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.
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.
11518347
Static-static-light-light tetraquarks in lattice QCD
I report on a lattice computation of the energy of a system of two light quarks and two static antiquarks as a function of the separation of the static antiquarks. In terms of hadrons such a system corresponds to a pair of B mesons and its energy to the hadronic potential. I present selected results for different isospin, spin and parity combinations of the individual B mesons mainly focusing on those channels relevant to determine, whether two B mesons may form a bound tetraquark state.
29909987
Fermions in the pseudoparticle approach
The pseudoparticle approach is a numerical technique to compute path integrals without discretizing spacetime. The basic idea is to integrate over those field configurations, which can be represented by a sum of a fixed number of localized building blocks (pseudoparticles). In a couple of previous papers we have successfully applied the pseudoparticle approach to pure SU(2) Yang-Mills theory. In this work I discuss how to incorporate fermionic fields in the pseudoparticle approach. To test the method, I compute the phase diagram of the 1 + 1-dimensional Gross-Neveu model in the large-N limit.
23409560
The static-light baryon spectrum from twisted mass lattice QCD
We compute the static-light baryon spectrum by means of Wilson twisted mass lattice QCD using Nf = 2 flavors of sea quarks. As light u/d valence quarks we consider quarks, which have the same mass as the sea quarks with corresponding pion masses in the range 340 MeV ≲ ∼mPS ≲ 525 MeV,aswellaspartially quenched s quarks, which have a mass around the physical value. We consider all possible combinations of two light valence quarks, i.e. Λ, Σ, Ξ and Ω baryons corresponding to isospin I ∈ {0, 1/2, 1} and strangeness S ∈{0, − 1, − 2} as well as angular momentum of the light degrees of freedom j ∈{0, 1} and parity P ∈{+ , −}. We extrapolate in the light u/d and in the heavy b quark mass to the physical point and compare with available experimental results. Besides experimentally known positive parity states we are also able to predict a number of negative parity states, which have neither been measured in experiments nor previously been computed by lattice methods.
7348824
The continuum limit of the static-light meson spectrum
We investigate the continuum limit of the low lying static-light meson spectrum using Wilson twisted mass lattice QCD with Nf = 2 dynamical quark flavours. We consider three values of the lattice spacing a ≈ 0.051 fm, 0.064 fm, 0.080 fm and various values of the pion mass in the range 280 MeV ≲ mPS 640 MeV. We present results in the continuum limit for light cloud angular momentum j = 1/2, 3/2, 5/2 and for parity $ \mathcal{P} = +, - $. We extrapolate our results to physical quark masses, make predictions regarding the spectrum of B and Bs mesons and compare with available experimental results.
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.
119266212
QCD critical region and higher moments for three flavor models
One of the distinctive features of the QCD phase diagram is the possible emergence of a critical endpoint. The critical region around the critical point and the path dependency of the critical exponents are investigated within effective chiral (2 + 1)-flavor models with and without Polyakov loops. Results obtained in no-sea mean-field approximations where a divergent vacuum part in the fermion-loop contribution is neglected are compared to the renormalized ones. Furthermore, the modifications caused by the backreaction of the matter fluctuations on the pure Yang-Mills system are discussed. Higher-order, non-Gaussian moments of event-by-event distributions of various particle multiplicities are enhanced near the critical point and could serve as a probe to determine its location in the phase diagram. By means of a novel derivative technique higher-order generalized quark-number susceptibilities are calculated and their sign structure in the phase diagram is analyzed.
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.
18193194
QCD thermodynamics with effective models
In this talk we extend the Polyakov-quark-meson model to N_f=2+1 quark flavors and study its bulk thermodynamics at finite temperatures in mean-field approximation. Three different Polyakov-loop potentials are considered. Our findings are confronted to recent QCD lattice simulations of the RBC-Bielefeld and HotQCD collaborations. Furthermore, the finite chemical potential expansion of the quark-number susceptibility in a Taylor series around vanishing chemical potential is analyzed. By means of a novel algorithmic differentiation technique, we have calculated Taylor coefficients up to 24th order in the model for the first time. This allows the systematic study of convergence properties of the Taylor series.
62901349
Charge Fluctuations as Thermometer for Heavy-Ion Collisions
We present a determination of freeze-out conditions in heavy-ion collisions based on ratios of cumulants of net electric charge fluctuations obtained from lattice QCD. These ratios can reliably be calculated 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. We first determine the strangeness and electric charge chemical potentials that characterize the conditions in heavy ion collisions at RHIC and LHC. 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. We apply our method to preliminary data of the STAR and PHENIX collaborations.