The observation of beam spin asymmetries in two-pion production in semi-inclusive deep inelastic scattering off an unpolarized proton target is reported. The data presented here were taken in the fall of 2018 with the CLAS12 spectrometer using a 10.6 GeV longitudinally spin-polarized electron beam delivered by CEBAF at JLab. The measured asymmetries provide the first opportunity to extract the parton distribution function e(x), which provides information about the interaction between gluons and quarks, in a collinear framework that offers cleaner access than previous measurements. The asymmetries also constitute the first ever signal sensitive to the helicity-dependent two-pion fragmentation function G(1)(perpendicular to). A clear sign change is observed around the rho mass that appears in model calculations and is indicative of the dependence of the produced pions on the helicity of the fragmenting quark.
Hayward, T.b., Dilks, C., Vossen, A., Avakian, H., Adhikari, S., Angelini, G., et al. (2021). Observation of beam spin asymmetries in the process ep →e′π+π-X with CLAS12. PHYSICAL REVIEW LETTERS, 126(15), 1-6 [10.1103/PhysRevLett.126.152501].
Observation of beam spin asymmetries in the process ep →e′π+π-X with CLAS12
D'Angelo A.Membro del Collaboration Group
;Lanza L.;Rizzo A.Membro del Collaboration Group
;
2021-04-12
Abstract
The observation of beam spin asymmetries in two-pion production in semi-inclusive deep inelastic scattering off an unpolarized proton target is reported. The data presented here were taken in the fall of 2018 with the CLAS12 spectrometer using a 10.6 GeV longitudinally spin-polarized electron beam delivered by CEBAF at JLab. The measured asymmetries provide the first opportunity to extract the parton distribution function e(x), which provides information about the interaction between gluons and quarks, in a collinear framework that offers cleaner access than previous measurements. The asymmetries also constitute the first ever signal sensitive to the helicity-dependent two-pion fragmentation function G(1)(perpendicular to). A clear sign change is observed around the rho mass that appears in model calculations and is indicative of the dependence of the produced pions on the helicity of the fragmenting quark.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
