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

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 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

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

Study of eta-eta ' mixing from measurement of B-(s)(0) -&gt; J/psi eta((')) decay rates

A study of B and Bs meson decays into J/ψ η and J/ψ η′ final states is performed using a data set of proton-proton collisions at centre-of-mass energies of 7 and 8 TeV, collected by the LCHb experiment and corresponding to 3.0 fb−1 of integrated luminosity. The decay B0 → J/ψ η′ is observed for the first time. The following ratios of branching fractions are measured: B(B0→J/ψη′)B(B0s→ J/ψη′)=(2.28±0.65 (stat)±0.10 (syst)±0.13 (fs/fd))×10−2,B(B0→ J/ψη)B(B0s→ J/ψη)=(1.85±0.61 (stat)±0.09 (syst)±0.11 (fs/fd))×10−2, where the third uncertainty is related to the present knowledge of fs/fd, the ratio between the probabilities for a b quark to form a Bs or a B0 meson. The branching fraction ratios are used to determine the parameters of η − η′ meson mixing. In addition, the first evidence for the decay Bs → ψ(2S)η′ is reported, and the relative branching fraction is measured, B(B0s→ ψ(2S)η′)B(B0s→ J/ψη′)=(38.7±9.0 (stat)±1.3 (syst)±0.9(B))×10−2, where the third uncertainty is due to the limited knowledge of the branching fractions of J/ψ and ψ(2S) mesons

Precise measurements of the properties of the B-1(5721)(0,+) and B-2*(5747)(0,+) states and observation of B-+,B-0 pi(-,+) mass structures

Invariant mass distributions of B+pi- and B0pi+ combinations are investigated in order to study excited B mesons. The analysis is based on a data sample corresponding to 3.0 fb-1 of pp collision data, recorded by the LHCb detector at centre-of-mass energies of 7 and 8 TeV. Precise measurements of the masses and widths of the B_1(5721)^(0,+) and B_2*(5747)^(0,+) states are reported. Clear enhancements, particularly prominent at high pion transverse momentum, are seen over background in the mass range 5850--6000 MeV in both B+pi- and B0pi+ combinations. The structures are consistent with the presence of four excited B mesons, labelled B_J(5840)^(0,+) and B_J(5960)^(0,+), whose masses and widths are obtained under different hypotheses for their quantum numbers.Comment: 29 pages, 5 Figures, 8 Table

Amplitude analysis of B− → D+ π−π− decays

The Dalitz plot analysis technique is used to study the resonant substructures of B−→D+π−π− decays in a data sample corresponding to 3.0  fb−1 of pp collision data recorded by the LHCb experiment during 2011 and 2012. A model-independent analysis of the angular moments demonstrates the presence of resonances with spins 1, 2 and 3 at high D+π− mass. The data are fitted with an amplitude model composed of a quasi-model-independent function to describe the D+π− S wave together with virtual contributions from the D∗(2007)0 and B*0 states, and components corresponding to the D∗2(2460)0, D∗1(2680)0, D∗3(2760)0 and D∗2(3000)0 resonances. The masses and widths of these resonances are determined together with the branching fractions for their production in B−→D+π−π− decays. The D+π− S wave has phase motion consistent with that expected due to the presence of the D∗0(2400)0 state. These results constitute the first observations of the D∗3(2760)0 and D∗2(3000)0 resonances, with significances of 10σ and 6.6σ, respectively

Measurement of CPCP observables in B±→DK∗±B^{\pm} \rightarrow D K^{*\pm} decays using two- and four-body DD final states

Measurements of CP observables in B$^{±}$ → DK$^{*±}$ decays are presented, where D denotes a superposition of D$^{0}$ and ${\overline{D}}^0$ meson states. Decays of the D meson to K$^{−}$ π$^{+}$, K$^{−}$ K$^{+}$, π$^{−}$ π$^{+}$, K$^{−}$ π$^{+}$ π$^{−}$ π$^{+}$ and π$^{−}$ π$^{+}$ π$^{−}$ π$^{+}$ are used and the K$^{*±}$ meson is reconstructed in the K$_{S}^{0}$ π$^{±}$ final state. This analysis uses a data sample of pp collisions collected with the LHCb experiment, corresponding to integrated luminosities of 1 fb$^{−1}$, 2 fb$^{−1}$ and 1.8 fb$^{−1}$ at centre-of-mass energies $\sqrt{s}=7$ TeV, 8 TeV and 13 TeV, respectively. The sensitivity of the results to the CKM angle γ is discussed.Measurements of $CP$ observables in $B^{\pm} \rightarrow D K^{*\pm}$ decays are presented, where $D$ denotes a superposition of $D^0$ and $\overline{D^0}$ meson states. Decays of the $D$ meson to $K^{-}\pi^{+}$, $K^{-}K^{+}$, $\pi^{-}\pi^{+}$, $K^{-}\pi^{+}\pi^{-}\pi^{+}$ and $\pi^{-}\pi^{+}\pi^{-}\pi^{+}$ are used and the $K^{*\pm}$ meson is reconstructed in the $K^{0}_{\mathrm{S}}\pi^{\pm}$ final state. This analysis uses a data sample of $pp$ collisions collected with the LHCb experiment, corresponding to integrated luminosities of 1 $\mathrm{fb}^{-1}$, 2 $\mathrm{fb}^{-1}$ and 1.8 $\mathrm{fb}^{-1}$ at centre-of-mass energies $\sqrt{s} =$ 7 TeV, 8 TeV and 13 TeV, respectively. The sensitivity of the results to the CKM angle $\gamma$ is discussed

First observation of B+→Ds+K+K−B^{+} \to D_s^{+}K^{+}K^{-} decays and a search for B+→Ds+ϕB^{+} \to D_s^{+}\phi decays

A search for B$^{+}$ → D$_{s}^{+}$ K$^{+}$K$^{−}$ decays is performed using pp collision data corresponding to an integrated luminosity of 4.8 fb$^{−1}$, collected at centre-of-mass energies of 7, 8 and 13 TeV with the LHCb experiment. A significant signal is observed for the first time and the branching fraction is determined to beA search for $B^{+} \to D_s^{+}K^{+}K^{-}$ decays is performed using $pp$ collision data corresponding to an integrated luminosity of 4.8 fb$^{-1}$, collected at centre-of-mass energies of 7, 8 and 13$\,$TeV with the LHCb experiment. A significant signal is observed for the first time and the branching fraction is determined to be \begin{equation*} \mathcal{B}(B^{+} \to D_s^{+}K^{+}K^{-} ) = (7.1 \pm 0.5 \pm 0.6 \pm 0.7) \times 10^{-6}, \end{equation*} where the first uncertainty is statistical, the second systematic and the third due to the uncertainty on the branching fraction of the normalisation mode $B^{+} \to D_s^{+} \overline{\kern -0.2em D}^{0}$. A search is also performed for the pure annihilation decay $B^{+} \to D_s^{+}\phi$. No significant signal is observed and a limit of \begin{equation*} \mathcal{B}(B^{+} \to D_s^{+}\phi) < 4.9 \times 10^{-7}~(4.2 \times 10^{-7}) \end{equation*} is set on the branching fraction at 95$\%$ (90$\%$) confidence level