33,157 research outputs found
Pion structure in a nuclear medium
The structure and electroweak properties of the pion in symmetric nuclear
matter are presented in the framework of the Nambu--Jona-Lasinio model. The
pion is described as a bound state of a dressed quark-antiquark pair governed
by the Bethe-Salpeter equation. For the in-medium current-light-quark
properties we use the quark-meson coupling model, which describes successfully
the properties of hadron in a nuclear medium. We found that the light-quark
condensates, the pion decay constant and pion-quark coupling constant decrease
with increasing nuclear matter density. We then predict the modifications of
the charge radius of the charged pion in nuclear matter.Comment: 4 pages, 6 figures, accepted version for the QNP2018 proceedings, 8th
International Conference on Quarks and Nuclear Physics (QNP2018), November
13-17, 2018, Tsukuba, Ibaraki, Japa
Effects of medium modifications of nucleon form factors on neutrino scattering in dense matter
Effects of the in-medium modifications of nucleon form factors on neutrino
interaction in dense matter are presented by considering both the weak and
electromagnetic interactions of neutrinos with the constituents of the matter.
A relativistic mean field and the quark-meson coupling models are respectively
adopted for the effective nucleon mass and in-medium nucleon form factors. We
calculate the cross-section of neutrino scattering as well as the neutrino mean
free path. We found the cross sections of neutrino scattering in cold nuclear
medium decreases when the in-medium modifications of the nucleon weak and
electromagnetic form factors are taken into account.This reduction results in
the enhancement of the neutrino mean free path, in particular at the baryon
density of around a few times of the normal nuclear matter density.Comment: 4 pages, 2 figures, accepted for the QNP2018 proceedings, a talk
given at QNP2018, 8th International Conference on Quarks and Nuclear Physics
(QNP2018), November 13-17, 2018, Tsukuba, Ibaraki, Japa
Neutral scalar Higgs bosons in the USSM at the LHC
We study the possibility of discovering neutral scalar Higgs bosons in the
-extended supersymmetric standard model (USSM) at the CERN Large Hadron
Collider (LHC), by examining their productions via the exotic quark loop in the
gluon fusion process at leading order. It is possible in some parameter region
that the neutral scalar Higgs bosons may have stronger couplings with the
exotic quarks than with top quark. In this case, the exotic quarks may
contribute more significantly than top quark in productions of the neutral
scalar Higgs bosons in the gluon fusion process. We find that there is indeed
some parameter region in the USSM that supports our speculations.Comment: 18 pages; changed content; JPhys
Higher Derivative CP(N) Model and Quantization of the Induced Chern-Simons Term
We consider higher derivative CP(N) model in 2+1 dimensions with the
Wess-Zumino-Witten term and the topological current density squared term. We
quantize the theory by using the auxiliary gauge field formulation in the path
integral method and prove that the extended model remains renormalizable in the
large N limit. We find that the Maxwell-Chern-Simons theory is dynamically
induced in the large N effective action at a nontrivial UV fixed point. The
quantization of the Chern-Simons term is also discussed.Comment: 8 pages, no figure, a minor change in abstract, added Comments on the
quantization of the Chern-Simons term whose coefficient is also corrected,
and some references are added. Some typos are corrected. Added a new
paragraph checking the equivalence between (3) and (5), and a related
referenc
Coisotropic Branes, Noncommutativity, and the Mirror Correspondence
We study coisotropic A-branes in the sigma model on a four-torus by
explicitly constructing examples. We find that morphisms between coisotropic
branes can be equated with a fundamental representation of the noncommutatively
deformed algebra of functions on the intersection. The noncommutativity
parameter is expressed in terms of the bundles on the branes. We conjecture
these findings hold in general. To check mirror symmetry, we verify that the
dimensions of morphism spaces are equal to the corresponding dimensions of
morphisms between mirror objects.Comment: 13 page
Nonvolatile memories using deep traps formed in HfOâ by Nb ion implantation
We report nonvolatile memories (NVMs) based on deep-energy trap levels formed in HfOâ by metal ion implantation. A comparison of Nb- and Ta-implanted samples shows that suitable charge-trapping centers are formed in Nb-implanted samples, but not in Ta-implanted samples. This is consistent with density-functional theory calculations which predict that only Nb will form deep-energy levels in the bandgap of HfOâ. Photocurrent spectroscopy exhibits characteristics consistent with one of the trap levels predicted in these calculations. Nb-implanted samples showing memory windows in capacitanceâvoltage (V) curves always exhibit current (I) peaks in IâV curves, indicating that NVM effects result from deep traps in HfOâ. In contrast, Ta-implanted samples show dielectric breakdowns during the IâV sweeps between 5 and 11 V, consistent with the fact that no trap levels are present. For a sample implanted with a fluence of 10ÂčÂłNb cmâ»ÂČ, the charge losses after 10⎠s are âŒ9.8 and âŒ25.5% at room temperature (RT) and 85°C, respectively, and the expected charge loss after 10 years is âŒ34% at RT, very promising for commercial NVMs
Molecular beam epitaxial growth of high-quality InSb on InP and GaAs substrates
Epitaxial layers of InSb were grown on InP and GaAs substrates by molecular beam epitaxy. The dependence of the epilayer quality on flux ratio, J sub Sb4/J sub In, was studied. Deviation from an optimum value of J sub Sb4/J sub In (approx. 2) during growth led to deterioration in the surface morphology and the electrical and crystalline qualities of the films. Room temperature electron mobilities as high as 70,000 and 53,000 sq cm /V-s were measured in InSb layers grown on InP and GaAs substrates, respectively. Unlike the previous results, the conductivity in these films is n-type even at T = 13 K, and no degradation of the electron mobility due to the high density of dislocations was observed. The measured electron mobilities (and carrier concentrations) at 77 K in InSb layers grown on InP and GaAs substrates are 110,000 sq cm/V-s (3 x 10(15) cm(-3)) and 55,000 sq cm/V-s (4.95 x 10(15) cm(-3)), respectively, suggesting their application to electronic devices at cryogenic temperatures
Probing High Redshift Radiation Fields with Gamma-Ray Absorption
The next generation of gamma-ray telescopes may be able to observe gamma-ray
blazars at high redshift, possibly out to the epoch of reionization. The
spectrum of such sources should exhibit an absorption edge due to
pair-production against UV photons along the line of sight. One expects a sharp
drop in the number density of UV photons at the Lyman edge E_{L}. This implies
that the universe becomes transparent after gamma-ray photons redshift below E
(m_{e}c^2)^{2}/E_{L} 18 GeV. Thus, there is only a limited redshift interval
over which GeV photons can pair produce. This implies that any observed
absorption will probe radiation fields in the very early universe, regardless
of the subsequent star formation history of the universe. Furthermore,
measurements of differential absorption between blazars at different redshifts
can cleanly isolate the opacity due to UV emissivity at high redshift. An
observable absorption edge should be present for most reasonable radiation
fields with sufficient energy to reionize the universe. Ly-alpha photons may
provide an important component of the pair-production opacity. Observations of
a number of blazars at different redshifts will thus allow us to probe the rise
in comoving UV emissivity with time.Comment: ApJ accepted version, minor changes. 19 pages, 5 figure
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