Observation of a threshold cusp at the Λη threshold in the pK- mass spectrum with Λc+ →pK-π+ decays

S. B. Yang; K. Tanida; J. K. Ahn; I. Adachi; H. Aihara; D. M. Asner; H. Atmacan; V. Aulchenko; T. Aushev; R. Ayad; V. Babu; P. Behera; K. Belous; J. Bennett; M. Bessner; V. Bhardwaj; B. Bhuyan; D. Bodrov; J. Borah; A. Bozek; M. Bračko; P. Branchini; T. E. Browder; A. Budano; M. Campajola; D. Červenkov; M. C. Chang; P. Chang; 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 Pietro; R. Dhamija; F. Di Capua; Z. DoleŽal; T. V. Dong; D. Dossett; D. Epifanov; B. G. Fulsom; R. Garg; V. Gaur; A. Garmash; A. Giri; P. Goldenzweig; E. Graziani; T. Gu; Y. Guan; K. Gudkova; C. Hadjivasiliou; K. Hayasaka; H. Hayashii; W. S. Hou; C. L. Hsu; T. Iijima; K. Inami; N. Ipsita; A. Ishikawa; R. Itoh; M. Iwasaki; Y. Iwasaki; W. W. Jacobs; E. J. Jang; Q. P. Ji; S. Jia; Y. Jin; K. K. Joo; K. H. Kang; G. Karyan; T. Kawasaki; H. Kichimi; C. Kiesling; C. H. Kim; D. Y. Kim; K. H. Kim; Y. J. Kim; Y. K. Kim; H. Kindo; P. Kodyš; T. Konno; A. Korobov; S. Korpar; E. Kovalenko; P. KriŽan; P. Krokovny; M. Kumar; R. Kumar; K. Kumara; Y. J. Kwon; T. Lam; J. S. Lange; M. Laurenza; J. Y. Lee; S. C. Lee; C. H. Li; J. Li; L. K. Li; Y. Li; L. Li Gioi; J. Libby; K. Lieret; D. Liventsev; T. Luo; M. Masuda; T. Matsuda; D. Matvienko; S. K. Maurya; F. Meier; M. Merola; F. Metzner; K. Miyabayashi; R. Mizuk; G. B. Mohanty; I. Nakamura; T. Nakano; M. Nakao; Z. Natkaniec; A. Natochii; L. Nayak; M. Niiyama; N. K. Nisar; S. Nishida; H. Ono; P. Oskin; P. Pakhlov; G. Pakhlova; S. Pardi; H. Park; S. H. Park; A. Passeri; S. Patra; S. Paul; T. K. Pedlar; R. Pestotnik; L. E. Piilonen; T. Podobnik; E. Prencipe; M. T. Prim; N. Rout; G. Russo; S. Sandilya; L. Santelj; V. Savinov; G. Schnell; J. Schueler; C. Schwanda; Y. Seino; K. Senyo; M. E. Sevior; M. Shapkin; C. Sharma; C. P. Shen; J. G. Shiu; J. B. Singh; A. Sokolov; E. Solovieva; M. Starič; M. Sumihama; T. Sumiyoshi; W. Sutcliffe; M. Takizawa; U. Tamponi; F. Tenchini; K. Trabelsi; T. Tsuboyama; M. Uchida; T. Uglov; Y. Unno; S. Uno; Y. Ushiroda; Y. Usov; R. Van Tonder; G. Varner; A. Vossen; E. Waheed; E. Wang; M. Z. Wang; X. L. Wang; M. Watanabe; S. Watanuki; O. Werbycka; E. Won; B. D. Yabsley; W. Yan; J. Yelton; J. H. Yin; C. Z. Yuan; Y. Yusa; Y. Zhai; Z. P. Zhang; V. Zhilich; V. Zhukova

doi:10.1103/PhysRevD.108.L031104

Observation of a threshold cusp at the Λη threshold in the pK- mass spectrum with Λc+ →pK-π+ decays

S. B. Yang, K. Tanida, J. K. Ahn, I. Adachi, H. Aihara, D. M. Asner, H. Atmacan, V. Aulchenko, T. Aushev, R. Ayad, V. Babu, P. Behera, K. Belous, J. Bennett, M. Bessner, V. Bhardwaj, B. Bhuyan, D. Bodrov, J. Borah, A. BozekM. Bračko, P. Branchini, T. E. Browder, A. Budano, M. Campajola, D. Červenkov, M. C. Chang, P. Chang, 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 Pietro, R. Dhamija, F. Di Capua, Z. DoleŽal, T. V. Dong, D. Dossett, D. Epifanov, B. G. Fulsom, R. Garg, V. Gaur, A. Garmash, A. Giri, P. Goldenzweig, E. Graziani, T. Gu, Y. Guan, K. Gudkova, C. Hadjivasiliou, K. Hayasaka, H. Hayashii, W. S. Hou, C. L. Hsu, T. Iijima, K. Inami, N. Ipsita, A. Ishikawa, R. Itoh, M. Iwasaki, Y. Iwasaki, W. W. Jacobs, E. J. Jang, Q. P. Ji, S. Jia, Y. Jin, K. K. Joo, K. H. Kang, G. Karyan, T. Kawasaki, H. Kichimi, C. Kiesling, C. H. Kim, D. Y. Kim, K. H. Kim, Y. J. Kim, Y. K. Kim, H. Kindo, P. Kodyš, T. Konno, A. Korobov, S. Korpar, E. Kovalenko, P. KriŽan, P. Krokovny, M. Kumar, R. Kumar, K. Kumara, Y. J. Kwon, T. Lam, J. S. Lange, M. Laurenza, J. Y. Lee, S. C. Lee, C. H. Li, J. Li, L. K. Li, Y. Li, L. Li Gioi, J. Libby, K. Lieret, D. Liventsev, T. Luo, M. Masuda, T. Matsuda, D. Matvienko, S. K. Maurya, F. Meier, M. Merola, F. Metzner, K. Miyabayashi, R. Mizuk, G. B. Mohanty, I. Nakamura, T. Nakano, M. Nakao, Z. Natkaniec, A. Natochii, L. Nayak, M. Niiyama, N. K. Nisar, S. Nishida, H. Ono, P. Oskin, P. Pakhlov, G. Pakhlova, S. Pardi, H. Park, S. H. Park, A. Passeri, S. Patra, S. Paul, T. K. Pedlar, R. Pestotnik, L. E. Piilonen, T. Podobnik, E. Prencipe, M. T. Prim, N. Rout, G. Russo, S. Sandilya, L. Santelj, V. Savinov, G. Schnell, J. Schueler, C. Schwanda, Y. Seino, K. Senyo, M. E. Sevior, M. Shapkin, C. Sharma, C. P. Shen, J. G. Shiu, J. B. Singh, A. Sokolov, E. Solovieva, M. Starič, M. Sumihama, T. Sumiyoshi, W. Sutcliffe, M. Takizawa, U. Tamponi, F. Tenchini, K. Trabelsi, T. Tsuboyama, M. Uchida, T. Uglov, Y. Unno, S. Uno, Y. Ushiroda, Y. Usov, R. Van Tonder, G. Varner, A. Vossen, E. Waheed, E. Wang, M. Z. Wang, X. L. Wang, M. Watanabe, S. Watanuki, O. Werbycka, E. Won, B. D. Yabsley, W. Yan, J. Yelton, J. H. Yin, C. Z. Yuan, Y. Yusa, Y. Zhai, Z. P. Zhang, V. Zhilich, V. Zhukova

Research output: Contribution to journal › Article › peer-review

2 Scopus citations

Abstract

We observe a narrow peaking structure in the pK- invariant-mass spectrum near the Λη threshold. The peak is clearly seen in 1.5 million events of Λc+→pK-π+ decay using the 980 fb-1 data sample collected by the Belle detector at the KEKB asymmetric-energy e+e- collider. We try two approaches to explain this structure: as a new resonance and as a cusp at the Λη threshold. The best fit is obtained with a coherent sum of a Flatté function and a constant background amplitude with the reduced χ2 of 257/243 (p=0.25), while the fits to Breit-Wigner functions are unfavored by more than 7σ. The best fit explains the structure as a cusp at the Λη threshold, and the obtained parameters are consistent with the known properties of Λ(1670). The observation gives the first identification of a threshold cusp in hadrons from the spectrum shape.

Original language	English
Article number	L031104
Journal	Physical Review D
Volume	108
Issue number	3
DOIs	https://doi.org/10.1103/PhysRevD.108.L031104
State	Published - 1 Aug 2023

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10.1103/PhysRevD.108.L031104

Cite this

Yang, S. B., Tanida, K., Ahn, J. K., Adachi, I., Aihara, H., Asner, D. M., Atmacan, H., Aulchenko, V., Aushev, T., Ayad, R., Babu, V., Behera, P., Belous, K., Bennett, J., Bessner, M., Bhardwaj, V., Bhuyan, B., Bodrov, D., Borah, J., ... Zhukova, V. (2023). Observation of a threshold cusp at the Λη threshold in the pK- mass spectrum with Λc+ →pK-π+ decays. Physical Review D, 108(3), Article L031104. https://doi.org/10.1103/PhysRevD.108.L031104

@article{b139892f576c4027926ea3e06c05ef04,

title = "Observation of a threshold cusp at the Λη threshold in the pK- mass spectrum with Λc+ →pK-π+ decays",

abstract = "We observe a narrow peaking structure in the pK- invariant-mass spectrum near the Λη threshold. The peak is clearly seen in 1.5 million events of Λc+→pK-π+ decay using the 980 fb-1 data sample collected by the Belle detector at the KEKB asymmetric-energy e+e- collider. We try two approaches to explain this structure: as a new resonance and as a cusp at the Λη threshold. The best fit is obtained with a coherent sum of a Flatt{\'e} function and a constant background amplitude with the reduced χ2 of 257/243 (p=0.25), while the fits to Breit-Wigner functions are unfavored by more than 7σ. The best fit explains the structure as a cusp at the Λη threshold, and the obtained parameters are consistent with the known properties of Λ(1670). The observation gives the first identification of a threshold cusp in hadrons from the spectrum shape.",

author = "Yang, {S. B.} and K. Tanida and Ahn, {J. K.} and I. Adachi and H. Aihara and Asner, {D. M.} and H. Atmacan and V. Aulchenko and T. Aushev and R. Ayad and V. Babu and P. Behera and K. Belous and J. Bennett and M. Bessner and V. Bhardwaj and B. Bhuyan and D. Bodrov and J. Borah and A. Bozek and M. Bra{\v c}ko and P. Branchini and Browder, {T. E.} and A. Budano and M. Campajola and D. {\v C}ervenkov and Chang, {M. C.} and P. Chang and Cheon, {B. G.} and K. Chilikin and Cho, {H. E.} and K. Cho and Cho, {S. J.} and Choi, {S. K.} and Y. Choi and S. Choudhury and D. Cinabro and S. Das and {De Pietro}, G. and R. Dhamija and {Di Capua}, F. and Z. Dole{\v Z}al and Dong, {T. V.} and D. Dossett and D. Epifanov and Fulsom, {B. G.} and R. Garg and V. Gaur and A. Garmash and A. Giri and P. Goldenzweig and E. Graziani and T. Gu and Y. Guan and K. Gudkova and C. Hadjivasiliou and K. Hayasaka and H. Hayashii and Hou, {W. S.} and Hsu, {C. L.} and T. Iijima and K. Inami and N. Ipsita and A. Ishikawa and R. Itoh and M. Iwasaki and Y. Iwasaki and Jacobs, {W. W.} and Jang, {E. J.} and Ji, {Q. P.} and S. Jia and Y. Jin and Joo, {K. K.} and Kang, {K. H.} and G. Karyan and T. Kawasaki and H. Kichimi and C. Kiesling and Kim, {C. H.} and Kim, {D. Y.} and Kim, {K. H.} and Kim, {Y. J.} and Kim, {Y. K.} and H. Kindo and P. Kody{\v s} and T. Konno and A. Korobov and S. Korpar and E. Kovalenko and P. Kri{\v Z}an and P. Krokovny and M. Kumar and R. Kumar and K. Kumara and Kwon, {Y. J.} and T. Lam and Lange, {J. S.} and M. Laurenza and Lee, {J. Y.} and Lee, {S. C.} and Li, {C. H.} and J. Li and Li, {L. K.} and Y. Li and {Li Gioi}, L. and J. Libby and K. Lieret and D. Liventsev and T. Luo and M. Masuda and T. Matsuda and D. Matvienko and Maurya, {S. K.} and F. Meier and M. Merola and F. Metzner and K. Miyabayashi and R. Mizuk and Mohanty, {G. B.} and I. Nakamura and T. Nakano and M. Nakao and Z. Natkaniec and A. Natochii and L. Nayak and M. Niiyama and Nisar, {N. K.} and S. Nishida and H. Ono and P. Oskin and P. Pakhlov and G. Pakhlova and S. Pardi and H. Park and Park, {S. H.} and A. Passeri and S. Patra and S. Paul and Pedlar, {T. K.} and R. Pestotnik and Piilonen, {L. E.} and T. Podobnik and E. Prencipe and Prim, {M. T.} and N. Rout and G. Russo and S. Sandilya and L. Santelj and V. Savinov and G. Schnell and J. Schueler and C. Schwanda and Y. Seino and K. Senyo and Sevior, {M. E.} and M. Shapkin and C. Sharma and Shen, {C. P.} and Shiu, {J. G.} and Singh, {J. B.} and A. Sokolov and E. Solovieva and M. Stari{\v c} and M. Sumihama and T. Sumiyoshi and W. Sutcliffe and M. Takizawa and U. Tamponi and F. Tenchini and K. Trabelsi and T. Tsuboyama and M. Uchida and T. Uglov and Y. Unno and S. Uno and Y. Ushiroda and Y. Usov and {Van Tonder}, R. and G. Varner and A. Vossen and E. Waheed and E. Wang and Wang, {M. Z.} and Wang, {X. L.} and M. Watanabe and S. Watanuki and O. Werbycka and E. Won and Yabsley, {B. D.} and W. Yan and J. Yelton and Yin, {J. H.} and Yuan, {C. Z.} and Y. Yusa and Y. Zhai and Zhang, {Z. P.} and V. Zhilich and V. Zhukova",

note = "Publisher Copyright: {\textcopyright} 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the {"}https://creativecommons.org/licenses/by/4.0/{"}Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.",

year = "2023",

month = aug,

day = "1",

doi = "10.1103/PhysRevD.108.L031104",

language = "English",

volume = "108",

journal = "Physical Review D",

issn = "2470-0010",

publisher = "American Physical Society",

number = "3",

}

Yang, SB, Tanida, K, Ahn, JK, Adachi, I, Aihara, H, Asner, DM, Atmacan, H, Aulchenko, V, Aushev, T, Ayad, R, Babu, V, Behera, P, Belous, K, Bennett, J, Bessner, M, Bhardwaj, V, Bhuyan, B, Bodrov, D, Borah, J, Bozek, A, Bračko, M, Branchini, P, Browder, TE, Budano, A, Campajola, M, Červenkov, D, Chang, MC, Chang, P, Cheon, BG, Chilikin, K, Cho, HE, Cho, K, Cho, SJ, Choi, SK, Choi, Y, Choudhury, S, Cinabro, D, Das, S, De Pietro, G, Dhamija, R, Di Capua, F, DoleŽal, Z, Dong, TV, Dossett, D, Epifanov, D, Fulsom, BG, Garg, R, Gaur, V, Garmash, A, Giri, A, Goldenzweig, P, Graziani, E, Gu, T, Guan, Y, Gudkova, K, Hadjivasiliou, C, Hayasaka, K, Hayashii, H, Hou, WS, Hsu, CL, Iijima, T, Inami, K, Ipsita, N, Ishikawa, A, Itoh, R, Iwasaki, M, Iwasaki, Y, Jacobs, WW, Jang, EJ, Ji, QP, Jia, S, Jin, Y, Joo, KK, Kang, KH, Karyan, G, Kawasaki, T, Kichimi, H, Kiesling, C, Kim, CH, Kim, DY, Kim, KH, Kim, YJ, Kim, YK, Kindo, H, Kodyš, P, Konno, T, Korobov, A, Korpar, S, Kovalenko, E, KriŽan, P, Krokovny, P, Kumar, M, Kumar, R, Kumara, K, Kwon, YJ, Lam, T, Lange, JS, Laurenza, M, Lee, JY, Lee, SC, Li, CH, Li, J, Li, LK, Li, Y, Li Gioi, L, Libby, J, Lieret, K, Liventsev, D, Luo, T, Masuda, M, Matsuda, T, Matvienko, D, Maurya, SK, Meier, F, Merola, M, Metzner, F, Miyabayashi, K, Mizuk, R, Mohanty, GB, Nakamura, I, Nakano, T, Nakao, M, Natkaniec, Z, Natochii, A, Nayak, L, Niiyama, M, Nisar, NK, Nishida, S, Ono, H, Oskin, P, Pakhlov, P, Pakhlova, G, Pardi, S, Park, H, Park, SH, Passeri, A, Patra, S, Paul, S, Pedlar, TK, Pestotnik, R, Piilonen, LE, Podobnik, T, Prencipe, E, Prim, MT, Rout, N, Russo, G, Sandilya, S, Santelj, L, Savinov, V, Schnell, G, Schueler, J, Schwanda, C, Seino, Y, Senyo, K, Sevior, ME, Shapkin, M, Sharma, C, Shen, CP, Shiu, JG, Singh, JB, Sokolov, A, Solovieva, E, Starič, M, Sumihama, M, Sumiyoshi, T, Sutcliffe, W, Takizawa, M, Tamponi, U, Tenchini, F, Trabelsi, K, Tsuboyama, T, Uchida, M, Uglov, T, Unno, Y, Uno, S, Ushiroda, Y, Usov, Y, Van Tonder, R, Varner, G, Vossen, A, Waheed, E, Wang, E, Wang, MZ, Wang, XL, Watanabe, M, Watanuki, S, Werbycka, O, Won, E, Yabsley, BD, Yan, W, Yelton, J, Yin, JH, Yuan, CZ, Yusa, Y, Zhai, Y, Zhang, ZP, Zhilich, V & Zhukova, V 2023, 'Observation of a threshold cusp at the Λη threshold in the pK- mass spectrum with Λc+ →pK-π+ decays', Physical Review D, vol. 108, no. 3, L031104. https://doi.org/10.1103/PhysRevD.108.L031104

TY - JOUR

T1 - Observation of a threshold cusp at the Λη threshold in the pK- mass spectrum with Λc+ →pK-π+ decays

AU - Yang, S. B.

AU - Tanida, K.

AU - Ahn, J. K.

AU - Adachi, I.

AU - Aihara, H.

AU - Asner, D. M.

AU - Atmacan, H.

AU - Aulchenko, V.

AU - Aushev, T.

AU - Ayad, R.

AU - Babu, V.

AU - Behera, P.

AU - Belous, K.

AU - Bennett, J.

AU - Bessner, M.

AU - Bhardwaj, V.

AU - Bhuyan, B.

AU - Bodrov, D.

AU - Borah, J.

AU - Bozek, A.

AU - Bračko, M.

AU - Branchini, P.

AU - Browder, T. E.

AU - Budano, A.

AU - Campajola, M.

AU - Červenkov, D.

AU - Chang, M. C.

AU - Chang, P.

AU - Cheon, B. G.

AU - Chilikin, K.

AU - Cho, H. E.

AU - Cho, K.

AU - Cho, S. J.

AU - Choi, S. K.

AU - Choi, Y.

AU - Choudhury, S.

AU - Cinabro, D.

AU - Das, S.

AU - De Pietro, G.

AU - Dhamija, R.

AU - Di Capua, F.

AU - DoleŽal, Z.

AU - Dong, T. V.

AU - Dossett, D.

AU - Epifanov, D.

AU - Fulsom, B. G.

AU - Garg, R.

AU - Gaur, V.

AU - Garmash, A.

AU - Giri, A.

AU - Goldenzweig, P.

AU - Graziani, E.

AU - Gu, T.

AU - Guan, Y.

AU - Gudkova, K.

AU - Hadjivasiliou, C.

AU - Hayasaka, K.

AU - Hayashii, H.

AU - Hou, W. S.

AU - Hsu, C. L.

AU - Iijima, T.

AU - Inami, K.

AU - Ipsita, N.

AU - Ishikawa, A.

AU - Itoh, R.

AU - Iwasaki, M.

AU - Iwasaki, Y.

AU - Jacobs, W. W.

AU - Jang, E. J.

AU - Ji, Q. P.

AU - Jia, S.

AU - Jin, Y.

AU - Joo, K. K.

AU - Kang, K. H.

AU - Karyan, G.

AU - Kawasaki, T.

AU - Kichimi, H.

AU - Kiesling, C.

AU - Kim, C. H.

AU - Kim, D. Y.

AU - Kim, K. H.

AU - Kim, Y. J.

AU - Kim, Y. K.

AU - Kindo, H.

AU - Kodyš, P.

AU - Konno, T.

AU - Korobov, A.

AU - Korpar, S.

AU - Kovalenko, E.

AU - KriŽan, P.

AU - Krokovny, P.

AU - Kumar, M.

AU - Kumar, R.

AU - Kumara, K.

AU - Kwon, Y. J.

AU - Lam, T.

AU - Lange, J. S.

AU - Laurenza, M.

AU - Lee, J. Y.

AU - Lee, S. C.

AU - Li, C. H.

AU - Li, J.

AU - Li, L. K.

AU - Li, Y.

AU - Li Gioi, L.

AU - Libby, J.

AU - Lieret, K.

AU - Liventsev, D.

AU - Luo, T.

AU - Masuda, M.

AU - Matsuda, T.

AU - Matvienko, D.

AU - Maurya, S. K.

AU - Meier, F.

AU - Merola, M.

AU - Metzner, F.

AU - Miyabayashi, K.

AU - Mizuk, R.

AU - Mohanty, G. B.

AU - Nakamura, I.

AU - Nakano, T.

AU - Nakao, M.

AU - Natkaniec, Z.

AU - Natochii, A.

AU - Nayak, L.

AU - Niiyama, M.

AU - Nisar, N. K.

AU - Nishida, S.

AU - Ono, H.

AU - Oskin, P.

AU - Pakhlov, P.

AU - Pakhlova, G.

AU - Pardi, S.

AU - Park, H.

AU - Park, S. H.

AU - Passeri, A.

AU - Patra, S.

AU - Paul, S.

AU - Pedlar, T. K.

AU - Pestotnik, R.

AU - Piilonen, L. E.

AU - Podobnik, T.

AU - Prencipe, E.

AU - Prim, M. T.

AU - Rout, N.

AU - Russo, G.

AU - Sandilya, S.

AU - Santelj, L.

AU - Savinov, V.

AU - Schnell, G.

AU - Schueler, J.

AU - Schwanda, C.

AU - Seino, Y.

AU - Senyo, K.

AU - Sevior, M. E.

AU - Shapkin, M.

AU - Sharma, C.

AU - Shen, C. P.

AU - Shiu, J. G.

AU - Singh, J. B.

AU - Sokolov, A.

AU - Solovieva, E.

AU - Starič, M.

AU - Sumihama, M.

AU - Sumiyoshi, T.

AU - Sutcliffe, W.

AU - Takizawa, M.

AU - Tamponi, U.

AU - Tenchini, F.

AU - Trabelsi, K.

AU - Tsuboyama, T.

AU - Uchida, M.

AU - Uglov, T.

AU - Unno, Y.

AU - Uno, S.

AU - Ushiroda, Y.

AU - Usov, Y.

AU - Van Tonder, R.

AU - Varner, G.

AU - Vossen, A.

AU - Waheed, E.

AU - Wang, E.

AU - Wang, M. Z.

AU - Wang, X. L.

AU - Watanabe, M.

AU - Watanuki, S.

AU - Werbycka, O.

AU - Won, E.

AU - Yabsley, B. D.

AU - Yan, W.

AU - Yelton, J.

AU - Yin, J. H.

AU - Yuan, C. Z.

AU - Yusa, Y.

AU - Zhai, Y.

AU - Zhang, Z. P.

AU - Zhilich, V.

AU - Zhukova, V.

N1 - Publisher Copyright: © 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.

PY - 2023/8/1

Y1 - 2023/8/1

N2 - We observe a narrow peaking structure in the pK- invariant-mass spectrum near the Λη threshold. The peak is clearly seen in 1.5 million events of Λc+→pK-π+ decay using the 980 fb-1 data sample collected by the Belle detector at the KEKB asymmetric-energy e+e- collider. We try two approaches to explain this structure: as a new resonance and as a cusp at the Λη threshold. The best fit is obtained with a coherent sum of a Flatté function and a constant background amplitude with the reduced χ2 of 257/243 (p=0.25), while the fits to Breit-Wigner functions are unfavored by more than 7σ. The best fit explains the structure as a cusp at the Λη threshold, and the obtained parameters are consistent with the known properties of Λ(1670). The observation gives the first identification of a threshold cusp in hadrons from the spectrum shape.

AB - We observe a narrow peaking structure in the pK- invariant-mass spectrum near the Λη threshold. The peak is clearly seen in 1.5 million events of Λc+→pK-π+ decay using the 980 fb-1 data sample collected by the Belle detector at the KEKB asymmetric-energy e+e- collider. We try two approaches to explain this structure: as a new resonance and as a cusp at the Λη threshold. The best fit is obtained with a coherent sum of a Flatté function and a constant background amplitude with the reduced χ2 of 257/243 (p=0.25), while the fits to Breit-Wigner functions are unfavored by more than 7σ. The best fit explains the structure as a cusp at the Λη threshold, and the obtained parameters are consistent with the known properties of Λ(1670). The observation gives the first identification of a threshold cusp in hadrons from the spectrum shape.

UR - http://www.scopus.com/inward/record.url?scp=85168828517&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.108.L031104

DO - 10.1103/PhysRevD.108.L031104

M3 - Article

AN - SCOPUS:85168828517

SN - 2470-0010

VL - 108

JO - Physical Review D

JF - Physical Review D

IS - 3

M1 - L031104

ER -

Observation of a threshold cusp at the Λη threshold in the pK- mass spectrum with Λc+ →pK-π+ decays

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