Showing papers by "Malgorzata Anna Janik published in 2023"
TL;DR: In this article , the production of prompt Λc+ baryons at midrapidity (|y| < 0.5) was measured in central and mid-central Pb-Pb collisions at the center-of-mass energy per nucleon-nucleon pair sNN=5.02 TeV with the ALICE detector.
3 citations
TL;DR: In this paper , the authors report on the inclusive production cross section of several quarkonium states, and measured with the ALICE detector at the LHC, in pp collisions at 5.5.
Abstract: Abstract This article reports on the inclusive production cross section of several quarkonium states, $$\textrm{J}/\psi $$ J / ψ , $$\psi \mathrm{(2S)}$$ ψ ( 2 S ) , $$\Upsilon \mathrm (1S)$$ Υ ( 1 S ) , $$\Upsilon \mathrm{(2S)}$$ Υ ( 2 S ) , and $$\Upsilon \mathrm{(3S)}$$ Υ ( 3 S ) , measured with the ALICE detector at the LHC, in pp collisions at $$\sqrt{s} = 5.02$$ s = 5.02 TeV. The analysis is performed in the dimuon decay channel at forward rapidity ( $$2.5< y < 4$$ 2.5 < y < 4 ). The integrated cross sections and transverse-momentum ( $$p_{\textrm{T}}$$ p T ) and rapidity ( $$y$$ y ) differential cross sections for $$\textrm{J}/\psi $$ J / ψ , $$\psi \mathrm{(2S)}$$ ψ ( 2 S ) , $$\Upsilon \mathrm (1S)$$ Υ ( 1 S ) , and the $$\psi \mathrm{(2S)}$$ ψ ( 2 S ) -to- $$\textrm{J}/\psi $$ J / ψ cross section ratios are presented. The integrated cross sections, assuming unpolarized quarkonia, are: $$\sigma _{\textrm{J}/\psi }$$ σ J / ψ ( $$p_{\textrm{T}} <20$$ p T < 20 GeV/c) = 5.88 ± 0.03 ± 0.34 $$ ~\mu $$ μ b, $$\sigma _{\psi \mathrm{(2S)}}$$ σ ψ ( 2 S ) ( $$p_{\textrm{T}} <12$$ p T < 12 GeV/c) = 0.87 ± 0.06 ± 0.10 $$~\mu $$ μ b, $$\sigma _{\Upsilon \mathrm (1S)}$$ σ Υ ( 1 S ) ( $$p_{\textrm{T}} <15$$ p T < 15 GeV/c) = 45.5 ± 3.9 ± 3.5 nb, $$\sigma _{\Upsilon \mathrm{(2S)}}$$ σ Υ ( 2 S ) ( $$p_{\textrm{T}} <15$$ p T < 15 GeV/c) = 22.4 ± 3.2 ± 2.7 nb, and $$\sigma _{\Upsilon \mathrm{(3S)}}$$ σ Υ ( 3 S ) ( $$p_{\textrm{T}} <15$$ p T < 15 GeV/c) = 4.9 ± 2.2 ± 1.0 nb, where the first (second) uncertainty is the statistical (systematic) one. For the first time, the cross sections of the three $$\Upsilon $$ Υ states, as well as the $$\psi \mathrm{(2S)}$$ ψ ( 2 S ) one as a function of $$p_{\textrm{T}}$$ p T and $$y$$ y , are measured at $$\sqrt{s} = 5.02$$ s = 5.02 TeV at forward rapidity. These measurements also significantly extend the $$\textrm{J}/\psi $$ J / ψ $$p_{\textrm{T}}$$ p T reach and supersede previously published results. A comparison with ALICE measurements in pp collisions at $$\sqrt{s} = 2.76$$ s = 2.76 , 7, 8, and 13 TeV is presented and the energy dependence of quarkonium production cross sections is discussed. Finally, the results are compared with the predictions from several production models.
2 citations
TL;DR: In this paper , the ALICE detector was used to measure the production of prompt (cid:2) + c baryons at mid-rapidity ( | y | < 0 . 5) and reach much lower transverse momentum (p T = 1 GeV / c ) with respect to previous measurements performed by the ALice, STAR, and CMS Collaborations in nucleus-nucleus collisions, allowing for an extrapolation down to p T = 0.
Abstract: The production of prompt (cid:2) + c baryons at midrapidity ( | y | < 0 . 5) was measured in central (0–10%) and mid-central (30–50%) Pb–Pb collisions at the center-of-mass energy per nucleon–nucleon pair √ s NN = 5 . 02 TeV with the ALICE detector. The results are more precise, more differential in centrality, and reach much lower transverse momentum ( p T = 1 GeV / c ) with respect to previous measurements performed by the ALICE, STAR, and CMS Collaborations in nucleus–nucleus collisions, allowing for an extrapolation down to p T = 0. The p T -differential (cid:2) + c / D 0 ratio is enhanced with respect to the pp measurement for 4 < p T < 8 GeV / c by 3.7 standard deviations ( σ ), while the p T -integrated ratios are compatible within 1 σ . The observed trend is similar to that observed in the strange sector for the (cid:2) / K 0S ratio. Model calculations including coalescence or statistical hadronization for charm-hadron formation are compared with the data. © 2023 European Organization for Nuclear Research. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP 3 .
2 citations
TL;DR: In this article , a new observable for correlations between symmetry planes, which characterize the direction of the anisotropic emission of produced particles, is measured in Pb-Pb collisions at 2.76 TeV with ALICE.
Abstract: Abstract A newly developed observable for correlations between symmetry planes, which characterize the direction of the anisotropic emission of produced particles, is measured in Pb–Pb collisions at $$\sqrt{s_\text {NN}}$$ s NN = 2.76 TeV with ALICE. This so-called Gaussian Estimator allows for the first time the study of these quantities without the influence of correlations between different flow amplitudes. The centrality dependence of various correlations between two, three and four symmetry planes is presented. The ordering of magnitude between these symmetry plane correlations is discussed and the results of the Gaussian Estimator are compared with measurements of previously used estimators. The results utilizing the new estimator lead to significantly smaller correlations than reported by studies using the Scalar Product method. Furthermore, the obtained symmetry plane correlations are compared to state-of-the-art hydrodynamic model calculations for the evolution of heavy-ion collisions. While the model predictions provide a qualitative description of the data, quantitative agreement is not always observed, particularly for correlators with significant non-linear response of the medium to initial state anisotropies of the collision system. As these results provide unique and independent information, their usage in future Bayesian analysis can further constrain our knowledge on the properties of the QCD matter produced in ultrarelativistic heavy-ion collisions.
TL;DR: The first direct measurement of the three-body nuclear forces at the LHC was presented in this paper , where three-particle cumulants were extracted from the correlation functions by applying the Kubo formalism, where the threeparticle interaction contribution to these correlations were isolated after subtracting the known two-body interaction terms.
Abstract: Abstract Three-body nuclear forces play an important role in the structure of nuclei and hypernuclei and are also incorporated in models to describe the dynamics of dense baryonic matter, such as in neutron stars. So far, only indirect measurements anchored to the binding energies of nuclei can be used to constrain the three-nucleon force, and if hyperons are considered, the scarce data on hypernuclei impose only weak constraints on the three-body forces. In this work, we present the first direct measurement of the p–p–p and p–p– $$\Lambda $$ Λ systems in terms of three-particle correlation functions carried out for pp collisions at $$\sqrt{s} = 13$$ s = 13 TeV. Three-particle cumulants are extracted from the correlation functions by applying the Kubo formalism, where the three-particle interaction contribution to these correlations can be isolated after subtracting the known two-body interaction terms. A negative cumulant is found for the p–p–p system, hinting to the presence of a residual three-body effect while for p–p– $$\Lambda $$ Λ the cumulant is consistent with zero. This measurement demonstrates the accessibility of three-baryon correlations at the LHC.
TL;DR: In this article , the authors presented measurements of the groomed jet radius and momentum splitting fraction in pp collisions at 5.02$ TeV with the ALICE detector at the Large Hadron Collider.
Abstract: This article presents measurements of the groomed jet radius and momentum splitting fraction in pp collisions at $\sqrt{s}=5.02$ TeV with the ALICE detector at the Large Hadron Collider. Inclusive charged-particle jets are reconstructed at midrapidity using the anti-$k_{\rm{T}}$ algorithm for transverse momentum $60< p_{\mathrm{T}}^{\rm{ch\; jet}}<80$ GeV/$c$. We report results using two different grooming algorithms: soft drop and, for the first time, dynamical grooming. For each grooming algorithm, a variety of grooming settings are used in order to explore the impact of collinear radiation on these jet substructure observables. These results are compared to perturbative calculations that include resummation of large logarithms at all orders in the strong coupling constant. We find good agreement of the theoretical predictions with the data for all grooming settings considered.
TL;DR: In this article , two-particle correlations were studied in the transverse momentum range of the Pb-Pb collision at a centre-of-mass energy per-nucleon (COME) detector.
Abstract: Abstract Two-particle correlations with $$\textrm{K}^{0}_\mathrm{{S}}$$ K S 0 , $$\Lambda $$ Λ / $$\overline{\Lambda }$$ Λ ¯ , and charged hadrons as trigger particles in the transverse momentum range $$8{<}p_{{\textrm{T}},{\textrm{trig}}}{<}16$$ 8 < p T , trig < 16 GeV/ $$c$$ c , and associated charged particles within $$1{<}p_{{\textrm{T}},{\textrm{assoc}}}{<}8$$ 1 < p T , assoc < 8 GeV/ $$c$$ c , are studied at midrapidity in pp and central Pb–Pb collisions at a centre-of-mass energy per nucleon–nucleon collision $$\sqrt{s_{\textrm{NN}}}~=~5.02$$ s NN = 5.02 TeV with the ALICE detector at the LHC. After subtracting the contributions of the flow background, the per-trigger yields are extracted on both the near and away sides, and the ratio in Pb–Pb collisions with respect to pp collisions ( $$I_{\textrm{AA}}$$ I AA ) is computed. The per-trigger yield in Pb–Pb collisions on the away side is strongly suppressed to the level of $$I_{\textrm{AA}}$$ I AA $$\approx 0.6$$ ≈ 0.6 for $$p_{{\textrm{T}},{\textrm{assoc}}}>3$$ p T , assoc > 3 GeV/ $$c$$ c as expected from strong in-medium energy loss, while an enhancement develops at low $$p_{{\textrm{T}},{\textrm{assoc}}}$$ p T , assoc on both the near and away sides, reaching $$I_{\textrm{AA}}$$ I AA $$\approx 1.8$$ ≈ 1.8 and 2.7 respectively. These findings are in good agreement with previous ALICE measurements from two-particle correlations triggered by neutral pions ( $$\pi ^{0}$$ π 0 –h) and charged hadrons (h–h) in Pb–Pb collisions at $$\sqrt{s_{\textrm{NN}}}~=~2.76$$ s NN = 2.76 TeV. Moreover, the correlations with $$\textrm{K}^{0}_\mathrm{{S}}$$ K S 0 mesons and $$\Lambda $$ Λ / $$\overline{\Lambda }$$ Λ ¯ baryons as trigger particles are compared to those of inclusive charged hadrons. The results are compared with the predictions of Monte Carlo models.
TL;DR: In this paper , the first measurement of the TeV with the ALICE detector is presented in this paper, where the resonances are reconstructed via their hadronic decay channel via their decay channel.
Abstract: Abstract Hadronic resonances are used to probe the hadron gas produced in the late stage of heavy-ion collisions since they decay on the same timescale, of the order of 1–10 fm/ c , as the decoupling time of the system. In the hadron gas, (pseudo)elastic scatterings among the products of resonances that decayed before the kinetic freeze-out and regeneration processes counteract each other, the net effect depending on the resonance lifetime, the duration of the hadronic phase, and the hadronic cross sections at play. In this context, the $$\Sigma (1385)^{\pm }$$ Σ ( 1385 ) ± particle is of particular interest as models predict that regeneration dominates over rescattering despite its relatively short lifetime of about 5.5 fm/ c . The first measurement of the $$\Sigma (1385)^{\pm }$$ Σ ( 1385 ) ± resonance production at midrapidity in Pb–Pb collisions at $$\sqrt{s_{\textrm{NN}}}= 5.02$$ s NN = 5.02 TeV with the ALICE detector is presented in this Letter. The resonances are reconstructed via their hadronic decay channel, $$\Lambda \pi $$ Λ π , as a function of the transverse momentum ( $$p_\textrm{T}$$ p T ) and the collision centrality. The results are discussed in comparison with the measured yield of pions and with expectations from the statistical hadronization model as well as commonly employed event generators, including PYTHIA8/Angantyr and EPOS3 coupled to the UrQMD hadronic cascade afterburner. None of the models can describe the data. For $$\Sigma (1385)^{\pm }$$ Σ ( 1385 ) ± , a similar behaviour as $$\textrm{K}^{*} (892)^{0}$$ K ∗ ( 892 ) 0 is observed in data unlike the predictions of EPOS3 with afterburner.
TL;DR: In this article , the production of the W$^\pm$ bosons measured in p$-$Pb collisions at a center-of-mass energy per nucleon = 8.16$ TeV with ALICE at the LHC is presented.
Abstract: The production of the W$^\pm$ bosons measured in p$-$Pb collisions at a centre-of-mass energy per nucleon$-$nucleon collision $\sqrt{s_{NN}} = 8.16$ TeV and Pb$-$Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV with ALICE at the LHC is presented. The W$^\pm$ bosons are measured via their muonic decay channel, with the muon reconstructed in the pseudorapidity region $-4 < \eta^\mu_{\rm lab} < -2.5$ with transverse momentum $p_{\rm T}^\mu > 10$ GeV/$c$. While in Pb$-$Pb collisions the measurements are performed in the forward ($2.5 < y^\mu_{\rm cms} < 4$) rapidity region, in p$-$Pb collisions, where the centre-of-mass frame is boosted with respect to the laboratory frame, the measurements are performed in the backward ($-4.46 < y^\mu_{\rm cms} < -2.96$) and forward ($2.03 < y^\mu_{\rm cms} < 3.53$) rapidity regions. The W$^{-}$ and W$^{+}$ production cross sections, lepton-charge asymmetry, and nuclear modification factors are evaluated as a function of the muon rapidity. In order to study the production as a function of the p$-$Pb collision centrality, the production cross sections of the W$^{-}$ and W$^{+}$ bosons are combined and normalised to the average number of binary nucleon$-$nucleon collision $\langle N_\mathrm{coll} \rangle$. In Pb$-$Pb collisions, the same measurements are presented as a function of the collision centrality. Study of the binary scaling of the W$^\pm$-boson cross sections in p$-$Pb and Pb$-$Pb collisions is also reported. The results are compared with perturbative QCD (pQCD) calculations, with and without nuclear modifications of the Parton Distribution Functions (PDFs), as well as with available data at the LHC. Significant deviations from the theory expectations are found in the two collision systems, indicating that the measurements can provide additional constraints for the determination of nuclear PDF (nPDFs) and in particular of the light-quark distributions.
TL;DR: In this article , the transverse-momentum of a nucleon-nucleon collision was measured with the ALICE detector up to 16 GeV/c in the rapidity range.
Abstract: Abstract The transverse-momentum $$(p_{\textrm{T}})$$ ( p T ) spectra of K $$^{*}(892)^{0}~$$ ∗ ( 892 ) 0 and $$\mathrm {\phi (1020)}~$$ ϕ ( 1020 ) measured with the ALICE detector up to $$p_{\textrm{T}} $$ p T = 16 GeV/ c in the rapidity range $$-1.2< y < 0.3,$$ - 1.2 < y < 0.3 , in p–Pb collisions at the center-of-mass energy per nucleon–nucleon collision $$\sqrt{s_{\textrm{NN}}} = 5.02$$ s NN = 5.02 TeV are presented as a function of charged particle multiplicity and rapidity. The measured $$p_{\textrm{T}} $$ p T distributions show a dependence on both multiplicity and rapidity at low $$p_{\textrm{T}} $$ p T whereas no significant dependence is observed at high $$p_{\textrm{T}} $$ p T . A rapidity dependence is observed in the $$p_{\textrm{T}} $$ p T -integrated yield (d N /d y ), whereas the mean transverse momentum $$\left( \langle p_{\textrm{T}} \rangle \right) $$ ⟨ p T ⟩ shows a flat behavior as a function of rapidity. The rapidity asymmetry ( $$Y_{\textrm{asym}}$$ Y asym ) at low $$p_{\textrm{T}} $$ p T (< 5 GeV/ c ) is more significant for higher multiplicity classes. At high $$p_{\textrm{T}} $$ p T , no significant rapidity asymmetry is observed in any of the multiplicity classes. Both K $$^{*}(892)^{0}~$$ ∗ ( 892 ) 0 and $$\mathrm {\phi (1020)}~$$ ϕ ( 1020 ) show similar $$Y_{\textrm{asym}}$$ Y asym . The nuclear modification factor $$(Q_{\textrm{CP}})$$ ( Q CP ) as a function of $$p_{\textrm{T}} $$ p T shows a Cronin-like enhancement at intermediate $$p_{\textrm{T}} $$ p T , which is more prominent at higher rapidities (Pb-going direction) and in higher multiplicity classes. At high $$p_{\textrm{T}}$$ p T (> 5 GeV/ $$c$$ c ), the $$Q_{\textrm{CP}}$$ Q CP values are greater than unity and no significant rapidity dependence is observed.
TL;DR: In this paper , the authors measured particle transverse momentum spectra as a function of R T in different topological regions of the events and found that the yield of high-transverse momentum particles relative to the R T -integrated measurement decreases with increasing R T, indicating that the softer particle production as R T increases and validating that R T can be used to control the magnitude of the UE.
Abstract: A bstract The production of π ± , K ± , and $$ \left(\overline{\textrm{p}}\right)\textrm{p} $$ p ¯ p is measured in pp collisions at $$ \sqrt{s} $$ s = 13 TeV in different topological regions of the events. Particle transverse momentum ( p T ) spectra are measured in the “toward”, “transverse”, and “away” angular regions defined with respect to the direction of the leading particle in the event. While the toward and away regions contain the fragmentation products of the near-side and away-side jets, respectively, the transverse region is dominated by particles from the Underlying Event (UE). The relative transverse activity classifier, R T = N T /〈 N T 〉, is used to group events according to their UE activity, where N T is the measured charged-particle multiplicity per event in the transverse region and 〈 N T 〉 is the mean value over all the analysed events. The first measurements of identified particle p T spectra as a function of R T in the three topological regions are reported. It is found that the yield of high transverse momentum particles relative to the R T -integrated measurement decreases with increasing R T in both the toward and the away regions, indicating that the softer UE dominates particle production as R T increases and validating that R T can be used to control the magnitude of the UE. Conversely, the spectral shapes in the transverse region harden significantly with increasing R T . This hardening follows a mass ordering, being more significant for heavier particles. Finally, it is observed that the p T -differential particle ratios $$ \left(\textrm{p}+\overline{\textrm{p}}\right)/\left({\uppi}^{+}+{\uppi}^{-}\right) $$ p + p ¯ / π + + π − and (K + + K − ) / ( π + + π − ) in the low UE limit ( R T → 0) approach expectations from Monte Carlo generators such as PYTHIA 8 with Monash 2013 tune and EPOS LHC, where the jet-fragmentation models have been tuned to reproduce e + e − results.
TL;DR: The first measurements of elliptic flow of π ± , K ± , $$ \textrm{p}+\overline{p}} $$ as mentioned in this paper
Abstract: A bstract The first measurements of elliptic flow of π ± , K ± , $$ \textrm{p}+\overline{\textrm{p}} $$ p + p ¯ , $$ {\textrm{K}}_{\textrm{S}}^0 $$ K S 0 , $$ \Lambda +\overline{\Lambda} $$ Λ + Λ ¯ , ϕ , $$ {\Xi}^{-}+{\overline{\Xi}}^{+} $$ Ξ − + Ξ ¯ + , and $$ {\varOmega}^{-}+{\overline{\varOmega}}^{+} $$ Ω − + Ω ¯ + using multiparticle cumulants in Pb–Pb collisions at $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 5 . 02 TeV are resented. Results obtained with two- ( v 2 {2}) and four-particle cumulants ( v 2 {4}) are shown as a function of transverse momentum, p T , for various collision centrality intervals. Combining the data for both v 2 {2} and v 2 {4} also allows us to report the first measurements of the mean elliptic flow, elliptic flow fluctuations, and relative elliptic flow fluctuations for various hadron species. These observables probe the event-by-event eccentricity fluctuations in the initial state and the contributions from the dynamic evolution of the expanding quark–gluon plasma. The characteristic features observed in previous p T -differential anisotropic flow measurements for identified hadrons with two-particle correlations, namely the mass ordering at low p T and the approximate scaling with the number of constituent quarks at intermediate p T , are similarly present in the four-particle correlations and the combinations of v 2 {2} and v 2 {4}. In addition, a particle species dependence of flow fluctuations is observed that could indicate a significant contribution from final state hadronic interactions. The comparison between experimental measurements and CoLBT model calculations, which combine the various physics processes of hydrodynamics, quark coalescence, and jet fragmentation, illustrates their importance over a wide p T range.
TL;DR: In this paper , a newly developed observable for correlations between symmetry planes, which characterize the direction of the anisotropic emission of produced particles, is measured in Pb-Pb collisions at √ s NN = 2.76 TeV with ALICE.
Abstract: A newly developed observable for correlations between symmetry planes, which characterize the direction of the anisotropic emission of produced particles, is measured in Pb–Pb collisions at √ s NN = 2.76 TeV with ALICE. This so-called Gaussian Estimator allows for the first time the study of these quantities without the influence of correlations between different flow amplitudes. The centrality dependence of various correlations between two, three and four symmetry planes is presented. The ordering of magnitude between these symmetry plane correlations is discussed and the results of the Gaussian Estimator are compared with measurements of previously used estimators. The results utilizing the new estimator lead to significantly smaller correlations than reported by studies using the Scalar Product method. Furthermore, the obtained symmetry plane correlations are compared to state-of-the-art hydrodynamic model calculations for the evolution of heavy-ion collisions. While the model predictions provide a qualitative description of the data, quantitative agreement is not always observed, particularly for correlators with significant non-linear response of the medium to initial state anisotropies of the collision system. As these results provide unique and independent information, their usage in future Bayesian analysis can further constrain our knowledge on the properties of the QCD matter produced in ultrarelativistic heavy-ion collisions.
TL;DR: In this paper , the authors measured the fraction of transverse momentum carried by subjets of radius $r$ within jets of radius$R$. Charged-particle jets are reconstructed at midrapidity using the anti-$k_{\rm{T}}$ algorithm with jet radius $R=0.4$ and subjet is reconstructed by reclustering the jet constituents using the ant-$k{T} algorithm with radii $r= 0.1$ and
Abstract: This article presents new measurements of the fragmentation properties of jets in both proton-proton (pp) and heavy-ion collisions with the ALICE experiment at the LHC. We report distributions of the fraction $z_r$ of transverse momentum carried by subjets of radius $r$ within jets of radius $R$. Charged-particle jets are reconstructed at midrapidity using the anti-$k_{\rm{T}}$ algorithm with jet radius $R=0.4$, and subjets are reconstructed by reclustering the jet constituents using the anti-$k_{\rm{T}}$ algorithm with radii $r=0.1$ and $r=0.2$. In pp collisions, we measure both the inclusive and leading subjet distributions. We compare these measurements to perturbative calculations at next-to-leading logarithmic accuracy, which suggest a large impact of threshold resummation and hadronization effects on the $z_r$ distribution. In heavy-ion collisions, we measure the leading subjet distributions, which allow access to a region of harder jet fragmentation than has been probed by previous measurements of jet quenching via hadron fragmentation distributions. The $z_r$ distributions enable extraction of the parton-to-subjet fragmentation function and allow for tests of the universality of jet fragmentation functions in the quark-gluon plasma (QGP). We find no significant modification of $z_r$ distributions in Pb-Pb compared to pp collisions. However, the distributions are also consistent with a hardening trend for $z_r<0.95$, as predicted by several jet quenching models. As $z_r \rightarrow 1$ our results indicate that any such hardening effects cease, exposing qualitatively new possibilities to disentangle competing jet quenching mechanisms. By comparing our results to theoretical calculations based on an independent extraction of the parton-to-jet fragmentation function, we find consistency with the universality of jet fragmentation and no indication of factorization breaking in the QGP.
TL;DR: In this article , a production of inclusive charmonia in pp collisions at center-of-mass energy of 12 TeV was studied as a function of charged-particle pseudorapidity density with ALICE, where ground and excited charmonium states (J/ψ , ψ (2S)) were measured from their dimuon decays in the interval of rapidity in the center-ofthe-mass frame.
Abstract: A bstract Production of inclusive charmonia in pp collisions at center-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV and p–Pb collisions at center-of-mass energy per nucleon pair of $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 8 . 16 TeV is studied as a function of charged-particle pseudorapidity density with ALICE. Ground and excited charmonium states ( J/ψ , ψ (2S)) are measured from their dimuon decays in the interval of rapidity in the center-of-mass frame 2 . 5 < y cms < 4 . 0 for pp collisions, and 2 . 03 < y cms < 3 . 53 and −4 . 46 < y cms < −2 . 96 for p–Pb collisions. The charged-particle pseudorapidity density is measured around midrapidity (| η | < 1 . 0). In pp collisions, the measured charged-particle multiplicity extends to about six times the average value, while in p-Pb collisions at forward (backward) rapidity a multiplicity corresponding to about three (four) times the average is reached. The ψ (2S) yield increases with the charged-particle pseudorapidity density. The ratio of ψ (2S) over J/ψ yield does not show a significant multiplicity dependence in either colliding system, suggesting a similar behavior of J/ψ and ψ (2S) yields with respect to charged-particle pseudorapidity density. Results for the ψ (2S) yield and its ratio with respect to J/ψ agree with available model calculations.
TL;DR: In this paper , the underlying event associated with hard scatterings at mid-pseudorapidity (|η|<0.8) in pp, p-Pb, and pb-pb collisions at centre-of-mass energy per nucleon pair, sNN=5.02 TeV, was characterized with ALICE at the LHC.
TL;DR: In this paper , the first measurement of the TeV with the ALICE detector is presented in this paper, where the resonances are reconstructed via their hadronic decay channel via their decay channel.
Abstract: Abstract Hadronic resonances are used to probe the hadron gas produced in the late stage of heavy-ion collisions since they decay on the same timescale, of the order of 1–10 fm/ c , as the decoupling time of the system. In the hadron gas, (pseudo)elastic scatterings among the products of resonances that decayed before the kinetic freeze-out and regeneration processes counteract each other, the net effect depending on the resonance lifetime, the duration of the hadronic phase, and the hadronic cross sections at play. In this context, the $$\Sigma (1385)^{\pm }$$ Σ ( 1385 ) ± particle is of particular interest as models predict that regeneration dominates over rescattering despite its relatively short lifetime of about 5.5 fm/ c . The first measurement of the $$\Sigma (1385)^{\pm }$$ Σ ( 1385 ) ± resonance production at midrapidity in Pb–Pb collisions at $$\sqrt{s_{\textrm{NN}}}= 5.02$$ s NN = 5.02 TeV with the ALICE detector is presented in this Letter. The resonances are reconstructed via their hadronic decay channel, $$\Lambda \pi $$ Λ π , as a function of the transverse momentum ( $$p_\textrm{T}$$ p T ) and the collision centrality. The results are discussed in comparison with the measured yield of pions and with expectations from the statistical hadronization model as well as commonly employed event generators, including PYTHIA8/Angantyr and EPOS3 coupled to the UrQMD hadronic cascade afterburner. None of the models can describe the data. For $$\Sigma (1385)^{\pm }$$ Σ ( 1385 ) ± , a similar behaviour as $$\textrm{K}^{*} (892)^{0}$$ K ∗ ( 892 ) 0 is observed in data unlike the predictions of EPOS3 with afterburner.
TL;DR: In this article , the properties of the underlying event measured with ALICE at the LHC in pp and p-Pb collisions were reported, quantified by charged-particle number and summed-p T densities.
Abstract: A bstract We report about the properties of the underlying event measured with ALICE at the LHC in pp and p–Pb collisions at $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 5 . 02 TeV. The event activity, quantified by charged-particle number and summed- p T densities, is measured as a function of the leading-particle transverse momentum $$ \left({p}_{\textrm{T}}^{\textrm{trig}}\right) $$ p T trig . These quantities are studied in three azimuthal-angle regions relative to the leading particle in the event: toward, away, and transverse. Results are presented for three different p T thresholds (0.15, 0.5 and 1 GeV/ c ) at mid-pseudorapidity (| η | < 0 . 8). The event activity in the transverse region, which is the most sensitive to the underlying event, exhibits similar behaviour in both pp and p–Pb collisions, namely, a steep increase with $$ {p}_{\textrm{T}}^{\textrm{trig}} $$ p T trig for low $$ {p}_{\textrm{T}}^{\textrm{trig}} $$ p T trig , followed by a saturation at $$ {p}_{\textrm{T}}^{\textrm{trig}}\approx 5 $$ p T trig ≈ 5 GeV/ c . The results from pp collisions are compared with existing measurements at other centre-of-mass energies. The quantities in the toward and away regions are also analyzed after the subtraction of the contribution measured in the transverse region. The remaining jet-like particle densities are consistent in pp and p–Pb collisions for $$ {p}_{\textrm{T}}^{\textrm{trig}}>10 $$ p T trig > 10 GeV/ c , whereas for lower $$ {p}_{\textrm{T}}^{\textrm{trig}} $$ p T trig values the event activity is slightly higher in p–Pb than in pp collisions. The measurements are compared with predictions from the PYTHIA 8 and EPOS LHC Monte Carlo event generators.
TL;DR: The AEg̅IS collaboration at CERN's AD produces antihydrogen atoms in the form of a pulsed, isotropic source with a precisely defined formation time as mentioned in this paper .
Abstract: The AEg̅IS collaboration at CERN’s AD produces antihydrogen atoms in the form of a pulsed, isotropic source with a precisely defined formation time. AEg̅IS has recently undergone major upgrades to fully benefit from the increased number of colder antiprotons provided by the new ELENA decelerator and to move toward forming a horizontal beam to directly investigate the influence of gravity on the H̅ atoms, thereby probing the Weak Equivalence Principle for antimatter. This contribution gives an overview of these upgrades as well as subsequent results from the first beam times with ELENA.
TL;DR: In this article , femtoscopic correlations of non-identical charged kaons are studied in Pb$-$Pb collisions at a center-of-mass energy per nucleon$-$nucleon collision $\sqrt{s_{\mathrm{NN}}} =2.76$ TeV by ALICE at the LHC.
Abstract: Femtoscopic correlations of non-identical charged kaons ($\rm K^+ K^-$) are studied in Pb$-$Pb collisions at a center-of-mass energy per nucleon$-$nucleon collision $\sqrt{s_{\mathrm{NN}}} =2.76$ TeV by ALICE at the LHC. One-dimensional $\rm K^+ K^-$ correlation functions are analyzed in three centrality classes and eight intervals of particle-pair transverse momentum. The Lednick\'y and Luboshitz interaction model used in the $\rm K^+ K^-$ analysis includes the final-state Coulomb interactions between kaons and the final-state interaction through $a_{0}$(980) and $f_{0}$(980) resonances. The mass of $f_{0}$(980) and coupling were extracted from the fit to $\rm K^+ K^-$ correlation functions using the femtoscopic technique. The measured mass and width of the $f_{0}$(980) resonance are consistent with other published measurements. The height of the $\phi$(1020) meson peak present in the $\rm K^+ K^-$ correlation function rapidly decreases with increasing source radius, qualitatively in agreement with an inverse volume dependence. A phenomenological fit to this trend suggests that the $\phi$(1020) meson yield is dominated by particles produced directly from the hadronization of the system. The small fraction subsequently produced by final-state interactions could not be precisely quantified with data presented in this paper and will be assessed in future work.
TL;DR: The first systematic comparison of the charged-particle pseudorapidity densities for three widely different collision systems, pp, pPb and PbPb, at the top energy of the Large Hadron Collider (sNN=5.02TeV) was presented in this paper .
TL;DR: The measurement of the production of charm jets, identified by the presence of a D 0 meson in the jet constituents, is presented in proton-proton collisions at centre-of-mass energies of 5.02 and 13 TeV with the ALICE detector at the CERN LHC as mentioned in this paper .
Abstract: A bstract The measurement of the production of charm jets, identified by the presence of a D 0 meson in the jet constituents, is presented in proton–proton collisions at centre-of-mass energies of $$ \sqrt{s} $$ s = 5.02 and 13 TeV with the ALICE detector at the CERN LHC. The D 0 mesons were reconstructed from their hadronic decay D 0 → K − π + and the respective charge conjugate. Jets were reconstructed from D 0 -meson candidates and charged particles using the anti- k T algorithm, in the jet transverse momentum range 5 < p T , chjet < 50 GeV/ c , pseudorapidity | η jet | < 0 . 9 − R , and with the jet resolution parameters R = 0 . 2 , 0 . 4 , 0 . 6. The distribution of the jet momentum fraction carried by a D 0 meson along the jet axis $$ \left({z}_{\Big\Vert}^{\textrm{ch}}\right) $$ z ‖ ch was measured in the range 0 . 4 < $$ {z}_{\Big\Vert}^{\textrm{ch}} $$ z ‖ ch < 1 . 0 in four ranges of the jet transverse momentum. Comparisons of results for different collision energies and jet resolution parameters are also presented. The measurements are compared to predictions from Monte Carlo event generators based on leading-order and next-to-leading-order perturbative quantum chromodynamics calculations. A generally good description of the main features of the data is obtained in spite of a few discrepancies at low p T , chjet . Measurements were also done for R = 0 . 3 at $$ \sqrt{s} $$ s = 5 . 02 and are shown along with their comparisons to theoretical predictions in an appendix to this paper.