Charge symmetry breaking in np-->dpi(0)

Area of Science:

• Nuclear Physics
• Particle Physics
• Quantum Chromodynamics

Background:

• Charge symmetry is a fundamental symmetry in nuclear physics, predicting certain reaction outcomes.
• The forward-backward asymmetry in np-->dp pi(0) is a sensitive probe of charge symmetry violation.
• Previous measurements and theoretical calculations provide context for this study.

Purpose of the Study:

• To precisely measure the forward-backward asymmetry in the np-->dp pi(0) reaction.
• To test the predictions of charge symmetry in the strong interaction.
• To provide experimental data for refining chiral effective field theory calculations and probing fundamental quark properties.

Main Methods:

• Experimental measurement of the np-->dp pi(0) reaction at a specific incident neutron energy.
• Utilizing particle detectors to identify and measure the momenta of the outgoing deuteron and pion.
• Statistical and systematic error analysis to ensure measurement accuracy.

Main Results:

• The forward-backward asymmetry was measured to be (17.2 ± 8.0 (stat) ± 5.5 (syst)) x 10^-4 at 279.5 MeV incident neutron energy.
• This non-zero value indicates a violation of charge symmetry in this reaction.
• The experimental result was compared with recent chiral effective field theory calculations.

Conclusions:

• The measured forward-backward asymmetry provides evidence for charge symmetry violation in the np-->dp pi(0) reaction.
• The findings have implications for the theoretical understanding of the up and down quark mass difference.
• This experiment contributes to the ongoing effort to precisely determine fundamental parameters of the Standard Model.