6,813 research outputs found
Electromagnetic Form Factors and the Hypercentral CQM
New results about the electromagnetic form factors of the nucleon are
obtained with a semirelativistic version of the hypercentral constituent quark
model (hCQM) and a relativistic current. The complex structure of the
constituent quarks is taken into account implicitly by means of
phenomenological constituent quark form factors. We obtain a detailed
reproduction of the experimental data up to , moreover our findings
about constituent quark root mean square radii are of the same order than the
recent ones obtained analyzing the proton structure functions.Comment: 11 pages, 4 figure
A relativistic study of the nucleon form factors
We perform a calculation of the relativistic corrections to the
electromagnetic elastic form factors of the nucleon obtained with various
Constituent Quark Models. With respect to the non relativistic calculations a
substantial improvement is obtained up to Q^2 about 2 (GeV/c)^2.Comment: 10 pages, 6 figures (1a,1b,1c,2a,2b,2c), to be published on Z. Phys.
Structural Properties of the Disordered Spherical and other Mean Field Spin Models
We extend the approach of Aizenman, Sims and Starr for the SK-type models to
their spherical versions. Such an extension has already been performed for
diluted spin glasses. The factorization property of the optimal structures
found by Guerra for the SK model, which holds for diluted models as well, is
verified also in the case of spherical systems, with the due modifications.
Hence we show that there are some common structural features in various mean
field spin models. These similarities seem to be quite paradigmatic, and we
summarize the various techniques typically used to prove the structural
analogies and to tackle the computation of the free energy per spin in the
thermodynamic limit.Comment: 24 page
Covariant Hamiltonian Dynamics with Negative Energy States
A relativistic quantum mechanics is studied for bound hadronic systems in the
framework of the Point Form Relativistic Hamiltonian Dynamics. Negative energy
states are introduced taking into account the restrictions imposed by a correct
definition of the Poincar\'e group generators. We obtain nonpathological,
manifestly covariant wave equations that dynamically contain the contributions
of the negative energy states. Auxiliary negative energy states are also
introduced, specially for studying the interactions of the hadronic systems
with external probes.Comment: 42 pages, submitted to EPJ
Telling the spin of the "Higgs boson" at the LHC
We assume that the Higgs boson or a possible resonance---playing its role in
strongly interacting models of electroweak symmetry breaking---has been
discovered at the LHC and propose a search strategy to determine its spin based
on two simple asymmetries in the ZZ, W+W- and t t-bar decays channels. We
consider some benchmark values for its mass (in the interval from 182 GeV/c^2
to 1 TeV/c^2) and discuss the relative advantages of the different decay
processes. A full analysis, including the background, is given. For a
center-of-mass energy of 14 TeV, we find that the lowest integrated luminosity
required to discriminate between the different spins is, depending on the
process and the resonance mass, between 40 fb^{-1} and 250 fb^{-1}.Comment: 17 pages, 3 figure
Electromagnetic Form Factors and the hCQM
We briefly report on results about the electromagnetic form factors of the
nucleon obtained with different models and then we concentrate our attention on
recent results obtained with the hypercentral constituent quark model (hCQM).Comment: 12 pages, 5 figures, Invited talk at 27th Symposium on Nuclear
Physics, Taxco, Guerrero, Mexico, 5-8 Jan 200
- …