More Like this

1. Searching for the QCD critical point through constant entropy density contours

   https://doi.org/10.1051/epjconf/202636415007  

   Shah, Hitansh; Hippert, Mauricio; Noronha, Jorge; Ratti, Claudia; Vovchenko, Volodymyr (January 2026, EPJ Web of Conferences)

   We propose a novel method to locate the QCD critical point by constructing an expansion along contours of constant entropy density. Applying two independent analyses of lattice QCD data at zero baryon chemical potential, we find a critical point atT_c=114 ± 7 MeV andμ_Bc= 602±62 MeV for an expansion truncated at orderμ_B². This approach is consistent with recent lattice QCD results up toμ_B/T≤ 3. A more precise determination of the required expansion coefficients from lattice simulations will be essential for reliably establishing the location of the QCD critical endpoint. 

   more » « less
2. Locating the QCD critical point through contours of constant entropy density

   https://doi.org/10.1103/cbwj-4jfl  

   Shah, Hitansh; Hippert, Mauricio; Noronha, Jorge; Ratti, Claudia; Vovchenko, Volodymyr (January 2026, Physical Review C)

   We propose a new method to investigate the existence and location of the conjectured high-temperature critical point of strongly interacting matter via contours of constant entropy density. By approximating these lines as a power series in the baryon chemical potential ${\mu }_B$ , one can extrapolate them from first-principle results at zero net-baryon density, and use them to locate the quantum chromodynamics (QCD) critical point, including the associated first-order and spinodal lines. As a proof of principle, we employ currently available continuum-extrapolated lattice data from the Wuppertal-Budapest collaboration to find a critical point at a temperature and a baryon chemical potential of $T_c=114.3\pm 6.9$ MeV and ${\mu }_{B,c}=602.1\pm 62.1$ MeV, respectively, at expansion order $\mathcal{O}\left({\mu }_B^2\right)$ . We advocate for a more precise determination of the required expansion coefficients via lattice QCD simulations as a means of pinpointing the location of the critical endpoint in the phase diagram of strongly interacting matter. 

   more » « less
3. Calculating QCD Phase Diagram Trajectories of Nuclear Collisions using a Semi-analytical Model

   https://doi.org/10.1051/epjconf/202327601012  

   Mendenhall, Todd; Lin, Zi-Wei (January 2023, EPJ Web of Conferences)

   Kim, Y.; Moon, D.H. (Ed.)

   At low to moderate collision energies where the parton formation time τ F is not small compared to the nuclear crossing time, the finite nuclear thickness significantly affects the energy density ϵ( t ) and net conserved-charge densities such as the net-baryon density n B ( t ) produced in heavy ion collisions. As a result, at low to moderate energies the trajectory in the QCD phase diagram is also affected by the finite nuclear thickness. Here, we first discuss our semi-analytical model and its results on ϵ( f ), n R ( t ), n Q ( t ), and n s ( t ) in central Au+Au collisions. We then compare the T ( t ), μ B ( t ), μ Q ( t ), and μ S ( t ) extracted with the ideal gas equation of state (EoS) with quantum statistics to those extracted with a lattice QCD-based EoS. We also compare the T -μ B trajectories with the RHIC chemical freezeout data. Finally, we discuss the effect of transverse flow on the trajectories. 

   more » « less
4. QCD equation of state with improved precision from lattice simulations

   https://doi.org/10.1051/epjconf/202429614007  

   Parotto, Paolo; Borsányi, Szabolcs; Fodor, Zoltan; Guenther, Jana N; Kara, Ruben; Pásztor, Attila; Ratti, Claudia; Szabó, Kalman K (January 2024, EPJ Web of Conferences)

   Bellwied, R; Geurts, F; Rapp, R; Ratti, C; Timmins, A; Vitev, I (Ed.)

   The equation of state of Quantum Chromodynamics has been in recent years the focus of intense effort from first principle methods, mostly lattice simulations, with particular interest to the finite baryon density regime. Because of the sign problem, various extrapolation methods have been used to reconstruct bulk properties of the theory up to as far asμ_B=T≃ 3:5. However, said efforts rely on the equation of state at vanishing baryon density as an integration constant, which up toμ_B=T≃ 2 - 2:5 proves to be the dominant source of uncertainty at the level of precision currently available. In this contribution we present the update of our equation of state at zero net baryon density from 2014, performing a continuum limit from lattices with Nτ = 8; 10; 12; 16. We show how the improved precision is translated in a lower uncertainty on the extrapolated equation of state at finite chemical potential. 

   more » « less
5. Observation of a $$ {\varLambda}_b^0 $$ − $$ {\overline{\varLambda}}_b^0 $$ production asymmetry in proton-proton collisions at $$ \sqrt{s} $$ = 7 and 8 TeV

   https://doi.org/10.1007/JHEP10(2021)060  

   Aaij, R.; Abdelmotteleb, A. S.; Abellán Beteta, C.; Ackernley, T.; Adeva, B.; Adinolfi, M.; Afsharnia, H.; Aidala, C. A.; Aiola, S.; Ajaltouni, Z.; et al (October 2021, Journal of High Energy Physics)

   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. 

   more » « less