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Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
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Lattice QCD Constraints on the Parton Distribution Functions of ^{3}He
William Detmold1, Marc Illa2, David J Murphy1
1Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Physical Review Letters
|June 10, 2021
Summary
Lattice quantum chromodynamics (QCD) calculations determined the momentum fraction carried by u and d quarks in helium-3 nuclei for the first time. Results align with nucleon data, showing potential for precise nuclear parton distribution studies and understanding the EMC effect.
Area of Science:
- Nuclear Physics
- Quantum Chromodynamics (QCD)
- Particle Physics
Background:
- Understanding the distribution of momentum carried by quarks and gluons within atomic nuclei is crucial for comprehending nuclear structure and interactions.
- The EMC effect, a phenomenon where parton distribution functions (PDFs) in nuclei differ from those in free nucleons, remains a significant puzzle in nuclear physics.
- Lattice QCD provides a first-principles approach to studying the strong force, but calculations for light nuclei are computationally demanding.
Purpose of the Study:
- To determine, for the first time, the fraction of longitudinal momentum in helium-3 ($^{3}$He) carried by the isovector combination of up (u) and down (d) quarks using lattice QCD.
- To compare the momentum fraction in $^{3}$He with that in constituent nucleons to test theoretical models and nuclear parton distribution functions (nPDFs).
- To assess the potential of lattice QCD calculations for refining nPDFs and elucidating the QCD origins of the EMC effect.
Main Methods:
- Employed lattice quantum chromodynamics (QCD) calculations to simulate the behavior of quarks and gluons within the $^{3}$He nucleus.
- Calculated the isovector combination of u and d quark longitudinal momentum fractions.
- Performed calculations with unphysically large quark masses (corresponding to pion mass $m_{π}∼800$ MeV) and extrapolated results towards physical quark masses.
Main Results:
- The fraction of longitudinal momentum carried by the isovector combination of u and d quarks in $^{3}$He was found to be consistent with that in constituent nucleons at the few-percent level.
- This lattice QCD constraint, even with unphysical quark masses, is more precise than current global nuclear parton distribution function fits.
- The results are consistent with determinations from the nnnpdf framework, validating the lattice approach.
Conclusions:
- Lattice QCD calculations of light nuclei offer a powerful, first-principles method for precise determinations of nuclear parton distributions.
- The study demonstrates the imminent potential of lattice QCD to provide crucial insights into the QCD origins of the EMC effect.
- Future lattice calculations will enable more accurate mapping of the internal structure of light nuclei and their constituent partons.
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