Finally, scientists prove the ‘dead cone effect,’ shaking up particle physics

https://www.popularmechanics.com/science/a40432968/dead-cone-effect/

"large mass — along with beauty and top quarks ... large dead cone... isolate charm quark and reconstruct gluon emissions... Comparing this emission pattern to the emissions from lighter quarks and from gluons revealed the dead cone in the charm quark’s emissions. “Our technique found a way not only to isolate the charm quark but measure an effect that is directly sensitive to the mass it has before it binds into a hadron"