30,317 research outputs found
Bound state of dimers on a spherical surface
The study of particle motion on spherical surfaces is relevant to adsorption
on buckyballs and other solid particles. This paper reports results for the
binding energy of such dimers, consisting of two light particles (He atoms or
hydrogen molecules) constrained to move on a spherical surface. The binding
energy reaches a particularly large value when the radius of the sphere is
about 3/4 of the particles' diameter.Comment: 6 pages, 3 figures, submitted to JLTP, conference proceedings QFS
200
Large gauge invariant non-standard neutrino interactions
Theories beyond the Standard Model must necessarily respect its gauge
symmetry. This implies strict constraints on the possible models of
non-standard neutrino interactions, which we analyze. The focus is set on the
effective low-energy dimension six and eight operators involving four leptons,
decomposing them according to all possible tree-level mediators, as a guide for
model building. The new couplings are required to have sizeable strength, while
processes involving four charged leptons are required to be suppressed. For
non-standard interactions in matter, only diagonal tau-neutrino interactions
can escape these requirements and can be allowed to result from dimension six
operators. Large non-standard neutrino interactions from dimension eight
operators alone are phenomenologically allowed in all flavour channels and
shown to require at least two new mediator particles. The new couplings must
obey general cancellation conditions both at the dimension six and eight
levels, which result from expressing the operators obtained from the mediator
analysis in terms of a complete basis of operators. We illustrate with one
example how to apply this information to model building.Comment: 34 pages, 4 figures, 5 tables. Final version in PR
Finite-Size Scaling of Vector and Axial Current Correlators
Using quenched chiral perturbation theory, we compute the long-distance
behaviour of two-point functions of flavour non-singlet axial and vector
currents in a finite volume, for small quark masses, and at a fixed gauge-field
topology. We also present the corresponding predictions for the unquenched
theory at fixed topology. These results can in principle be used to measure the
low-energy constants of the chiral Lagrangian, from lattice simulations in
volumes much smaller than one pion Compton wavelength. We show that quenching
has a dramatic effect on the vector correlator, which is argued to vanish to
all orders, while the axial correlator appears to be a robust observable only
moderately sensitive to quenching.Comment: version to appear in NP
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First CRDS-measurements of water vapour continuum in the 940nm absorption band
Measurements of near-infrared water vapour continuum using continuous wave cavity ring down spectroscopy (cw-
CRDS) have been performed at around 10611.6 and 10685:2 cm1. The continuum absorption coefficients for N2-
broadening have been determined for two temperatures and wavenumbers.
These results represent the first near-IR continuum laboratory data determined within the complex spectral environment in the 940nm water vapour band and are in reasonable agreement with simulations using the semiempirical CKD formulation
Production of Two Pions Induced by Neutrinos
We study the threshold production of two pions induced by neutrinos in
nucleon targets. The contribution of nucleon pole, pion and contact terms is
calculated using a chiral Lagrangian. The contribution of the Roper resonance,
neglected in earlier studies, has also been taken into account.Comment: Contribution to the proceedings of Chiral07, RCNP, Osaka, Japan.
Corrected version because of problems on some pdf viewer
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