arXiv subjects

Mao-Wu Nie

Publications and source records attributed to Mao-Wu Nie.

5 recordsLinked to original sources

arXiv2020

An extended $R^{(2)}_{Ψ_m}(ΔS_2)$ correlator for detecting and characterizing the Chiral Magnetic Wave

The extended $R^{(2)}_{Ψ_{m}}(ΔS_{2})$ correlator is presented and examined for its efficacy to detect and characterize the quadrupole charge separation ($ΔS_{2}$) associated with the purported Chiral Magnetic Wave (CMW) produced in heavy-ion collisions. Sensitivity tests involving varying degrees of proxy CMW signals injected into events simulated with the Multi-Phase Transport Model (AMPT), show that the $R^{(2)}_{Ψ_{m}}(ΔS_{2})$ correlator provides discernible responses for the background- and CMW-driven charge separation. This distinction could aid identification of the CMW via measurements of the $R^{(2)}_{Ψ_{2}}(ΔS_{2})$ and $R^{(2)}_{Ψ_{3}}(ΔS_{2})$ correlators, relative to the second- ($Ψ_2$) and third-order ($Ψ_3$) event planes. The tests also indicate a level of sensitivity that would allow for robust experimental characterization of the CMW signal.

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arXiv2020

A sensitivity study of the primary correlators used to characterize chiral-magnetically-driven charge separation

A Multi-Phase Transport (AMPT) model is used to study the detection sensitivity of two of the primary correlators -- $Δγ$ and $R_{Ψ_{2}}$ -- employed to characterize charge separation induced by the Chiral Magnetic Effect (CME). The study, performed relative to several event planes for different input "CME signals", indicates a detection threshold for the fraction $f_{\rm CME}=Δγ_{\rm CME}/Δγ$, which renders the $Δγ$-correlator insensitive to values of the Fourier dipole coefficient $a_1 \lesssim 2.5\%$, that is larger than the purported signal(signal difference) for ion-ion(isobaric) collisions. By contrast, the $R_{Ψ_{2}}$ correlator indicates concave-shaped distributions with inverse widths ($\mathrm{σ^{-1}_{R_{Ψ_2}}}$) that are linearly proportional to $a_1$, and independent of the character of the event plane used for their extraction. The sensitivity of the $R_{Ψ_{2}}$ correlator to minimal CME-driven charge separation in the presence of realistic backgrounds, could aid better characterization of the CME in heavy-ion collisions.

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arXiv2019

Sensitivity analysis of the chiral magnetic effect observables using a multiphase transport model

Because the traditional observable of charge-dependent azimuthal correlator $γ$ contains both contributions from the chiral magnetic effect (CME) and its background, a new observable of $R_{Ψ_{m}}$ has been recently proposed which is expected to be able to distinguish the CME from the background. In this study, we apply two methods to calculate $R_{Ψ_{m}}$ using a multiphase transport model without or with introducing a percentage of CME-induced charge separation. We demonstrate that the shape of final $R_{Ψ_{2}}$ distribution is flat for the case without the CME, but concave for that with an amount of the CME, because the initial CME signal survives from strong final state interactions. By comparing the responses of $R_{Ψ_{2}}$ and $γ$ to the strength of the initial CME, we observe that two observables show different nonlinear sensitivities to the CME. We find that the shape of $R_{Ψ_{2}}$ has an advantage in measuring a small amount of the CME, although it requires large event statistics.

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arXiv2018

Multiparticle azimuthal cumulants in p+Pb collisions from a multiphase transport model

A new subevent cumulant method was recently developed, which can significantly reduce the non-flow contributions in long-range correlations for small systems compared to the standard cumulant method. In this work, we study multi-particle cumulants in $p$+Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV with a multiphase transport model (AMPT), including two- and four-particle cumulants ($c_{2}\{2\}$ and $c_{2}\{4\}$) and symmetric cumulants [SC(2, 3) and SC(2, 4)]. Our numerical results show that $v_{2}\{2\}$ is consistent with the experimental data, while the magnitude of $c_{2}\{4\}$ is smaller than the experimental data, which may indicate either the collectivity is underestimated or some dynamical fluctuations are absent in the AMPT model. For the symmetric cumulants, we find that the results from the standard cumulant method are consistent with the experimental data, but those from the subevent cumulant method show different behaviors. The results indicate that the measurements from the standard cumulant method are contaminated by non-flow effects, especially when the number of produced particles is small. The subevent cumulant method is a better tool to explore the $real$ collectivity in small systems.

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arXiv2014

Azimuthal anisotropies of reconstructed jets in Pb+Pb collisions at $\sqrt{s_{_{\rm NN}}}$ = 2.76 TeV in a multiphase transport model

Azimuthal anisotropies of reconstructed jets [$v_{n}^{jet} (n=2, 3)$] have been investigated in Pb+Pb collisions at the center of mass energy $\sqrt{s_{_{\rm NN}}}$ = 2.76 TeV within a framework of a multiphase transport (AMPT) model. The $v_{2}^{jet}$ is in good agreement with the recent ATLAS data. However, the $v_{3}^{jet}$ shows a smaller magnitude than $v_{2}^{jet}$, and approaches zero at a larger transverse momentum. It is attributed to the path-length dependence in which the jet energy loss fraction depends on the azimuthal angles with respect to different orders of event planes. The ratio $v_{n}^{jet}/\varepsilon_{n}$ increases from peripheral to noncentral collisions, and $v_{n}^{jet}$ increases with the initial spatial asymmetry ($\varepsilon_{n}$) for a given centrality bin. These behaviors indicate that the $v_{n}^{jet}$ is produced by the strong interactions between jet and the partonic medium with different initial geometry shapes. Therefore, azimuthal anisotropies of reconstructed jet are proposed as a good probe to study the initial spatial fluctuations, which are expected to provide constraints on the path-length dependence of jet quenching models.

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