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

Tau Polarization in Λb→Xcτνˉ \Lambda_b \to X_c \tau \bar{\nu} and B→XcτνˉB \to X_c \tau \bar{\nu}

We discuss the longitudinal and transverse $\tau$-polarization in inclusive decays of hadrons containing $b$-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 $e^+ e^- \to e^+ e^- \tau^+ \tau^-$ at LEP is large enough to allow for a study of the anomalous electromagnetic couplings of the $\tau$ 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

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

Origem, disseminação, morfologia e fenologia.

Origem e disseminação; Morfologia: Semente, Talo e coroa, Folha, Flor, Desenvolvimento floral e polinização, Fruto; Fenologi

Variabilidade da temperatura no microambiente próximo as plantas de Paspalum pumilum.

O objetivo deste trabalho foi avaliar a variabilidade da temperatura do ambiente em diferentes níveis de altura próximo às plantas de Paspalum pumilum.Claudia Cristina Gulias Gomes, editora técnica

Influência de métodos de superação de dormência na germinação de sementes de Paspalum regnellii Mez.

Este trabalho teve por objetivo verificar a influencia de métodos de superação de dormência na porcentagem de germinação de sementes de Paspalum regnellii Mez.SEPE

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 $Z$ peak. Proportionality of the Yukawa couplings to the fermion masses, and to $\tan{\beta}$, makes such effects more important for the third family, and potentially relevant. For the $\tau$ lepton, the new diagrams are suppressed by $v_\tau = 2 \sin^2 \theta_W - 1/2$, or by powers of $m_\tau/M_Z$, 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 $\tan \beta$ is large. We also comment on the problem of the gauge dependence of the vertex, arising when the $Z$ 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 $\tau$ production at LEP2. In the case of the top, we find that the SM electroweak and gluonic contributions to the $Z t {\bar t}$ 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

Superação de dormência em sementes de Paspalum dilatatum Poir biótipo virasoro pelo uso de ácido sulfúrico.

Esse trabalho tem por objetivo avaliar a superação de dormência pela escarificação química utilizando ácido sulfúrico em diferentes tempos de exposição.Claudia Cristina Gulias Gomes, editora técnica