Search results for "crisis"
showing 10 items of 860 documents
Proton spin polarizabilities from polarized Compton scattering
2007
Polarized Compton scattering off the proton is studied within the framework of subtracted dispersion relations for photon energies up to 300 MeV. As a guideline for forthcoming experiments, we focus the attention on the role of the proton's spin polarizabilities and investigate the most favorable conditions to extract them with a minimum of model dependence. We conclude that a complete separation of the four spin polarizabilities is possible, at photon energies between threshold and the $\Delta(1232)$ region, provided one can achieve polarization measurements with an accuracy of a few percent.
Proton spin and the cheshire cat principle
1991
Abstract We discuss the proton matrix element of the flavor-singlet axial current (FSAC), often referred to as proton spin, in terms of the chiral bag model with due account of the axial anomaly and quantum number fractionation. We conclude that the contribution due to gluons is significant for large bag radii and that it is crucial in order to establish the Cheshire cat principle.
Measurements of Double-Polarized Compton Scattering Asymmetries and Extraction of the Proton Spin Polarizabilities
2015
The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to measure the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the $\Delta(1232)$ region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a…
Measurement Of The Proton Spin Polarisabilities
2013
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 gluon spin in the chiral bag model
2000
We study the gluon polarization contribution at the quark model renormalization scale to the proton spin, $\Gamma$, in the chiral bag model. It is evaluated by taking the expectation value of the forward matrix element of a local gluon operator in the axial gauge $A^+=0$. It is shown that the confining boundary condition for the color electric field plays an important role. When a solution satisfying the boundary condition for the color electric field, which is not the conventionally used but which we favor, is used, the $\Gamma$ has a positive value for {\it all} bag radii and its magnitude is comparable to the quark spin polarization. This results in a significant reduction in the relativ…
Final COMPASS results on the deuteron spin-dependent structure functiong1dand the Bjorken sum rule
2017
Final results are presented from the inclusive measurement of deep-inelastic polarised-muon scattering on longitudinally polarised deuterons using a 6 LiD target. The data were taken at 160 GeV beam energy and the results are shown for the kinematic range 1(GeV/c)2 4GeV/c2 in the mass of the hadronic final state. The deuteron double-spin asymmetry A1d and the deuteron longitudinal-spin structure function g1d are presented in bins of x and Q2 . Towards lowest accessible values of x , g1d decreases and becomes consistent with zero within uncertainties. The presented final g1d values together with the recently published final g1p values of COMPASS are used to again evaluate the Bjorken sum rul…
Presencia de la langosta. Plagas en la Valencia bajomedieval
1997
La documentación municipal de Valencia es la base de este trabajo, en el que se precisa la cronología de las plagas de langosta que padecieron los campos del entorno de la ciudad en los siglos XIV y XV, y se analiza su incidencia en la vida urbana.
El impacto de la gran recesión en la Comunidad Valenciana
2013
La gran recesión ha tenido un impacto importante sobre la estructura de la pobreza y la privación en la población de la Comunidad Valenciana. Exceptuando el grupo de las personas de más edad, todos los demás se han visto afectados por esta crisis en mayor o menor medida. No solo ha crecido el porcentaje de familias que está por debajo del umbral de la pobreza o que están privadas de algunos bienes o servicios básicos, sino que también ha aumentado la intensidad de estos fenómenos pudiendo afirmarse que las personas pobres y privadas de bienes lo son ahora con mayor intensidad que antes de la crisis. El presente artículo expone de una manera resumida los principales datos del estudio realiza…
La escritura del shock. Crisis y poesía en España
2015
Resumen: El presente trabajo consiste en el analisis de la emergencia de nuevas subjetividades provocadas por el estado de shock neoliberal que ha tenido lugar en Espana y su cristalizacion en la escritura a traves de tres poemarios de autores jovenes. Partimos en primer lugar de la redefinicion del concepto de shock, describiendo por un lado el shock politico y, por otro, el shock estetico; a continuacion se lleva a cabo una explicacion del panorama poetico actual que engloba a los poetas jovenes aqui estudiados y las tendencias que comienzan a seguir y, finalmente, se lleva a cabo un analisis detallado de los tres libros para constatar dicha emergencia de nuevas subjetividades provocadas …