Observation of the Λ b 0 → χ c 1 \[ {\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1} \] (3872) pK− decay

• Published in: The journal of high energy physics Vol. 2019; no. 9; pp. 1 - 20
• Main Authors: Andreotti, M, Baldini, W, Bediaga, I, Bel, L J, Bertholet, E, Betancourt, C, Billoir, P, Bocci, V, Borisyak, M, Buonaura, A, Butter, J S, Calladine, R, Chatzikonstantinidis, G, Chekalina, V, Colombo, T, Costa Sobral, C M, Craik, D C, Da Silva, C L, P d’Argent, Davis, A, De Serio, M, Demmer, M, Dovbnya, A, Dudek, M W, Dzhelyadin, R, Egede, U, Farry, S, Fazzini, D, Ferro-Luzzi, M, Fischer, K M, Gersabeck, M, Gioventù, A, Gorelov, I V, Guth, A, Gys, T, Hadavizadeh, T, Hecker, M, Heß, M, Inglessi, A, Jakobsen, S, Kirn, T, Kotriakhova, S, Kress, F, Lazzeroni, C, P-R, Li, Z Li, Loi, A, Luo, Y, Maccolini, S, Mackowiak, P, Maevskiy, A, Martinazzoli, L, Mathe, Z, McNab, A, Mogini, A, Monteil, S, Moron, J, Nanut, T, Nasteva, I, Nikitin, N, Ossowska, A, Otalora Goicochea, J M, Papanestis, A, Penso, G, Pereima, D, Polycarpo, E, Popov, D, Rademacker, J H, Ratnikov, F, Reiss, F, Ruf, T, Savrina, D, Schael, S, Schmidt, B, Sciubba, A, Shekhtman, L, Shupperd, J D, Skidmore, N, Skwarnicki, T, Stefko, P, Stracka, S, Stramaglia, M E, Sun, Y, Szumlak, T, Tekampe, T, Tournefier, E, Trisovic, A, Tuning, N, Ustyuzhanin, A, Valat, S, Van Hulse, C B, Velthuis, J J, Vollhardt, A, Xie, Y, A Xu, J Yu, Yushchenko, O, Zdybal, M, Zhang, W C, Zhelezov, A
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer Nature B.V 01-09-2019
• Subjects: Decay; High energy physics; Luminosity; Particle collisions; Protons
• ISSN: 1029-8479
• DOI: 10.1007/JHEP09(2019)028

Using proton-proton collision data, collected with the LHCb detector and corresponding to 1.0, 2.0 and 1.9 fb−1 of integrated luminosity at the centre-of-mass energies of 7, 8, and 13 TeV, respectively, the decay Λb0→χc1\[ {\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1} \](3872)pK− with χc1(3872) → J/ψ π+π− is observed for the first time. The significance of the observed signal is in excess of seven standard deviations. It is found that (58 ± 15)% of the decays proceed via the two-body intermediate state χc1(3872)Λ(1520). The branching fraction with respect to that of the Λb0\[ {\Lambda}_{\mathrm{b}}^0 \] → ψ(2S)pK− decay mode, where the ψ(2S) meson is reconstructed in the J/ψ π+π− final state, is measured to be:βΛb0→χc13872pK−βΛb0→ψ2SpK−×βχc13872→J/ψπ+π−βψ2S→J/ψπ+π−=5.4±1.1±0.2×10−2,\[ \frac{\beta \left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}(3872){\mathrm{pK}}^{-}\right)}{\beta \left({\Lambda}_{\mathrm{b}}^0\to \uppsi \left(2\mathrm{S}\right){\mathrm{pK}}^{-}\right)}\times \frac{\beta \left({\upchi}_{\mathrm{c}1}(3872)\to \mathrm{J}/\uppsi {\uppi}^{+}{\uppi}^{-}\right)}{\beta \left(\uppsi \left(2\mathrm{S}\right)\to \mathrm{J}/\uppsi {\uppi}^{+}{\uppi}^{-}\right)}=\left(5.4\pm 1.1\pm 0.2\right)\times {10}^{-2}, \]where the first uncertainty is statistical and the second is systematic.