2,328 research outputs found
Semi-direct Gauge Mediation in Conformal Windows of Vector-like Gauge Theories
Direct gauge mediation models using the Intriligator-Seiberg-Shih (ISS)
metastable vacua suffer from the Landau pole problem of the standard model
gauge couplings and the existence of R symmetry forbidding gaugino masses.
These problems may be solved by using the recently proposed SUSY breaking
models in a conformal window of the vector-like gauge theory with
gauge singlets. In this paper we propose a model of gauge mediation based on
the SUSY-breaking model in the conformal window, and study the dynamics for the
SUSY breaking. In the model, there are massive vector-like bifundamental fields
charged under both and the standard model gauge group, and our model
can be regarded as a semi-direct gauge mediation model. The color number
can be small to avoid the Landau pole problem, and the R symmetry is also
broken under a reasonable assumption on the strong dynamics of the model. The
model possesses only one free parameter, and the gaugino and sfermion masses
are naturally of the same order.Comment: 21 pages, 1 figur
Contribution of Type Ia and Type II Supernovae for Intra-Cluster Medium Enrichment
The origin of the chemical composition of the intracluster medium (ICM) is
discussed in this paper. In particular, the contribution from Type Ia
supernovae (SNe Ia) to the ICM enrichment is shown to exist by adopting the
fitting formulas which have been used in the analysis of the solar system
abundances. Our analysis means that we can use the frequency of SNe Ia relative
to SNe II as the better measure than for
estimating the contribution of SNe Ia. Moreover, the chemical compositions of
ICMs are shown to be similar to that of the solar system abundances. We can
also reproduce the sulfur/iron abundance ratio within a factor of 2, which
means that the abundance problem of sulfur needs not to be emphasized too
strongly. We need more precise observations to conclude whether ICMs really
suffer the shortage problem of sulfur or not.Comment: 20 pages, LaTeX text and 15 postscript figures. Accepted for
publication in Astrophysical Journa
One-Loop Anomaly Mediated Scalar Masses and (g-2)_mu in Pure Gravity Mediation
We consider the effects of non-universalities among sfermion generations in
models of Pure Gravity Mediation (PGM). In PGM models and in many models with
strongly stabilized moduli, the gravitino mass may be O(100) TeV, whereas
gaugino masses, generated through anomalies at 1-loop, remain relatively light
O(1) TeV. In models with scalar mass universality, input scalar masses are
generally very heavy (m_0 \simeq m_{3/2}) resulting in a mass spectrum
resembling that in split supersymmetry. However, if one adopts a no-scale or
partial no-scale structure for the K\"ahler manifold, sfermion masses may
vanish at the tree level. It is usually assumed that the leading order anomaly
mediated contribution to scalar masses appears at 2-loops. However, there are
at least two possible sources for 1-loop scalar masses. These may arise if
Pauli-Villars fields are introduced as messengers of supersymmetry breaking. We
consider the consequences of a spectrum in which the scalar masses associated
with the third generation are heavy (order m_{3/2}) with 1-loop scalar masses
for the first two generations. A similar spectrum is expected to arise in GUT
models based on E_7/SO(10) where the first two generations of scalars act as
pseudo-Nambu-Goldstone bosons. Explicit breaking of this symmetry by the gauge
couplings then generates one-loop masses for the first two generations. In
particular, we show that it may be possible to reconcile the g_mu - 2
discrepancy with potentially observable scalars and gauginos at the LHC.Comment: 30 pages, 30 figure
Relaxing a constraint on the number of messengers in a low-scale gauge mediation
We propose a mechanism for relaxing a constraint on the number of messengers
in low-scale gauge mediation models. The Landau pole problem for the
standard-model gauge coupling constants in the low-scale gauge mediation can be
circumvented by using our mechanism. An essential ingredient is a large
positive anomalous dimension of messenger fields given by a large Yukawa
coupling in a conformal field theory at high energies. The positive anomalous
dimension reduces the contribution of the messengers to the beta function of
the standard-model gauge couplings.Comment: 22pages; v2:explanations expanded in sec.3.2, reference adde
On Myosin II dynamics in the presence of external loads
We address the controversial hot question concerning the validity of the
loose coupling versus the lever-arm theories in the actomyosin dynamics by
re-interpreting and extending the phenomenological washboard potential model
proposed by some of us in a previous paper. In this new model a Brownian motion
harnessing thermal energy is assumed to co-exist with the deterministic swing
of the lever-arm, to yield an excellent fit of the set of data obtained by some
of us on the sliding of Myosin II heads on immobilized actin filaments under
various load conditions. Our theoretical arguments are complemented by accurate
numerical simulations, and the robustness of the model is tested via different
choices of parameters and potential profiles.Comment: 6 figures, 8 tables, to appear on Biosystem
Indirect Signatures of Type I See-Saw Scenarios
We consider the low energy constraints that can be applied to type I see-saw
extensions of the Standard Model in which the right-handed neutrinos are taken
at the electroweak scale. In the reported scenarios, the flavour structure of
the charged current and neutral current weak interactions of the Standard Model
leptons with the heavy right-handed neutrinos is essentially determined by the
neutrino oscillation parameters. In this case, correlations among different
measurable phenomena in the lepton sector may provide compelling indirect
evidence of low energy see-saw mechanism of neutrino mass generation.Comment: 4 pages, 2 figures. Contributions to the Proceedings of the 12th
International Conference on Topics in Astroparticle and Underground Physics
(TAUP 2011), Munich, Germany, 5-9 September 201
Dirac Neutrino Masses from Generalized Supersymmetry Breaking
We demonstrate that Dirac neutrino masses in the experimentally preferred
range are generated within supersymmetric gauge extensions of the Standard
Model with a generalized supersymmetry breaking sector. If the usual
superpotential Yukawa couplings are forbidden by the additional gauge symmetry
(such as a U(1)'), effective Dirac mass terms involving the "wrong Higgs" field
can arise either at tree level due to hard supersymmetry breaking fermion
Yukawa couplings, or at one-loop due to nonanalytic or "nonholomorphic" soft
supersymmetry breaking trilinear scalar couplings. As both of these operators
are naturally suppressed in generic models of supersymmetry breaking, the
resulting neutrino masses are naturally in the sub-eV range. The neutrino
magnetic and electric dipole moments resulting from the radiative mechanism
also vanish at one-loop order.Comment: 5 pages, 1 figure, references added, note added on effective
superpotential mass terms generated upon U(1)' breakin
- …