26 research outputs found
Supersymmetric Sum Rules for Electromagnetic Multipoles
We derive model independent, non-perturbative supersymmetric sum rules for
the magnetic and electric multipole moments of any theory with N=1
supersymmetry. We find that in any irreducible N=1 supermultiplet the diagonal
matrix elements of the l-multipole moments are completely fixed in terms of
their off-diagonal matrix elements and the diagonal (l-1)-multipole moments.Comment: 10 pages, plain Te
Effects of physics beyond the standard model on the neutrino charge radius: an effective Lagrangian approach
In this work, we look for possible new physics effects on the electromagnetic
charge and anapole form factors, and , for a massless
Dirac neutrino, when these quantities are calculated in the context of an
effective electroweak Yang-Mills theory, which induces the most general
--invariant Lorentz tensor structure of nonrenormalizable type for the
vertex. It is found that in this context, besides the standard model
contribution, the additional contribution to and
( and , respectively) are gauge independent
and finite functions of after adopting a renormalization scheme. These
form factors, and , get contribution at
the one loop level only from the proper neutrino electromagnetic vertex.
Besides, the relation
(,
) is still fulfilled and
hence the relation (, )is gotten, just as in the SM. Using the experimental
constraint on the anomalous vertex, a value for the additional
contribution to the charge radius of |^{O_W}| \lsim 10^{-34}
cm^2 is obtained, which is one order of magnitude lower than the SM value.Comment: 9 pages, 3 figure
Production of Three Vector Bosons in e+e- Annihilation as a Test of W+-, Z, gamma Self-Interactions
We study the vector-boson production processes e+e- --> WWZ and e+e-
-->WWgamma which are directly affected by the trilinear and quadrilinear self
couplings of the W, Z and gamma. Our analysis is based upon a single-parameter
effective-Lagrangian model for these self interactions which contains the
standard model as a special case. Consequences for the phenomenology at an e+e-
collider of 500 GeV (NLC) are discussed, and fits of the free parameter around
its standard model value are carried out.Comment: BI-TP 92/30, July 1992 (Enlarged Version October 1992) One section
added to the old version. Figures (unchanged) no more included but available
by reques
Uses and Abuses of Effective Lagrangians
Motivated by past and recent analyses we critically re-examine the use of
effective lagrangians in the literature to constrain new physics and to
determine the `physics reach' of future experiments. We demonstrate that many
calculations, such as those involving anomalous trilinear gauge-boson
couplings, either considerably overestimate loop-induced effects, or give
ambiguous answers. The source of these problems is the use of cutoffs to
evaluate the size of such operators in loop diagrams. In contrast to other
critics of these loop estimates, we prove that the inclusion of
nonlinearly-realized gauge invariance into the low-energy lagrangian is
irrelevant to this conclusion. We use an explicit example using known
multi-Higgs physics above the weak scale to underline these points. We show how
to draw conclusions regarding the nature of the unknown high-energy physics
without making reference to low-energy cutoffs.Comment: 36 page
Extracting W Boson Couplings from the Production of Four Leptons
We consider the processes , including all possible charged lepton combinations, with
regard to measuring parameters characterizing the boson. We calculate at
what level these processes can be used to measure anamolous triple-boson
vertice coupling parameters for the cases of colliders at 500
and 1 center of mass energies.Comment: 13 pages,OCIP/C-93-
Nuclear Shadowing in a Parton Recombination Model
Deep inelastic structure functions are investigated in a
rescaling model with parton recombination effects. We find that the model can
explain experimentally measured structure functions reasonably well
in the wide Bjorken range (). In the very small region
(), recombination results are very sensitive to input sea-quark and
gluon distributions.Comment: preprint MKPH-T-93-04, IU/NTC 92-20, 25 pages, TEX file (without
Figs. 1-14)., (address after April 1: Saga U., Japan
High-Energy Vector-Boson Scattering with Non-Standard Interactions and the Role of a Scalar Sector
The high-energy behavior of vector-boson scattering amplitudes is examined
within an effective theory for non-standard self-interactions of electroweak
vector-bosons. Irrespectively of whether this theory is brought into a gauge
invariant form by including non-standard interactions of a Higgs particle I
find that terms that grow particularly strongly with increasing scattering
energy are absent. Different theories are compared concerning their high-energy
behavior and the appearance of divergences at the one-loop level.Comment: 21 pages LaTeX, condensed version of BI-TP 93/5
Nuclear shadowing at low Q^2
We re-examine the role of vector meson dominance in nuclear shadowing at low
Q^2. We find that models which incorporate both vector meson and partonic
mechanisms are consistent with both the magnitude and the Q^2 slope of the
shadowing data.Comment: 7 pages, 2 figures; to appear in Phys. Rev.
Shadowing, Binding and Off-Shell Effects in Nuclear Deep Inelastic Scattering
We present a unified description of nuclear deep inelastic scattering (DIS)
over the whole region of the Bjorken variable. Our approach is based on
a relativistically covariant formalism which uses analytical properties of
quark correlators. In the laboratory frame it naturally incorporates two
mechanisms of DIS: (I) scattering from quarks and antiquarks in the target and
(II) production of quark-antiquark pairs followed by interactions with the
target. We first calculate structure functions of the free nucleon and develop
a model for the quark spectral functions. We show that mechanism (II) is
responsible for the sea quark content of the nucleon while mechanism (I)
governs the valence part of the nucleon structure functions. We find that the
coherent interaction of pairs with nucleons in the nucleus leads to
shadowing at small and discuss this effect in detail. In the large
region DIS takes place mainly on a single nucleon. There we focus on the
derivation of the convolution model. We point out that the off-shell properties
of the bound nucleon structure function give rise to sizable nuclear effects.Comment: 29 pages (and 10 figures available as hard copies from Authors),
REVTE
Role of beam polarization in the determination of and couplings from
We evaluate the constraints on anomalous trilinear gauge-boson couplings that
can be obtained from the study of electron-positron annihilation into pairs
at a facility with either the electron beam longitudinally polarized or both
electron and positron beams transversely polarized. The energy ranges
considered in the analysis are the ones relevant to the next-linear collider
and to LEP~200. We discuss the possibilities of a model independent analysis of
the general conserving anomalous effective Lagrangian, as well as its
restriction to some specific models with reduced number of independent
couplings. The combination of observables with initial and final state
polarizations allows to separately constrain the different couplings and to
improve the corresponding numerical bounds.Comment: 24 pages, LaTeX, 9 figures (available on request from the authors