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Measurement of electrons from semileptonic heavy-flavor hadron decays inppcollisions ats=2.76 TeV
Abelev, B.,Adam, J.,Adamová,, D.,Aggarwal, M. M.,Agnello, M.,Agostinelli, A.,Agrawal, N.,Ahammed, Z.,Ahmad, N.,Ahmed, I.,Ahn, S. U.,Ahn, S. A.,Aimo, I.,Aiola, S.,Ajaz, M.,Akindinov, A.,Alam, S. American Physical Society 2015 PHYSICAL REVIEW D - Vol.91 No.1
<P>The p(T)-differential production cross section of electrons from semileptonic decays of heavy-flavor hadrons has been measured at midrapidity in proton-proton collisions at root s = 2.76 TeV in the transverse momentum range 0.5 < p(T) < 12 GeV/c with the ALICE detector at the LHC. The analysis was performed using minimum bias events and events triggered by the electromagnetic calorimeter. Predictions from perturbative QCD calculations agree with the data within the theoretical and experimental uncertainties.</P>
Abelev, B.,Adam, J.,Adamová,, D.,Aggarwal, M. M.,Agnello, M.,Agostinelli, A.,Agrawal, N.,Ahammed, Z.,Ahmad, N.,Ahmed, I.,Ahn, S. U.,Ahn, S. A.,Aimo, I.,Aiola, S.,Ajaz, M.,Akindinov, A.,Alam, S. Institute of Physics Pub 2015 The journal of high energy physics Vol.2015 No.6
<P>The elliptic flow coefficient (v(2)) of identified particles in Pb-Pb collisions at root s(NN) = 2.76 TeV was measured with the ALICE detector at the Large Hadron Collider (LHC). The results were obtained with the Scalar Product method, a two-particle correlation technique, using a pseudo-rapidity gap of |Delta eta| > 0.9 between the identified hadron under study and the reference particles. The v (2) is reported for pi(+/-), K-+/-, K-S(0), p+(p) over bar, phi, Lambda+(Lambda) over bar, Xi+(Xi) over bar (+) and Omega(-)+(Omega) over bar (+) in several collision centralities. In the low transverse momentum (p(T)) region, p(T) < 3 GeV/c, v(2)(p(T)) exhibits a particle mass dependence consistent with elliptic flow accompanied by the transverse radial expansion of the system with a common velocity field. The experimental data for pi (+/-) and the combined K-+/- and K-S(0) results, are described fairly well by hydrodynamic calculations coupled to a hadronic cascade model (VISHNU) for central collisions. However, the same calculations fail to reproduce the v(2)(p(T)) for p+(p) over bar, phi, Lambda+(Lambda) over bar, Xi+(Xi) over bar (+). For transverse momentum values larger than about 3 GeV/c, particles tend to group according to their type, i.e. mesons and baryons. The present measurements exhibit deviations from the number of constituent quark (NCQ) scaling at the level of +/- 20% for p(T) > 3 GeV/c.</P>
Freeze-out radii extracted from three-pion cumulants in pp, p–Pb and Pb–Pb collisions at the LHC
Abelev, B.,Adam, J.,Adamová,, D.,Aggarwal, M.M.,Agnello, M.,Agostinelli, A.,Agrawal, N.,Ahammed, Z.,Ahmad, N.,Ahmed, I.,Ahn, S.U.,Ahn, S.A.,Aimo, I.,Aiola, S.,Ajaz, M.,Akindinov, A.,Alam, S.N.,A Elsevier 2014 Physics letters: B Vol.739 No.-
<P><B>Abstract</B></P> <P>In high-energy collisions, the spatio-temporal size of the particle production region can be measured using the Bose–Einstein correlations of identical bosons at low relative momentum. The source radii are typically extracted using two-pion correlations, and characterize the system at the last stage of interaction, called kinetic freeze-out. In low-multiplicity collisions, unlike in high-multiplicity collisions, two-pion correlations are substantially altered by background correlations, e.g. mini-jets. Such correlations can be suppressed using three-pion cumulant correlations. We present the first measurements of the size of the system at freeze-out extracted from three-pion cumulant correlations in pp, p–Pb and Pb–Pb collisions at the LHC with ALICE. At similar multiplicity, the invariant radii extracted in p–Pb collisions are found to be 5–15% larger than those in pp, while those in Pb–Pb are 35–55% larger than those in p–Pb. Our measurements disfavor models which incorporate substantially stronger collective expansion in p–Pb as compared to pp collisions at similar multiplicity.</P>
Suppression of ϒ ( 1 S ) at forward rapidity in Pb–Pb collisions at <sub> s NN </sub> = 2.76 TeV
Abelev, B.,Adam, J.,Adamová,, D.,Aggarwal, M.M.,Agnello, M.,Agostinelli, A.,Agrawal, N.,Ahammed, Z.,Ahmad, N.,Ahmed, I.,Ahn, S.U.,Ahn, S.A.,Aimo, I.,Aiola, S.,Ajaz, M.,Akindinov, A.,Alam, S.N.,A North-Holland Pub. Co 2014 Physics letters. Section B Vol.738 No.-
<P><B>Abstract</B></P> <P>We report on the measurement of the inclusive ϒ ( 1 S ) production in Pb–Pb collisions at <SUB> s NN </SUB> = 2.76 TeV carried out at forward rapidity ( 2.5 < y < 4 ) and down to zero transverse momentum using its <SUP> μ + </SUP> <SUP> μ − </SUP> decay channel with the ALICE detector at the Large Hadron Collider. A strong suppression of the inclusive ϒ ( 1 S ) yield is observed with respect to pp collisions scaled by the number of independent nucleon–nucleon collisions. The nuclear modification factor, for events in the 0–90% centrality range, amounts to 0.30 ± 0.05 (stat) ± 0.04 (syst) . The observed ϒ ( 1 S ) suppression tends to increase with the centrality of the collision and seems more pronounced than in corresponding mid-rapidity measurements. Our results are compared with model calculations, which are found to underestimate the measured suppression and fail to reproduce its rapidity dependence.</P>
Abelev, B.,Adam, J.,Adamová,, D.,Aggarwal, M. M.,Agnello, M.,Agostinelli, A.,Agrawal, N.,Ahammed, Z.,Ahmad, N.,Ahmad Masoodi, A.,Ahmed, I.,Ahn, S. U.,Ahn, S. A.,Aimo, I.,Aiola, S.,Ajaz, M.,Akind Springer Berlin Heidelberg 2014 European Physical Journal C Vol.74 No.8
<P>The inclusive production cross sections at forward rapidity of [FORMULA OMISSION], [FORMULA OMISSION], [FORMULA OMISSION](1S) and [FORMULA OMISSION](2S) are measured in [FORMULA OMISSION] collisions at [FORMULA OMISSION] 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 OMISSION]. Quarkonia are reconstructed in the dimuon-decay channel and the signal yields are evaluated by fitting the [FORMULA OMISSION] invariant mass distributions. The differential production cross sections are measured as a function of the transverse momentum [FORMULA OMISSION] and rapidity [FORMULA OMISSION], over the ranges [FORMULA OMISSION] GeV/c for [FORMULA OMISSION], [FORMULA OMISSION] GeV/c for all other resonances and for [FORMULA OMISSION]. The measured cross sections integrated over [FORMULA OMISSION] and [FORMULA OMISSION], and assuming unpolarized quarkonia, are: [FORMULA OMISSION] [FORMULA OMISSION]b, [FORMULA OMISSION] [FORMULA OMISSION]b, [FORMULA OMISSION] nb and [FORMULA OMISSION] 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.</P>
Suppression of ψ(2S) production in p-Pb collisions at s N N $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV
Abelev, B.,Adam, J.,Adamová,, D.,Aggarwal, M. M.,Agnello, M.,Agostinelli, A.,Agrawal, N.,Ahammed, Z.,Ahmad, N.,Ahmed, I.,Ahn, S. U.,Ahn, S. A.,Aimo, I.,Aiola, S.,Ajaz, M.,Akindinov, A.,Alam, S. Springer-Verlag 2014 Journal of high energy physics Vol.2014 No.12
Abelev, B.,Adam, J.,Adamová,, D.,Adare, A. M.,Aggarwal, M. M.,Aglieri Rinella, G.,Agocs, A. G.,Agostinelli, A.,Aguilar Salazar, S.,Ahammed, Z.,Ahmad Masoodi, A.,Ahmad, N.,Ahn, S. A.,Ahn, S. U.,A Springer Berlin Heidelberg 2013 The European physical journal. C, Particles and fi Vol.73 No.6
<P>Measurements of cross sections of inelastic and diffractive processes in proton–proton collisions at LHC energies were carried out with the ALICE detector. The fractions of diffractive processes in inelastic collisions were determined from a study of gaps in charged particle pseudorapidity distributions: for single diffraction (diffractive mass <I>M</I><SUB><I>X</I></SUB><200 GeV/<I>c</I><SUP>2</SUP>) [FORMULA OMISSION], and [FORMULA OMISSION], respectively at centre-of-mass energies [FORMULA OMISSION]; for double diffraction (for a pseudorapidity gap Δ<I>η</I>>3) <I>σ</I><SUB>DD</SUB>/<I>σ</I><SUB>INEL</SUB>=0.11±0.03,0.12±0.05, and [FORMULA OMISSION], respectively at [FORMULA OMISSION]. To measure the inelastic cross section, beam properties were determined with van der Meer scans, and, using a simulation of diffraction adjusted to data, the following values were obtained: [FORMULA OMISSION] mb at [FORMULA OMISSION] and [FORMULA OMISSION] at [FORMULA OMISSION]. The single- and double-diffractive cross sections were calculated combining relative rates of diffraction with inelastic cross sections. The results are compared to previous measurements at proton–antiproton and proton–proton colliders at lower energies, to measurements by other experiments at the LHC, and to theoretical models.</P>
Measurement of PromptD-Meson Production inp−PbCollisions atsNN=5.02 TeV
Abelev, B.,Adam, J.,Adamová,, D.,Aggarwal, M. M.,Aglieri Rinella, G.,Agnello, M.,Agostinelli, A.,Agrawal, N.,Ahammed, Z.,Ahmad, N.,Ahmed, I.,Ahn, S. U.,Ahn, S. A.,Aimo, I.,Aiola, S.,Ajaz, M.,Aki American Physical Society 2014 Physical Review Letters Vol.113 No.23