Abstract
The ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high-transverse momentum trigger hadron in p–Pb collisions at sNN=5.02 TeV. Jets are reconstructed from charged-particle tracks using the anti-kT algorithm with resolution parameter R=0.2 and 0.4. A data-driven statistical approach is used to correct the uncorrelated background jet yield. Recoil jet distributions are reported for jet transverse momentum 15<pT,jetch<50GeV/c and are compared in various intervals of p–Pb event activity, based on charged-particle multiplicity and zero-degree neutral energy in the forward (Pb-going) direction. The semi-inclusive observable is self-normalized and such comparisons do not require the interpretation of p–Pb event activity in terms of collision geometry, in contrast to inclusive jet observables. These measurements provide new constraints on the magnitude of jet quenching in small systems at the LHC. In p–Pb collisions with high event activity, the average medium-induced out-of-cone energy transport for jets with R=0.4 and 15<pT,jetch<50GeV/c is measured to be less than 0.4 GeV/c at 90% confidence, which is over an order of magnitude smaller than a similar measurement for central Pb–Pb collisions at sNN=2.76TeV. Comparison is made to theoretical calculations of jet quenching in small systems, and to inclusive jet measurements in p–Pb collisions selected by event activity at the LHC and in d–Au collisions at RHIC.
Highlights
The collision of heavy nuclei at high energies generates a Quark–Gluon Plasma (QGP), a dense, highly inviscid, stronglycoupled fluid governed by sub-nucleonic degrees of freedom [1]
We have reported measurements of the semi-inclusive distribution of charged in p–Pb collisions ajtet√s srNeNco=ili5n.g02frToemV, a high-pT hadron trigger selected by event activity in forward (Pb-going) charged multiplicity and zero-degree neutral energy
It provides a new probe of jet quenching in p–Pb collisions that is systematically different from quenching measurements based on inclusive jet production
Summary
The collision of heavy nuclei at high energies generates a Quark–Gluon Plasma (QGP), a dense, highly inviscid, stronglycoupled fluid governed by sub-nucleonic degrees of freedom [1]. Current understanding of the properties of the QGP is based primarily on two phenomena observed in high energy nuclear collisions and their comparison to theoretical calculations: strong collective flow [2], and jet quenching, which arises from interaction of energetic jets with the medium [3]. Turbative QCD (pQCD) are in excellent agreement over a broad kinematic range with jet measurements in pp collisions at the Large Hadron Collider (LHC) [4,5,6,7]. Measurements in pp collisions of charged-particle jets, which consist of the charged component of the hadronic jet shower, are well-described by QCD-based Monte Carlo calculations [8,9]
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