May 13 – 19, 2018
Venice, Italy
Europe/Zurich timezone
The organisers warmly thank all participants for such a lively QM2018! See you in China in 2019!

A Quasiparticle Transport Explanation for Collectivity in the Smallest of Collision Systems ($p+p$ and $e^+e^-$)

May 14, 2018, 4:50 PM
Sala Mosaici-1, 3rd Floor (Palazzo del Casinò)

Sala Mosaici-1, 3rd Floor

Palazzo del Casinò

Parallel Talk Collectivity in small systems Collectivity in small systems


James Lawrence Nagle (University of Colorado Boulder)


Experimental evidence suggests that collectivity in asymmetric small systems ($p$, $d$, $^{3}$He+A) is directly related to the initial collision geometry. Therefore, a compelling question is whether the same argument can be extended to p+p, and even $e^+e^-$ collisions. We have modified A-Multiphase-Transport-Model (AMPT) to include the constituent quark structure of the proton. We find with very modest parton-parton cross sections a good description of the triangular and elliptic flow coefficients measured by ATLAS and CMS in p+p collisions, as a function of multiplicity and transverse momentum. We assess the non-flow separation techniques used by these experiments, by implementing their exact methods and comparing the result with the true flow relative to initial geometry in the model. The default AMPT model imposes formation times for partons which are much shorter than their respective de Broglie wavelength, at odds with a central assumption of semi-classical kinetic theory. This challenges the idea of modeling the QGP as well-defined quasi-particles undergoing Boltzmann evolution. We explore the impact on collectivity of enforcing a minimum de Broglie wavelength criterion, and find that it is significant for these smallest of systems. Lastly, we explore the minimal requirements for collectivity within this transport framework to determine whether the multiplicity and geometry of $e^+e^-$ collisions is sufficient to generate experimentally verifiable signals.

Centralised submission by Collaboration Presenter name already specified
Content type Theory

Primary authors

Mr Javier Orjuela-Koop (University of Colorado Boulder) James Lawrence Nagle (University of Colorado Boulder)

Presentation materials