175 research outputs found
Role of Quark-Interchange in NN → NNpi Reactions
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
Neutrino mass induced radiatively by supersymmetric leptoquarks
We show how nonzero Majorana neutrino masses can be radiatively generated by
extending the MSSM with leptoquark chiral multiplets without violating
R-parity. It is found that, with these particles, the R-parity conservation
does not imply lepton number conservation. Neutrino masses generated at a
one-loop level are closely related to the down quark mass matrix. The ratio of
neutrino mass-squared splittings obtained is naturally close to which is in the right region required to explain both
the atmospheric neutrino data and the MSW solutions for the solar neutrino
data.Comment: 13 pages, one figure, more constraints added. To appear in Phys.
Lett.
Can the quintessence be a complex scalar field?
In light of the recent observations of type Ia supernovae suggesting an
accelerating expansion of the Universe, we wish in this paper to point out the
possibility of using a complex scalar field as the quintessence to account for
the acceleration. In particular, we extend the idea of Huterer and Turner in
deriving the reconstruction equations for the complex quintessence, showing the
feasibility of making use of a complex scalar field (instead of a real scalar
field) while maintaining the uniqueness feature of the reconstruction for two
possible situations, respectively. We discuss very briefly how future
observations may help to distinguish the different quintessence scenarios,
including the scenario with a positive cosmological constant.Comment: 9 pages, LaTeX, final versio
Hadronic Parity Violation and Inelastic Electron-Deuteron Scattering
We compute contributions to the parity-violating (PV) inelastic
electron-deuteron scattering asymmetry arising from hadronic PV. While hadronic
PV effects can be relatively important in PV threshold electro- disintegration,
we find that they are highly suppressed at quasielastic kinematics. The
interpretation of the PV quasielastic asymmetry is, thus, largely unaffected by
hadronic PV.Comment: 27 pages, 13 figures, uses REVTeX and BibTe
Nonleptonic Hyperon Decays with QCD Sum Rules
Despite measurements which date more than 20 years ago, no straightforward
solution of the ratio of the parity-conserving (P-wave) to parity- violating
(S-wave) decays of the hyperons has been obtained. Here we use two 2-point
methods in QCD sum rules to examine the problem. We find that resonance
contributions are needed to fit the data, similar to a chiral perturbation
theory treatment.Comment: 17 pages, 8 figure
The Weak Parity-Violating Pion-Nucleon Coupling (Revised)
We use QCD sum rules to obtain the weak parity-violating pion-nucleon
coupling constant . We find that , about an order of magnitude smaller than the ``best estimates'' based
on quark models. This result follows from the cancellation between perturbative
and nonperturbative QCD processes not found in quark models, but explicit in
the QCD sum rule method. Our result is consistent with the experimental upper
limit found from F parity-violating measurements.Comment: 13 pages, uses LaTex; figures can be obtained from any of the
authors: [email protected], Kisslinger@kelvin. phys.cmu.edu,
[email protected]
coupling constant
We calculate the coupling
using light cone QCD sum rule. Our result is
.Comment: RevTex, 5 pages + 1 PS figur
Vertex functions for d-wave mesons in the light-front approach
While the light-front quark model (LFQM) is employed to calculate hadronic
transition matrix elements, the vertex functions must be pre-determined. In
this work we derive the vertex functions for all d-wave states in this model.
Especially, since both of and are mesons, the Lorentz
structures of their vertex functions are the same. Thus when one needs to study
the processes where is involved, all the corresponding formulas for
states can be directly applied, only the coefficient of the vertex
function should be replaced by that for . The results would be useful
for studying the newly observed resonances which are supposed to be d-wave
mesons and furthermore the possible 2S-1D mixing in with the LFQM.Comment: 12 pages, 2 figures, some typos corrected and more discussions added.
Accepted by EPJ
Deuteron Electroweak Disintegration
We study the deuteron electrodisintegration with inclusion of the neutral
currents focusing on the helicity asymmetry of the exclusive cross section in
coplanar geometry. We stress that a measurement of this asymmetry in the quasi
elastic region is of interest for an experimental determination of the weak
form factors of the nucleon, allowing one to obtain the parity violating
electron neutron asymmetry. Numerically, we consider the reaction at low
momentum transfer and discuss the sensitivity of the helicity asymmetry to the
strangeness radius and magnetic moment. The problems coming from the finite
angular acceptance of the spectrometers are also considered.Comment: 30 pages, Latex, 7 eps figures, submitted to Phys.Rev.C e-mail:
[email protected] , [email protected]
Pion Content of the Nucleon as seen in the NA51 Drell-Yan experiment
In a recent CERN Drell-Yan experiment the NA51 group found a strong asymmetry
of and densities in the proton at . We interpret
this result as a decisive confirmation of the pion-induced sea in the nucleon.Comment: 10 pages + 3 figures, Preprint KFA-IKP(TH)-1994-14 .tex file. After
\enddocument a uu-encodeded Postscript file comprising the figures is
appende
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