Transverse Λ polarization in e+e− collisions

Leonard Gamberg; Zhong-Bo Kang; Ding Yu Shao; John Terry; Fanyi Zhao

Physics Letters B (Jul 2021)

Transverse Λ polarization in e+e− collisions

Leonard Gamberg,
Zhong-Bo Kang,
Ding Yu Shao,
John Terry,
Fanyi Zhao

Affiliations

Leonard Gamberg: Division of Science, Penn State Berks, Reading, PA 19610, USA
Zhong-Bo Kang: Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA; Mani L. Bhaumik Institute for Theoretical Physics, University of California, Los Angeles, CA 90095, USA; Center for Frontiers in Nuclear Science, Stony Brook University, Stony Brook, NY 11794, USA
Ding Yu Shao: Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA; Mani L. Bhaumik Institute for Theoretical Physics, University of California, Los Angeles, CA 90095, USA; Center for Frontiers in Nuclear Science, Stony Brook University, Stony Brook, NY 11794, USA; Department of Physics and Center for Field Theory and Particle Physics, Fudan University, Shanghai, 200433, China; Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Fudan University, Shanghai, 200433, China; Corresponding author.
John Terry: Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA; Mani L. Bhaumik Institute for Theoretical Physics, University of California, Los Angeles, CA 90095, USA
Fanyi Zhao: Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA; Mani L. Bhaumik Institute for Theoretical Physics, University of California, Los Angeles, CA 90095, USA

Journal volume & issue: Vol. 818
p. 136371

Abstract

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In this paper we study transverse polarization of Λ hyperons in single-inclusive leptonic annihilation. We show that when the transverse momentum of the Λ baryon is measured with respect to the thrust axis, a transverse momentum dependent (TMD) factorization formalism is required and the polarization is generated by the TMD polarizing fragmentation function (TMD PFF), D1T⊥. However, when the transverse momentum of the Λ baryon is measured with respect to the momentum of the initial leptons, a collinear twist-3 formalism is required and the polarization is generated by the intrinsic collinear twist-3 fragmentation function DT. Thus while these measurements differ from one another only by a change in the measurement axis, they probe different distribution functions. Recently, Belle measured a significant polarization in single-inclusive Λ baryon production as a function of the transverse momentum with respect to the thrust axis. However, this data can in principle be re-analyzed to measure the polarization as a function of the transverse momentum of the Λ baryon with respect to the lepton pair. This observable could be the first significant probe of the function, DT. In this paper, we first develop a TMD formalism for Λ polarization; we then present a recent twist-3 formalism that was established to describe Λ polarization. Using the TMD formalism, we demonstrate that the Λ polarization at OPAL and Belle can be described using the twist-2 TMD factorization formalism. Finally, we make a theoretical prediction for this polarization in the collinear twist-3 formalism at Belle.

Published in Physics Letters B

ISSN: 0370-2693 (Print); 1873-2445 (Online)
Publisher: Elsevier
Country of publisher: Netherlands
LCC subjects: Science: Physics
Website: http://www.journals.elsevier.com/physics-letters-b/

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