The Study of Strange Sea Quarks’ Contribution to The Nucleon Spin A.J Parker & Fatiha Benmokhtar Ph.D I. Introduction Nucleons are composed of constituents known as quarks and leptons. Valence Quarks only contribute a little bit to the overall spin of the nucleon. It has been theorized that virtual sea quarks are in large part responsible for the overall spin of the nucleon. The question is how much do the virtual sea strange quarks contribute to the overall spin? In order to prove this theory, Semi-Inclusive Deep Inelastic Scattering (SIDIS) was employed to probe the inside of deuterons using electrons in order to study particle jets such as kaons. This will be achieved by using a Ring Imaging Cherenkov (RICH) detector for particle separations. IV. Data Analysis II. Background V. Future Direction VI. Acknowledgements As for the path of the experiment, JLab continues to synthesize data acquired by CLAS12’s RICH detector to analyze and determine the identity of the particles. CLAS12 is in the process of being enhanced to have more RICH detectors to have greater precise measurements. I would like to thank my mentor Dr. Fatiha Benmokhtar, the Physics Department, and the Undergraduate Research Program for allowing me to participate in this research. I would also like to acknowledge the Thomas Jefferson National Accelerator Facility. Figure 6: CLAS12 spectrometer system. Figure 4: Simplified schematic diagram of semi-inclusive deep inelastic scattering. = = 2 2 = =− ′ 2 = 2 + 2 + 2 2 = − 2 = 4 ′ sin 2 ( 2 ) Figure 2: Internal Structure of a deuteron nucleus. Figure 3: Quark composition of kaons. Kaon K + Kaon K 0 Kaon K - Anti- Kaon ഥ Figure 7: Jlab’s Experimental Hall B . Figure 9: Jlab’s CLAS12 spectrometer components. III. Approach Figure 13: The Strange-parton distribution xS(x,Q) from the measured Hermes multiplicity for charged kaons evolved to Q=2.5 GeV assuming [ (, ] − = 1.27 Figure 12: Statistical projections for the Isoscalar method measurement of x∆S(x) Deep inelastic scattering is the collision between an electron and a nucleon or nucleus by exchange of a virtual photon. Figure 8: The array of 391 Multi- Anode Photomultiplier Tubes. Figure 5: Deep Inelastic Scattering Kinematics. Figure 9: Deuteron program proposed by the E12-09-007 Experiment in CLAS12 at Jefferson Lab. *F. Benmokhtar, spokesperson. Antiparallel Orientation Parallel Orientation ൗ 3 2 ~ − + = ൗ 3 2 ൗ 1 2 ~ + + = ൗ 1 2 = + () ∆ = + () Quark parton distribution Quark helicity distribution The detection efficiency of the RICH detector is approximately 80% for kaons with momenta from 3 to 8 GeV.