3,466 research outputs found
Scalar Nonets in Pole-Dominated QCD Sum Rules
The light scalar nonets are studied using the QCD sum rules for the
tetraquark operators. The operator product expansion for the correlators is
calculated up to dimension 12 and this enables us to perform analyses retaining
sufficient pole-dominance. To classify the light scalar nonets, we investigate
the dependence on current quark mass and flavor dynamics. Especially, to
examine the latter, we study separately SU(3) singlet and octet states, and
show that the number of annihilation diagrams is largely responsible for their
differences, which is also the case even after the inclusion of the finite
quark mass. Our results support the tetraquark picture for isosinglets, while
that for octets is not conclusive yet.Comment: 4 pages, 3 figure, Talk given at Chiral Symmetry in Hadron and
Nuclear Physics (Chiral07), November 13-16, 2007, Osaka Univ., Japa
Lepton Energy Asymmetry and Precision SUSY study at Hadron Colliders
We study the distribution of lepton pairs from the second lightest neutralino
decay \tilde{\chi}^0_2-->\tilde{l}l followed by \tilde{l}\to \tilde{\chi}^0_1
l. The distribution of the ratio of lepton transverse momenta A_T shows peak
structure if m_{ll}< m^{max}_{ll}/2 is required. The peak position A_T^{peak}
is described by a simple function of the ino and slepton masses in the
m_{ll}\sim 0 limit. When a moderate m_{ll} cut is applied, A_T^{peak} depends
on the \tilde{\chi}^0_2 velocity distribution, but the dependence would be
corrected by studying the lepton P_T distribution. A_T^{peak} and the edge of
m_{ll} distributions are used to determine the mass parameters involved in the
decay for parameters of interest to LHC experiments. For some cases the ino and
slepton masses may be determined within 10% by the lepton distribution only
independent of model assumptions. Correct combinations of A_{T}^{peak} and
m_{ll}^{edge} would be identified even if different \tilde{\chi}^0_2 decay
chains are co-existing. The analysis could be extended to the Tevatron energy
scale or other cascade decays.Comment: 31 pages, 15 figure
Self-resonant Coil for Contactless Electrical Conductivity Measurement under Pulsed Ultra-high Magnetic Fields
In this study, we develop experimental apparatus for contactless electrical
conductivity measurements under pulsed high magnetic fields over 100 T using a
self-resonant-type high-frequency circuit. The resonant power spectra were
numerically analyzed, and the conducted simulations showed that the apparatus
is optimal for electrical conductivity measurements of materials with high
electrical conductivity. The newly developed instruments were applied to a
high-temperature cuprate superconductor LaSrCuO to show
conductivity changes in magnetic fields up to 102 T with a good signal-to-noise
ratio. The upper critical field was determined with high accuracy.Comment: 11 pages, 5 figure
CFL Phase of High Density QCD at Non Zero Strange Quark Mass
We compute free energy of quark matter at asymptotically high baryon number
density in the presence of non zero strange quark mass including dynamics of
pseudo Nambu-Goldstone bosons due to chiral symmetry breaking, extending
previously existing analysis based on perturbative expansion in
We demonstrate that the CFL state has lower free
energy than the symmetric CFL state for . We also
calculate the spectrum of the fermionic quasiparticle excitations about the
kaon condensed ground state in the regime and find
that for the CFL-gCFL phase transition, the
leading order result reported in [1], is not modified.Comment: 16 pages, 3 figure
Dimension-six top-Higgs interaction and its effect in collider phenomenology
Measurement of the Yukawa interaction between the top quark and the Higgs
boson should be useful to clarify the mechanism of fermion mass generation.
We discuss the impact of non-standard interactions characterized by
dimension-six operators on the effective top Yukawa coupling.
The cross section of the process is calculated including these operators, and possible deviation
from the standard model prediction is evaluated under the constraint from
perturbative unitarity and current experimental data.
We find that if the new physics scale is in a TeV region, the cross section
can be significantly enhanced due to the non-standard interactions.
Such a large effect should be detectable at the International Linear
Collider.Comment: 22 pages, RevTex4, 20 eps figure
The Radial Distribution of Galaxies in LCDM clusters
We study the radial distribution of subhalos and galaxies using
high-resolution cosmological simulations of galaxy clusters formed in the
concordance LCDM cosmology. In agreement with previous studies, we find that
the radial distribution of subhalos is significantly less concentrated than
that of the dark matter, when subhalos are selected using their present-day
gravitationally bound mass. We show that the difference in the radial
distribution is not a numerical artifact and is due to tidal stripping. The
subhalos in the cluster core lose more than 70% of their initial mass since
accretion, while the average tidal mass loss for halos near the virial radius
is ~30%. This introduces a radial bias in the spatial distribution of subhalos
when they are selected using their tidally truncated mass. We demonstrate that
the radial bias disappears almost entirely if subhalos are selected using their
mass or circular velocity at the accretion epoch. The comparisons of the
results of dissipationless simulations to the observed distribution of galaxies
in clusters are therefore sensitive to the selection criteria used to select
subhalo samples. Using the simulations that include cooling and starformation,
we show that the radial distribution of subhalos is in reasonable agreement
with the observed radial distribution of galaxies in clusters for
0.1<R/R200<2.0, if subhalos are selected using the stellar mass of galaxies.
The radial bias is minimized in this case because the stars are located in the
centers of dark matter subhalos and are tightly bound. The stellar mass of an
object is therefore approximately conserved as the dark matter is stripped from
the outer regions. Nevertheless, the concentration of the radial distribution
of galaxies is systematically lower than that of the dark matter.Comment: submitted to ApJ, 12 pages, 12 figure
Galactic Halo Stars in Phase Space :A Hint of Satellite Accretion?
The present day chemical and dynamical properties of the Milky Way bear the
imprint of the Galaxy's formation and evolutionary history. One of the most
enduring and critical debates surrounding Galactic evolution is that regarding
the competition between ``satellite accretion'' and ``monolithic collapse'';
the apparent strong correlation between orbital eccentricity and metallicity of
halo stars was originally used as supporting evidence for the latter. While
modern-day unbiased samples no longer support the claims for a significant
correlation, recent evidence has been presented by Chiba & Beers
(2000,AJ,119,2843) for the existence of a minor population of high-eccentricity
metal-deficient halo stars. It has been suggested that these stars represent
the signature of a rapid (if minor) collapse phase in the Galaxy's history.
Employing velocity- and integrals of motion-phase space projections of these
stars, coupled with a series of N-body/Smoothed Particle Hydrodynamic (SPH)
chemodynamical simulations, we suggest an alternative mechanism for creating
such stars may be the recent accretion of a polar orbit dwarf galaxy.Comment: 12 pages(incl. figures). Accepted for publication in ApJ letters
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Crossover of the weighted mean fragment mass scaling in 2D brittle fragmentation
We performed vertical and horizontal sandwich 2D brittle fragmentation
experiments. The weighted mean fragment mass was scaled using the multiplicity
. The scaling exponent crossed over at . In the
small regime, the binomial multiplicative (BM) model was
suitable and the fragment mass distribution obeyed log-normal form. However, in
the large regime, in which a clear power-law cumulative
fragment mass distribution was observed, it was impossible to describe the
scaling exponent using the BM model. We also found that the scaling exponent of
the cumulative fragment mass distribution depended on the manner of impact
(loading conditions): it was 0.5 in the vertical sandwich experiment, and
approximately 1.0 in the horizontal sandwich experiment.Comment: 5 pages, 3 figure
Replica symmetry breaking transition of the weakly anisotropic Heisenberg spin glass in magnetic fields
The spin and the chirality orderings of the three-dimensional Heisenberg spin
glass with the weak random anisotropy are studied under applied magnetic fields
by equilibrium Monte Carlo simulations. A replica symmetry breaking transition
occurs in the chiral sector accompanied by the simultaneous spin-glass order.
The ordering behavior differs significantly from that of the Ising SG, despite
the similarity in the global symmetry. Our observation is consistent with the
spin-chirality decoupling-recoupling scenario of a spin-glass transition.Comment: 4 pages, 4 figure
Class A scavenger receptor 1 (MSR1) restricts hepatitis C virus replication by mediating toll-like receptor 3 recognition of viral RNAs produced in neighboring cells
Persistent infections with hepatitis C virus (HCV) may result in life-threatening liver disease, including cirrhosis and cancer, and impose an important burden on human health. Understanding how the virus is capable of achieving persistence in the majority of those infected is thus an important goal. Although HCV has evolved multiple mechanisms to disrupt and block cellular signaling pathways involved in the induction of interferon (IFN) responses, IFN-stimulated gene (ISG) expression is typically prominent in the HCV-infected liver. Here, we show that Toll-like receptor 3 (TLR3) expressed within uninfected hepatocytes is capable of sensing infection in adjacent cells, initiating a local antiviral response that partially restricts HCV replication. We demonstrate that this is dependent upon the expression of class A scavenger receptor type 1 (MSR1). MSR1 binds extracellular dsRNA, mediating its endocytosis and transport toward the endosome where it is engaged by TLR3, thereby triggering IFN responses in both infected and uninfected cells. RNAi-mediated knockdown of MSR1 expression blocks TLR3 sensing of HCV in infected hepatocyte cultures, leading to increased cellular permissiveness to virus infection. Exogenous expression of Myc-MSR1 restores TLR3 signaling in MSR1-depleted cells with subsequent induction of an antiviral state. A series of conserved basic residues within the carboxy-terminus of the collagen superfamily domain of MSR1 are required for binding and transport of dsRNA, and likely facilitate acidification-dependent release of dsRNA at the site of TLR3 expression in the endosome. Our findings reveal MSR1 to be a critical component of a TLR3-mediated pattern recognition receptor response that exerts an antiviral state in both infected and uninfected hepatocytes, thereby limiting the impact of HCV proteins that disrupt IFN signaling in infected cells and restricting the spread of HCV within the liver
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