A bstract This article presents differential measurements of the asymmetry between $$ {\varLambda}_b^0 $$ Λ b 0 and $$ {\overline{\varLambda}}_b^0 $$ Λ ¯ b 0 baryon production rates in proton-proton collisions at centre-of-mass energies of $$ \sqrt{s} $$ s = 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb − 1 . The $$ {\varLambda}_b^0 $$ Λ b 0 baryons are reconstructed through the inclusive semileptonic decay $$ {\varLambda}_b^0 $$ Λ b 0 → $$ {\varLambda}_c^{+} $$ Λ c + μ − $$ \overline{\nu} $$ ν ¯ μ X . The production asymmetry is measured both in intervals of rapidity in the range 2 . 15 < y < 4 . 10 and transverse momentum in 2 < p T < 27 GeV/ c . The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both $$ \sqrt{s} $$ s = 7 and 8 TeV data, assuming no CP violation in the decay. There is evidence for a trend as a function of rapidity with a significance of 4 standard deviations. Comparisons to predictions from hadronisation models in P ythia and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in b -hadron production at LHC energies.
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Shear viscosity at finite baryon densities
We use the excluded volume Hadron Resonance Gas (HRG) model with the most up-to-date hadron list to calculate η T/w at low temperatures and at finite baryon densities ρ B . This η T/w is then matched to a QCD-based shear viscosity calculation of the QGP for different profiles of η T/w across T,μ B including cross-over and critical point transitions. When compared to ideal hydrodynamic trajectories across T,μ B , we find that the η T/w (T,μ B ) profiles would require initial conditions at much larger baryon density to reach the same freeze-out point.
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- Award ID(s):
- 1654219
- NSF-PAR ID:
- 10336524
- Editor(s):
- David, G.; Garg, P.; Kalweit, A.; Mukherjee, S.; Ullrich, T.; Xu, Z.; Yoo, I.-K.
- Date Published:
- Journal Name:
- EPJ Web of Conferences
- Volume:
- 259
- ISSN:
- 2100-014X
- Page Range / eLocation ID:
- 13006
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1051/epjconf/202225913006
