Physics Letters B 747 (2015) 135–138
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Hydrodynamic modeling of
3
He–Au collisions at
√
s
NN
= 200 GeV
Piotr Bo ˙zek
a,∗
, Wojciech Broniowski
b,c
a
AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, 30-059 Kraków, Poland
b
The H. Niewodnicza´nski Institute of Nuclear Physics, Polish Academy of Sciences, 31-342 Kraków, Poland
c
Institute of Physics, Jan Kochanowski University, 25-406 Kielce, Poland
a r t i c l e i n f o a b s t r a c t
Article history:
Received
9 March 2015
Received
in revised form 20 May 2015
Accepted
27 May 2015
Available
online 29 May 2015
Editor:
J.-P. Blaizot
Keywords:
Ultrarelativistic
3
He–Au collisions
Event-by-event
fluctuations
Collective
flow
Femtoscopy
Collective flow and femtoscopy in ultrarelativistic
3
He–Au collisions are investigated within the
3 + 1-dimensional (3 + 1D) viscous event-by-event hydrodynamics. We evaluate elliptic and triangular
flow coefficients as functions of the transverse momentum. We find the typical long-range ridge struc-
tures
in the two-particle correlations in the relative azimuth and pseudorapidity, in the pseudorapidity
directions of both Au and
3
He. We also make predictions for the pionic interferometric radii, which de-
crease
with the transverse momentum of the pion pair. All features found hint on collectivity of the
dynamics of the system formed in
3
He–Au collisions, with hydrodynamics leading to quantitative agree-
ment
with the up-to-now released data.
© 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
1. Introduction
The recent experimental [1–4] and theoretical [5–16] interest
in
ultrarelativistic heavy–light nuclear collisions originates from
expectations that studies of such system may shed light on mecha-
nisms
governing the formation of long-range correlations, and thus
reveal information on dynamics in the earliest phases of the reac-
tion.
A successful scenario for heavy–light collisions explored in
this paper involves, exactly as in the well understood case of two
heavy ion collisions, collective dynamics (hydrodynamics, trans-
port
models). Collectivity provides in a natural way the shape–
flow
transmutation: the deformation of the initial configuration
(ellipticity, triangularity, etc.) is transformed event-by-event into
harmonic flow at freeze-out. Moreover, the approximate transla-
tional
symmetry on the initial transverse shape along the spatial
rapidity direction leads to collimated flow, producing the famous
ridge structures, i.e., azimuthal correlations between particles with
a large pseudorapidity separation. Yet another vivid feature of col-
lectivity
is the mass ordering of various observables [11,12] seen
in proton–nucleus collisions [17].
The
azimuthal deformation of the fireball in small systems is
due to random fluctuations, as in p–Pb collisions, or to a combi-
*
Corresponding author.
E-mail
addresses: Piotr.Bozek@fis.agh.edu.pl (P. Bo ˙zek),
Wojciech.Broniowski@ifj.edu.pl (W. Broniowski).
nation of fluctuations and the intrinsic deformation of the small
projectile, as in d–Au collisions, where the large intrinsic separa-
tion
between the proton and neutron leads to large elliptic flow,
predicted in [5] and verified experimentally in [4]. Moreover, colli-
sions
involving projectiles with an intrinsic triangular deformation,
such
3
He–Au [13] or
12
C–Au [18], are particularly interesting, as
they probe systems with nontrivial projectile geometry.
In this paper we analyze in detail the predictions of 3 +1D vis-
cous
hydrodynamics of Ref. [19] for
3
He–Au collisions at
√
s
NN
=
200 GeV, the reaction currently analyzed at RHIC. In a previous
paper [20] we have proposed specific tests of collectivity, based on
ratios of flow coefficients evaluated with 4- and 2-particle cumu-
lants.
In the present work we focus on other, more direct and im-
mediately
accessible aspects of the reaction, namely, on the elliptic
and triangular flow coefficients, v
2
and v
3
, and the femtoscopic
radii. We also explore the ridge formation, both on the
3
He-side
and Au-side in the pseudorapidity direction. A comparison to pre-
liminary
flow data from the PHENIX Collaboration [21] indicates
a successful description of the reaction within our approach. We
also confirm the very recent findings of Romatschke [22] for the
flow coefficients and the interferometric radii. Our results are sim-
ilar
to results for v
2
and v
3
from hydrodynamical simulations with
IP-Glasma initial conditions [23].
Throughout this paper we use the three-phase approach, con-
sisting
of 1) the Glauber [24] Monte Carlo simulations of the initial
state with GLISSANDO [25], the intermediate 3 +1D event-by-event
http://dx.doi.org/10.1016/j.physletb.2015.05.068
0370-2693/
© 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by
SCOAP
3
.
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