Observation of the D1(2420)-->Dpi + pi- decays

Area of Science:

• High Energy Physics
• Particle Physics
• Quantum Chromodynamics

Background:

• Understanding the properties of heavy mesons is crucial for testing Quantum Chromodynamics.
• The D0/1(2420) and D+/1(2420) are excited states of charm mesons that require further experimental investigation.

Purpose of the Study:

• To report the first observation of specific decay modes for the D0/1(2420) and D+/1(2420) resonances.
• To exclude contributions from known dominant decay modes to isolate the observed phenomena.
• To set upper limits on branching fractions for related decays.

Main Methods:

• Analysis of 15.2 x 10^7 B-Bbar events collected by the Belle detector at the KEKB collider.
• Selection of B- --> D0/1(2420)pi- and B0 --> D+/1(2420)pi- decay channels.
• Exclusion of the dominant D1 --> D*pi decay mode contribution.

Main Results:

• First observation of D0/1(2420) --> D0pi-pi+ and D+/1(2420) --> D+pi-pi+ decays.
• Setting 90% confidence level upper limits for four other decay modes, including those involving D(*0)2(2460) and D(*+)2(2460) states.

Conclusions:

• The observed decays provide new insights into the spectroscopy of excited charm mesons.
• These results contribute to a more comprehensive understanding of heavy meson decay mechanisms.
• Further studies are warranted to fully characterize these resonances and their decay properties.