Study of the B⁺_c → J/ψ D⁺_s and B⁺_c→ J/ψ D^*+_s decays with the ATLAS detector

• Autores: Alconada Verzini, María Josefina; Alonso, Francisco; Arduh, Francisco Anuar; Dova, María Teresa; Monticelli, Fernando Gabriel; Wahlberg, Hernán Pablo; The ATLAS Collaboration
• Año de publicación: 2016
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Exactas; Física; Partículas Elementales; ATLAS detector; la̵rge hadron collider
• Institución: Universidad Nacional de La Plata

The decays B⁺_c→J/ψD⁺_s and B⁺_c→J/ψD^*+_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→ϕπ+(γ/π⁰) 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/ψD⁺_s and B⁺_c→J/ψD^*+_s, and the transverse polarisation fraction in B⁺_c→J/ψD^*+_s decay are measured. The transverse polarisation fraction is determined to be Γ±±(B⁺_c→J/ψD^*+_s)/Γ(B⁺_c→J/ψD^*+_s)=0.38±0.23±0.07, and the derived ratio of the branching fractions of the two modes is B_{B⁺c→J/ψD^*+s}/B_{B⁺c→J/ψD⁺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/ψπ+ decays is used to derive the ratios of branching fractions BB_{B⁺c→J/ψD^*+s}/B_{B⁺c→J/ψπ+}=3.8±1.1±0.4±0.2 and B_{B⁺c→J/ψD^*+s}/B_{B⁺c→J/ψπ+}=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.
Facultad de Ciencias Exactas