Heavy-light quark pseudoscalar and vector mesons at finite temperature

The temperature dependence of the mass, leptonic decay constant, and width of heavy-light quark peseudoscalar and vector mesons is obtained in the framework of thermal Hilbert moment QCD sum rules. The leptonic decay constants of both pseudoscalar and vector mesons decrease with increasing $T$, and vanish at a critical temperature $T_c$, while the mesons develop a width which increases dramatically and diverges at $T_c$, where $T_c$ is the temperature for chiral-symmetry restoration. These results indicate the disappearance of hadrons from the spectral function, which then becomes a smooth function of the energy. This is interpreted as a signal for deconfinement at $T=T_c$. In contrast, the masses show little dependence on the temperature, except very close to $T_c$, where the pseudoscalar meson mass increases slightly by 10-20 %, and the vector meson mass decreases by some 20-30

Strange quark mass from Finite Energy QCD sum rules to five loops

The strange quark mass is determined from a new QCD Finite Energy Sum Rule (FESR) optimized to reduce considerably the systematic uncertainties arising from the hadronic resonance sector. As a result, the main uncertainty in this determination is due to the value of $\Lambda_{QCD}$. The correlator of axial-vector divergences is used in perturbative QCD to five-loop order, including quark and gluon condensate contributions, in the framework of both Fixed Order (FOPT), and Contour Improved Perturbation Theory (CIPT). The latter exhibits very good convergence, leading to a remarkably stable result in the very wide range $s_0 = 1.0 - 4.0 {GeV}^2$, where $s_0$ is the radius of the integration contour in the complex energy (squared) plane. The value of the strange quark mass in this framework at a scale of 2 GeV is $m_s(2 {GeV}) = 95 \pm 5 (111 \pm 6) {MeV}$ for $\Lambda_{QCD} = 420 (330) {MeV}$, respectively.Comment: Additional comments added at the end of the Conclusions, and one extra reference is given. A note added in proof uses the most recent determination of Lambda_QCD from ALEPH to narrow down the predictio

Strange quark condensate from QCD sum rules to five loops

It is argued that it is valid to use QCD sum rules to determine the scalar and pseudoscalar two-point functions at zero momentum, which in turn determine the ratio of the strange to non-strange quark condensates $R_{su} = \frac{}{}$ with ($q=u,d$). This is done in the framework of a new set of QCD Finite Energy Sum Rules (FESR) that involve as integration kernel a second degree polynomial, tuned to reduce considerably the systematic uncertainties in the hadronic spectral functions. As a result, the parameters limiting the precision of this determination are $\Lambda_{QCD}$, and to a major extent the strange quark mass. From the positivity of $R_{su}$ there follows an upper bound on the latter: $\bar{m_{s}} (2 {GeV}) \leq 121 (105) {MeV}$, for $\Lambda_{QCD} = 330 (420) {MeV} .$Comment: Minor changes to Sections 2 and