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Measurement of the spin density matrix for the ρ0, K*0(892) and φ produced in Z0 decays

par Abreu, Pedro;Bertrand, Daniel ;Bricman, Charles ;Cao, Futian;Chen, Max;Deghorain, A.;De Brabandere, S.;De Clercq, Catherine;Herquet, Philippe ;Hoorelbeke, S.;Huet, Kathy;Lefebure, Véronique ;Lemonne, Jacques ;Tomaradze, A.;Van Lysebetten, Ann;Verbeure, F;Wickens, John H. ; [et al.]
Référence Physics letters. Section B, 406, 3, page (271-286)
Publication Publié, 1997-08

Article révisé par les pairs

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Résumé :

The spin density matrix elements for the ρ0, K*0(892) and φ produced in hadronic Z0 decays are measured in the DELPHI detector. There is no evidence for spin alignment of the K*0(892) and φ in the region xp ≤ 0.3 (xp = p/pbeam), where ρ00 = 0.33 ± 0.05 and ρ00 = 0.30 ± 0.04, respectively. In the fragmentation region, xp ≥ 0.4, there is some indication for spin alignment of the ρ0 and K*0(892), since ρ00 = 0.43 ± 0.05 and ρ00 = 0.46 ± 0.08, respectively. These values are compared with those found in meson-induced hadronic reactions. For the φ, ρ00 = 0.30 ± 0.04 for xp ≥ 0.4 and 0.55 ± 0.10 for xp ≥ 0.7. The off-diagonal spin density matrix element ρ1 - 1 is consistent with zero in all cases.© 1997 Published by Elsevier Science B.V.