Search results for "RENORMALIZATION"
showing 10 items of 470 documents
The Hunt for New Physics at the Large Hadron Collider
2010
233 páginas.-- AHEP Group: et al..-- El Pdf del artículo es la versión pre-print: arXiv.1001.2693v1.-- Trabajo presentado al "The International Workshop on Beyond the Standard Model Physics and LHC Signatures (BSM-LHC) celebrado en Boston (USA) del 2 al 4 de junio de 2009.
From transition magnetic moments to majorana neutrino masses
2005
It is well known that a majorana mass induces a (small) transition magnetic moment. The converse is also true; in this paper we estimate the loop contribution of transition magnetic moments $[\mu]_{\alpha \beta}$ to the neutrino mass matrix $[m]_{\alpha \beta}$. We show that for hierarchical neutrino masses, the contribution of $[\mu]_{e \tau}$ to $[m]_{e \tau}$ can exceed the experimental value of $[m]_{e \tau}$.
Muon Anomaly from Lepton Vacuum Polarization and The Mellin--Barnes Representation
2008
We evaluate, analytically, a specific class of eighth--order and tenth--order QED contributions to the anomalous magnetic moment of the muon. They are generated by Feynman diagrams involving lowest order vacuum polarization insertions of leptons $l=e,\mu$, and $\tau$. The results are given in the form of analytic expansions in terms of the mass ratios $m_e/m_\mu$ and $m_\mu/m_\tau$. We compute as many terms as required by the error induced by the present experimental uncertainty on the lepton masses. We show how the Mellin--Barnes integral representation of Feynman parametric integrals allows for an easy analytic evaluation of as many terms as wanted in these expansions and how its underlyi…
B parameters of the complete set of matrix elements of delta B = 2 operators from the lattice
2001
We compute on the lattice the ``bag'' parameters of the five (Delta B = 2) operators of the supersymmetric basis, by combining their values determined in full QCD and in the static limit of HQET. The extrapolation of the QCD results from the accessible heavy-light meson masses to the B-meson mass is constrained by the static result. The matching of the corresponding results in HQET and in QCD is for the first time made at NLO accuracy in the MSbar(NDR) renormalization scheme. All results are obtained in the quenched approximation.
Running of the Charm-Quark Mass from HERA Deep-Inelastic Scattering Data
2017
Physics letters / B 775, 233 - 238 (2017). doi:10.1016/j.physletb.2017.11.002
Charm and hidden charm scalar mesons in the nuclear medium
2009
We study the renormalization of the properties of low-lying charm and hidden charm scalar mesons in a nuclear medium, concretely of the D-s0(2317) and the theoretical hidden charm state X(3700). We find that for the D-s0(2317), with negligible width at zero density, the width becomes about 100 MeV at normal nuclear-matter density, while in the case of the X(3700) the width becomes as large as 200 MeV. We discuss the origin of this new width and trace it to reactions occurring in the nucleus, while offering a guideline for future experiments testing these changes. We also show how those medium modifications will bring valuable information on the nature of the scalar resonances and the mechan…
s-wave pion-nucleus optical potential
2007
We calculate the s-wave part of the pion-nucleus optical potential using a unitarized chiral approach that has been previously used to simultaneously describe pionic hydrogen and deuterium data as well as low energy pi N scattering in the vacuum. This energy dependent model allows for additional isoscalar parts in the potential from multiple rescattering. We consider Pauli blocking and pion polarization in an asymmetric nuclear matter environment. Also, higher order corrections of the pi N amplitude are included. The model can accommodate the repulsion required by phenomenological fits, though the theoretical uncertainties are bigger than previously thought. At the same time, we also find a…
Gluon mass generation in the massless bound-state formalism
2013
We present a detailed, all-order study of gluon mass generation within the massless bound-state formalism, which constitutes the general framework for the systematic implementation of the Schwinger mechanism in non-Abelian gauge theories. The main ingredient of this formalism is the dynamical formation of bound states with vanishing mass, which give rise to effective vertices containing massless poles; these latter vertices, in turn, trigger the Schwinger mechanism, and allow for the gauge-invariant generation of an effective gluon mass. This particular approach has the conceptual advantage of relating the gluon mass directly to quantities that are intrinsic to the bound-state formation its…
Next-to-next-to-leading order corrections to three-jet observables in electron-positron annihilation.
2008
I report on a numerical program, which can be used to calculate any infrared safe three-jet observable in electron-positron annihilation to next-to-next-to-leading order in the strong coupling constant ${\ensuremath{\alpha}}_{s}$. The results are compared to a recent calculation by another group. Numerical differences in three color factors are discussed and explained.
State-of-the-art density matrix renormalization group and coupled cluster theory studies of the nitrogen binding curve.
2004
We study the nitrogen binding curve with the density matrix renormalization group (DMRG) and single-reference and multireference coupled cluster (CC) theory. Our DMRG calculations use up to 4000 states and our single-reference CC calculations include up to full connected hextuple excitations. Using the DMRG, we compute an all-electron benchmark nitrogen binding curve, at the polarized, valence double-zeta level (28 basis functions), with an estimated accuracy of 0.03mE_h. We also assess the performance of more approximate DMRG and CC theories across the nitrogen curve. We provide an analysis of the relative strengths and merits of the DMRG and CC theory under different correlation condition…