Contribution to a conference proceedings/Contribution to a book

PUBDB-2023-00204

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Overview of HERMES Results on Longitudinal Spin Asymmetries

Marukyan, H. (Corresponding author)Extern* ; HERMES Collaboration

2022
Journal of the Physical Society of Japan

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Please use a persistent id in citations: doi:10.7566/JPSCP.37.020106  doi:10.3204/PUBDB-2023-00204

Abstract: The HERMES experiment collected a wealth of data using the 27.6 GeV polarized HERA lepton beam and various polarized and unpolarized gaseous targets. This allows for a series of unique measurements of observables sensitive to the multidimensional (spin) structure of the nucleon, in particular semi-inclusive deep-inelastic scattering (SIDIS) measurements, for which the HERMES dual-radiator ring-imaging Cherenkov counter provided final-hadron identification between 2 to 15 GeV for pions, kaons, and (anti)protons.In this contribution, longitudinal single- and double-spin asymmetries in SIDIS will be presented. The azimuthally uniform double-spin asymmetries using longitudinally polarized nucleons constrain the flavor dependence of the quark-spin contribution to the nucleon spin. For a first time, such asymmetries are explored differential in three dimensions in Bjorken-x and in the hadron kinematics z and P$_{h⊥}$ (which respectively represent the energy fraction and transverse momentum of the final-state hadron) simultaneously. This approach increases the quark-flavor sensitivity and allows to probe the transverse-momentum dependence of the helicity distribution. The measurement of hadron charge-difference asymmetries allows, under certain simplifying assumptions, the direct extraction of valence-quark polarizations. The azimuthal modulation of this double-spin as well as of the single-(beam)spin asymmetry probe novel quark-gluon-quark correlations through twist-3 distribution and fragmentation functions. Also here, asymmetries are explored in several dimensions. Furthermore, in case of the beam-spin asymmetry, results for electro-produced protons and antiprotons have become available. The beam-spin asymmetries for pions are compared to similar measurements for pions at CLAS and unidentified hadrons at COMPASS.

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Contributing Institute(s):

1. HERMES Kollaboration (HERMES)

Research Program(s):

1. 611 - Fundamental Particles and Forces (POF4-611) (POF4-611)

Experiment(s):

1. HERA: HERMES

Appears in the scientific report 2022

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