Fermi matrix element with isospin breaking

Prompted by the level of accuracy now being achieved in tests of the unitarity of the CKM matrix, we consider the possible modification of the Fermi matrix element for the $\beta$-decay of a neutron, including possible in-medium and isospin violating corrections. While the nuclear modifications lead to very small corrections once the Behrends-Sirlin-Ademollo-Gatto theorem is respected, the effect of the $u-d$ mass difference on the conclusion concerning $V_{ud}$ is no longer insignificant. Indeed, we suggest that the correction to the value of $|V_{ud}|^2 \, + \, |V_{us}|^2 \, + \, |V_{ub}|^2$ is at the level of $10^{-4}$

Constraints on nuclear matter properties from QCD susceptibilities

We establish the interrelation between the QCD scalar response of the nuclear medium and its response to a scalar probe coupled to nucleons, such as the scalar meson responsible for the nuclear binding. The relation that we derive applies at the nucleonic as well as at the nuclear levels. Non trivial consequences follow. In particular it opens the possibility of relating medium effects in the scalar meson exchange or three-body forces of nuclear physics to QCD lattice studies of the nucleon massComment: Submitted to EPJ

Progress in Understanding the Nuclear Equation of State at the Quark Level

At the present time there is a lively debate within the nuclear community concerning the relevance of quark degrees of freedom in understanding nuclear structure. We outline the key issues and review the impressive progress made recently within the framework of the quark-meson coupling model. In particular, we explain in quite general terms how the modification of the internal structure of hadrons in-medium leads naturally to three- and four-body forces, or equivalently, to density dependent effective interactions.Comment: Invited presentation at XXX Symposium on Nuclear Physics, Hacienda Cocoyoc, Jan. 3-6, 200

Deeply virtual electroproduction of photons and mesons on the nucleon

We give predictions for the leading order amplitudes for deeply virtual Compton scattering and hard meson electroproduction reactions at large Q^2 in the valence region in terms of skewed quark distributions. We give first estimates for the power corrections to these leading order amplitudes. In particular, we outline examples of experimental opportunities to access the skewed parton distributions at the current high-energy lepton facilities : JLab, HERMES and COMPASS.Comment: 4 pages, 4 figures. Invited talk at XVth Particles and Nuclei International Conference (PANIC 99), Uppsala, Sweden, 10-16 June 1999. To be published by World Scientific (Singapore

Hypernuclei in the quark-meson coupling model

We present results of hypernuclei calculated in the latest quark-meson coupling (QMC) model, where the effect of the mean scalar field in-medium on the one-gluon exchange hyperfine interaction, is also included self-consistently. The extra repulsion associated with this increased hyperfine interaction in-medium completely changes the predictions for {\Sigma} hypernuclei. Whereas in the earlier version of QMC they were bound by an amount similar to {\Lambda} hypernuclei, they are unbound in the latest version of QMC, in qualitative agreement with the experimental absence of such states.Comment: 6 pages, 3 figures, to be published in the proceedings of Achievements and New Directions in Subatomic Physics: Workshop in Honour of Tony Thomas' 60th Birthday, Adelaide, South Australia, 15-19 Feb 201

Quark structure and nuclear effective forces

We formulate the quark meson coupling model as a many-body effective Hamiltonian. This leads naturally to the appearance of many-body forces. We investigate the zero range limit of the model and compare its Hartree-Fock Hamiltonian to that corresponding to the Skyrme effective force. By fixing the three parameters of the model to reproduce the binding and symmetry energy of nuclear matter, we find that it allows a very satisfactory interpretation of the Skyrme force.Comment: 4 pages, 1tabl

EMC and Polarized EMC Effects in Nuclei

We determine nuclear structure functions and quark distributions for $^7$Li, $^{11}$B, $^{15}$N and $^{27}$Al. For the nucleon bound state we solve the covariant quark-diquark equations in a confining Nambu--Jona-Lasinio model, which yields excellent results for the free nucleon structure functions. The nucleus is described using a relativistic shell model, including mean scalar and vector fields that couple to the quarks in the nucleon. The nuclear structure functions are then obtained as a convolution of the structure function of the bound nucleon with the light-cone nucleon distributions. We find that we are readily able to reproduce the EMC effect in finite nuclei and confirm earlier nuclear matter studies that found a large polarized EMC effect.Comment: 8 pages, 9 figure

Recherche-développement et didactique des langues

National audienceThis article aims at analysing the potential of contextualised research-development for research in applied linguistics. Starting from the meaning this methodology has for the industrial sector in which it originated, our purpose will be firstly to propose a definition for contextualised research-development, and secondly to describe its particular mode of production of knowledge so as to highlight its key elements and its limits for research on foreign language learning through multimedia.Cet article vise à analyser le potentiel de la recherche-développement pour la recherche en didactique des langues. En partant de son acception pour le secteur industriel dont cette démarche est issue, il s'agira de définir ce que pourrait être une recherche-développement contextualisée, de décrire son mode particulier de production des connaissances afin d'en souligner les éléments essentiels et les limites pour la recherche sur l'apprentissage médiatisé des langues étrangères

Training future language teachers to develop online tutors' competence through reflective analysis

International audienceThis article sets out to identify key competencies which language tutors need to develop in order to manage synchronous online teaching. In order to aptly monitor interactions with distant learners, it is proposed that three types of regulation pertaining to socio-affective, pedagogical and multimedia aspects are required. On the one hand, this research aims at specifying these competencies and, on the other hand, it seeks to identify the relevance of reflective analysis for professional development. The context of this study is a teacher training programme for Masters Degree students in teaching French as a foreign language that provides trainees with the opportunity of teaching online to intermediate-level students of French from a North American university via a desktop videoconferencing platform. This programme first endeavours to put trainees in a professional situation by getting them to prepare and administer sessions in order to confront them with the specific challenges of synchronous online tutoring. Second, it seeks to help them to gain insight into their own activity by developing critical thinking towards their own practice. The data elicited for this research derive from the tutor trainees' interpretations of their own practice when confronted with the film of their own situated activity. The episodes chosen by the trainees to feed the self-confrontation process constitute significant units because by being told and commented upon, they elucidate how and to what extent competencies are built. Three discursive strategies have been identified and used to organise the content analysis of the data: description; expression of a difficulty; reflective review of the activity. The strategies used by trainees to verbalise their own activity can inform teacher educators about the constraints of the work situation and about the resources trainees need to deploy to face up to this unknown professional situation. Results indicate that trainees concentrate particularly on pedagogical aspects that distance and faulty technology have rendered complex. The encountered difficulties are equally distributed between a repertoire of competencies pertaining to language teaching and competencies more directly linked with online teaching. Finally, this study has enabled us to assess the potential of self-confrontation for teacher practice and leads us to propose directions for improving this training device

Quark Distributions in a Medium

We derive the formal expressions needed to discuss the change of the twist-two parton distribution functions when a hadron is placed in a medium with relativistic scalar and vector mean fieldsComment: 6 page