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Production of [FORMULA OMISSION] and [FORMULA OMISSION] in p–Pb collisions at [FORMULA OMISSION] TeV
Adamová,, D.,Aggarwal, M. M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahmad, S.,Ahn, S. U.,Aiola, S.,Akindinov, A.,Alam, S. N.,Albuquerque, D. S. D.,Aleksandrov, D.,Alessandro, B. Springer 2017 European Physical Journal C Vol.77 No.6
<P>The transverse momentum distributions of the strange and double-strange hyperon resonances ([FORMULA OMISSION], [FORMULA OMISSION]) produced in p–Pb collisions at [FORMULA OMISSION] TeV were measured in the rapidity range [FORMULA OMISSION] for event classes corresponding to different charged-particle multiplicity densities, [FORMULA OMISSION]d[FORMULA OMISSION]/d[FORMULA OMISSION]. The mean transverse momentum values are presented as a function of [FORMULA OMISSION]d[FORMULA OMISSION]/d[FORMULA OMISSION], as well as a function of the particle masses and compared with previous results on hyperon production. The integrated yield ratios of excited to ground-state hyperons are constant as a function of [FORMULA OMISSION]d[FORMULA OMISSION]/d[FORMULA OMISSION]. The equivalent ratios to pions exhibit an increase with [FORMULA OMISSION]d[FORMULA OMISSION]/d[FORMULA OMISSION], depending on their strangeness content.</P>
Adamová,, D.,Aggarwal, M.M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahmad, N.,Ahn, S.U.,Aiola, S.,Akindinov, A.,Alam, S.N.,Albuquerque, D.S.D.,Aleksandrov, D.,Alessandro, B.,Alex North-Holland Pub. Co 2018 Physics letters. Section B Vol.776 No.-
<P><B>Abstract</B></P> <P>We report measurements of the inclusive J/<I>ψ</I> yield and average transverse momentum as a function of charged-particle pseudorapidity density d <SUB> N ch </SUB> / d η in p–Pb collisions at <SUB> s NN </SUB> = 5.02 TeV with ALICE at the LHC. The observables are normalised to their corresponding averages in non-single diffractive events. An increase of the normalised J/<I>ψ</I> yield with normalised d <SUB> N ch </SUB> / d η , measured at mid-rapidity, is observed at mid-rapidity and backward rapidity. At forward rapidity, a saturation of the relative yield is observed for high charged-particle multiplicities. The normalised average transverse momentum at forward and backward rapidities increases with multiplicity at low multiplicities and saturates beyond moderate multiplicities. In addition, the forward-to-backward nuclear modification factor ratio is also reported, showing an increasing suppression of J/<I>ψ</I> production at forward rapidity with respect to backward rapidity for increasing charged-particle multiplicity.</P>
Measurement of an Excess in the Yield ofJ/ψat Very LowpTin Pb-Pb Collisions atsNN=2.76 TeV
Adam, J.,Adamová,, D.,Aggarwal, M. M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahn, S. U.,Aiola, S.,Akindinov, A.,Alam, S. N.,Aleksandrov, D.,Alessandro, B.,Alexandre, D.,Alfaro M American Physical Society 2016 Physical review letters Vol.116 No.22
<P>We report on the first measurement of an excess in the yield of J/psi at very low transverse momentum (pT < 0.3 GeV/c) in peripheral hadronic Pb-Pb collisions at root s(NN) = 2.76 TeV, performed by ALICE at the CERN LHC. Remarkably, the measured nuclear modification factor of J/psi in the rapidity range 2.5 < y < 4 reaches about 7 (2) in the p(T) range 0-0.3 GeV/c in the 70%-90% (50%-70%) centrality class. The J/psi production cross section associated with the observed excess is obtained under the hypothesis that coherent photoproduction of J/psi is the underlying physics mechanism. If confirmed, the observation of J/psi coherent photoproduction in Pb-Pb collisions at impact parameters smaller than twice the nuclear radius opens new theoretical and experimental challenges and opportunities. In particular, coherent photoproduction accompanying hadronic collisions may provide insight into the dynamics of photoproduction and nuclear reactions, as well as become a novel probe of the quark-gluon plasma.</P>
Flow Dominance and Factorization of Transverse Momentum Correlations in Pb-Pb Collisions at the LHC
Adam, J.,Adamová,, D.,Aggarwal, M. M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahmad, S.,Ahn, S. U.,Aiola, S.,Akindinov, A.,Alam, S. N.,Albuquerque, D. S. D.,Aleksandrov, D.,Aless American Physical Society 2017 Physical review letters Vol.118 No.16
<P>We present the first measurement of the two-particle transverse momentum differential correlation function, P-2 = <Delta pT Delta p(T)>/ < p(T)>(2), in Pb-Pb collisions at root s(NN) = 2.76 TeV. Results for P-2 are reported as a function of the relative pseudorapidity (Delta eta) and azimuthal angle (Delta phi) between two particles for different collision centralities. The Delta phi dependence is found to be largely independent of Delta eta for broken vertical bar Delta eta broken vertical bar >= 0.9. In the 5% most central Pb-Pb collisions, the two-particle transverse momentum correlation function exhibits a clear double-hump structure around Delta phi=pi (i. e., on the away side), which is not observed in number correlations in the same centrality range, and thus provides an indication of the dominance of triangular flow in this collision centrality. Fourier decompositions of P-2, studied as a function of the collision centrality, show that correlations at broken vertical bar Delta eta broken vertical bar >= 0.9 can be well reproduced by a flow ansatz based on the notion that measured transverse momentum correlations are strictly determined by the collective motion of the system.</P>
Acharya, S.,Adam, J.,Adamová,, D.,Adolfsson, J.,Aggarwal, M.M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahmad, N.,Ahn, S.U.,Aiola, S.,Akindinov, A.,Al-Turany, M.,Alam, S.N.,Alba, Elsevier 2018 Physics letters: B Vol.781 No.-
<P><B>Abstract</B></P> <P>First results on the longitudinal asymmetry and its effect on the pseudorapidity distributions in Pb–Pb collisions at <SUB> s NN </SUB> = 2.76 TeV at the Large Hadron Collider are obtained with the ALICE detector. The longitudinal asymmetry arises because of an unequal number of participating nucleons from the two colliding nuclei, and is estimated for each event by measuring the energy in the forward neutron-Zero-Degree-Calorimeters (ZNs). The effect of the longitudinal asymmetry is measured on the pseudorapidity distributions of charged particles in the regions | η | < 0.9 , 2.8 < η < 5.1 and − 3.7 < η < − 1.7 by taking the ratio of the pseudorapidity distributions from events corresponding to different regions of asymmetry. The coefficients of a polynomial fit to the ratio characterise the effect of the asymmetry. A Monte Carlo simulation using a Glauber model for the colliding nuclei is tuned to reproduce the spectrum in the ZNs and provides a relation between the measurable longitudinal asymmetry and the shift in the rapidity ( <SUB> y 0 </SUB> ) of the participant zone formed by the unequal number of participating nucleons. The dependence of the coefficient of the linear term in the polynomial expansion, <SUB> c 1 </SUB> , on the mean value of <SUB> y 0 </SUB> is investigated.</P>
Abelev, B.,Adam, J.,Adamová,, D.,Aggarwal, M. M.,Rinella, G. Aglieri,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 Springer Berlin Heidelberg 2015 European Physical Journal C Vol.75 No.1
<P>The production of the strange and double-strange baryon resonances ([FORMULA OMISSION], [FORMULA OMISSION]) has been measured at mid-rapidity ([FORMULA OMISSION][FORMULA OMISSION]) in proton–proton collisions at [FORMULA OMISSION] [FORMULA OMISSION] 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 OMISSION] pentaquark, decaying in the [FORMULA OMISSION] channel, has been carried out but no evidence is seen.</P>
Acharya, S.,Adamová,, D.,Adolfsson, J.,Aggarwal, M.M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahn, S.U.,Aiola, S.,Akindinov, A.,Al-Turany, M.,Alam, S.N.,Albuquerque, D.S.D.,Aleks North-Holland Pub. Co 2018 Physics letters. Section B Vol.783 No.-
<P><B>Abstract</B></P> <P>The ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high-transverse momentum trigger hadron in p–Pb collisions at <SUB> s NN </SUB> = 5.02 TeV. Jets are reconstructed from charged-particle tracks using the anti- <SUB> k T </SUB> algorithm with resolution parameter R = 0.2 and 0.4. A data-driven statistical approach is used to correct the uncorrelated background jet yield. Recoil jet distributions are reported for jet transverse momentum 15 < p T , jet ch < 50 GeV / c and are compared in various intervals of p–Pb event activity, based on charged-particle multiplicity and zero-degree neutral energy in the forward (Pb-going) direction. The semi-inclusive observable is self-normalized and such comparisons do not require the interpretation of p–Pb event activity in terms of collision geometry, in contrast to inclusive jet observables. These measurements provide new constraints on the magnitude of jet quenching in small systems at the LHC. In p–Pb collisions with high event activity, the average medium-induced out-of-cone energy transport for jets with R = 0.4 and 15 < p T , jet ch < 50 GeV / c is measured to be less than 0.4 GeV / c at 90% confidence, which is over an order of magnitude smaller than a similar measurement for central Pb–Pb collisions at <SUB> s NN </SUB> = 2.76 TeV . Comparison is made to theoretical calculations of jet quenching in small systems, and to inclusive jet measurements in p–Pb collisions selected by event activity at the LHC and in d–Au collisions at RHIC.</P>
Anomalous Evolution of the Near-Side Jet Peak Shape in Pb-Pb Collisions at sNN=2.76 TeV
Adam, J.,Adamová,, D.,Aggarwal, M. M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahmad, S.,Ahn, S. U.,Aiola, S.,Akindinov, A.,Alam, S. N.,Albuquerque, D. S. D.,Aleksandrov, D.,Aless American Physical Society 2017 Physical review letters Vol.119 No.10
<P>The measurement of two-particle angular correlations is a powerful tool to study jet quenching in a p(T) region inaccessible by direct jet identification. In these measurements pseudorapidity (Delta(eta)) and azimuthal (Delta phi) differences are used to extract the shape of the near-side peak formed by particles associated with a higher p(T) trigger particle (1 < p(T,trig) < 8 GeV/c). A combined fit of the near-side peak and long-range correlations is applied to the data allowing the extraction of the centrality evolution of the peak shape in Pb-Pb collisions at root s(NN) = 2.76 TeV. A significant broadening of the peak in the Delta(eta) direction at low p(T) is found from peripheral to central collisions, which vanishes above 4 GeV/c, while in the Delta(phi) direction the peak is almost independent of centrality. For the 10% most central collisions and 1 < p(T,assoc) < 2 GeV/c, 1 < p(T,trig) < 3 GeV/c a novel feature is observed: a depletion develops around the center of the peak. The results are compared to pp collisions at the same center of mass energy and AMPT model simulations. The comparison to the investigated models suggests that the broadening and the development of the depletion is connected to the strength of radial and longitudinal flow.</P>
Inclusive quarkonium production at forward rapidity in pp collisions at [FORMULA OMISSION] TeV
Adam, J.,Adamová,, D.,Aggarwal, M. M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahn, S. U.,Aiola, S.,Akindinov, A.,Alam, S. N.,Aleksandrov, D.,Alessandro, B.,Alexandre, D.,Alfaro M Springer Berlin Heidelberg 2016 The European physical journal. C, Particles and fi Vol.76 No.4
<P>We report on the inclusive production cross sections of [FORMULA OMISSION], [FORMULA OMISSION], [FORMULA OMISSION](1S), [FORMULA OMISSION](2S) and [FORMULA OMISSION](3S), measured at forward rapidity with the ALICE detector in [FORMULA OMISSION] collisions at a center-of-mass energy [FORMULA OMISSION] TeV. The analysis is based on data collected at the LHC and corresponds to an integrated luminosity of 1.23 pb[FORMULA OMISSION]. Quarkonia are reconstructed in the dimuon-decay channel. The differential production cross sections are measured as a function of the transverse momentum [FORMULA OMISSION] and rapidity <I>y</I>, over the [FORMULA OMISSION] ranges [FORMULA OMISSION] GeV/<I>c</I> for [FORMULA OMISSION], [FORMULA OMISSION] GeV/<I>c</I> for all other resonances, and for [FORMULA OMISSION]. The cross sections, integrated over [FORMULA OMISSION] and <I>y</I>, and assuming unpolarized quarkonia, are [FORMULA OMISSION] [FORMULA OMISSION]b, [FORMULA OMISSION] [FORMULA OMISSION]b, [FORMULA OMISSION] nb, [FORMULA OMISSION] nb and [FORMULA OMISSION] nb, where the first uncertainty is statistical and the second one is systematic. These values agree, within at most [FORMULA OMISSION], with measurements performed by the LHCb collaboration in the same rapidity range.</P>
Adam, J.,Adamová,, D.,Aggarwal, M.M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahmad, S.,Ahn, S.U.,Aiola, S.,Akindinov, A.,Alam, S.N.,Albuquerque, D.S.D.,Aleksandrov, D.,Alessandro North-Holland Pub. Co 2017 Physics letters. Section B Vol.771 No.-
<P><B>Abstract</B></P> <P>Electrons from heavy-flavour hadron decays (charm and beauty) were measured with the ALICE detector in Pb–Pb collisions at a centre-of-mass of energy <SUB> s NN </SUB> = 2.76 TeV . The transverse momentum ( <SUB> p T </SUB> ) differential production yields at mid-rapidity were used to calculate the nuclear modification factor <SUB> R AA </SUB> in the interval 3 < <SUB> p T </SUB> < 18 GeV/<I>c</I>. The <SUB> R AA </SUB> shows a strong suppression compared to binary scaling of pp collisions at the same energy (up to a factor of 4) in the 10% most central Pb–Pb collisions. There is a centrality trend of suppression, and a weaker suppression (down to a factor of 2) in semi-peripheral (50–80%) collisions is observed. The suppression of electrons in this broad <SUB> p T </SUB> interval indicates that both charm and beauty quarks lose energy when they traverse the hot medium formed in Pb–Pb collisions at LHC.</P>