107 research outputs found
Tensor charge and anomalous magnetic moment correlation
We propose a generalization of the upgraded Karl- Sehgal formula which
relates baryon magnetic moments to the spin structure of constituent quarks, by
adding anomalous magnetic moments of quarks. We first argue that relativistic
nature of quarks inside baryons requires introduction of two kinds of
magnetisms, one axial and the other tensoriel. The first one is associated with
integrated quark helicity distributions (standard) and the second with
integrated transversity distributions . The weight of each contribution is
controlled by the combination of two parameters, xi the ratio of the quark mass
to the average kinetic energy Ei and ai the quark anomalous magnetic moment.
The quark anomalous magnetic moment is correlated to transversity and both are
necessary ingredients in describing relativistic quarks. The proposed formula,
then when confronted with baryon magnetic moments data with reasonable inputs,
yields beside quark magnetic densities, anomalous magnetic moments enough large
to not be ignored.Comment: 26 pages, PDF format onl
Search for TeV Strings and New Phenomena in Bhabha Scattering at LEP2
A combined analysis of the data on Bhabha scattering at centre-of-mass
energies 183 and 189 GeV from the LEP experiments ALEPH, L3 and OPAL is
performed to search for effects of TeV strings in quantum gravity models with
large extra dimensions. No statistically significant deviations from the
Standard Model expectations are observed and lower limit on the string scale
M_S = 0.631 TeV at 95 % confidence level is derived. The data are used to set
lower limits on the scale of contact interactions ranging from 4.2 to 16.2 TeV
depending on the model. In a complementary analysis we derive an upper limit on
the electron size of 2.8 x 10^{-19} m at 95 % confidence level.Comment: 10 pages, 1 table, 3 figure
Tau Polarization in and
We discuss the longitudinal and transverse -polarization in inclusive
decays of hadrons containing -quarks. The calculation is performed by means
of an OPE in HQET. Some mathematical difficulties in calculating transverse
polarizations are explained. Numerical results are presented for longitudinal
and for transverse polarizations, both in and perpendicular to the decay plane.Comment: LATEX, 20 pages, 5 Postscript figure
TAU-PAIR PRODUCTION VIA PHOTON-PHOTON COLLISIONS AT LEP
We point out that the cross-section for the process at LEP is large enough to allow for a study of the anomalous
electromagnetic couplings of the lepton. We show that the present bounds
on the magnetic dipole moment can be improved and that competitive bounds can
be obtained for the electric dipole moment using the data taken from 1992 to
1994. Finally, we briefly discuss the improvements that can be obtained at LEP
II.Comment: 9 pages, latex, 2 figure
Weak magnetic dipole moments in two-Higgs-doublet models
We investigate the effects of the new scalars in a two-Higgs-doublet model on
the weak magnetic dipole moments of the fermions at the peak.
Proportionality of the Yukawa couplings to the fermion masses, and to
, makes such effects more important for the third family, and
potentially relevant. For the lepton, the new diagrams are suppressed by
, or by powers of , but may still
be comparable to the SM electroweak contributions. In contrast, we find that
the new contributions for the bottom quark may be much larger than the SM
electroweak contributions. These new effects may even compete with the gluonic
contribution, if the extra scalars are light and is large. We also
comment on the problem of the gauge dependence of the vertex, arising when the
is off mass shell. We compute the contributions from the new scalars to the
magnetic dipole moments for top-quark production at the NLC, and for bottom and
production at LEP2. In the case of the top, we find that the SM
electroweak and gluonic contributions to the vertex are
comparable. The new contributions may be of the same order of magnitude as the
standard-model ones, but not much larger.Comment: 17 pages, LaTex, 8 figures available upon reques
Avaliação de Panicum maximum em Bagé - RS.
Panicum maximum Jacq. Ă© uma espĂ©cie originĂĄria da Ăfrica, de alta qualidade forrageira, exigente em fertilidade do solo e adaptada a vĂĄrios tipos de clima e solos. No Brasil, desde meados da dĂ©cada de 1980, vem sendo conduzido o programa de melhoramento genĂ©tico desta forrageira pela Embrapa.Claudia Cristina Gulias Gomes, editora tĂ©cnica
Variabilidade da temperatura no microambiente prĂłximo as plantas de Paspalum pumilum.
O objetivo deste trabalho foi avaliar a variabilidade da temperatura do ambiente em diferentes nĂveis de altura prĂłximo Ă s plantas de Paspalum pumilum.Claudia Cristina Gulias Gomes, editora tĂ©cnica
Estabilidade de genĂłtipos elites de azevĂ©m na Campanha gaĂșcha.
O objetivo deste trabalho foi avaliar a estabilidade de 8 genótipos, sendo 6 cultivares durante dois anos consecutivos.Claudia Cristina Gulias Gomes, editora técnica
Can We Observe Weak Anomalous Couplings of Heavy Quarks Through Three Jet Events?
The rates and corresponding jet distributions for the decay
and the process may be sensitive to anomalous dipole-like
couplings of heavy quarks to the photon and . In the -quark case, after
updating our previous analysis on the constraints imposed by current
experiments on anomalous couplings, we show that the variation of
these couplings within their presently allowed ranges leads to rather minor
modifications to the Standard Model expectations for
observables. In the -quark case, significant deviations from the Standard
Model predictions for production at the Next Linear Collider are
possible.Comment: 26 pages with 9 embedded figures; gzipped, uuencoded postscript file.
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