Search results for "Spectral function"

Updated determination of chiral couplings and vacuum condensates from hadronic tau decay data

2016

We analyze the lowest spectral moments of the left-right two-point correlation function, using all known short-distance constraints and the recently updated ALEPH V-A spectral function from tau decays. This information is used to determine the low-energy couplings L10 and C87 of chiral perturbation theory and the lowest-dimensional contributions to the Operator Product Expansion of the left-right correlator. A detailed statistical analysis is implemented to assess the theoretical uncertainties, including violations of quark-hadron duality.

Mesonic and binding contributions to the nuclear Drell-Yan process

1997

We have evaluated the Drell-Yan cross section in nuclei paying special attention to the meson cloud contribution from pion and rho-meson, for which an accurate calculation using the meson nuclear spectral functions is used. Similarly, the nucleonic contribution is evaluated in terms of a relativistic nucleon spectral function. Fair agreement with experiment is found for different nuclei and the results show a sizeable contribution from the renormalized meson cloud. In order to reproduce the experiment a novel element is introduced, consisting of a gradual energy loss of the incoming proton in its pass through the nucleus which produces a strong A dependence at x_1 large.

Duality violation in QCD Sum Rules with the LR correlator

2010

5 páginas, 4 figuras.-- Dedicated to the memory of our colleague and friend Joaquim (Ximo) Prades.-- Talk given at the 15th International QCD Conference (Montpellier, 28th June - 3rd July 2010) and the Internation Light Cone 2010 Conference (Valencia, 14-18th June 2010).-- arXiv:1010.1219v1.

Nucleon structure and nucleon-nucleon interaction

1978

The strong coupling from ALEPH tau decays

2017

The strong coupling from ALEPH tau decays. We use the publically available non-strange spectral function from ALEPH tau decays to critically analyze the different determinations of αs(mτ2) that can be found in the literature and the numerical impact of their possible weaknesses. We also introduce some novel approaches. We find that perturbative uncertainties dominate. Our results with different approaches are very stable. Our final value is αs(mτ2)=0.328±0.013.

Probing spectral properties of the QGP with real-time lattice simulations

2018

We present a new method to obtain spectral properties of a non-Abelian gauge theory in the region where occupation numbers are high. The method to measure the (single-particle) spectral function is based on linear response theory and classical-statistical lattice simulations. Although we apply it to a system far from equilibrium in a self-similar regime, the extracted spectral function can be understood within the hard thermal loop (HTL) formalism and can thus be connected to thermal equilibrium at high temperatures. This allows us to obtain quantities like the lifetime of quasiparticles that are beyond the leading order and difficult to compute within HTL. The approach has the potential to…

Diagrammatic expansion for positive spectral functions beyond GW : Application to vertex corrections in the electron gas

2014

We present a diagrammatic approach to construct self-energy approximations within many-body perturbation theory with positive spectral properties. The method cures the problem of negative spectral functions which arises from a straightforward inclusion of vertex diagrams beyond the GW approximation. Our approach consists of a two-steps procedure: we first express the approximate many-body self-energy as a product of half-diagrams and then identify the minimal number of half-diagrams to add in order to form a perfect square. The resulting self-energy is an unconventional sum of self-energy diagrams in which the internal lines of half a diagram are time-ordered Green's functions whereas those…

Prospects for dilepton rates from lattice QCD

2015

We discuss the prospects of computing thermal dilepton rates from first principles lattice QCD. The focus lies in the determination of the meson vector-vector current spectral function to estimate the electrical conductivity, heavy quark diffusion and quarkonium dissociation. We review and compare recent results from continuum-extrapolated, quenched calculations, as well as dynamical two-flavor setups.

Strange quark mass from the invariant mass distribution of Cabibbo-suppressed tau decays

2001

8 páginas, 4 figuras, 4 tablas.-- arXiv:hep-ph/0105253v1

Light quark masses from scalar sum rules

2001

7 páginas, 2 figuras, 1 tabla.-- arXiv:hep-ph/0110194v2