Search results for "Reno"
showing 10 items of 1031 documents
The gluon spin in the chiral bag model
2000
We study the gluon polarization contribution at the quark model renormalization scale to the proton spin, $\Gamma$, in the chiral bag model. It is evaluated by taking the expectation value of the forward matrix element of a local gluon operator in the axial gauge $A^+=0$. It is shown that the confining boundary condition for the color electric field plays an important role. When a solution satisfying the boundary condition for the color electric field, which is not the conventionally used but which we favor, is used, the $\Gamma$ has a positive value for {\it all} bag radii and its magnitude is comparable to the quark spin polarization. This results in a significant reduction in the relativ…
Resummation prediction on top quark transverse momentum distribution at largepT
2012
We study the factorization and resummation of t-channel top quark transverse momentum distribution at large pT in the SM at both the Tevatron and the LHC with soft-collinear effective theory. The cross section in the threshold region can be factorized into a convolution of hard, jet and soft functions. In particular, we first calculate the NLO soft functions for this process, and give a RG improved cross section by evolving the different functions to a common scale. Our results show that the resummation effects increase the NLO results by about 9%-13% and 4%-9% when the top quark pT is larger than 50 and 70 GeV at the Tevatron and the 8 TeV LHC, respectively. Also, we discuss the scale inde…
Quark masses and the chiral condensate with a non-perturbative renormalization procedure
1999
We determine the quark masses and the chiral condensate in the MSbar scheme at NNLO from Lattice QCD in the quenched approximation at beta=6.0, beta=6.2 and beta=6.4 using both the Wilson and the tree-level improved SW-Clover fermion action. We extract these quantities using the Vector and the Axial Ward Identities and non-perturbative values of the renormalization constants. We compare the results obtained with the two methods and we study the O(a) dependence of the quark masses for both actions.
Light Quark Masses from Lattice Quark Propagators at Large Momenta
1999
We compute non-perturbatively the average up-down and strange quark masses from the large momentum (short-distance) behaviour of the quark propagator in the Landau gauge. This method, which has never been applied so far, does not require the explicit calculation of the quark mass renormalization constant. Calculations were performed in the quenched approximation, by using O(a)-improved Wilson fermions. The main results of this study are ml^RI(2GeV)=5.8(6)MeV and ms^RI(2GeV)=136(11)MeV. Using the relations between different schemes, obtained from the available four-loop anomalous dimensions, we also find ml^RGI=7.6(8)MeV and ms^RGI=177(14)MeV, and the MSbar-masses, ml^MS(2GeV)=4.8(5)MeV and …
Spin-one-Ising model for (CO)1?x (N2) x mixtures: A finite size scaling study of random-field-type critical phenomena
1995
A qualitative model for solid mixtures of diatomic molecules, where one species (called CO, to be specific) carries both a dipole moment and a quadrupole moment, while the other species (calledN 2) has only a quadrupole moment, is studied by Monte Carlo methods. We use spinsS i =±1 to represent the orientations of the CO electric dipole moment, if the lattice sitei is taken by a CO molecule, whileS i =0 if the site is taken by anN 2 molecule. Assuming nearest-neighbor antiferroelectric interactions between CO molecules, and a bilinear dipole-quadrupole coupling between CO andN 2, the randomly quenchedN 2 molecules act like random fields do in the random field Ising model. In previous work i…
FINITE-RANGE SEPARABLE PAIRING INTERACTION WITHIN NEW N[sup 3]LO DFT APPROACH
2011
For over four decades, the Skyrme functional within various parametrizations has been used to calculate nuclear properties. In the last few years there was a number of attempts to improve its performance and introduce generalized forms. In particular, the most general phenomenologi‐cal quasi‐local energy density functional, which contains all combinations of density, spin‐density, and their derivatives up to the sixth order (N3LO), was proposed in reference [1]. Since in the phe‐nomenological functional approaches the particle‐particle (pp) interaction channel is treated independently from the particle‐hole (ph) channel, there remains a question of what pairing interaction is suitable to us…
A Tutorial Approach to the Renormalization Group and the Smooth Feshbach Map
2006
2.1 Relative Bounds on the Interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2 The Feshbach Map and Pull-Through Formula . . . . . . . . . . . . . . . . . 4 2.3 Elimination of High-Energy Degrees of Freedom . . . . . . . . . . . . . . . . 5 2.4 Normal form of Hamiltonians . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.5 Banach Space of Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.6 The Renormalization Map Rρ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Dimensional Regularization. Ultraviolet and Infrared Divergences
2015
The cornerstone of Quantum Field Theory is renormalization. We shall speak more about in the next chapters. Before, it is necessary to discuss the method. The best and most simple is, of course, dimensional regularization (doesn’t break the symmetries, doesn’t violate the Ward Identities, preserves Lorentz invariance, etc.). When explained consistently, it becomes very simple and clear. Here, we shortly discuss ultraviolet (UV) and infrared (IR) divergences with a few examples. However, in Chap. 8, we shall extensively treat one-loop two and three-point functions and analyse many more examples of IR and UV divergences.
Massive Spin One and Renormalizable Gauges
2015
For many decades of the last century, physicists were struggling to define consistent (renormalizable and unitarity preserving) models for spin-one massive particles (Proca fields). As we know, this was beautifully achieved by Weinberg, Salam and Glashow in 1967 when they proposed an electroweak unified theory which we now call the Standard Model. The electroweak symmetry breaking mechanism, among other things, generates mass terms for the W and Z bosons, while preserving renormalizability and unitarity. The longitudinal degrees of freedom of the massive spin-one particles are given by the Goldostone bosons. Choosing one gauge or another might seem just a matter of convenience and in most c…
Renormalization aspects of chaotic strings
2014
Chaotic strings are a class of non-hyperbolic coupled map lattices, exhibiting a rich structure of complex dynamical phenomena with a surprising correspondence to physical contents. In this paper we introduce different types and models for chaotic strings, where 2B-strings with finite length are considered in detail. We demonstrate possibilities to extract renormalized quantities, which are expected to describe essential properties of the string.