Observation of a J / ψ Λ Resonance Consistent with a Strange Pentaquark Candidate in B − → J / ψ Λ p ¯ Decays

• Published in: Physical review letters Vol. 131; no. 3
• Main Authors: Aaij, R., Abdelmotteleb, A. S. W., Abellan Beteta, C., Abudinén, F., Ackernley, T., Adeva, B., Adinolfi, M., Adlarson, P., Afsharnia, H., Agapopoulou, C., Aidala, C. A., Ajaltouni, Z., Akar, S., Akiba, K., Albrecht, J., Alessio, F., Alexander, M., Alfonso Albero, A., Aliouche, Z., Alvarez Cartelle, P., Amalric, R., Amato, S., Amey, J. L., Amhis, Y., An, L., Anderlini, L., Andersson, M., Andreianov, A., Andreotti, M., Andreou, D., Ao, D., Archilli, F., Artamonov, A., Artuso, M., Aslanides, E., Atzeni, M., Audurier, B., Bachmann, S., Bachmayer, M., Back, J. J., Bailly-reyre, A., Baladron Rodriguez, P., Balagura, V., Baldini, W., Baptista de Souza Leite, J., Barbetti, M., Barlow, R. J., Barsuk, S., Barter, W., Bartolini, M., Baryshnikov, F., Basels, J. M., Bassi, G., Batsukh, B., Battig, A., Bay, A., Beck, A., Becker, M., Bedeschi, F., Bediaga, I. B., Beiter, A., Belavin, V., Belin, S., Bellee, V., Belous, K., Belov, I., Belyaev, I., Benane, G., Bencivenni, G., Ben-Haim, E., Berezhnoy, A., Bernet, R., Bernet Andres, S., Berninghoff, D., Bernstein, H. C., Bertella, C., Bertolin, A., Betancourt, C., Betti, F., Bezshyiko, Ia, Bhasin, S., Bhom, J., Bian, L., Bieker, M. S., Biesuz, N. V., Bifani, S., Billoir, P., Biolchini, A., Birch, M., Bishop, F. C. R., Bitadze, A., Bizzeti, A., Blago, M. P., Blake, T., Blanc, F., Blank, J. E., Blusk, S., Bobulska, D., Boelhauve, J. A., Boente Garcia, O.
• Format: Journal Article
• Language: English
• Published: American Physical Society 21-07-2023
• Subjects: High Energy Physics - Experiment; Physics; strangeness; statistical; TeV; parity, negative; spin; amplitude analysis; pentaquark; narrow resonance; LHC-B
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.131.031901

An amplitude analysis of B- → J/ψ Λ p ¯ decays is performed using 4400 signal candidates selected on a data sample of pp collisions recorded at center-of-mass energies of 7, 8, and 13 TeV with the LHCb detector, corresponding to an integrated luminosity of 9  fb-1 . A narrow resonance in the J/ψ Λ system, consistent with a pentaquark candidate with strangeness, is observed with high significance. The mass and the width of this new state are measured to be 4338.2±0.7±0.4  MeV and 7.0±1.2±1.3  MeV , where the first uncertainty is statistical and the second systematic. The spin is determined to be 1/2 and negative parity is preferred. Because of the small Q -value of the reaction, the most precise single measurement of the B- mass to date, 5279.44±0.05±0.07  MeV , is obtained.