15203131
Precise charm- and bottom-quark masses: Theoretical and experimental uncertainties
We consider recent theoretical and experimental improvements in determining charm- and bottom-quark masses. We present a new, improved evaluation of the contribution of the gluon condensate 〈αsG2/π〉 to the charm mass determination and a detailed study of potential uncertainties in the continuum cross section for $b\bar b$ production, together with a study of the parametric uncertainty from the αs-dependence of our results. The final results, mc(3 GeV) = 986(13) MeV and mb(mb) = 4163(16) MeV, together with the closely related lattice determination mc(3 GeV) = 986(6) MeV, currently represent the most precise determinations of these two fundamental standard-model parameters. We critically analyze the theoretical and experimental uncertainties.
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 .
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.
119202777
Two-Loop Virtual Corrections to Drell-Yan Production at order $\alpha_s \alpha^3$
The Drell-Yan mechanism for the production of lepton pairs is one of the most basic processes for physics studies at hadron colliders. It is therefore important to have accurate theoretical predictions. In this work we compute the two-loop virtual mixed QCD x QED corrections to Drell-Yan production. We evaluate the Feynman diagrams by decomposing the amplitudes into a set of known master integrals and their coefficients, which allows us to derive an analytical result. We also perform a detailed study of the ultraviolet and infrared structure of the two-loop amplitude and the corresponding poles in epsilon.
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.
116139290
Improving the precision of light quark mass determinations
We discuss the concepts and the framework of the renormalization procedure in regularization-invariant momentum subtraction schemes. These schemes are used in the context of lattice simulations for the determination of physical quantities like light quark masses. We focus on the renormalization procedure with a symmetric subtraction point of a quark mass and discuss its conversion from the RI/SMOM scheme to the MSbar scheme. A symmetric subtraction point allows for a lattice calculation with a reduced contamination from infrared effects. The perturbative series for the resulting matching factor at next-to-leading order is better behaved for the symmetric momentum configuration than for the exceptional one which can decrease the uncertainty in light quark mass determinations.
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.
119152945
Soft nuclear equation-of-state from heavy-ion data and implications for compact stars
Measurements of kaon production at subthreshold energies in heavy-ion collisions point to a soft nuclear equation-of-state for densities up to 2-3 times nuclear matter saturation density. We apply these results to study the implications on compact star properties, especially in the context of the recent measurement of the two solar mass pulsar PSR J1614-2230. The implications are two-fold: Firstly, the heavy-ion results constrain nuclear matter at densities relevant to light neutron stars. Hence, a radius measurement could provide information about the density dependence of the symmetry energy which is a crucial quantity in nuclear physics. Secondly, the information on the nucleon potential obtained from the analysis of the heavy-ion data can be combined with restrictions from causality on the nuclear equation-of-state. From this we can derive a limit for the highest allowed compact star mass of three solar masses.
54021017
Implications for compact stars of a soft nuclear equation of state from heavy-ion data
We study the implications on compact star properties of a soft nuclear equation of state determined from kaon production at subthreshold energies in heavy-ion collisions. On one hand, we apply these results to study radii and moments of inertia of light neutron stars. Heavy-ion data provides constraints on nuclear matter at densities relevant for those stars and, in particular, to the density dependence of the symmetry energy of nuclear matter. On the other hand, we derive a limit for the highest allowed neutron star mass of three solar masses. For that purpose, we use the information on the nucleon potential obtained from the analysis of the heavy-ion data combined with causality on the nuclear equation of state.
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.
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.