28,187 research outputs found

    Improved measurement of CP violation parameters in Bs0→J/ψK+K− decays in the vicinity of the ϕ(1020) resonance

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    The decay-time-dependent C P asymmetry in B 0 s → J / ψ ( → μ + μ − ) K + K − decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 6     fb − 1 , collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 B 0 s signal decays with an invariant K + K − mass in the vicinity of the ϕ ( 1020 ) resonance, the C P -violating phase ϕ s is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B 0 s − ¯ B 0 s system, Δ Γ s , and the difference of the average B 0 s and B 0 meson decay widths, Γ s − Γ d . The values obtained are ϕ s = − 0.039 ± 0.022 ± 0.006     rad , Δ Γ s = 0.0845 ± 0.0044 ± 0.0024     ps − 1 , and Γ s − Γ d = − 0.005 6 + 0.0013 − 0.0015 ± 0.0014     ps − 1 , where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase ϕ s is also measured independently for each polarization state of the K + K − system and shows no evidence for polarization dependence

    Measurement of the Z boson production cross-section in pp collisions at √s = 5.02 TeV

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    The frst measurement of the Z boson production cross-section at centre-of-mass energy √s = 5.02 TeV in the forward region is reported, using pp collision data collected by the LHCb experiment in year 2017, corresponding to an integrated luminosity of 100±2 pb−1 . The production cross-section is measured for fnal-state muons in the pseudorapidity range 2.0 < η < 4.5 with transverse momentum pT > 20 GeV/c. The integrated cross-section is determined to be σZ→µ+µ− = 39.6 ± 0.7(stat) ± 0.6(syst) ± 0.8(lumi) pb for the di-muon invariant mass in the range 60 < Mµµ < 120 GeV/c 2 . This result and the diferential cross-section results are in good agreement with theoretical predictions at next-to-next-to-leading order in the strong coupling constant. Based on a previous LHCb measurement of the Z boson production cross-section in pPb collisions at √ sNN = 5.02 TeV, the nuclear modifcation factor RpPb is measured for the frst time at this energy. The measured values are 1.2 +0.5 −0.3 (stat) ± 0.1(syst) in the forward region (1.53 < y∗ µ < 4.03) and 3.6 +1.6 −0.9 (stat)±0.2(syst) in the backward region (−4.97 < y∗ µ < −2.47), where y ∗ µ represents the muon rapidity in the centre-of-mass frame

    Production of η and η′ mesons in pp and pPb collisions

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    The production of η and η ′ mesons is studied in proton-proton and proton-lead collisions collected with the LHCb detector. Proton-proton collisions are studied at center-of-mass energies of 5.02 and 13 TeV and proton-lead collisions are studied at a center-of-mass energy per nucleon of 8.16 TeV . The studies are performed in center-of-mass (c.m.) rapidity regions 2.5 < y c . m . < 3.5 (forward rapidity) and − 4.0 < y c . m . < − 3.0 (backward rapidity) defined relative to the proton beam direction. The η and η ′ production cross sections are measured differentially as a function of transverse momentum for 1.5 < p T < 10 GeV and 3 < p T < 10 GeV , respectively. The differential cross sections are used to calculate nuclear modification factors. The nuclear modification factors for η and η ′ mesons agree at both forward and backward rapidity, showing no significant evidence of mass dependence. The differential cross sections of η mesons are also used to calculate η / π 0 cross-section ratios, which show evidence of a deviation from the world average. These studies offer new constraints on mass-dependent nuclear effects in heavy-ion collisions, as well as η and η ′ meson fragmentation

    Measurement of CP Violation in B<sup>0</sup>→ψ(→ℓ<sup>+</sup>ℓ<sup>−</sup>)K<sup>0</sup><sub>S</sub>(→π<sup>+</sup>π<sup>−</sup>) Decays

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    A measurement of time-dependent CP violation in the decays of B0 and B̅0 mesons to the final states J/ψ(→μ+μ−)K0S, ψ(2S)(→μ+μ−)K0S and J/ψ(→e+e−)K0S with K0S→π+π− is presented. The data correspond to an integrated luminosity of 6  fb−1 collected at a center-of-mass energy of √s = 13  TeV with the LHCb detector. The CP-violation parameters are measured to be SψK0S=0.717±0.013(stat)±0.008(syst) and CψK0S=0.008±0.012(stat)±0.003(syst). This measurement of SψK0S represents the most precise single measurement of the CKM angle β to date and is more precise than the current world average. In addition, measurements of the CP-violation parameters of the individual channels are reported and a combination with the LHCb Run 1 measurements is performed

    Computational Analysis of Cas Proteins Unlocks New Potential in HIV-1 Targeted Gene Therapy

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    Introduction: The human immunodeficiency virus type 1 (HIV-1) pandemic has been slowed with the advent of anti-retroviral therapy (ART). However, ART is not a cure and as such has pushed the disease into a chronic infection. One potential cure strategy that has shown promise is the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas gene editing system. It has recently been shown to successfully edit and/or excise the integrated provirus from infected cells and inhibit HIV-1 in vitro, ex vivo, and in vivo. These studies have primarily been conducted with SpCas9 or SaCas9. However, additional Cas proteins are discovered regularly and modifications to these known proteins are being engineered. The alternative Cas molecules have different requirements for protospacer adjacent motifs (PAMs) which impact the possible targetable regions of HIV-1. Other modifications to the Cas protein or gRNA handle impact the tolerance for mismatches between gRNA and the target. While reducing off-target risk, this impacts the ability to fully account for HIV-1 genetic variability. Methods: This manuscript strives to examine these parameter choices using a computational approach for surveying the suitability of a Cas editor for HIV-1 gene editing. The Nominate, Diversify, Narrow, Filter (NDNF) pipeline measures the safety, broadness, and effectiveness of a pool of potential gRNAs for any PAM. This technique was used to evaluate 46 different potential Cas editors for their HIV therapeutic potential. Results: Our examination revealed that broader PAMs that improve the targeting potential of editors like SaCas9 and LbCas12a have larger pools of useful gRNAs, while broader PAMs reduced the pool of useful SpCas9 gRNAs yet increased the breadth of targetable locations. Investigation of the mismatch tolerance of Cas editors indicates a 2-missmatch tolerance is an ideal balance between on-target sensitivity and off-target specificity. Of all of the Cas editors examined, SpCas-NG and SPRY-Cas9 had the highest number of overall safe, broad, and effective gRNAs against HIV. Discussion: Currently, larger proteins and wider PAMs lead to better targeting capacity. This implies that research should either be targeted towards delivering longer payloads or towards increasing the breadth of currently available small Cas editors. With the discovery and adoption of additional Cas editors, it is important for researchers in the HIV-1 gene editing field to explore the wider world of Cas editors

    Convergence of resistance and evolutionary responses in Escherichia coli and Salmonella enterica co-inhabiting chicken farms in China

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    Sharing of genetic elements among different pathogens and commensals inhabiting same hosts and environments has significant implications for antimicrobial resistance (AMR), especially in settings with high antimicrobial exposure. We analysed 661 Escherichia coli and Salmonella enterica isolates collected within and across hosts and environments, in 10 Chinese chicken farms over 2.5 years using novel data-mining methods. Most isolates within same hosts possessed same clinically relevant AMR-carrying mobile genetic elements (plasmids: 70.6%, transposons: 78%), which also showed recent common evolution. Machine learning revealed known and novel AMR-associated mutations and genes underlying resistance to 28 antimicrobials and primarily associated with resistance in E. coli and susceptibility in S. enterica. Many were essential and affected same metabolic processes in both species, albeit with varying degrees of phylogenetic penetration. Multi-modal strategies are crucial to investigate the interplay of mobilome, resistance and metabolism in cohabiting bacteria, especially in ecological settings where community-driven resistance selection occurs

    Measurement of CP Violation in B<sup>0</sup>→ψ(→ℓ<sup>+</sup>ℓ<sup>−</sup>)K<sup>0</sup><sub>S</sub>(→π<sup>+</sup>π<sup>−</sup>) Decays

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    A measurement of time-dependent CP violation in the decays of B0 and B̅0 mesons to the final states J/ψ(→μ+μ−)K0S, ψ(2S)(→μ+μ−)K0S and J/ψ(→e+e−)K0S with K0S→π+π− is presented. The data correspond to an integrated luminosity of 6  fb−1 collected at a center-of-mass energy of √s = 13  TeV with the LHCb detector. The CP-violation parameters are measured to be SψK0S=0.717±0.013(stat)±0.008(syst) and CψK0S=0.008±0.012(stat)±0.003(syst). This measurement of SψK0S represents the most precise single measurement of the CKM angle β to date and is more precise than the current world average. In addition, measurements of the CP-violation parameters of the individual channels are reported and a combination with the LHCb Run 1 measurements is performed

    A search for rare B → Dμ + μ − decays