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

  • Author(s): Adam, J;
  • Adamová, D;
  • Aggarwal, MM;
  • Aglieri Rinella, G;
  • Agnello, M;
  • Agrawal, N;
  • Ahammed, Z;
  • Ahmad, S;
  • Ahn, SU;
  • Aiola, S;
  • Akindinov, A;
  • Alam, SN;
  • Albuquerque, DSD;
  • Aleksandrov, D;
  • Alessandro, B;
  • Alexandre, D;
  • Alfaro Molina, R;
  • Alici, A;
  • Alkin, A;
  • Alme, J;
  • Alt, T;
  • Altinpinar, S;
  • Altsybeev, I;
  • Alves Garcia Prado, C;
  • An, M;
  • Andrei, C;
  • Andrews, HA;
  • Andronic, A;
  • Anguelov, V;
  • Anson, C;
  • Antičić, T;
  • Antinori, F;
  • Antonioli, P;
  • Aphecetche, L;
  • Appelshäuser, H;
  • Arcelli, S;
  • Arnaldi, R;
  • Arnold, OW;
  • Arsene, IC;
  • Arslandok, M;
  • Audurier, B;
  • Augustinus, A;
  • Averbeck, R;
  • Azmi, MD;
  • Badalà, A;
  • Baek, YW;
  • Bagnasco, S;
  • Bailhache, R;
  • Bala, R;
  • Balasubramanian, S;
  • Baldisseri, A;
  • Baral, RC;
  • Barbano, AM;
  • Barbera, R;
  • Barile, F;
  • Barnaföldi, GG;
  • Barnby, LS;
  • Barret, V;
  • Bartalini, P;
  • Barth, K;
  • Bartke, J;
  • Bartsch, E;
  • Basile, M;
  • Bastid, N;
  • Basu, S;
  • Bathen, B;
  • Batigne, G;
  • Batista Camejo, A;
  • Batyunya, B;
  • Batzing, PC;
  • Bearden, IG;
  • Beck, H;
  • Bedda, C;
  • Behera, NK;
  • Belikov, I;
  • Bellini, F;
  • Bello Martinez, H;
  • Bellwied, R;
  • Belmont-Moreno, E;
  • Beltran, LGE;
  • Belyaev, V;
  • Bencedi, G;
  • Beole, S;
  • Berceanu, I;
  • Bercuci, A;
  • Berdnikov, Y;
  • Berenyi, D;
  • Bertens, RA;
  • Berzano, D;
  • Betev, L;
  • Bhasin, A;
  • Bhat, IR;
  • Bhati, AK;
  • Bhattacharjee, B;
  • Bhom, J;
  • Bianchi, L;
  • Bianchi, N;
  • Bianchin, C;
  • Bielčík, J;
  • Bielčíková, J
  • et al.
Abstract

We present measurements of two-particle correlations with neutral pion trigger particles of transverse momenta 8>pTtrig>16 GeV/c and associated charged particles of 0.5>pTassoc>10 GeV/c versus the azimuthal angle difference Δφ at midrapidity in pp and central Pb–Pb collisions at sNN=2.76 TeV with ALICE. The new measurements exploit associated charged hadrons down to 0.5 GeV/c, which significantly extends our previous measurement that only used charged hadrons above 3 GeV/c. After subtracting the contributions of the flow background, v2 to v5, the per-trigger yields are extracted for |Δφ|>0.7 on the near and for |Δφ−π|>1.1 on the away side. The ratio of per-trigger yields in Pb–Pb to those in pp collisions, IAA, is measured on the near and away side for the 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≈0.6 for pTassoc<3 GeV/c, while with decreasing momenta an enhancement develops reaching about 5 at low pTassoc. On the near side, an enhancement of IAA between 1.2 at the highest to 1.8 at the lowest pTassoc 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 pTassoc. Only AMPT captures the enhancement at low pTassoc, both on the near and away side. However, it also underpredicts IAA above 5 GeV/c, in particular on the near-side.

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