Scientific program of DERICA — prospective accelerator and storage ring facility for radioactive ion beam research

Studies of radioactive ions (RIs) are the most thriving field of low-energy nuclear physics. In this paper, the concept and the scientific agenda of the prospective accelerator and storage ring facility for RI beam (RIB) research are proposed for a large-scale international project based at the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research. The motivation for the new facility is discussed and its characteristics are briefly presented and shown to be comparable to those of advanced world centers, the so-called "RIB factories". In the project, the emphasis is made on studies with short-lived RIBs in storage rings. Aunique feature of the project is the possibility of studying electron-RI interactions in a collider experiment to determine the fundamental properties of nuclear matter, in particular, electromagnetic form factors of exotic nuclei

Observation of the suppressed Λb0→DpK- decay with D→K+π- and measurement of its CP asymmetry

International audienceA study of Λb0 baryon decays to the DpK- final state is presented based on a proton-proton collision data sample corresponding to an integrated luminosity of 9  fb-1 collected with the LHCb detector. Two Λb0 decays are considered, Λb0→DpK- with D→K-π+ and D→K+π-, where D represents a superposition of D0 and D¯0 states. The latter process is expected to be suppressed relative to the former, and is observed for the first time. The ratio of branching fractions of the two decays is measured, and the CP asymmetry of the suppressed mode, which is sensitive to the Cabibbo-Kobayashi-Maskawa angle γ, is also reported

Angular analysis of the rare decay Bs0 {B}_s^0 → ϕμ+^{+}μ−^{−}

An angular analysis of the rare decay ${B}_s^0$→ ϕμ$^{+}$μ$^{−}$ is presented, using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 8.4 fb$^{−1}$. The observables describing the angular distributions of the decay ${B}_s^0$→ ϕμ$^{+}$μ$^{−}$ are determined in regions of q$^{2}$, the square of the dimuon invariant mass. The results are consistent with Standard Model predictions.[graphic not available: see fulltext

Simultaneous determination of CKM angle γ\gamma and charm mixing parameters

A combination of measurements sensitive to the CP violation angle γ of the Cabibbo-Kobayashi-Maskawa unitarity triangle and to the charm mixing parameters that describe oscillations between D$^{0}$ and $\overline{D} ^{0}$ mesons is performed. Results from the charm and beauty sectors, based on data collected with the LHCb detector at CERN’s Large Hadron Collider, are combined for the first time. This method provides an improvement on the precision of the charm mixing parameter y by a factor of two with respect to the current world average. The charm mixing parameters are determined to be $x=\left({0.400}_{-0.053}^{+0.052}\right)\%$ and y = $\left({0.630}_{-0.030}^{+0.033}\right)\%$. The angle γ is found to be γ = $\left({65.4}_{-4.2}^{+3.8}\right){}^{\circ}$ and is the most precise determination from a single experiment.[graphic not available: see fulltext

Simultaneous determination of CKM angle γ\gamma and charm mixing parameters

International audienceA combination of measurements sensitive to the CP violation angle γ of the Cabibbo-Kobayashi-Maskawa unitarity triangle and to the charm mixing parameters that describe oscillations between D$^{0}$ and $\overline{D} ^{0}$ mesons is performed. Results from the charm and beauty sectors, based on data collected with the LHCb detector at CERN’s Large Hadron Collider, are combined for the first time. This method provides an improvement on the precision of the charm mixing parameter y by a factor of two with respect to the current world average. The charm mixing parameters are determined to be $x=\left({0.400}_{-0.053}^{+0.052}\right)\%$ and y = $\left({0.630}_{-0.030}^{+0.033}\right)\%$. The angle γ is found to be γ = $\left({65.4}_{-4.2}^{+3.8}\right){}^{\circ}$ and is the most precise determination from a single experiment.[graphic not available: see fulltext

Observation of excited Ωc0\Omega_c^0 baryons in Ωb−→Ξc+K−π−\Omega_b^- \to \Xi_c^+ K^-\pi^-decays

The first observation of the $Ω_b^- → Ξ_c^+ K^- π^-$ decay is reported using p p collision data at center of mass energies of 7, 8, and 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb$^{-1}$. Four excited $Ω_c^0$ baryons are observed in the $Ξ_c^+ K^-$ mass projection of the $Ω_b^-→ Ξ_c^+ K^- π^-$ decays with the significance of each exceeding five standard deviations. They coincide with the states previously observed in prompt pp and $e^+ e^-$ production. Relative production rates, masses, and natural widths of the states are measured, and a test of spin hypotheses is performed. Moreover, the branching ratio of $Ω_b^- → Ξ_c^+ K^- π^-$ is measured relative to the $Ω_b^- → Ω_c^0 π^-$ decay mode and a precise measurement of the $Ω_b^-$ mass of $6044.3±1.2±1.1_{-0.22}^{+0.19}$ MeV is obtained

Observation of a Λb0−Λ‾b0\Lambda_b^0-\overline{\Lambda}_b^0 production asymmetry in proton-proton collisions at s=7 and 8 TeV\sqrt{s} = 7 \textrm{ and } 8\,\textrm{TeV}

International audienceThis article presents differential measurements of the asymmetry between ${\varLambda}_b^0$ and ${\overline{\varLambda}}_b^0$ baryon production rates in proton-proton collisions at centre-of-mass energies of $\sqrt{s}$ = 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb$^{−1}$. The ${\varLambda}_b^0$ baryons are reconstructed through the inclusive semileptonic decay ${\varLambda}_b^0$ → ${\varLambda}_c^{+}$μ$^{−} \overline{\nu} _{μ}$X. The production asymmetry is measured both in intervals of rapidity in the range 2.15 < y < 4.10 and transverse momentum in 2 < p$_{T}$< 27 GeV/c. The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both $\sqrt{s}$ = 7 and 8 TeV data, assuming no CP violation in the decay. There is evidence for a trend as a function of rapidity with a significance of 4 standard deviations. Comparisons to predictions from hadronisation models in Pythia and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in b-hadron production at LHC energies.[graphic not available: see fulltext