70 Search Results

We present the measurement of 𝜋⁺-argon inelastic cross sections using the ProtoDUNE single-phase liquid argon time projection chamber in the incident 𝜋⁺ kinetic energy range of 500–800 MeV in multiple exclusive channels (absorption, charge exchange, and the remaining inelastic interactions). The results of this analysis are important inputs to simulations of liquid argon neutrino experiments such as the Deep Underground Neutrino Experiment and the Short Baseline Neutrino program at Fermi National Accelerator Laboratory. They will be employed to improve the modeling of final state interactions within neutrino event generators used by these experiments, as well as the modeling of 𝜋⁺-argonmore » secondary interactions within the liquid argon. This is the first measurement of 𝜋⁺-argon absorption at this kinetic energy range as well as the first ever measurement of 𝜋⁺-argon charge exchange.« less

A sample of 𝑝⁢𝑝 collision data, corresponding to an integrated luminosity of 5.4 fb⁻¹ and collected by the LHCb experiment during LHC Run 2, is used to measure the ratio of the lifetime of the $$Ξ^0_b$$ baryon to that of the $$Λ^0_b$$ baryon, 𝑟_𝜏 $$≡$$ $$𝜏_{Ξ^0_b}$$$$/𝜏_{Λ^0_b}$$. The value 𝑟$$^{\textrm{Run 2}}_𝜏$$ =1.004 ± 0.009 ± 0.006 is obtained, where the first uncertainty is statistical and the second systematic. This value is averaged with the corresponding value from Run 1 to obtain 𝑟_𝜏 =1.004 ± 0.008 ± 0.005. Multiplying by the known value of the $$Λ^0_b$$ lifetime yields $$𝜏_{Ξ^0_b}$$ = 1.475 ±more » 0.012 ± 0.008 ± 0.009 ps, where the last uncertainty is due to the limited knowledge of the $$Λ^0_b$$ lifetime. This measurement improves the precision of the current world average of the $$Ξ^0_b$$ lifetime by about a factor of two, and is in good agreement with the most recent theoretical predictions.« less

A study is presented of $B^{+}\to K_{\mathrm{S}}^0{K}^{-}{\pi }^{+}{K}^{+}$ and $B^{+}\to K_{\mathrm{S}}^0{K}^{+}{\pi }^{-}{K}^{+}$ decays based on the analysis of proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$ . The ${more »}_{}^{}$ K S 0 K π invariant-mass distributions of both $B^{+}$ decay modes show, in the $m\left(K_{\mathrm{S}}^{0}K\pi \right)<1.85\mathrm{GeV}$ mass region, large activity which is resolved using an amplitude analysis. A simple model, where $J^{PC}$ amplitudes are described by multiple Breit-Wigner functions with appropriate angular distributions, provides a good description of the experimental data. In this approach a complex mixture of $J^{PC}=0^{-+}$ , $1^{++}$ and $1^{+-}$ amplitudes is observed that is dominated by $\eta \left(1405\right)$ , $\eta \left(1470\right)$ , $\eta \left(1760\right)$ , $f_1\left(1285\right)$ , $f_1\left(1420\right)$ and $h_1\left(1405\right)$ resonances. The $K_{\mathrm{S}}^{0}K\pi$ Dalitz plots are dominated by asymmetric crossing $K^{*}\overline{K}$ bands which are different for the two $B^{+}$ decay modes. This is due to a different interference pattern between the $1^{++}$ and $1^{+-}$ amplitudes in the two channels. Branching fractions are measured for each resonant contribution. © 2025 CERN, for the LHCb Collaboration 2025 CERN« less

The branching fraction of the decay $B^{+}\to \psi \left(2S\right)\varphi \left(1020\right)K^{+}$ , relative to the topologically similar decay $B^{+}\to J/\psi \varphi \left(1020\right)K^{+}$ , 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 $0.061\pm 0.004more »$ ± 0.009 , where the first uncertainty is statistical and the second systematic. Using the world-average branching fraction for $B^{+}\to J/\psi \varphi \left(1020\right)K^{+}$ , the branching fraction for the decay $B^{+}\to \psi \left(2S\right)\varphi \left(1020\right)K^{+}$ 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. © 2025 CERN, for the LHCb Collaboration 2025 CERN« less

The first measurement of the $CP$ asymmetry of the decay rate ( $A_{CP}$ ) and the $CP$ average ( $\mathrm{\Sigma }{A}_{\mathrm{FB}}$ ) and $CP$ asymmetry ( $\mathrm{\Delta }{A}_{\mathrm{FB}}$ ) of the forward-backward asymmetry in the muon system of ${\mathrm{\Lambda }}_c^{+}\to p{\mu }^{+}{\mu }^{-}$ decays is reported. The measurement is performed using a data sample of proton-proton collisions, recordedmore » by the LHCb experiment from 2016 to 2018 at a center-of-mass energy of 13 TeV, which corresponds to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ . The asymmetries are measured in two regions of dimuon mass near the  $\varphi$ -meson mass peak. The dimuon-mass integrated results are $A_{CP}=(-1.1\pm 4.0\pm 0.5)\%$ , $\mathrm{\Sigma }{A}_{\mathrm{FB}}=(3.9\pm 4.0\pm 0.6)\%$ , $\mathrm{\Delta }{A}_{\mathrm{FB}}=(3.1\pm 4.0\pm 0.4)\%$ , where the first uncertainty is statistical and the second systematic. The results are consistent with the conservation of $CP$ symmetry and the Standard Model expectations. © 2025 CERN, for the LHCb Collaboration 2025 CERN« less

The first test of lepton flavor universality between muons and electrons using $B^{+}\to K^{+}{\pi }^{+}{\pi }^{-}{\ell }^{+}{\ell }^{-}$ ( $\ell =e$ , $\mu$ ) decays is presented. The measurement is performed with data from proton-proton collisions collected by the LHCb experiment at center-of-mass energies of 7,more » 8, and 13 TeV, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$ . The ratio of branching fractions between $B^{+}\to K^{+}{\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ and $B^{+}\to K^{+}{\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-}$ decays is measured in the dilepton invariant-mass-squared range $1.1<q^2<7.0{\mathrm{GeV}}^2/c^4$ and is found to be $R_{K\pi \pi }^{-1}=1.31_{-0.17}^{+0.18}\left(\mathrm{stat}){}_{-0.09}^{+0.12}\right(\mathrm{syst})$ , in agreement with the standard model prediction. The first observation of the $B^{+}\to K^{+}{\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ decay is also reported. © 2025 CERN, for the LHCb Collaboration 2025 CERN« less

The determination of the direction of a stellar core collapse via its neutrino emission is crucial for the identification of the progenitor for a multimessenger follow-up. A highly effective method of reconstructing supernova directions within the Deep Underground Neutrino Experiment (DUNE) is introduced. The supernova neutrino pointing resolution is studied by simulating and reconstructing electron-neutrino charged-current absorption on ⁴⁰Ar and elastic scattering of neutrinos on electrons. Procedures to reconstruct individual interactions, including a newly developed technique called “brems flipping,” as well as the burst direction from an ensemble of interactions are described. Performance of the burst direction reconstruction is evaluatedmore » for supernovae happening at a distance of 10 kpc for a specific supernova burst flux model. The pointing resolution is found to be 3.4 degrees at 68% coverage for a perfect interaction-channel classification and a fiducial mass of 40 kton, and 6.6 degrees for a 10 kton fiducial mass respectively. Assuming a 4% rate of charged-current interactions being misidentified as elastic scattering, DUNE’s burst pointing resolution is found to be 4.3 degrees (8.7 degrees) at 68% coverage.« less

A search for $CP$ violation in ${\mathrm{\Lambda }}_b^0\to p{K}^{-}$ and ${\mathrm{\Lambda }}_b^0\to p{\pi }^{-}$ decays is presented using the full Run 1 and Run 2 data samples of $pp$ collisions collected with the LHCb detector, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$ at center-of-mass energies of 7, 8, and 13 TeV. For the Run 2 data sample, the $CP$ -violatingmore » asymmetries are measured to be $A_{CP}^{p{K}^{-}}=(-1.4\pm 0.7\pm 0.4)\%$ and $A_{CP}^{p{\pi }^{-}}=(0.4\pm 0.9\pm 0.4)\%$ , where the first uncertainty is statistical and the second is systematic. Following significant improvements in the evaluation of systematic uncertainties compared to the previous LHCb measurement, the Run 1 dataset is reanalyzed to update the corresponding results. When combining the Run 2 and updated Run 1 measurements, the final results are found to be $A_{CP}^{p{K}^{-}}=(-1.1\pm 0.7\pm 0.4)\%$ and $A_{CP}^{p{\pi }^{-}}=(0.2\pm 0.8\pm 0.4)\%$ , constituting the most precise measurements of these asymmetries to date. © 2025 CERN, for the LHCb Collaboration 2025 CERN« less

A search for $D^0$ meson decays to the ${\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ and $K^{+}{K}^{-}{e}^{+}{e}^{-}$ final states is reported using a sample of proton-proton collisions collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $6{\mathrm{fb}}^{-1}$ . The decay $D^0\to {\pi }^{more »}$ + π − e + e − is observed for the first time when requiring that the two electrons are consistent with coming from the decay of a $\varphi$ or ${\rho }^0/\omega$ meson. The corresponding branching fractions are measured relative to the $D^0\to K^{-}{\pi }^{-}[e^{+}{e}^{-}{]}_{{\rho }^0/\omega }$ decay, where the two electrons are consistent with coming from the decay of a ${\rho }^0$ or $\omega$ meson. No evidence is found for the $D^0\to K^{+}{K}^{-}{e}^{+}{e}^{-}$ decay and world-best limits are set on its branching fraction. The results are compared to, and found to be consistent with, the branching fractions of the $D^0\to {\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-}$ and $D^0\to K^{+}{K}^{-}{\mu }^{+}{\mu }^{-}$ decays recently measured by LHCb and confirm lepton universality at the current precision. © 2025 CERN, for the LHCb Collaboration 2025 CERN« less

The determination of the direction of a stellar core collapse via its neutrino emission is crucial for the identification of the progenitor for a multimessenger follow-up. A highly effective method of reconstructing supernova directions within the Deep Underground Neutrino Experiment (DUNE) is introduced. The supernova neutrino pointing resolution is studied by simulating and reconstructing electron-neutrino charged-current absorption on ${}_{40}\mathrm{Ar}$ and elastic scattering of neutrinos on electrons. Procedures to reconstruct individual interactions, including a newly developed technique called “brems flipping,” as well as the burst direction from anmore » ensemble of interactions are described. Performance of the burst direction reconstruction is evaluated for supernovae happening at a distance of 10 kpc for a specific supernova burst flux model. The pointing resolution is found to be 3.4 degrees at 68% coverage for a perfect interaction-channel classification and a fiducial mass of 40 kton, and 6.6 degrees for a 10 kton fiducial mass respectively. Assuming a 4% rate of charged-current interactions being misidentified as elastic scattering, DUNE’s burst pointing resolution is found to be 4.3 degrees (8.7 degrees) at 68% coverage.« less