118742513
QCD Thermodynamics: Confronting the Polyakov-Quark-Meson Model with Lattice QCD
NJL-type effective models represent a low-energy realization of QCD and incorporate pertinent aspects such as chiral symmetry and its spontaneous breaking, the center symmetry in the heavy-quark limit as well as the axial anomaly. One such model, the Polyakov-quark-meson model for three light quark flavors, is introduced in order to study the phase structure of strongly-interacting matter. With recent high-statistics lattice QCD simulations of the finite-temperature equation of state, a detailed comparison with model results becomes accessible. Such comparisons allow to estimate volume and truncation effects of quantities, obtained on the lattice and provide possible lattice extrapolation procedures to finite chemical potential which are important to locate a critical endpoint in the QCD phase diagram.
119299702
Deconfinement of strangeness and freeze-out from charge fluctuations
We use Lattice QCD calculations of fluctuations and correlations of various conserved charges to show that the deconfinement of strangeness takes place in the chiral crossover region of QCD; however, inside the quark-gluon plasma strange quarks remain strongly interacting at least up to temperatures twice the QCD crossover temperature. Further, we discuss how the freeze-out parameters of heavy-ion collisions can be determined in a model-independent way through direct comparisons between experimentally measured higher order cumulants of conserved charges and corresponding Lattice QCD calculations. Utilizing the preliminary data from the STAR and PHENIX experiments we illustrate this method. Although, the Lattice QCD based determinations of the freeze-out parameters utilizing data sets of different experiments and different observables are currently not consistent with each other, it is tantalizing to see that all the observed freeze-out parameters lie very close to the chiral/deconfinement crossover region of QCD.
3253782
On the efficient computation of high-order derivatives for implicitly defined functions
Abstract Scientific studies often require the precise calculation of derivatives. In many cases an analytical calculation is not feasible and one resorts to evaluating derivatives numerically. These are error-prone, especially for higher-order derivatives. A technique based on algorithmic differentiation is presented which allows for a precise calculation of higher-order derivatives. The method can be widely applied even for the case of only numerically solvable, implicit dependencies which totally hamper a semi-analytical calculation of the derivatives. As a demonstration the method is applied to a quantum field theoretical physical model. The results are compared with standard numerical derivative methods.
16484524
On the QCD phase structure from effective models
Abstract Some recent theoretical developments of the QCD phase diagram are summarized. Chiral symmetry restoration and the confinement/deconfinement transition at nonzero temperature and quark densities are analyzed in the framework of an effective linear sigma model with three light quark flavors. The sensitivity of the chiral transition as well as the existence of a critical end point in the phase diagram on the value of the sigma mass is explored. The influence of the axial anomaly on the chiral critical surface is addressed. Finally, the modifications by the inclusion of the Polyakov loop on the phase structure are investigated.
118463111
The Three-flavor chiral phase structure in hot and dense QCD matter
Chiral symmetry restoration at nonzero temperature and quark densities are investigated in the framework of a linear sigma model with N{sub f}=3 light quark flavors. After the derivation of the grand potential in mean-field approximation, the nonstrange and strange condensates, the in-medium masses of the scalar and pseudoscalar nonets are analyzed in hot and dense medium. The influence of the axial anomaly on the nonet masses and the isoscalar mixings on the pseudoscalar {eta}-{eta}{sup '} and scalar {sigma}(600)-f{sub 0}(1370) complex are examined. The sensitivity of the chiral phase transition as well as the existence and location of a critical end point in the phase diagram on the value of the sigma mass are explored. The chiral critical surface with and without the influence of the axial U(1){sub A} anomaly is elaborated as a function of the pion and kaon masses for several values of the sigma mass.
115815562
On the convergence of multi-channel effective interactions
A detailed analysis of convergence properties of the Andreozzi-Lee-Suzuki iteration method, which is used for the calculation of low-momentum effective potentials Vlowk is presented. After summarizing different modifications of the iteration method for one-flavor channel we introduce a simple model in order to study the generalization of the iteration method to multi-flavor channels. The failure of a straightforward generalization is discussed. The introduction of a channel-dependent cutoff cures the conceptual and technical problems. This novel method has already been applied successfully for realistic hyperon-nucleon interactions.
1888088
The pseudoparticle approach for solving path integrals in gauge theories
We present a numerical technique for calculating path integrals in non-compact U(1) and SU(2) gauge theories. The gauge fields are represented by a superposition of pseudoparticles of various types with their amplitudes and color orientations as degrees of freedom. Applied to Maxwell theory this technique results in a potential which is in excellent agreement with the Coulomb potential. For SU(2) Yang-Mills theory the same technique yields clear evidence of confinement. Varying the coupling constant exhibits the same scaling behavior for the string tension, the topological susceptibility and the critical temperature while their dimensionless ratios are similar to those obtained in lattice calculations.
61399113
Hough Transform Based Pattern Recognition for the $\overline{P}$ANDA Forward Tracking System
6716581
Static-light meson masses from twisted mass lattice QCD
We compute the static-light meson spectrum using two-flavor Wilson twisted mass lattice QCD. We have considered five different values for the light quark mass corresponding to 300 MeV < m_PS < 600 MeV. We have extrapolated our results, to make predictions regarding the spectrum of B and B_s mesons.
3216251
Classes of confining gauge field configurations
We present a numerical method to compute path integrals in effective SU(2) Yang-Mills theories. The basic idea is to approximate the Yang-Mills path integral by summing over all gauge field configurations, which can be represented as a linear superposition of a small number of localized building blocks. With a suitable choice of building blocks many essential features of SU(2) Yang-Mills theory can be reproduced, particularly confinement. The analysis of our results leads to the conclusion that topological charge as well as extended structures are essential elements of confining gauge field configurations.
38785788
The spectrum of static-light baryons in twisted mass lattice QCD
We compute the static-light baryon spectrum with N_f = 2 flavors of sea quarks using Wilson twisted mass lattice QCD. As light valence quarks we consider quarks, which have the same mass as the sea quarks with corresponding pion masses in the range 340 MeV < m_PS < 525 MeV, as well as partially quenched quarks, which have the mass of the physical s quark. We extract masses of states with isospin I = 0, 1/2, 1, with strangeness S = 0, -1, -2, with angular momentum of the light degrees of freedom j = 0, 1 and with parity P = +, -. We present a preliminary extrapolation in the light u/d and an interpolation in the heavy b quark mass to the physical point and compare with available experimental results.