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

First experimental study of photon polarization in radiative B-s(0) decays

The polarization of photons produced in radiative B0s decays is studied for the first time. The data are recorded by the LHCb experiment in pp collisions corresponding to an integrated luminosity of 3  fb−1 at center-of-mass energies of 7 and 8 TeV. A time-dependent analysis of the B0s→ϕγ decay rate is conducted to determine the parameter AΔ, which is related to the ratio of right- over left-handed photon polarization amplitudes in b→sγ transitions. A value of AΔ=−0.98+0.46−0.52+0.23−0.20 is measured. This result is consistent with the standard model prediction within 2 standard deviations

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

Precision measurement of the B[0 over s]–[– over B][0 over s] oscillation frequency with the decay B[0 over s]→D[– over s]π[superscript +]

A key ingredient to searches for physics beyond the Standard Model in B[0 over s] mixing phenomena is the measurement of the B[0 over s]–[– over B][0 over s] oscillation frequency, which is equivalent to the mass difference Δm[subscript s] of the B[0 over s] mass eigenstates. Using the world's largest B[0 over s] meson sample accumulated in a dataset, corresponding to an integrated luminosity of 1.0 fb[superscript −1], collected by the LHCb experiment at the CERN LHC in 2011, a measurement of Δm[subscript s] is presented. A total of about 34 000 B[0 over s] → D[− over s]π[superscript +] signal decays are reconstructed, with an average decay time resolution of 44 fs. The oscillation frequency is measured to be Δm[subscript s] = 17.768 ± 0.023 (stat) ± 0.006 (syst) ps[superscript −1], which is the most precise measurement to date.National Science Foundation (U.S.

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

Search for the decay Bs -&gt; D*-+ π+-

A search for the decay Bs -&gt; D*-+ \pi+- is presented using a data sample corresponding to an integrated luminosity of 1.0 fb-1 of pp collisions collected by LHCb. This decay is expected to be mediated by a W-exchange diagram, with little contribution from rescattering processes, and therefore a measurement of the branching fraction will help to understand the mechanism behind related decays such as Bs -&gt; \pi+ \pi- and Bs -&gt; D Dbar. Systematic uncertainties are minimised by using B0 -&gt; D*-+ \pi+- as a normalisation channel. We find no evidence for a signal, and set an upper limit on the branching fraction of BR(Bs -&gt; D*-+ \pi+-) &lt; 6.1 (7.8) x10^(-6) at 90% (95%) confidence level

Measurement of the cross-section for Z-&gt;e+e- production in pp collisions at sqrt{s}=7TeV

A measurement of the cross-section for pp-&gt;Z-&gt;e+e- is presented using data at sqrt{s}=7TeV corresponding to an integrated luminosity of 0.94 fb^{-1}. The process is measured within the kinematic acceptance pT&gt;20GeV/c and 2&lt;\eta&lt;4.5 for the daughter electrons and dielectron invariant mass in the range 60--120GeV/c^2. The cross-section is determined to be \sigma(pp-&gt;Z-&gt;e+e-)=76.0+-0.8+-2.0+-2.6pb where the first uncertainty is statistical, the second is systematic and the third is the uncertainty in the luminosity. The measurement is performed as a function of Z rapidity and as a function of an angular variable which is closely related to the Z transverse momentum. The results are compared with previous LHCb measurements and with theoretical predictions from QCD

Measurement of CP observables in B0 -&gt; D K*0 with D -&gt; K+ K-

The decay B0 -&gt; D K*0 and the charge conjugate mode are studied using 1.0fb-1 of pp collision data collected by the LHCb experiment at sqrt(s) = 7TeV in 2011. The CP asymmetry between the B0 -&gt; D K*0 and the B0bar -&gt; D K*0bar decay rates, with the neutral D meson in the CP-even final state K+K-, is found to be A_d_KK = -0.45 +- 0.23 +- 0.02, where the first uncertainty is statistical and the second is systematic. In addition, favoured B0 -&gt; D K*0 decays are reconstructed with the D meson in the non-CP eigenstate K+ pi-. The ratio of the B-flavour averaged decay rates in D decays to CP and non-CP eigenstates is measured to be R_d_KK = 1.36 (+0.37) (-0.32) +- 0.07, where the ratio of the branching fractions of D0 -&gt; K- pi+ to D0 -&gt; K+ K- decays is included as multiplicative factor. The CP asymmetries measured with two control channels, the favoured B0 -&gt; DK*0 decay with D -&gt; K+ pi- and the Bs0bar -&gt; D K*0 decay with D K+ K-, are also reported