Isotensor Dibaryon in the pp→ppπ^{+}π^{-} Reaction?

Area of Science:

• Nuclear Physics
• Particle Physics
• Hadron Spectroscopy

Background:

• Investigating the complex dynamics of the quasifree pp→ppπ^{+}π^{-} reaction is crucial for understanding nuclear interactions.
• Existing models based on t-channel meson exchange do not fully reproduce experimental data in the relevant energy region.

Purpose of the Study:

• To precisely measure total and differential cross sections for the pp→ppπ^{+}π^{-} reaction.
• To test theoretical models of N*(1440) and Δ(1232) resonance excitations.
• To explore the existence of exotic dibaryon resonances.

Main Methods:

• Exclusive measurements were performed at WASA@COSY using proton-deuteron (pd) collisions.
• Proton beam energies (T_{p}) ranged from 1.08 to 1.36 GeV.
• Analysis focused on the quasifree pp→ppπ^{+}π^{-} reaction channel.

Main Results:

• Experimental total and differential cross sections were extracted for the specified energy range.
• T-channel meson exchange calculations significantly underpredict the total cross section and disagree with differential cross sections.
• The data indicate the presence of resonance structures not adequately described by standard models.

Conclusions:

• The findings challenge conventional explanations involving N*(1440) and Δ(1232) resonances alone.
• An isotensor ΔN dibaryon resonance with quantum numbers I(J^{P})=2(1^{+}), produced with a pion, is proposed as a necessary component.
• This exotic dibaryon resonance offers a potential explanation for the discrepancies observed in the cross-section measurements.