Measurement of Λ polarization from Ζ decays

ALEPH Collaboration

doi:10.1016/0370-2693(96)00300-0

Measurement of Λ polarization from Ζ decays

ALEPH Collaboration

Université Paris-Sud
University of São Paulo
University of California at Santa Cruz
Florida State University
University of Barcelona
INFN Sezione di Bari
Institute of High Energy Physics, Chinese Academy of Sciences
European Organization for Nuclear Research
Université Blaise Pascal
Niels Bohr Institutet
NCSR Demokritos
University of Edinburgh
University of Florence
LNF-INFN
University of Turin
Ev-K2-CNR Committee
University of Glasgow
University of Heidelberg
Imperial College London
University of Innsbruck
Lancaster University
Johannes Gutenberg University
Max-Planck-Institut für Physik
Laboratoire de l'Accélérateur Linéaire
Kangwon National University
Scuola Normale Superiore di Pisa
Dipartimento di Scienze Biomediche
King's College London
Rutherford Appleton Laboratory
CEA, Irfu, SPP
The University of Sheffield
Universität Siegen
University of Trieste
University of Washington
University of Wisconsin-Madison

Research output: Contribution to journal › Article › peer-review

153 Citations (Scopus)

Abstract

The polarization of Λ baryons from Ζ decays is studied with the ALEPH apparatus. Evidence of longitudinal polarization of s quarks from Ζ decay is observed for the first time. The measured longitudinal Λ polarization is P^Λ_L = -0.32 ± 0.07 for z = p/p_beam > 0.3. This agrees with the prediction of -0.39 ± 0.08 from the standard model and the constituent quark model, where the error is due to uncertainties in the mechanism for Λ production. The observed Λ polarization is diluted with respect to the primary s quark polarization by Λ baryons without a primary s quark. Measurements of the Λ forward-backward asymmetry and of the correlation between back-to-back ΛΛ̄ pairs are used to check this dilution. In addition the transverse Λ polarization is measured. An indication of transverse polarization, more than two standard deviations away from zero, is found along the normal to the plane defined by the thrust axis and the Λ direction.

Original language	English
Pages (from-to)	319-330
Number of pages	12
Journal	Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume	374
Issue number	4
DOIs	https://doi.org/10.1016/0370-2693(96)00300-0
Publication status	Published - 9 May 1996

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10.1016/0370-2693(96)00300-0

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@article{ee102abe1263461ca5d10a058cbef064,

title = "Measurement of Λ polarization from Ζ decays",

abstract = "The polarization of Λ baryons from Ζ decays is studied with the ALEPH apparatus. Evidence of longitudinal polarization of s quarks from Ζ decay is observed for the first time. The measured longitudinal Λ polarization is PΛL = -0.32 ± 0.07 for z = p/pbeam > 0.3. This agrees with the prediction of -0.39 ± 0.08 from the standard model and the constituent quark model, where the error is due to uncertainties in the mechanism for Λ production. The observed Λ polarization is diluted with respect to the primary s quark polarization by Λ baryons without a primary s quark. Measurements of the Λ forward-backward asymmetry and of the correlation between back-to-back Λ{\=Λ} pairs are used to check this dilution. In addition the transverse Λ polarization is measured. An indication of transverse polarization, more than two standard deviations away from zero, is found along the normal to the plane defined by the thrust axis and the Λ direction.",

author = "\{ALEPH Collaboration\} and D. Buskulic and \{de Bonis\}, I. and D. Decamp and P. Ghez and C. Goy and Lees, \{J. P.\} and A. Lucotte and Minard, \{M. N.\} and P. Odier and B. Pietrzyk and M. Chmeissani and Crespo, \{J. M.\} and M. Delfino and I. Efthymiopoulos and E. Fernandez and M. Fernandez-Bosman and Ll Garrido and A. Juste and M. Martinez and S. Orteu and A. Pacheco and C. Padilla and F. Palla and A. Pascual and Perlas, \{J. A.\} and I. Riu and F. Sanchez and F. Teubert and A. Colaleo and D. Creanza and \{de Palma\}, M. and A. Farilla and G. Gelao and M. Girone and G. Iaselli and G. Maggi and M. Maggi and N. Marinelli and S. Natali and S. Nuzzo and A. Ranieri and G. Raso and F. Romano and F. Ruggieri and G. Selvaggi and L. Silvestris and P. Tempesta and G. Zito and X. Huang and M. Verderi",

year = "1996",

month = may,

day = "9",

doi = "10.1016/0370-2693(96)00300-0",

language = "English",

volume = "374",

pages = "319--330",

journal = "Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics",

issn = "0370-2693",

publisher = "Elsevier B.V.",

number = "4",

}

TY - JOUR

T1 - Measurement of Λ polarization from Ζ decays

AU - ALEPH Collaboration

AU - Buskulic, D.

AU - de Bonis, I.

AU - Decamp, D.

AU - Ghez, P.

AU - Goy, C.

AU - Lees, J. P.

AU - Lucotte, A.

AU - Minard, M. N.

AU - Odier, P.

AU - Pietrzyk, B.

AU - Chmeissani, M.

AU - Crespo, J. M.

AU - Delfino, M.

AU - Efthymiopoulos, I.

AU - Fernandez, E.

AU - Fernandez-Bosman, M.

AU - Garrido, Ll

AU - Juste, A.

AU - Martinez, M.

AU - Orteu, S.

AU - Pacheco, A.

AU - Padilla, C.

AU - Palla, F.

AU - Pascual, A.

AU - Perlas, J. A.

AU - Riu, I.

AU - Sanchez, F.

AU - Teubert, F.

AU - Colaleo, A.

AU - Creanza, D.

AU - de Palma, M.

AU - Farilla, A.

AU - Gelao, G.

AU - Girone, M.

AU - Iaselli, G.

AU - Maggi, G.

AU - Maggi, M.

AU - Marinelli, N.

AU - Natali, S.

AU - Nuzzo, S.

AU - Ranieri, A.

AU - Raso, G.

AU - Romano, F.

AU - Ruggieri, F.

AU - Selvaggi, G.

AU - Silvestris, L.

AU - Tempesta, P.

AU - Zito, G.

AU - Huang, X.

AU - Verderi, M.

PY - 1996/5/9

Y1 - 1996/5/9

N2 - The polarization of Λ baryons from Ζ decays is studied with the ALEPH apparatus. Evidence of longitudinal polarization of s quarks from Ζ decay is observed for the first time. The measured longitudinal Λ polarization is PΛL = -0.32 ± 0.07 for z = p/pbeam > 0.3. This agrees with the prediction of -0.39 ± 0.08 from the standard model and the constituent quark model, where the error is due to uncertainties in the mechanism for Λ production. The observed Λ polarization is diluted with respect to the primary s quark polarization by Λ baryons without a primary s quark. Measurements of the Λ forward-backward asymmetry and of the correlation between back-to-back ΛΛ̄ pairs are used to check this dilution. In addition the transverse Λ polarization is measured. An indication of transverse polarization, more than two standard deviations away from zero, is found along the normal to the plane defined by the thrust axis and the Λ direction.

AB - The polarization of Λ baryons from Ζ decays is studied with the ALEPH apparatus. Evidence of longitudinal polarization of s quarks from Ζ decay is observed for the first time. The measured longitudinal Λ polarization is PΛL = -0.32 ± 0.07 for z = p/pbeam > 0.3. This agrees with the prediction of -0.39 ± 0.08 from the standard model and the constituent quark model, where the error is due to uncertainties in the mechanism for Λ production. The observed Λ polarization is diluted with respect to the primary s quark polarization by Λ baryons without a primary s quark. Measurements of the Λ forward-backward asymmetry and of the correlation between back-to-back ΛΛ̄ pairs are used to check this dilution. In addition the transverse Λ polarization is measured. An indication of transverse polarization, more than two standard deviations away from zero, is found along the normal to the plane defined by the thrust axis and the Λ direction.

U2 - 10.1016/0370-2693(96)00300-0

DO - 10.1016/0370-2693(96)00300-0

M3 - Article

AN - SCOPUS:4244028997

SN - 0370-2693

VL - 374

SP - 319

EP - 330

JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

IS - 4

ER -

Measurement of Λ polarization from Ζ decays

Abstract

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