28,181 research outputs found
Induced top Yukawa coupling and suppressed Higgs mass parameters
In the scenarios with heavy top squarks, mass parameters of the Higgs field
must be fine-tuned due to a large logarithmic correction to the soft scalar
mass. We consider a new possibility that the top Yukawa coupling is small above
TeV scale. The large top mass is induced from strong Yukawa interaction of the
Higgs with another gauge sector, in which supersymmetry breaking parameters are
given to be small. Then it is found that the logarithmic correction to the
Higgs soft scalar mass is suppressed in spite of the strong coupling and the
fine-tuning is ameliorated. We propose an explicit model coupled to a
superconformal gauge theory which realizes the above situation.Comment: RevTeX4 style, 10 pages, 3 figure
Decay in the Nambu-Jona-Lasinio Model
We study the decays using the version of
the Nambu-Jona-Lasinio model with the effective nonleptonic weak
interaction. The amplitude is in reasonable agreement with
experimental data. On the other hand, the calculated
amplitudes strongly depend on the mass of the low-lying scalar-isoscalar
meson, and therefore give a strong constraint on the parameters of the
model.Comment: 10 pages, 3 Postscript figures, Talk given at YITP Workshp: From
Hadronic Matter to Quark Matter: Evolving View of Hadronic Matter, Kyoto,
Japan, Oct. 30-Nov. 1, 1994, to be published in Prog. Theor. Phys. Supp
Doubly magic nuclei from Lattice QCD forces at 469 MeV/c
We perform ab initio self-consistent Green's function calculations of the
closed shell nuclei He, O and Ca, based on
two-nucleon potentials derived from Lattice QCD simulations, in the flavor
SU(3) limit and at the pseudo-scalar meson mass of 469~MeV/c. The
nucleon-nucleon interaction is obtained using the HAL QCD method and its
short-distance repulsion is treated by means of ladder resummations outside the
model space. Our results show that this approach diagonalises ultraviolet
degrees of freedom correctly. Therefore, ground state energies can be obtained
from infrared extrapolations even for the relatively hard potentials of HAL
QCD. Comparing to previous Brueckner Hartree-Fock calculations, the total
binding energies are sensibly improved by the full account of many-body
correlations. The results suggest an interesting possible behaviour in which
nuclei are unbound at very large pion masses and islands of stability appear at
first around the traditional doubly-magic numbers when the pion mass is lowered
toward its physical value. The calculated one-nucleon spectral distributions
are qualitatively close to those of real nuclei even for the pseudo-scalar
meson mass considered here.Comment: 7 pages, 4 figures, RIKEN-QHP-286, RIKEN-iTHEMS-Report-1
X-ray and Radio Follow-up Observations of High-Redshift Blazar Candidates in the Fermi-LAT Unassociated Source Population
We report on the results of X-ray and radio follow-up observations of two GeV
gamma-ray sources 2FGL J0923.5+1508 and 2FGL J1502.1+5548, selected as
candidates for high-redshift blazars from unassociated sources in the {\it
Fermi} Large Area Telescope Second Source Catalog. We utilize the Suzaku
satellite and the VLBI Exploration of Radio Astrometry (VERA) telescopes for
X-ray and radio observations, respectively. For 2FGL J0923.5+1508, a possible
radio counterpart NVSS J092357+150518 is found at 1.4 GHz from an existing
catalog, but we do not detect any X-ray emission from it and derive a flux
upper limit 1.37 10 erg cm
s. Radio observations at 6.7 GHz also result in an upper limit of
19 mJy, implying a steep radio spectrum that is not
expected for a blazar. On the other hand, we detect X-rays from NVSS
J150229+555204, the potential 1.4 GHz radio counterpart of 2FGL J1502.1+5548.
The X-ray spectrum can be fitted with an absorbed power-law model with a photon
index =1.8 and the unabsorbed flux is =4.3 10 erg cm s. Moreover,
we detect unresolved radio emission at 6.7 GHz with flux =30.1
mJy, indicating a compact, flat-spectrum radio source. If NVSS J150229+555204
is indeed associated with 2FGL J1502.1+5548, we find that its multiwavelength
spectrum is consistent with a blazar at redshift .Comment: 24 pages, 7 figures, 6 tables, accepted for publication in Ap
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