121 research outputs found

    Evidence for the strangeness-changing weak decay Ξb−→Λb0π−\Xi_b^-\to\Lambda_b^0\pi^-

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    Using a pppp collision data sample corresponding to an integrated luminosity of 3.0~fb−1^{-1}, collected by the LHCb detector, we present the first search for the strangeness-changing weak decay Ξb−→Λb0π−\Xi_b^-\to\Lambda_b^0\pi^-. No bb hadron decay of this type has been seen before. A signal for this decay, corresponding to a significance of 3.2 standard deviations, is reported. The relative rate is measured to be fΞb−fΛb0B(Ξb−→Λb0π−)=(5.7±1.8−0.9+0.8)×10−4{{f_{\Xi_b^-}}\over{f_{\Lambda_b^0}}}{\cal{B}}(\Xi_b^-\to\Lambda_b^0\pi^-) = (5.7\pm1.8^{+0.8}_{-0.9})\times10^{-4}, where fΞb−f_{\Xi_b^-} and fΛb0f_{\Lambda_b^0} are the b→Ξb−b\to\Xi_b^- and b→Λb0b\to\Lambda_b^0 fragmentation fractions, and B(Ξb−→Λb0π−){\cal{B}}(\Xi_b^-\to\Lambda_b^0\pi^-) is the branching fraction. Assuming fΞb−/fΛb0f_{\Xi_b^-}/f_{\Lambda_b^0} is bounded between 0.1 and 0.3, the branching fraction B(Ξb−→Λb0π−){\cal{B}}(\Xi_b^-\to\Lambda_b^0\pi^-) would lie in the range from (0.57±0.21)%(0.57\pm0.21)\% to (0.19±0.07)%(0.19\pm0.07)\%.Comment: 7 pages, 2 figures, 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-2015-047.htm

    A double-blind placebo controlled trial into the impacts of HMB supplementation and exercise on free-living muscle protein synthesis, muscle mass and function, in older adults

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    Age-related sarcopenia and dynapenia are associated with frailty and metabolic diseases. Resistance exercise training (RET) adjuvant to evidence-based nutritional intervention(s) have been shown as mitigating strategies. Given that HMB supplementation during RET improves lean body mass in younger humans (Wilson et al., 2014), and that we have shown that HMB acutely stimulates muscle protein synthesis (MPS) and inhibits breakdown; we hypothesized that chronic supplementation of HMB adjuvant to RET would enhance MPS and muscle mass/function in older people.We recruited 16 healthy older men (PLA: 68.5±1.0y, HMB: 67.8±1.1y) for a randomised double-blind-placebo (PLA) controlled trial (HMB 3 x 1g/day vs. PLA) involving a 6-week unilateral progressive RET regime (6 x 8 repetitions, 75% 1-RM, 3.wk-1). D2O dosing was performed over the first two weeks (0-2w) and last two weeks (4-6w) with bilateral vastus lateralis (VL) biopsies at 0-2 and 4-6 weeks (each time 75±2 min after a single bout of RE) for quantification of early and later MPS responses and post-RE myogenic gene expression. Thigh lean mass was measured by DXA, VL thickness and architecture (fibre length and pennation angle) by ultrasound at 0/3/6 weeks, and strength by knee extensor 1-RM testing and MVC by isokinetic dynamometry (approx. every 10 days).RET induced strength increases (1-RM) in the exercised leg in both groups (398±22N to 499±30N HMB vs. 396±29N to 510±43N PLA (both

    Measurements of long-range near-side angular correlations in sNN=5\sqrt{s_{\text{NN}}}=5TeV proton-lead collisions in the forward region

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    Two-particle angular correlations are studied in proton-lead collisions at a nucleon-nucleon centre-of-mass energy of sNN=5\sqrt{s_{\text{NN}}}=5TeV, collected with the LHCb detector at the LHC. The analysis is based on data recorded in two beam configurations, in which either the direction of the proton or that of the lead ion is analysed. The correlations are measured in the laboratory system as a function of relative pseudorapidity, Δη\Delta\eta, and relative azimuthal angle, Δϕ\Delta\phi, for events in different classes of event activity and for different bins of particle transverse momentum. In high-activity events a long-range correlation on the near side, Δϕ≈0\Delta\phi \approx 0, is observed in the pseudorapidity range 2.0<η<4.92.0<\eta<4.9. This measurement of long-range correlations on the near side in proton-lead collisions extends previous observations into the forward region up to η=4.9\eta=4.9. The correlation increases with growing event activity and is found to be more pronounced in the direction of the lead beam. However, the correlation in the direction of the lead and proton beams are found to be compatible when comparing events with similar absolute activity in the direction analysed.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-2015-040.htm

    Teaching of Energy Issues: A debate proposal for a GLobal Reorientation

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    The growing awareness of serious difficulties in the learning of energy issues has produced a great deal of research, most of which is focused on specific conceptual aspects. In our opinion, the difficulties pointed out in the literature are interrelated and connected to other aspects (conceptual as well as procedural and axiological), which are not sufficiently taken into account in previous research. This paper aims to carry out a global analysis in order to avoid the more limited approaches that deal only with individual aspects. From this global analysis we have outlined 24 propositions that are put forward for debate to lay the foundations for a profound reorientation of the teaching of energy topics in upper high school courses, in order to facilitate a better scientific understanding of these topics, avoid many students' misconceptions and enhance awareness of the current situation of planetary emergency

    Integrative analysis of genomic variants reveals new associations of candidate haploinsufficient genes with congenital heart disease

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    Congenital Heart Disease (CHD) affects approximately 7-9 children per 1000 live births. Numerous genetic studies have established a role for rare genomic variants at the copy number variation (CNV) and single nucleotide variant level. In particular, the role of de novo mutations (DNM) has been highlighted in syndromic and non-syndromic CHD. To identify novel haploinsufficient CHD disease genes we performed an integrative analysis of CNVs and DNMs identified in probands with CHD including cases with sporadic thoracic aortic aneurysm (TAA). We assembled CNV data from 7,958 cases and 14,082 controls and performed a gene-wise analysis of the burden of rare genomic deletions in cases versus controls. In addition, we performed mutation rate testing for DNMs identified in 2,489 parent-offspring trios. Our combined analysis revealed 21 genes which were significantly affected by rare genomic deletions and/or constrained non-synonymous de novo mutations in probands. Fourteen of these genes have previously been associated with CHD while the remaining genes (FEZ1, MYO16, ARID1B, NALCN, WAC, KDM5B and WHSC1) have only been associated in singletons and small cases series, or show new associations with CHD. In addition, a systems level analysis revealed shared contribution of CNV deletions and DNMs in CHD probands, affecting protein-protein interaction networks involved in Notch signaling pathway, heart morphogenesis, DNA repair and cilia/centrosome function. Taken together, this approach highlights the importance of re-analyzing existing datasets to strengthen disease association and identify novel disease genes

    Model-independent measurement of mixing parameters in D0^{0} → KS0_{S}^{0} π+^{+}π−^{−} decays

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    The first model-independent measurement of the charm mixing parameters in the decay D0→KSπ+π−D^0 \to K_S \pi^+ \pi^- is reported, using a sample of pppp collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 1.0 fb−1^{-1} at a centre-of-mass energy of 7 TeV. The measured values are \begin{eqnarray*} x &=& (-0.86 \pm 0.53 \pm 0.17) \times 10^{-2}, \\ y &=& (+0.03 \pm 0.46 \pm 0.13) \times 10^{-2}, \end{eqnarray*} where the first uncertainties are statistical and include small contributions due to the external input for the strong phase measured by the CLEO collaboration, and the second uncertainties are systematic.Comment: 25 pages, 3 figures. Sign error in x fixed as of v2. 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-2015-042.htm

    Search for the lepton-flavour violating decay D0→e±Ό∓D^0 \to e^\pm\mu^\mp

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    A search for the lepton-flavour violating decay D0→e±Ό∓D^0 \to e^\pm \mu^\mp is made with a dataset corresponding to an integrated luminosity of 3.03.0 fb−1^{-1} of proton-proton collisions at centre-of-mass energies of 77 TeV and 88 TeV, collected by the LHCb experiment. Candidate D0D^0 mesons are selected using the decay D∗+→D0π+D^{*+} \to D^0 \pi^+ and the D0→e±Ό∓D^0 \to e^\pm \mu^\mp branching fraction is measured using the decay mode D0→K−π+D^0 \to K^- \pi^+ as a normalisation channel. No significant excess of D0→e±Ό∓D^0 \to e^\pm \mu^\mp candidates over the expected background is seen, and a limit is set on the branching fraction, B(D0→e±Ό∓)<1.3×10−8\mathcal{B}(D^0 \to e^\pm \mu^\mp) < 1.3 \times 10^{-8}, at 90 % confidence level. This is an order of magnitude lower than the previous limit and it further constrains the parameter space in some leptoquark models and in supersymmetric models with R-parity violation.A search for the lepton-flavour violating decay D0→e±Ό∓ is made with a dataset corresponding to an integrated luminosity of 3.0fb−1 of proton–proton collisions at centre-of-mass energies of 7 TeV and 8 TeV , collected by the LHCb experiment. Candidate D0 mesons are selected using the decay D⁎+→D0π+ and the D0→e±Ό∓ branching fraction is measured using the decay mode D0→K−π+ as a normalization channel. No significant excess of D0→e±Ό∓ candidates over the expected background is seen, and a limit is set on the branching fraction, B(D0→e±Ό∓)<1.3×10−8 , at 90% confidence level. This is an order of magnitude lower than the previous limit and it further constrains the parameter space in some leptoquark models and in supersymmetric models with R-parity violation.A search for the lepton-flavour violating decay D0→e±Ό∓D^0 \to e^\pm \mu^\mp is made with a dataset corresponding to an integrated luminosity of 3.0 fb−1^{-1} of proton-proton collisions at centre-of-mass energies of 77 TeV and 88 TeV, collected by the LHCb experiment. Candidate D0D^0 mesons are selected using the decay D∗+→D0π+D^{*+} \to D^0 \pi^+ and the D0→e±Ό∓D^0 \to e^\pm \mu^\mp branching fraction is measured using the decay mode D0→K−π+D^0 \to K^-\pi^+ as a normalisation channel. No significant excess of D0→e±Ό∓D^0 \to e^\pm \mu^\mp candidates over the expected background is seen, and a limit is set on the branching fraction, B(D0→e±Ό∓)<1.3×10−8\mathcal{B}(D^0 \to e^\pm \mu^\mp) < 1.3 \times 10^{-8}, at 90 % confidence level. This is an order of magnitude lower than the previous limit and it further constrains the parameter space in some leptoquark models and in supersymmetric models with R-parity violation
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