The Study of Strange Sea Quarks’ Contribution to

The Nucleon SpinA.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.

𝑦 =𝑣

𝐸

𝑥 =𝑄2

2𝑀𝑣

𝑍 =𝐸𝑘𝑣

𝑦 = 𝐸 − 𝐸′ 𝑊2 = 𝑀2 + 2𝑀𝑣 + 𝑄2

𝑄2 = −𝑞2 = 4𝐸𝐸′ sin2(𝜃

2)

Figure 2: Internal Structure

of a deuteron nucleus. Figure 3: Quark composition

of kaons.

Kaon K+

Kaon K0

Kaon K-

Anti-

Kaon ഥ𝐊𝟎

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 [𝑫𝑺𝑲(𝒛,𝑸𝟐𝒅𝒛]

−𝟏= 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

𝜎 ൗ3 2~𝑞− 𝑥 𝑆𝑦 + 𝑆𝑛 = ൗ3 2𝜎 ൗ1 2

~𝑞+ 𝑥 𝑆𝑦 + 𝑆𝑛 = ൗ1 2

𝑞𝑓 𝑥 = 𝑞𝑓 𝑥 + 𝑞𝑓(𝑥)

∆𝑞𝑓 𝑥 = 𝑞𝑓 𝑥 + 𝑞𝑓(𝑥)

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.