253 research outputs found

    Search for the doubly heavy baryon Ξbc+\it{\Xi}_{bc}^{+} decaying to J/ψΞc+J/\it{\psi} \it{\Xi}_{c}^{+}

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    A first search for the Ξbc+→J/ψΞc+\it{\Xi}_{bc}^{+}\to J/\it{\psi}\it{\Xi}_{c}^{+} decay is performed by the LHCb experiment with a data sample of proton-proton collisions, corresponding to an integrated luminosity of 9 fb−19\,\mathrm{fb}^{-1} recorded at centre-of-mass energies of 7, 8, and 13 TeV13\mathrm{\,Te\kern -0.1em V}. Two peaking structures are seen with a local (global) significance of 4.3 (2.8)4.3\,(2.8) and 4.1 (2.4)4.1\,(2.4) standard deviations at masses of 6571 MeV ⁣/c26571\,\mathrm{Me\kern -0.1em V\!/}c^2 and 6694 MeV ⁣/c26694\,\mathrm{Me\kern -0.1em V\!/}c^2, respectively. Upper limits are set on the Ξbc+\it{\Xi}_{bc}^{+} baryon production cross-section times the branching fraction relative to that of the Bc+→J/ψDs+B_{c}^{+}\to J/\it{\psi} D_{s}^{+} decay at centre-of-mass energies of 8 and 13 TeV13\mathrm{\,Te\kern -0.1em V}, in the Ξbc+\it{\Xi}_{bc}^{+} and in the Bc+B_{c}^{+} rapidity and transverse-momentum ranges from 2.0 to 4.5 and 0 to 20 GeV ⁣/c20\,\mathrm{Ge\kern -0.1em V\!/}c, respectively. Upper limits are presented as a function of the Ξbc+\it{\Xi}_{bc}^{+} mass and lifetime.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-005.html (LHCb public pages

    Second-Sphere Effects in Dinuclear Fe<sup>III</sup>Zn<sup>II</sup> Hydrolase Biomimetics: Tuning Binding and Reactivity Properties

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    Herein, we report the synthesis and characterization of two dinuclear Fe<sup>III</sup>Zn<sup>II</sup> complexes [Fe<sup>III</sup>Zn<sup>II</sup>LP1] (<b>1</b>) and [Fe<sup>III</sup>Zn<sup>II</sup>LP2] (<b>2</b>), in which LP1 and LP2 are conjugated systems containing one and two pyrene groups, respectively, connected via the diamine −HN­(CH<sub>2</sub>)<sub>4</sub>NH– spacer to the well-known N<sub>5</sub>O<sub>2</sub>-donor H<sub>2</sub>L ligand (H<sub>2</sub>L = 2-bis­{[(2-pyridylmethyl)­aminomethyl]-6-[(2-hydroxybenzyl)­(2-pyridylmethyl)]­aminomethyl}-4-methylphenol). The complex [Fe<sup>III</sup>Zn<sup>II</sup>L1] (<b>3</b>), in which H<sub>2</sub>L was modified to H<sub>2</sub>L1, with a carbonyl group attached to the terminal phenol group, was included in this study for comparison purposes.<sup>1</sup> Both complexes <b>1</b> and <b>2</b> were satisfactorily characterized in the solid state and in solution. Extended X-ray absorption fine structure data for <b>1</b> and <b>3</b> in an acetonitrile solution show that the multiply bridged structure seen in the solid state of <b>3</b> is retained in solution. Potentiometric and UV–vis titration of <b>1</b> and <b>2</b> show that electrostatic interaction between the protonated amino groups and coordinated water molecules significantly decreases the p<i>K</i><sub>a</sub> of the iron­(III)-bound water compared to those of <b>3</b>. On the other hand, catalytic activity studies using <b>1</b> and <b>2</b> in the hydrolysis of the activated substrate bis­(2,4-dinitrophenyl)­phosphate (BDNPP) resulted in a significant increase in the association of the substrate (<i>K</i><sub>ass</sub> ≅ 1/<i>K</i><sub>M</sub>) compared to that of <b>3</b> because of electrostatic and hydrophobic interactions between BDNPP and the side-chain diaminopyrene of the ligands H<sub>2</sub>LP1 and H<sub>2</sub>LP2. In addition, the introduction of the pyrene motifs in <b>1</b> and <b>2</b> enhanced their activity toward DNA and as effective antitumor drugs, although the biochemical mechanism of the latter effect is currently under investigation. These complexes represent interesting examples of how to promote an increase in the activity of traditional artificial metal nucleases by introducing second-coordination-sphere effects

    The LHCb upgrade I

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    International audienceThe LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software

    The LHCb upgrade I

    No full text
    International audienceThe LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software

    The LHCb upgrade I

    No full text
    International audienceThe LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software

    The LHCb upgrade I

    No full text
    The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software

    The LHCb upgrade I

    No full text
    International audienceThe LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software
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