Related Experiment Video
Updated: Aug 9, 2026
09:00
Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser
Published on: June 28, 2018
Spin-dependent structure functions in nuclear matter and the polarized EMC effect
I C Cloët1, W Bentz, A W Thomas
1Special Research Centre for the Subatomic Structure of Matter and Department of Physics and Mathematical Physics, University of Adelaide, South Australia 5005, Australia. icloet@physics.adelaide.edu.au
Physical Review Letters
|August 11, 2005
Summary
A modified Nambu--Jona-Lasinio model accurately describes quark distributions and structure functions. The model reproduces the European Muon Collaboration (EMC) effect and shows nuclear matter significantly quenches spin-dependent structure functions.
Area of Science:
- Nuclear Physics
- Quantum Chromodynamics
- Particle Physics
Background:
- Understanding nucleon structure functions is crucial in quantum chromodynamics.
- Nuclear medium effects on these functions are experimentally observed (e.g., EMC effect).
- Theoretical models are needed to explain these modifications.
Purpose of the Study:
- To investigate nuclear medium modifications of spin-independent and spin-dependent quark distributions and structure functions.
- To utilize a modified Nambu--Jona-Lasinio model incorporating confinement.
- To compare theoretical predictions with experimental data, including the EMC effect and spin-dependent ratios.
Main Methods:
- Employed a modified Nambu--Jona-Lasinio model that avoids unphysical thresholds for nucleon decay.
- Investigated nuclear medium modifications to structure functions within this model.
- Calculated nuclear matter saturation and the F2N(A)/F2N ratio.
- Determined the spin-dependent structure function ratio g1p(A)/g1p.
Main Results:
- The model successfully reproduces nuclear matter saturation and the European Muon Collaboration (EMC) effect.
- The ratio g1p(A)/g1p was found to differ significantly from unity.
- Nuclear medium quenching for spin-dependent structure functions is approximately twice that of the spin-independent case.
Conclusions:
- The modified Nambu--Jona-Lasinio model provides an excellent description of quark distributions and structure functions.
- The significant quenching of spin-dependent structure functions by the nuclear medium is a key finding.
- Experimental confirmation of these results will offer profound insights into the quark structure of nuclear matter.
Related Concept Videos
01:08Atomic Nuclei: Nuclear Spin
All atomic particles possess an intrinsic angular momentum, or 'spin'. Electrons, protons, and neutrons each have a spin value of ½, although protons and neutrons in nuclei may have higher half-integer spins owing to energetic factors.
Atomic nuclei have a net nuclear spin, , which can have an integer or half-integer value. In atomic nuclei, the spins of protons are paired against each other but not with neutrons, and vice versa. Consequently, an even number of protons does not contribute to...
Atomic nuclei have a net nuclear spin, , which can have an integer or half-integer value. In atomic nuclei, the spins of protons are paired against each other but not with neutrons, and vice versa. Consequently, an even number of protons does not contribute to...
00:59Atomic Nuclei: Nuclear Magnetic Moment
All atomic nuclei are positively charged. When they have a nonzero spin, they behave like rotating charges. As a consequence of their charge and spin, these nuclei generate a magnetic field (B). This, in turn, gives rise to a magnetic moment (μ), which is randomly oriented in the absence of an external magnetic field. When an external magnetic field (B0) is applied, the magnetic moment vectors can align with the field or against it in 2 + 1 orientations. A hydrogen nucleus, which is just a...
01:03Atomic Nuclei: Nuclear Spin State Overview
NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of one, the...
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
01:23Atomic Nuclei: Nuclear Relaxation Processes
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis. This...
01:29Potential Due to a Polarized Object
A neutral atom consists of a positively charged nucleus surrounded by a negatively charged electron cloud. When placed in an external electric field, the external electric force pulls the electrons and nucleus apart, opposite to the intrinsic attraction between the nucleus and the electrons. The opposing forces balance each other with a slight shift between the center of masses of the nucleus and the electron cloud, resulting in a polarized atom. On the other hand, a few molecules, like water,...