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Open Access Publications from the University of California

Scholarly Works (7 results)

  • Article
  • Peer Reviewed
UC Berkeley Previously Published Works (2013)
Differential cross sections of charged particles in inelastic pp collisions as a function of pT have been measured at [Formula: see text] at the LHC. The pT spectra are compared to NLO-pQCD calculations. Though the differential cross section for an individual [Formula: see text] cannot be described by NLO-pQCD, the relative increase of cross section with [Formula: see text] is in agreement with NLO-pQCD. Based on these measurements and observations, procedures are discussed to construct pp reference spectra at [Formula: see text] up to pT=50 GeV/c as required for the calculation of the nuclear modification factor in nucleus-nucleus and proton-nucleus collisions.
    Cover page: Energy dependence of the transverse momentum distributions of charged particles in pp collisions measured by ALICE
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2014)
    Event-by-event fluctuations of the mean transverse momentum of charged particles produced in pp collisions at 0.9, 2.76 and 7 TeV, and Pb–Pb collisions at 2.76 TeV are studied as a function of the charged-particle multiplicity using the ALICE detector at the LHC. Dynamical fluctuations indicative of correlated particle emission are observed in all systems. The results in pp collisions show little dependence on collision energy. The Monte Carlo event generators PYTHIA and PHOJET are in qualitative agreement with the data. Peripheral Pb–Pb data exhibit a similar multiplicity dependence as that observed in pp. In central Pb–Pb, the results deviate from this trend, featuring a significant reduction of the fluctuation strength. The results in Pb–Pb are in qualitative agreement with previous measurements in Au–Au at lower collision energies and with expectations from models that incorporate collective phenomena.
      Cover page: Event-by-event mean pT fluctuations in pp and Pb–Pb collisions at the LHC
      • Article
      • Peer Reviewed
      UC Berkeley Previously Published Works (2015)
      The production of the strange and double-strange baryon resonances ([Formula: see text], [Formula: see text]) has been measured at mid-rapidity ([Formula: see text][Formula: see text]) in proton-proton collisions at [Formula: see text] [Formula: see text] 7 TeV with the ALICE detector at the LHC. Transverse momentum spectra for inelastic collisions are compared to QCD-inspired models, which in general underpredict the data. A search for the [Formula: see text] pentaquark, decaying in the [Formula: see text] channel, has been carried out but no evidence is seen.
        Cover page: Production of Σ(1385)± and Ξ(1530)0 in proton–proton collisions at s= 7 TeV
        • Article
        • Peer Reviewed
        UC Berkeley Previously Published Works (2014)
        The inclusive production cross sections at forward rapidity of [Formula: see text], [Formula: see text], [Formula: see text](1S) and [Formula: see text](2S) are measured in [Formula: see text] collisions at [Formula: see text] with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.35 pb[Formula: see text]. Quarkonia are reconstructed in the dimuon-decay channel and the signal yields are evaluated by fitting the [Formula: see text] invariant mass distributions. The differential production cross sections are measured as a function of the transverse momentum [Formula: see text] and rapidity [Formula: see text], over the ranges [Formula: see text] GeV/c for [Formula: see text], [Formula: see text] GeV/c for all other resonances and for [Formula: see text]. The measured cross sections integrated over [Formula: see text] and [Formula: see text], and assuming unpolarized quarkonia, are: [Formula: see text] [Formula: see text]b, [Formula: see text] [Formula: see text]b, [Formula: see text] nb and [Formula: see text] 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.
          Cover page: Measurement of quarkonium production at forward rapidity in pp collisions at s=7TeV
          • Article
          • Peer Reviewed
          UC Berkeley Previously Published Works (2013)
          The ALICE Collaboration at the LHC has measured the J/ψ and ψ' photoproduction at mid-rapidity in ultra-peripheral Pb-Pb collisions at [Formula: see text]. 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 μb-1. The cross section for coherent and incoherent J/ψ production in the rapidity interval -0.9<y<0.9, are [Formula: see text] and [Formula: see text], respectively. The results are compared to theoretical models for J/ψ production and the coherent cross section is found to be in good agreement with those models incorporating moderate nuclear gluon shadowing at Bjorken-x around 10-3, such as EPS09 parametrization. In addition the cross section for the process γγ→e+e- has been measured and found to be in agreement with models implementing QED at leading order.
            Cover page: Charmonium and e+e− pair photoproduction at mid-rapidity in ultra-peripheral Pb–Pb collisions at
            • Article
            • Peer Reviewed
            UC Berkeley Previously Published Works (2015)
            The multiplicity and pseudorapidity distributions of inclusive photons have been measured at forward rapidities (2.3 < η < 3.9) in proton–proton collisions at three center-of-mass energies, √s = 0.9, 2.76 and 7 TeV using the ALICE detector. It is observed that the increase in the average photon multiplicity as a function of beam energy is compatible with both a logarithmic and a power-law dependence. The relative increase in average photon multiplicity produced in inelastic pp collisions at 2.76 and 7 TeV center-of-mass energies with respect to 0.9 TeV are 37.2± 0.3% (stat) ± 8.8% (sys) and 61.2 ± 0.3 % (stat) ± 7.6% (sys), respectively. The photon multiplicity distributions for all center-of-mass energies are well described by negative binomial distributions. The multiplicity distributions are also presented in terms of KNO variables. The results are compared to model predictions, which are found in general to underestimate the data at large photon multiplicities, in particular at the highest center-of-mass energy. Limiting fragmentation behavior of photons has been explored with the data, but is not observed in the measured pseudorapidity range.
              Cover page: Inclusive photon production at forward rapidities in proton–proton collisions at s = 0.9, 2.76 and 7 TeV
              • Article
              • Peer Reviewed
              UC Berkeley Previously Published Works (2014)
              The transverse momentum (Formula presented.) distribution of primary charged particles is measured at midrapidity in minimum-bias p–Pb collisions at (Formula presented.)NN = 5.02(Formula presented.) TeV with the ALICE detector at the LHC in the range. 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 (Formula presented.) larger than 2 GeV/(Formula presented.)(Formula presented.) around 4 (Formula presented.). The measurement is compared to theoretical calculations and to data in Pb–Pb collisions at (Formula presented.) TeV.
                Cover page: Transverse momentum dependence of inclusive primary charged-particle production in p–Pb collisions at sNN=5.02TeV
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