Abstract
We present measurements of Collins asymmetries in the inclusive process $e^+e^- \rightarrow h_1 h_2 X$, $h_1h_2=KK,\, K\pi,\, \pi\pi$, at the center-of-mass energy of 10.6 GeV, using a data sample of 468 fb$^{-1}$ collected by the BaBar experiment at the PEP-II $B$ factory at SLAC National Accelerator Center. Considering hadrons in opposite thrust hemispheres of hadronic events, we observe clear azimuthal asymmetries in the ratio of unlike- to like-sign, and unlike- to all charged $h_1 h_2$ pairs, which increase with hadron energies. The $K\pi$ asymmetries are similar to those measured for the $\pi\pi$ pairs, whereas those measured for high-energy $KK$ pairs are, in general, larger.
Highlights
52INFN Sezione di Pisaa; Dipartimento di Fisica, Universitadi Pisab; Scuola Normale Superiore di Pisac, I-56127 Pisa, Italy
In e+e− annihilation, one can measure the product of two Collins fragmentation function (FF), and detailed measurements have been made for pairs of charged pions [11,12,13]
No measurements are available for Kπ and KK pairs, which are sensitive to different quark-flavor combinations, in particular the contribution of the strange quark
Summary
We construct all the possible pairs of selected tracks reconstructed in opposite thrust hemispheres, and we calculate the corresponding azimuthal angles φ1, φ2, and φ0 in the respective reference frames. The normalized distributions can be parametrized with a cosine function: Rαi = bα + aiα cos βα, where α = 0, 12 indicates the reference frames, i = U, L, C the charge combination of hadron pairs, and β12(0) = φ12(2φ0).
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