29 research outputs found
Physics at the front-end of a neutrino factory: a quantitative appraisal
We present a quantitative appraisal of the physics potential for neutrino
experiments at the front-end of a muon storage ring. We estimate the forseeable
accuracy in the determination of several interesting observables, and explore
the consequences of these measurements. We discuss the extraction of individual
quark and antiquark densities from polarized and unpolarized deep-inelastic
scattering. In particular we study the implications for the undertanding of the
nucleon spin structure. We assess the determination of alpha_s from scaling
violation of structure functions, and from sum rules, and the determination of
sin^2(theta_W) from elastic nu-e and deep-inelastic nu-p scattering. We then
consider the production of charmed hadrons, and the measurement of their
absolute branching ratios. We study the polarization of Lambda baryons produced
in the current and target fragmentation regions. Finally, we discuss the
sensitivity to physics beyond the Standard Model.Comment: 73+1 pages, 33 figs. Report of the nuDIS Working Group for the
ECFA-CERN Neutrino-Factory study, M.L. Mangano (convener
Angular distributions in hard exclusive production of pion pairs
Using the leading order amplitudes of hard exclusive electroproduction of
pion pairs we have analyzed the angular distribution of the two produced
particles. At leading twist a pion pair can be produced only in an isovector or
an isoscalar state. We show that certain components of the angular distribution
only get contributions from the interference of the I=1 and the (much smaller)
I=0 amplitude. Therefore our predictions prove to be a good probe of isospin
zero pion pair production. We predict effects of a measurable size that could
be observed at experiments like HERMES. We also discuss how hard exclusive pion
pair production can provide us with new information on the effective chiral
Lagrangian.Comment: 17 pages, version to appear in Phys. Rev.
Current in the light-front Bethe-Salpeter formalism II: Applications
We pursue applications of the light-front reduction of current matrix
elements in the Bethe-Salpeter formalism. The normalization of the reduced wave
function is derived from the covariant framework and related to non-valence
probabilities using familiar Fock space projection operators. Using a simple
model, we obtain expressions for generalized parton distributions that are
continuous. The non-vanishing of these distributions at the crossover between
kinematic regimes (where the plus component of the struck quark's momentum is
equal to the plus component of the momentum transfer) is tied to higher Fock
components. Moreover continuity holds due to relations between Fock components
at vanishing plus momentum. Lastly we apply the light-front reduction to
time-like form factors and derive expressions for the generalized distribution
amplitudes in this model.Comment: 12 pages, 6 figures, RevTex