18,627 research outputs found

### A Feynman graph selection tool in GRACE system

We present a Feynman graph selection tool {\tt grcsel}, which is an
interpreter written in C language. In the framework of {\tt GRACE}, it enables
us to get a subset of Feynman graphs according to given conditions.Comment: 3 pages, 2 figures, Latex, ACAT200

### ASCA Observation of the Lyman-limit Quasar PKS2145+067

X-ray observation of a famous Lyman-limit quasar PKS2145+067at z_em= 0.990
was carried with ASCA. The source showed a 2-10 keV flux of 1.3 E-11 erg cm^-2
sec^-1 (L_X = 2.5 E46 erg sec^-1 for H_0=50 km s^-1 Mpc^-1) described by a
power-law spectrum with a photon index Gamma=1.63 +/- 0.04 . In the ASCA energy
band, no excess absorption was detected implying the absorption column density
at z_ ab=0.791 was less than 1.6 E21 cm^-2 if absorbing medium had a metal
abundance of 0.5 solar. Comparison with previous Einstein and ROSAT
observations shows that PKS2145+067 has increased its luminosity by a factor of
2--3 between 1991 and 1998.Comment: 15 pages, 3figures, Latex(PASJadd,sty, PASJ95.sty) accepted in PAS

### Neutrino Oscillations in Intermediate States.II -- Wave Packets

We analyze oscillations of intermediate neutrinos in terms of the scattering
of particles described by Gaussian wave packets. We study a scalar model as in
a previous paper (I) but in realistic situations, where the two particles of
the initial state and final state are wave packets and neutrinos are in the
intermediate state. The oscillation of the intermediate neutrino is found from
the time evolution of the total transition probability between the initial
state and final state. The effect of a finite lifetime and a finite relaxation
time are also studied. We find that the oscillation pattern depends on the
magnitude of wave packet sizes of particles in the initial state and final
state and the lifetime of the initial particle. For $\Delta m^2_{21}=3\times
10^{-2}$ eV$^2$, the oscillation probability deviates from that of the standard
formula if the wave packet sizes are around $10^{-13}$ m for 0.4 MeV neutrino.Comment: 29 pages, 11 figures. typos corrected, appendix adde

### Evidence for Narrow S=+1 Baryon Resonance in Photo-production from Neutron

The gamma n -> K+ K- n reaction on 12C has been studied by measuring both K+
and K- at forward angles. A sharp baryon resonance peak was observed at 1.54 +-
0.01 GeV with a width smaller than 25 MeV and a Gaussian significance of 4.6
sigma. The strangeness quantum number (S) of the baryon resonance is +1. It can
be interpreted as a molecular meson-baryon resonance or alternatively as an
exotic 5-quark state (uudd{s_bar}) that decays into a K+ and a neutron. The
resonance is consistent with the lowest member of an anti-decuplet of baryons
predicted by the chiral soliton model.Comment: 12 pages, 3 encapsulated postscript figure

### Coordinate space proton-deuteron scattering calculations including Coulomb force effects

We present a practical method to solve the proton-deuteron scattering problem
at energies above the three-body breakup threshold, in which we treat
three-body integral equations in coordinate space accommodating long-range
proton-proton Coulomb interactions. The method is examined for phase shift
parameters, and then applied to calculations of differential cross sections in
elastic and breakup reactions, analyzing powers, etc. with a realistic
nucleon-nucleon force and three-nucleon forces. Effects of the Coulomb force
and the three-nucleon forces on these observables are discussed in comparing
with experimental data.Comment: 15 pages, 14 figures, submitted to PR

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