Importance of d-wave contributions in the charge symmetry breaking reaction $dd\to {}^4\text{He}{\pi }^0$

Abstract

This letter reports a first quantitative analysis of the contribution of higher partial waves in the charge symmetry breaking reaction $dd\to {}^4\text{He}{\pi }^0$ using the WASA-at-COSY detector setup at an excess energy of $Q=60$ MeV. The determined differential cross section can be parametrized as $\text{d}\sigma /\text{d}\Omega =a+b{\cos }^2{\theta }^{\ast }$, where ${\theta }^{\ast }$ is the production angle of the pion in the center-of-mass coordinate system, and the results for the parameters are $a=\left(1.55\pm 0.46(\text{stat}{)}_{-0.8}^{+0.32}(\text{syst})\right)$ pb/sr and $b=\left(13.1\pm 2.1(\text{stat}{)}_{-2.7}^{+1.0}(\text{syst})\right)$ pb/sr. The data are compatible with vanishing p-waves and a sizable d-wave contribution. This finding should strongly constrain the contribution of the $\Delta$ isobar to the $dd\to {}^4\text{He}{\pi }^0$ reaction and is, therefore, crucial for a quantitative understanding of quark mass effects in nuclear production reactions.

arXiv comment5 figures

References in corpus (19)

• The ratios of the light quark masses
• Meson production in nucleon--nucleon collisions close to the threshold
• Charge Symmetry Breaking and QCD
• Observation of the Charge Symmetry Breaking d + d -> 4He + pi0 Reaction Near Threshold
• Role of the $\Delta$ isobar in the reaction $NN\to NN\pi$ near threshold
• Charge symmetry breaking in n p --> d pi^0
• Near threshold eta meson production in the d+d->alpha+eta reaction
• Survey of charge symmetry breaking operators for dd -> alpha pi0
• Extraction of the strong neutron-proton mass difference from the charge symmetry breaking in pn-->d pi0
• p-Wave pion production from nucleon-nucleon collisions
• Comment on "Role of heavy meson exchange in near threshold N N --> d pi"
• Realistic Few-Body Physics in the $dd\to \alpha {\pi }^0$ Reaction
• Effective Field Theory calculations of $NN\to NN\pi$
• Pion production in nucleon-nucleon collisions in chiral effective field theory with Delta(1232)-degrees of freedom
• Nucleon-nucleon charge symmetry breaking and the dd -> alpha pi0 reaction
• Initial-State Coulomb Interaction in the dd -> alpha pi^0 Reaction
• Charge Symmetry Breaking in dd->4Heπ0 with WASA-at-COSY
• Threshold pion production in proton-proton collisions at NNLO in chiral EFT
• Investigation of the dd -> 3He n π0 reaction with the FZ Jülich WASA-at-COSY facility

Cited by in corpus (2)

• Pion absorption from the lowest atomic orbital in 2H, 3H and 3He
• Ernest Henley's Isospin and the Ensuing Progress