Strangeness with ALICE: from pp to Pb-Pb

We present the measurements of strange and multi-strange hadrons in high energy pp and Pb-Pb collisions at the Large Hadron Collider (LHC) at CERN. The data for these measurements were collected by the ALICE detector in 2010 and 2011. By comparing strangeness data where Quark-Gluon Plasma (QGP) is not expected to be produced (pp collisions) with data where the energy-density of the collision is sufficient to produce the QGP (central and mid-central Pb-Pb collisions), we are able to investigate the properties of the QGP. We characterize the matter created in the collision by presenting strange and multi-strange particle spectra, yields, and transverse momenta in the context of increasing strangeness number, varying collision energy, and the number of nucleons participating in the collision (Npart).Comment: This is a proceedings for the Physics of the LHC 2012 Conference, held in Vancouver, B

Measurement of electrons from beauty hadron decays in pp collisions at root s=7 TeV

The production cross section of electrons from semileptonic decays of beauty hadrons was measured at mid-rapidity (vertical bar y vertical bar LT 0.8) in, the transverse momentum range 1 LT p(T) LT 8 GeV/c with the ALICE experiment at the CERN LHC in pp collisions at a center of mass energy root s = 7 TeV using an integrated luminosity of 2.2 nb(-1). Electrons from beauty hadron decays were selected based on the displacement of the decay vertex from the collision vertex. A perturbative QCD calculation agrees with the measurement within uncertainties. The data were extrapolated to the full phase space to determine the total cross section for the production of beauty quark-antiquark pairs. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved

Suppression of high transverse momentum D mesons in central Pb-Pb collisions at root s(NN)=2.76 TeV

The production of the prompt charm mesons D-0, D+, D*(+), and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at the LHC, at a centre-of-mass energy root s(NN) = 2.76 TeV per nucleon-nucleon collision. The p(t)-differential production yields in the range 2 LT p(t) LT 16 GeV/c at central rapidity, vertical bar y vertical bar LT 0.5, were used to calculate the nuclear modification factor R-AA with respect to a proton-proton reference obtained from the cross section measured at root s = 7 TeV and scaled to root s = 2.76 TeV. For the three meson species, R-AA shows a suppression by a factor 3-4, for transverse momenta larger than 5 GeV/c in the 20% most central collisions. The suppression is reduced for peripheral collisions

Exclusive J/psi Photoproduction off Protons in Ultraperipheral p-Pb Collisions at root s(NN)=5.02 TeV

We present the first measurement at the LHC of exclusive J/psi photoproduction off protons, in ultraperipheral proton-lead collisions at root s(NN) = 5.02 TeV. Events are selected with a dimuon pair produced either in the rapidity interval, in the laboratory frame, 2.5 LT y LT 4 (p-Pb) or -3.6 LT y LT -2.6 (Pb-p), and no other particles observed in the ALICE acceptance. The measured cross sections sigma(gamma + p - GT J/psi + p) are 33.2 +/- 2.2(stat) +/- 3.2(syst) +/- 0.7(theor) nb in p-Pb and 284 +/- 36(stat)(-32)(+27)(syst) +/- 26(theor) nb in Pb-p collisions. We measure this process up to about 700 GeV in the gamma p center of mass, which is a factor of two larger than the highest energy studied at HERA. The data are consistent with a power law dependence of the J/psi photoproduction cross section in gamma p energies from about 20 to 700 GeV, or equivalently, from Bjorken x scaling variable between similar to 2 x 10(-2) and similar to 2 x 10(-5), thus indicating no significant change in the gluon density behavior of the proton between HERA and LHC energies

Measurement of Prompt D-Meson Production in p-Pb Collisions at root s(NN)=5.02 TeV

The p(T)-differential production cross sections of the prompt charmed mesons D-0, D+, D*(-), and D-s(+) and their charge conjugate in the rapidity interval -0.96 LT y(cms) LT 0.04 were measured in p-Pb collisions at a center-of-mass energy root s(NN) = 5.02 TeV with the ALICE detector at the LHC. The nuclear modification factor R-pPb, quantifying the D-meson yield in p-Pb collisions relative to the yield in pp collisions scaled by the number of binary nucleon-nucleon collisions, is compatible within the 15%-20% uncertainties with unity in the transverse momentum interval 1 LT p(T) LT 24 GeV/c. No significant difference among the R-pPb of the four D-meson species is observed. The results are described within uncertainties by theoretical calculations that include initial-state effects. The measurement adds experimental evidence that the modification of the momentum spectrum of D mesons observed in Pb-Pb collisions with respect to pp collisions is due to strong final-state effects induced by hot partonic matter

Two- and three-pion quantum statistics correlations in Pb-Pb collisions at root S-NN=2.76 TeV at the CERN Large Hadron Collider

Correlations induced by quantum statistics are sensitive to the spatiotemporal extent as well as dynamics of particle-emitting sources in heavy-ion collisions. In addition, such correlations can be used to search for the presence of a coherent component of pion production. Two- and three-pion correlations of same and mixed charge are measured at low relative momentum to estimate the coherent fraction of charged pions in Pb-Pb collisions at root S-NN = 2.76 TeV at the CERN Large Hadron Collider with ALICE. The genuine three-pion quantum statistics correlation is found to be suppressed relative to the two-pion correlation based on the assumption of fully chaotic pion emission. The suppression is observed to decrease with triplet momentum. The observed suppression at low triplet momentum may correspond to a coherent fraction in charged-pion emission of 23% +/- 8%

Production of Sigma (1385)(+/-) and Xi (1530)(0) in proton-proton collisions at root s=7 TeV

The production of the strange and double-strange baryon resonances (Sigma (1385)(+/-), Xi (1530)(0)) has been measured at mid-rapidity (vertical bar y vertical bar LT 0.5) in proton-proton collisions at root s = 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 phi (1860) pentaquark, decaying in the Xi pi channel, has been carried out but no evidence is seen