Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/88152
Type: Artigo de periódico
Title: Origin Of Long-range Azimuthal Correlations In Hadronic Collisions
Author: Torrieri G.
Abstract: I review the models suggested to date as an explanation for the so-called "ridge" phenomenon: an elongation in rapidity of two-particle correlations seen at energies of the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider. I argue that these models can be divided into two phenomenologically distinct classes: "Hotspot+flow"-driven correlations, where initial-state correlations created by structures local in configuration space are collimated by transverse flow, and models where the azimuthal correlation is created through local partonic interactions in a high-gluon-density initial state. I argue that the measurement of a strong double ridge in pA and dA collisions allows a good opportunity to understand the ridge's origin because it allows us to see if a common Knudsen number scaling, which is expected if the ridge has a hydrodynamic origin, can be used to understand all data. I show that current data present evidence that this scaling is lacking, which presents a challenge to the hydrodynamic models. On the other hand, particle-identified correlations are a particularly promising way of testing the assumption that distinguishes the two models; namely, of whether the correlation is formed initially in the partonic phase, or as a final-state effect. Assuming fragmentation occurs "as in vacuum" can be used to predict scaling trends which are generally broken by models, such as hydrodynamics, where the ridge is created as a final-state effect. While evidence is again not fully conclusive, data do seem to follow a scaling compatible with hydrodynamics [Phys. Rev. Lett. 111, 172303 (2013)PRLTAO0031- 900710.1103/PhysRevLett.111.172303]. I close by discussing experimental observables capable of clarifying the situation. © 2014 American Physical Society.
Editor: 
Rights: aberto
Identifier DOI: 10.1103/PhysRevC.89.024908
Address: http://www.scopus.com/inward/record.url?eid=2-s2.0-84897795411&partnerID=40&md5=6131ac92fc28065063e8bcb912b59faa
Date Issue: 2014
Appears in Collections:Unicamp - Artigos e Outros Documentos

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