23,064 research outputs found
Evidence for the two pole structure of the Lambda(1405) resonance
The K^- p --> pi^0 pi^0 Sigma^0 reaction is studied within a chiral unitary
model. The distribution of pi^0 Sigma^0 states forming the Lambda(1405) shows,
in agreement with a recent experiment, a peak at 1420 MeV and a relatively
narrow width of Gamma = 38 MeV. The mechanism for the reaction is largely
dominated by the emission of a pi^0 prior to the K^- p interaction leading to
the Lambda(1405). This ensures the coupling of the Lambda(1405) to the K^- p
channel, thus maximizing the contribution of the second state found in chiral
unitary theories, which is narrow and of higher energy than the nominal
Lambda(1405). This is unlike the pi^- p --> K^0 \pi Sigma reaction, which gives
more weight to the pole at lower energy and with a larger width. The data of
these two experiments, together with the present theoretical analysis, provides
a firm evidence of the two pole structure of the Lambda(1405).Comment: 4 pages, 6 figure
Magnetic order in Ce0.95Nd0.05CoIn5: the Q-phase at zero magnetic field
We report neutron scattering experiment results revealing the nature of the
magnetic order occurring in the heavy fermion superconductor Ce0.95Nd0.05CoIn5,
a case for which an antiferromagnetic state is stabilized at a temperature
below the superconducting transition one. We evidence an incommensurate order
and its propagation vector is found to be identical to that of the magnetic
field induced antiferromagnetic order occurring in the stoichiometric
superconductor CeCoIn5, the so-called Q-phase. The commonality between these
two cases suggests that superconductivity is a requirement for the formation of
this kind of magnetic order and the proposed mechanism is the enhancement of
nesting condition by d-wave order parameter with nodes in the nesting area.Comment: submitted to Phys. Rev. Lett. on June 30th, 201
Experimental status of deeply bound kaonic states in nuclei
We review recent claims of the existence of deeply bound kaonic states in
nuclei. Also we study in details the (K-,p) reaction on C12 with 1 GeV/c
momentum kaon beam, based on which a deep kaon nucleus optical potential was
claimed in [1]. In our Monte Carlo simulation of this reaction we include not
only the quasi-elastic K- p scattering, as in [1], but also K- absorption by
one and two nucleons followed by the decay of the hyperon in pi N, which can
also produce strength in the region of interest. The final state interactions
in terms of multiple scattering of the K-, p and all other primary particles on
their way out of the nucleus is also considered. We will show that all these
additional mechanisms allow us to explain the observed spectrum with a
"standard" shallow kaon nucleus optical potential obtained in chiral models.
[1] T. Kishimoto et al., Prog. Theor. Phys. 118, 181 (2007).Comment: 5 pages, 3 figures. To be published in the Proceedings of the
International Workshop on Chiral Symmetry in Hadrons and Nuclei (Chiral10),
Valencia, Spain, June 21-24, 201
A escolha da semente de abóbora é muito importante.
Em experimentos de pesquisa realizados em áreas de agricultores familiares, a Embrapa Tabuleiros Costeiros de Aracaju (SE) detectou, no ano de 2009, a ocorrência da antracnose em Simão Dias, região Agreste de Sergipe, município com expressão no cultivo e comercialização da abóbora.bitstream/item/123123/1/escolha-da-semente.pd
Derivation of Source-Free Maxwell and Gravitational Radiation Equations by Group Theoretical Methods
We derive source-free Maxwell-like equations in flat spacetime for any
helicity "j" by comparing the transformation properties of the 2(2j+1) states
that carry the manifestly covariant representations of the inhomogeneous
Lorentz group with the transformation properties of the two helicity "j" states
that carry the irreducible representations of this group. The set of
constraints so derived involves a pair of curl equations and a pair of
divergence equations. These reduce to the free-field Maxwell equations for j=1
and the analogous equations coupling the gravito-electric and the
gravito-magnetic fields for j=2.Comment: 15 pages, no figures, to appear in Int. J. Mod. Phys.
A theoretical description of energy spectra and two-neutron separation energies for neutron-rich zirconium isotopes
Very recently the atomic masses of neutron-rich Zr isotopes, from Zr
to Zr, have been measured with high precision. Using a schematic
Interacting Boson Model (IBM) Hamiltonian, the evolution from spherical to
deformed shapes along the chain of Zr isotopes, describing at the same time the
excitation energies as well as the two-neutron separation energies, can be
rather well reproduced. The interplay between phase transitions and
configuration mixing of intruder excitations in this mass region is succinctly
addressed.Comment: Accepted in European Journal of Physics
Order parameter for the dynamical phase transition in Bose-Einstein condensates with topological modes
In a trapped Bose-Einstein condensate, subject to the action of an
alternating external field, coherent topological modes can be resonantly
excited. Depending on the amplitude of the external field and detuning
parameter, there are two principally different regimes of motion, with mode
locking and without it. The change of the dynamic regime corresponds to a
dynamic phase transition. This transition can be characterized by an effective
order parameter defined as the difference between fractional mode populations
averaged over the temporal period of oscillations. The behavior of this order
parameter, as a function of detuning, pumping amplitude, and atomic
interactions is carefully analyzed. A special attention is payed to numerical
calculations for the realistic case of a quadrupole exciting field and the
system parameters accessible in current experiments
Investigating entanglement entropy at small-x in DIS off protons and nuclei
In this work we analyse the entanglement entropy in deep inelastic scattering
off protons and nuclei. It is computed based on the formalism where the
partonic state at small-x is maximally entangled with proton being constituted
by large number of microstates occuring with equal probabilities. We consider
analytical expressions for the number of gluons, N_{gluon}, obtained from gluon
saturation models for the dipole-target amplitudes within the QCD color dipole
picture. In particular, the nuclear entanglement entropy per nucleon is
studied. We also study the underlying uncertainties on these calculations and
compare the results to similar investigations in literature.Comment: 11 pages, 5 figures and 1 table (revised, conclusions unchanged).
Extended version to be published in Physical Review
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