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Light vector meson production in pp collisions at s=7 TeV
ALICE Collaboration,Abelev, B.,Abrahantes Quintana, A.,Adamova, D.,Adare, A.M.,Aggarwal, M.M.,Aglieri Rinella, G.,Agocs, A.G.,Agostinelli, A.,Aguilar Salazar, S.,Ahammed, Z.,Ahmad, N.,Ahmad Masoodi, A North-Holland Pub. Co 2012 Physics letters: B Vol.710 No.4
<P>The ALICE experiment has measured low-mass dimuon production in pp collisions at root s = 7 TeV in the dimuon rapidity region 2.5 < y < 4. The observed dimuon mass spectrum is described as a superposition of resonance decays (eta, rho, omega, eta', phi) into muons and semi-leptonic decays of charmed mesons. The measured production cross sections for omega and phi are sigma(omega)(1 < p(t) < 5 GeV/c. 2.5 < y < 4) = 5.28 +/- 0.54(stat) +/- 0.49(syst) mb and sigma(phi)(1 < p(t) < 5 GeV/c. 2.5 < y < 4) = 0.940 +/- 0.084(stat) +/- 0.076(syst) mb. The differential cross sections d(2)sigma/dy dp(t) are extracted as a function of p(t) for omega and phi. The ratio between the rho and omega cross section is obtained. Results for the phi are compared with other measurements at the same energy and with predictions by models. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.</P>
Neutral pion and η meson production in proton-proton collisions at s=0.9 TeV and s=7 TeV
ALICE Collaboration,Abelev, B.,Abrahantes Quintana, A.,Adamova, D.,Adare, A.M.,Aggarwal, M.M.,Aglieri Rinella, G.,Agocs, A.G.,Agostinelli, A.,Aguilar Salazar, S.,Ahammed, Z.,Ahmad, N.,Ahmad Masoodi, A North-Holland Pub. Co 2012 Physics letters. Section B Vol.717 No.1
The first measurements of the invariant differential cross sections of inclusive π<SUP>0</SUP> and η meson production at mid-rapidity in proton-proton collisions at s=0.9 TeV and s=7 TeV are reported. The π<SUP>0</SUP> measurement covers the ranges 0.4<p<SUB>T</SUB><7 GeV/c and 0.3<p<SUB>T</SUB><25 GeV/c for these two energies, respectively. The production of η mesons was measured at s=7 TeV in the range 0.4<p<SUB>T</SUB><15 GeV/c. Next-to-Leading Order perturbative QCD calculations, which are consistent with the π<SUP>0</SUP> spectrum at s=0.9 TeV, overestimate those of π<SUP>0</SUP> and η mesons at s=7 TeV, but agree with the measured η/π<SUP>0</SUP> ratio at s=7 TeV.
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at s<sub>NN</sub>=2.76 TeV
ALICE Collaboration,Aamodt, K.,Abrahantes Quintana, A.,Adamova, D.,Adare, A.M.,Aggarwal, M.M.,Aglieri Rinella, G.,Agocs, A.G.,Aguilar Salazar, S.,Ahammed, Z.,Ahmad, N.,Ahmad Masoodi, A.,Ahn, S.U.,Akin North-Holland Pub. Co 2011 Physics letters: B Vol.696 No.4
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb collisions at s<SUB>NN</SUB>=2.76 TeV at the Large Hadron Collider is presented. We observe a growing trend with energy now not only for the longitudinal and the outward but also for the sideward pion source radius. The pion homogeneity volume and the decoupling time are significantly larger than those measured at RHIC.
ALICE Collaboration,Aamodt, K.,Abelev, B.,Abrahantes Quintana, A.,Adamova, D.,Adare, A.M.,Aggarwal, M.M.,Aglieri Rinella, G.,Agocs, A.G.,Agostinelli, A.,Aguilar Salazar, S.,Ahammed, Z.,Ahmad, N.,Ahmad North-Holland Pub. Co 2012 Physics letters: B Vol.708 No.3
Angular correlations between unidentified charged trigger (t) and associated (a) particles are measured by the ALICE experiment in Pb-Pb collisions at s<SUB>NN</SUB>=2.76 TeV for transverse momenta 0.25<p<SUB>T</SUB><SUP>t,a</SUP><15 GeV/c, where p<SUB>T</SUB><SUP>t</SUP>>p<SUB>T</SUB><SUP>a</SUP>. The shapes of the pair correlation distributions are studied in a variety of collision centrality classes between 0 and 50% of the total hadronic cross section for particles in the pseudorapidity interval |η|<1.0. Distributions in relative azimuth Δφ=φ<SUP>t</SUP>-φ<SUP>a</SUP> are analyzed for |Δη|=|η<SUP>t</SUP>-η<SUP>a</SUP>|>0.8, and are referred to as ''long-range correlations''. Fourier components V<SUB>nΔ</SUB>≤cos(nΔφ)> are extracted from the long-range azimuthal correlation functions. If particle pairs are correlated to one another through their individual correlation to a common symmetry plane, then the pair anisotropy V<SUB>nΔ</SUB>(p<SUB>T</SUB><SUP>t</SUP>,p<SUB>T</SUB><SUP>a</SUP>) is fully described in terms of single-particle anisotropies v<SUB>n</SUB>(p<SUB>T</SUB>) as V<SUB>nΔ</SUB>(p<SUB>T</SUB><SUP>t</SUP>,p<SUB>T</SUB><SUP>a</SUP>)=v<SUB>n</SUB>(p<SUB>T</SUB><SUP>t</SUP>)v<SUB>n</SUB>(p<SUB>T</SUB><SUP>a</SUP>). This expectation is tested for 1≤n≤5 by applying a global fit of all V<SUB>nΔ</SUB>(p<SUB>T</SUB><SUP>t</SUP>,p<SUB>T</SUB><SUP>a</SUP>) to obtain the best values v<SUB>n</SUB>{GF}(p<SUB>T</SUB>). It is found that for 2≤n≤5, the fit agrees well with data up to p<SUB>T</SUB><SUP>a</SUP>~3-4 GeV/c, with a trend of increasing deviation as p<SUB>T</SUB><SUP>t</SUP> and p<SUB>T</SUB><SUP>a</SUP> are increased or as collisions become more peripheral. This suggests that no pair correlation harmonic can be described over the full 0.25<p<SUB>T</SUB><15 GeV/c range using a single v<SUB>n</SUB>(p<SUB>T</SUB>) curve; such a description is however approximately possible for 2≤n≤5 when p<SUB>T</SUB><SUP>a</SUP><4 GeV/c. For the n=1 harmonic, however, a single v<SUB>1</SUB>(p<SUB>T</SUB>) curve is not obtained even within the reduced range p<SUB>T</SUB><SUP>a</SUP><4 GeV/c.