Publications (451)992.88 Total impact
 [Show abstract] [Hide abstract]
ABSTRACT: We study the correlators of Polyakov loops, and the corresponding gauge invariant free energy of a static quarkantiquark pair in 2+1 flavor QCD at finite temperature. Our simulations were carried out on $N_t$ = 6, 8, 10, 12, 16 lattices using Symanzik improved gauge action and a stout improved staggered action with physical quark masses. The free energies calculated from the Polyakov loop correlators are extrapolated to the continuum limit. For the free energies we use a two step renormalization procedure that only uses data at finite temperature. We also measure correlators with definite Euclidean time reversal and charge conjugation symmetry to extract two different screening masses, one in the magnetic, and one in the electric sector, to distinguish two different correlation lengths in the full Polyakov loop correlator.01/2015;  [Show abstract] [Hide abstract]
ABSTRACT: We perform a detailed, fullycorrelated study of the chiral behavior of the pion mass and decay constant, based on 2+1 flavor lattice QCD simulations. These calculations are implemented using treelevel, O(a)improved Wilson fermions, at four values of the lattice spacing down to 0.054 fm and all the way down to below the physical value of the pion mass. They allow a sharp comparison with the predictions of SU(2) chiral perturbation theory (\chi PT) and a determination of some of its low energy constants. In particular, we systematically explore the range of applicability of NLO SU(2) \chi PT in two different expansions: the first in quark mass (xexpansion), and the second in pion mass (\xiexpansion). We find that these expansions begin showing signs of failure around M_\pi=300 MeV for the typical percentlevel precision of our N_f=2+1 lattice results. We further determine the LO low energy constants (LECs), F=88.0 \pm 1.3\pm 0.3 and B^\msbar(2 GeV)=2.58 \pm 0.07 \pm 0.02 GeV, and the related quark condensate, \Sigma^\msbar(2 GeV)=(271\pm 4\pm 1 MeV)^3, as well as the NLO ones, l_3=2.5 \pm 0.5 \pm 0.4 and l_4=3.8 \pm 0.4 \pm 0.2, with fully controlled uncertainties. We also explore the NNLO expansions and the values of NNLO LECs. In addition, we show that the lattice results favor the presence of chiral logarithms. We further demonstrate how the absence of lattice results with pion masses below 200 MeV can lead to misleading results and conclusions. Our calculations allow a fully controlled, ab initio determination of the pion decay constant with a total 1% error, which is in excellent agreement with experiment.Physical Review D. 12/2014;  [Show abstract] [Hide abstract]
ABSTRACT: $\phi$ and K$^$ mesons from Ni+Ni collisions at the beam energy of 1.91A GeV have been measured by the FOPI spectrometer, with a trigger selecting central and semicentral events amounting to 51% of the total cross section. The phase space distributions, and the total yield of K$^$, as well as the kinetic energy distribution and the total yield of $\phi$ mesons are presented. The $\phi$\K$^$ ratio is found to be $0.44 \pm 0.07(\text{stat}) ^{+0.18}_{0.12} (\text{syst})$, meaning that about 22% of K$^$ mesons originate from the decays of $\phi$ mesons, occurring mostly in vacuum. The inverse slopes of direct kaons are up to about 15 MeV larger than the ones extracted within the onesource model, signalling that a considerable share of gap between the slopes of K$^+$ and K$^$ could be explained by the contribution of $\phi$ mesons to negative kaons.12/2014;  [Show abstract] [Hide abstract]
ABSTRACT: The cutoff effects of the lattice gradient flow  often called Wilson flow  are calculated on a periodic 4torus at leading order in the gauge coupling. A large class of discretizations is considered which includes all frequently used cases in practice. It is shown how the results lead to a smoother continuum extrapolation for the betafunction of SU(3) gauge theory with N_f = 4 flavors of fermions.10/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We report on a continuum extrapolated result (arXiv:1309.5258) for the equation of state (EoS) of QCD with $N_f=2+1$ dynamical quark flavors and discuss preliminary results obtained with an additional dynamical charm quark ($N_f=2+1+1$). For all our final results, the systematics are controlled, quark masses are set to their physical values, and the continuum limit is taken using at least three lattice spacings corresponding to temporal extents up to $N_t=16$.10/2014;  [Show abstract] [Hide abstract]
ABSTRACT: Finite temperature charmonium spectral functions in the pseudoscalar(PS) and vector(V) channels are studied in lattice QCD with 2+1 flavours of dynamical Wilson quarks, on fine isotropic lattices (with a lattice spacing of 0.057fm), with a nonphysical pion mass of 545MeV. The highest temperature studied is approximately 1.4Tc. Up to this temperature no significant variation of the spectral function is seen in the PS channel. The V channel shows some temperature dependence, which seems to be consistent with a temperature dependent low frequency peak related to heavy quark transport, plus a temperature independent term at omega > 0. These results are in accord with previous calculations using the quenched approximation.10/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We present our latest results for fluctuations of electric charge and baryon number, simulated on the lattice in a system of 2+1 dynamical quark flavors at the physical quark masses and continuum extrapolated. In order to extract the chemical freezeout temperature and chemical potential, we compare our results to the moments of multiplicity distribution of the corresponding conserved charges, measured in heavy ion collision experiments by the STAR collaboration. Consistency between the freezeout parameters obtained through different conserved charges is discussed.Journal of Physics Conference Series 09/2014; 535(1):012030.  [Show abstract] [Hide abstract]
ABSTRACT: In this talk, the response of the thermal QCD medium to external (electro)magnetic fields is studied using continuum extrapolated lattice results at physical quark masses. The magnetic susceptibility of QCD is calculated, revealing a strong paramagnetic response at high temperatures. This paramagnetism is shown to result in an anisotropic squeezing of the quark–gluon plasma in noncentral heavyion collisions, implying a sizeable contribution to the elliptic flow. Another aspect is the magnetic response of topologically nontrivial domains to the magnetic field. We quantify this effect on the lattice and compare the results to a simple model estimate.Nuclear Physics A 09/2014; · 2.50 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The latest results on fluctuations of electric charge and baryon number, simulated on the lattice by the Wuppertal–Budapest collaboration, are compared to the moments of multiplicity distribution of the corresponding conserved charges, measured in heavy ion collision experiments by the STAR collaboration. The purpose of this study is to extract the chemical freezeout parameters (temperature and chemical potential) as a function of the collision energy, from first principles. Consistency between the freezeout parameters obtained through the two different conserved charges used in the analysis is discussed.Nuclear Physics A 08/2014; · 2.50 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The existence and stability of atoms relies on the fact that neutrons are more massive than protons. The mass difference is only 0.14% of the average. This tiny mass splitting has significant astrophysical and cosmological implications. A slightly smaller or larger value would have led to a dramatically different universe. Here we show, how this difference results from the competition between electromagnetic and mass isospin breaking effects. We compute the neutronproton mass splitting and show that it is greater than zero by five standard deviations. Furthermore, splittings in the $\Sigma$, $\Xi$, $D$ and $\Xi_{cc}$ isospin multiplets are determined providing also predictions. We perform lattice QuantumChromodynamics plus QuantumElectrodynamics computations with four, nondegenerate Wilson fermion flavors. Four lattice spacings and pion masses down to 195 MeV are used.06/2014;  [Show abstract] [Hide abstract]
ABSTRACT: The YangMills gradient flow and the observable E(t), defined by the square of the field strength tensor at t>0, are calculated at finite lattice spacing and treelevel in the gauge coupling. Improvement of the flow, the gauge action and the observable are all considered. The results are relevant for two purposes. First, the discretization of the flow, gauge action and observable can be chosen in such a way that $O(a^2)$, $O(a^4)$ or even $O(a^6)$ improvement is achieved. Second, simulation results using arbitrary discretizations can be treelevel improved by the perturbatively calculated correction factor normalized to one in the continuum limit.Journal of High Energy Physics 06/2014; 2014(9). · 6.22 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We highlight the progress, current status, and open challenges of QCDdriven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to stronglycoupled, complex systems in particle and condensedmatter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.04/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We study local CPviolation on the lattice by measuring the local correlation between the topological charge density and the electric dipole moment of quarks, induced by a constant external magnetic field. This correlator is found to increase linearly with the external field, with the coefficient of proportionality depending only weakly on temperature. Results are obtained on lattices with various spacings, and are extrapolated to the continuum limit after the renormalization of the observables is carried out. This renormalization utilizes the gradient flow for the quark and gluon fields. Our findings suggest that the strength of local CPviolation in QCD with physical quark masses is about an order of magnitude smaller than a model prediction based on nearly massless quarks in domains of constant gluon backgrounds with topological charge. We also show numerical evidence that the observed local CPviolation correlates with spatially extended electric dipole structures in the QCD vacuum.Journal of High Energy Physics 04/2014; 2014(4). · 6.22 Impact Factor 
Conference Paper: Can the Higgs Impostor Hide Near the Conformal Window?
Proceedings of KMIGCOE Workshop; 03/2014 
Article: Freezeout parameters from electric charge and baryon number fluctuations: is there consistency?
[Show abstract] [Hide abstract]
ABSTRACT: Recent results for moments of multiplicity distributions of netprotons and netelectric charge from the STAR collaboration are compared to lattice QCD results for higher order fluctuations of baryon number and electric charge by the WuppertalBudapest collaboration, with the purpose of extracting the freezeout temperature and chemical potential. All lattice simulations are performed at the physical mass for light and strange quarks; all results are continuum extrapolated. We show that it is possible to extract an upper value for the freezeout temperature, as well as precise baryochemical potential values corresponding to the four highest collision energies of the experimental beam energy scan. Consistency between the freezeout parameters obtained from baryon number and electric charge fluctuations is found. The freezeout chemical potentials are now in agreement with the statistical hadronization model.Physical review letters. 03/2014; 113(5).  [Show abstract] [Hide abstract]
ABSTRACT: Azimuthal emission patterns of $K^\pm$ mesons have been measured in Ni + Ni collisions with the FOPI spectrometer at a beam kinetic energy of 1.91 A GeV. The transverse momentum $p_{T}$ integrated directed and elliptic flow of $K^{+}$ and $K^{}$ mesons as well as the centrality dependence of $p_{T}$  differential directed flow of $K^{+}$ mesons are compared to the predictions of HSD and IQMD transport models. The data exhibits different propagation patterns of $K^{+}$ and $K^{}$ mesons in the compressed and heated nuclear medium and favor the existence of a kaonnucleon inmedium potential, repulsive for $K^{+}$ mesons and attractive for $K^{}$ mesons.Physical Review C 03/2014; 90(2). · 3.88 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The eigenvalues of the Dirac operator at finite volume encode whether or not chiral symmetry is spontaneously broken in a massless theory. We apply this framework in a particular BSM context, namely SU(3) gauge theory with N_f=2 massless flavors in the 2index symmetric (sextet) representation. Our first results are at a single lattice spacing. We find that both the density of nearzero eigenvalues and the renormalization group invariant mode number indicate spontaneous symmetry breaking. Quantitatively, there is a discrepancy between the determination of the fermion condensate in the chiral limit via the eigenvalue spectrum and the determinations from direct measurements of the chiral condensate and the GMOR relation. We comment on possible explanations of this discrepancy and further refinements of this study.02/2014;  [Show abstract] [Hide abstract]
ABSTRACT: Finite temperature charmonium spectral functions in the pseudoscalar and vector channels are studied in lattice QCD with 2+1 flavours of dynamical Wilson quarks, on fine isotropic lattices (with a lattice spacing of 0.057 fm), with a nonphysical pion mass of $m_{\pi} \approx$ 545 MeV. The highest temperature studied is approximately $1.4 T_c$. Up to this temperature no significant variation of the spectral function is seen in the pseudoscalar channel. The vector channel shows some temperature dependence, which seems to be consistent with a temperature dependent low frequency peak related to heavy quark transport, plus a temperature independent term at \omega>0. These results are in accord with previous calculations using the quenched approximation.01/2014;  [Show abstract] [Hide abstract]
ABSTRACT: NA61/SHINE (SPS Heavy Ion and Neutrino Experiment) is a multipurpose experimental facility to study hadron production in hadronproton, hadronnucleus and nucleusnucleus collisions at the CERN Super Proton Synchrotron. It recorded the first physics data with hadron beams in 2009 and with ion beams (secondary 7Be beams) in 2011. NA61/SHINE has greatly profited from the long development of the CERN proton and ion sources and the accelerator chain as well as the H2 beamline of the CERN North Area. The latter has recently been modified to also serve as a fragment separator as needed to produce the Be beams for NA61/SHINE. Numerous components of the NA61/SHINE setup were inherited from its predecessors, in particular, the last one, the NA49 experiment. Important new detectors and upgrades of the legacy equipment were introduced by the NA61/SHINE Collaboration. This paper describes the state of the NA61/SHINE facility  the beams and the detector system  before the CERN Long Shutdown I, which started in March 2013.01/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We study the chiral magnetic effect on the lattice by measuring the local correlation between the topological charge density and the electric dipole moment of quarks, induced by the magnetic field. This correlator is found to increase linearly with the external field, with the coefficient of proportionality depending only weakly on temperature. Results are obtained on lattices with various spacings, and are extrapolated to the continuum limit after the renormalization of the observables is carried out. This renormalization utilizes the gradient flow for the quark and gluon fields. Our findings suggest that the strength of the chiral magnetic effect is about an order of magnitude smaller than the model prediction based on massless quarks, the lowestLandaulevel approximation and instantonlike gluon backgrounds.01/2014;
Publication Stats
9k  Citations  
992.88  Total Impact Points  
Top Journals
Institutions

2003–2014

Bergische Universität Wuppertal
 Physical and Theoretical Chemistry
Wuppertal, North RhineWestphalia, Germany


1997–2013

Hungarian Academy of Sciences
 • MTA Wigner Research Centre for Physics
 • Institute for Particle and Nuclear Physics
Budapeŝto, Budapest, Hungary


2012

Magyar Tudományos Akadémia Wigner Fizikai Kutatóközpont
Budapeŝto, Budapest, Hungary


1989–2011

Eötvös Loránd University
 • Department of Theoretical Physics
 • Institute of Physics
Budapest, Budapest fovaros, Hungary


2010

Massachusetts Institute of Technology
 Center for Theoretical Physics
Cambridge, MA, United States 
University of Oslo
 Department of Physics
Oslo, Oslo, Norway


1993–2008

Deutsches ElektronenSynchrotron
Hamburg, Hamburg, Germany


2005

University of Seoul
Sŏul, Seoul, South Korea


2004–2005

University Hospital Frankfurt
Frankfurt, Hesse, Germany 
Ruder Boskovic Institute
Zagrabia, Grad Zagreb, Croatia


1979–2001

Joint Institute for Nuclear Research
Dubno, Moskovskaya, Russia


1998

University of Münster
 Institute of Theoretical Physics
Muenster, North RhineWestphalia, Germany


1991–1995

CERN
Genève, Geneva, Switzerland


1989–1995

Université Blaise Pascal  ClermontFerrand II
 Laboratoire de Physique Corpusculaire
ClermontFerrand, Auvergne, France


1990

University of Freiburg
Freiburg, BadenWürttemberg, Germany
