arXiv subjects

Aihong Tang

Publications and source records attributed to Aihong Tang.

27 records · Page 2Linked to original sources

arXiv2011

Statistical Origin of Constituent-Quark Scaling in the QGP hadronization

Nonextensive statistics in a Blast-Wave model (TBW) is implemented to describe the identified hadron production in relativistic p+p and nucleus-nucleus collisions. Incorporating the core and corona components within the TBW formalism allows us to describe simultaneously some of the major observations in hadronic observables at the Relativistic Heavy-Ion Collider (RHIC): the Number of Constituent Quark Scaling (NCQ), the large radial and elliptic flow, the effect of gluon saturation and the suppression of hadron production at high transverse momentum (pT) due to jet quenching. In this formalism, the NCQ scaling at RHIC appears as a consequence of non-equilibrium process. Our study also provides concise reference distributions with a least chi2 fit of the available experimental data for future experiments and models.

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arXiv2010

Directed Flow of Identified Particles in Au + Au Collisions at $\sqrtsNN = 200$ GeV

STAR's measurements of directed flow ($v_1$) for pions, kaons (charged and $K_s^0$), protons and antiprotons for Au + Au collisions at $\sqrtsNN = 200$ GeV are presented. Negative $v_1(y)$ slope is observed for pions, antiprotons, protons and kaons. The proton $v_1(y)$ slope at midrapidity is found extremely small. Sizable difference is seen between $v_1$ of protons and anti-protons in 5-30% central collisions. Anti-flow can explain the negative slope, however, it has difficulties explaining the centrality dependence of the difference between the $v_1(y)$ slopes of protons and anti-protons. The $v_1$ excitation function is presented. Comparisons to model calculations (RQMD, uRQMD, AMPT and QGSM) are made, and it is found that none of the four models can successfully describe the data.

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arXiv2009

Footprints of the (Nearly) Perfect Liquid

In relativistic heavy-ion collisions, the system has gone through a series of evolution, almost at every stage of its evolution it leaves behind footprints in flow observable. Those footprints contain valuable information of the bulk property of the (nearly) perfect liquid. By examing footprints of the nearly perfect liquid, we address a few important issues, including the ideal hydrodynamic limit, estimation of $η/s$, testing the Number of Constituent Quark scaling at low energy, in small system, at large transverse momentum, and in forward region. Future prospect of flow study is discussed.

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arXiv2008

Flow Results and Hints of Incomplete Thermalization

We classified $v_2$ measurements according to their sensitivities w.r.t. to two planes, namely, reaction plane and participant plane. Likewise, in $v_2/ε$ scaling, we showed that one needs to choose a $ε$ that is sensitive to the same plane as that $v_2$ is sensitive to. We presented our $v_2/ε$ as a function of centrality and transverse momentum. We studied the ratio of $v_4/v_2^2$. We discussed the applicable range for hydrodynamics, as well as implications to an incomplete thermalization.

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arXiv2007

Elliptic flow in the Gaussian model of eccentricity fluctuations

We discuss a specific model of elliptic flow fluctuations due to Gaussian fluctuations in the initial spatial $x$ and $y$ eccentricity components $\left\{\mean{(σ_y^2-σ_x^2)/(σ_x^2+σ_y^2)}, \mean{2σ_{xy}/(σ_x^2+σ_y^2)} \right\}$. We find that in this model $\vfour$, elliptic flow determined from 4-particle cumulants, exactly equals the average flow value in the reaction plane coordinate system, $\mean{v_{RP}}$, the relation which, in an approximate form, was found earlier by Bhalerao and Ollitrault in a more general analysis, but under the same assumption that $v_2$ is proportional to the initial system eccentricity. We further show that in the Gaussian model all higher order cumulants are equal to $\vfour$. Analysis of the distribution in the magnitude of the flow vector, the $Q-$distribution, reveals that it is totally defined by two parameters, $\vtwo$, the flow from 2-particle cumulants, and $\vfour$, thus providing equivalent information compared to the method of cumulants. The flow obtained from the $Q-$distribution is again $\vfour=\mean{v_{RP}}$.

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arXiv2007

A method for determining event-by-event elliptic flow fluctuations based on the first-order event plane in heavy-ion collisions

A new method is presented for determining event-by-event fluctuations of elliptic flow, $v_2$, using first-order event planes. By studying the event-by-event distributions of $v_2$ observables and first-order event-plane observables, average flow $\avg{v_2}$ and event-by-event flow fluctuations can be separately determined, making appropriate allowance for the effects of finite multiplicity and non-flow. The method has been tested with Monte Carlo simulations. The connection between flow fluctuations and fluctuations of the initial-state participant eccentricity is discussed.

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arXiv2007

Collective Dynamics at RHIC

The property of the ``perfect liquid'' created at RHIC is probed with anisotropic flow measurements. Different initial conditions and their consequences on flow measurements are discussed. The collectivity is shown to be achieved fast and early. The thermalization is investigated with the ratio of $v_4/v_2^2$. Measurements from three sectors of soft physics (HBT, flow and strangeness) are shown to have a simple, linear, length scaling. Directed flow is found to be independent of system size.

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arXiv2004

Directed and Elliptic Flow at RHIC

We present the directed flow measurement ($v_1$) from Au+Au collisions at $\sqrtsNN = 62$ GeV. Over the pseudorapidity range we have studied, which covers $η$ from -1.2 to 1.2 and $2.4 < |η| < 4$, the magnitude of $v_1$ for charged particles is found to increase monotonously with pseudorapidity for all centralities. No ``$v_1$ wiggle'', as predicted by various theoretical models, is observed at midrapidity. Elliptic flow ($v_2$) from moderate high $p_t$ particles ($3-6 GeV/c$) at $\sqrtsNN = 200$ GeV is presented as a function of impact parameter. It is found that models that are based on {\it jet quenching} alone appear to underpredict $v_2$ at moderate high $p_t$, while the model that incorporates both, recombination and fragmentation, describes the data better.

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arXiv2003

Elliptic Flow From Au+Au Collisions at 200 GeV

This paper presents results of elliptic flow measurements at moderate high transverse momentum in Au+Au collisions using the STAR detector at RHIC. Sizable $v_{2}$ is found up to 7 GeV/c in transverse momentum. Non-flow effects are discussed comparing correlations in p+p collisions and Au+Au collisions. $v_{2}$ from two-, four- and six-particle cumulant are shown and discussed.

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