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arXiv · 2211.11151

First Observation of $\Lambda\pi^+$ and $\Lambda\pi^-$ Signals near the $\bar{K}N (I=1)$ Mass Threshold in $\Lambda_c^+\rightarrow\Lambda\pi^+\pi^+\pi^-$ Decay

Belle Collaboration·Y. Ma·J. Yelton·K. Tanida·I. Adachi·J. K. Ahn·H. Aihara·S. Al Said·D. M. Asner·H. Atmacan·T. Aushev·R. Ayad·V. Babu·S. Bahinipati·Sw. Banerjee·P. Behera·K. Belous·J. Bennett·M. Bessner·B. Bhuyan·T. Bilka·D. Biswas·A. Bobrov·D. Bodrov·J. Borah·A. Bozek·M. Bračko·P. Branchini·T. E. Browder·A. Budano·M. Campajola·D. Červenkov·M. -C. Chang·A. Chen·B. G. Cheon·K. Chilikin·H. E. Cho·K. Cho·S. -J. Cho·S. -K. Choi·Y. Choi·S. Choudhury·D. Cinabro·S. Das·G. De Nardo·G. De Pietro·R. Dhamija·F. Di Capua·J. Dingfelder·Z. Doležal·T. V. Dong·D. Epifanov·T. Ferber·D. Ferlewicz·B. G. Fulsom·R. Garg·V. Gaur·A. Garmash·A. Giri·P. Goldenzweig·B. Golob·E. Graziani·K. Gudkova·C. Hadjivasiliou·S. Halder·K. Hayasaka·H. Hayashii·M. T. Hedges·W. -S. Hou·C. -L. Hsu·K. Inami·N. Ipsita·A. Ishikawa·R. Itoh·M. Iwasaki·W. W. Jacobs·E. -J. Jang·S. Jia·Y. Jin·A. B. Kaliyar·K. H. Kang·T. Kawasaki·C. Kiesling·C. H. Kim·D. Y. Kim·Y. -K. Kim·K. Kinoshita·P. Kodyš·A. Korobov·S. Korpar·E. Kovalenko·P. Križan·P. Krokovny·R. Kumar·K. Kumara·Y. -J. Kwon·T. Lam·J. S. Lange·S. C. Lee·P. Lewis
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Abstract

Using the data sample of 980 fb$^{-1}$ collected with the Belle detector operating at the KEKB asymmetric-energy $e^+e^-$ collider, we present the results of an investigation of the $\Lambda\pi^+$ and $\Lambda\pi^-$ invariant mass distributions looking for substructure in the decay $\Lambda_c^+\rightarrow\Lambda\pi^+\pi^+\pi^-$. We find a significant signal in each mass dis\ tribution. When interpreted as resonances, we find for the $\Lambda\pi^+$ ($\Lambda\pi^-$) combination a mass of $1434.3 \pm 0.6 (\mathrm{stat}) \pm 0.9(\mathrm{syst})$ MeV/$c^2$ [$1438.5 \pm 0.9 (\mathrm{stat}) \pm 2.5(\mathrm{syst})$ MeV/$c^2$], an intrinsic width of $11.5 \pm 2.8 (\mathrm{stat}) \pm 5.3(\mathrm{syst})$ MeV/$c^2$ [$33.0 \pm 7.5 (\mathrm{stat}) \pm 23.6(\mathrm{syst})$ MeV/$c^2$] with a significance of 7.5$\sigma$ (6.2$\sigma$). As these two signals are very close to the $\bar{K}N$ threshold, we also investigate the possibility of a $\bar{K}N$ cusp, and find that \ we cannot discriminate between these two interpretations due to the limited size of the data sample.

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Belle Collaboration, Y. Ma, J. Yelton, K. Tanida, I. Adachi, J. K. Ahn, H. Aihara, S. Al Said, D. M. Asner, H. Atmacan, T. Aushev, R. Ayad, V. Babu, S. Bahinipati, Sw. Banerjee, P. Behera, K. Belous, J. Bennett, M. Bessner, B. Bhuyan, T. Bilka, D. Biswas, A. Bobrov, D. Bodrov, J. Borah, A. Bozek, M. Bračko, P. Branchini, T. E. Browder, A. Budano, M. Campajola, D. Červenkov, M. -C. Chang, A. Chen, B. G. Cheon, K. Chilikin, H. E. Cho, K. Cho, S. -J. Cho, S. -K. Choi, Y. Choi, S. Choudhury, D. Cinabro, S. Das, G. De Nardo, G. De Pietro, R. Dhamija, F. Di Capua, J. Dingfelder, Z. Doležal, T. V. Dong, D. Epifanov, T. Ferber, D. Ferlewicz, B. G. Fulsom, R. Garg, V. Gaur, A. Garmash, A. Giri, P. Goldenzweig, B. Golob, E. Graziani, K. Gudkova, C. Hadjivasiliou, S. Halder, K. Hayasaka, H. Hayashii, M. T. Hedges, W. -S. Hou, C. -L. Hsu, K. Inami, N. Ipsita, A. Ishikawa, R. Itoh, M. Iwasaki, W. W. Jacobs, E. -J. Jang, S. Jia, Y. Jin, A. B. Kaliyar, K. H. Kang, T. Kawasaki, C. Kiesling, C. H. Kim, D. Y. Kim, Y. -K. Kim, K. Kinoshita, P. Kodyš, A. Korobov, S. Korpar, E. Kovalenko, P. Križan, P. Krokovny, R. Kumar, K. Kumara, Y. -J. Kwon, T. Lam, J. S. Lange, S. C. Lee, P. Lewis. 2022-11-21. First Observation of $\Lambda\pi^+$ and $\Lambda\pi^-$ Signals near the $\bar{K}N (I=1)$ Mass Threshold in $\Lambda_c^+\rightarrow\Lambda\pi^+\pi^+\pi^-$ Decay. https://doi.org/10.1103/physrevlett.130.151903

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