160,027 research outputs found
Medium effects of magnetic moments of baryons on neutron stars under strong magnetic fields
We investigate medium effects due to density-dependent magnetic moments of
baryons on neutron stars under strong magnetic fields. If we allow the
variation of anomalous magnetic moments (AMMs) of baryons in dense matter under
strong magnetic fields, AMMs of nucleons are enhanced to be larger than those
of hyperons. The enhancement naturally affects the chemical potentials of
baryons to be large and leads to the increase of a proton fraction.
Consequently, it causes the suppression of hyperons, resulting in the stiffness
of the equation of state. Under the presumed strong magnetic fields, we
evaluate relevant particles' population, the equation of state and the maximum
masses of neutron stars by including density-dependent AMMs and compare them
with those obtained from AMMs in free space
Determination of Intrinsic Ferroelectric Polarization in Orthorhombic Manganites with E-type Spin Order
By directly measuring electrical hysteresis loops using the Positive-Up
Negative-Down (PUND) method, we accurately determined the remanent
ferroelectric polarization Pr of orthorhombic RMnO3 (R = Ho, Tm, Yb, and Lu)
compounds below their E-type spin ordering temperatures. We found that LuMnO3
has the largest Pr of 0.17 uC/cm^2 at 6 K in the series, indicating that its
single-crystal form can produce a Pr of at least 0.6 \muuC/cm^2 at 0 K.
Furthermore, at a fixed temperature, Pr decreases systematically with
increasing rare earth ion radius from R = Lu to Ho, exhibiting a strong
correlation with the variations in the in-plane Mn-O-Mn bond angle and Mn-O
distances. Our experimental results suggest that the contribution of the Mn t2g
orbitals dominates the ferroelectric polarization.Comment: 16 pages, 4 figure
Flavor SU(3) analysis of charmless B->PP decays
We perform a global fits to charmless decays which independently
constrain the vertex of the unitarity triangle. The
fitted amplitudes and phase are used to predict the branching ratios and CP
asymmetries of all decay modes, including those of the system. Different
schemes of SU(3) breaking in decay amplitude sizes are analyzed. The
possibility of having a new physics contribution to decays is also
discussed.Comment: 3 pages, 2 figs. Talk given at EPS-HEP07 To appear in the
proceedings, Reference adde
Effective Nonlinear Schr\"odinger Equations for Cigar-Shaped and Disk-Shaped Fermi Superfluids at Unitarity
In the case of tight transverse confinement (cigar-shaped trap) the
three-dimensional (3D) nonlinear Schr\"odinger equation, describing superfluid
Fermi atoms at unitarity (infinite scattering length ), is
reduced to an effective one-dimensional form by averaging over the transverse
coordinates. The resultant effective equation is a 1D nonpolynomial Schrodinger
equation, which produces results in good agreement with the original 3D one. In
the limit of small and large fermion number the nonlinearity is of simple
power-law type. A similar reduction of the 3D theory to a two-dimensional form
is also performed for a tight axial confinement (disk-shaped trap). The
resultant effective 2D nonpolynomial equation also produces results in
agreement with the original 3D equation and has simple power-law nonlinearity
for small and large . For both cigar- and disk-shaped superfluids our
nonpolynomial Schr\"odinger equations are quite attractive for phenomenological
application.Comment: 22 pages, 5 figure
Limits on Interactions between Weakly Interacting Massive Particles and Nucleons Obtained with NaI(Tl) crystal Detectors
Limits on the cross section for weakly interacting massive particles (WIMPs)
scattering off nucleons in the NaI(Tl) detectors at the Yangyang Underground
Laboratory are obtained with a 2967.4 kg*day data exposure. Nuclei recoiling
are identified by the pulse shape of scintillating photon signals. Data are
consistent with no nuclear recoil hypothesis, and 90% confidence level upper
limits are set. These limits partially exclude the DAMA/LIBRA region of
WIMP-sodium interaction with the same NaI(Tl) target detector. This 90%
confidence level upper limit on WIMP-nucleon spin-independent cross section is
3.26*10^-4 pb for a WIMP mass at 10 GeV/c^2
Symplectic embedding and Hamilton-Jacobi analysis of Proca model
Following the symplectic approach we show how to embed the Abelian Proca
model into a first-class system by extending the configuration space to include
an additional pair of scalar fields, and compare it with the improved Dirac
scheme. We obtain in this way the desired Wess-Zumino and gauge fixing terms of
BRST invariant Lagrangian. Furthermore, the integrability properties of the
second-class system described by the Abelian Proca model are investigated using
the Hamilton-Jacobi formalism, where we construct the closed Lie algebra by
introducing operators associated with the generalized Poisson brackets.Comment: 24 page
Pulse-shape discrimination between electron and nuclear recoils in a NaI(Tl) crystal
We report on the response of a high light-output NaI(Tl) crystal to nuclear
recoils induced by neutrons from an Am-Be source and compare the results with
the response to electron recoils produced by Compton scattered 662 keV
-rays from a Cs source. The measured pulse-shape discrimination
(PSD) power of the NaI(Tl) crystal is found to be significantly improved
because of the high light output of the NaI(Tl) detector. We quantify the PSD
power with a quality factor and estimate the sensitivity to the interaction
rate for weakly interacting massive particles (WIMPs) with nucleons, and the
result is compared with the annual modulation amplitude observed by the
DAMA/LIBRA experiment. The sensitivity to spin-independent WIMP-nucleon
interactions based on 100 kgyear of data from NaI detectors is estimated
with simulated experiments, using the standard halo model.Comment: 11page
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