Gluonic superfluid in high energy p-pb collisions Chris Zin Derek Everett, Sean Gavin, AbhijitMajumder Graduate Research Day Wayne State University
Quark-gluon plasma State of matter consisting of free quarks and gluons Requires extremely high temperature and/or density Above 175 MeV (~2 trillion kelvin) 100,000 times hotter than the sun
Where can we find QGP? Early universe At the center of dense stars http://www.universetoday.com/15306/
Heavy-ion collisions Particle colliders RHIC and LHC Initial approach Collision Quark-gluon plasma Freeze-out https://str.llnl.gov/str/janfeb03/gifs/soltz3.jpg Phase transition Hydrodynamic expansion
Studying QGP is difficult! No access to the early universe or the centers of stars Collider produced QGP is too short lived to study directly System lifetime is ~10 fm/c (~3.3*10-24 seconds) So how do we study it? We use indirect methods - study what comes out Compare with pp and pa experiments Compare with theory
Radial and elliptic flow The system does not have to expand uniformly To study the shape of the expansion we expand the distribution function into Fourier components: Elliptic flow is characterized by v 2 http://qcdmof.cns.s.u-tokyo.ac.jp/index.php?quark%20gluon%20plasma
PbPb vs ppb Relatively large v 2 was viewed as characteristic of larger collision systems Provides some of the strongest evidence for QGP It was not expected in smaller systems Not enough produced particles to develop flow Not enough time to develop flow The origin of this effect is under debate http://arxiv.org/pdf/1406.2474v2.pdf
Initial state with high gluon occupation High energy nucleons contain a large number of low momentum gluons When these nucleons collide the gluons fuse and occupy the lowest momentum modes These modes are macroscopically occupied This forms a dense superfluid Bose-Einstein condensate (supergluid ) http://arxiv.org/pdf/1111.5452.pdf
Superfluidity A state of matter having nearly zero viscosity Liquid helium below 2.17 K Wikipedia: Superfluidity Can flow without losing energy to friction Difficult to create excitations This can lead to strange effects Rollin film Fountain effect YouTube: Alfred Leitner Liquid Helium II the Superfluid
Can it flow? The superfluid cannot dissipate immediately There is a mass gap to higher modes Allows time for expansion (possibly develop flow pattern) Excitations in the fluid eventually cause dissipation The excitations start interacting and make QGP The system can then proceed with a head start on flow
Model of the condensate Start with a charged scalar Lagrangian Substitute amplitude and phase to describe superfluid Include small fluctuations above the background condensate Density and velocity of superfluid
Model of the condensate Factor the Lagrangian according to the order of the fluctuations Zeroth order describes the condensate Dense phase we treat this classically Classical equations of motion
Model of the condensate Second order and higher describes interaction of the excitations with the condensate and other excitations These form a dilute phase and must be treated quantumly Mass terms for fluctuations due to interaction with the condensate Note: proportional to ρ 2!
Early simulations They do not include excitations A view of the central transverse slice of the expanding system
Summary We are investigating the possibility of pre-equilibrium flow in high energy ppb collisions caused by a gluonic Bose-Einstein condensate We are using a charged scalar theory A mass gap may allow time for the system to develop flow patterns Early simulations show potential for elliptic flow Much work left to do Include excitations Study mass gap Time range of applicability