Sneha Malde

Abstract:

Quantum-correlated ψ(3770)→DD decays collected by the CLEO-c experiment are used to perform first measurements of F+, the fractional CP-even content of the self-conjugate decays D→π+π-π0 and D→K+K-π0. Values of 0.968±0.017±0.006 and 0.731±0.058±0.021 are obtained for π+π-π0 and K+K-π0, respectively. It is demonstrated how modes of this sort can be cleanly included in measurements of the unitarity triangle angle γ using B∓→DK∓ decays. The high CP-even content of D→π+π-π0, in particular, makes this a promising mode for improving the precision on γ.

Abstract:

Time-dependent CPviolation is measured in the B⁰→J/Ψπ⁺π^-channel for each π⁺π^-resonant final state using data collected with an integrated luminosity of 3.0fb^-1in ppcollisions using the LHCb detector. The final state with the largest rate, J/Ψρ⁰(770), is used to measure the CP-violating angle 2β^effto be (41.7 ±9.6^+2.8 -6.3)°. This result can be used to limit the size of penguin amplitude contributions to CPviolation measurements in, for example, B⁰ s→J/Ψϕdecays. Assuming approximate SU(3) flavour symmetry and neglecting higher order diagrams, the shift in the CP-violating phase ϕsis limited to be within the interval [-1.05°, +1.18°] at 95% confidence level. Changes to the limit due to SU(3) symmetry breaking effects are also discussed.

Abstract:

Abstract: The associated production of a Z boson or an off-shell photon γ^* with a bottom quark in the forward region is studied using proton-proton collisions at a centre-of-mass energy of 7 TeV. The Z bosons are reconstructed in the Z/γ^* → μ⁺μ⁻ final state from muons with a transverse momentum larger than 20 GeV, while two transverse momentum thresholds are considered for jets (10 GeV and 20 GeV). Both muons and jets are reconstructed in the pseudorapidity range 2.0 < η < 4.5. The results are based on data corresponding to 1.0 fb⁻¹ recorded in 2011 with the LHCb detector. The measurement of the Z+b-jet cross-section is normalized to the Z+jet cross-section. The measured cross-sections are(Formula presented.)for pT(jet) > 10 GeV, and(Formula presented.)for pT(jet) > 20 GeV.[Figure not available: see fulltext.].

Abstract:

Abstract: A search for the lepton flavour violating decay τ⁻ → μ⁻μ⁺μ⁻ is performed with the LHCb experiment. The data sample corresponds to an integrated luminosity of 1.0 fb⁻¹ of proton-proton collisions at a centre-of-mass energy of 7 TeV and 2.0 fb⁻¹ at 8 TeV. No evidence is found for a signal, and a limit is set at 90% confidence level on the branching fraction, B(τ⁻ → μ⁻μ⁺μ⁻) < 4.6 × 10⁻⁸

Abstract:

© 2015 The Authors. A search for the rare decays B⁰s → π⁺π^-μ⁺μ^- and B⁰ → π⁺π^-μ⁺μ^- is performed in a data set corresponding to an integrated luminosity of 3.0fb^-1collected by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7 and 8TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5-1.3GeV/c² and with muon pairs that do not originate from a resonance are considered. The first observation of the decay B⁰s → π⁺π^-μ⁺μ^-and the first evidence of the decay B⁰ → π⁺π^-μ⁺μ^-are obtained and the branching fractions, restricted to the dipion-mass range considered, are measured to be B(B⁰s → π⁺pπμ⁺μ^-) =(8.6 ±1.5(stat) ±0.7(syst) ±0.7 (norm)) ×10^-8 and B(B⁰ → π⁺π^-μ⁺μ^-) =(2.11±0.51(stat)±0.15(syst)±0.16(norm)) × 10^-8, where the third uncertainty is due to the branching fraction of the decay B⁰ → J/ψ(→ μ⁺μ^-)K*(892)⁰(→ K⁺p^-), used as a normalisation.