| 1. |
- Acharya, S., et al.
(författare)
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Data-driven precision determination of the material budget in ALICE
- 2023
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 18:11
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Tidskriftsartikel (refereegranskat)abstract
- The knowledge of the material budget with a high precision is fundamental for measurements of direct photon production using the photon conversion method due to its direct impact on the total systematic uncertainty. Moreover, it influences many aspects of the charged-particle reconstruction performance. In this article, two procedures to determine data-driven corrections to the material-budget description in ALICE simulation software are developed. One is based on the precise knowledge of the gas composition in the Time Projection Chamber. The other is based on the robustness of the ratio between the produced number of photons and charged particles, to a large extent due to the approximate isospin symmetry in the number of produced neutral and charged pions. Both methods are applied to ALICE data allowing for a reduction of the overall material budget systematic uncertainty from 4.5% down to 2.5%. Using these methods, a locally correct material budget is also achieved. The two proposed methods are generic and can be applied to any experiment in a similar fashion. © 2023 CERN for the benefit of the Alice collaboration.
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| 2. |
- Acharya, S., et al.
(författare)
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Exclusive and dissociative J/ψ photoproduction, and exclusive dimuon production, in p-Pb collisions at sNN =8.16 TeV
- 2023
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Ingår i: Physical Review D. - 2470-0010. ; 108:11
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Tidskriftsartikel (refereegranskat)abstract
- The ALICE Collaboration reports three measurements in ultraperipheral proton-lead collisions at forward rapidity. The exclusive two-photon process γγ→μ+μ- and the exclusive photoproduction of J/ψ are studied. J/ψ photoproduction with proton dissociation is measured for the first time at a hadron collider. The cross section for the two-photon process of dimuons in the invariant mass range from 1 to 2.5 GeV/c2 agrees with leading-order quantum electrodynamics calculations. The exclusive and dissociative cross sections for J/ψ photoproductions are measured for photon-proton center-of-mass energies from 27 to 57 GeV. They are in good agreement with HERA results.
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| 3. |
- Acharya, S., et al.
(författare)
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Measurement of the non-prompt D-meson fraction as a function of multiplicity in proton-proton collisions at √s = 13 TeV
- 2023
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2023:10
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Tidskriftsartikel (refereegranskat)abstract
- The fractions of non-prompt (i.e. originating from beauty-hadron decays) D0 and D+ mesons with respect to the inclusive yield are measured as a function of the charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy of s = 13 TeV with the ALICE detector at the LHC. The results are reported in intervals of transverse momentum (p T) and integrated in the range 1 < p T < 24 GeV/c. The fraction of non-prompt D0 and D+ mesons is found to increase slightly as a function of p T in all the measured multiplicity intervals, while no significant dependence on the charged-particle multiplicity is observed. In order to investigate the production and hadronisation mechanisms of charm and beauty quarks, the results are compared to PYTHIA 8 as well as EPOS 3 and EPOS 4 Monte Carlo simulations, and to calculations based on the colour glass condensate including three-pomeron fusion. [Figure not available: see fulltext.]. © 2023, The Author(s).
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| 4. |
- Acharya, S., et al.
(författare)
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Measurement of the radius dependence of charged-particle jet suppression in Pb–Pb collisions at sNN=5.02TeV
- 2024
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 849
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Tidskriftsartikel (refereegranskat)abstract
- The ALICE Collaboration reports a differential measurement of inclusive jet suppression using pp and Pb–Pb collision data at a center-of-mass energy per nucleon–nucleon collision sNN=5.02 TeV. Charged-particle jets are reconstructed using the anti-kT algorithm with resolution parameters R=0.2, 0.3, 0.4, 0.5, and 0.6 in pp collisions and R=0.2, 0.4, 0.6 in central (0–10%), semi-central (30–50%), and peripheral (60–80%) Pb–Pb collisions. A novel approach based on machine learning is employed to mitigate the influence of jet background. This enables measurements of inclusive jet suppression in new regions of phase space, including down to the lowest jet pT≥40 GeV/c at R=0.6 in central Pb–Pb collisions. This is an important step for discriminating different models of jet quenching in the quark–gluon plasma. The transverse momentum spectra, nuclear modification factors, derived cross section, and nuclear modification factor ratios for different jet resolution parameters of charged-particle jets are presented and compared to model predictions. A mild dependence of the nuclear modification factor ratios on collision centrality and resolution parameter is observed. The results are compared to a variety of jet-quenching models with varying levels of agreement.
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| 5. |
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| 6. |
- Acharya, S., et al.
(författare)
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Study of flavor dependence of the baryon-to-meson ratio in proton-proton collisions at s =13 TeV
- 2023
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Ingår i: Physical Review D. - 2470-0010. ; 108:11
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Tidskriftsartikel (refereegranskat)abstract
- The production cross sections of D0 and Λ+c hadrons originating from beauty-hadron decays (i.e., nonprompt) were measured for the first time at midrapidity (|y|<0.5) by the ALICE Collaboration in proton-proton collisions at a center-of-mass energy √s=13 TeV. They are described within uncertainties by perturbative QCD calculations employing the fragmentation fractions of beauty quarks to baryons measured at forward rapidity by the LHCb Collaboration. The b¯b production cross section per unit of rapidity at midrapidity, estimated from these measurements, is dσb¯b/dy||y|<0.5=83.1±3.5(stat)±5.4(syst)+12.3−3.2(extrap) μb. The baryon-to-meson ratios are computed to investigate the hadronization mechanism of beauty quarks. The nonprompt Λ+c/D0 production ratio has a similar trend to the one measured for the promptly produced charmed particles and to the p/π+ and Λ/K0S ratios, suggesting a similar baryon-formation mechanism among light, strange, charm, and beauty hadrons. The pT -integrated nonprompt Λ+c/D0 ratio is found to be significantly higher than the one measured in e+e− collisions.
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| 7. |
- Acharya, S., et al.
(författare)
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System-size dependence of the hadronic rescattering effect at energies available at the CERN Large Hadron Collider
- 2024
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Ingår i: Physical Review C. - 2469-9985. ; 109:1
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Tidskriftsartikel (refereegranskat)abstract
- The first measurements of K∗(892)0 resonance production as a function of charged-particle multiplicity in Xe-Xe collisions at sNN=5.44 TeV and pp collisions ats=5.02 TeV using the ALICE detector are presented. The resonance is reconstructed at midrapidity (|y| < 0.5) using the hadronic decay channel K∗0 →K±π∓. Measurements of transverse-momentum integrated yield, mean transverse-momentum, nuclear modification factor of K∗0, and yield ratios of resonance to stable hadron (K∗0/K) are compared across different collision systems (pp, p-Pb, Xe-Xe, and Pb-Pb) at similar collision energies to investigate how the production of K∗0 resonances depends on the size of the system formed in these collisions. The hadronic rescattering effect is found to be independent of the size of colliding systems and mainly driven by the produced charged-particle multiplicity, which is a proxy of the volume of produced matter at the chemical freeze-out. In addition, the production yields of K∗0 in Xe-Xe collisions are utilized to constrain the dependence of the kinetic freeze-out temperature on the system size using the hadron resonance gas-partial chemical equilibrium model. © 2024 CERN.
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| 8. |
- Acharya, S., et al.
(författare)
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ψ (2S) Suppression in Pb-Pb Collisions at the LHC
- 2024
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Ingår i: Physical Review Letters. - 0031-9007. ; 132:4
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Tidskriftsartikel (refereegranskat)abstract
- The production of the ψ(2S) charmonium state was measured with ALICE in Pb-Pb collisions at √sNN=5.02 TeV, in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity (2.5
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