539 research outputs found

    Kinematical coincidence method in transfer reactions

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    A new method to extract high resolution angular distributions from kinematical coincidence measurements in binary reactions is presented. Kinematic is used to extract the center of mass angular distribution from the measured energy spectrum of light particles. Results obtained in the case of 10Be+p-->9Be+d reaction measured with the CHIMERA detector are shown. An angular resolution of few degrees in the center of mass is obtained.Comment: 6 Page 10 Figures submitted to Nuclear Instruments and Methods

    Observation of two new Ξb−\Xi_b^- baryon resonances

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    Two structures are observed close to the kinematic threshold in the Ξb0π−\Xi_b^0 \pi^- mass spectrum in a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb−1^{-1} recorded by the LHCb experiment. In the quark model, two baryonic resonances with quark content bdsbds are expected in this mass region: the spin-parity JP=12+J^P = \frac{1}{2}^+ and JP=32+J^P=\frac{3}{2}^+ states, denoted Ξbâ€Č−\Xi_b^{\prime -} and Ξb∗−\Xi_b^{*-}. Interpreting the structures as these resonances, we measure the mass differences and the width of the heavier state to be m(Ξbâ€Č−)−m(Ξb0)−m(π−)=3.653±0.018±0.006m(\Xi_b^{\prime -}) - m(\Xi_b^0) - m(\pi^{-}) = 3.653 \pm 0.018 \pm 0.006 MeV/c2/c^2, m(Ξb∗−)−m(Ξb0)−m(π−)=23.96±0.12±0.06m(\Xi_b^{*-}) - m(\Xi_b^0) - m(\pi^{-}) = 23.96 \pm 0.12 \pm 0.06 MeV/c2/c^2, Γ(Ξb∗−)=1.65±0.31±0.10\Gamma(\Xi_b^{*-}) = 1.65 \pm 0.31 \pm 0.10 MeV, where the first and second uncertainties are statistical and systematic, respectively. The width of the lighter state is consistent with zero, and we place an upper limit of Γ(Ξbâ€Č−)<0.08\Gamma(\Xi_b^{\prime -}) < 0.08 MeV at 95% confidence level. Relative production rates of these states are also reported.Comment: 17 pages, 2 figure

    First observation and amplitude analysis of the B−→D+K−π−B^{-}\to D^{+}K^{-}\pi^{-} decay

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    The B−→D+K−π−B^{-}\to D^{+}K^{-}\pi^{-} decay is observed in a data sample corresponding to 3.0 fb−13.0~\rm{fb}^{-1} of pppp collision data recorded by the LHCb experiment during 2011 and 2012. Its branching fraction is measured to be B(B−→D+K−π−)=(7.31±0.19±0.22±0.39)×10−5{\cal B}(B^{-}\to D^{+}K^{-}\pi^{-}) = (7.31 \pm 0.19 \pm 0.22 \pm 0.39) \times 10^{-5} where the uncertainties are statistical, systematic and from the branching fraction of the normalisation channel B−→D+π−π−B^{-}\to D^{+}\pi^{-}\pi^{-}, respectively. An amplitude analysis of the resonant structure of the B−→D+K−π−B^{-}\to D^{+}K^{-}\pi^{-} decay is used to measure the contributions from quasi-two-body B−→D0∗(2400)0K−B^{-}\to D_{0}^{*}(2400)^{0}K^{-}, B−→D2∗(2460)0K−B^{-}\to D_{2}^{*}(2460)^{0}K^{-}, and B−→DJ∗(2760)0K−B^{-}\to D_{J}^{*}(2760)^{0}K^{-} decays, as well as from nonresonant sources. The DJ∗(2760)0D_{J}^{*}(2760)^{0} resonance is determined to have spin~1.Comment: 39 pages, 10 figures, submitted to Phys. Rev. D. Updated following erratum 10.1103/PhysRevD.93.11990

    Study of B−→DK−π+π−B^{-}\to DK^-\pi^+\pi^- and B−→Dπ−π+π−B^-\to D\pi^-\pi^+\pi^- decays and determination of the CKM angle Îł\gamma

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    We report a study of the suppressed B−→DK−π+π−B^-\to DK^-\pi^+\pi^- and favored B−→Dπ−π+π−B^-\to D\pi^-\pi^+\pi^- decays, where the neutral DD meson is detected through its decays to the K∓π±K^{\mp}\pi^{\pm} and CP-even K+K−K^+K^- and π+π−\pi^+\pi^- final states. The measurement is carried out using a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of 3.0~fb−1^{-1}. We observe the first significant signals in the CP-even final states of the DD meson for both the suppressed B−→DK−π+π−B^-\to DK^-\pi^+\pi^- and favored B−→Dπ−π+π−B^-\to D\pi^-\pi^+\pi^- modes, as well as in the doubly Cabibbo-suppressed D→K+π−D\to K^+\pi^- final state of the B−→Dπ−π+π−B^-\to D\pi^-\pi^+\pi^- decay. Evidence for the ADS suppressed decay B−→DK−π+π−B^{-}\to DK^-\pi^+\pi^-, with D→K+π−D\to K^+\pi^-, is also presented. From the observed yields in the B−→DK−π+π−B^-\to DK^-\pi^+\pi^-, B−→Dπ−π+π−B^-\to D\pi^-\pi^+\pi^- and their charge conjugate decay modes, we measure the value of the weak phase to be Îł=(74−19+20)o\gamma=(74^{+20}_{-19})^{\rm o}. This is one of the most precise single-measurement determinations of Îł\gamma to date.Comment: 22 pages, 9 figures; All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-020.htm

    Observation of the Bs0→ηâ€Čηâ€ČB^0_s\to\eta'\eta' decay

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    The first observation of the Bs0→ηâ€Čηâ€ČB^0_s\to\eta'\eta' decay is reported. The study is based on a sample of proton-proton collisions corresponding to 3.03.0 fb−1{\rm fb^{-1}} of integrated luminosity collected with the LHCb detector. The significance of the signal is 6.46.4 standard deviations. The branching fraction is measured to be [3.31±0.64 (stat)±0.28 (syst)±0.12 (norm)]×10−5[3.31 \pm 0.64\,{\rm (stat)} \pm 0.28\,{\rm (syst)} \pm 0.12\,{\rm (norm)}]\times10^{-5}, where the third uncertainty comes from the B±→ηâ€ČK±B^{\pm}\to\eta' K^{\pm} branching fraction that is used as a normalisation. In addition, the charge asymmetries of B±→ηâ€ČK±B^{\pm}\to\eta' K^{\pm} and B±→ϕK±B^{\pm}\to\phi K^{\pm}, which are control channels, are measured to be (−0.2±1.3)%(-0.2 \pm1.3)\% and (+1.7±1.3)%(+1.7\pm1.3)\%, respectively. All results are consistent with theoretical expectations

    Differential branching fraction and angular analysis of Λb0→ΛΌ+Ό−\Lambda^{0}_{b} \rightarrow \Lambda \mu^+\mu^- decays

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    The differential branching fraction of the rare decay Λb0→ΛΌ+Ό−\Lambda^{0}_{b} \rightarrow \Lambda \mu^+\mu^- is measured as a function of q2q^{2}, the square of the dimuon invariant mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of 3.0 \mbox{ fb}^{-1}, collected by the LHCb experiment. Evidence of signal is observed in the q2q^2 region below the square of the J/ψJ/\psi mass. Integrating over 15 < q^{2} < 20 \mbox{ GeV}^2/c^4 the branching fraction is measured as d\mathcal{B}(\Lambda^{0}_{b} \rightarrow \Lambda \mu^+\mu^-)/dq^2 = (1.18 ^{+ 0.09} _{-0.08} \pm 0.03 \pm 0.27) \times 10^{-7} ( \mbox{GeV}^{2}/c^{4})^{-1}, where the uncertainties are statistical, systematic and due to the normalisation mode, Λb0→J/ψΛ\Lambda^{0}_{b} \rightarrow J/\psi \Lambda, respectively. In the q2q^2 intervals where the signal is observed, angular distributions are studied and the forward-backward asymmetries in the dimuon (AFBlA^{l}_{\rm FB}) and hadron (AFBhA^{h}_{\rm FB}) systems are measured for the first time. In the range 15 < q^2 < 20 \mbox{ GeV}^2/c^4 they are found to be A^{l}_{\rm FB} = -0.05 \pm 0.09 \mbox{ (stat)} \pm 0.03 \mbox{ (syst)} and A^{h}_{\rm FB} = -0.29 \pm 0.07 \mbox{ (stat)} \pm 0.03 \mbox{ (syst)}.Comment: 27 pages, 10 figures, Erratum adde

    Precision measurement of CPCP violation in Bs0→J/ψK+K−B_s^0 \to J/\psi K^+K^- decays

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    The time-dependent CPCP asymmetry in Bs0→J/ψK+K−B_s^0 \to J/\psi K^+K^- decays is measured using pppp collision data, corresponding to an integrated luminosity of 3.03.0fb−1^{-1}, collected with the LHCb detector at centre-of-mass energies of 77 and 88TeV. In a sample of 96 000 Bs0→J/ψK+K−B_s^0 \to J/\psi K^+K^- decays, the CPCP-violating phase ϕs\phi_s is measured, as well as the decay widths ΓL\Gamma_{L} and ΓH\Gamma_{H} of the light and heavy mass eigenstates of the Bs0−Bˉs0B_s^0-\bar{B}_s^0 system. The values obtained are ϕs=−0.058±0.049±0.006\phi_s = -0.058 \pm 0.049 \pm 0.006 rad, Γs≡(ΓL+ΓH)/2=0.6603±0.0027±0.0015\Gamma_s \equiv (\Gamma_{L}+\Gamma_{H})/2 = 0.6603 \pm 0.0027 \pm 0.0015ps−1^{-1}, andΔΓs≡ΓL−ΓH=0.0805±0.0091±0.0032\Delta\Gamma_s \equiv \Gamma_{L} - \Gamma_{H} = 0.0805 \pm 0.0091 \pm 0.0032ps−1^{-1}, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of those quantities to date. A combined analysis with Bs0→J/ψπ+π−B_s^{0} \to J/\psi \pi^+\pi^- decays gives ϕs=−0.010±0.039\phi_s = -0.010 \pm 0.039 rad. All measurements are in agreement with the Standard Model predictions. For the first time the phase ϕs\phi_s is measured independently for each polarisation state of the K+K−K^+K^- system and shows no evidence for polarisation dependence.Comment: 6 figure

    A study of CPCP violation in B∓→Dh∓B^\mp \rightarrow Dh^\mp (h=K,πh=K,\pi) with the modes D→K∓π±π0D \rightarrow K^\mp \pi^\pm \pi^0, D→π+π−π0D \rightarrow \pi^+\pi^-\pi^0 and D→K+K−π0D \rightarrow K^+K^-\pi^0

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    An analysis of the decays of B∓→DK∓B^\mp \rightarrow D K^\mp and B∓→Dπ∓B^\mp \rightarrow D \pi^\mp is presented in which the DD meson is reconstructed in the three-body final states K∓π±π0K^\mp \pi^\pm \pi^0, π+π−π0\pi^+ \pi^- \pi^0 and K+K−π0K^+ K^- \pi^0. Using data from LHCb corresponding to an integrated luminosity of 3.0 fb−1^{-1} of pppp collisions, measurements of several CPCP observables are performed. First observations are obtained of the suppressed ADS decay B∓→[π∓K±π0]Dπ∓B^\mp \rightarrow [\pi^\mp K^\pm \pi^0]_D \pi^\mp and the quasi-GLW decay B∓→[K+K−π0]Dπ∓B^\mp \rightarrow [K^+ K^- \pi^0]_D \pi^\mp. The results are interpreted in the context of the unitarity triangle angle Îł\gamma and related parameters

    Amplitude analysis of B0→Dˉ0K+π−B^0 \rightarrow \bar{D}^0 K^+ \pi^- decays

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    The Dalitz plot distribution of B0→Dˉ0K+π−B^0 \rightarrow \bar{D}^0 K^+ \pi^- decays is studied using a data sample corresponding to 3.0fb−13.0\rm{fb}^{-1} of pppp collision data recorded by the LHCb experiment during 2011 and 2012. The data are described by an amplitude model that contains contributions from intermediate K∗(892)0K^*(892)^0, K∗(1410)0K^*(1410)^0, K2∗(1430)0K^*_2(1430)^0 and D2∗(2460)−D^*_2(2460)^- resonances. The model also contains components to describe broad structures, including the K0∗(1430)0K^*_0(1430)^0 and D0∗(2400)−D^*_0(2400)^- resonances, in the KπK\pi S-wave and the DπD\pi S- and P-waves. The masses and widths of the D0∗(2400)−D^*_0(2400)^- and D2∗(2460)−D^*_2(2460)^- resonances are measured, as are the complex amplitudes and fit fractions for all components included in the amplitude model. The model obtained will be an integral part of a future determination of the angle Îł\gamma of the CKM quark mixing matrix using B0→DK+π−B^0 \rightarrow D K^+ \pi^- decays.Comment: 33 pages, 12 figures; updated for publicatio
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