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Title
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A precise measurement of the polarisation at LEP-1
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Author
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Institution/Organisation
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DEPHI Collaboration
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Abstract
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| The tau polarisation has been studied with the e(+)e(-) --> tau(+)tau(-) data collected by the DELPHI detector at LEP in 1993, 1994 and 1995 around the Z resonance firstly through the exclusive decay channels ev (v) over bar, mu v (v) over bar, pi v, rho v and a(1)v and secondly with an inclusive hadronic analysis which benefits from a higher efficiency and a better systematic precision. The results have been combined with those previously published on 1990 to 1992 DELPHI data, to produce results which reflect the full LEP-1 statistics. The fit of the tau polarisation dependence on the production angle yielded the polarisation parameters A(tau) = 0.1359 +/- 0.0096 and A(epsilon) = 0.1382 +/- 0.0116. From these results the ratio of the vector and axial-vector effective couplings (v) over bar/(a) over bar(tau) = 0.0683 +/- 0.0048 and (v) over bar/(a) over bar(e) = 0.0694 +/- 0.0058 have been derived, compatible with e-tau universality. With the assumption of lepton universality, the ratio of vector to axial-vector effective couplings for leptons (v) over bar(l)/(a) over bar(l) = 0.0687 +/- 0.0037 was obtained, implying a value of the effective weak mixing angle sin(2) theta(eff)(lept) = 0.23282 +/- 0.00092. |
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Language
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English
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Source (journal)
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European physical journal : C : particles and fields. - Berlin
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Publication
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Berlin
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2000
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ISSN
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1434-6044
1434-6052
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DOI
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10.1007/S100520000363
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Volume/pages
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14
:4
(2000)
, p. 585-611
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ISI
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000088157000002
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Full text (Publisher's DOI)
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Full text (publisher's version - intranet only)
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