119235607
Error estimation for moment analysis in heavy-ion collision experiment
Higher moments of conserved quantities are predicted to be sensitive to the correlation length and connected to the thermodynamic susceptibility. Thus, higher moments of net-baryon, net-charge and net-strangeness have been extensively studied theoretically and experimentally to explore phase structure and bulk properties of QCD matters created in a heavy-ion collision experiment. As the higher moment analysis is a statistic hungry study, the error estimation is crucial to extract physics information from the limited experimental data. In this paper, we will derive the limit distributions and error formula based on the delta theorem in statistics for various order moments used in the experimental data analysis. The Monte Carlo simulation is also applied to test the error formula.
119270025
Search for the QCD Critical Point by Higher Moments of Net-proton Multiplicity Distributions at STAR
Abstract We present the measurements of the higher moments of the net-proton multiplicity distributions in Au + Au collisions from the first phase of the beam energy scan program at RHIC. The measurements are carried out at midrapidity ( | y | 0.5 ) and within the transverse momentum range 0.4 p T 0.8 GeV / c by STAR. We report the centrality and energy dependence of the moment products ( κ σ 2 and Sσ ), with σ 2 , S and κ being the variance, skewness and kurtosis, respectively. These moment products are related to the ratios of various order baryon number susceptibilities and sensitive to the correlation length, and hence can be used to search for the QCD critical point. The results are compared to the Poisson expectations, as well as transport model calculations to understand the contributions from effects not related to critical physics.
115143184
Baseline for the cumulants of net-proton distributions at STAR
Abstract We present a systematic comparison between the recently measured cumulants of the net-proton distributions by STAR for 0–5% central Au + Au collisions at s NN = 7.7 – 200 GeV and two kinds of possible baseline measure, the Poisson and Binomial baselines. These baseline measures are assuming that the proton and anti-proton distributions independently follow Poisson statistics or Binomial statistics. The higher order cumulant net-proton data are observed to deviate from all the baseline measures studied at 19.6 and 27 GeV. We also compare the net-proton with net-baryon fluctuations in UrQMD and AMPT model, and convert the net-proton fluctuations to net-baryon fluctuations in AMPT model by using a set of formula.
124177711
Higher Moments of Event-by-Event Net-proton Multiplicity Distributions in Ultra-relativistic Heavy Ion Collision
of the Dissertation Higher Moments of Event-by-Event Net-proton Multiplicity Distributions in Ultra-relativistic Heavy Ion Collision
119221604
Baseline drift effect on the performance of neutron and gamma ray discrimination using frequency gradient analysis
Frequency gradient analysis (FGA) effectively discriminates neutrons and gamma rays by examining the frequency-domain features of the photomultiplier tube anode signal. This approach is insensitive to noise but is inevitably affected by the baseline drift, similar to other pulse shape discrimination methods. The baseline drift effect is attributed to the factors such as power line fluctuation, dark current, noise disturbances, hum, and pulse tail in front-end electronics. This effect needs to be elucidated and quantified before the baseline shift can be estimated and removed from the captured signal. Therefore, the effect of baseline shift on the discrimination performance of neutrons and gamma rays with organic scintillation detectors using FGA is investigated in this paper. The relationship between the baseline shift and discrimination parameters of FGA is derived and verified by an experimental system consisting of an americium-beryllium source, a BC501A liquid scintillator detector, and a 5 GSPS 8-bit oscilloscope. Both theoretical and experimental results show that the estimation of the baseline shift is necessary, and the removal of baseline drift from the pulse shapes can improve the discrimination performance of FGA.