15,489 research outputs found
Nontriviality of Gauge-Higgs-Yukawa System and Renormalizability of Gauged NJL Model
In the leading order of a modified 1/Nc expansion, we show that a class of
gauge-Higgs-Yukawa systems in four dimensions give non-trivial and well-defined
theories in the continuum limit. The renormalized Yukawa coupling y and the
quartic scalar coupling \lambda have to lie on a certain line in the
(y,\lambda) plane and the line terminates at an upper bound. The gauged
Nambu--Jona-Lasinio (NJL) model in the limit of its ultraviolet cutoff going to
infinity, is shown to become equivalent to the gauge-Higgs-Yukawa system with
the coupling constants just on that terminating point. This proves the
renormalizability of the gauged NJL model in four dimensions. The effective
potential for the gauged NJL model is calculated by using renormalization group
technique and confirmed to be consistent with the previous result by Kondo,
Tanabashi and Yamawaki obtained by the ladder Schwinger-Dyson equation.Comment: 32 pages, LaTeX, 3 Postscript Figures are included as uuencoded files
(need `epsf.tex'), KUNS-1278, HE(TH) 94/10 / NIIG-DP-94-2. (Several
corrections in the introduction and references.
Comments on differential cross section of phi-meson photoproduction at threshold
We show that the differential cross section d_sigma/d_t of gamma p --> \phi p
reaction at the threshold is finite and its value is crucial to the mechanism
of the phi meson photoproduction and for the models of phi-N interaction.Comment: 8 pages, 2 figure
Enhanced thermoelectric properties by Ir doping of PtSb2 with pyrite structure
The effects of Ir doping on the thermoelectric properties of Pt1-xIrxSb2 (x =
0, 0.01, 0.03, and 0.1) with pyrite structure were studied. Measurements of
electrical resistivity rho, Seebeck coefficient S, and thermal conductivity
kappa were conducted. The results showed an abrupt change from semiconducting
behavior without Ir (x = 0) to metallic behavior at x = 0.01. The sample with x
= 0.01 exhibited large S and low rho, resulting in a maximum power factor
(S^2/rho) of 43 muW/cmK^2 at 400 K. The peculiar "pudding mold"-type electronic
band dispersion could explain the enhanced thermoelectric properties in the
metallic state.Comment: 3 pages, 2 figure
An improved method for determining the DC magnetization curve using a ring specimen
When the DC magnetization curve (B-H) of nonoriented material is measured in a ring specimen, there is an intrinsic error due to the assumption that the mean magnetic path length is equal to the mean geometric path length. A novel method for determining the B-H curve accurately is proposed. The validity of the method is verified by experiments</p
Antiproton Production in p+d Reaction at Subthreshold Energies
An enhancement of antiprotons produced in p+d reaction in comparison with
ones in p+p elementary reaction is investigated.
In the neighborhood of subthreshold energy the enhancement is caused by the
difference of available energies for antiproton production. The cross section
in p+d reaction, on the other hand, becomes just twice of the one in elementary
p+p reaction at the incident energy far from the threshold energy when
non-nucleonic components in deuteron target are not considered.Comment: LaTeX,7 pages with 5 eps figure
Search for Anomalous Couplings in Top Decay at Hadron Colliders
We present a quantitative study on sensitivities to the top-decay anomalous
couplings, taking into account realistic experimental conditions expected at
Tevatron and LHC. A double angular distribution of W and charged lepton in the
top decay is analyzed, using ttbar events in the lepton+jets channel. In order
to improve sensitivities to the anomalous couplings, we apply two techniques:
(1) We use a likelihood fitting method for full kinematical reconstruction of
each top event. (2) We develop a new effective spin reconstruction method for
leptonically-decayed top quarks; this method does not require spin information
of the antitop side. For simplicity, we neglect couplings of right-handed
bottom quark as well as CP violating couplings. The 95% C.L. estimated bound on
a ratio of anomalous couplings reads -0.81 < f_2/f_1 < -0.70,
-0.12<f_2/f_1<0.14 using 1000 reconstructed top events at Tevatron, while
-0.74<f_2/f_1<-0.72, -0.01<f_2/f_1<0.01 is expected with 100k reconstructed top
events at LHC, where only statistical errors are taken into account. A two-fold
ambiguity in the allowed range remains when the number of events exceeds a few
hundred.Comment: 21 pages, 15 figure
Electronic properties of alkali-metal loaded zeolites -- a "supercrystal" Mott insulator
First-principles band calculations are performed for the first time for an
open-structured zeolite (LTA) with guest atoms (potassium) introduced in their
cages. A surprisingly simple band structure emerges, which indicates that this
system may be regarded as a "supercrystal", where each cluster of guest atoms
with diameter 10\AA acts as a "superatom" with well-defined - and
-like orbitals, which in turn form the bands around the Fermi energy. The
calculated Coulomb and exchange energies for these states turn out to be in the
strongly-correlated regime. With the dynamical mean-field theory we show the
system should be on the Mott-insulator side, and, on a magnetic phase diagram
for degenerate-orbital systems, around the ferromagnetic regime, in accord with
experimental results. We envisage this class of systems can provide a new
avenue for materials design.Comment: 4 pages, 4 figure
R&D Status of Nuclear Emulsion For Directional Dark Matter Search
In this study, we are doing R&D for directional dark matter search with
nuclear emulsion. First of all, higher resolution nuclear emulsion with fine
silver halide crystals was developed in the production facility of emulsion at
Nagoya university, and we confirmed that it can detect the expected nuclear
recoil tracks. The readout of submicron tracks was required the new technology.
We developed the expansion technique, and could readout the signal by shape
analysis with optical microscopy. The two dimensional angular resolution is 36
degrees at the original track length of range from 150nm to 200nm with optical
microscopy. Finally we demonstrated by using recoiled nuclei induced by 14.8MeV
neutron, and confirmed the technique.Moreover, we developed the X-ray
microscope system with SPring-8 as final check with higher resolution of
selected candidate tracks with optical microscopy. The angular resolution was
improved from 31 degrees with optical microscopy to 17degrees with X-ray
microscopy at the track length of range from 150nm to 250nm. We are developing
the practical system and planning for start of the test running with prototype
detector.Comment: Proceedings of the 3rd International conference on Directional
Detection of Dark Matter (CYGNUS 2011), Aussois, France, 8-10 June 201
Self-Force on a Scalar Charge in Circular Orbit around a Schwarzschild Black Hole
In an accompanying paper, we have formulated two types of regulariz_ation methods to calculate the scalar self-force on a particle of charge moving around a black hole of mass , one of which is called the ``power expansion regularization''. In this paper, we analytically evaluate the self-force (which we also call the reaction force) to the third post-Newtonian (3PN) order on the scalar particle in circular orbit around a Schwarzschild black hole by using the power expansion regularization. It is found that the -component of the self-force arises at the 3PN order, whereas the - and -components, which are due to the radiation reaction, appear at the 2PN and 1.5PN orders, respectively
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