| 11. |
- 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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| 12. |
- Acharya, S, et al.
(författare)
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Jet-associated deuteron production in pp collisions at s=13 TeV
- 2021
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 819
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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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| 13. |
- Acharya, S, et al.
(författare)
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Jet fragmentation transverse momentum distributions in pp and p-Pb collisions at √s , √sNN = 5.02 TeV
- 2021
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2021:9
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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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| 14. |
- Acharya, S, et al.
(författare)
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Kaon–proton strong interaction at low relative momentum via femtoscopy in Pb–Pb collisions at the LHC
- 2021
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 2021:9
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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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| 15. |
- Acharya, S, et al.
(författare)
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KS0 - and (anti-) Λ -hadron correlations in pp collisions at √s=13 TeV
- 2021
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6052 .- 1434-6044. ; 81:10
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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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| 16. |
- Acharya, S, et al.
(författare)
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Long- and short-range correlations and their event-scale dependence in high-multiplicity pp collisions at √s = 13 TeV
- 2021
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; 2021:5
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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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| 17. |
- Acharya, S, et al.
(författare)
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Measurement of beauty and charm production in pp collisions at √s = 5.02 TeV via non-prompt and prompt D mesons
- 2021
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Ingår i: Journal of High Energy Physics. - 1029-8479.
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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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| 18. |
- Acharya, S, et al.
(författare)
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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
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Ingår i: Physical Review Letters. - 1079-7114. ; 127:27
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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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| 19. |
- Acharya, S, et al.
(författare)
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Measurement of the production cross section of prompt Ξc0 baryons at midrapidity in pp collisions at √s = 5.02 TeV
- 2021
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Ingår i: J. High Energy Phys.. - 1029-8479. ; 2021:10
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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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| 20. |
- Acharya, S, et al.
(författare)
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Measurements of mixed harmonic cumulants in Pb–Pb collisions at sNN=5.02 TeV
- 2021
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Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 818
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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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