118580235
Higher-order ratios of baryon number cumulants
The relevance of higher order cumulants of net baryon number fluctuations for the analysis of freeze-out and critical conditions in heavy-ion collisions at LHC and RHIC is addressed. The sign structure of the higher order cumulants in the vicinity of the chiral crossover temperature might be a sensitive probe and may allow to elucidate their relation to the QCD phase transition. We calculate ratios of generalized quarknumber susceptibilities to high orders in three flavor QCD-like models and investigate their sign structure close to the chiral crossover line.
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.
17501397
Low-momentum hyperon-nucleon interactions
We present a first exploratory study for hyperon-nucleon interactions using renormalization group techniques. The effective two-body low-momentum potential ${V}_{\text{low}\phantom{\rule{0.3em}{0ex}}k}$ is obtained by integrating out the high-momentum components from realistic Nijmegen YN potentials. A T-matrix equivalence approach is employed, so that the low-energy phase shifts are reproduced by ${V}_{\text{low}\phantom{\rule{0.3em}{0ex}}k}$ up to a momentum scale $\ensuremath{\Lambda}~500$ MeV. Although the various bare Nijmegen models differ somewhat from each other, the corresponding ${V}_{\text{low}\phantom{\rule{0.3em}{0ex}}k}$ interactions show convergence in some channels, suggesting a possible model-independent YN interaction at low momenta.
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.
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.
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.
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.
16569966
Fermionic fields in the pseudoparticle approach
The pseudoparticle approach is a numerical method to compute path integrals without discretizing spacetime. The basic idea is to consider only those field configurations, which can be represented as a linear superposition of a small number of localized building blocks (pseudoparticles), and to replace the functional integration by an integration over the pseudoparticle degrees of freedom. In previous papers we have successfully applied the pseudoparticle approach to SU(2) Yang-Mills theory. In this work we discuss the inclusion of fermionic fields in the pseudoparticle approach. To test our method, we compute the phase diagram of the 1+1-dimensional Gross-Neveu model in the large-N limit as well as the chiral condensate in the crystal phase.
27851457
Light hadrons from Nf=2+1+1 dynamical twisted mass fermions
7 pages, 5 figures, talk presented at the XXVIII International Symposium on Lattice Field Theory, Lattice2010, June 14-19, 2010 Villasimius, Italy
17073204
The adjoint potential in the pseudoparticle approach: string breaking and Casimir scaling
We perform a detailed study of the adjoint static potential in the pseudoparticle approach, which is a model for SU(2) Yang-Mills theory. We find agreement with the Casimir scaling hypothesis and there is clear evidence for string breaking. At the same time the potential in the fundamental representation is linear for large separations. Our results are in qualitative agreement with results from lattice computations.
39889187
Kaon and D meson masses with N_f = 2+1+1 twisted mass lattice QCD
We discuss the computation of the kaon and D meson masses in the N_f = 2+1+1 twisted mass lattice QCD setup, where explicit heavy flavor and parity breaking occurs at finite lattice spacing. We present three methods suitable in this context and verify their consistency.