1,098 research outputs found

    Granulomatosis with polyangiitis

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    Granulomatosis with polyangiitis is a small and medium vessel vasculitis. It may affect any organ system. Neurological involvement, though less frequent, mostly manifests as peripheral neuropathy. Central nervous system (CNS) involvement as autoimmune cerebritis is rare but may be devastating. We report a patient having CNS involvement in the form of Parkinsonism long before the development of typical upper and lower airway symptoms. Granulomatosis with polyangiitis was diagnosed on the basis of cavitary lung lesions along with epistaxis, granulomatous inflammation from fine needle aspiration (FNAC) of lymph node and high titer of c-ANCA. The patient was commenced on intravenous methylprednisolone followed by mycophenolate mofetil and responded to treatment. Autoimmune cerebritis may present with subacute manifestation of diffuse CNS involvement

    Measurement of quarkonium production at forward rapidity in pp collisions at √s=7 TeV

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    The inclusive production cross sections at forward rapidity of J/ψ , ψ(2S) , Υ (1S) and Υ (2S) are measured in pp collisions at s√=7 TeV with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.35 pb‾¹ . Quarkonia are reconstructed in the dimuon-decay channel and the signal yields are evaluated by fitting the μ+μ− invariant mass distributions. The differential production cross sections are measured as a function of the transverse momentum pT and rapidity y , over the ranges 0<pT<20 GeV/c for J/ψ , 0<pT<12 GeV/c for all other resonances and for \(2.5 . The measured cross sections integrated over pT and y , and assuming unpolarized quarkonia, are: σJ/ψ=6.69±0.04±0.63 μ b, σψ(2S)=1.13±0.07±0.19 μ b, σΥ(1S)=54.2±5.0±6.7 nb and σΥ(2S)=18.4±3.7±2.9 nb, where the first uncertainty is statistical and the second one is systematic. The results are compared to measurements performed by other LHC experiments and to theoretical models

    Transverse momentum dependence of inclusive primary charged-particle production in p–Pb collisions at √sNN=5.02 TeV

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    The transverse momentum ( pT ) distribution of primary charged particles is measured at midrapidity in minimum-bias p–Pb collisions at sNN−−−√=5.02 TeV with the ALICE detector at the LHC in the range \(0.15 GeV/ c . The spectra are compared to the expectation based on binary collision scaling of particle production in pp collisions, leading to a nuclear modification factor consistent with unity for pT larger than 2 GeV/ c , with a weak indication of a Cronin-like enhancement for pT around 4 GeV/c . The measurement is compared to theoretical calculations and to data in Pb–Pb collisions at sNN−−−√=2.76 TeV

    Production of charged pions, kaons and protons at large transverse momenta in pp and Pb-Pb collisions at sNN\sqrt{s_{NN}} = 2.76 TeV

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    Transverse momentum spectra of π±,K±\pi^{\pm}, K^{\pm} and p(pˉ)p(\bar{p}) up to pTp_T = 20 GeV/c at mid-rapidity, |y| \le 0.8, in pp and Pb-Pb collisions at sNN\sqrt{s_{NN}} = 2.76 TeV have been measured using the ALICE detector at the LHC. At intermediate pTp_T (2-8 GeV/c) an enhancement of the proton-to-proton ratio, (p + \bar{p})/(\pi^+ + \pi^-\(), with respect to pp collisions is observed and the ratio reaches 0.80 in central Pb-Pb collisions. The measurement of the nuclear modification factors for \(\pi^{\pm}, K^{\pm} and p(pˉ)p(\bar{p}) indicates that within the systematic and statistical uncertainties they are the same at high pTp_T (> 10 GeV/c), suggesting that the chemical composition of leading particles from jets in the medium is similar to that of vacuum jets.publishedVersio

    Charmonium and e+ee^+e^- pair photoproduction at mid-rapidity in ultra-peripheral Pb-Pb collisions at sNN\sqrt{s_{NN}} = 2.76 TeV

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    The ALICE Collaboration at the LHC has measured the J/ψJ/\psi and ψ\psi' photoproduction at mid-rapidity in ultra-peripheral Pb-Pb collisions at sNN\sqrt{s_{NN}} = 2.76 TeV. The charmonium is identified via its leptonic decay for events where the hadronic activity is required to be minimal. The analysis is based on an event sample corresponding to an integrated luminosity of about 23 μb1{\mu}b^{-1}, The cross section for coherent and incoherent J/ψJ/\psi production in the rapidity interval -0.9 < y < 0.9, are dσJ/ψcoh/dy=2.380.24+0.34(sta+sys)d\sigma_{J/\psi}^{coh}/dy = 2.38^{+0.34}_{-0.24}(sta+sys) mb and dσJ/ψinc/dy=0.980.17+0.19(sta+sys)d\sigma_{J/\psi}^{inc}/dy = 0.98^{+0.19}_{-0.17}(sta+sys) mb, respectively. The results are compared to theoretical models for J/ψJ/\psi production and the coherent cross section is found to be in good agreement with those models which include nuclear gluon shadowing consistent with EPS09 parametrization. In addition the cross section for the process γγe+e\gamma\gamma \to e^+e^- has been measured and found to be in agreement with the STARLIGHT Monte Carlo predictions.publishedVersio

    Measurement of the Cross Section for Electromagnetic Dissociation with Neutron Emission in Pb-Pb Collisions at √sNN = 2.76 TeV

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    The first measurement of neutron emission in electromagnetic dissociation of 208Pb nuclei at the LHC is presented. The measurement is performed using the neutron Zero Degree Calorimeters of the ALICE experiment, which detect neutral particles close to beam rapidity. The measured cross sections of single and mutual electromagnetic dissociation of Pb nuclei at √sNN = 2.76 TeV with neutron emission are σ_single EMD = 187.2±0.2 (stat.) +13.8−12.0 (syst.) b and σ_mutual EMD = 6.2 ± 0.1 (stat.) ±0.4 (syst.) b respectively. The experimental results are compared to the predictions from a relativistic electromagnetic dissociation model.publishedVersio

    Energy dependence of the transverse momentum distributions of charged particles in pp collisions measured by ALICE

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    Differential cross sections of charged particles in inelastic pp collisions as a function of pTp_T have been measured at s\sqrt{s} = 0.9, 2.76 and 7 TeV at the LHC. The pTp_T spectra are compared to NLO-pQCD calculations. Though the differential cross section for an individual s\sqrt{s} cannot be described by NLO-pQCD, the relative increase of cross section with s\sqrt{s} is in agreement with NLO-pQCD. Based on these measurements and observations, procedures are discussed to construct pp reference spectra at s\sqrt{s} = 2.76 and 5.02 TeV up to pTp_T = 50 GeV/c as required for the calculation of the nuclear modification factor in nucleus-nucleus and proton-nucleus collisions.publishedVersio

    Multiplicity dependence of the average transverse momentum in pp, p-Pb, and Pb-Pb collisions at the LHC

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    The average transverse momentum versus the charged-particle multiplicity NchN_{ch} was measured in p-Pb collisions at a collision energy per nucleon-nucleon pair sNN\sqrt{s_{NN}} = 5.02 TeV and in pp collisions at collision energies of s\sqrt{s} = 0.9, 2.76, and 7 Tev in the kinematic range 0.15 with NchN_{ch} is observed, which is much stronger than that measured in Pb-Pb collisions. For pp collisions, this could be attributed, within a model of hadronizing strings, to multiple-parton interactions and to a final-state color reconnection mechanism. The data in p-Pb and Pb-Pb collisions cannot be described by an incoherent superposition of nucleon-nucleon collisions and pose a challenge to most of the event generators.publishedVersio

    Mid-rapidity anti-baryon to baryon ratios in pp collisions at s\sqrt{s} = 0.9, 2.76 and 7 TeV measured by ALICE

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    The ratios of yields of anti-baryons to baryons probes the mechanisms of baryon-number transport. Results for anti-proton/proton, anti-Λ/Λ\Lambda/\Lambda, anti-Ξ+/Ξ\Xi^{+}/\Xi^{-} and anti-Ω+/Ω\Omega^{+}/\Omega^{-} in pp collisions at s\sqrt{s} = 0.9, 2.76 and 7 TeV, measured with the ALICE detector at the LHC, are reported. Within the experimental uncertainties and ranges covered by our measurement, these ratios are independent of rapidity, transverse momentum and multiplicity for all measured energies. The results are compared to expectations from event generators, such as PYTHIA and HIJING/B, that are used to model the particle production in pp collisions. The energy dependence of anti-proton/proton, anti-Λ/Λ\Lambda/\Lambda, anti-Ξ+/Ξ\Xi^{+}/\Xi^{-} and anti-Ω+/Ω\Omega^{+}/\Omega^{-}, reaching values compatible with unity for s\sqrt{s} = 7 TeV, complement the earlier anti-proton/proton measurement of ALICE. These dependencies can be described by exchanges with the Regge-trajectory intercept of αJ\alpha_J ≈ 0.5, which are suppressed with increasing rapidity interval Δy\Delta y, Any significant contribution of an exchange not suppressed at large Δy\Delta y (reached at LHC energies) is disfavoured.publishedVersio

    Centrality dependence of the pseudorapidity density distribution for charged particles in Pb-Pb collisions at sNN\sqrt{s_{NN}} = 2.76 TeV

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    We present the first wide-range measurement of the charged-particle pseudorapidity density distribution, for different centralities (the 0-5%, 5-10%, 10-20%, and 20-30% most central events) in Pb-Pb collisions at sNN\sqrt{s_{NN}} = 2.76 TeV at the LHC. The measurement is performed using the full coverage of the ALICE detectors, -5.0 < η\eta < 5.5, and employing a special analysis technique based on collisions arising from LHC ' satellite' bunches. We present the pseudorapidity density as a function of the number of participating nucleons as well as an extrapolation to the total number of produced charged particles NchN_{ch} = 17165 +/- 772 for the 0-5% most central collisions). From the measured d\)._{ch}\).d\).eta\) distribution we derive the rapidity density distribution, d\)._{ch}\).dy, under simple assumptions. The rapidity density distribution is found to be significantly wider than the predictions of the Landau model, which reproduce data well at RHIC energies. We assess the validity of longitudinal scaling by comparing to lower energy results from RHIC. Finally the mechanisms of the underlying particle production are discussed based on a comparison with various theoretical models.publishedVersio
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