Search results for "Chromodynamics"
showing 10 items of 1030 documents
Form-factors and current correlators: chiral couplingsL10r(μ) andC87r(μ) at NLO in 1/NC
2008
Using the resonance chiral theory Lagrangian, we perform a calculation of the vector and axial-vector two-point functions at the next-to-leading order (NLO) in the 1/N-C expansion. We have analyzed these correlators within the single-resonance approximation and have also investigated the corrections induced by a second multiplet of vector and axial-vector resonance states. Imposing the correct QCD short-distance constraints, one determines the difference of the two correlators Pi(t) equivalent to Pi(VV)(t)-Pi(AA)(t) in terms of the pion decay constant and resonance masses. Its low momentum expansion fixes then the low-energy chiral couplings L 1 0 and C 8 7 at NLO, keeping full control of t…
Scalar glueball spectrum
2006
I discuss scenarios for scalar glueballs using arguments based on sum rules, spectral decomposition, the $\frac{1}{{N}_{c}}$ approximation, the scales of the strong interaction and the topology of the flux tubes. I analyze the phenomenological support of those scenarios and their observational implications. My investigations hint a rich low lying glueball spectrum.
Old and new physics interpretations of the NuTeV anomaly
2001
We discuss whether the NuTeV anomaly can be explained, compatibly with all other data, by QCD effects (maybe, if the strange sea is asymmetric, or there is a tiny violation of isospin), new physics in propagators or couplings of the vector bosons (not really), loops of supersymmetric particles (no), dimension six operators (yes, for one specific SU(2)-invariant operator), leptoquarks (not in a minimal way), extra U(1) gauge bosons (maybe: an unmixed Z' coupled to B-3L_mu also increases the muon g-2 by about 10^{-9} and gives a `burst' to cosmic rays above the GZK cutoff).
Violation of quark-hadron duality and spectral chiral moments in QCD
2010
We analyze the spectral moments of the V - A two-point correlation function. Using all known short-distance constraints and the most recent experimental data from tau decays, we determine the lowest spectral moments, trying to assess the uncertainties associated with the so-called violations of quark-hadron duality. We have generated a large number of acceptable spectral functions, satisfying all conditions, and have used them to extract the wanted hadronic parameters through a careful statistical analysis. We obtain accurate values for the chi PT couplings L-10 and C-87, and a realistic determination of the dimension six and eight contributions in the operator product expansion, O-6 = (-5.…
Hadron structure at small momentum transfer
2008
Giving three examples, the form factors of the nucleon, the polarisability of the charged pion and the interference of the $S_{11}(1535)$ with the $D_{13}(1520)$ excitation of the nucleon in the $\eta p$-decay channel, it is argued that the hadron structure at low momentum transfer is highly significant for studying QCD.
Photon Plus Jet Production in Large-Q2 ep Collisions at Next-to-Leading Order QCD
1999
The production of photons accompanied by jets in large-Q2 deep inelastic ep scattering is calculated in next-to-leading order. We describe how to consistently include contributions from quark-to-photon fragmentation and give numerical results relevant for HERA experiments.
Pion transverse momentum dependent parton distributions in the Nambu and Jona-Lasinio model
2015
An explicit evaluation of the two pion transverse momentum dependent parton distributions at leading twist is presented, in the framework of the Nambu-Jona Lasinio model with Pauli-Villars regularization. The transverse momentum dependence of the obtained distributions is generated solely by the dynamics of the model. Using these results, the so called generalized Boer-Mulders shift is studied and compared with recent lattice data. The obtained agreement is very encouraging, in particular because no additional parameter has been introduced. A more conclusive comparison would require a precise knowledge of the QCD evolution of the transverse momentum dependent parton distributions under scru…
The vector form factor at the next-to-leading order in 1/N(C): chiral couplings L9(mu) and C88(mu) - C90(mu)
2010
24 páginas, 3 figuras, 2 tablas.-- arXiv:1011.5771v1.
The QCD Effective Charge to All Orders
2002
Using the pinch technique, we show how to construct the QCD effective charge to all orders.
Origin of the Large Perturbative Corrections to Higgs Production at Hadron Colliders
2008
The very large K-factor for Higgs-boson production at hadron colliders is shown to result from enhanced perturbative corrections of the form (C_A\pi\alpha_s)^n, which arise in the analytic continuation of the gluon form factor to time-like momentum transfer. These terms are resummed to all orders in perturbation theory using the renormalization group. After the resummation, the K-factor for the production of a light Higgs boson at the LHC is reduced to a value close to 1.3.