Heavy quark initial condition consistent with
soft matter production
Weiyao Ke, J. Scott Moreland & Steffen A. Bass
Department of Physics, Duke University
wk42@phy.duke.edu
Introduction
• Heavy quark observables RAA and v2 are sensitive to HQ interaction with the QGP medium and its evolution.
• In event-by-event calculations, correlations between HQ production vertices and medium inhomogeneities may affect observables.
• This project: develop implementation of HQ production vertices into TRENTo IC generator that is consistent with underlying soft event.
• At LHC energy, hNci and hNchi scale as.
p
dNc dNch 0
T
T
,
∼
C
∼
C
T
(x,
y).
(5)
A
B
AA
dηsd2xT ηs=0
dηsd2xT ηs=0
This ansatz describes the correlation between normalised Nc
and Nch well for both large and small systems.
Soft matter initial condition TRENTo
• TRENTo: effective model of initial entropy deposition in pp,
pA and AA collisions [1].
• Entropy production is mapped from nuclear thickness functions via a generalised mean ansatz,
dS = CTR(TA, TB ; p),
(1)
2
dηsd xT ηs=0

T
T

A
B

,
p
=
−1

1

p

T
+
T
p p
A
B
p
TA + TB
TR =
(2)
=
TATB , p → 0 .

2


TA + TB


, p = +1
2
Key results
• TRENTo v.s. Glauber: charm quark initial correlation with
underlying entropy / entropy gradient of soft matter.
• Most central AA: similar results for both models
• pA and peripheral AA: sub-nucleonic fluctuation dominates
and TRENTo generates more charm quarks in the high entropy
/ entropy gradient region.
• parameter ”p” fitted to experiments (p ≈ 0 at LHC energy and
0.3 for RHIC energy).
• Nuclear thickness function:
participant
TA,B =
X
kiρi(x, y),
(3)
i∈A,B
ki, subjecting to Γ distribution (continuum limit of NBD), incorporate sub-nucleonic fluctuation in pp.
• Compared to two-component MC-Glauber model:
participants
X
α
dS ki (1 − α) + nbc,i ρi(x, y). (4)
∼
2
dηsd xT ηs=0
2
i
Charm quark correlation with underlying entropy and entropy
gradient in Pb+Pb collision in TRENTo and Glauber.
α ≈ 0.14 is the relative contribution of ”hard” component.
Implementation of HQ in initial condition
• Traditionally in MC-Galuber model: production of charm
quark ∝ Nbin; and vertices are spatially deposited at midpoint
of each binary collision.
• Nbin includes fluctuations for nucleon positions, but subnucleonic fluctuations (dominant in small systems) are missing (correlation between ND and Nch in pp).
• In TRENTo: to incorporate both
nucleonic
and
sub-nucleonic
R 2
fluctuations, hNci ∝ σpp→cc̄ d x⊥TAA with spatial sampling
according to fluctuating TAA(x, y).
[1] J. Scott Moreland, Jonah E. Bernhard, and Steffen A. Bass.
arxiv:1412.4708 [nucl-th]. Physical Review C, in printing.
Same as the previous, but for p+Pb.
Forthcoming Research
• Tune TRENTo with experimental observables.
• Perform transport calculation with this consistent Hard + Soft
initial condition.