LHCb Physics Performance Uwer, Ulrich
B Physics at Hadron Machines,
01/2004, Letnik:
722
Journal Article
Recenzirano
(LHCb Collaboration) The LHCb detector has recently undergone a reoptimization with respect to its original design. In the following, the expected physics potential of the reoptimized detector is ...discussed. The expectations are based on a Monte Carlo simulation of the detector performance including the simulation of the trigger. LHCb will offer an excellent opportunity to determine precisely the CKM parameters. The manifold of different CP measurements will over-constrain the unitarity triangles and will allow to spot new physics, if present.
Embryo formation is the first patterning process during vegetative plant growth. Using transposons as insertional mutagens in Arabidopsis, we identified the mutant edd1 that shows embryo-defective ...development. The insertion mutation is lethal, arresting embryo growth between the globular and heart stages of embryonic development. The mutant phenotype cosegregates with a transposed Dissociation element. Sequences flanking the transposed element were isolated and used to isolate a full-length cDNA clone representing the wild-type EDD1 gene. Complementation of the mutant through Agrobacterium-mediated gene transfer of an EDD1 wild-type copy as well as loss of the transposon concomitant with phenotypic reversion demonstrated that the transposon had caused the mutation. Based on homology to Escherichia coli, the EDD1 gene is predicted to encode a novel glycyl-tRNA synthetase (GlyRS) that has not been identified previously in higher plants. An N-terminal portion of the plant protein is able to direct a marker protein into pea chloroplasts. Thus, the gene identified by the embryo-defective insertion mutation encodes a GlyRS homolog, probably acting within the plastidic compartment
To isolate brassinosteroid (BR) inducible genes, a subtractive cDNA-cloning strategy was applied. One of the isolated genes encodes a plant homologue to yeast old yellow enzymes (OYE) with strong ...sequence similarity to two cloned 12-oxo-phytodienoic acid reductases (
OPR1 and
OPR2) from
A. thaliana and was termed
12-oxophytodienoate reductase 3 (
OPR3; accession number: AJ238149). The expression of the
OPR3 gene is induced by brassinosteroids, jasmonic acid (JA), and by a variety of stimuli like UV-light, touch, wind, wounding, and application of a detergent. Recombinant OPR3 protein converts 12-oxophytodienoate (OPDA) into 12-oxo phytoenoic acid (OPC8: 0), indicating the participation of
OPR3 in the biosynthesis of JA from linolenic acid via the Vick-Zimmerman-pathway. In plants, OPC8: 0 is inevitably metabolized to JA by three cycles of β-oxidation. Both OPDA and JA are signal molecules involved in developmental processes and stress responses. Depending on environmental or developmental conditions, OPR potentially regulates the ratio between these two signal molecules. The yeast old yellow enzymes act on various enones and phenols including steroids, catalyzing reduction and disproportionation reactions. Thus, in addition to OPDA to OPC8: 0 conversion,
OPR3 might be involved in further biosynthetic or degradative pathways in plants. As
OPR3 expression is increased through treatment with brassinosteroids, it provides a potential link between brassinosteroid action and JA synthesis. BRs may thus influence the stress responses of plants through stimulation of JA synthesis.
Abstract The prompt production of Λ c + baryons is studied in proton-lead collisions collected with the LHCb detector at the LHC. The data sample corresponds to an integrated luminosity of 1.58 nb−1 ...recorded at a nucleon-nucleon centre-of-mass energy of s N N = 5.02 $$ \sqrt{s_{\mathrm{NN}}}=5.02 $$ TeV. Measurements of the differential cross-section and the forwardbackward production ratio are reported for Λ c + baryons with transverse momenta in the range 2 < p T < 10 GeV/c and rapidities in the ranges 1.5 < y ∗ < 4.0 and −4.5 < y ∗ < −2.5 in the nucleon-nucleon centre-of-mass system. The ratio of cross-sections of Λ c + baryons and D 0 mesons is also reported. The results are compared with next-to-leading order calculations that use nuclear parton distribution functions.
Abstract Measurements are reported of the central exclusive production of J/ψ and ψ(2S) mesons in pp collisions at a centre-of-mass energy of 13 TeV. Backgrounds are significantly reduced compared to ...previous measurements made at lower energies through the use of new forward shower counters. The products of the cross-sections and the branching fractions for the decays to dimuons, where both muons are within the pseudorapidity range 2.0 < η < 4.5, are measured to be σ J / ψ → μ + μ − = 435 ± 18 ± 11 ± 17 p b σ ψ 2 S → μ + μ − = 11.1 ± 1.1 ± 0.3 ± 0.4 p b . $$ \begin{array}{c}\hfill {\sigma}_{J/\psi \to {\mu}^{+}{\mu}^{-}} = 435 \pm 18 \pm 11 \pm 17\ \mathrm{p}\mathrm{b}\hfill \\ {}\hfill {\sigma}_{\psi (2S)\to {\mu}^{+}{\mu}^{-}} = 11.1 \pm 1.1 \pm 0.3 \pm 0.4\ \mathrm{p}\mathrm{b}.\hfill \end{array} $$ The first uncertainties are statistical, the second are systematic, and the third are due to the luminosity determination. The cross-sections are also measured differentially for meson rapidities between 2.0 and 4.5. Good agreement is observed with theoretical predictions. Photoproduction cross-sections are derived and compared to previous experiments, and a deviation from a pure power-law extrapolation of lower energy data is observed.
Abstract A measurement of Z → τ + τ − production cross-section is presented using data, corresponding to an integrated luminosity of 2 fb−1, from pp collisions at s=8 $$ \sqrt{s}=8 $$ TeV collected ...by the LHCb experiment. The τ + τ − candidates are reconstructed in final states with the first tau lepton decaying leptonically, and the second decaying either leptonically or to one or three charged hadrons. The production cross-section is measured for Z bosons with invariant mass between 60 and 120 GeV/c 2, which decay to tau leptons with transverse momenta greater than 20 GeV/c and pseudorapidities between 2.0 and 4.5. The cross-section is determined to be σpp→Z→τ+τ−=95.8±2.1±4.6±0.2±1.1 $$ {\sigma}_{pp}{{}_{\to Z\to {\tau}^{+}}}_{\tau^{-}}=95.8 \pm 2.1 \pm 4.6 \pm 0.2 \pm 1.1 $$ pb, where the first uncertainty is statistical, the second is systematic, the third is due to the LHC beam energy uncertainty, and the fourth to the integrated luminosity uncertainty. This result is compatible with NNLO Standard model predictions. The ratio of the cross-sections for Z → τ + τ − to Z → μ + μ − (Z → e + e −), determined to be 1.01 ± 0.05 (1.02 ± 0.06), is consistent with the lepton-universality hypothesis in Z decays.
Abstract The inclusive D s ± production asymmetry is measured in pp collisions collected by the LHCb experiment at centre-of-mass energies of s=7 $$ \sqrt{s}=7 $$ and 8 TeV. Promptly produced D s ± ...mesons are used, which decay as D s ± → ϕπ±, with ϕ → K + K −. The measurement is performed in bins of transverse momentum, p T, and rapidity, y, covering the range 2.5 < p T < 25.0 GeV/c and 2.0 < y < 4.5. No kinematic dependence is observed. Evidence of nonzero D s ± production asymmetry is found with a significance of 3.3 standard deviations.
Abstract Forward top quark pair production is studied in pp collisions in the μeb final state using a data sample corresponding to an integrated luminosity of 1.93 fb−1 collected with the LHCb ...experiment at a centre-of-mass energy of 13 TeV. The cross-section is measured in a fiducial region where both leptons have a transverse momentum greater than 20 GeV and a pseudorapidity between 2.0 and 4.5. The quadrature sum of the azimuthal separation and the difference in pseudorapidities, denoted ΔR, between the two leptons must be larger than 0.1. The b-jet axis is required to be separated from both leptons by a ΔR of 0.5, and to have a transverse momentum in excess of 20 GeV and a pseudorapidity between 2.2 and 4.2. The cross-section is measured to be σtt¯=126±19stat±16syst±5lumifb $$ {\sigma}_{t\overline{t}}=126\pm 19\left(\mathrm{stat}\right)\pm 16\left(\mathrm{syst}\right)\pm 5\left(\mathrm{lumi}\right)\mathrm{f}\mathrm{b} $$ where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measurement is compatible with the Standard Model prediction.
Abstract A search for the decay BS0→K¯∗0μ+μ− $$ {B}_S^0\to {\overline{K}}^{\ast 0}{\mu}^{+}{\mu}^{-} $$ is presented using data sets corresponding to 1.0, 2.0 and 1.6 fb−1 of integrated luminosity ...collected during pp collisions with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. An excess is found over the background-only hypothesis with a significance of 3.4 standard deviations. The branching fraction of the BS0→K¯∗0μ+μ− $$ {B}_S^0\to {\overline{K}}^{\ast 0}{\mu}^{+}{\mu}^{-} $$ decay is determined to be ℬBs0→K¯∗0μ+μ−=2.9±1.0stat±0.2syst±0.3norm×10−8 $$ \mathrm{\mathcal{B}}\left({B}_s^0\to {\overline{K}}^{\ast 0}{\mu}^{+}{\mu}^{-}\right)=\left2.9\pm 1.0\left(\mathrm{stat}\right)\pm 0.2\left(\mathrm{syst}\right)\pm 0.3\left(\mathrm{norm}\right)\right\times {10}^{-8} $$, where the first and second uncertainties are statistical and systematic, respectively. The third uncertainty is due to limited knowledge of external parameters used to normalise the branching fraction measurement.
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