The Solar pp and hep Processes in Effective Field Theory

The strategy of modern effective field theory is exploited to pin down accurately the flux $S$ factors for the $pp$ and $hep$ processes in the Sun. The technique used is to combine the high accuracy established in few-nucleon systems of the "standard nuclear physics approach" (SNPA) and the systematic power counting of chiral perturbation theory (ChPT) into a consistent effective field theory framework. Using highly accurate wave functions obtained in the SNPA and working to \nlo3 in the chiral counting for the current, we make totally parameter-free and error-controlled predictions for the $pp$ and $hep$ processes in the Sun.Comment: 5 pages, aipproc macros are included. Talk given at International Nuclear Physics Conference 2001, Berkeley, California, July 30 - August 3, 200

The Gluon Spin in the Chiral Bag Model

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 relative fraction of the proton spin carried by the quark spin, which is consistent with the small flavor singlet axial current measured in the EMC experiments.Comment: Corrections to figure

Top quark forward-backward asymmetry and charge asymmetry in left-right twin Higgs model

In order to explain the Tevatron anomaly of the top quark forward-backward asymmetry $A_{FB}^t$ in the left-right twin Higgs model, we choose to give up the lightest neutral particle of $\hat{h}$ field as a stable dark matter candidate. Then a new Yukawa interaction for $\hat{h}$ is allowed, which can be free from the constraint of same-sign top pair production and contribute sizably to $A_{FB}^t$. Considering the constraints from the production rates of the top pair ($t\bar t$), the top decay rates and $t\bar{t}$ invariant mass distribution, we find that this model with such new Yukawa interaction can explain $A_{FB}^t$ measured at the Tevatron while satisfying the charge asymmetry $A_{C}^t$ measured at the LHC.Moreover, this model predicts a strongly correlation between $A_{C}^t$ at the LHC and $A_{FB}^t$ at the Tevatron, i.e., $A_{C}^t$ increases as $A_{FB}^t$ increases.Comment: 17 pages, 9 figures; matches the published versio

An Universal Quantum Network - Quantum CPU

An universal quantum network which can implement a general quantum computing is proposed. In this sense, it can be called the quantum central processing unit (QCPU). For a given quantum computing, its realization of QCPU is just its quantum network. QCPU is standard and easy-assemble because it only has two kinds of basic elements and two auxiliary elements. QCPU and its realizations are scalable, that is, they can be connected together, and so they can construct the whole quantum network to implement the general quantum algorithm and quantum simulating procedure.Comment: 8 pages, Revised versio

Higher Derivative Operators as Counterterms in Orbifold Compactifications

In the context of 5D N=1 supersymmetric models compactified on S_1/Z_2 or S_1/(Z_2 x Z_2') orbifolds and with brane-localised superpotential, higher derivative operators are generated radiatively as one-loop counterterms to the mass of the (brane or zero mode of the bulk) scalar field. It is shown that the presence of such operators which are brane-localised is not related to the mechanism of supersymmetry breaking considered (F-term, discrete or continuous Scherk-Schwarz breaking) and initial supersymmetry does not protect against the dynamical generation of such operators. Since in many realistic models the scalar field is commonly regarded as the Higgs field, and the higher derivative operators seem a generic presence in orbifold compactifications, we stress the importance of these operators for solving the hierarchy problem.Comment: Contribution to the Conference "Supersymmetry 2005", Durham; 13 pages, LaTe

The classical dynamics of two-electron atoms near the triple collision

The classical dynamics of two electrons in the Coulomb potential of an attractive nucleus is chaotic in large parts of the high-dimensional phase space. Quantum spectra of two-electron atoms, however, exhibit structures which clearly hint at the existence of approximate symmetries in this system. In a recent paper,(Phys. Rev. Lett. 93, 054302 (2004)), we presented a study of the dynamics near the triple collision as a first step towards uncovering the hidden regularity in the classical dynamics of two electron atoms. The non-regularisable triple collision singularity is a main source of chaos in three body Coulomb problems. Here, we will give a more detailed account of our findings based on a study of the global structure of the stable and unstable manifolds of the triple collision.Comment: 21 pages, 17 figure

Chiral Dynamics and Heavy-Fermion Formalism in Nuclei: Exchange Axial Currents

URL: http://www-spht.cea.fr/articles/T93/013 http://fr.arxiv.org/abs/hep-ph/9301295International audienceChiral perturbation theory in heavy-fermion formalism is developed for meson-exchange currents in nuclei and applied to nuclear axial-charge transitions. Calculation is performed to the next-to-leading order in chiral expansion which involves graphs up to one loop. The result turns out to be very simple. The previously conjectured notion of \lq\lq chiral filter mechanism\rq\rq\ in the time component of the nuclear axial current on the space component of the nuclear electromagnetic current is verified to that order. As a consequence, the phenomenologically observed soft-pion dominance in the nuclear process is given a simple interpretation in terms of chiral symmetry in nuclei. In this paper we focus on the axial current, relegating the electromagnetic current which can be treated in a similar way to a separate paper. We discuss the implication of our result on the enhanced axial-charge transitions observed in heavy nuclei and clarify the relationship between the phenomenological meson-exchange description and the chiral Lagrangian description.Lorqu'on cherche à appliquer la théorie des perturbations chirales à des processus où entrent en jeu les nucléons et les mésons, on se heurte à une difficulté liée à la masse du nucléon qui est grande par rapport aux petits paramètres de la théorie (impulsions externes, masse du pion, constante de désintégration du pion). Dans ce travail les auteurs appliquent le formalisme des baryons lourds pour lever cette difficulté. Grossièrement parlant ce formalisme travaille avec des champs des nucléons redéfinis de manière à éliminer les effets de la masse du nucléon. Cela permet aux auteurs d'identifier l'ordre en nombre de boucles à l'ordre de la perturbation chirale. Les calculs deviennent plus rigoureux et en sont grandement simplifiés. Les auteurs appliquent leur méthode au calcul, jusqu'au deuxième ordre, de l'interaction du courant électrofaible avec les noyaux