Study of the B_c^+ → J/ψ D_s^+ and B_c^+ → J/ψ D_s^{*+} decays with the ATLAS detector
Abstract
The decays B_c^+ → J/ψ D_s^+ and B_c^+ → J/ψ D_s^{*+} are studied with the ATLAS detector at the LHC using a dataset corresponding to integrated luminosities of 4.9 and 20.6 fb^{-1} of pp collisions collected at centre-of-mass energies √{s} = 7 TeV and 8 TeV, respectively. Signal candidates are identified through J/ψ → μ ^+μ ^- and D_s^{(*)+}→ φ π ^+(γ /π ^0) decays. With a two-dimensional likelihood fit involving the B_c^+ reconstructed invariant mass and an angle between the μ ^+ and D_s^+ candidate momenta in the muon pair rest frame, the yields of B_c^+ → J/ψ D_s^+ and B_c^+ → J/ψ D_s^{*+}, and the transverse polarisation fraction in B_c^+ → J/ψ D_s^{*+} decay are measured. The transverse polarisation fraction is determined to be Γ _{± ± }(B_c^+ → J/ψ D_s^{*+})/Γ (B_c^+ → J/ψ D_s^{*+}) = 0.38 ± 0.23 ± 0.07, and the derived ratio of the branching fractions of the two modes is {B}_{B_c^+ → J/ψ D_s^{*+}}/{B}_{B_c^+ → J/ψ D_s^+} = 2.8 ^{+1.2}_{-0.8} ± 0.3, where the first error is statistical and the second is systematic. Finally, a sample of B_c^+→ J/ψ π ^+ decays is used to derive the ratios of branching fractions {B}_{B_c^+ → J/ψ D_s^+}/{B}_{B_c^+ → J/ψ π ^+} = 3.8 ± 1.1 ± 0.4 ± 0.2 and {B}_{B_c^+ → J/ψ D_s^{*+}}/{B}_{B_c^+ → J/ψ π ^+} = 10.4 ± 3.1 ± 1.5 ± 0.6, where the third error corresponds to the uncertainty of the branching fraction of D_s^+→ φ (K^+K^-)π ^+ decay. The available theoretical predictions are generally consistent with the measurement.
- Publication:
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European Physical Journal C
- Pub Date:
- January 2016
- DOI:
- 10.1140/epjc/s10052-015-3743-8
- Bibcode:
- 2016EPJC...76....4A