We present a determination of freeze-out conditions in heavy ion collisions based on ratios of cumulants of net electric charge fluctuations. These ratios can reliably be calculated in lattice QCD ...for a wide range of chemical potential values by using a next-to-leading order Taylor series expansion around the limit of vanishing baryon, electric charge and strangeness chemical potentials. From a computation of up to fourth order cumulants and charge correlations we first determine the strangeness and electric charge chemical potentials that characterize freeze-out conditions in a heavy ion collision and confirm that in the temperature range 150 MeV ≤ T ≤ 170 MeV the hadron resonance gas model provides good approximations for these parameters that agree with QCD calculations on the 5%-15% level. We then show that a comparison of lattice QCD results for ratios of up to third order cumulants of electric charge fluctuations with experimental results allows us to extract the freeze-out baryon chemical potential and the freeze-out temperature.
Equation of state in ( 2 + 1 )-flavor QCD Bazavov, A.; Bhattacharya, Tanmoy; DeTar, C. ...
Physical review. D, Particles, fields, gravitation, and cosmology,
11/2014, Letnik:
90, Številka:
9
Journal Article
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We present results for the equation of state in (2 + 1)-flavor QCD using the highly improved staggered quark action and lattices with temporal extent N sub(tau) = 6, 8, 10, and 12. We show that these ...data can be reliably extrapolated to the continuum limit and obtain a number of thermodynamic quantities and the speed of sound in the temperature range 130-400 MeV. We compare our results with previous calculations and provide an analytic parameterization of the pressure, from which other thermodynamic quantities can be calculated, for use in phenomenology. We show that the energy density in the crossover region, 145 MeV < or = T < or = 163 MeV, defined by the chiral transition, is varepsilonc = (0.18-0.5) GeV /fm super(3), i.e., (1.2-3.1) varepsilon sub(nuclear). At high temperatures, we compare our results with resummed and dimensionally reduced perturbation theory calculations. As a byproduct of our analyses, we obtain the values of the scale parameters r sub(0) from the static quark potential and w sub(0) from the gradient flow.
We calculate the equation of state at high temperatures in 2+1 flavor QCD using the highly improved staggered quark (HISQ) action. We study the lattice spacing dependence of the pressure at high ...temperatures using lattices with temporal extent Nτ=6, 8, 10 and 12 and perform continuum extrapolations. We also give a continuum estimate for the equation of state up to temperatures T=2 GeV, which are then compared with results of the weak-coupling calculations. We find a reasonably good agreement with the weak-coupling calculations at the highest temperatures.
We present new results on up to sixth-order cumulants of net baryon-number fluctuations at small values of the baryon chemical potential, μ B , obtained in lattice QCD calculations with physical ...values of light and strange quark masses. Representing the Taylor expansions of higher-order cumulants in terms of the ratio of the two lowest-order cumulants, ... , allows for a parameter-free comparison with data on net proton-number cumulants obtained by the STAR Collaboration in the Beam Energy Scan at RHIC. We show that recent high-statistics data on skewness and kurtosis ratios of net proton-number distributions, obtained at a beam energy ... , agree well with lattice QCD results on cumulants of net baryon-number fluctuations close to the pseudocritical temperature, Tpc (μB) , for the chiral transition in QCD. We also present first results from a next-to-leading-order expansion of fifth- and sixth-order cumulants on the line of the pseudocritical temperatures.(ProQuest: ... denotes formulae omitted.)
Lattice gauge theories are fundamental to our understanding of high-energy physics. Nevertheless, the search for suitable platforms for their quantum simulation has proven difficult. We show that the ...Abelian Higgs model in 1+1 dimensions is a prime candidate for an experimental quantum simulation of a lattice gauge theory. To this end, we use a discrete tensor reformulation to smoothly connect the space-time isotropic version used in most numerical lattice simulations to the continuous-time limit corresponding to the Hamiltonian formulation. The eigenstates of the Hamiltonian are neutral for periodic boundary conditions, but we probe the nonzero charge sectors by introducing either a Polyakov loop or an external electric field. In both cases we obtain universal functions relating the mass gap, the gauge coupling, and the spatial size, which are invariant under the deformation of the temporal lattice spacing. We propose to use a physical multileg ladder of atoms trapped in optical lattices and interacting with Rydberg-dressed interactions to quantum simulate the model and check the universal features. Our results provide a path to the analog quantum simulation of lattice gauge theories with atoms in optical lattices.
We present lattice QCD results for mesonic screening masses in the temperature range 140 MeV ≲ T ≲ 2500 MeV. Our calculations were carried out using (2 + 1) flavors of the highly improved ...staggered quark action, with a physical value for the strange quark mass and two values of the light quark mass corresponding to pion masses of 160 and 140 MeV. Continuum-extrapolated results were obtained using calculations with a variety of lattice spacings corresponding to temporal lattice extents Nτ = 6 – 16 . We discuss the implications of these results for the effective restoration of various symmetries in the high temperature phase of QCD, as well as the approach toward the perturbative limit.
We study correlation functions of spatially separated static quark-antiquark pairs in (2+1)-flavor QCD in order to investigate onset and nature of color screening at high temperatures. We perform ...lattice calculations in a wide temperature range, 140≤T≤5814 MeV, using the highly improved staggered quark action and several lattice spacings to control discretization effects. By comparing at high temperatures our lattice results to weak-coupling calculations, as well as to the zero temperature result for the energy of a static quark-antiquark pair, we observe that color screening sets in at rT≈0.3. Furthermore, we also observe that in the range 0.3≲rT≲0.6 weak-coupling calculations in the framework of suitable effective field theories provide an adequate picture of color screening.
We compare lattice QCD results for appropriate combinations of net strangeness fluctuations and their correlations with net baryon number fluctuations with predictions from two hadron resonance gas ...(HRG) models having different strange hadron content. The conventionally used HRG model based on experimentally established strange hadrons fails to describe the lattice QCD results in the hadronic phase close to the QCD crossover. Supplementing the conventional HRG with additional, experimentally uncharted strange hadrons predicted by quark model calculations and observed in lattice QCD spectrum calculations leads to good descriptions of strange hadron thermodynamics below the QCD crossover. We show that the thermodynamic presence of these additional states gets imprinted in the yields of the ground-state strange hadrons leading to a systematic 5-8 MeV decrease of the chemical freeze-out temperatures of ground-state strange baryons.
We present results for pseudo-critical temperatures of QCD chiral crossovers at zero and non-zero values of baryon (B), strangeness (S), electric charge (Q), and isospin (I) chemical potentials ...μX=B,Q,S,I. The results were obtained using lattice QCD calculations carried out with two degenerate up and down dynamical quarks and a dynamical strange quark, with quark masses corresponding to physical values of pion and kaon masses in the continuum limit. By parameterizing pseudo-critical temperatures as Tc(μX)=Tc(0)1−κ2X(μX/Tc(0))2−κ4X(μX/Tc(0))4, we determined κ2X and κ4X from Taylor expansions of chiral observables in μX. We obtained a precise result for Tc(0)=(156.5±1.5) MeV. For analogous thermal conditions at the chemical freeze-out of relativistic heavy-ion collisions, i.e., μS(T,μB) and μQ(T,μB) fixed from strangeness-neutrality and isospin-imbalance, we found κ2B=0.012(4) and κ4B=0.000(4). For μB≲300 MeV, the chemical freeze-out takes place in the vicinity of the QCD phase boundary, which coincides with the lines of constant energy density of 0.42(6)GeV/fm3 and constant entropy density of 3.7(5)fm−3.
We calculate the up-, down-, strange-, charm-, and bottom-quark masses using the MILC highly improved staggered-quark ensembles with four flavors of dynamical quarks. We use ensembles at six lattice ...spacings ranging from a≈0.15 to 0.03 fm and with both physical and unphysical values of the two light and the strange sea-quark masses. We use a new method based on heavy-quark effective theory (HQET) to extract quark masses from heavy-light pseudoscalar meson masses. Combining our analysis with our separate determination of ratios of light-quark masses we present masses of the up, down, strange, charm, and bottom quarks. Our results for the MS¯-renormalized masses are mu(2 GeV)=2.130(41) MeV, md(2 GeV)=4.675(56) MeV, ms(2 GeV)=92.47(69) MeV, mc(3 GeV)=983.7(5.6) MeV, and mc(mc)=1273(10) MeV, with four active flavors; and mb(mb)=4195(14) MeV with five active flavors. We also obtain ratios of quark masses mc/ms=11.783(25), mb/ms=53.94(12), and mb/mc=4.578(8). The result for mc matches the precision of the most precise calculation to date, and the other masses and all quoted ratios are the most precise to date. Moreover, these results are the first with a perturbative accuracy of αs4. As byproducts of our method, we obtain the matrix elements of HQET operators with dimension 4 and 5: Λ¯MRS=555(31) MeV in the minimal renormalon-subtracted (MRS) scheme, μπ2=0.05(22) GeV2, and μG2(mb)=0.38(2) GeV2. The MRS scheme Phys. Rev. D 97, 034503 (2018) is the key new aspect of our method.
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