Ardit Krasniqi - Academia.edu (original) (raw)

Papers by Ardit Krasniqi

arXiv (Cornell University), Nov 28, 2022

We investigate several aspects of chiral symmetry in QCD at a temperature of T = 128 MeV. The stu... more We investigate several aspects of chiral symmetry in QCD at a temperature of T = 128 MeV. The study is based on a 24 × 96 3 lattice-QCD ensemble with O(a)improved Wilson quarks and physical up, down and strange quark masses. The pion quasiparticle turns out to be significantly lighter than the zero-temperature pion mass, even though the corresponding static correlation length is shorter. We perform a quantitative comparison of our findings to predictions of chiral perturbation theory. Among several order parameters for chiral symmetry restoration, we compute the difference of the vector-and axial-vector time-dependent correlators and find it to be reduced by a factor ∼ 2/3 as compared to its vacuum counterpart.

arXiv (Cornell University), Dec 11, 2022

The thermal photon emission rate is determined by the spatially transverse, in-medium spectral fu... more The thermal photon emission rate is determined by the spatially transverse, in-medium spectral function of the electromagnetic current. Accessing the spectral function using Euclidean data is, however, a challenging problem due to the ill-posed nature of inverting the Laplace transform. In this contribution, we present the first results on implementing the proposal of directly computing the analytic continuation of the retarded correlator at fixed, vanishing virtuality of the photon via the calculation of the appropriate Euclidean correlator at imaginary spatial momentum. We employ two dynamical O()-improved Wilson fermions at a temperature of 250 MeV.

Proceedings of The 39th International Symposium on Lattice Field Theory — PoS(LATTICE2022), Dec 23, 2022

We investigate the properties of the pion quasiparticle in the thermal hadronic phase of (2 + 1)-... more We investigate the properties of the pion quasiparticle in the thermal hadronic phase of (2 + 1)-flavor QCD on the lattice at physical quark masses at a temperature = 128 MeV. We find that the pion quasiparticle mass 0 = 113(3) MeV is significantly reduced relative to the zero-temperature pion mass 0 = 128(1) MeV, by contrast with the static screening mass = 144(3) MeV, which increases with temperature. On the other hand the pion quasiparticle decay constant does not change much compared to the corresponding zero-temperature decay constant. The difference of the vector-and axialvector spectral functions serves as an order parameter of chiral symmetry restoration. By analyzing this quantity we conclude that chiral symmetry restoration is already at an advanced stage in the spectral function.

Proceedings of The 39th International Symposium on Lattice Field Theory — PoS(LATTICE2022)

The photon emissivity of the quark-gluon plasma (QGP) is an important input to predict the photon... more The photon emissivity of the quark-gluon plasma (QGP) is an important input to predict the photon yield in heavy-ion collisions, particularly for transverse momenta in the range of 1 to 2 GeV. Photon production in the QGP can be probed non-perturbatively in lattice QCD via (Euclidean) timedependent correlators. Analyzing the spatially transverse channel, as well as the difference of the transverse and longitudinal channels as a consistency check, we determine the photon emissivity based on continuum-extrapolated correlators in two-flavour QCD. Estimates of the lepton-pair production rate can be derived by combining the two aforementioned channels.

Proceedings of The 39th International Symposium on Lattice Field Theory — PoS(LATTICE2022)

The thermal photon emission rate is determined by the spatially transverse, in-medium spectral fu... more The thermal photon emission rate is determined by the spatially transverse, in-medium spectral function of the electromagnetic current. Accessing the spectral function using Euclidean data is, however, a challenging problem due to the ill-posed nature of inverting the Laplace transform. In this contribution, we present the first results on implementing the proposal of directly computing the analytic continuation of the retarded correlator at fixed, vanishing virtuality of the photon via the calculation of the appropriate Euclidean correlator at imaginary spatial momentum. We employ two dynamical O()-improved Wilson fermions at a temperature of 250 MeV.

Proceedings of The 38th International Symposium on Lattice Field Theory — PoS(LATTICE2021)

We present results for the photon emission rate determined from the transverse channel vector cor... more We present results for the photon emission rate determined from the transverse channel vector correlator at fixed spatial momentum using two flavors of dynamical Wilson fermions at ∼250 MeV. We estimate the transverse channel spectral function using the continuum extrapolated correlator by applying various fit ansätze with a smooth matching to the NLO perturbative result. We confront our estimate based on this channel with the latest results of our collaboration based on the difference of the transverse and longitudinal channels.

Physical Review D

display=\"inline\">24×963</ msup> latti... more display=\"inline\">24×963</ msup> lattice-QCD ensemble with <math xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><mi mathvariant=\"normal\">O<mo stretchy=\"false\">(a<mo stretchy=\"false\">)-improved Wilson quarks and physical up, down and strange quark masses. The pion quasiparticle turns out to be significantly lighter than the zero-temperature pion mass, even though the corresponding static correlation length is shorter. We perform a quantitative comparison of our findings to predictions of chiral perturbation theory. Among several order parameters for chiral symmetry restoration, we compute the difference of the vector-and axialvector time-dependent correlators and find it to be reduced by a factor <math xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"> 2/3 as compared to ∼ its vacuum counterpart.

arXiv (Cornell University), Nov 28, 2022

We investigate several aspects of chiral symmetry in QCD at a temperature of T = 128 MeV. The stu... more We investigate several aspects of chiral symmetry in QCD at a temperature of T = 128 MeV. The study is based on a 24 × 96 3 lattice-QCD ensemble with O(a)improved Wilson quarks and physical up, down and strange quark masses. The pion quasiparticle turns out to be significantly lighter than the zero-temperature pion mass, even though the corresponding static correlation length is shorter. We perform a quantitative comparison of our findings to predictions of chiral perturbation theory. Among several order parameters for chiral symmetry restoration, we compute the difference of the vector-and axial-vector time-dependent correlators and find it to be reduced by a factor ∼ 2/3 as compared to its vacuum counterpart.

arXiv (Cornell University), Dec 11, 2022

The thermal photon emission rate is determined by the spatially transverse, in-medium spectral fu... more The thermal photon emission rate is determined by the spatially transverse, in-medium spectral function of the electromagnetic current. Accessing the spectral function using Euclidean data is, however, a challenging problem due to the ill-posed nature of inverting the Laplace transform. In this contribution, we present the first results on implementing the proposal of directly computing the analytic continuation of the retarded correlator at fixed, vanishing virtuality of the photon via the calculation of the appropriate Euclidean correlator at imaginary spatial momentum. We employ two dynamical O()-improved Wilson fermions at a temperature of 250 MeV.

Proceedings of The 39th International Symposium on Lattice Field Theory — PoS(LATTICE2022), Dec 23, 2022

We investigate the properties of the pion quasiparticle in the thermal hadronic phase of (2 + 1)-... more We investigate the properties of the pion quasiparticle in the thermal hadronic phase of (2 + 1)-flavor QCD on the lattice at physical quark masses at a temperature = 128 MeV. We find that the pion quasiparticle mass 0 = 113(3) MeV is significantly reduced relative to the zero-temperature pion mass 0 = 128(1) MeV, by contrast with the static screening mass = 144(3) MeV, which increases with temperature. On the other hand the pion quasiparticle decay constant does not change much compared to the corresponding zero-temperature decay constant. The difference of the vector-and axialvector spectral functions serves as an order parameter of chiral symmetry restoration. By analyzing this quantity we conclude that chiral symmetry restoration is already at an advanced stage in the spectral function.

Proceedings of The 39th International Symposium on Lattice Field Theory — PoS(LATTICE2022)

The photon emissivity of the quark-gluon plasma (QGP) is an important input to predict the photon... more The photon emissivity of the quark-gluon plasma (QGP) is an important input to predict the photon yield in heavy-ion collisions, particularly for transverse momenta in the range of 1 to 2 GeV. Photon production in the QGP can be probed non-perturbatively in lattice QCD via (Euclidean) timedependent correlators. Analyzing the spatially transverse channel, as well as the difference of the transverse and longitudinal channels as a consistency check, we determine the photon emissivity based on continuum-extrapolated correlators in two-flavour QCD. Estimates of the lepton-pair production rate can be derived by combining the two aforementioned channels.

Proceedings of The 39th International Symposium on Lattice Field Theory — PoS(LATTICE2022)

The thermal photon emission rate is determined by the spatially transverse, in-medium spectral fu... more The thermal photon emission rate is determined by the spatially transverse, in-medium spectral function of the electromagnetic current. Accessing the spectral function using Euclidean data is, however, a challenging problem due to the ill-posed nature of inverting the Laplace transform. In this contribution, we present the first results on implementing the proposal of directly computing the analytic continuation of the retarded correlator at fixed, vanishing virtuality of the photon via the calculation of the appropriate Euclidean correlator at imaginary spatial momentum. We employ two dynamical O()-improved Wilson fermions at a temperature of 250 MeV.

Proceedings of The 38th International Symposium on Lattice Field Theory — PoS(LATTICE2021)

We present results for the photon emission rate determined from the transverse channel vector cor... more We present results for the photon emission rate determined from the transverse channel vector correlator at fixed spatial momentum using two flavors of dynamical Wilson fermions at ∼250 MeV. We estimate the transverse channel spectral function using the continuum extrapolated correlator by applying various fit ansätze with a smooth matching to the NLO perturbative result. We confront our estimate based on this channel with the latest results of our collaboration based on the difference of the transverse and longitudinal channels.

Physical Review D

display=\"inline\">24×963</ msup> latti... more display=\"inline\">24×963</ msup> lattice-QCD ensemble with <math xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><mi mathvariant=\"normal\">O<mo stretchy=\"false\">(a<mo stretchy=\"false\">)-improved Wilson quarks and physical up, down and strange quark masses. The pion quasiparticle turns out to be significantly lighter than the zero-temperature pion mass, even though the corresponding static correlation length is shorter. We perform a quantitative comparison of our findings to predictions of chiral perturbation theory. Among several order parameters for chiral symmetry restoration, we compute the difference of the vector-and axialvector time-dependent correlators and find it to be reduced by a factor <math xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"> 2/3 as compared to ∼ its vacuum counterpart.