Search results for "EXPANSION"
showing 10 items of 630 documents
The W and Z boson spin observables as messengers of New Physics at LHC
2017
The successful LHC operation suggests going beyond the search of excess of events for the quest of new physics. We demonstrate that the eight multipole parameters describing the spin state of the W or Z bosons are able to disentangle their hidden production mechanism. They can be separately extracted from well defined angular asymmetries in the leptonic distribution of boson decays. The discriminating power of this analysis is well illustrated by: (i) polarised top quark decays, (ii) two body decay of heavy resonances, (iii) Drell-Yan production of Z plus jets, (iv) Z boson plus missing transverse energy.
General formulae for polarization observables in two-body break-up of deuteron photodisintegration
1988
The formal expressions of all possible polarization observables ind(γ,N)N with polarized photons and oriented deuterons are derived in terms of thet-matrix elements. Furthermore, using the multipole expansion of thet-matrix, all observables are expanded in terms of Legendre polynomials or associated functions, the coefficients of which are given as bilinear forms of the multipole moments and allow a model independent analysis of experimental data.
The SVZ plasmon
1985
The sum rule technique of Shifman, Vainshtein and Zakharov is applied to a non-relativistic many-body system, the homogeneous, degenerate electron gas. The operator product expansion for the nonrelativistic correlation function is derived and shown to be equivalent in lowest order to a moment expansion. The nonperturbative terms in this expansion characterize the interacting ground state (“vacuum”) of the system. For the electron gas they can be related to the correlation energy which is very well known. Following as close as possible the SVZ procedure the mass of the plasmon (i.e. the dispersion coefficient of the collective plasma excitation) is calculated and compared with results from c…
Riccati-Padé quantization and oscillatorsV(r)=grα
1993
We develop an alternative construction of bound states based on matching the Riccati threshold and asymptotic expansions via their two-point Pad\'e interpolation. As a form of quantization it gives highly accurate eigenvalues and eigenfunctions.
Watson’s theorem and theNΔ(1232)axial transition
2016
We present a new determination of the $N\mathrm{\ensuremath{\Delta}}$ axial form factors from neutrino induced pion production data. For this purpose, the model of Hernandez et al. [Phys. Rev. D 76, 033005 (2007)] is improved by partially restoring unitarity. This is accomplished by imposing Watson's theorem on the dominant vector and axial multipoles. As a consequence, a larger ${C}_{5}^{A}(0)$, in good agreement with the prediction from the off-diagonal Goldberger-Treiman relation, is now obtained.
self-consistent approach to describe unit-cell-parameter and volume variations with pressure and temperature
2021
A method is presented for the self-consistent description of the variations of unit-cell parameters of crystals with pressure and temperature.
A pedagogical approach to the Magnus expansion
2010
Time-dependent perturbation theory as a tool to compute approximate solutions of the Schrodinger equation does not preserve unitarity. Here we present, in a simple way, how the Magnus expansion (also known as exponential perturbation theory) provides such unitary approximate solutions. The purpose is to illustrate the importance and consequences of such a property. We suggest that the Magnus expansion may be introduced to students in advanced courses of quantum mechanics.
Optimized time-dependent perturbation theory for pulse-driven quantum dynamics in atomic or molecular systems
2003
We present a time-dependent perturbative approach adapted to the treatment of intense pulsed interactions. We show there is a freedom in choosing secular terms and use it to optimize the accuracy of the approximation. We apply this formulation to a unitary superconvergent technique and improve the accuracy by several orders of magnitude with respect to the Magnus expansion.
AN OPERATOR PRODUCT EXPANSION ANALYSIS OF e+e-ANNIHILATION DATA
2013
Perturbative Quantum Chromodynamics combined with the operator product expansion is expected to provide a framework for the description of phenomena in hadron interactions including contributions of nonperturbative origin. Applied to the correlator of two electromagnetic currents, this framework can be confronted with e+e-annihilation into hadrons. Data from the total hadronic e+e-cross-section have become much more precise in recent years and the power corrections in the operator product expansion, i.e. the vacuum condensates are expected to be determined with higher precision than previously. We present an analysis of the condensates of dimensions d = 2, 4 and 6 and find reasonably stable…
Towards a determination of the chiral couplings at NLO in 1/N-C: L-8(r)(μ) and C-38(r)(μ)
2007
14 pages.-- ISI Article Identifier: 000244120200039.-- ArXiv pre-print available at: http://arxiv.org/abs/hep-ph/0610290