11,234 research outputs found

    O(\alpha_s) QCD Corrections to Spin Correlations in e−e+→ttˉe^- e^+ \to t \bar t process at the NLC

    Full text link
    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 O(αs)O(\alpha_s) QCD corrections to eL−e+e_L^- e^+ (eR−e+e_R^- e^+) scattering process increase the differential cross sections of the dominant spin component t↑tˉ↓t_{\uparrow}\bar{t}_{\downarrow} (t↓tˉ↑t_{\downarrow}\bar{t}_{\uparrow}) by ∼30\sim 30% and ∼(0.1\sim (0.1%-3%) depending on the scattering angle for s=400GeV\sqrt{s}=400 GeV and 1 TeV, respectively; (b) in {Off-diagonal basis} (Helicity basis), the dominant spin component makes up 99.8% (∼53\sim 53%) of the total cross section at both tree and one-loop level for s=400GeV\sqrt{s}=400 GeV, and the Off-diagonal basis therefore remains to be the optimal spin basis after the inclusion of O(αs)O(\alpha_s) 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

    Full text link
    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
    • …
    corecore