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Conference papers

Transverse polarization of quark pairs created in string fragmentation

X. Artru 1 J. Czyzewski
1 Théorie
IP2I Lyon - Institut de Physique des 2 Infinis de Lyon
Abstract : Classical arguments predict that the quark and the antiquark of a pair created during string fragmentation are both transversely polarized in the direction of \hat z \times \vec q_T, where z is the direction of the pull exerted by the string on the antiquark and \vec q_T (-\vec q_T) is the transverse momentum of the quark (antiquark). The existence of this effect at the quantum-mechanical level is investigated by considering two analogous processes involving the tunnel effect in a strong field: (1) dissociation of the positronium atom (2) electron pair creation. In case (1) the positronium is taken in the 3P_0 state to simulate the vacuum quantum numbers J^PC = 0^++. Using the nonrelativistic WKB method, the final electron and positron are indeed found to be transversely polarized along \hat z \times \vec p_T. On the contrary, case (2), treated with the Dirac equation, shows no correlation between transverse polarization and transverse momentum both when the field is uniform and when it depends on z and t. The pair is nevertheless produced in a triplet spin state. The difference between these two results and their relevance to transverse spin asymmetry in inclusive reactions is discussed.
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Contributor : Sylvie Flores <>
Submitted on : Wednesday, December 2, 1998 - 1:46:52 PM
Last modification on : Thursday, February 6, 2020 - 4:28:09 PM

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X. Artru, J. Czyzewski. Transverse polarization of quark pairs created in string fragmentation. Cracow Epiphany Conference on spin effects in particle physics and Tempus Workshop, Jan 1998, Cracow, Poland. pp.2115-2127. ⟨in2p3-00003418⟩



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