scholarly journals Measurements of open charm production and flow in √sNN = 200GeV Au+Au collisions with the STAR experiment at RHIC

2018 ◽  
Vol 192 ◽  
pp. 00015
Author(s):  
Spyridon Margetis
Keyword(s):  
Transport Model ◽  
Supervised Machine Learning ◽  
Heavy Flavor ◽  
Strong Suppression ◽  
Data Set ◽  
Model Calculations ◽  
Central Collisions ◽  
200 Gev ◽  
Star Experiment ◽  
Signal Significance

We present an improved, higher statistics, measurement with respect to the previously published results of the D0 meson elliptic flow (v2) as a function of transverse momentum (pT) in Au+Au collisions at √sNN = 200 GeV with the STAR Heavy Flavor Tracker (HFT). The D0 v2 results are compared to those of light-flavor hadrons to test the number-of-constituent-quark (NCQ) scaling. They are also compared to recent hydrodynamic and transport model calculations. We also report on the updated measurements of D0 nuclear modification factors RAA and RCP using the 2014 data. The measured D0 RAAin central collisions is less than 1 across the entire pT region. The D0 yields show strong suppression at high pT (> 6 GeV/c) in central collisions, consistent with those of light flavor hadrons. We also report the measurements of collision centrality and pT dependences of the Λ±c production in Au+Au collisions at √sNN = 200 GeV, using the HFT. The Λ±c signal significance is greatly improved with the addition of the highstatistics data set collected in 2016 and the use of a supervised machine learning method for a more effcient topological reconstruction of the decay vertices. The measured Λ±c/D0 ratio in 10-80% Au+Au collisions shows a significant enhancement compared to the PYTHIA prediction for p + p collisions, across the measured pT range.

scholarly journals Production of Open-Charm Hadrons in AuAu Collisions at sNN=200GeV Mesured by the STAR Experiment +†

Proceedings ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 10 ◽  
Author(s):  
Jan Vanek
Keyword(s):  
Charm Quark ◽  
Heavy Ion ◽  
Open Charm ◽  
Hadronic Decay ◽  
Relativistic Heavy Ion Collisions ◽  
Supervised Machine Learning ◽  
Machine Learning Techniques ◽  
Heavy Flavor ◽  
Quark Interaction ◽  
Star Experiment

Charm quarks are primarily produced at the early stages of ultra-relativistic heavy-ion collisions and can therefore probe the quark-gluon plasma throughout its whole evolution. Final-state open-charm hadrons are commonly used to experimentally study the charm quark interaction with the medium. Thanks to the excellent secondary vertex resolution provided by the Heavy Flavor Tracker, STAR is able to directly reconstruct D ± , D 0 , D s , and Λ c ± via their hadronic decay channels. The topological cuts for signal extraction are optimized using supervised machine learning techniques. In these proceedings, we present an overview of recent open charm results from the STAR experiment. The nuclear modification factors of open-charm mesons and Λ c ± /D 0 ratio are shown as functions of transverse momentum and collision centrality.

scholarly journals Charged-pion production in $$\mathbf {Au+Au}$$ collisions at $$\sqrt{\mathbf {s}_{\mathbf {NN}}} = 2.4~{\mathbf {GeV}}$$

2020 ◽  
Vol 56 (10) ◽  
Author(s):  
J. Adamczewski-Musch ◽  
◽  
O. Arnold ◽  
C. Behnke ◽  
A. Belounnas ◽  
...  
Keyword(s):  
Charged Pion ◽  
Transport Model ◽  
Polar Angle ◽  
Transverse Mass ◽  
Angular Distributions ◽  
Model Calculations ◽  
Central Collisions ◽  
Pion Emission ◽  
Pion Multiplicity ◽  
Momentum Transverse

AbstractWe present high-statistic data on charged-pion emission from Au + Au collisions at $$\sqrt{s_{\mathrm{NN}}} = 2.4~\hbox {GeV}$$ s NN = 2.4 GeV (corresponding to $$E_{beam} = 1.23~\hbox {A GeV}$$ E beam = 1.23 A GeV ) in four centrality classes in the range 0–40% of the most central collisions. The data are analyzed as a function of transverse momentum, transverse mass, rapidity, and polar angle. Pion multiplicity per participating nucleon decreases moderately with increasing centrality. The polar angular distributions are found to be non-isotropic even for the most central event class. Our results on pion multiplicity fit well into the general trend of the available world data, but undershoot by $$2.5~\sigma $$ 2.5 σ data from the FOPI experiment measured at slightly lower beam energy. We compare our data to state-of-the-art transport model calculations (PHSD, IQMD, PHQMD, GiBUU and SMASH) and find substantial differences between the measurement and the results of these calculations.

scholarly journals Open Bottom Production in Au+Au Collisions at s NN = 200 GeV with the STAR Experiment

2018 ◽  
Vol 46 ◽  
pp. 1860014 ◽  
Author(s):  
Shenghui Zhang
Keyword(s):  
Heavy Flavor ◽  
Vertex Detector ◽  
Significance Level ◽  
Decay Channels ◽  
Nuclear Modification ◽  
Decay Products ◽  
Charm Hadron ◽  
200 Gev ◽  
Star Experiment ◽  
Nuclear Modification Factors

In these proceedings, we present measurements of open bottom hadron production through multiple decay channels in Au+Au collisions at [Formula: see text] = 200 GeV by the STAR experiment. Namely, measurements of nuclear modification factors for electrons, [Formula: see text], and [Formula: see text] from open bottom hadron decays are shown. The decay products are topologically identified utilizing the Heavy Flavor Tracker, a silicon vertex detector installed at STAR during the period of 2014 - 2016. It enables precise reconstruction of displaced decay vertices. The results show large suppression for non-prompt [Formula: see text] and non-prompt [Formula: see text] at high transverse momenta, and indicate less suppression for electrons from bottom hadron decays than for those from charm hadron decays at [Formula: see text] significance level.

scholarly journals Measurements of charm hadron production and anisotropic flow in Au+Au collisions at 200 GeV with the STAR experiment at RHIC

2018 ◽  
Vol 171 ◽  
pp. 18006 ◽  
Author(s):  
Sooraj Radhakrishnan
Keyword(s):  
Charm Quark ◽  
Heavy Ion ◽  
Gluon Plasma ◽  
Hadronic Decay ◽  
Heavy Flavor ◽  
Model Calculations ◽  
Anisotropic Flow ◽  
Ion Collisions ◽  
200 Gev ◽  
Heavy Flavor Quarks

Heavy flavor quarks, owing to their large masses, are predominantly produced through initial hard parton scatterings in heavy-ion collisions, and thus are excellent probes to study properties of the strongly coupled Quark Gluon Plasma (sQGP) medium produced in these collisions. Measurements of anisotropic flow harmonics of heavy flavor hadrons can provide information on the properties of the medium, including the heavy flavor transport coefficient. Charm quark hadronization mechanism in the sQGP medium can be studied through measurements of yields of different charm hadrons. In these proceedings we report on the measurements of elliptic and triangular flow harmonics of D0 mesons as well as the yield ratios of D±s/D0 and Λ±c/D0 in Au+Au collisions at [see formula in PDF] = 200 GeV at RHIC with the STAR detector. These measurements use the STAR Heavy Flavor Tracker (HFT) to reconstruct charm hadrons via their hadronic decay channels. Results are compared to model calculations and the implications on the understanding of charm quark dynamics in the medium are discussed.

scholarly journals Equatorial total column of nitrous oxide as measured by IASI on MetOp-A: implications for transport processes

2009 ◽  
Vol 9 (1) ◽  
pp. 3243-3264 ◽  
Author(s):  
P. Ricaud ◽  
J.-L. Attié ◽  
H. Teyssèdre ◽  
L. El Amraoui ◽  
V.-H. Peuch ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Transport Model ◽  
Local Maximum ◽  
Transport Processes ◽  
Western Pacific ◽  
Chemical Transport Model ◽  
Data Set ◽  
Model Calculations ◽  
Equatorial Band ◽  
Total Column

Abstract. In this paper we use the total columns of nitrous oxide (N2O) as retrieved from the radiance spectra as measured by the Infrared Atmospheric Sounding Interferometer (IASI) instrument aboard the MetOp-A platform and distributed by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) during the March–May (MAM) 2008 period. Since the total column of N2O reflects concentrations in the middle troposphere, cloud-free columnar N2O measurements are used to assess transport processes in the equatorial band (10° S–10° N). We compare the measured data set with the outputs produced by the 3-D chemical-transport model MOCAGE during the period MAM 2002–2004. To reflect MAM 2008 concentrations, MOCAGE results have been scaled by a factor 1.25% in order to represent the change in concentration of N2O since 2004. IASI N2O equatorial measurements show a maximum over Africa (4.96×10−3 kg m−2) and a minimum over South America (4.86×10−3 kg m−2) in very good agreement with the outputs from MOCAGE despite the fact that emissions of N2O are more intense over America than over Africa. The amplitude of the longitudinal variation of total column N2O along the equatorial band is twice as intense in the measurements (~1.6%) than as in the model calculations (~0.8%), and much greater than the IASI mean random error (0.16–0.33%). A difference between the two data sets is observed above the Western Pacific (110° E–150° E) with a marked minimum in IASI compared to MOCAGE. Recent theoretical studies (Ricaud et al., 2007, 2008) have shown the potentially important effect of the Walker and the Hadley cells on the tropospheric distribution of N2O in producing a local maximum in N2O above Africa. Based on equatorial total columns of N2O measured by IASI, we provide measurement evidence that Africa is a zone of convergence of airmasses coming from different convective regions whilst Western Pacific behaves more like a divergence zone.

scholarly journals Studies of Heavy Flavor Jets Using D0-Hadron Correlations in Azimuth and Pseudorapidity in Au Au Collisons at 200 GeV at the STAR Experiment

Proceedings ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 34
Author(s):  
Alexander Jentsch
Keyword(s):  
Early Stage ◽  
Heavy Ion ◽  
Azimuthal Anisotropy ◽  
Relativistic Heavy Ion Collisions ◽  
Strong Interactions ◽  
Heavy Flavor ◽  
Angular Correlations ◽  
Ion Collisions ◽  
200 Gev ◽  
Star Experiment

Heavy flavor (HF) quarks (charm, bottom) are important probes of the medium produced in relativistic heavy-ion collisions because they are formed in the early stage and propagate throughout the lifetime of the system. HF-meson spectra and azimuthal anisotropy ( v 2 ) measurements have been reported by experiments at RHIC and the LHC, and they suggest strong interactions of HF quarks with the medium. D 0 -hadron correlations on relative pseudorapidity and azimuth ( Δ η , Δ ϕ ) provide a method for disentangling correlation structures on ( Δ η , Δ ϕ )—allowing for separation of structures related to jets and bulk phenomena directly, with the D 0 serving as a proxy for a charm jet. In these proceedings, we present 2D D 0 -hadron angular correlations as a function of centrality in Au + Au collisions at s N N = 200 GeV. These data reveal a jet-like, peaked structure at ( Δ η , Δ ϕ ) = (0, 0) (near-side), and a Δ η -independent azimuthal harmonic modulation. Here, we focus on the evolution of the near-side peak’s yield and widths on ( Δ η , Δ ϕ ) as a function of centrality and compare them to results from light flavor correlations.

scholarly journals Global distribution of mean age of stratospheric air from MIPAS SF<sub>6</sub> measurements

2008 ◽  
Vol 8 (3) ◽  
pp. 677-695 ◽  
Author(s):  
G. P. Stiller ◽  
T. von Clarmann ◽  
M. Höpfner ◽  
N. Glatthor ◽  
U. Grabowski ◽  
...  
Keyword(s):  
Standard Error ◽  
Middle Atmosphere ◽  
Transport Model ◽  
Michelson Interferometer ◽  
Latitudinal Gradients ◽  
Data Set ◽  
Model Calculations ◽  
Short Period ◽  
The Mean

Abstract. Global distributions of profiles of sulphur hexafluoride (SF6) have been retrieved from limb emission spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat covering the period September 2002 to March 2004. Individual SF6 profiles have a precision of 0.5 pptv below 25 km altitude and a vertical resolution of 4–6 km up to 35 km altitude. These data have been validated versus in situ observations obtained during balloon flights of a cryogenic whole-air sampler. For the tropical troposphere a trend of 0.230±0.008 pptv/yr has been derived from the MIPAS data, which is in excellent agreement with the trend from ground-based flask and in situ measurements from the National Oceanic and Atmospheric Administration Earth System Research Laboratory, Global Monitoring Division. For the data set currently available, based on at least three days of data per month, monthly 5° latitude mean values have a 1σ standard error of 1%. From the global SF6 distributions, global daily and monthly distributions of the apparent mean age of air are inferred by application of the tropical tropospheric trend derived from MIPAS data. The inferred mean ages are provided for the full globe up to 90° N/S, and have a 1σ standard error of 0.25 yr. They range between 0 (near the tropical tropopause) and 7 years (except for situations of mesospheric intrusions) and agree well with earlier observations. The seasonal variation of the mean age of stratospheric air indicates episodes of severe intrusion of mesospheric air during each Northern and Southern polar winter observed, long-lasting remnants of old, subsided polar winter air over the spring and summer poles, and a rather short period of mixing with midlatitude air and/or upward transport during fall in October/November (NH) and April/May (SH), respectively, with small latitudinal gradients, immediately before the new polar vortex starts to form. The mean age distributions further confirm that SF6 is destroyed in the mesosphere to a considerable degree. Model calculations with the Karlsruhe simulation model of the middle atmosphere (KASIMA) chemical transport model agree well with observed global distributions of the mean age only if the SF6 sink reactions in the mesosphere are included in the model.

scholarly journals Measurements of J/ψ Production and Polarization in p+p and p+Au Collisions at s NN = 200 GeV with the STAR Experiment

2018 ◽  
Vol 46 ◽  
pp. 1860015
Author(s):  
Zhen Liu
Keyword(s):  
Decay Channel ◽  
Muon Decay ◽  
Model Calculations ◽  
Nuclear Modification Factor ◽  
Nuclear Modification ◽  
Nuclear Absorption ◽  
Text Production ◽  
200 Gev ◽  
Modification Factor ◽  
Star Experiment

We present the measurements of [Formula: see text] production at mid-rapidity via the di-muon decay channel in p+p and p+Au collisions at [Formula: see text] = 200 GeV by the STAR experiment at RHIC. In p+p collisions, the measured inclusive [Formula: see text] cross section can be qualitatively described by model calculations. The [Formula: see text] polarization parameters, [Formula: see text], [Formula: see text] as well as the frame-invariant quantity [Formula: see text], are presented as a function of transverse momentum in both the helicity and Collins-Soper frames. No significant polarization is observed. In addition, the nuclear modification factor for inclusive J/[Formula: see text] in p+Au collisions is similar to that measured in d+Au collisions and favors an additional nuclear absorption effect on top of the nuclear PDF effect.

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