Journal Article Jet-like correlations with neutral pion triggers in pp and central Pb–Pb collisions at 2.76 TeV

ALICE Collaboration  ,  Busch, O  ,  Chujo, T.  ,  Esumi, S.  ,  Miake, Y.

763pp.238 - 250 , 2016-12 , Elsevier B.V.
ISSN:0370-2693
NCID:AA00774026
Description
We present measurements of two-particle correlations with neutral pion trigger particles of transverse momenta View the MathML source8<pTtrig<16 GeV/c and associated charged particles of View the MathML source0.5<pTassoc<10 GeV/c versus the azimuthal angle difference Δφ at midrapidity in pp and central Pb–Pb collisions at View the MathML sourcesNN=2.76 TeV with ALICE. The new measurements exploit associated charged hadrons down to 0.5 GeV/c0.5 GeV/c, which significantly extends our previous measurement that only used charged hadrons above 3 GeV/c3 GeV/c. After subtracting the contributions of the flow background, v2v2 to v5v5, the per-trigger yields are extracted for |Δφ|<0.7|Δφ|<0.7 on the near and for |Δφ−π|<1.1|Δφ−π|<1.1 on the away side. The ratio of per-trigger yields in Pb–Pb to those in pp collisions, IAAIAA, is measured on the near and away side for the 0–10%0–10% most central Pb–Pb collisions. On the away side, the per-trigger yields in Pb–Pb are strongly suppressed to the level of IAA≈0.6IAA≈0.6 for View the MathML sourcepTassoc>3 GeV/c, while with decreasing momenta an enhancement develops reaching about 5 at low View the MathML sourcepTassoc. On the near side, an enhancement of IAAIAA between 1.2 at the highest to 1.8 at the lowest View the MathML sourcepTassoc is observed. The data are compared to parton-energy-loss predictions of the JEWEL and AMPT event generators, as well as to a perturbative QCD calculation with medium-modified fragmentation functions. All calculations qualitatively describe the away-side suppression at high View the MathML sourcepTassoc. Only AMPT captures the enhancement at low View the MathML sourcepTassoc, both on the near and away side. However, it also underpredicts IAAIAA above 5 GeV/c5 GeV/c, in particular on the near-side.
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