Abstract
We report the first direct measurement of the dead-cone effect at colliders, using iterative jet declustering techniques in pp collisions at s=13TeV. The procedure exposes the splittings of D0 mesons in the jet shower, by iteratively declustering the angular ordered C/A tree. The splitting history of the D0 meson initiated jet is mapped onto the Lund Plane, where appropriate cuts can be made to suppress hadronisation effects. The reported variable is the splitting angle with respect to the D0 meson axis, which is updated after each splitting. Track-based jet finding, along with the low transverse momentum reach for charged tracks of the ALICE detector, allow for an accurate reconstruction of the splitting angle in the phase-space where the dead-cone effect is expected to be largest. The results are compared to those of inclusive jets, where the dead-cone effect is expected to be negligible.
Highlights
The dead-cone effect is a fundamental property of all radiative theories
For illustrative purposes the Lund Planes shown here have ln(kT ) instead of Erad on the y-axis. At this stage already a visual hint of a suppression of splittings at small angles in the D0-tagged jets compared to inclusive ones can been observed
In order to directly observe the dead-cone effect, projections of the angular axis of the D0-tagged jet and inclusive jet Lund Planes were made in bins of Erad
Summary
The dead-cone effect is a fundamental property of all radiative theories. It defines an angle relative to the emitter, within which emissions are parametrically suppressed. The dead-cone region is susceptible to pollution by both the decay products of the heavy quarks (and their subsequent emissions) and hadronisation effects. Another experimental constraint was the accurate determination of the emission axis, as this must be updated after each subsequent emission. One technique involves the statistical separation of radiation emitted from heavy quarks in a 4-body top quark decay [3] Another method [4], which this analysis is based on, allows for the measurement of the dead-cone effect for charm and beauty quarks by taking advantage of Lund Planes [5]
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