Reference pppp cross-sections for J/ψJ/\psi studies in proton-lead collisions at sNN=5.02\sqrt{s_{NN}} = 5.02~TeV and comparisons between ALICE and LHCb results

The ALICE and LHCb collaborations have studied $J/\psi$ production at forward rapidities in proton-lead collisions at $\sqrt{s}=5.02$~TeV using the dimuon channel. The evaluation of cold nuclear matter effects requires the knowledge of the corresponding $J/\psi$ cross-section in $pp$ collisions at the same centre-of-mass energy and in the same kinematic range. In this note the interpolation procedure used to determine this quantity and the related consistency checks are described. Finally, the results from the two experiments on nuclear modification factors are shortly summarized and found to be in good agreement

Reference pp cross-sections for Υ(1S)\Upsilon(1S) studies in proton-lead collisions at sNN=5.02\sqrt{s_{NN}} = 5.02 TeV and comparisons between ALICE and LHCb results

The ALICE and LHCb collaborations have studied $\Upsilon$ (1$S$) production at large rapidities in proton-lead collisions at $\sqrt{s_{NN}} = 5.02$ TeV at the LHC using di-muon fi nal states. The evaluation of cold nuclear matter effects requires the knowledge of the corresponding $\Upsilon$ (1$S$) production cross section in $pp$ collisions at the same centre-of-mass energy and in the same kinematic range. In this note the interpolation procedures used to determine this quantity and the related consistency checks are described. Finally, the results from the two experiments on nuclear modi fication factors are briefly summarized and found to be in good agreement

Combination of LHC results of the search for Bs→μ+μ−B_s\to\mu^+\mu^- decays

A combination of the results of the search for the decay $B^{0}_{s} \to \mu^{+}\mu^{-}$ is performed using about 0.34 fb$^{-1}$ and 1.14 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}$ = 7 TeV, collected by the LHCb and CMS experiments, respectively, at the Large Hadron Collider at CERN. The observed candidates in both experiments are consistent with the expectation from the sum of backgrounds and Standard Model signal. The combination results in an upper limit on the branching ratio, $B(B^{0}_{s} \to \mu^{+}\mu^{-} < 1.08 \times 10^{-8}$ at 95 % confidence level

Observation of the rare B0s→μ+μ- decay from the combined analysis of CMS and LHCb data

The standard model of particle physics describes the fundamental particles and their interactions via the strong, electromagnetic and weak forces. It provides precise predictions for measurable quantities that can be tested experimentally. The probabilities, or branching fractions, of the strangeB meson (B0 s ) and theB0 meson decaying into two oppositely charged muons (m1 and m2) are especially interesting because of their sensitivity to theories that extend the standard model. The standard model predicts that the B0 s ?m1m2 and B0?m1m2 decays are very rare, with about four of the former occurring for every billion B0 s mesons produced, and one of the latter occurring for every ten billion B0 mesons1 . A difference in the observed branching fractions with respect to the predictions of the standard model would provide a direction in which the standard model should be extended. Before the Large Hadron Collider (LHC) at CERN2 started operating, no evidence for either decay mode had been found. Upper limits on the branching fractions were an order of magnitude above the standard model predictions. The CMS (CompactMuon Solenoid) and LHCb (LargeHadron Collider beauty) collaborations have performed a joint analysis of the data from proton-proton collisions that they collected in 2011 at a centre-ofmass energy of seven teraelectronvolts and in 2012 at eight teraelectronvolts. Here we report the first observation of the B0 s ? m1m2 decay, with a statistical significance exceeding six standard deviations, and the best measurement so far of its branching fraction. Furthermore, we obtained evidence for the B0?m1m2 decay with a statistical significance of three standard deviations. Both measurements are statistically compatible with standard model predictions and allow stringent constraints to be placed on theories beyond the standard model. The LHC experiments will resume taking data in 2015, recording proton-proton collisions at a centre-of-mass energy of 13 teraelectronvolts, which will approximately double the production rates of B0 s and B0 mesons and lead to further improvements in the precision of these crucial tests of the standard model

The impact of intrinsic charm on the parton distribution functions

In this work, we present a new investigation about the impact of intrinsic charm (IC) on the physical observables, in particular, on the heavy structure function $F_2^c$. Since IC distribution is dominant at large Bjorken variable $x$, normally, it is expected that it can be explored only at large $x$. But, by studying the correlation of the charm density in the proton with $F_2^c$, we are going to show that the IC component can also be effective at low $x$. To investigate further, we perform three QCD global analyses of parton distribution functions (PDFs), by including the EMC $F_2^c$ data that are recognized as clear evidence for existence of the intrinsic charm in the proton, and also by considering the IC component. Although the fit of the EMC data is extremely poor due to the data points with lower $x$ values, i.e. $x<$0.05, but these analyses can give us new information about the impact of EMC data and IC contribution on the behaviour of PDFs.Comment: I withdraw this paper since my supervisor require me to withdraw this pape