Perturbative QCD prediction for πp → ρp density matrix elements

1989 ◽  
Author(s):  
Huayi Zhang ◽  
Glennys R. Farrar
Keyword(s):  
Density Matrix ◽  
Perturbative Qcd ◽  
Matrix Elements

scholarly journals Spin Density Matrix Elements in Exclusive Production of Omega Mesons at HERMES

2016 ◽  
Vol 40 ◽  
pp. 1660063
Author(s):  
Hrachya Marukyan
Keyword(s):  
Density Matrix ◽  
Spin Density ◽  
Cross Section ◽  
Transverse Cross Section ◽  
Spin Density Matrix ◽  
Pion Pole ◽  
Matrix Elements ◽  
Unnatural Parity ◽  
Proton Data ◽  
Parity Exchange

Exclusive electroproduction of [Formula: see text] mesons on unpolarized hydrogen and deuterium targets is studied at HERMES in the kinematic region of [Formula: see text], [Formula: see text], and [Formula: see text]. The data were accumulated during the 1996-2007 running period using the [Formula: see text] longitudinally polarized electron or positron beams at HERA. The determination of the virtual-photon longitudinal-to-transverse cross-section ratio shows that a considerable part of the cross section arises from transversely polarized photons. Spin density matrix elements are derived and presented in projections of [Formula: see text] or [Formula: see text]. Violation of s-channel helicity conservation is observed for some of these elements. A sizable contribution from unnatural-parity-exchange amplitudes is found and the phase shift between those amplitudes that describe transverse [Formula: see text] production by longitudinal and transverse virtual photons is determined for the first time. Good agreement is found between the HERMES proton data and results of a pQCD-inspired phenomenological model that includes pion-pole contributions.

scholarly journals Exact density matrix elements for a driven dissipative system described by a quadratic Hamiltonian

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sh. Saedi ◽  
F. Kheirandish
Keyword(s):  
Density Matrix ◽  
Equations Of Motion ◽  
Dissipative System ◽  
Characteristic Functions ◽  
Matrix Elements ◽  
Exact Density ◽  
Quadratic Hamiltonian ◽  
Heisenberg Equations ◽  
Reduced Density ◽  
Heisenberg Equations Of Motion

AbstractFor a prototype quadratic Hamiltonian describing a driven, dissipative system, exact matrix elements of the reduced density matrix are obtained from a generating function in terms of the normal characteristic functions. The approach is based on the Heisenberg equations of motion and operator calculus. The special and limiting cases are discussed.

scholarly journals Exact evaluation of density matrix elements for the Heisenberg chain

2006 ◽  
Vol 2006 (12) ◽  
pp. P12017-P12017 ◽  
Author(s):  
Jun Sato ◽  
Masahiro Shiroishi ◽  
Minoru Takahashi
Keyword(s):  
Density Matrix ◽  
Matrix Elements ◽  
Heisenberg Chain ◽  
Exact Evaluation

Off-diagonal helicity density matrix elements for vector mesons produced in polarized

1999 ◽  
Vol 11 (3) ◽  
pp. 529 ◽  
Author(s):  
M. Anselmino ◽  
M. Bertini ◽  
F. Caruso ◽  
F. Murgia ◽  
P. Quintairos
Keyword(s):  
Density Matrix ◽  
Matrix Elements ◽  
Vector Mesons

Spin-Density Matrix Elements and Regge Cuts

1970 ◽  
Vol 1 (6) ◽  
pp. 1847-1848
Author(s):  
Robert L. Thews
Keyword(s):  
Density Matrix ◽  
Spin Density ◽  
Spin Density Matrix ◽  
Matrix Elements
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