The production of J/\(\psi\) mesons is studied in proton-lead collisions at the centre-of-mass energy per nucleon pair \(\sqrt{s_{\text{NN}}}=8.16\) TeV with the LHCb detector at the LHC. The double ...differential cross-sections of prompt and nonprompt J/\(\psi\) production are measured as functions of the J/\(\psi\) transverse momentum and rapidity in the nucleon-nucleon centre-of-mass frame. Forward-to-backward ratios and nuclear modification factors are determined. The results are compared with theoretical calculations based on collinear factorisation using nuclear parton distribution functions, on the colour glass condensate or on coherent energy loss models.
A study of \(B^{0}_{s} \to \eta_{c} \phi\) and \(B^{0}_{s} \to \eta_{c} \pi^{+}\pi^{-}\) decays is performed using \(pp\) collision data corresponding to an integrated luminosity of 3.0\(\,\rm ...fb^{-1}\), collected with the LHCb detector in Run~1 of the LHC. The observation of the decay \(B^{0}_{s} \to \eta_{c} \phi\) is reported, where the \(\eta_{c}\) meson is reconstructed in the \(p\bar p\), \(K^+K^-\pi^+\pi^-\), \(\pi^+\pi^-\pi^+\pi^-\) and \(K^+K^-K^+K^-\) decay modes and the \(\phi(1020)\) in the \(K^+ K^-\) decay mode. The decay \(B^{0}_{s} \to J/\psi \phi\) is used as a normalisation channel. Evidence is also reported for the decay \(B^{0}_{s} \to \eta_{c} \pi^{+}\pi^{-}\), where the \(\eta_{c}\) meson is reconstructed in the \(p\bar p\) decay mode, using the decay \(B^{0}_{s} \to J/\psi \pi^+ \pi^-\) as a normalisation channel. The measured branching fractions are \begin{eqnarray*} {\mathcal B (B^{0}_{s} \to \eta_{c} \phi)} &=& \left(5.01 \pm 0.53 \pm 0.27 \pm 0.63 \right) \times 10^{-4} \,, \nonumber \\ {\mathcal B (B^{0}_{s} \to \eta_{c} \pi^+ \pi^-)} &=& \left(1.76 \pm 0.59 \pm 0.12 \pm 0.29 \right) \times 10^{-4} \,, \end{eqnarray*} where in each case the first uncertainty is statistical, the second systematic and the third uncertainty is due to the limited knowledge of the external branching fractions.
A search for the decay Bs -> D*-+ \pi+- is presented using a data sample corresponding to an integrated luminosity of 1.0 fb-1 of pp collisions collected by LHCb. This decay is expected to be ...mediated by a W-exchange diagram, with little contribution from rescattering processes, and therefore a measurement of the branching fraction will help to understand the mechanism behind related decays such as Bs -> \pi+ \pi- and Bs -> D Dbar. Systematic uncertainties are minimised by using B0 -> D*-+ \pi+- as a normalisation channel. We find no evidence for a signal, and set an upper limit on the branching fraction of BR(Bs -> D*-+ \pi+-) < 6.1 (7.8) x10^(-6) at 90% (95%) confidence level.
Two general mechanisms are implicated in chemical carcinogenesis. The first involves direct damage to DNA, referred to as genotoxic (GTX), to which the cell responds by repair of the damages, arrest ...of the cell cycle or induction of apoptosis. The second is non-DNA damaging, non-genotoxic (NGTX), in which a wide variety of cellular processes may be involved. Therefore, it can be hypothesized that modulation of the underlying gene expression patterns is profoundly distinct between GTX and NGTX carcinogens, and thus that expression profiling is applicable for classification of chemical carcinogens as GTX or NGTX. We investigated this hypothesis by analysing modulation of gene expression profiles induced by 20 chemical carcinogens in HepG2 cells with application of cDNA microarrays that contain 597 toxicologically relevant genes. In total, 22 treatments were included, divided in two sets. The training set consisted of 16 treatments (nine genotoxins and seven non-genotoxins) and the validation set of six treatments (three and three). Class discrimination models based on Pearson correlation analyses for the 20 most discriminating genes were developed with data from the training set, where after the models were tested with all data. Using all data, the correctness for classification of the carcinogens from the training set was clearly better than that for the validation set, namely 81 and 33%, respectively. Exclusion of the treatments that had only marginal effects on the expression profiles, improved the discrimination for the training and validation sets to 92 and 100% correctness, respectively. Exclusion of the gene expression signals that were hardly altered also improved classification, namely to 94 and 80%. Therefore, our study proves the principle that gene expression profiling can discriminate carcinogens with major differences in their mode of actions, namely genotoxins versus non-genotoxins.
A search for non-resonant D+(s) to pi+mu+mu- and D+(s) to pi-mu+mu+ decays is performed using proton-proton collision data, corresponding to an integrated luminosity of 1.0 fb-1, at sqrt(s) = 7 TeV ...recorded by the LHCb experiment in 2011. No signals are observed and the 90% (95%) confidence level (CL) limits on the branching fractions are B(D+ to pi+mu+mu-) < 7.3 (8.3) x 10-8, B(Ds+ to pi+mu+mu-) < 4.1 (4.8) x 10-7, B(D+ to pi-mu+mu+) < 2.2 (2.5) x 10-8, B(Ds+ to pi-mu+mu+) < 1.2 (1.4) x 10-7. These limits are the most stringent to date.
The energy flow created in pp collisions at sqrt(s)=7 TeV is studied within the pseudorapidity range 1.9<eta<4.9 with data collected by the LHCb experiment. The measurements are performed for ...inclusive minimum-bias interactions, hard scattering processes and events with an enhanced or suppressed diffractive contribution. The results are compared to predictions given by PYTHIA-based and cosmic-ray event generators, which provide different models of soft hadronic interactions.
The first observation of the \(D^0 \to \pi^+\pi^-\mu^+\mu^-\) and \(D^0 \to K^+K^-\mu^+\mu^-\) decays is reported using a sample of proton-proton collisions collected by LHCb at a center-of-mass ...energy of 8\(\,\)TeV, and corresponding to 2\(\,\)fb\(^{-1}\) of integrated luminosity. The corresponding branching fractions are measured using as normalization the decay \(D^0 \to K^- \pi^+\mu^+\mu^-_{\rho^0/\omega}\), where the two muons are consistent with coming from the decay of a \(\rho^0\) or \(\omega\) meson. The results are \(\mathcal{B}(D^0 \to \pi^+\pi^-\mu^+\mu^-)=(9.64\pm0.48\pm0.51\pm0.97)\times10^{-7}\) and \(\mathcal{B}(D^0 \to K^+K^-\mu^+\mu^-)=( 1.54\pm0.27\pm0.09\pm0.16)\times10^{-7}\), where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalization branching fraction. The dependence of the branching fraction on the dimuon mass is also investigated.
A search for CP violation in the phase-space structures of D0 and D0bar decays to the final states K-K+pi-pi+ and pi-pi+pi+pi- is presented. The search is carried out with a data set corresponding to ...an integrated luminosity of 1.0fb^-1 collected in 2011 by the LHCb experiment in \(pp\) collisions at a centre-of-mass energy of 7TeV. For the K-K+pi-pi+ final state, the four-body phase space is divided into 32 bins, each bin with approximately 1800 decays. The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a CP asymmetry greater than 6.5% observed. The phase space of the pi-pi+pi+pi- final state is partitioned into 128 bins, each bin with approximately 2500 decays. The \(p\)-value under the hypothesis of no CP violation is 41%, and in no bin is a CP asymmetry greater than 5.5% observed. All results are consistent with the hypothesis of no CP violation at the current sensitivity.
A search for baryon-number-violating \(\Xi_b^0\) oscillations is performed with a sample of \(pp\) collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 3 ...fb\(^{-1}\). The baryon number at the moment of production is identified by requiring that the \(\Xi_b^0\) come from the decay of a resonance \(\Xi_b^{*-} \to \Xi_b^0 \pi^-\) or \(\Xi_b^{\prime-} \to \Xi_b^0 \pi^-\), and the baryon number at the moment of decay is identified from the final state using the decays \(\Xi_b^0 \to \Xi_c^+ \pi^-, ~ \Xi_c^+ \to p K^- \pi^+\). No evidence of baryon number violation is found, and an upper limit at the 95% confidence level is set on the oscillation rate of \(\omega < 0.08\) ps\(^{-1}\), where \(\omega\) is the associated angular frequency.
PDF