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    Optical stark effect in the 2-photon spectrum of NO

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    A large optical Stark effect has been observed in the two-photon spectrum X(2)Pi yields A(2)Sigma(+)_ in NO. It is explained as a near-resonant process in which the upper state of the two-photon transition is perturbed by interactions with higher-lying electronic states coupled by the laser field. A theoretical analysis is presented along with coupling parameters determined from ab initio wave functions. The synthetic spectrum reproduces the major experimental features

    Azimuthal correlation between the (pl,pXb)(\vec{p}_l,\vec{p}_{X_b}) and (pl,Pt)(\vec{p}_l,\vec{P}_t) planes in the semileptonic rest frame decay of a polarized top quark: An O(αs)O(\alpha_s) effect

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    The azimuthal correlation between the planes formed by the vectors (p,pXb)(\vec{p}_\ell,\vec{p}_{X_b}) and (p,Pt)(\vec{p}_\ell,\vec{P}_t) in the semileptonic rest frame decay of a polarized top quark t()Xb+l++νt(\uparrow) \to X_b + l^+ + \nu_\ell belongs to a class of polarization observables involving the top quark which vanish at the Born term level in the standard model. We determine the next--to--leading order QCD corrections to the afore-mentioned azimuthal correlation and compare the result to the corresponding contribution of a non--standard--model right--chiral quark current.Comment: latex, 12 pages with 2 figures in the text, typos removed,comment and references added, replaced with published versio
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