Search results for "RULE"
showing 10 items of 1403 documents
Pentaquark from QCD sum rules: consequences of the diquark approach
2006
In this work we investigate the consequences of the Jaffe and Wilczek diquark model in the framework of QCD sum rules. An analysis of the Theta^+(1540) as (ud)^2\bar{s} state shows that the mass of the pentaquark is compatible with the experimentally measured value. The mass difference between the Theta^+ and the pentaquark with the quantum numbers of the nucleon amounts to 70 MeV and is consistent with the interpretation of the N(1440) as a pentaquark.
Exploring the D* rho system within QCD sum rules
2013
We present a study of the D* rho system made by using the method of QCD sum rules to determine the mass of possible resonances generated in the same system. Using isospin and spin projectors, we investigate the different configurations and obtain evidences for three D* mesons with isospin I = 1/2, spin S = 0, 1, 2 and with masses 2500 +/- 67, 2523 +/- 60, and 2439 +/- 119 MeV, respectively. The last state can be associated with D-2*(2460) ( spin 2) listed by the Particle Data Group, while one of the first two might be related to D* (2640), with unknown spin parity. In the case of I = 3/2 we also find evidences of three states with spin 0, 1, and 2, respectively, with masses 2467 +/- 82, 242…
Radiative decay of the dynamically generated open and hidden charm scalar meson resonancesDs0*(2317)andX(3700)
2007
We present the formalism for the decay of dynamically generated scalar mesons with open- or hidden charm and give results for the decay of ${D}_{s0}^{*}(2317)$ to $\ensuremath{\gamma}{D}_{s}^{*}$ plus that of a hidden charm scalar meson state predicted by the theory around 3700 MeV decaying into $\ensuremath{\gamma}J/\ensuremath{\psi}$.
A new measurement of the spin-dependent structure function $g_{1}(x)$ of the deuteron
1995
Abstract We present a new measurement of the spin-dependent structure function g 1 d of the deuteron in deep inelastic scattering of 190 GeV polarised muons on polarised deuterons, in the kinematic range 0.003 x 2 Q 2 2 . This structure function is found to be negative at small x . The first moment Γ 1 d =∫ 0 1 g 1 d d x evaluated at Q 0 2 = 10 GeV 2 is 0.034 ± 0.009 (stat.) ± 0.006 (syst.). This value is below the Ellis-Jaffe sum rule prediction by three standard deviations. Using our earlier determination of Γ 1 p , we obtain Γ 1 p − Γ 1 n = 0.199 ± 0.038 which agrees with the Bjorken sum rule.
Nuclear effects in F_3 structure function of nucleon
2008
We study nuclear effects in the $F^A_3(x)$ structure function in the deep inelastic neutrino reactions on iron by using a relativistic framework to describe the nucleon spectral functions in the nucleus. The results for the ratio $R(x,Q^2)=\frac{F^A_3(x,Q^2)}{AF^N_3(x, Q^2)}$ and the Gross-Llewellyn Smith(GLS) integral $G(x,Q^2)=\int_x^1 dx F^A_3(x,Q^2)$ in nuclei are discussed and compared with the recent results available in literature from theoretical and phenomenological analyses of experimental data.
New neutrino mass sum rule from the inverse seesaw mechanism
2012
A class of discrete flavor-symmetry-based models predicts constrained neutrino mass matrix schemes that lead to specific neutrino mass sum rules. One of these implies a lower bound on the effective neutrinoless double beta mass parameter, even for normal hierarchy neutrinos. Here we propose a new model based on the ${S}_{4}$ flavor symmetry that leads to the new neutrino mass sum rule and discuss how to generate a nonzero value for the reactor angle ${\ensuremath{\theta}}_{13}$ indicated by recent experiments, and the resulting correlation with the solar angle ${\ensuremath{\theta}}_{12}$.
Nucleon Vector Strangeness Form Factors: Multi-pion Continuum and the OZI Rule
1997
We estimate the 3 \pi continuum contribution to the nucleon strange quark vector current form factors, including the effect of a 3 \pi \rho \pi resonance. We find the magnitude of this OZI-violating contribution to be comparable to that of typical OZI-allowed contributions. We also study the isoscalar electromagnetic form factors, and find that the presence of a \rho \pi resonance in the multi-pion continuum may generate an appreciable contribution.
Fermion masses and unitarity without a Higgs boson
2004
We discuss the consistency of fermion mass generation by boundary conditions and brane localized terms in higher dimensional models of gauge symmetry breaking without a Higgs boson. The sum rules imposed by tree-level unitarity and Ward identities are applied to check the consistency of mass generation by orbifold projections and more general boundary conditions consistent with the variational principle. We find that the sum rules are satisfied for boundary conditions corresponding to brane localized mass and kinetic terms consistent with the reduced gauge symmetry on the brane.
Low-energy Compton scattering and the polarizabilities of the proton
2001
Differential cross-sections for Compton scattering from the proton have been measured at the MAMI tagged photon facility using the TAPS setup. The data cover an angular range of θlab γ = 59°-155° and photon energies ranging from 55 MeV to 165 MeV. Our results are in good agreement with those from previous experiments, but yield higher precision. Using dispersion relations the proton polarizabilities have been determined to be = [11.9±0.5stat.±1.3syst.±0.3mod.] . 10-4 fm 3 and = [1.2±0.7stat.±0.3syst.±0.4mod.)] . 10-4 fm 3. These results confirm the Baldin sum rule which was re-evaluated to be + = [13.8±0.4] . 10-4 fm 3. We can also conclude that there is no significant additional asymptotic…
Study of polarization observables in double pion photoproduction on the proton
2001
Using a model for two pion photoproduction on the proton previously tested in total cross sections and invariant mass distributions, we evaluate here polarization observables on which recent experiments are providing new information. We evaluate cross sections for spin 1/2 and 3/2, which are measured at Mainz and play an important role in tests of the GHD sum rule. We also evaluate the proton polarization asymmetry $\Sigma$ which is currently under investigation at GRAAL in Grenoble.