Measurement of the CKM angle γ in the B0→DK *0 channel using self-conjugate D→ KS0h+ h- decays

A model-independent study of CP violation in B-0 -> DK (*0) decays is presented using data corresponding to an integrated luminosity of 9 fb(-1) collected by the LHCb experiment at centre-of-mass energies of v s = 7, 8 and 13TeV. The CKM angle. is determined by examining the distributions of signal decays in phase-space bins of the self-conjugate D. K(S)(0)h(+) h(-) decays, where h = p, K. Observables related to CP violation are measured and the angle. is determined to be. = (49+22 -19).. Measurements of the amplitude ratio and strong-phase difference between the favoured and suppressed B-0 decays are also presented

Curvature-bias corrections using a pseudomass method

Momentum measurements for very high momentum charged particles, such as muons from electroweak vector boson decays, are particularly susceptible to charge-dependent curvature biases that arise from misalignments of tracking detectors. Low momentum charged particles used in alignment procedures have limited sensitivity to coherent displacements of such detectors, and therefore are unable to fully constrain these misalignments to the precision necessary for studies of electroweak physics. Additional approaches are therefore required to understand and correct for these effects. In this paper the curvature biases present at the LHCb detector are studied using the pseudomass method in proton-proton collision data recorded at centre of mass energy √s = 13 TeV during 2016, 2017 and 2018. The biases are determined using Z → μ+μ- decays in intervals defined by the data-taking period, magnet polarity and muon direction. Correcting for these biases, which are typically at the 10-4 GeV-1 level, improves the Z → μ+μ- mass resolution by roughly 18% and eliminates several pathological trends in the kinematic-dependence of the mean dimuon invariant mass

Study of Ds1 (2460)+ → Ds+π+π- in B → D‾(*)Ds+π+π- decays

An amplitude analysis of the Ds1(2460)+→Ds+π+π- transition is performed simultaneously in B0→D-Ds+π+π-, B+→D‾0Ds+π+π-, and B0→D*-Ds+π+π- decays. The study is based on a data sample of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of s=7,8, and 13 TeV, corresponding to a total integrated luminosity of 9fb-1. A clear double-peak structure is observed in the m(π+π-) spectrum of the Ds1(2460)+→Ds+π+π- decay. The data can be described either with a model including f0500,f0980, and f2(1270) resonances, in which the contributions of f0(980) and f2(1270) are unexpectedly large, or with a model including f0(500), a doubly charged open-charm tetraquark state Tcs¯++ and its isospin partner Tcs¯0. If the former is considered implausible, the Tcs¯ states are observed with high significance, and the data are consistent with isospin symmetry. When imposing isospin constraints between the two Tcs¯ states, their mass and width are determined to be (2327±13±13) MeV and (96±16-23+170) MeV, respectively, where the first uncertainty is statistical and the second is systematic. The mass is slightly below the DK threshold, and a spin-parity of 0+ is favoured with high significance

Search for the Bs0 → μ+μ−γ decay

A search for the fully reconstructed B0 s → µ +µ −γ decay is performed at the LHCb experiment using proton-proton collisions at √ s = 13 TeV corresponding to an integrated luminosity of 5.4 fb−1 . No signifcant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set B(B 0 s → µ +µ −γ) < 4.2 × 10−8 , m(µ +µ −) ∈ [2mµ, 1.70] GeV/c2 , B(B 0 s → µ +µ −γ) < 7.7 × 10−8 , m(µ +µ −) ∈ [1.70, 2.88] GeV/c2 , B(B 0 s → µ +µ −γ) < 4.2 × 10−8 , m(µ +µ −) ∈ [3.92, mB0 s ] GeV/c2 , at 95% confdence level. Additionally, upper limits are set on the branching fraction in the [2mµ, 1.70] GeV/c2 dimuon mass region excluding the contribution from the intermediate ϕ(1020) meson, and in the region combining all dimuon-mass intervals

Helium identification with LHCb

The identification of helium nuclei at LHCb is achieved using a method based on measurements of ionisation losses in the silicon sensors and timing measurements in the Outer Tracker drift tubes. The background from photon conversions is reduced using the RICH detectors and an isolation requirement. The method is developed using pp collision data at √(s) = 13 TeV recorded by the LHCb experiment in the years 2016 to 2018, corresponding to an integrated luminosity of 5.5 fb-1. A total of around 105 helium and antihelium candidates are identified with negligible background contamination. The helium identification efficiency is estimated to be approximately 50% with a corresponding background rejection rate of up to O(10^12). These results demonstrate the feasibility of a rich programme of measurements of QCD and astrophysics interest involving light nuclei

Curvature-bias corrections using a pseudomass method

Momentum measurements for very high momentum charged particles, such as muons from electroweak vector boson decays, are particularly susceptible to charge-dependent curvature biases that arise from misalignments of tracking detectors. Low momentum charged particles used in alignment procedures have limited sensitivity to coherent displacements of such detectors, and therefore are unable to fully constrain these misalignments to the precision necessary for studies of electroweak physics. Additional approaches are therefore required to understand and correct for these effects. In this paper the curvature biases present at the LHCb detector are studied using the pseudomass method in proton-proton collision data recorded at centre of mass energy √(s)=13 TeV during 2016, 2017 and 2018. The biases are determined using Z→μ + μ - decays in intervals defined by the data-taking period, magnet polarity and muon direction. Correcting for these biases, which are typically at the 10-4 GeV-1 level, improves the Z→μ + μ - mass resolution by roughly 18% and eliminates several pathological trends in the kinematic-dependence of the mean dimuon invariant mass

Study of CP violation in B0 → DK⋆(892)0 decays with D → Kπ(ππ), ππ(ππ), and KK final states

A measurement of CP-violating observables associated with the interference of B0 → D0K⋆ (892)0 and B0 → D¯ 0K⋆ (892)0 decay amplitudes is performed in the D0 → K∓π ±(π +π −), D0 → π +π −(π +π −), and D0 → K+K− fnal states using data collected by the LHCb experiment corresponding to an integrated luminosity of 9 fb−1 . CP-violating observables related to the interference of B0 s → D0K¯ ⋆ (892)0 and B0 s → D¯ 0K¯ ⋆ (892)0 are also measured, but no evidence for interference is found. The B0 observables are used to constrain the parameter space of the CKM angle γ and the hadronic parameters r DK⋆ B0 and δ DK⋆ B0 with inputs from other measurements. In a combined analysis, these measurements allow for four solutions in the parameter space, only one of which is consistent with the world average

Branching fraction measurement of the decay B+→ψ(2S)ϕ(1020)K+B^+ \to \psi(2S) \phi(1020) K^+

The branching fraction of the decay $B^+\to \psi(2S)\phi(1020)K^+$, relative to the topologically similar decay $B^+\to J/\psi \phi(1020) K^+$, is measured using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of $9\,\mathrm{fb}^{-1}$. The ratio is found to be $0.061 \pm 0.004 \pm 0.009$, where the first uncertainty is statistical and the second systematic. Using the world-average branching fraction for $B^+ \to J/\psi \phi(1020) K^+$, the branching fraction for the decay $B^+\to \psi(2S) \phi(1020) K^+$ is found to be $(3.0 \pm 0.2 \pm 0.5 \pm 0.2) \times 10^{-6}$, where the first uncertainty is statistical, the second systematic, and the third is due to the branching fraction of the normalization channel.The branching fraction of the decay $B^+ \to \psi(2S)\,\phi(1020)\,K^+$, relative to the topologically similar decay $B^+ \to J/\psi\,\phi(1020)\,K^+$, is measured using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$. The ratio is found to be $0.061 \pm 0.004 \pm 0.009$, where the first uncertainty is statistical and the second systematic. Using the world-average branching fraction for $B^+ \to J/\psi\,\phi(1020)\,K^+$, the branching fraction for the decay $B^+ \to \psi(2S)\,\phi(1020)\,K^+$ is found to be $(3.0 \pm 0.2 \pm 0.5 \pm 0.2) \times 10^{-6}$, where the first uncertainty is statistical, the second systematic, and the third is due to the branching fraction of the normalization channel.The branching fraction of the decay $B^+\to \psi(2S)\phi(1020)K^+$, relative to the topologically similar decay $B^+\to J/\psi \phi(1020) K^+$, is measured using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of $9\,\mathrm{fb}^{-1}$. The ratio is found to be $0.061 \pm 0.004 \pm 0.009$, where the first uncertainty is statistical and the second systematic. Using the world-average branching fraction for $B^+ \to J/\psi \phi(1020) K^+$, the branching fraction for the decay $B^+\to \psi(2S) \phi(1020) K^+$ is found to be $(3.0 \pm 0.2 \pm 0.5 \pm 0.2) \times 10^{-6}$, where the first uncertainty is statistical, the second systematic, and the third is due to the branching fraction of the normalization channel

Search for charge-parity violation in semileptonically tagged D0→K+π−D^{0} \to K^{+} \pi^{-} decays

An analysis of the flavour oscillations of the charmed neutral meson is presented. The ratio of ${D^{0} \to K^{+} \pi^{-}}$ and ${D^{0} \to K^{-} \pi^{+}}$ decay rates is measured as a function of the decay time of the $D^{0}$ meson and compared with the charge-conjugated system to search for charge-parity violation. The meson flavour at production is double-tagged by the charges of the muon and pion in the preceding ${\kern 0.18em \overline{\kern -0.18em B}\to{D^{*}(2010)^{+}} \mu^{-} X}$ and ${{D^{*}(2010)^{+}} \to D^{0} \pi^{+}}$ decays, respectively. These decays are selected from proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of ${13\,\text{TeV}}$ and corresponding to an integrated luminosity of ${5.4\,\text{fb}^{-1}}$. The flavour oscillation parameters, relating to the differences in mass and width of the mass eigenstates, are found to be ${y^\prime=(5.8\pm1.6)\times10^{-3}}$ and ${(x^\prime)^2=(0.0\pm1.2)\times10^{-4}}$. No evidence for charge-parity violation is seen either in the flavour oscillations or in the decay, where the direct charge-parity asymmetry is measured to be ${A_{D}=(2.3\pm1.7)\,{\%}}$.An analysis of the flavour oscillations of the charmed neutral meson is presented. The ratio of D$^{0}$ → K$^{+}$π$^{−}$ and D$^{0}$ → K$^{−}$π$^{+}$ decay rates is measured as a function of the decay time of the D$^{0}$ meson and compared with the charge-conjugated system to search for charge-parity violation. The meson flavour at production is double-tagged by the charges of the muon and pion in the preceding $\overline{B}\to {D}^{\ast }{(2010)}^{+}{\mu}^{-}X$ and D$^{∗}$(2010)$^{+}$ → D$^{0}$π$^{+}$ decays, respectively. These decays are selected from proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 5.4 fb$^{−1}$. The flavour oscillation parameters, relating to the differences in mass and width of the mass eigenstates, are found to be y′ = (5.8 ± 1.6) × 10$^{−3}$ and (x′)$^{2}$ = (0.0 ± 1.2) × 10$^{−4}$. No evidence for charge-parity violation is seen either in the flavour oscillations or in the decay, where the direct charge-parity asymmetry is measured to be A$_{D}$ = (2.3 ± 1.7) %.[graphic not available: see fulltext]An analysis of the flavour oscillations of the charmed neutral meson is presented. The ratio of $D^{0} \to K^{+} \pi^{-}$ and $D^{0} \to K^{-} \pi^{+}$ decay rates is measured as a function of the decay time of the $D^{0}$ meson and compared with the charge-conjugated system to search for charge-parity violation. The meson flavour at production is double-tagged by the charges of the muon and pion in the preceding $\overline{B} \to D^{*}(2010)^{+} \mu^{-} X$ and ${{D^{*}(2010)^{+}} \to D^{0}\pi^{+}}$ decays, respectively. These decays are selected from proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of ${13\,\text{TeV}}$ and corresponding to an integrated luminosity of ${5.4\,\text{fb}^{-1}}$. The flavour oscillation parameters, relating to the differences in mass and width of the mass eigenstates, are found to be ${y^\prime=(5.8\pm1.6)\times10^{-3}}$ and ${(x^\prime)^2=(0.0\pm1.2)\times10^{-4}}$. No evidence for charge-parity violation is seen either in the flavour oscillations or in the decay, where the direct charge-parity asymmetry is measured to be ${A_{D}=(2.3\pm1.7)\,{\%}}$

Observation of the very rare Σ+→pμ+μ−\Sigma^+ \to p \mu^+ \mu^- decay

The first observation of the $\Sigma^+ \to p \mu^+ \mu^-$ decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of $5.4\,\rm{fb}^{-1}$, collected with the LHCb detector at a centre-of-mass energy of 13~TeV. A yield of $237\pm 16$ $\Sigma^+ \to p \mu^+ \mu^-$ decays is obtained, where the uncertainty is statistical only. A branching fraction of $(1.08 \pm 0.17) \times 10^{-8}$ is measured, where the uncertainty includes statistical and systematic sources. No evidence of resonant structures is found in the dimuon invariant-mass distribution. All results are compatible with Standard Model expectations. This represents the rarest decay of a baryon ever observed.The first observation of the Σ+→pμ+μ- decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 5.4  fb-1, collected with the LHCb detector at a center-of-mass energy of 13 TeV. A yield of 237±16  Σ+→pμ+μ- decays is obtained, where the uncertainty is statistical only. A branching fraction of (1.08±0.17)×10-8 is measured, where the uncertainty includes statistical and systematic sources. No evidence of resonant structures is found in the dimuon invariant-mass distribution. All results are compatible with standard model expectations. This represents the rarest decay of a baryon ever observed.The first observation of the $\Sigma^+ \to p \mu^+ \mu^-$ decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of $5.4\,\rm{fb}^{-1}$, collected with the LHCb detector at a centre-of-mass energy of 13~TeV. A yield of $237\pm 16$$\Sigma^+ \to p \mu^+ \mu^-$ decays is obtained, where the uncertainty is statistical only. A branching fraction of $(1.08 \pm 0.17) \times 10^{-8}$ is measured, where the uncertainty includes statistical and systematic sources. No evidence of resonant structures is found in the dimuon invariant-mass distribution. All results are compatible with Standard Model expectations. This represents the rarest decay of a baryon ever observed