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

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

Measurements of the branching fractions of Λ c + → pπ−π+, Λ c + → pK−K+, and Λ c + → pπ−K+

The ratios of the branching fractions of the decays $\Lambda_{c}^{+} \rightarrow p \pi^{-} \pi^{+}$, $\Lambda_{c}^{+} \rightarrow p K^{-} K^{+}$, and $\Lambda_{c}^{+} \rightarrow p \pi^{-} K^{+}$ with respect to the Cabibbo-favoured $\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+}$ decay are measured using proton-proton collision data collected with the LHCb experiment at a 7 TeV centre-of-mass energy and corresponding to an integrated luminosity of 1.0 fb$^{-1}$: \begin{align*} \frac{\mathcal{B}(\Lambda_{c}^{+} \rightarrow p \pi^{-} \pi^{+})}{\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+})} &amp; = (7.44 \pm 0.08 \pm 0.18)\,\%, \\ \frac{\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} K^{+})}{\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+})} &amp;= (1.70 \pm 0.03 \pm 0.03)\,\%, \\ \frac{\mathcal{B}(\Lambda_{c}^{+} \rightarrow p \pi^{-} K^{+})}{\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+})} &amp; = (0.165 \pm 0.015 \pm 0.005 )\,\%, \end{align*} where the uncertainties are statistical and systematic, respectively. These results are the most precise measurements of these quantities to date. When multiplied by the world-average value for $\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+})$, the corresponding branching fractions are \begin{align*} \mathcal{B}(\Lambda_{c}^{+} \rightarrow p \pi^{-} \pi^{+}) &amp;= (4.72 \pm 0.05 \pm 0.11 \pm 0.25) \times 10^{-3}, \\ \mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} K^{+}) &amp;= (1.08 \pm 0.02 \pm 0.02 \pm 0.06) \times 10^{-3}, \\ \mathcal{B}(\Lambda_{c}^{+} \rightarrow p \pi^{-} K^{+}) &amp;= (1.04 \pm 0.09 \pm 0.03 \pm 0.05) \times 10^{-4}, \end{align*} where the final uncertainty is due to $\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+})$

Search for Higgs-like bosons decaying into long-lived exotic particles

A search is presented for massive long-lived particles, in the 20–60&nbsp;GeV/c2 mass range with lifetimes between 5 and 100&nbsp;ps. The dataset used corresponds to 0.62fb-1 of proton-proton collision data collected by the LHCb detector at s=7TeV. The particles are assumed to be pair-produced by the decay of a Higgs-like boson with mass between 80 and 140&nbsp;GeV/c2. No excess above the background expectation is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime and of the Higgs-like boson mass