| 11. |
- Acharya, S., et al.
(author)
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Elliptic flow of charged particles at midrapidity relative to the spectator plane in Pb–Pb and Xe–Xe collisions
- 2023
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In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 846
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Journal article (peer-reviewed)abstract
- Measurements of the elliptic flow coefficient relative to the collision plane defined by the spectator neutrons v2{ΨSP} in collisions of Pb ions at center-of-mass energy per nucleon–nucleon pair sNN=2.76 TeV and Xe ions at sNN=5.44 TeV are reported. The results are presented for charged particles produced at midrapidity as a function of centrality and transverse momentum for the 5–70% and 0.2–6 GeV/c ranges, respectively. The ratio between v2{ΨSP} and the elliptic flow coefficient relative to the participant plane v2{4}, estimated using four-particle correlations, deviates by up to 20% from unity depending on centrality. This observation differs strongly from the magnitude of the corresponding eccentricity ratios predicted by the TRENTo and the elliptic power models of initial state fluctuations that are tuned to describe the participant plane anisotropies. The differences can be interpreted as a decorrelation of the neutron spectator plane and the reaction plane because of fragmentation of the remnants from the colliding nuclei, which points to an incompleteness of current models describing the initial state fluctuations. A significant transverse momentum dependence of the ratio v2{ΨSP}/v2{4} is observed in all but the most central collisions, which may help to understand whether momentum anisotropies at low and intermediate transverse momentum have a common origin in initial state fluctuations. The ratios of v2{ΨSP} and v2{4} to the corresponding initial state eccentricities for Xe–Xe and Pb–Pb collisions at similar initial entropy density show a difference of (7.0±0.9)% with an additional variation of +1.8% when including RHIC data in the TRENTo parameter extraction. These observations provide new experimental constraints for viscous effects in the hydrodynamic modeling of the expanding quark–gluon plasma produced in heavy-ion collisions at the LHC. © 2022 The Author(s)
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| 12. |
- Acharya, S., et al.
(author)
-
Enhanced Deuteron Coalescence Probability in Jets
- 2023
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In: Physical Review Letters. - 0031-9007. ; 131:4
-
Journal article (peer-reviewed)abstract
- The transverse-momentum (pT) spectra and coalescence parameters B2 of (anti)deuterons are measured in p-p collisions at s=13 TeV for the first time in and out of jets. In this measurement, the direction of the leading particle with the highest pT in the event (pTlead>5 GeV/c) is used as an approximation for the jet axis. The event is consequently divided into three azimuthal regions, and the jet signal is obtained as the difference between the toward region, that contains jet fragmentation products in addition to the underlying event (UE), and the transverse region, which is dominated by the UE. The coalescence parameter in the jet is found to be approximately a factor of 10 larger than that in the underlying event. This experimental observation is consistent with the coalescence picture and can be attributed to the smaller average phase-space distance between nucleons in the jet cone as compared with the underlying event. The results presented in this Letter are compared to predictions from a simple nucleon coalescence model, where the phase-space distributions of nucleons are generated using pythia8 with the Monash 2013 tuning, and to predictions from a deuteron production model based on ordinary nuclear reactions with parametrized energy-dependent cross sections tuned on data. The latter model is implemented in pythia8.3. Both models reproduce the observed large difference between in-jet and out-of-jet coalescence parameters, although the almost flat trend of the B2Jet is not reproduced by the models, which instead give a decreasing trend. © 2023 CERN.
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| 13. |
- Acharya, S., et al.
(author)
-
Exploring the NΛ–NΣ coupled system with high precision correlation techniques at the LHC
- 2022
-
In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 833
-
Journal article (peer-reviewed)abstract
- The interaction of Λ and Σ hyperons (Y) with nucleons (N) is strongly influenced by the coupled-channel dynamics. Due to the small mass difference of the NΛ and NΣ systems, the sizable coupling strength of the NΣ↔NΛ processes constitutes a crucial element in the determination of the NΛ interaction. In this letter we present the most precise measurements on the interaction of pΛ pairs, from zero relative momentum up to the opening of the NΣ channel. The correlation function in the relative momentum space for pΛ⊕p‾Λ‾ pairs measured in high-multiplicity triggered pp collisions at s=13 TeV at the LHC is reported. The opening of the inelastic NΣ channels is visible in the extracted correlation function as a cusp-like structure occurring at relative momentum k⁎=289MeV/c. This represents the first direct experimental observation of the NΣ↔NΛ coupled channel in the pΛ system. The correlation function is compared with recent chiral effective field theory calculations, based on different strengths of the NΣ↔NΛ transition potential. A weaker coupling, as possibly supported by the present measurement, would require a more repulsive three-body NNΛ interaction for a proper description of the Λ in-medium properties, which has implications on the nuclear equation of state and for the presence of hyperons inside neutron stars. © 2022 European Organization for Nuclear Research, ALICE
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| 14. |
- Acharya, S., et al.
(author)
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Extending the ALICE strong-interaction studies to nuclei: measurement of proton-deuteron correlations in pp collisions at √s = 13 TeV
- 2022
-
In: The European Physical Society Conference on High Energy Physics. - Trieste, Italy : Sissa Medialab. - 1824-8039. ; 398
-
Conference paper (peer-reviewed)abstract
- The large data sample of high-multiplicity pp collisions collected by ALICE allows for the precise measurement of the size of source producing primary hadrons, opening the doors to a study of the interaction of different hadron species using femtoscopy techniques. The momentum correlation between (anti)protons and (anti)deuterons measured in pp collisions at √s = 13 TeV with ALICE is studied here for the first time. The measured correlation function for ((equation presented))p-((equation presented))d pairs is compared with theoretical predictions obtained considering Coulomb and Coulomb plus strong interactions and employing the Lednický-Lyuboshitz model with scattering parameters extracted from traditional scattering experiments for the p-d system. The measured correlation function can not be reproduced by any of the obtained predictions. This deviation can to large extent be interpreted as a demonstration of the late formation time of (anti)deuterons in hadron-hadron collisions. This observation is key for the understanding of the production mechanism of light (anti)nuclei, which is an open issue in high-energy physics and has also important consequences for the study of antinuclei formation in the interstellar medium either from collisions triggered by high-energy cosmic rays or by dark matter decays. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0)
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| 15. |
- Acharya, S., et al.
(author)
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f0(980) production in inelastic pp collisions at s = 5.02 TeV
- 2023
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In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 846
-
Journal article (peer-reviewed)abstract
- The measurement of the production of f0(980) in inelastic pp collisions at s=5.02 TeV is presented. This is the first reported measurement of inclusive f0(980) yield at LHC energies. The production is measured at midrapidity, |y|
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| 16. |
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| 17. |
- Acharya, S., et al.
(author)
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First measurement of prompt and non-prompt D⁎+ vector meson spin alignment in pp collisions at s=13 TeV
- 2023
-
In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 846
-
Journal article (peer-reviewed)abstract
- This letter reports the first measurement of spin alignment, with respect to the helicity axis, for D⁎+ vector mesons and their charge conjugates from charm-quark hadronisation (prompt) and from beauty-meson decays (non-prompt) in hadron collisions. The measurements were performed at midrapidity (|y|
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| 18. |
- Acharya, S., et al.
(author)
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First measurement of quarkonium polarization in nuclear collisions at the LHC
- 2021
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In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 815
-
Journal article (peer-reviewed)abstract
- The polarization of inclusive J/ψ and ϒ(1S) produced in Pb–Pb collisions at sNN=5.02 TeV at the LHC is measured with the ALICE detector. The study is carried out by reconstructing the quarkonium through its decay to muon pairs in the rapidity region 2.5
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| 19. |
- Acharya, S., et al.
(author)
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First measurement of the Λ–Ξ interaction in proton–proton collisions at the LHC
- 2023
-
In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 844
-
Journal article (peer-reviewed)abstract
- The first experimental information on the strong interaction between Λ and Ξ− strange baryons is presented in this Letter. The correlation function of Λ–Ξ− and Λ‾–Ξ‾+ pairs produced in high-multiplicity proton–proton (pp) collisions at s=13 TeV at the LHC is measured as a function of the relative momentum of the pair. The femtoscopy method is used to calculate the correlation function, which is then compared with theoretical expectations obtained using a meson exchange model, chiral effective field theory, and Lattice QCD calculations close to the physical point. Data support predictions of small scattering parameters while discarding versions with large ones, thus suggesting a weak Λ–Ξ− interaction. The limited statistical significance of the data does not yet allow one to constrain the effects of coupled channels like Σ–Ξ and N–Ω.
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| 20. |
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