A1 Journal article (refereed)
Direct observation of the dead-cone effect in quantum chromodynamics (2022)

ALICE Collaboration. (2022). Direct observation of the dead-cone effect in quantum chromodynamics. Nature, 605(7910), 440-446. https://doi.org/10.1038/s41586-022-04572-w

JYU authors or editors

Publication details

All authors or editors: ALICE Collaboration

Journal or series: Nature

ISSN: 0028-0836

eISSN: 1476-4687

Publication year: 2022

Publication date: 18/05/2022

Volume: 605

Issue number: 7910

Pages range: 440-446

Publisher: Nature Publishing Group

Publication country: United Kingdom

Publication language: English

DOI: https://doi.org/10.1038/s41586-022-04572-w

Publication open access: Openly available

Publication channel open access: Partially open access channel

Publication is parallel published (JYX): https://jyx.jyu.fi/handle/123456789/82673

Publication is parallel published: https://arxiv.org/abs/2106.05713

Additional information: Publisher Correction: https://doi.org/10.1038/s41586-022-05026-z

Abstract

In particle collider experiments, elementary particle interactions with large momentum transfer produce quarks and gluons (known as partons) whose evolution is governed by the strong force, as described by the theory of quantum chromodynamics (QCD)1. These partons subsequently emit further partons in a process that can be described as a parton shower2, which culminates in the formation of detectable hadrons. Studying the pattern of the parton shower is one of the key experimental tools for testing QCD. This pattern is expected to depend on the mass of the initiating parton, through a phenomenon known as the dead-cone effect, which predicts a suppression of the gluon spectrum emitted by a heavy quark of mass mQ and energy E, within a cone of angular size mQ/E around the emitter3. Previously, a direct observation of the dead-cone effect in QCD had not been possible, owing to the challenge of reconstructing the cascading quarks and gluons from the experimentally accessible hadrons. We report the direct observation of the QCD dead cone by using new iterative declustering techniques4,5 to reconstruct the parton shower of charm quarks. This result confirms a fundamental feature of QCD. Furthermore, the measurement of a dead-cone angle constitutes a direct experimental observation of the non-zero mass of the charm quark, which is a fundamental constant in the standard model of particle physics.

Keywords: particle physics; quantum chromodynamics; quarks

Contributing organizations

Ministry reporting: Yes

Reporting Year: 2022

JUFO rating: 3