11,234 research outputs found
O(\alpha_s) QCD Corrections to Spin Correlations in process at the NLC
Using a Generic spin basis, we present a general formalism of one-loop
radiative corrections to the spin correlations in the top quark pair production
at the Next Linear Collider, and calculate the O(\alpha_s) QCD corrections
under the soft gluon approximation. We find that: (a) in Off-diagonal basis,
the QCD corrections to () scattering
process increase the differential cross sections of the dominant spin component
() by
and depending on the scattering angle for
and 1 TeV, respectively; (b) in {Off-diagonal basis}
(Helicity basis), the dominant spin component makes up 99.8% () of
the total cross section at both tree and one-loop level for ,
and the Off-diagonal basis therefore remains to be the optimal spin basis after
the inclusion of QCD corrections.Comment: 12 pages, 4 figures, revised version (a few print mistakes are
corrected, some numerical results are modified, and Fig.4 is added
Lower Bound of Concurrence Based on Positive Maps
We study the concurrence of arbitrary dimensional bipartite quantum systems.
An explicit analytical lower bound of concurrence is obtained, which detects
entanglement for some quantum states better than some well-known separability
criteria, and improves the lower bounds such as from the PPT, realignment
criteria and the Breuer's entanglement witness.Comment: 8 pages, 1 figur
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