Search results for "Interaction"
showing 10 items of 5710 documents
Theoretical overview on tau physics
2006
8 páginas, 2 figuras, 1 tabla.-- PACS numbers: 14.60.Fg, 13.30.Ce, 12.20.Fv.-- Comunicación presentada a la International Workshop on Tau-Charm Physics (Charm2006), celebrada del 5 al 7 de Junio de 2006 en Beijing (China).-- arXiv:hep-ph/0609138v1
New Strong Interactions: From QCD to LHC
2006
The concept of strong interactions need not be limited to the sector of physics taken by QCD. While this domain is investigated by RHIC, LHC will be able to probe potential new strong interactions simultaneously: Finding the precise mechanism for electroweak symmetry breaking is one of the prime problems of physics. Intricately linked to this point is the question after the true nature or even the existence of the Higgs boson. Here, we present stronly interacting theories providing an explanation for the hierarchy problem and leading to a light composite Higgs boson, favoured by experimental data. Our variation of the standard model is consistent with precision data. We achieve this accorda…
Next-to-leading order QCD corrections toW+W+andW−W−production in association with two jets
2014
We present a study of ${W}^{+}{W}^{+}jj$ and ${W}^{\ensuremath{-}}{W}^{\ensuremath{-}}jj$ production including leptonic decays in hadron-hadron collisions. The full electroweak and QCD induced contributions and their interferences are calculated at leading order. We find that, for inclusive cuts, the interference effects can be large if the jets are produced with large transverse momentum where, however, the production rate is suppressed. We also discuss the vector-boson-fusion cuts and show the validity of the vector-boson-fusion approximation. The next-to-leading order QCD corrections to the QCD-induced channels are also calculated. Compared to the previous calculation, we allow the inter…
Gluonic effects in vector meson photoproduction at large momentum transfers
2001
Non-perturbative QCD mechanisms are of fundamental importance in strong interaction physics. In particular, the flavor singlet axial anomaly leads to a gluonic pole mechanism which has been shown to explain the $\eta^{\prime}$ mass, violations of the OZI rule and more recently the proton spin. We show here that the interaction derived from the gluonic pole exchange explains the high momentum transfer behavior of the photoproduction cross sections of vector mesons at JLab energies.
The rho NN coupling with direct coupling and loops
2002
Starting from a gauge formalism of $\rho$ mesons, pions and baryons we evaluate the $\rho$ coupling to the nucleon, including the direct coupling provided by the Lagrangians, plus contributions from loops with the virtual pion cloud. We find a contribution to the magnetic $\rho$ coupling to the nucleon from pionic loops of the same size as the direct coupling, which is, however, still small compared to the empirical values. This finding goes in line with chiral formulations of the strong interaction of mesons at low energies where, unlike the scalar mesons which are mostly built of a pion (kaon) cloud, the $\rho$ meson stands as a genuine QCD state with intrinsic properties not tied to thos…
Lattice QCD and the anomalous magnetic moment of the muon
2019
The anomalous magnetic moment of the muon, a_mu, has been measured with an overall precision of 540 ppb by the E821 experiment at BNL. Since the publication of this result in 2004 there has been a persistent tension of 3.5 standard deviations with the theoretical prediction of a_mu based on the Standard Model. The uncertainty of the latter is dominated by the effects of the strong interaction, notably the hadronic vacuum polarisation (HVP) and the hadronic light-by-light (HLbL) scattering contributions, which are commonly evaluated using a data-driven approach and hadronic models, respectively. Given that the discrepancy between theory and experiment is currently one of the most intriguing …
Foundations of the Quantum Chromodynamics
2015
Quantum chromodynamics (QCD) is a theory to describe the strong interaction in hadrons. It was developed in the history of understanding the structure of the hadrons. In the 1950s, a large number of hadrons were discovered in experiments.
Alternative large-n limit for QCD and its implications for low-energy nuclear phenomena
1990
The Corrigan-Ramond model for large-{ital N} QCD is analyzed in detail. The spectrum, leading-order results for interactions, and an effective Lagrangian describing large-{ital N} interactions are derived. This Lagrangian, when quantized, provides an effective quantum field theory for mesons and baryons. The applicability of such a theory to low-energy nuclear phenomena is studied. The model has features that distinguish it clearly from standard large-{ital N} QCD.
QCD Condensates for the Light Quark V-A Correlator
2003
We use the procedure of pinched-weight Finite Energy Sum Rules (pFESR) to determine the OPE coefficients a_6, ...,a_16 of the flavor ud V-A correlator in terms of existing hadronic tau decay data. We show by appropriate weight choices that the error on the dominant d=6 contribution, which is known to be related to the K -> Pi Pi matrix elements of the electroweak penguin operator in the chiral limit, may be reduced to below the ~15% level. The values we obtain for the OPE coefficients with d>8 are shown to naturally account for the discrepancies between our results for the d=6 and d=8 terms and those of previous analyses, which were obtained neglecting d>8 contributions.
SIMPRE1.2: Considering the hyperfine and quadrupolar couplings and the nuclear spin bath decoherence
2016
SIMPRE is a fortran77code which uses an effective electrostatic model of point charges to predict the magnetic behavior of rare-earth-based mononuclear complexes. In this manuscript, we present SIMPRE1.2, which now takes into account two further phenomena.Firstly, SIMPRE now considers the hyperfine and quadrupolar interactions within the rare-earth ion, resulting in a more complete and realistic set of energy levels and wave functions. Secondly,and in order to widen SIMPRE’s predictive capabilities regarding potential molecular spin qubits, it now includes a routine that calculates an upper-bound estimate of the decoherence time considering only the dipolar coupling between the electron spi…