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Observation of the Z →ψ + - Decay in pp Collisions at s =13 TeV
Date Issued
04-10-2018
Author(s)
Sirunyan, A. M.
Tumasyan, A.
Adam, W.
Ambrogi, F.
Asilar, E.
Bergauer, T.
Brandstetter, J.
Brondolin, E.
Dragicevic, M.
Erö, J.
Escalante Del Valle, A.
Flechl, M.
Frühwirth, R.
Ghete, V. M.
Hrubec, J.
Jeitler, M.
Krammer, N.
Krätschmer, I.
Liko, D.
Madlener, T.
Mikulec, I.
Rad, N.
Rohringer, H.
Schieck, J.
Schöfbeck, R.
Spanring, M.
Spitzbart, D.
Taurok, A.
Waltenberger, W.
Wittmann, J.
Wulz, C. E.
Zarucki, M.
Chekhovsky, V.
Mossolov, V.
Suarez Gonzalez, J.
De Wolf, E. A.
Di Croce, D.
Janssen, X.
Lauwers, J.
Pieters, M.
Van De Klundert, M.
Van Haevermaet, H.
Van Mechelen, P.
Van Remortel, N.
Abu Zeid, S.
Blekman, F.
D'Hondt, J.
De Bruyn, I.
De Clercq, J.
Deroover, K.
Flouris, G.
Lontkovskyi, D.
Lowette, S.
Marchesini, I.
Moortgat, S.
Moreels, L.
Python, Q.
Skovpen, K.
Tavernier, S.
Van Doninck, W.
Van Mulders, P.
Van Parijs, I.
Beghin, D.
Bilin, B.
Brun, H.
Clerbaux, B.
De Lentdecker, G.
Delannoy, H.
Dorney, B.
Fasanella, G.
Favart, L.
Goldouzian, R.
Grebenyuk, A.
Kalsi, A. K.
Lenzi, T.
Luetic, J.
Postiau, N.
Starling, E.
Thomas, L.
Vander Velde, C.
Vanlaer, P.
Vannerom, D.
Wang, Q.
Cornelis, T.
Dobur, D.
Fagot, A.
Gul, M.
Khvastunov, I.
Poyraz, D.
Roskas, C.
Trocino, D.
Tytgat, M.
Verbeke, W.
Vermassen, B.
Vit, M.
Zaganidis, N.
Bakhshiansohi, H.
Bondu, O.
Brochet, S.
Bruno, G.
Abstract
This Letter presents the observation of the rare Z boson decay Z→ψ + -. Here, ψ represents contributions from direct J/ψ and ψ(2S)→J/ψX, + - is a pair of electrons or muons, and the J/ψ meson is detected via its decay to μ+μ-. The sample of proton-proton collision data, collected by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV, corresponds to an integrated luminosity of 35.9 fb-1. The signal is observed with a significance in excess of 5 standard deviations. After subtraction of the ψ(2S)→J/ψX contribution, the ratio of the branching fraction of the exclusive decay Z→J/ψ + - to the decay Z→μ+μ-μ+μ- within a fiducial phase space is measured to be B(Z→J/ψ + -)/B(Z→μ+μ-μ+μ-)=0.67±0.18(stat)±0.05(syst).
Volume
121