Search results for "propagator"
showing 10 items of 173 documents
Tree-Loop Duality Relation beyond simple poles
2013
We develop the Tree-Loop Duality Relation for two- and three-loop integrals with multiple identical propagators (multiple poles). This is the extension of the Duality Relation for single poles and multi-loop integrals derived in previous publications. We prove a generalization of the formula for single poles to multiple poles and we develop a strategy for dealing with higher-order pole integrals by reducing them to single pole integrals using Integration By Parts.
Ghost spectral function from the spectral Dyson-Schwinger equation
2021
We compute the ghost spectral function in Yang-Mills theory by solving the corresponding Dyson-Schwinger equation for a given input gluon spectral function. The results encompass both scaling and decoupling solutions for the gluon propagator input. The resulting ghost spectral function displays a particle peak at vanishing momentum and a negative scattering spectrum, whose infrared and ultraviolet tails are obtained analytically. The ghost dressing function is computed in the entire complex plane, and its salient features are identified and discussed.
Search for long-lived neutral particles produced in pp collisions at s=13 TeV decaying into displaced hadronic jets in the ATLAS inner detector and …
2020
A search is presented for pair production of long-lived neutral particles using 33 fb − 1 of √ s = 13 TeV proton–proton collision data, collected during 2016 by the ATLAS detector at the LHC. This search focuses on a topology in which one long-lived particle decays in the ATLAS inner detector and the other decays in the muon spectrometer. Special techniques are employed to reconstruct the displaced tracks and vertices in the inner detector and in the muon spectrometer. One event is observed that passes the full event selection, which is consistent with the estimated background. Limits are placed on scalar boson propagators with masses from 125 GeV to 1000 GeV decaying into pairs of …
LocalD=4field theory onκ-deformed Minkowski space
2000
We describe the local $D=4$ field theory on $\ensuremath{\kappa}$-deformed Minkowski space as a nonlocal relativistic field theory on standard Minkowski space-time. For simplicity the case of a $\ensuremath{\kappa}$-deformed scalar field $\ensuremath{\varphi}$ with the interaction $\ensuremath{\lambda}{\ensuremath{\varphi}}^{4}$ is considered, and the $\ensuremath{\kappa}$-deformed interaction vertex is described. It appears that the fundamental mass parameter $\ensuremath{\kappa}$ plays the role of regularizing the imaginary Pauli-Villars mass in the $\ensuremath{\kappa}$-deformed propagator.
Improving the ultraviolet behavior in baryon chiral perturbation theory
2004
We introduce a new formulation of baryon chiral perturbation theory which improves the ultraviolet behavior of propagators and can be interpreted as a smooth cutoff regularization scheme. It is equivalent to the standard approach, preserves all symmetries and therefore satisfies the Ward identities. Our formulation is equally well defined in the vacuum, one- and few-nucleon sectors of the theory. The equations (Bethe-Salpeter, Lippmann-Schwinger, etc.) for the scattering amplitudes of the few-nucleon sector are free of divergences in the new approach. Unlike the usual cutoff regularization, our 'cutoffs' are parameters of the Lagrangian and do not have to be removed.
On the chiral covariant approach to ρρ scattering
2017
We examine in detail a recent work (D.~G\"ulmez, U.-G.~Mei\ss ner and J.~A.~Oller, Eur. Phys. J. C 77:460 (2017)), where improvements to make $\rho\rho$ scattering relativistically covariant are made. The paper has the remarkable conclusion that the $J=2$ state disappears with a potential which is much more attractive than for $J=0$, where a bound state is found. We trace this abnormal conclusion to the fact that an "on-shell" factorization of the potential is done in a region where this potential is singular and develops a large discontinuous and unphysical imaginary part. A method is developed, evaluating the loops with full $\rho$ propagators, and we show that they do not develop singula…
〈VAP〉 Green function in the resonance region
2004
Abstract We analyze the 〈 V A P 〉 three-point function of vector, axial-vector and pseudoscalar currents. In the spirit of large N C , a resonance dominated Green function is confronted with the leading high-energy behaviour from the operator product expansion. The matching is shown to be fully compatible with a chiral resonance Lagrangian and it allows to determine some of the chiral low-energy constants of O ( p 6 ) .
Connection between certain massive and massless diagrams
1996
A useful connection between two-loop massive vacuum integrals and one-loop off-shell triangle diagrams with massless internal particles is established for arbitrary values of the space-time dimension {ital n}. {copyright} {ital 1996 The American Physical Society.}
Coherent and incoherent η-photoproduction from nuclei
1991
Abstract Elastic and inelastic η-photoproduction from complex nuclei is studied in a distorted-wave impulse approximation (DWIA) framework. The elementary operator is obtained by using a dynamical model which employs the reactions π N→ π N, π N→ ππ N and π − p→ η n to fix the hadronic vertex as well as the isobar propagators and the process γ N→ π N to constrain the electromagnetic vertex. The nuclear structure input for the inelastic transitions has been extracted from electron-scattering form factors. The η final-state interaction has been included via a simple optical potential using the ηN t -matrix as an input. We find that coherent η-production is dominated by the D 13 (1520) isobar w…
Finite-size Scaling of Meson Propagators
2001
Using quenched chiral perturbation theory we compute meson correlation functions at finite volume and fixed gauge field topology. We also present the corresponding analytical predictions for the unquenched theory at fixed gauge field topology. These results can be used to measure the low-energy parameters of the chiral Langrangian from lattice simulations in volumes much smaller than one pion Compton wavelength.