9-14 September 2018
University of Ferrara
Europe/Rome timezone

Transversity and Lambda polarization in polarized semi-inclusive DIS at COMPASS

13 Sep 2018, 17:20
A10 (Polo degli Adelardi - Via Adelardi, 33)


Polo degli Adelardi - Via Adelardi, 33

Parallel Sessions Nucleon Helicity Structure Nucleon helicity structure


Andrea Moretti (TS)


One among the several methods proposed to access the transversity function h_1^q(x) in semi-inclusive DIS is the measurement of Lambda hyperons polarization, which can be quantified by studying the angular distribution of the proton emitted in the self-analyzing Lambda -> p pi^- decay. The struck quark inherits the transverse polarization of the target with a proportionality factor given by the ratio of h_1^q(x) with the unpolarized parton distribution function f_1^q(x). The transverse polarization of the initial quark is transferred to the fragmenting final quark in lepton-quark hard scattering, thus the polarization of the Lambda, measured with respect to the final quark spin axis, can carry information on transversity. Nowadays transversity is already quite well known for u and d quarks as it has been extracted from Collins and dihadron asymmetries, so that a Lambda polarization different from zero can be used to infer a possible transversity distribution for the s quark h_1^s(x), as well as information on the chiral-odd fragmentation function H_1^{Lambda,q}. The results obtained in COMPASS using data collected with a transversely polarized proton target will be shown in this talk, together with possible interpretations and with perspectives for the future COMPASS deuteron run to be held in 2021.

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