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A<sc>bstract</sc> The first measurement at midrapidity (|y|<0.5) of the production yield of the strange-charm baryons$${\Xi }_{\text{c}}^{+}$$and$${\Xi }_{\text{c}}^{0}$$as a function of transverse momentum (pT) in different charged-particle multiplicity classes in proton-proton collisions at$$\sqrt{s}=13$$TeV with the ALICE experiment at the LHC is reported. The$${\Xi }_{\text{c}}^{+}$$baryon is reconstructed via the$${\Xi }_{\text{c}}^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+}$$decay channel in the range 4< pT<12 GeV/c, while the$${\Xi }_{\text{c}}^{0}$$baryon is reconstructed via both the$${\Xi}_{\text{c}}^{0}\to {\Xi}^{-}{\pi }^{+}$$and$${\Xi}_{\text{c}}^{0}\to {\Xi}^{-}{\text{e}}^{+}{\nu }_{\text{e}}$$decay channels in the range 2< pT<12 GeV/c. The baryon-to-meson$$\left({\Xi}_{\text{c}}^{0,+}/{\text{D}}^{0}\right)$$and the baryon-to-baryon$$\left({\Xi}_{\text{c}}^{0,+}/{\Lambda}_{\text{c}}^{+}\right)$$production yield ratios show no significant dependence on multiplicity. In addition, the observed yield ratios are not described by theoretical predictions that model charm-quark fragmentation based on measurements at e+e−and e−p colliders, indicating differences in the charm-baryon production mechanism in pp collisions. A comparison with different event generators and tunings, including different modelling of the hadronisation process, is also discussed. Moreover, the branching-fraction ratio of$${\text{BR}}\left({\Xi}_{\text{c}}^{0}\to {\Xi }^{-}{\text{e}}^{+}{\nu }_{\text{e}}\right)/{\text{BR}}\left({\Xi}_{\text{c}}^{0}\to {\Xi }^{-}{\pi }^{+}\right)$$is measured as 0.825 ± 0.094 (stat.) ± 0.081 (syst.). This value supersedes the previous ALICE measurement, improving the statistical precision by a factor of 1.6.
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This content will become publicly available on November 1, 2026
Study of $$\langle {p}_{\text{T}}\rangle $$ and its higher moments, and extraction of the speed of sound in Pb-Pb collisions with ALICE
A<sc>bstract</sc> Ultrarelativistic heavy-ion collisions produce a state of hot and dense strongly interacting QCD matter called quark-gluon plasma (QGP). On an event-by-event basis, the volume of the QGP in ultracentral collisions is mostly constant, while its total entropy can vary significantly due to quantum fluctuations, leading to variations in the temperature of the system. Exploiting this unique feature of ultracentral collisions allows for the interpretation of the correlation of the mean transverse momentum$$(\langle {p}_{\text{T}}\rangle )$$of produced charged hadrons and the number of charged hadrons as a measure for the speed of sound,cs. This speed is related to the rate at which compression waves travel in the QGP and is determined by fitting the relative increase in$$\langle {p}_{\text{T}}\rangle $$with respect to the relative change in the average charged-particle density$$(\langle \text{d}{N}_{\text{ch}}/\text{d}\eta \rangle )$$measured at mid-rapidity. This study reports the event-average$$\langle {p}_{\text{T}}\rangle $$of charged particles as well as the variance, skewness, and kurtosis of the event-by-event transverse momentum per charged particle$$([{p}_{\text{T}}])$$distribution in ultracentral Pb-Pb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair using the ALICE detector. Different centrality estimators based on charged-particle multiplicity or the transverse energy of the event are used to select ultracentral collisions. By ensuring a pseudorapidity gap between the region used to define the centrality and the region used to perform the measurement, the influence of biases and their potential effects on the rise of the mean transverse momentum is tested. The measured$${c}_{\text{s}}^{2}$$is found to strongly depend on the exploited centrality estimator and ranges between 0.1146±0.0028 (stat.)±0.0065 (syst.) and 0.4374±0.0006 (stat.)±0.0184 (syst.) in natural units. The self-normalized variance shows a steep decrease towards ultracentral collisions, while the self-normalized skewness variables show a maximum, followed by a fast decrease. These non-Gaussian features are understood in terms of the vanishing of the impact-parameter fluctuations contributing to the event-to-event [pT] distribution.
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- PAR ID:
- 10689730
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- https://link.springer.com
- Date Published:
- Journal Name:
- Journal of High Energy Physics
- Volume:
- 2025
- Issue:
- 11
- ISSN:
- 1029-8479
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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