| 1. |
- Acharya, S, et al.
(författare)
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Anisotropic flow of identified hadrons in Xe-Xe collisions at √sNN = 5.44 TeV
- 2021
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2021:10
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of elliptic (v2) and triangular (v3) flow coefficients of π±, K±, p+p ¯ , KS0, and Λ+Λ ¯ obtained with the scalar product method in Xe-Xe collisions at sNN = 5.44 TeV are presented. The results are obtained in the rapidity range |y| < 0.5 and reported as a function of transverse momentum, pT, for several collision centrality classes. The flow coefficients exhibit a particle mass dependence for pT< 3 GeV/c, while a grouping according to particle type (i.e., meson and baryon) is found at intermediate transverse momenta (3 < pT< 8 GeV/c). The magnitude of the baryon v2 is larger than that of mesons up to pT = 6 GeV/c. The centrality dependence of the shape evolution of the pT-differential v2 is studied for the various hadron species. The v2 coefficients of π±, K±, and p+p ¯ are reproduced by MUSIC hydrodynamic calculations coupled to a hadronic cascade model (UrQMD) for pT< 1 GeV/c. A comparison with vn measurements in the corresponding centrality intervals in Pb-Pb collisions at sNN = 5.02 TeV yields an enhanced v2 in central collisions and diminished value in semicentral collisions. [Figure not available: see fulltext.] © 2021, The Author(s).
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| 2. |
- Acharya, S, et al.
(författare)
-
(Anti-)deuteron production in pp collisions at √s=13TeV
- 2020
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:9
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Tidskriftsartikel (refereegranskat)abstract
- The study of (anti-)deuteron production in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper the production of (anti-)deuterons is studied as a function of the charged particle multiplicity in inelastic pp collisions at s=13 TeV using the ALICE experiment. Thanks to the large number of accumulated minimum bias events, it has been possible to measure (anti-)deuteron production in pp collisions up to the same charged particle multiplicity (d Nch/ d η∼ 26) as measured in p–Pb collisions at similar centre-of-mass energies. Within the uncertainties, the deuteron yield in pp collisions resembles the one in p–Pb interactions, suggesting a common formation mechanism behind the production of light nuclei in hadronic interactions. In this context the measurements are compared with the expectations of coalescence and statistical hadronisation models (SHM). © 2020, The Author(s).
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| 3. |
- Acharya, S, et al.
(författare)
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Azimuthal correlations of prompt D mesons with charged particles in pp and p–Pb collisions at √sNN=5.02TeV
- 2020
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:10
-
Tidskriftsartikel (refereegranskat)abstract
- The measurement of the azimuthal-correlation function of prompt D mesons with charged particles in pp collisions at s=5.02TeV and p–Pb collisions at sNN=5.02TeV with the ALICE detector at the LHC is reported. The D , D +, and D ∗ + mesons, together with their charge conjugates, were reconstructed at midrapidity in the transverse momentum interval 30.3GeV/c and pseudorapidity | η| < 0.8. The properties of the correlation peaks appearing in the near- and away-side regions (for Δ φ≈ 0 and Δ φ≈ π, respectively) were extracted via a fit to the azimuthal correlation functions. The shape of the correlation functions and the near- and away-side peak features are found to be consistent in pp and p–Pb collisions, showing no modifications due to nuclear effects within uncertainties. The results are compared with predictions from Monte Carlo simulations performed with the PYTHIA, POWHEG+PYTHIA, HERWIG, and EPOS 3 event generators. © 2020, The Author(s).
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| 4. |
- Acharya, S, et al.
(författare)
-
Centrality dependence of J/ψ and ψ(2S) production and nuclear modification in p-Pb collisions at √sNN = 8.16 TeV
- 2021
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2021
-
Tidskriftsartikel (refereegranskat)abstract
- The inclusive production of the J/ψ and ψ(2S) charmonium states is studied as a function of centrality in p-Pb collisions at a centre-of-mass energy per nucleon pair sNN = 8.16 TeV at the LHC. The measurement is performed in the dimuon decay channel with the ALICE apparatus in the centre-of-mass rapidity intervals −4.46 < ycms< −2.96 (Pb-going direction) and 2.03 < ycms< 3.53 (p-going direction), down to zero transverse momentum (pT). The J/ψ and ψ(2S) production cross sections are evaluated as a function of the collision centrality, estimated through the energy deposited in the zero degree calorimeter located in the Pb-going direction. The pT-differential J/ψ production cross section is measured at backward and forward rapidity for several centrality classes, together with the corresponding average 〈pT〉 and 〈pT2〉 values. The nuclear effects affecting the production of both charmonium states are studied using the nuclear modification factor. In the p-going direction, a suppression of the production of both charmonium states is observed, which seems to increase from peripheral to central collisions. In the Pb-going direction, however, the centrality dependence is different for the two states: the nuclear modification factor of the J/ψ increases from below unity in peripheral collisions to above unity in central collisions, while for the ψ(2S) it stays below or consistent with unity for all centralities with no significant centrality dependence. The results are compared with measurements in p-Pb collisions at sNN = 5.02 TeV and no significant dependence on the energy of the collision is observed. Finally, the results are compared with theoretical models implementing various nuclear matter effects. [Figure not available: see fulltext.] © 2021, The Author(s).
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| 5. |
- Acharya, S, et al.
(författare)
-
Charged-particle multiplicity fluctuations in Pb–Pb collisions at √sNN = 2.76 TeV
- 2021
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6052. ; 81:11
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of event-by-event fluctuations of charged-particle multiplicities in Pb–Pb collisions at sNN = 2.76 TeV using the ALICE detector at the CERN Large Hadron Collider (LHC) are presented in the pseudorapidity range | η| < 0.8 and transverse momentum 0.2 < pT< 2.0 GeV/c. The amplitude of the fluctuations is expressed in terms of the variance normalized by the mean of the multiplicity distribution. The η and pT dependences of the fluctuations and their evolution with respect to collision centrality are investigated. The multiplicity fluctuations tend to decrease from peripheral to central collisions. The results are compared to those obtained from HIJING and AMPT Monte Carlo event generators as well as to experimental data at lower collision energies. Additionally, the measured multiplicity fluctuations are discussed in the context of the isothermal compressibility of the high-density strongly-interacting system formed in central Pb–Pb collisions. © 2021, The Author(s).
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| 6. |
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| 7. |
- Acharya, S, et al.
(författare)
-
Coherent J / ψ and ψ ′ photoproduction at midrapidity in ultra-peripheral Pb–Pb collisions at √sNN=5.02 TeV
- 2021
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 81:8
-
Tidskriftsartikel (refereegranskat)abstract
- The coherent photoproduction of J/ψ and ψ′ mesons was measured in ultra-peripheral Pb–Pb collisions at a center-of-mass energy sNN−−−√ = 5.02 TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The J/ψ is reconstructed using the dilepton (l+l−) and proton–antiproton decay channels, while for the ψ′ the dilepton and the l+l−π+π− decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 μb−1. The results are compared with theoretical models for coherent J/ψ and ψ′ photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.64 at a Bjorken-x of around 6×10−4, such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent J/ψ cross section including ALICE measurements at forward rapidity. The ratio of ψ′ to J/ψ coherent photoproduction cross sections was also measured and found to be consistent with the one for photoproduction off protons.
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| 8. |
- Acharya, S, et al.
(författare)
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Coherent photoproduction of ρ 0 vector mesons in ultra-peripheral Pb-Pb collisions at √sNN = 5.02 TeV
- 2020
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2020:6
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Tidskriftsartikel (refereegranskat)abstract
- Cross sections for the coherent photoproduction of ρ0 vector mesons in ultra-peripheral Pb-Pb collisions at sNN = 5.02 TeV are reported. The measurements, which rely on the π+π− decay channel, are presented in three regions of rapidity covering the range |y| < 0.8. For each rapidity interval, cross sections are shown for different nuclear-breakup classes defined according to the presence of neutrons measured in the zero-degree calorimeters. The results are compared with predictions based on different models of nuclear shadowing. Finally, the observation of a coherently produced resonance-like structure with a mass around 1.7 GeV/c2 and a width of about 140 MeV/c2 is reported and compared with similar observations from other experiments. [Figure not available: see fulltext.] © 2020, The Author(s).
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| 9. |
- Acharya, S, et al.
(författare)
-
Constraining the Chiral Magnetic Effect with charge-dependent azimuthal correlations in Pb-Pb collisions at √sNN = 2.76 and 5.02 TeV
- 2020
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2020:9
-
Tidskriftsartikel (refereegranskat)abstract
- Systematic studies of charge-dependent two- and three-particle correlations in Pb-Pb collisions at sNN = 2.76 and 5.02 TeV used to probe the Chiral Magnetic Effect (CME) are presented. These measurements are performed for charged particles in the pseudorapidity (η) and transverse momentum (pT) ranges |η| < 0.8 and 0.2 < pT< 5 GeV/c. A significant charge-dependent signal that becomes more pronounced for peripheral collisions is reported for the CME-sensitive correlators γ1, 1 = 〈cos(φα + φβ − 2Ψ2)〉 and γ1, − 3 = 〈cos(φα − 3φβ + 2Ψ2)〉. The results are used to estimate the contribution of background effects, associated with local charge conservation coupled to anisotropic flow modulations, to measurements of the CME. A blast-wave parametrisation that incorporates local charge conservation tuned to reproduce the centrality dependent background effects is not able to fully describe the measured γ1,1. Finally, the charge and centrality dependence of mixed-harmonics three-particle correlations, of the form γ1, 2 = 〈cos(φα + 2φβ − 3Ψ3)〉, which are insensitive to the CME signal, verify again that background contributions dominate the measurement of γ1,1.
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| 10. |
- Acharya, S, et al.
(författare)
-
Dielectron production in proton-proton and proton-lead collisions at sNN =5.02 TeV
- 2020
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Ingår i: Physical Review C. - 2469-9985. ; 102:5
-
Tidskriftsartikel (refereegranskat)abstract
- The first measurements of dielectron production at midrapidity (|ηe|<0.8) in proton–proton and proton–lead collisions at √sNN=5.02TeV at the LHC are presented. The dielectron cross section is measured with the ALICE detector as a function of the invariant mass mee and the pair transverse momentum pT,ee in the ranges mee<3.5 GeV/c2 and pT,ee<8 GeV/c, in both collision systems. In proton–proton collisions, the charm and beauty cross sections are determined at midrapidity from a fit to the data with two different event generators. This complements the existing dielectron measurements performed at √s=7 and 13 TeV. The slope of the √s dependence of the three measurements is described by FONLL calculations. The dielectron cross section measured in proton–lead collisions is in agreement, within the current precision, with the expected dielectron production without any nuclear matter effects for e+e− pairs from open heavy-flavor hadron decays. For the first time at LHC energies, the dielectron production in proton–lead and proton–proton collisions are directly compared at the same √sNN via the dielectron nuclear modification factor RpPb. The measurements are compared to model calculations including cold nuclear matter effects, or additional sources of dielectrons from thermal radiation.
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| 11. |
- Acharya, S, et al.
(författare)
-
Elliptic and triangular flow of (anti)deuterons in Pb-Pb collisions at sNN =5.02 TeV
- 2020
-
Ingår i: Physical Review C. - 2469-9985. ; 102:5
-
Tidskriftsartikel (refereegranskat)abstract
- The measurements of the (anti)deuteron elliptic flow (v2) and the first measurements of triangular flow (v3) in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon collision sNN = 5.02 TeV are presented. A mass ordering at low transverse momentum (pT) is observed when comparing these measurements with those of other identified hadrons, as expected from relativistic hydrodynamics. The measured (anti)deuteron v2 lies between the predictions from the simple coalescence and blast-wave models, which provide a good description of the data only for more peripheral and for more central collisions, respectively. The mass number scaling, which is violated for v2, is approximately valid for the (anti)deuterons v3. The measured v2 and v3 are also compared with the predictions from a coalescence approach with phase-space distributions of nucleons generated by iebe-vishnu with ampt initial conditions coupled with urqmd, and from a dynamical model based on relativistic hydrodynamics coupled to the hadronic afterburner smash. The model predictions are consistent with the data within the uncertainties in midcentral collisions, while a deviation is observed in the most central collisions. © 2020 CERN.
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| 12. |
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| 13. |
- Acharya, S, et al.
(författare)
-
Energy dependence of ϕ meson production at forward rapidity in pp collisions at the LHC
- 2021
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 81:8
-
Tidskriftsartikel (refereegranskat)abstract
- The production of ϕ mesons has been studied in pp collisions at LHC energies with the ALICE detector via the dimuon decay channel in the rapidity region 2.5 < y< 4. Measurements of the differential cross section d 2σ/ d yd pT are presented as a function of the transverse momentum (pT) at the center-of-mass energies s=5.02, 8 and 13 TeV and compared with the ALICE results at midrapidity. The differential cross sections at s=5.02 and 13 TeV are also studied in several rapidity intervals as a function of pT, and as a function of rapidity in three pT intervals. A hardening of the pT-differential cross section with the collision energy is observed, while, for a given energy, pT spectra soften with increasing rapidity and, conversely, rapidity distributions get slightly narrower at increasing pT. The new results, complementing the published measurements at s=2.76 and 7 TeV, allow one to establish the energy dependence of ϕ meson production and to compare the measured cross sections with phenomenological models. None of the considered models manages to describe the evolution of the cross section with pT and rapidity at all the energies. © 2021, The Author(s).
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| 14. |
- Acharya, S, et al.
(författare)
-
Evidence of rescattering effect in Pb–Pb collisions at the LHC through production of K(892)0⁎ and ϕ(1020) mesons
- 2020
-
Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 802
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of K(892)0⁎ and ϕ(1020) resonance production in Pb–Pb and pp collisions at sNN = 5.02 TeV with the ALICE detector at the Large Hadron Collider are reported. The resonances are measured at midrapidity (|y| < 0.5) via their hadronic decay channels and the transverse momentum (pT) distributions are obtained for various collision centrality classes up to pT = 20 GeV/c. The pT-integrated yield ratio K(892)0⁎/K in Pb–Pb collisions shows significant suppression relative to pp collisions and decreases towards more central collisions. In contrast, the ϕ(1020)/K ratio does not show any suppression. Furthermore, the measured K(892)0⁎/K ratio in central Pb–Pb collisions is significantly suppressed with respect to the expectations based on a thermal model calculation, while the ϕ(1020)/K ratio agrees with the model prediction. These measurements are an experimental demonstration of rescattering of K(892)0⁎ decay products in the hadronic phase of the collisions. The K(892)0⁎/K yield ratios in Pb–Pb and pp collisions are used to estimate the time duration between chemical and kinetic freeze-out, which is found to be ∼ 4–7 fm/c for central collisions. The pT-differential ratios of K(892)0⁎/K, ϕ(1020)/K, K(892)0⁎/π, ϕ(1020)/π, p/K(892)0⁎ and p/ϕ(1020) are also presented for Pb–Pb and pp collisions at sNN = 5.02 TeV. These ratios show that the rescattering effect is predominantly a low-pT phenomenon.
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| 15. |
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| 16. |
- Acharya, S, et al.
(författare)
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Experimental Evidence for an Attractive p-φ Interaction
- 2021
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Ingår i: Physical Review Letters. - 1079-7114. ; 127:17
-
Tidskriftsartikel (refereegranskat)abstract
- This Letter presents the first experimental evidence of the attractive strong interaction between a proton and a φ meson. The result is obtained from two-particle correlations of combined p-φ p¯-φ pairs measured in high-multiplicity pp collisions at s=13 TeV by the ALICE Collaboration. The spin-averaged scattering length and effective range of the p-φ interaction are extracted from the fully corrected correlation function employing the Lednický-Lyuboshits approach. In particular, the imaginary part of the scattering length vanishes within uncertainties, indicating that inelastic processes do not play a prominent role for the p-φ interaction. These data demonstrate that the interaction is dominated by elastic p-φ scattering. Furthermore, an analysis employing phenomenological Gaussian- and Yukawa-type potentials is conducted. Under the assumption of the latter, the N-φ coupling constant is found to be gN-φ=0.14±0.03(stat)±0.02(syst). This work provides valuable experimental input to accomplish a self-consistent description of the N-φ interaction, which is particularly relevant for the more fundamental studies on partial restoration of chiral symmetry in nuclear medium. © 2021 CERN.
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| 17. |
- Acharya, S, et al.
(författare)
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First measurement of the |t|-dependence of coherent J/ψ photonuclear production
- 2021
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 817
-
Tidskriftsartikel (refereegranskat)abstract
- The first measurement of the cross section for coherent J/ψ photoproduction as a function of |t|, the square of the momentum transferred between the incoming and outgoing target nucleus, is presented. The data were measured with the ALICE detector in ultra-peripheral Pb–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02TeV with the J/ψ produced in the central rapidity region |y|<0.8, which corresponds to the small Bjorken-x range (0.3−1.4)×10−3. The measured |t|-dependence is not described by computations based only on the Pb nuclear form factor, while the photonuclear cross section is better reproduced by models including shadowing according to the leading-twist approximation, or gluon-saturation effects from the impact-parameter dependent Balitsky–Kovchegov equation. These new results are therefore a valid tool to constrain the relevant model parameters and to investigate the transverse gluonic structure at very low Bjorken-x. © 2021 The Author(s)
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| 18. |
- Acharya, S, et al.
(författare)
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First measurements of N-subjettiness in central Pb-Pb collisions at √sNN = 2.76 TeV
- 2021
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2021:9
-
Tidskriftsartikel (refereegranskat)abstract
- The ALICE Collaboration reports the first fully-corrected measurements of the N-subjettiness observable for track-based jets in heavy-ion collisions. This study is performed using data recorded in pp and Pb-Pb collisions at centre-of-mass energies of s = 7 TeV and sNN = 2.76 TeV, respectively. In particular the ratio of 2-subjettiness to 1-subjettiness, τ2/τ1, which is sensitive to the rate of two-pronged jet substructure, is presented. Energy loss of jets traversing the strongly interacting medium in heavy-ion collisions is expected to change the rate of two-pronged substructure relative to vacuum. The results are presented for jets with a resolution parameter of R = 0.4 and charged jet transverse momentum of 40 ≤ pT,jet ≤ 60 GeV/c, which constitute a larger jet resolution and lower jet transverse momentum interval than previous measurements in heavy-ion collisions. This has been achieved by utilising a semi-inclusive hadron-jet coincidence technique to suppress the larger jet combinatorial background in this kinematic region. No significant modification of the τ2/τ1 observable for track-based jets in Pb-Pb collisions is observed relative to vacuum PYTHIA6 and PYTHIA8 references at the same collision energy. The measurements of τ2/τ1, together with the splitting aperture angle ∆R, are also performed in pp collisions at s = 7 TeV for inclusive jets. These results are compared with PYTHIA calculations at s = 7 TeV, in order to validate the model as a vacuum reference for the Pb-Pb centre-of-mass energy. The PYTHIA references for τ2/τ1 are shifted to larger values compared to the measurement in pp collisions. This hints at a reduction in the rate of two-pronged jets in Pb-Pb collisions compared to pp collisions. [Figure not available: see fulltext.] © 2021, The Author(s).
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| 19. |
- Acharya, S., et al.
(författare)
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First study of the two-body scattering involving charm hadrons
- 2022
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Ingår i: Physical Review D. - 2470-0010. ; 106:5
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Tidskriftsartikel (refereegranskat)abstract
- This article presents the first measurement of the interaction between charm hadrons and nucleons. The two-particle momentum correlations of pD- and p¯D+ pairs are measured by the ALICE Collaboration in high-multiplicity pp collisions at s=13 TeV. The data are compatible with the Coulomb-only interaction hypothesis within (1.1-1.5)σ. The level of agreement slightly improves if an attractive nucleon (N)D¯ strong interaction is considered, in contrast to most model predictions which suggest an overall repulsive interaction. This measurement allows for the first time an estimation of the 68% confidence level interval for the isospin I=0 inverse scattering length of the ND¯ state f0,I=0-1 [-0.4,0.9] fm-1, assuming negligible interaction for the isospin I=1 channel. © 2022 CERN.
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| 20. |
- Acharya, S, et al.
(författare)
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Higher harmonic non-linear flow modes of charged hadrons in Pb-Pb collisions at √sNN = 5.02 TeV
- 2020
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2020:5
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Tidskriftsartikel (refereegranskat)abstract
- Anisotropic flow coefficients, vn, non-linear flow mode coefficients, χn,mk, and correlations among different symmetry planes, ρn,mk are measured in Pb-Pb collisions at sNN = 5.02 TeV. Results obtained with multi-particle correlations are reported for the transverse momentum interval 0.2 < pT< 5.0 GeV/c within the pseudorapidity interval 0.4 < |η| < 0.8 as a function of collision centrality. The vn coefficients and χn,mk and ρn,mk are presented up to the ninth and seventh harmonic order, respectively. Calculations suggest that the correlations measured in different symmetry planes and the non-linear flow mode coefficients are dependent on the shear and bulk viscosity to entropy ratios of the medium created in heavy-ion collisions. The comparison between these measurements and those at lower energies and calculations from hydrodynamic models places strong constraints on the initial conditions and transport properties of the system.
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| 21. |
- Acharya, S, et al.
(författare)
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Inclusive heavy-flavour production at central and forward rapidity in Xe–Xe collisions at sNN=5.44 TeV
- 2021
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 819
-
Tidskriftsartikel (refereegranskat)abstract
- The first measurements of the production of muons and electrons from heavy-flavour hadron decays in Xe–Xe collisions at sNN=5.44 TeV, using the ALICE detector at the LHC, are reported. The measurement of the nuclear modification factor RAA is performed as a function of transverse momentum pT in several centrality classes at forward rapidity (2.5
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| 22. |
- Acharya, S, et al.
(författare)
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Inclusive J / ψ production at midrapidity in pp collisions at √s=13 TeV
- 2021
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 81:12
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Tidskriftsartikel (refereegranskat)abstract
- We report on the inclusive J / ψ production cross section measured at the CERN Large Hadron Collider in proton–proton collisions at a center-of-mass energy s=13 TeV. The J / ψ mesons are reconstructed in the e +e - decay channel and the measurements are performed at midrapidity (| y| < 0.9) in the transverse-momentum interval 0 < pT< 40 GeV/c, using a minimum-bias data sample corresponding to an integrated luminosity Lint=32.2nb-1 and an Electromagnetic Calorimeter triggered data sample with Lint=8.3pb-1. The pT-integrated J / ψ production cross section at midrapidity, computed using the minimum-bias data sample, is dσ/dy|y=0=8.97±0.24(stat)±0.48(syst)±0.15(lumi)μb. An approximate logarithmic dependence with the collision energy is suggested by these results and available world data, in agreement with model predictions. The integrated and pT-differential measurements are compared with measurements in pp collisions at lower energies and with several recent phenomenological calculations based on the non-relativistic QCD and Color Evaporation models. © 2021, The Author(s).
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| 23. |
- Acharya, S, et al.
(författare)
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Investigation of the p–Σ0 interaction via femtoscopy in pp collisions
- 2020
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 805
-
Tidskriftsartikel (refereegranskat)abstract
- This Letter presents the first direct investigation of the p–Σ0 interaction, using the femtoscopy technique in high-multiplicity pp collisions at s=13 TeV measured by the ALICE detector. The Σ0 is reconstructed via the decay channel to Λγ, and the subsequent decay of Λ to pπ−. The photon is detected via the conversion in material to e+e− pairs exploiting the capability of the ALICE detector to measure electrons at low transverse momenta. The measured p–Σ0 correlation indicates a shallow strong interaction. The comparison of the data to several theoretical predictions obtained employing the Correlation Analysis Tool using the Schrödinger Equation (CATS) and the Lednický–Lyuboshits approach shows that the current experimental precision does not yet allow to discriminate between different models, as it is the case for the available scattering and hypernuclei data. Nevertheless, the p–Σ0 correlation function is found to be sensitive to the strong interaction, and driven by the interplay of the different spin and isospin channels. This pioneering study demonstrates the feasibility of a femtoscopic measurement in the p–Σ0 channel and with the expected larger data samples in LHC Run 3 and Run 4, the p–Σ0 interaction will be constrained with high precision. © 2020 European Organization for Nuclear Research
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| 24. |
- Acharya, S, et al.
(författare)
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J/ψ elliptic and triangular flow in Pb-Pb collisions at √sNN = 5.02 TeV
- 2020
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2020:10
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Tidskriftsartikel (refereegranskat)abstract
- The inclusive J/ψ elliptic (v2) and triangular (v3) flow coefficients measured at forward rapidity (2.5 < y < 4) and the v2 measured at midrapidity (|y| < 0.9) in Pb-Pb collisions at sNN = 5.02 TeV using the ALICE detector at the LHC are reported. The entire Pb-Pb data sample collected during Run 2 is employed, amounting to an integrated luminosity of 750 μb−1 at forward rapidity and 93 μb−1 at midrapidity. The results are obtained using the scalar product method and are reported as a function of transverse momentum pT and collision centrality. At midrapidity, the J/ψ v2 is in agreement with the forward rapidity measurement. The centrality averaged results indicate a positive J/ψ v3 with a significance of more than 5σ at forward rapidity in the pT range 2 < pT< 5 GeV/c. The forward rapidity v2, v3, and v3/v2 results at low and intermediate pT (pT ≲ 8 GeV/c) exhibit a mass hierarchy when compared to pions and D mesons, while converging into a species-independent curve at higher pT. At low and intermediate pT, the results could be interpreted in terms of a later thermalization of charm quarks compared to light quarks, while at high pT, path-length dependent effects seem to dominate. The J/ψ v2 measurements are further compared to a microscopic transport model calculation. Using a simplified extension of the quark scaling approach involving both light and charm quark flow components, it is shown that the D-meson vn measurements can be described based on those for charged pions and J/ψ flow. [Figure not available: see fulltext.] © 2020, The Author(s).
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| 25. |
- Acharya, S, et al.
(författare)
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J/ψ production as a function of charged-particle multiplicity in p-Pb collisions at √sNN = 8.16 TeV
- 2020
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2020:9
-
Tidskriftsartikel (refereegranskat)abstract
- Inclusive J/ψ yields and average transverse momenta in p-Pb collisions at a center-of-mass energy per nucleon pair sNN = 8.16 TeV are measured as a function of the charged-particle pseudorapidity density with ALICE. The J/ψ mesons are reconstructed at forward (2.03 < ycms< 3.53) and backward (−4.46 < ycms< −2.96) center-of-mass rapidity in their dimuon decay channel while the charged-particle pseudorapidity density is measured around midrapidity. The J/ψ yields at forward and backward rapidity normalized to their respective average values increase with the normalized charged-particle pseudorapidity density, the former showing a weaker increase than the latter. The normalized average transverse momenta at forward and backward rapidity manifest a steady increase from low to high charged-particle pseudorapidity density with a saturation beyond the average value. [Figure not available: see fulltext.] © 2020, The Author(s).
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| 26. |
- Acharya, S, et al.
(författare)
-
Jet-associated deuteron production in pp collisions at s=13 TeV
- 2021
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 819
-
Tidskriftsartikel (refereegranskat)abstract
- Deuteron production in high-energy collisions is sensitive to the space–time evolution of the collision system, and is typically described by a coalescence mechanism. For the first time, we present results on jet-associated deuteron production in pp collisions at s=13 TeV, providing an opportunity to test the established picture for deuteron production in events with a hard scattering. Using a trigger particle with high transverse-momentum (pT>5 GeV/c) as a proxy for the presence of a jet at midrapidity, we observe a measurable population of deuterons being produced around the jet proxy. The associated deuteron yield measured in a narrow angular range around the trigger particle differs by 2.4–4.8 standard deviations from the uncorrelated background. The data are described by PYTHIA model calculations featuring baryon coalescence. © 2021 The Author
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| 27. |
- Acharya, S, et al.
(författare)
-
Jet fragmentation transverse momentum distributions in pp and p-Pb collisions at √s , √sNN = 5.02 TeV
- 2021
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2021:9
-
Tidskriftsartikel (refereegranskat)abstract
- Jet fragmentation transverse momentum (jT) distributions are measured in proton-proton (pp) and proton-lead (p-Pb) collisions at sNN = 5.02 TeV with the ALICE experiment at the LHC. Jets are reconstructed with the ALICE tracking detectors and electromagnetic calorimeter using the anti-kT algorithm with resolution parameter R = 0.4 in the pseudorapidity range |η| < 0.25. The jT values are calculated for charged particles inside a fixed cone with a radius R = 0.4 around the reconstructed jet axis. The measured jT distributions are compared with a variety of parton-shower models. Herwig and Pythia 8 based models describe the data well for the higher jT region, while they underestimate the lower jT region. The jT distributions are further characterised by fitting them with a function composed of an inverse gamma function for higher jT values (called the “wide component”), related to the perturbative component of the fragmentation process, and with a Gaussian for lower jT values (called the “narrow component”), predominantly connected to the hadronisation process. The width of the Gaussian has only a weak dependence on jet transverse momentum, while that of the inverse gamma function increases with increasing jet transverse momentum. For the narrow component, the measured trends are successfully described by all models except for Herwig. For the wide component, Herwig and PYTHIA 8 based models slightly underestimate the data for the higher jet transverse momentum region. These measurements set constraints on models of jet fragmentation and hadronisation. [Figure not available: see fulltext.] © 2021, The Author(s).
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| 28. |
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| 29. |
- Acharya, S, et al.
(författare)
-
Kaon–proton strong interaction at low relative momentum via femtoscopy in Pb–Pb collisions at the LHC
- 2021
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 2021:9
-
Tidskriftsartikel (refereegranskat)abstract
- In quantum scattering processes between two particles, aspects characterizing the strong and Coulomb forces can be observed in kinematic distributions of the particle pairs. The sensitivity to the interaction potential reaches a maximum at low relative momentum and vanishing distance between the two particles. Ultrarelativistic heavy-ion collisions at the LHC provide an abundant source of many hadron species and can be employed as a measurement method of scattering parameters that is complementary to scattering experiments. This study confirms that momentum correlations of particles produced in Pb–Pb collisions at the LHC provide an accurate measurement of kaon–proton scattering parameters at low relative momentum, allowing precise access to the K−p→K−p process. This work also validates the femtoscopic measurement in ultrarelativistic heavy-ion collisions as an alternative to scattering experiments and a complementary tool to the study of exotic atoms with comparable precision. In this work, the first femtoscopic measurement of momentum correlations of K−p(K+p‾) and K+p(K−p‾) pairs in Pb–Pb collisions at centre-of-mass energy per nucleon pair of sNN=5.02 TeV registered by the ALICE experiment is reported. The components of the K−p complex scattering length are extracted and found to be ℜf0=−0.91±0.03(stat)−0.03+0.17(syst) and ℑf0=0.92±0.05(stat)−0.33+0.12(syst). The results are compared with chiral effective field theory predictions as well as with existing data from dedicated scattering and exotic kaonic atom experiments. © 2021 ALICE, European Organization for Nuclear Research
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| 30. |
- Acharya, S, et al.
(författare)
-
KS0 - and (anti-) Λ -hadron correlations in pp collisions at √s=13 TeV
- 2021
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6052 .- 1434-6044. ; 81:10
-
Tidskriftsartikel (refereegranskat)abstract
- Two-particle Azimuthal correlations are measured with the ALICE apparatus in pp collisions at s=13 TeV to explore strangeness- and multiplicity-related effects in the fragmentation of jets and the transition regime between bulk and hard production, probed with the condition that a strange meson (KS0) or baryon (Λ) with transverse momentum pT> 3 GeV/c is produced. Azimuthal correlations between kaons or Λ hyperons with other hadrons are presented at midrapidity for a broad range of the trigger (3
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| 31. |
- Acharya, S, et al.
(författare)
-
Long- and short-range correlations and their event-scale dependence in high-multiplicity pp collisions at √s = 13 TeV
- 2021
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2021:5
-
Tidskriftsartikel (refereegranskat)abstract
- Two-particle angular correlations are measured in high-multiplicity proton-proton collisions at s = 13 TeV by the ALICE Collaboration. The yields of particle pairs at short-(∆η ∼ 0) and long-range (1.6 < |∆η| < 1.8) in pseudorapidity are extracted on the near-side (∆φ ∼ 0). They are reported as a function of transverse momentum (pT) in the range 1 < pT< 4 GeV/c. Furthermore, the event-scale dependence is studied for the first time by requiring the presence of high-pT leading particles or jets for varying pT thresholds. The results demonstrate that the long-range “ridge” yield, possibly related to the collective behavior of the system, is present in events with high-pT processes as well. The magnitudes of the short- and long-range yields are found to grow with the event scale. The results are compared to EPOS LHC and PYTHIA 8 calculations, with and without string-shoving interactions. It is found that while both models describe the qualitative trends in the data, calculations from EPOS LHC show a better quantitative agreement for the pT dependency, while overestimating the event-scale dependency. [Figure not available: see fulltext.] © 2021, The Author(s).
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| 32. |
- Acharya, S, et al.
(författare)
-
Measurement of beauty and charm production in pp collisions at √s = 5.02 TeV via non-prompt and prompt D mesons
- 2021
-
Ingår i: Journal of High Energy Physics. - 1029-8479.
-
Tidskriftsartikel (refereegranskat)abstract
- The pT-differential production cross sections of prompt and non-prompt (produced in beauty-hadron decays) D mesons were measured by the ALICE experiment at midrapidity (|y|< 0.5) in proton-proton collisions at s = 5.02 TeV. The data sample used in the analysis corresponds to an integrated luminosity of (19.3 ± 0.4) nb−1. D mesons were reconstructed from their decays D0→ K−π+, D+→ K−π+π+, and Ds+→ϕπ+→K−K+π+ and their charge conjugates. Compared to previous measurements in the same rapidity region, the cross sections of prompt D+ and Ds+ mesons have an extended pT coverage and total uncertainties reduced by a factor ranging from 1.05 to 1.6, depending on pT, allowing for a more precise determination of their pT-integrated cross sections. The results are well described by perturbative QCD calculations. The fragmentation fraction of heavy quarks to strange mesons divided by the one to non-strange mesons, fs/(fu + fd), is compatible for charm and beauty quarks and with previous measurements at different centre-of-mass energies and collision systems. The b b ¯ production cross section per rapidity unit at midrapidity, estimated from non-prompt D-meson measurements, is dσbb¯/dy||y|<0.5=34.5±2.4(stat)−2.9+4.7(tot.syst) μb. It is compatible with previous measurements at the same centre-of-mass energy and with the cross section pre- dicted by perturbative QCD calculations. [Figure not available: see fulltext.] © 2021, The Author(s).
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| 33. |
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| 34. |
- Acharya, S, et al.
(författare)
-
Measurement of nuclear effects on ψ(2S) production in p-Pb collisions at √sNN = 8.16 TeV
- 2020
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2020:7
-
Tidskriftsartikel (refereegranskat)abstract
- Inclusive ψ(2S) production is measured in p-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair sNN = 8.16 TeV, using the ALICE detector at the CERN LHC. The production of ψ(2S) is studied at forward (2.03 < ycms< 3.53) and backward (−4.46 < ycms< −2.96) centre-of-mass rapidity and for transverse momentum pT< 12 GeV/c via the decay to muon pairs. In this paper, we report the integrated as well as the ycms- and pT-differential inclusive production cross sections. Nuclear effects on ψ(2S) production are studied via the determination of the nuclear modification factor that shows a strong suppression at both forward and backward centre-of-mass rapidities. Comparisons with corresponding results for inclusive J/ψ show a similar suppression for the two states at forward rapidity (p-going direction), but a stronger suppression for ψ(2S) at backward rapidity (Pb-going direction). As a function of pT, no clear dependence of the nuclear modification factor is found. The relative size of nuclear effects on ψ(2S) production compared to J/ψ is also studied via the double ratio of production cross sections [σψ(2S)/σJ/ψ]pPb/[σψ(2S)/σJ/ψ]pp between p-Pb and pp collisions. The results are compared with theoretical models that include various effects related to the initial and final state of the collision system and also with previous measurements at sNN = 5.02 TeV. [Figure not available: see fulltext.] © 2020, The Author(s).
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| 35. |
- Acharya, S, et al.
(författare)
-
Measurement of the Cross Sections of Ξc0 and Ξc+ Baryons and of the Branching-Fraction Ratio BR (Ξc0 → Ξ-e+νe)/BR (Ξc0 → Ξ-π+) in pp Collisions at s =13 TeV
- 2021
-
Ingår i: Physical Review Letters. - 1079-7114. ; 127:27
-
Tidskriftsartikel (refereegranskat)abstract
- The pT-differential cross sections of prompt charm-strange baryons Ξc0 and Ξc+ were measured at midrapidity (|y|<0.5) in proton-proton (pp) collisions at a center-of-mass energy s=13 TeV with the ALICE detector at the LHC. The Ξc0 baryon was reconstructed via both the semileptonic decay (Ξ-e+νe) and the hadronic decay (Ξ-π+) channels. The Ξc+ baryon was reconstructed via the hadronic decay (Ξ-π+π+) channel. The branching-fraction ratio BR(Ξc0→Ξ-e+νe)/BR(Ξc0→Ξ-π+)=1.38±0.14(stat)±0.22(syst) was measured with a total uncertainty reduced by a factor of about 3 with respect to the current world average reported by the Particle Data Group. The transverse momentum (pT) dependence of the Ξc0- and Ξc+-baryon production relative to the D0 meson and to the ςc0,+,++- and Λc+-baryon production are reported. The baryon-to-meson ratio increases toward low pT up to a value of approximately 0.3. The measurements are compared with various models that take different hadronization mechanisms into consideration. The results provide stringent constraints to these theoretical calculations and additional evidence that different processes are involved in charm hadronization in electron-positron (e+e-) and hadronic collisions.
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| 36. |
- Acharya, S, et al.
(författare)
-
Measurement of the Low-Energy Antideuteron Inelastic Cross Section
- 2020
-
Ingår i: Physical Review Letters. - 1079-7114. ; 125:16
-
Tidskriftsartikel (refereegranskat)abstract
- In this Letter, we report the first measurement of the inelastic cross section for antideuteron-nucleus interactions at low particle momenta, covering a range of 0.3≤p
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| 37. |
- Acharya, S, et al.
(författare)
-
Measurement of the production cross section of prompt Ξc0 baryons at midrapidity in pp collisions at √s = 5.02 TeV
- 2021
-
Ingår i: J. High Energy Phys.. - 1029-8479. ; 2021:10
-
Tidskriftsartikel (refereegranskat)abstract
- The transverse momentum (pT) differential cross section of the charm-strange baryon Ξc0 is measured at midrapidity (|y| < 0.5) via its semileptonic decay into e+Ξ−νe in pp collisions at s = 5.02 TeV with the ALICE detector at the LHC. The ratio of the pT-differential Ξc0-baryon and D0-meson production cross sections is also reported. The measurements are compared with simulations with different tunes of the PYTHIA 8 event generator, with predictions from a statistical hadronisation model (SHM) with a largely augmented set of charm-baryon states beyond the current lists of the Particle Data Group, and with models including hadronisation via quark coalescence. The pT-integrated cross section of prompt Ξc0-baryon production at midrapidity is also reported, which is used to calculate the baryon-to-meson ratio Ξc0/D0 = 0.20 ± 0.04 (stat.)−0.07+0.08 (syst.). These results provide an additional indication of a modification of the charm fragmentation from e+e− and e−p collisions to pp collisions. [Figure not available: see fulltext.] © 2021, The Author(s).
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| 38. |
- Acharya, S, et al.
(författare)
-
Measurements of inclusive jet spectra in pp and central Pb-Pb collisions at sNN =5.02 TeV
- 2020
-
Ingår i: Physical Review C. - 2469-9985. ; 101:3
-
Tidskriftsartikel (refereegranskat)abstract
- This article reports measurements of the pT-differential inclusive jet cross section in pp collisions at s=5.02TeV and the pT-differential inclusive jet yield in Pb-Pb 0-10% central collisions at sNN=5.02TeV. Jets were reconstructed at midrapidity with the ALICE tracking detectors and electromagnetic calorimeter using the anti-kT algorithm. For pp collisions, we report jet cross sections for jet resolution parameters R=0.1-0.6 over the range 20
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| 39. |
- Acharya, S, et al.
(författare)
-
Measurements of mixed harmonic cumulants in Pb–Pb collisions at sNN=5.02 TeV
- 2021
-
Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 818
-
Tidskriftsartikel (refereegranskat)abstract
- Correlations between moments of different flow coefficients are measured in Pb–Pb collisions at sNN=5.02 TeV recorded with the ALICE detector. These new measurements are based on multiparticle mixed harmonic cumulants calculated using charged particles in the pseudorapidity region |η|<0.8 with the transverse momentum range 0.2
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| 40. |
- Acharya, S, et al.
(författare)
-
Multiharmonic Correlations of Different Flow Amplitudes in Pb-Pb Collisions at sNN =2.76 TeV
- 2021
-
Ingår i: Physical Review Letters. - 1079-7114. ; 127:9
-
Tidskriftsartikel (refereegranskat)abstract
- The event-by-event correlations between three flow amplitudes are measured for the first time in Pb-Pb collisions, using higher-order symmetric cumulants. We find that different three-harmonic correlations develop during the collective evolution of the medium when compared to correlations that exist in the initial state. These new results cannot be interpreted in terms of previous lower-order flow measurements since contributions from two-harmonic correlations are explicitly removed in the new observables. A comparison to Monte Carlo simulations provides new and independent constraints for the initial conditions and system properties of nuclear matter created in heavy-ion collisions. © 2021 CERN, for the ALICE Collaboration.
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| 41. |
- Acharya, S, et al.
(författare)
-
Multiplicity dependence of inclusive J/ψ production at midrapidity in pp collisions at s=13 TeV
- 2020
-
Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 810
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of the inclusive J/ψ yield as a function of charged-particle pseudorapidity density dNch/dη in pp collisions at s=13 TeV with ALICE at the LHC are reported. The J/ψ meson yield is measured at midrapidity (|y|<0.9) in the dielectron channel, for events selected based on the charged-particle multiplicity at midrapidity (|η|<1) and at forward rapidity (−3.7<η<−1.7 and 2.8<η<5.1); both observables are normalized to their corresponding averages in minimum bias events. The increase of the normalized J/ψ yield with normalized dNch/dη is significantly stronger than linear and dependent on the transverse momentum. The data are compared to theoretical predictions, which describe the observed trends well, albeit not always quantitatively. © 2020 European Organization for Nuclear Research
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| 42. |
- Acharya, S, et al.
(författare)
-
Multiplicity dependence of K*(892)0 and ϕ(1020) production in pp collisions at s=13 TeV
- 2020
-
Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 807
-
Tidskriftsartikel (refereegranskat)abstract
- The striking similarities that have been observed between high-multiplicity proton-proton (pp) collisions and heavy-ion collisions can be explored through multiplicity-differential measurements of identified hadrons in pp collisions. With these measurements, it is possible to study mechanisms such as collective flow that determine the shapes of hadron transverse momentum (pT) spectra, to search for possible modifications of the yields of short-lived hadronic resonances due to scattering effects in an extended hadron-gas phase, and to investigate different explanations provided by phenomenological models for enhancement of strangeness production with increasing multiplicity. In this paper, these topics are addressed through measurements of the K⁎(892)0 and ϕ(1020) mesons at midrapidity in pp collisions at s= 13 TeV as a function of the charged-particle multiplicity. The results include the pT spectra, pT-integrated yields, mean transverse momenta, and the ratios of the yields of these resonances to those of longer-lived hadrons. Comparisons with results from other collision systems and energies, as well as predictions from phenomenological models, are also discussed. © 2020 European Organization for Nuclear Research
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| 43. |
- Acharya, S, et al.
(författare)
-
Multiplicity dependence of π , K, and p production in pp collisions at √s=13 TeV
- 2020
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:8
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the measurements of π±, K ±, p and p ¯ transverse momentum (pT) spectra as a function of charged-particle multiplicity density in proton–proton (pp) collisions at s=13TeV with the ALICE detector at the LHC. Such study allows us to isolate the center-of-mass energy dependence of light-flavour particle production. The measurements reported here cover a pT range from 0.1 to 20 GeV / c and are done in the rapidity interval | y| < 0.5. The pT-differential particle ratios exhibit an evolution with multiplicity, similar to that observed in pp collisions at s=7TeV, which is qualitatively described by some of the hydrodynamical and pQCD-inspired models discussed in this paper. Furthermore, the pT-integrated hadron-to-pion yield ratios measured in pp collisions at two different center-of-mass energies are consistent when compared at similar multiplicities. This also extends to strange and multi-strange hadrons, suggesting that, at LHC energies, particle hadrochemistry scales with particle multiplicity the same way under different collision energies and colliding systems. © 2020, CERN for the benefit of the ALICE collaboration.
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| 44. |
- Acharya, S, et al.
(författare)
-
Non-linear flow modes of identified particles in Pb-Pb collisions at √sNN = 5.02 TeV
- 2020
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2020:6
-
Tidskriftsartikel (refereegranskat)abstract
- The pT-differential non-linear flow modes, v4,22, v5,32, v6,33 and v6,222 for π±, K±, KS0 , p + p ¯ , Λ + Λ ¯ and ϕ-meson have been measured for the first time at sNN = 5.02 TeV in Pb-Pb collisions with the ALICE detector at the Large Hadron Collider. The results were obtained with a multi-particle technique, correlating the identified hadrons with reference charged particles from a different pseudorapidity region. These non-linear observables probe the contribution from the second and third order initial spatial anisotropy coefficients to higher flow harmonics. All the characteristic features observed in previous pT-differential anisotropic flow measurements for various particle species are also present in the non-linear flow modes, i.e. increase of magnitude with increasing centrality percentile, mass ordering at low pT and particle type grouping in the intermediate pT range. Hydrodynamical calculations (iEBE-VISHNU) that use different initial conditions and values of shear and bulk viscosity to entropy density ratios are confronted with the data at low transverse momenta. These calculations exhibit a better agreement with the anisotropic flow coefficients than the non-linear flow modes. These observations indicate that non-linear flow modes can provide additional discriminatory power in the study of initial conditions as well as new stringent constraints to hydrodynamical calculations. [Figure not available: see fulltext.]. © 2020, The Author(s).
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| 45. |
- Acharya, S, et al.
(författare)
-
Pion–kaon femtoscopy and the lifetime of the hadronic phase in Pb−Pb collisions at sNN=2.76 TeV
- 2021
-
Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 813
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the first femtoscopic analysis of pion–kaon correlations at the LHC is reported. The analysis was performed on the Pb–Pb collision data at sNN=2.76 TeV recorded with the ALICE detector. The non-identical particle correlations probe the spatio-temporal separation between sources of different particle species as well as the average source size of the emitting system. The sizes of the pion and kaon sources increase with centrality, and pions are emitted closer to the centre of the system and/or later than kaons. This is naturally expected in a system with strong radial flow and is qualitatively reproduced by hydrodynamic models. ALICE data on pion–kaon emission asymmetry are consistent with (3+1)-dimensional viscous hydrodynamics coupled to a statistical hadronisation model, resonance propagation, and decay code THERMINATOR 2 calculation, with an additional time delay between 1 and 2 fm/c for kaons. The delay can be interpreted as evidence for a significant hadronic rescattering phase in heavy-ion collisions at the LHC. © 2020 The Author
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| 46. |
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| 47. |
- Acharya, S, et al.
(författare)
-
Production of light (anti)nuclei in pp collisions at √s = 13 TeV
- 2022
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2022:1
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the production mechanism of light (anti)nuclei is one of the key challenges of nuclear physics and has important consequences for astrophysics, since it provides an input for indirect dark-matter searches in space. In this paper, the latest results about the production of light (anti)nuclei in pp collisions at s = 13 TeV are presented, focusing on the comparison with the predictions of coalescence and thermal models. For the first time, the coalescence parameters B2 for deuterons and B3 for helions are compared with parameter-free theoretical predictions that are directly constrained by the femtoscopic measurement of the source radius in the same event class. A fair description of the data with a Gaussian wave function is observed for both deuteron and helion, supporting the coalescence mechanism for the production of light (anti)nuclei in pp collisions. This method paves the way for future investigations of the internal structure of more complex nuclear clusters, including the hypertriton. [Figure not available: see fulltext.]. © 2022, The Author(s).
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| 48. |
- Acharya, S, et al.
(författare)
-
Production of light-flavor hadrons in pp collisions at √s=7and√s=13TeV
- 2021
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 81:3
-
Tidskriftsartikel (refereegranskat)abstract
- The production of π±, K ±, KS0, K ∗(892) , p , ϕ(1020) , Λ , Ξ -, Ω -, and their antiparticles was measured in inelastic proton–proton (pp) collisions at a center-of-mass energy of s = 13 TeV at midrapidity (| y| < 0.5) as a function of transverse momentum (pT) using the ALICE detector at the CERN LHC. Furthermore, the single-particle pT distributions of KS0, Λ , and Λ ¯ in inelastic pp collisions at s=7 TeV are reported here for the first time. The pT distributions are studied at midrapidity within the transverse momentum range 0 ≤ pT≤ 20 GeV/c, depending on the particle species. The pT spectra, integrated yields, and particle yield ratios are discussed as a function of collision energy and compared with measurements at lower s and with results from various general-purpose QCD-inspired Monte Carlo models. A hardening of the spectra at high pT with increasing collision energy is observed, which is similar for all particle species under study. The transverse mass and xT≡2pT/s scaling properties of hadron production are also studied. As the collision energy increases from s = 7–13 TeV, the yields of non- and single-strange hadrons normalized to the pion yields remain approximately constant as a function of s, while ratios for multi-strange hadrons indicate enhancements. The pT-differential cross sections of π±, K ± and p (p ¯) are compared with next-to-leading order perturbative QCD calculations, which are found to overestimate the cross sections for π± and p (p ¯) at high pT. © 2021, CERN for the benefit of the ALICE collaboration.
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| 49. |
- Acharya, S, et al.
(författare)
-
Production of muons from heavy-flavour hadron decays at high transverse momentum in Pb–Pb collisions at sNN=5.02 and 2.76 TeV
- 2021
-
Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 820
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of the production of muons from heavy-flavour hadron decays in Pb–Pb collisions at sNN=5.02 and 2.76 TeV using the ALICE detector at the LHC are reported. The nuclear modification factor RAA at sNN=5.02 TeV is measured at forward rapidity (2.57 GeV/c). The RAA shows an increase of the suppression of the yields of muons from heavy-flavour hadron decays with increasing centrality. A suppression by a factor of about three is observed in the 10% most central collisions. The RAA at sNN=5.02 TeV is similar to that at sNN=2.76 TeV. The precise RAA measurements have the potential to distinguish between model predictions implementing different mechanisms of parton energy loss in the high-density medium formed in heavy-ion collisions. They place important constraints for the understanding of the heavy-quark interaction with the hot and dense QCD medium. © 2021 European Organization for Nuclear Research, ALICE
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| 50. |
- Acharya, S, et al.
(författare)
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Production of pions, kaons, (anti-)protons and ϕ mesons in Xe–Xe collisions at √sNN = 5.44 TeV
- 2021
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 81:7
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Tidskriftsartikel (refereegranskat)abstract
- The first measurement of the production of pions, kaons, (anti-)protons and ϕ mesons at midrapidity in Xe–Xe collisions at sNN=5.44TeV is presented. Transverse momentum (pT) spectra and pT-integrated yields are extracted in several centrality intervals bridging from p–Pb to mid-central Pb–Pb collisions in terms of final-state multiplicity. The study of Xe–Xe and Pb–Pb collisions allows systems at similar charged-particle multiplicities but with different initial geometrical eccentricities to be investigated. A detailed comparison of the spectral shapes in the two systems reveals an opposite behaviour for radial and elliptic flow. In particular, this study shows that the radial flow does not depend on the colliding system when compared at similar charged-particle multiplicity. In terms of hadron chemistry, the previously observed smooth evolution of particle ratios with multiplicity from small to large collision systems is also found to hold in Xe–Xe. In addition, our results confirm that two remarkable features of particle production at LHC energies are also valid in the collision of medium-sized nuclei: the lower proton-to-pion ratio with respect to the thermal model expectations and the increase of the ϕ-to-pion ratio with increasing final-state multiplicity. © 2021, The Author(s).
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