Search results for "quantum chromodynamics"
showing 10 items of 1027 documents
The strange-quark mass from QCD sum rules in the pseudoscalar channel
1997
QCD Laplace transform sum rules, involving the axial-vector current divergences, are used in order to determine the strange quark mass. The two-point function is known in QCD up to four loops in perturbation theory, and up to dimension-six in the non-perturbative sector. The hadronic spectral function is reconstructed using threshold normalization from chiral symmetry, together with experimental data for the two radial excitations of the kaon. The result for the running strange quark mass, in the $\bar{MS}$ scheme at a scale of 1 ${GeV}^{2}$ is: ${\bar m}_{s}(1 GeV^{2}) = 155 \pm 25 {MeV}$.
QCD vacuum condensates from tau-lepton decay data
2006
The QCD vacuum condensates in the Operator Product Expansion are extracted from the final ALEPH data on vector and axial-vector spectral functions from $\tau$-decay. Weighted Finite Energy Sum Rules are employed in the framework of both Fixed Order and Contour Improved Perturbation Theory. An overall consistent picture satisfying chirality constraints can be achieved only for values of the QCD scale below some critical value $\Lambda\simeq350 {MeV}$. For larger values of $\Lambda$, perturbation theory overwhelms the power corrections. A strong correlation is then found between $\Lambda$ and the resulting values of the condensates. Reasonable accuracy is obtained up to dimension $d=8$, beyon…
NLO corrections to processes with electroweak bosons at hadron colliders
2015
For many processes with electroweak bosons in the final state, next-to-leading order QCD and, in some cases, electroweak corrections have been calculated for differential cross sections at hadron colliders. The calculational techniques and some phenomenological implications are reviewed in this contribution. Processes discussed include vector boson fusion and vector boson scattering, production of two and three electroweak bosons, potentially with jets, (VV j, VV jj and VVV events) and some Higgs production processes. All QCD corrections are implemented in the publicly available VBFNLO program package.
Prospects of medium tomography using back-to-back hadron correlations
2006
We discuss the prospects of extracting information about the bulk QCD matter distribution and evolution on the basis of hard hadronic back-to-back correlations in ultrarelativistic heavy-ion collisions. Using both hydrodynamical and parametrized evolution models for the spacetime evolution of the produced matter, which have been tested against RHIC data, we study six different setups for the spacetime dependence of hard-parton energy losses. Assuming that the energy loss of hard partons traversing the medium is radiative and calculable in the BDMPS formalism, we adjust one parameter, the quenching power scale, to the measured R_AA in each of the setups and study the systematic variations of…
Charmonium properties in hot quenched lattice QCD
2012
We study the properties of charmonium states at finite temperature in quenched QCD on large and fine isotropic lattices. We perform a detailed analysis of charmonium correlation and spectral functions both below and above $T_c$. Our analysis suggests that both S wave states ($J/\psi$ and $\eta_c$) and P wave states ($\chi_{c0}$ and $\chi_{c1}$) disappear already at about $1.5 T_c$. The charm diffusion coefficient is estimated through the Kubo formula and found to be compatible with zero below $T_c$ and approximately $1/\pi T$ at $1.5 T_c\lesssim T\lesssim 3 T_c$.
Order-$\alpha_s^3$ determination of the strange quark mass
1996
We present a QCD sum rule calculation of the strange-quark mass including four-loop QCD corrections to the correlator of scalar currents. We obtain $\bar m_s(1$ GeV$)=205.5\pm 19.1$ MeV.
NNLL momentum-space threshold resummation in direct top quark production at the LHC
2014
We update the theoretical precision of the total cross section for direct top quark production at the LHC by extending the threshold resummation to the next-to-next-to-leading logarithmic accuracy.
Scrutinizing the Green's functions of QCD: Lattice meets Schwinger-Dyson
2009
Proceedings of the International Workshop Light Cone 2009 (LC2009): Relativistic Hadronic and Particle Physics. Sao Jose dos Campos, Brazil, July 8-13, 2009.
Gauge-invariant resummation formalism for two-point correlation functions
1996
The consistent description of unstable particles, renormalons, or other Schwinger--Dyson-type of solutions within the framework of perturbative gauge field theories necessitates the definition and resummation of off-shell Green's functions, which must respect several crucial physical requirements. A formalism is presented for resummation of off-shell two-point correlation functions, which is mainly based on arguments of analyticity, unitarity, gauge invariance and renormalizability. The analytic results obtained with various methods, including the background field gauges and the pinch technique are confronted with the physical requirements imposed; to one-loop order the pinch technique appr…
Effective field theory description of the pion form factor
1997
7 páginas, 2 figuras.-- PACS: 14.40.Aq; 13.40.Gp; 13.6O.Fz; 12.39.Fe.-- arXiv:hep-ph/9707347v1