Exploring the Structure of the Proton via Semi-inclusive Pion Electroproduction
- Univ. of Connecticut, Storrs, CT (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Measurements of the multiplicity, $$cos \phi_h$$ moment, and $$cos 2\phi_h$$ moment of the semi-inclusive deep inelastic scattering (SIDIS) cross-section have been performed. The data set used was the E1-F run from the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson National Lab. The run used a 5.498 GeV longitudinally polarized electron beam and an unpolarized liquid hydrogen target. Both charged pion channels were studied over a broad range of kinematics (0:1 < $$x$$ < 0:6, 1:0 < $Q^2$ < 4:7 GeV2, 0:0 < $$z$$ < 0:9, 0:0 < $$P^2_{h\perp}$$ < 1:0 GeV2, and -180 < $$\phi_h$$ < 180 ). These measurements give access to transverse momentum dependent parton distribution functions (TMDs) which describe the transverse motion of quarks and gluons inside of the proton. Results show evidence of a TMD known as the Boer-Mulders function being non-zero via a flavor dependence on the $$cos \phi_h$$ and $$cos 2\phi_h$$ modulations of the data. A non-zero Boer-Mulders function requires a non-zero quark orbital angular momentum ($$L_q$$) contribution to the proton spin, thus giving insights into the 28 year old puzzle of the missing proton spin.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Nuclear Physics (NP)
- DOE Contract Number:
- AC05-06OR23177
- OSTI ID:
- 1432197
- Report Number(s):
- JLAB-PHY-15-2336; DOE/OR/23177-4400
- Country of Publication:
- United States
- Language:
- English
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