9,831 research outputs found
Associated strangeness production in the pp to pK^+K^-p and pp to pK^+ pi^0 Sigma^0 reactions
The total and differential cross sections for associated strangeness
production in the and reactions
have been studied in a unified approach using an effective Lagrangian model. It
is assumed that both the and final states originate from
the decay of the resonance which was formed in the production
chain . The available experimental data
are well reproduced, especially the ratio of the two total cross sections,
which is much less sensitive to the particular model of the entrance channel.
The significant coupling of the resonance to is
further evidence for large components in the quark wave function of
the resonance.Comment: Published in Phys. Rev.
Odd Parity Light Baryon Resonances
We use a consistent SU(6) extension of the meson-baryon chiral Lagrangian
within a coupled channel unitary approach in order to calculate the T-matrix
for meson-baryon scattering in s-wave. The building blocks of the scheme are
the pion and nucleon octets, the rho nonet and the Delta decuplet. We identify
poles in this unitary T-matrix and interpret them as resonances. We study here
the non exotic sectors with strangeness S=0,-1,-2,-3 and spin J=1/2, 3/2 and
5/2. Many of the poles generated can be associated with known N, Delta, Sigma,
Lambda and Xi resonances with negative parity. We show that most of the
low-lying three and four star odd parity baryon resonances with spin 1/2 and
3/2 can be related to multiplets of the spin-flavor symmetry group SU(6). This
study allows us to predict the spin-parity of the Xi(1620), Xi(1690), Xi(1950),
Xi(2250), Omega(2250) and Omega(2380) resonances, which have not been
determined experimentally yet.Comment: New appendix and references adde
On photohadronic processes in astrophysical environments
We discuss the first applications of our newly developed Monte Carlo event
generator SOPHIA to multiparticle photoproduction of relativistic protons with
thermal and power law radiation fields. The measured total cross section is
reproduced in terms of excitation and decay of baryon resonances, direct pion
production, diffractive scattering, and non-diffractive multiparticle
production. Non--diffractive multiparticle production is described using a
string fragmentation model. We demonstrate that the widely used
`--approximation' for the photoproduction cross section is reasonable
only for a restricted set of astrophysical applications. The relevance of this
result for cosmic ray propagation through the microwave background and hadronic
models of active galactic nuclei and gamma-ray bursts is briefly discussed.Comment: 9 pages including 4 embedded figures, submitted to PAS
Mixing of pseudoscalar-baryon and vector-baryon in the J(P)=1/2(-) sector and the N* (1535) and N* (1650) resonances
We study the meson-baryon interaction with J(P) = 1/2 using the hidden-gauge Lagrangians and mixing pseudoscalar meson-baryon with the vector meson-baryon states in a coupled channels scheme with pi N, eta N, K Lambda, K Sigma, rho N, and pi Delta (d wave). We fit the subtraction constants of each channel to the S-11 partial wave amplitude of the pi N scattering data extracted from the partial wave analysis of the George Washington group. We find two poles that we associate to the N*(1535) and the N*(1650) resonances, with negative subtraction constants of natural size, and compare the results with empirical determinations of these pole positions. We calculate the branching ratios for the different channels of each resonance and we find a good agreement with the experimental data. The cross section for the pi(-)p -> eta n scattering is also evaluated and compared with experiment
Antiproton-nucleus electromagnetic annihilation as a way to access the proton timelike form factors
Contrary to the reaction pbar + p --> e+ e- with a high momentum incident
antiproton on a free target proton at rest, in which the invariant mass M of
the (e+ e-) pair is necessarily much larger than the (pbar p) mass, in the
reaction pbar + d --> n e+ e- the value of M can take values near or below the
(pbar p) mass. In the antiproton-deuteron electromagnetic annihilation, this
allows to access the proton electromagnetic form factors in the time-like
region of q^2 near the (pbar p) threshold. We estimate the cross section
dsigma(pbar +d --> e+ e- n)/dM for an antiproton beam momentum of 1.5 GeV/c. We
find that near the (pbar p) threshold this cross section is about 1 pb/MeV. The
case of heavy nuclei target is also discussed. Elements of experimental
feasibility are presented for the process pbar + d --> n e+ e- in the context
of the Panda project.Comment: 14 pages, 11 figures. submitted to EPJ
Plasduino: an inexpensive, general purpose data acquisition framework for educational experiments
Based on the Arduino development platform, Plasduino is an open-source data
acquisition framework specifically designed for educational physics
experiments. The source code, schematics and documentation are in the public
domain under a GPL license and the system, streamlined for low cost and ease of
use, can be replicated on the scale of a typical didactic lab with minimal
effort. We describe the basic architecture of the system and illustrate its
potential with some real-life examples.Comment: 11 pages, 10 figures, presented at the XCIX conference of the
Societ\`a Italiana di Fisic
Light-Front Quantization and AdS/QCD: An Overview
We give an overview of the light-front holographic approach to strongly
coupled QCD, whereby a confining gauge theory, quantized on the light front, is
mapped to a higher-dimensional anti de Sitter (AdS) space. The framework is
guided by the AdS/CFT correspondence incorporating a gravitational background
asymptotic to AdS space which encodes the salient properties of QCD, such as
the ultraviolet conformal limit at the AdS boundary at , as well as
modifications of the geometry in the large infrared region to describe
confinement and linear Regge behavior. There are two equivalent procedures for
deriving the AdS/QCD equations of motion: one can start from the Hamiltonian
equation of motion in physical space time by studying the off-shell dynamics of
the bound state wavefunctions as a function of the invariant mass of the
constituents. To a first semiclassical approximation, where quantum loops and
quark masses are not included, this leads to a light-front Hamiltonian equation
which describes the bound state dynamics of light hadrons in terms of an
invariant impact variable which measures the separation of the partons
within the hadron at equal light-front time. Alternatively, one can start from
the gravity side by studying the propagation of hadronic modes in a fixed
effective gravitational background. Both approaches are equivalent in the
semiclassical approximation. This allows us to identify the holographic
variable in AdS space with the impact variable . Light-front
holography thus allows a precise mapping of transition amplitudes from AdS to
physical space-time. The internal structure of hadrons is explicitly introduced
and the angular momentum of the constituents plays a key role.Comment: Invited talk presented by GdT at the XIV School of Particles and
Fields, Morelia, Mexico, November 8-12, 201
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