
TopicsQuantum Chromodynamics and Particle Interactions · Particle physics theoretical and experimental studies