Updated measurements of exclusive J/ψ and ψ(2S) production cross-sections in pp collisions at √s = 7 TeV

The differential cross-section as a function of rapidity has been measured for the exclusive production of J/ψ and ψ(2S) mesons in proton–proton collisions at √s = 7 TeV, using data collected by the LHCb experiment, corresponding to an integrated luminosity of 930 pb−1. The cross-sections times branching fractions to two muons having pseudorapidities between 2.0 and 4.5 are measured to be where the first uncertainty is statistical and the second is systematic. The measurements agree with next-to-leading order QCD predictions as well as with models that include saturation effects

Studies of beauty baryon decays to D0ph− and Λ+ch− final states

Decays of beauty baryons to the D0ph− and Λ+ch− final states (where h indicates a pion or a kaon) are studied using a data sample of pp collisions, corresponding to an integrated luminosity of 1.0  fb−1, collected by the LHCb detector. The Cabibbo-suppressed decays Λ0b→D0pK− and Λ0b→Λ+cK− are observed, and their branching fractions are measured with respect to the decays Λ0b→D0pπ− and Λ0b→Λ+cπ−. In addition, the first observation is reported of the decay of the neutral beauty-strange baryon Ξ0b to the D0pK− final state, and a measurement of the Ξ0b mass is performed. Evidence of the Ξ0b→Λ+cK− decay is also reported

Measurement of the CKM angle γ\gamma using B0→DK∗0B^0 \rightarrow D K^{*0} with D→KS0π+π−D \rightarrow K^0_S \pi^+ \pi^- decays

A model-dependent amplitude analysis of the decay $B^0\rightarrow D(K^0_S\pi^+\pi^-) K^{*0}$ is performed using proton-proton collision data corresponding to an integrated luminosity of 3.0fb$^{-1}$, recorded at $\sqrt{s}=7$ and $8 TeV$ by the LHCb experiment. The CP violation observables $x_{\pm}$ and $y_{\pm}$, sensitive to the CKM angle $\gamma$, are measured to be \begin{eqnarray*} x_- &=& -0.15 \pm 0.14 \pm 0.03 \pm 0.01, y_- &=& 0.25 \pm 0.15 \pm 0.06 \pm 0.01, x_+ &=& 0.05 \pm 0.24 \pm 0.04 \pm 0.01, y_+ &=& -0.65^{+0.24}_{-0.23} \pm 0.08 \pm 0.01, \end{eqnarray*} where the first uncertainties are statistical, the second systematic and the third arise from the uncertainty on the $D\rightarrow K^0_S \pi^+\pi^-$ amplitude model. These are the most precise measurements of these observables. They correspond to $\gamma=(80^{+21}_{-22})^{\circ}$ and $r_{B^0}=0.39\pm0.13$, where $r_{B^0}$ is the magnitude of the ratio of the suppressed and favoured $B^0\rightarrow D K^+ \pi^-$ decay amplitudes, in a $K\pi$ mass region of $\pm50 MeV$ around the $K^*(892)^0$ mass and for an absolute value of the cosine of the $K^{*0}$ decay angle larger than $0.4$.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-2016-007.htm

Search for dark photons produced in 13 TeV pppp collisions

Searches are performed for both promptlike and long-lived dark photons, A 0 , produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using A 0 → μ þ μ − decays and a data sample corresponding to an integrated luminosity of 1 . 6 fb − 1 collected with the LHCb detector. The promptlike A 0 search covers the mass range from near the dimuon threshold up to 70 GeV, while the long-lived A 0 search is restricted to the low-mass region 214 <m ð A 0 Þ < 350 MeV. No evidence for a signal is found, and 90% confidence level exclusion limits are placed on the γ – A 0 kinetic-mixing strength. The constraints placed on promptlike dark photons are the most stringent to date for the mass range 10 . 6 <m ð A 0 Þ < 70 GeV, and are comparable to the best existing limits for m ð A 0 Þ < 0 . 5 GeV. The search for long-lived dark photons is the first to achieve sensitivity using a displaced-vertex signature

Observation of the suppressed ADS modes B →[πKππ]DKand B →[πKππ]Dπ

An analysis of B → DK and B → Dπ decays is presented where the D meson is reconstructed in the four-body nal state Kπππ. Using LHCb data corresponding to an integrated luminosity of 1.0fb1, rst observations are made of the suppressed ADS modes B →[πKππ]D K and B → [πKππ]Dπ with a signicance of 5.1σ and greater than 10σ, respectively. Measurements of CP asymmetries and CP-conserving ratios of partial widths from this family of decays are also performed. The magnitude of the ratio between the suppressed and favoured B → DK amplitudes is determined to be r = 0.097 ±0.011. © 2013 CERN. Published by Elsevier B.V

First observation of the decays (B)over-bar((s))(0) -> Ds+K-pi(+)pi(-) and (B)over-bar((s))(0) -> Ds(1)(2536)(+)pi(-)

The first observation of the decays (B) over bar (0)(s) -> Ds+K-pi(+)pi(-) and (B) over bar (0)(s) -> Ds+K-pi(+)pi(-) are reported using an integrated luminosity of 1.0 fb(-1) recorded by the LHCb experiment. The branching fractions, normalized with respect to (B) over bar (0)(s) -> D-s(+)pi(-)pi(+)pi(-) and (B) over bar (0)(s) -> Ds+K-pi(+)pi(-), respectively, are measured to be B((B) over bar (0)(s)-> DsK-pi(+)pi(-))/B((B) over bar (0)(s)-> D-s pi(-)pi(+)pi(-)) = (5.2 +/- 0.5 +/- 0.3) x 10(-2) and B((B) over bar (0)(s)-> DsK-pi(+)pi(-))/B((B) over bar (0)(s)-> DsK-pi(+)pi(-)) = 0.54 +/- 0.07 +/- 0.07, where the first uncertainty is statistical and the second is systematic. The (B) over bar (0)(s) -> D-s(+) K-pi(+)pi(-) decay is of particular interest as it can be used to measure the weak phase gamma. First observation of the (B) over bar (0)(s) -> D-s1(2536)(+)pi(-), D-s1(+) -> D-s(+) pi(-)pi(+) decay is also presented, and its branching fraction relative to (B) over bar (0)(s) -> D-s(+) pi(-)pi(+)pi(-) is found to be B((B) over bar (0)(s) -> D-s1(2536)(+)pi(-),D-s1(+)-> D-s(+)pi(-)pi(+)/B((B) over bar (0)(s) -> D-s(+)pi(-)pi(+)pi(-))) = (4.0 +/- 1.0 +/- 0.4) x 10(-3). DOI: 10.1103/PhysRevD.86.112005 RI Coca, Cornelia/B-6015-2012; Galli, Domenico/A-1606-2012; Sarti, Alessio/I-2833-201

Observation of the suppressed ADS modes B →[πKππ]DKand B →[πKππ]Dπ

An analysis of B → DK and B → Dπ decays is presented where the D meson is reconstructed in the four-body nal state Kπππ. Using LHCb data corresponding to an integrated luminosity of 1.0fb1, rst observations are made of the suppressed ADS modes B →[πKππ]D K and B → [πKππ]Dπ with a signicance of 5.1σ and greater than 10σ, respectively. Measurements of CP asymmetries and CP-conserving ratios of partial widths from this family of decays are also performed. The magnitude of the ratio between the suppressed and favoured B → DK amplitudes is determined to be r = 0.097 ±0.011. © 2013 CERN. Published by Elsevier B.V

Branching fraction and CP asymmetry of the decays B+ -&gt; K-S(0)pi(+) and B+ -&gt; (KSK+)-K-0

An analysis of B+→KS0π+ and B+→KS0K+ decays is performed with the LHCb experiment. The pp collision data used correspond to integrated luminosities of 1fb-1 and 2fb-1 collected at centre-of-mass energies of √s=7TeV and √s=8TeV, respectively. The ratio of branching fractions and the direct CP asymmetries are measured to be B(B+→KS0K+)/B(B+→KS0π+)=0.064±0.009 (stat.)±0.004(syst.), ACP(B+→KS0π+)=-0.022±0.025(stat.)±0.010 (syst.) and ACP(B+→KS0K+)=-0.21±0.14 (stat.)±0.01 (syst.). The data sample taken at √s=7 TeV is used to search for Bc+→KS0K+ decays and results in the upper limit (fc{dot operator}B(Bc+→KS0K+))/(fu{dot operator}B(B+→KS0π+))&lt;5.8×10-2 at 90% confidence level, where fc and fu denote the hadronisation fractions of a b- quark into a Bc+ or a B+ meson, respectively. © 2013 CERN