The longitudinal spin transfer DLL to Λ and Λ¯ hyperons produced in high-energy polarized proton--proton collisions is expected to be sensitive to the helicity distribution functions of strange quarks and anti-quarks of the proton, and to longitudinally polarized fragmentation functions. We report an improved measurement of DLL from data obtained at a center-of-mass energy of s√ = 200 GeV with the STAR detector at RHIC. The data have an approximately twelve times larger figure-of-merit than prior results and cover |η|< 1.2 in pseudo-rapidity with transverse momenta pT up to 6 GeV/c. In the forward scattering hemisphere at largest pT, the longitudinal spin transfer is found to be DLL = -0.036 ± 0.048 (stat) ± 0.013(sys) for Λ hyperons and DLL = 0.032 ± 0.043\,(stat) ± 0.013\,(sys) for Λ¯ anti-hyperons. The dependences on η and pT are presented and compared with model evaluations.

Improved measurement of the longitudinal spin transfer to Λ and Λ hyperons in polarized proton-proton collisions at s =200 GeV

Contin, G.;
2018

Abstract

The longitudinal spin transfer DLL to Λ and Λ¯ hyperons produced in high-energy polarized proton--proton collisions is expected to be sensitive to the helicity distribution functions of strange quarks and anti-quarks of the proton, and to longitudinally polarized fragmentation functions. We report an improved measurement of DLL from data obtained at a center-of-mass energy of s√ = 200 GeV with the STAR detector at RHIC. The data have an approximately twelve times larger figure-of-merit than prior results and cover |η|< 1.2 in pseudo-rapidity with transverse momenta pT up to 6 GeV/c. In the forward scattering hemisphere at largest pT, the longitudinal spin transfer is found to be DLL = -0.036 ± 0.048 (stat) ± 0.013(sys) for Λ hyperons and DLL = 0.032 ± 0.043\,(stat) ± 0.013\,(sys) for Λ¯ anti-hyperons. The dependences on η and pT are presented and compared with model evaluations.
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https://journals.aps.org/prd/abstract/10.1103/PhysRevD.98.112009
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11368/2940139
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