The STAR Collaboration has recently published
“Centrality and transverse momentum dependence of
D0-meson production at mid-rapidity in Au +
Au collisions at √sNN = 200 GeV,”
in Physical
Review C 99, 034908 (2019).
This paper presents a new measurement of D0 meson
production enabled by the Heavy Flavor Tracker (HFT)
high-resolution silicon detector system in Au + Au
collisions at √sNN = 200 GeV. Compared to the previous
measurement with the TPC only, the new data contain
greatly improved precision which allows us to
systematically investigate the D0 meson production in
wide centrality and transverse momentum regions. The
new improved data are expected to further constrain
our understanding of the charm medium interaction as
well as to better determine the medium transport
parameters together with the previous publication on
D0 elliptic flow measurement.
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Left: D0 RCP for different centrality
classes with the 40–60% spectrum as the reference
compared to that of other light and strange mesons (π,
Κs, and φ) as well as the
model calculations. Right:
Integrated D0 cross section per
nucleon-nucleon collision at mid-rapidity
for pT > 0 (a)
and pT > 4 GeV/c (b) as a
function of centrality Npart. The green boxes on the
data points depict the overall normalization
uncertainties in p + p and Au + Au data
respectively.
The nuclear modification factors RCP
of D0 meson are shown in the left
figure, and show significantly suppression at
high pT and the suppression level is
comparable to that of light hadrons
at pT > 5 GeV/c, indicates
that charm quarks lose significant energy when
traversing through the hot QCD medium. Right figure
shows
the pT-integrated D0
production cross section per nucleon-nucleon
collisions in Au + Au collisions together with the
measurement in p + p. The
full-pT integrated cross section in
Au + Au collisions seem to be smaller than that
in p + p collisions by 1.5σ,
indicating that cold nuclear matter effects (CNM)
and/or hadronization through quark coalescence may
play an important role in Au + Au collisions. While
for pT > 4GeV/c, it shows a clear
decreasing trend from peripheral to mid-central and
central collisions.
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Slope parameter Teff from the exponential function
fits to the mT spectra for different particles in
central Au + Au collisions. The dashed lines depict
linear function fits to π, K, p and φ,
Ξ, Ω, D0 respectively.
The low pT D0
spectra are fit to various thermal model inspired
functions to study the D0 meson
radial collectivity. The observations suggest
that D0 hadrons show a radial
collective behavior with the medium, but freeze-out
from the system earlier and gain less radial
collectivity compared to π, K, and p
particles, while D0 mesons have
similar kinetic freeze-out properties as
multi-strange-quark hadrons such as φ
and Ξ.
The paper also presents a detail description of the
HFT detector performance and efficiency corrections
for charmed hadron reconstruction, particularly the
usage of data-driven simulation method that may
inspire the efficiency correction procedure for other
detectors.
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