Precision measurements of A1N in the deep inelastic regime

We have performed precision measurements of the double-spin virtual-photon asymmetry A1A1 on the neutron in the deep inelastic scattering regime, using an open-geometry, large-acceptance spectrometer and a longitudinally and transversely polarized 3He target. Our data cover a wide kinematic range 0.277≤x≤0.5480.277≤x≤0.548 at an average Q2Q2 value of 3.078 (GeV/c)2, doubling the available high-precision neutron data in this x range. We have combined our results with world data on proton targets to make a leading-order extraction of the ratio of polarized-to-unpolarized parton distribution functions for up quarks and for down quarks in the same kinematic range. Our data are consistent with a previous observation of anA1n zero crossing near x=0.5x=0.5. We find no evidence of a transition to a positive slope in(Δd+Δd¯)/(d+d¯) up to x=0.548x=0.548

Phenomenology of the deuteron electromagnetic form factors

A rigorous extraction of the deuteron charge form factors from tensor polarization data in elastic electron-deuteron scattering, at given values of the 4-momentum transfer, is presented. Then the world data for elastic electron-deuteron scattering is used to parameterize, in three different ways, the three electromagnetic form factors of the deuteron in the 4-momentum transfer range 0-7 fm. This procedure is made possible with the advent of recent polarization measurements. The parameterizations allow a phenomenological characterization of the deuteron electromagnetic structure. They can be used to remove ambiguities in the form factors extraction from future polarization data

UNA CORTA HISTORIA DE FACTORES g: “CASI” 100 AÑOS DE FACTORES g

El estudio de las propiedades electromagnéticas del núcleo ha sido fundamental en la investigación de la estructura nuclear. En particular, la magnitud y el signo del momento magnético inducen una medida directa de la configuración de los nucleones dentro del núcleo. Este trabajo se focaliza en la medida de los momentos magnéticos de núcleos con tiempos de vida media alrededor de los pico segundos. Muchas técnicas han sido desarrolladas, sacando provecho de la interacción entre los momentos magnéticos y los intensos campos magnéticos hiperfinos generados por el entorno electrónico. Se sugiere leer este artículo, en el que se delinean los principales elementos de estas investigaciones y se subrayan ejemplos relevantes, apoyado en la referencia[1], en donde se detalla la instrumentación, las reacciones relevantes y el análisis de los resultados.Ever since the discovery of the electron spin and the firm establishment of nuclear physics the study of electromagnetic properties of nuclei has been an important part of nuclear structure research. In particular, the magnitude and sign of the magnetic moment yield a direct measure of the configuration of the nucleons in the nucleus. This presentation is focused on the measurement of magnetic moments of short-lived nuclei with mean lifetimes of fractions to tenths of picoseconds. Many techniques have been developed which make use of the interactions between the nuclear moments and the very high hyperfine magnetic fields generated by the electronic environment. The main elements of the investigations are outlined and a few examples are highlighted. This paper should be read together with the presentation of an in-depth complementary description of relevant reactions, instrumentation, and analysis in Ref. [1]

Measurement of the generalized spin polarizabilities of the neutron in the low-Q2Q^2 region

International audienceUnderstanding the nucleon spin structure in the regime where the strong interaction becomes truly strong poses a challenge to both experiment and theory. At energy scales below the nucleon mass of about 1 GeV, the intense interaction among the quarks and gluons inside the nucleon makes them highly correlated. Their coherent behaviour causes the emergence of effective degrees of freedom, requiring the application of non-perturbative techniques such as chiral effective field theory1. Here we present measurements of the neutron’s generalized spin polarizabilities that quantify the neutron’s spin precession under electromagnetic fields at very low energy-momentum transfer squared down to 0.035 GeV2. In this regime, chiral effective field theory calculations2,3,4 are expected to be applicable. Our data, however, show a strong discrepancy with these predictions, presenting a challenge to the current description of the neutron’s spin properties