Direct observation of the dead-cone effect in quantum chromodynamics

S. Acharya, J. Adolfsson, S. Basu, P. Christiansen, O. Matonoha, A.F. Nassirpour, A. Ohlson, A. Oskarsson, T. Richert, O.V. Rueda, D. Silvermyr, N. Zurlo, ALICE Collaboration

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskriftPeer review


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. © 2022, The Author(s).
Sidor (från-till)440-446
Antal sidor7
StatusPublished - 2022

Bibliografisk information

Number of authors = 1026

EID = 85130231262

Start page = 440

End page = 446

Affiliation = Acharya, S., Variable Energy Cyclotron Centre, Homi Bhabha National Institute, Kolkata, India

Affiliation = Zurlo, N., INFN, Sezione di Pavia, Pavia, Italy, Universita di Brescia, Brescia, Italy

Affiliation = ALICE Collaboration

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