977 research outputs found
Exclusive Measurement of the Nonmesonic Weak Decay of ^{5}_{\Lambda}He Hypernucleus
We performed a coincidence measurement of two nucleons emitted from the
nonmesonic weak decay (NMWD) of ^{5}_{\Lambda}He formed via the
^{6}Li(\pi^+,K^+) reaction. The energies of two nucleons and the pair number
distributions in the opening angle between them were measured. In both np and
nn pairs, we observed a clean back-to-back correlation coming from the two-body
decay of \Lambda p --> n p and \Lambda n --> n n, respectively. The ratio of
the nucleon pair numbers was N_{nn}/N_{np}=0.45 \pm 0.11(stat)\pm 0.03(syst) in
the kinematic region of cos(theta_{NN}) < -0.8. Since each decay mode was
exclusively detected, the measured ratio should be close to the ratio of
\Gamma(\Lambda p --> np)/\Gamma(\Lambda n --> nn).
The ratio is consistent with recent theoretical calculations based on the
heavy meson/direct quark exchange picture.Comment: Submitted to Phys. Rev. lett., 4 pages, 3 figure
Measurement of the decay width of He
We have precisely measured decay width of \5LHe and
demonstrated significantly larger - overlap than expected
from the central repulsion - potential, which is derived from
YNG \Lambda$-nucleon interaction.Comment: 4 pages, 3 figure
Proton asymmetry in non-mesonic weak decay of light hypernuclei
We have obtained the decay asymmetry parameters in non-mesonic weak decay of
polarized Lambda-hypernuclei by measuring the proton asymmetry. The polarized
Lambda-hypernuclei, 5_Lambda-He, 12_Lambda-C, and 11_Lambda-B, were produced in
high statistics via the (pi^+,k^+) reaction at 1.05 GeV/c in the forward
angles. Preliminary analysis shows that the decay asymmetry parameters are very
small for these s-shell and p-shell hypernuclei.Comment: 4pages, 4figures, International Conference on Hypernuclear and
Strange Particle Physics (HYP2003
pi^0 decay branching ratios of 5_Lambda-He and 12_Lambda-C hypernuclei
We precisely measured pi^0 branching ratios of 5_Lambda-He and 12_Lambda-C
hypernuclei produced via (pi^+,k^+) reaction. Using these pi^0 branching ratios
with the pi^- branching ratios and the lifetimes, we obtained the pi^0 decay
widths and the non-mesonic weak decay widths at high statistics with the
accuracy of ~5 % (stat) for both hypernuclei.Comment: 4pages, 4figures, International Conference on Hypernuclear and
Strange Particle Physics (HYP2003
Nucleon-nucleon coincidence measurement in the non-mesonic weak decay of 5_Lambda-He and 12_Lambda-C hypernuclei
We have measured both yields of neutron-proton and neutron-neutron pairs
emitted from the non-mesonic weak decay process of 5_Lambda-He and 12_Lambda-C
hypernuclei produced via the (pi^+,K^+) reaction for the first time. We
observed clean back-to-back correlation of the np- and nn-pairs in the
coincidence spectra for both hypernuclei. The ratio of those back-to-back pair
yields, Nnn / Nnp, must be close to the ratio of neutron- and proton-induced
decay widths of the decay, Gn(Lambda n -> nn)/Gp(Lambda p -> np). The obtained
ratios for each hypernuclei support recent calculations based on short-range
interactions.Comment: 4 pages, 1 figure, International Nuclear Physics Conference (INPC
2004), Goteborg, Sweden, June 27 - July 2, 2004, to appear in Nuclear Physics
Automatic modulation classification using interacting multiple model - Kalman filter for channel estimation
YesA rigorous model for automatic modulation
classification (AMC) in cognitive radio (CR) systems is proposed
in this paper. This is achieved by exploiting the Kalman filter
(KF) integrated with an adaptive interacting multiple model
(IMM) for resilient estimation of the channel state information
(CSI). A novel approach is proposed, in adding up the squareroot singular values (SRSV) of the decomposed channel using the
singular value decompositions (SVD) algorithm. This new
scheme, termed Frobenius eigenmode transmission (FET), is
chiefly intended to maintain the total power of all individual
effective eigenmodes, as opposed to keeping only the dominant
one. The analysis is applied over multiple-input multiple-output
(MIMO) antennas in combination with a Rayleigh fading channel
using a quasi likelihood ratio test (QLRT) algorithm for AMC.
The expectation-maximization (EM) is employed for recursive
computation of the underlying estimation and classification
algorithms. Novel simulations demonstrate the advantages of the
combined IMM-KF structure when compared to the perfectly
known channel and maximum likelihood estimate (MLE), in
terms of achieving the targeted optimal performance with the
desirable benefit of less computational complexity loads
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