Journal Article

Study of the ψ2(3823) and χc1(3872) states in B+→ (J/ψπ+π−)K+ decays

Vorobyev, V., Chefdeville, M., Di Canto, A., Alexander, M., Jones, C. R., Durante, P., Gao, Y., Eschle, J., Brossa Gonzalo, A., Yang, Z., Cardinale, R., Meinert, N., Mead, J. V., Barlow, R. J., Schmelling, M., Vázquez Sierra, C., Cai, H., Bedeschi, F., Swientek, K., Yang, Y., Stefko, P., Millard, E., Pugatch, V., Ketel, T., Bobulska, D., Ferro-Luzzi, M., Lefèvre, R., Zhang, S., Solovev, A., Golubkov, D., Lampis, A., Dalseno, J., Jawahery, A., Lai, A., Schneider, O., Rama, M., Bozzi, C., Carniti, P., Tran, M. T., Fontana, M., Straticiuc, M., Cenci, R., Ene, A., Smith, E., Zhou, X., Gibson, V., Mulder, M., Ramos Pernas, M., Jiang, F., Hollitt, S. E., Bezshyiko, Ia, Ribatti, R., Bertella, C., Tuning, N., Cobbledick, J. L., Kvaratskheliya, T., Morris, A. B., Carboni, G., Downes, A. G., Zenaiev, O., Didenko, S., Calero Diaz, L., McNulty, R., Baldini, W., Ponce, S., Karacson, M., Nguyen-Mau, C., Bian, L., Pomery, G. J., Decamp, D., Hancock, T. H., Brea Rodriguez, A., Skidmore, N., Chulikov, V., Romanovskiy, V., Malecki, B., Cadeddu, S., Pappagallo, M., Kecke, M., Nanut, T., Marino, P., Materok, M., Merli, A., Bishop, F. C. R., Epple, E., Dey, B., Lu, Y., Wiedner

2020

Overview

A bstract The decays B + → J / ψπ + π − K + are studied using a data set corresponding to an integrated luminosity of 9 fb − 1 collected with the LHCb detector in proton-proton collisions between 2011 and 2018. Precise measurements of the ratios of branching fractions with the intermediate ψ 2 (3823), χ c1 (3872) and ψ(2S) states are reported. The values are B B + → ψ 2 3823 K + × B ψ 2 3823 → J / ψπ + π − B B + → χ c 1 3872 K + × B χ c 1 3872 → J / ψπ + π − = 3.56 ± 0.67 ± 0.11 × 10 − 2 , B B + → ψ 2 3823 K + × B ψ 2 3823 → J / ψπ + π − B B + → ψ 2 S K + × B ψ 2 S → J / ψπ + π − = 1.31 ± 0.25 ± 0.04 × 10 − 3 , B B + → χ c 1 3872 K + × B χ c 1 3872 → J / ψπ + π − B B + → ψ 2 S K + × B ψ 2 S → J / ψπ + π − = 3.69 ± 0.07 ± 0.06 × 10 − 2 , where the first uncertainty is statistical and the second is systematic. The decay of B + → ψ 2 (3823)K + with ψ 2 (3823) → J / ψπ + π − is observed for the first time with a significance of 5.1 standard deviations. The mass differences between the ψ 2 (3823), χ c1 (3872) and ψ(2S) states are measured to be m χ c 1 3872 − m ψ 2 3823 = 47.50 ± 0.53 ± 0.13 MeV / c 2 , m ψ 2 3823 − m ψ 2 2 S = 137.98 ± 0.53 ± 0.14 MeV / c 2 , m χ c 1 3872 − m ψ 2 2 S = 185.49 ± 0.06 ± 0.03 MeV / c 2 , resulting in the most precise determination of the χ c1 (3872) mass. The width of the ψ 2 (3823) state is found to be below 5.2 MeV at 90% confidence level. The Breit-Wigner width of the χ c1 (3872) state is measured to be Γ χ c 1 3872 BW = 0.96 − 0.18 + 0.19 ± 0.21 MeV which is inconsistent with zero by 5.5 standard deviations.

• Publisher: Springer Berlin Heidelberg,Springer Nature
• Subject: Atomic, Nuclear and Particle Physics / B physics / Branching fraction / Classical and Quantum Gravitation / Elementary Particles / Hadron-Hadron scattering (experiments) / Physics / Physics and Astronomy / Quantum Field Theories / Quantum Field Theory / Quantum Physics / Quarkonium / Regular Article - Experimental Physics / Relativity Theory / Spectroscopy / String Theory