11,543 research outputs found
Study of unstable particle through the spectral function in O(4) theory
We test application of the maximum entropy method to decompose the states
contributing to the unstable correlation function through the spectral
function in the four dimensional O(4) theory. Reliable results are
obtained for the mass and two-particle state energy using
only the correlation function. We also find that the property of the
particle is different between the unstable ()
and stable () cases.Comment: Lattice2002(spectrum), 3 page
Two-Nucleon Bound States in Quenched Lattice QCD
We address the issue of bound state in the two-nucleon system in lattice QCD.
Our study is made in the quenched approximation at the lattice spacing of a =
0.128 fm with a heavy quark mass corresponding to m_pi = 0.8 GeV. To
distinguish a bound state from an attractive scattering state, we investigate
the volume dependence of the energy difference between the ground state and the
free two-nucleon state by changing the spatial extent of the lattice from 3.1
fm to 12.3 fm. A finite energy difference left in the infinite spatial volume
limit leads us to the conclusion that the measured ground states for not only
spin triplet but also singlet channels are bounded. Furthermore the existence
of the bound state is confirmed by investigating the properties of the energy
for the first excited state obtained by 2x2 diagonalization method. The
scattering lengths for both channels are evaluated by applying the finite
volume formula derived by Luscher to the energy of the first excited states.Comment: 34 pages, 28 figure
Nuclear Quadrupole Effects in Deeply Bound Pionic Atoms
We have studied nuclear quadrupole deformation effects in deeply bound pionic
atoms theoretically. We have evaluated the level shifts and widths of the
hyperfine components using the first order perturbation theory and compared
them with the effects of neutron skin. We conclude that the nuclear quadrupole
deformation effects for deeply bound and states are very difficult to
observe and that the effects could be observed for states. We also
conclude that the deformation effects are sensitive to the parameters of the
pion-nucleus optical potential.Comment: Latex 11pages, Figures available on reques
Picosecond time-resolved fluorescence spectra of photosystem I and II in Chlorella pyrenoidosa
AbstractPicosecond time-resolved fluorescence spectra emitted from intact cells of the green alga Chlorella pyrenoidosa have been measured by means of a new detection technique using a microchannel-plate photomultiplier. A fluorescence band (F700) was observed at 690–730 nm in the initial time region (0–180 ps), in addition to the well-known spectrum (F685) of photosystem II (PS II)-chlorophyll a (Chla) with a peak at 685 nm. F700 decays rapidly with lifetime of 104 ps, while F685 decays much more slowly in bi-exponential form with lifetimes of 0.64 and 1.7 ns. Appearance of F700 is independent of closure of the reaction center II (RC II). F700 is thus assigned to the fluorescence from PS I-Chl a, whose decay is governed by a fast energy transfer process from the antenna Chl aof PS I to P700 of RC I
Realistic calculations of Kbar-N-N, Kbar-N-N-N, and Kbar-Kbar-N-N quasibound states
Binding energies and widths of three-body KbarNN, and of four-body KbarNNN
and KbarKbarNN nuclear quasibound states are calculated in the hyperspherical
basis, using realistic NN potentials and subthreshold energy dependent chiral
KbarN interactions. Results of previous K^-pp calculations are reproduced and
an upper bound is placed on the binding energy of a K^-d quasibound state. A
self consistent handling of energy dependence is found to restrain binding,
keeping the calculated four-body ground-state binding energies to relatively
low values of about 30 MeV. The lightest strangeness -2 particle-stable Kbar
nuclear cluster is most probably KbarKbarNN. The calculated Kbar N -> pi Y
conversion widths range from approximately 30 MeV for the KbarNNN ground state
to approximately 80 MeV for the KbarKbarNN ground state.Comment: v3 matching journal publicatio
Studying Strange Meson Production with FOPI
The production of mesons containing strangeness is studied using elementary
and heavy-ion probes with the FOPI detector at GSI-SIS. The observed inclusive
cross section of neutral kaons points to an in-medium modification in the
production. The momentum dependent ratio of cross sections of light and heavy
target nuclei turns out to be a sensitive observable for the in-medium
potential strength in transport codes. The experiments will continue studying
the production of charged kaons with elementary probes including the search for
deeply bound antikaon nuclear clusters in proton proton collisions.Comment: Proceedings of the 10th International Workshop on Meson Production,
Properties and Interaction (MESON2008), Krak\'{o}w, Polan
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