Observation of an Excited Bc+ State

Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc∗(2S31)+ state reconstructed without the low-energy photon from the Bc∗(1S31)+→Bc+γ decay following Bc∗(2S31)+→Bc∗(1S31)+π+π-. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date

Measurement of the inelastic pp cross-section at a centre-of-mass energy of 13TeV

The cross-section for inelastic proton-proton collisions at a centre-of-mass energy of 13TeV is measured with the LHCb detector. The fiducial cross-section for inelastic interactions producing at least one prompt long-lived charged particle with momentum p > 2 GeV/c in the pseudorapidity range 2 < η < 5 is determined to be ϭ acc = 62:2 ± 0:2 ± 2:5mb. The first uncertainty is the intrinsic systematic uncertainty of the measurement, the second is due to the uncertainty on the integrated luminosity. The statistical uncertainty is negligible. Extrapolation to full phase space yields the total inelastic proton-proton cross-section ϭ inel = 75:4 ± 3:0 ± 4:5mb, where the first uncertainty is experimental and the second due to the extrapolation. An updated value of the inelastic cross-section at a centre-of-mass energy of 7TeV is also reported

Measurement of CPCP violation in B0→D∓π±B^{0}\rightarrow D^{\mp}\pi^{\pm} decays

A measurement of the $CP$ asymmetries $S_{f}$ and $S_{\bar{f}}$ in $B^0\to D^{\mp}\pi^{\pm}$ decays is reported. The decays are reconstructed in a dataset collected with the LHCb experiment in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV and corresponding to an integrated luminosity of $3.0 \rm{ fb}^{-1}$. The $CP$ asymmetries are measured to be $S_{f} = 0.058 \pm 0.020 (\rm{stat}) \pm 0.011(\rm{syst})$ and $S_{\bar{f}} = 0.038\pm 0.020 (\text{stat})\pm 0.007 (\text{syst})$. These results are in agreement with, and more precise than, previous determinations. They are used to constrain $|\sin\left(2\beta+\gamma\right)|$ and $\gamma$ to intervals that are consistent with the current world-average values.Comment: 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-2018-009.htm

Evidence for the decay BS0→K‾∗0μ+μ− {B}_S^0\to {\overline{K}}^{\ast 0}{\mu}^{+}{\mu}^{-}

International audienceA search for the decay ${B}_S^0\to {\overline{K}}^{\ast 0}{\mu}^{+}{\mu}^{-}$ is presented using data sets corresponding to 1.0, 2.0 and 1.6 fb$^{−1}$ of integrated luminosity collected during pp collisions with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. An excess is found over the background-only hypothesis with a significance of 3.4 standard deviations. The branching fraction of the ${B}_S^0\to {\overline{K}}^{\ast 0}{\mu}^{+}{\mu}^{-}$ decay is determined to be $\mathrm{\mathcal{B}}\left({B}_s^0\to {\overline{K}}^{\ast 0}{\mu}^{+}{\mu}^{-}\right)=\left[2.9\pm 1.0\left(\mathrm{stat}\right)\pm 0.2\left(\mathrm{syst}\right)\pm 0.3\left(\mathrm{norm}\right)\right]\times {10}^{-8}$ , where the first and second uncertainties are statistical and systematic, respectively. The third uncertainty is due to limited knowledge of external parameters used to normalise the branching fraction measurement

Measurement of the branching fraction and CP asymmetry in B plus . J/.. plus decays

The branching fraction and direct $C\!P$ asymmetry of the decay $B^{+}\rightarrow J/\psi \rho^{+}$ are measured using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to a total integrated luminosity of 3\mbox{fb}^{-1}. The following results are obtained: \begin{align} \mathcal{B}(B^{+}\rightarrow J/\psi \rho^{+}) &= (3.81 ^{+0.25}_{-0.24} \pm 0.35) \times 10^{-5}, \nonumber \\ \mathcal{A}^{C\!P} (B^{+}\rightarrow J/\psi \rho^{+}) &= -0.045^{+0.056}_{-0.057} \pm 0.008, \nonumber \end{align} where the first uncertainties are statistical and the second systematic. Both measurements are the most precise to date.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2018-036.htm

Measurement of forward top pair production in the dilepton channel in <i>pp</i> collisions at √s=13 TeV

Forward top quark pair production is studied in $pp$ collisions in the $\mu eb$ final state using a data sample corresponding to an integrated luminosity of 1.93 fb$^{-1}$ collected with the LHCb experiment at a centre-of-mass energy of 13 TeV. The cross-section is measured in a fiducial region where both leptons have a transverse momentum greater than 20 GeV and a pseudorapidity between 2.0 and 4.5. The quadrature sum of the azimuthal separation and the difference in pseudorapidities, denoted $\Delta R$, between the two leptons must be larger than 0.1. The $b$-jet axis is required to be separated from both leptons by a $\Delta R$ of 0.5, and to have a transverse momentum in excess of 20 GeV and a pseudorapidity between 2.2 and 4.2. The cross-section is measured to be $$\sigma_{t\bar{t}}= 126\pm19\,(\mathrm{stat})\pm16\,(\mathrm{syst})\pm5\,(\mathrm{lumi})\,\,\mathrm{ fb}$$ where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measurement is compatible with the Standard Model prediction.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2017-050.htm

Measurement of the CP asymmetry in B- -&gt; (Ds-D0) and B- -&gt; (D-D0) decays

The CP asymmetry in B- -&gt; (Ds-D0) and B- -&gt; (D-D0) decays is measured using LHCb data corresponding to an integrated luminosity of 3.0 fb(-1), collected in pp collisions at centre-of-mass energies of 7 and 8TeV. The results are A(CP) (B- -&gt; (Ds-D0)) = (-0.4 +/- 0.5 +/- 0.5)% and A(CP) (B- -&gt; (D-D0)) = (2.3 +/- 2.7 +/- 0.4)%, where the first uncertainties are statistical and the second systematic. This is the first measurement of A(CP) (B- -&gt; (Ds-D0)) and the most precise determination of A(CP) (B- -&gt; (D-D0)). Neither result shows evidence of CP violation

Search for CPCP violation through an amplitude analysis of D0→K+K−π+π−D^0 \to K^+ K^- \pi^+ \pi^- decays

International audienceA search for CP violation in the Cabibbo-suppressed D$^{0}$ → K$^{+}$K$^{−}$π$^{+}$π$^{−}$ decay mode is performed using an amplitude analysis. The measurement uses a sample of pp collisions recorded by the LHCb experiment during 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb$^{−1}$. The D$^{0}$ mesons are reconstructed from semileptonic b-hadron decays into D$^{0}$μ$^{−}$X final states. The selected sample contains more than 160 000 signal decays, allowing the most precise amplitude modelling of this D$^{0}$ decay to date. The obtained amplitude model is used to perform the search for CP violation. The result is compatible with CP symmetry, with a sensitivity ranging from 1% to 15% depending on the amplitude considered

Measurement of angular and CP asymmetries in D0→π+π-μ+μ- and D0→K+K-μ+μ- decays

The first measurements of the forward-backward asymmetry of the dimuon pair (A_{FB}), the triple-product asymmetry (A_{2ϕ}), and the charge-parity-conjugation asymmetry (A_{CP}), in D0→π+π-μ+μ- and D0→K+K-μ+μ- decays are reported. They are performed using data from proton-proton collisions collected with the LHCb experiment from 2011 to 2016, corresponding to a total integrated luminosity of 5  fb^{-1}. The asymmetries are measured to be A_{FB}(D^{0}→π^{+}π^{-}μ^{+}μ^{-})=(3.3±3.7±0.6)%, A_{2ϕ}(D^{0}→π^{+}π^{-}μ^{+}μ^{-})=(-0.6±3.7±0.6)%, A_{CP}(D^{0}→π^{+}π^{-}μ^{+}μ^{-})=(4.9±3.8±0.7)%, A_{FB}(D^{0}→K^{+}K^{-}μ^{+}μ^{-})=(0±11±2)%, A_{2ϕ}(D^{0}→K^{+}K^{-}μ^{+}μ^{-})=(9±11±1)%, A_{CP}(D^{0}→K^{+}K^{-}μ^{+}μ^{-})=(0±11±2)%, where the first uncertainty is statistical and the second systematic. The asymmetries are also measured as a function of the dimuon invariant mass. The results are consistent with the standard model predictions

Search for beautiful tetraquarks in the <i>ϒ</i>(1<i>S</i>)μ⁺μ⁻ invariant-mass spectrum

International audienceThe ϒ(1S)μ$^{+}$μ$^{−}$ invariant-mass distribution is investigated for a possible exotic meson state composed of two b quarks and two $\overline{b}$ quarks, ${X}_{b\overline{b}b\overline{b}}$ . The analysis is based on a data sample of pp collisions recorded with the LHCb detector at centre-of-mass energies $\sqrt{s}=7$ , 8 and 13 TeV, corresponding to an integrated luminosity of 6.3 fb$^{−1}$. No significant excess is found, and upper limits are set on the product of the production cross-section and the branching fraction as functions of the mass of the ${X}_{b\overline{b}b\overline{b}}$ state. The limits are set in the fiducial volume where all muons have pseudorapidity in the range [2.0, 5.0], and the ${X}_{b\overline{b}b\overline{b}}$ state has rapidity in the range [2.0, 4.5] and transverse momentum less than 15 GeV/c