10220872
Is a soft nuclear equation of state extracted from heavy-ion data incompatible with pulsar data?
We discuss the recent constraints on the nuclear equation of state (EoS) from pulsar mass measurements and from subthreshold production of kaons in heavy-ion collisions. While the recent pulsar data point towards a hard EoS, the analysis of the heavy-ion data allows only for soft equations of state. We resolve the apparent contradiction by considering the different density regimes probed. We argue that future measurements of global properties of low-mass pulsars can serve as an excellent cross-check to the heavy-ion data.
25947222
Evidence for a Soft Nuclear Equation-of-State from Kaon Production in Heavy-Ion Collisions.
The production of pions and kaons has been measured in 197Au+197Au collisions at beam energies from 0.6 to 1.5A GeV with the kaon spectrometer at SIS/GSI. The K+ meson multiplicity per nucleon is enhanced in Au+Au collisions by factors up to 6 relative to C+C reactions, whereas the corresponding pion ratio is reduced. The ratio of the K+ meson excitation functions for Au+Au and C+C collisions increases with decreasing beam energy. This behavior is expected for a soft nuclear equation-of-state.
119236403
Neutron star versus heavy-ion data: is the nuclear equation of state hard or soft?
Recent astrophysical observations of neutron stars and heavy-ion data are confronted with our present understanding of the equation of state of dense hadronic matter. Emphasis is put on the possible role of the presence of hyperons in the interior of compact stars. We argue that data from low-mass pulsars provide an important cross-check between high-density astrophysics and heavy-ion physics.
119373633
Review of the results of the KaoS Collaboration
The production of K+ and of K− mesons in heavy-ion collisions at beam energies of 1 to 2 A GeV has systematically been investigated with the kaon spectrometer KaoS. The ratio of the K+ production excitation function for Au+Au and for C+C reactions increases with decreasing beam energy, which is expected for a soft nuclear equation-of-state. A comprehensive study of the K+ and of the K− emission as a function of the size of the collision system, of the collision centrality, of the kaon energy, and of the polar emission angle has been performed. The K−/K+ ratio is found to be nearly constant as a function of the collision centrality and can be explained by the dominance of strangeness exchange. On the other hand, the spectral slopes and the polar emission patterns are different for K− and for K+. Furthermore the azimuthal distribution of the particle emission has been investigated. K+ mesons and pions are emitted preferentially perpendicular to the reaction plane as well in Au+Au as in Ni+Ni collisions. In contrast for K− mesons in Ni+Ni reactions an in-plane flow was observed for the first time at these incident energies.
20377841
First evidence for different freeze-out conditions for kaons and antikaons observed in heavy-ion collisions.
Differential production cross sections of K- and K+ mesons have been measured in Ni+Ni and Au+Au collisions at a beam energy of 1.5 A GeV. The K(-)/K(+) ratio is found to be nearly constant as a function of the collision centrality and system size. The spectral slopes and the polar emission pattern differ for K- and K+ mesons. These observations indicate that K+ mesons decouple earlier from the fireball than K- mesons.
126051003
Charged pion production in heavy ion collision at SIS energies
120745369
Precise quark masses from R(s)
We discuss the extraction of the charm- and bottom-quark mass from the experimentally measured R -ratio in combination with higher order QCD corrections to moments of the vacuum polarization function. The results for the MS ¯ -masses are m c ( 3 GeV ) = 0.986 ( 13 ) GeV and m b ( 10 GeV ) = 3.609 ( 25 ) GeV .
118852549
QCD decoupling at four loops
Abstract We present the matching condition for the strong coupling constant α s ( n f ) at a heavy quark threshold to four loops in the modified minimal subtraction scheme. Our results lead to further decrease of the theoretical uncertainty of the evolution of the strong coupling constant through heavy quark thresholds. Using a low energy theorem we furthermore derive the effective coupling of the Higgs boson to gluons (induced by a virtual heavy quark) in four- and (partially) through five-loop approximation.
7975024
Recent Results on Four-loop Tadpoles
The experimental measurable R -ratio can be used to perform a precise determination of the charm- and bottom-quark mass with the help of theoretical computable expansion coefficients of the vacuum polarization function. The four-loop contributions in perturbative QCD to the first two expansion coefficients of the vacuum polarization functions are presented.
28798455
Four loop QCD corrections and Master Integrals for the rho-Parameter
The calculation of the four-loop QCD corrections to the electroweak -parameter arising from top- and bottom-quarks of the order O(GF m 2 3) is discussed. In particular the computation of the numerous master integrals in the standard and "-nite basis is addressed.
12101220
QCD corrections to single top quark production in electron-photon interactions
Abstract.Single top quark production in electron-photon interactions provides a clean environment for the measurement of the Cabibbo-Kobayashi-Maskawa matrix element Vtb. Aiming at an experimental precision at the percent level the knowledge of radiative corrections is important. In this paper we present results for the radiative corrections in quantum chromodynamics.