arXiv subjects

Y. G. Ma

Publications and source records attributed to Y. G. Ma.

At least 181 records · Page 10Linked to original sources

arXiv2007

Systematic study of isoscaling behavior in projectile fragmentation by the statistical abrasion-ablation model

The isospin effect and isoscaling behavior in projectile fragmentation have been systematically investigated by a modified statistical abrasion-ablation (SAA) model. The normalized peak differences and reduced isoscaling parameters are found to decrease with ($Z_{proj}-Z$)/$Z_{proj}$ or the excitation energy per nucleon and have no significant dependence on the size of reaction systems. Assuming a Fermi-gas behavior, the excitation energy dependence of the symmetry energy coefficients are tentatively extracted from $α$ and $β$ which looks consistent with the experimental data. It is pointed out that the reduced isoscaling parameters can be used as an observable to study excitation extent of system and asymmetric nuclear equation of state in heavy ion collisions.

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arXiv2007

Comparison of elastic electron or positron scattering from proton-rich nuclei

We investigate the cross sections of the elastic electron or positron scattering from $^{208}$Pb, $^{12}$C, $^{12,16}$O and $^{28, 32}$S by the relativistic partial-wave expansion method using the static charge density distribution from the self-consistent relativistic mean field model and also calculate the charge form factor for $^{12, 16}$O and $^{28, 32}$S. The numerical results are compared with the available data. Calculations indicate that the extended charge density distributions of $^{12}$O and $^{28}$S have observable effects on the cross sections of the electron or positron scattering as well as the charge form factors.

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arXiv2007

Scaling of Anisotropic Flows and Nuclear Equation of State in Intermediate Energy Heavy Ion Collisions

Elliptic flow ($v_2$) and hexadecupole flow ($v_4$) of light clusters have been studied in details for 25 MeV/nucleon $^{86}$Kr + $^{124}$Sn at large impact parameters by Quantum Molecular Dynamics model with different potential parameters. Four parameter sets which include soft or hard equation of state (EOS) with/without symmetry energy term are used. Both number-of-nucleon ($A$) scaling of the elliptic flow versus transverse momentum ($p_t$) and the scaling of $v_4/A^{2}$ versus $(p_t/A)^2$ have been demonstrated for the light clusters in all above calculation conditions. It was also found that the ratio of $v_4/{v_2}^2$ keeps a constant of 1/2 which is independent of $p_t$ for all the light fragments. By comparisons among different combinations of EOS and symmetry potential term, the results show that the above scaling behaviors are solid which do not depend the details of potential, while the strength of flows is sensitive to EOS and symmetry potential term.

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arXiv2007

Examining exotic structure of proton-rich nucleus $^{23}$Al

The longitudinal momentum distribution (P_{//}) of fragments after one-proton removal from ^{23} Al and reaction cross sections (σ_R) for ^{23,24} Al on carbon target at 74A MeV have been measured. The ^{23,24} Al ions were produced through projectile fragmentation of 135 A MeV ^{28} Si primary beam using RIPS fragment separator at RIKEN. P_{//} is measured by a direct time-of-flight (TOF) technique, while σ_R is determined using a transmission method. An enhancement in σ_R is observed for ^{23} Al compared with ^{24} Al. The P_{//} for ^{22} Mg fragments from ^{23} Al breakup has been obtained for the first time. FWHM of the distributions has been determined to be 232 \pm 28 MeV/c. The experimental data are discussed by using Few-Body Glauber model. Analysis of P_{//} demonstrates a dominant d-wave configuration for the valence proton in ground state of ^{23} Al, indicating that ^{23} Al is not a proton halo nucleus.

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arXiv2007

Isospin effect in the statistical sequential decay

Isospin effect of the statistical emission fragments from the equilibrated source is investigated in the frame of statistical binary decay implemented into GEMINI code, isoscaling behavior is observed and the dependences of isoscaling parameters $α$ and $β$ on emission fragment size, source size, source isospin asymmetry and excitation energies are studied. Results show that $α$ and $β$ neither depends on light fragment size nor on source size. A good linear dependence of $α$ and $β$ on the inverse of temperature $T$ is manifested and the relationship of $α=4C_{sym}[(Z_{s}/A_{s})_{1}^{2}-(Z_{s}/A_{s})_{2}^{2}]/T$ and $β=4C_{sym}[(N_{s}/A_{s})_{1}^{2}-(N_{s}/A_{s})_{2}^{2}]/T$ from different isospin asymmetry sources are satisfied. The symmetry energy coefficient $C_{sym}$ extracted from simulation results is $\sim$ 23 MeV which includes both the volume and surface term contributions, of which the surface effect seems to play a significant role in the symmetry energy.

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arXiv2007

Transverse momentum and pseudorapidity dependences of $'\bm{Mach-like}'$ correlations for central Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV

The transverse momentum and pseudorapidity dependences of partonic {`\it{Mach-like}'} shock wave have been studied by using a multi-phase transport model (AMPT) with both partonic and hadronic interactions. The splitting parameter $D$, i.e. half distance between two splitting peaks on away side in di-hadron azimuthal angular ($Δϕ$) correlations, slightly increases with the transverse momentum of associated hadrons ($p^{assoc}_T$), which is consistent with preliminary experimental trend, owing to different interaction-lengths/numbers between wave partons and medium in strong parton cascade. On the other hand, the splitting parameter $D$ as a function of pseudorapidity of associated hadrons ($η^{assoc}$), keeps flat in mid-pseudorapidity region and rapidly drops in high-pseudorapidity region, which is as a result of different violent degrees of jet-medium interactions in the medium that has different energy densities in the longitudinal direction. It is proposed that the research on the properties of {`\it{Mach-like}'} correlation can shed light on the knowledge of both partonic and hadronic interactions at RHIC.

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arXiv2007

Three-Particle Correlations from Parton Cascades in Au+Au Collisions

We present a study of three-particle correlations among a trigger particle and two associated particles in Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV using a multi-phase transport model (AMPT) with both partonic and hadronic interactions. We found that three-particle correlation densities in different angular directions with respect to the triggered particle (`center', `cone', `deflected', `near' and `near-away') increase with the number of participants. The ratio of `deflected' to `cone' density approaches to 1.0 with the increasing of number of participants, which indicates that partonic Mach-like shock waves can be produced by strong parton cascades in central Au+Au collisions.

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arXiv2006

Scaling of Anisotropic Flows in Intermediate Energy and Ultra-relativistic Heavy Ion Collisions

Anisotropic flows ($v_2$ and $v_4$) of hadrons and light nuclear clusters are studied by a partonic transport model and nucleonic transport model, respectively, in ultra-relativistic and intermediate energy heavy ion collisions. Both number-of-constituent-quark scaling of hadrons, especially for $ϕ$ meson which is composed of strange quarks, and number-of-nucleon scaling of light nuclear clusters are discussed and explored for the elliptic flow ($v_2$). The ratios of $v_4/v_2^2$ of hadrons and nuclear clusters are, respectively, calculated and they show different constant values which are independent of transverse momentum. The above phenomena can be understood, respectively, by the coalescence mechanism in quark-level or nucleon-level.

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arXiv2006

Moment Analysis and Zipf Law

The moment analysis method and nuclear Zipf's law of fragment size distributions are reviewed to study nuclear disassembly. In this report, we present a compilation of both theoretical and experimental studies on moment analysis and Zipf law performed so far. The relationship of both methods to a possible critical behavior or phase transition of nuclear disassembly is discussed. In addition, scaled factorial moments and intermittency are reviewed.

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arXiv2006

Experimental determination of the symmetry energy of a low density nuclear gas

Experimental analyses of moderate temperature nuclear gases produced in the violent collisions of 35 MeV/nucleon$^{64}$Zn projectiles with $^{92}$Mo and $^{197}$Au target nuclei reveal a large degree of alpha particle clustering at low densities. For these gases, temperature and density dependent symmetry energy coefficients have been derived from isoscaling analyses of the yields of nuclei with A $\leq 4$. At densities of 0.01 to 0.05 times the ground state density of symmetric nuclear matter, the temperature and density dependent symmetry energies are 10.7 to 13.5 MeV. These values are much larger than those obtained in mean field calculations. They are in quite good agreement with results of a recently proposed Virial Equation of State calculation.

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arXiv2006

The Proto Type of Shanghai Laser Electron Gamma Source at 100 MeV LINAC

The design for the proto type of the Shanghai Laser Electron Gamma Source (SLEGS) at the Shanghai Synchrotron Radiation Facility (SSRF) is introduced. Some detailed descriptions for design of related instruments are provided. The proto type can produce X-ray with energy of 10 keV order. A description of the kinematics of Compton backscattering mechanism and the related simulation results are presented and discussed. The backgrounds from dipole magnet and bremsstrahlung are estimated and the signal-noise ratio is also given.

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arXiv2006

Nucleon-nucleon momentum correlation function for light nuclei

Nucleon-nucleon momentum correlation function have been presented for nuclear reactions with neutron-rich or proton-rich projectiles using a nuclear transport theory, namely Isospin-Dependent Quantum Molecular Dynamics model. The relationship between the binding energy of projectiles and the strength of proton-neutron correlation function at small relative momentum has been explored, while proton-proton correlation function shows its sensitivity to the proton density distribution. Those results show that nucleon-nucleon correlation function is useful to reflect some features of the neutron- or proton-halo nuclei and therefore provide a potential tool for the studies of radioactive beam physics.

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arXiv2006

Time evolution of Mach-like structure in a partonic transport model

The time evolution of Mach-like structure (the splitting of the away side peak in di-hadron $Δϕ$ correlation) is presented in the framework of a dynamical partonic transport model. With the increasing of the lifetime of partonic matter, Mach-like structure can be produced and developed by strong parton cascade process. Not only the splitting parameter but also the number of associated hadrons ($N_{h}^{assoc}$) increases with the lifetime of partonic matter and partonic interaction cross section. Both the explosion of $N_{h}^{assoc}$ following the formation of Mach-like structure and the corresponding results of three-particle correlation support that a partonic Mach-like shock wave can be formed by strong parton cascade mechanism. Therefore, the studies about Mach-like structure may give us some critical information, such as the lifetime of partonic matter and hadronization time.

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arXiv2006

An Intense $γ$-ray Beam Line of 10 MeV Order Based on Compton Backscattering

Shanghai Laser Electron Gamma Source, a $γ$-ray beam line of 10MeV order was proposed recently. The beam line is expected to generate $γ$-ray with maximum energy of 22MeV by backward Compton scattering between CO$_2$ laser and electron in the 3.5GeV storage ring of future Shanghai Synchrotron Radiation Facility. The flux of non-collimated $γ$-ray can be 10$^9$ $\sim$ 10$^{10}$s$^{-1}$ if a commercial CO$_2$ laser of 100W order output power is employed and injected with optimized settings.

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arXiv2006

Scaling of anisotropy flows in intermediate energy heavy ion collisions

Anisotropic flows ($v_1$, $v_2$ and $v_4$) of light nuclear clusters are studied by a nucleonic transport model in intermediate energy heavy ion collisions. The number-of-nucleon scalings of the directed flow ($v_1$) and elliptic flow ($v_2$) are demonstrated for light nuclear clusters. Moreover, the ratios of $v_4/v_2^2$ of nuclear clusters show a constant value of 1/2 regardless of the transverse momentum. The above phenomena can be understood by the coalescence mechanism in nucleonic level and are worthy to be explored in experiments.

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arXiv2006

Di-hadron azimuthal correlation and Mach-like cone structure in parton/hadron transport model

In the framework of a multi-phase transport model (AMPT) with both partonic and hadronic interactions, azimuthal correlations between trigger particles and associated scattering particles have been studied by the mixing-event technique. The momentum ranges of these particles are $3< p^{trig}_T< 6$ GeV/$c$ and $0.15< p_{T}^{assoc} < 3$ GeV/$c$ (soft), or $2.5 $ increases, with the impact parameter in the AMPT model including partonic dynamics from string melting scenario.

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arXiv2006

Elliptic flow of $ϕ$ meson and strange quark collectivity at RHIC

Based on A Multi-Phase Transport (AMPT) model, we have studied the elliptic flow $v_{2}$ of $ϕ$ mesons from reconstructed $K^{+}K^{-}$ decay channel at the top Relativistic Heavy Ion Collider energy at Brookhaven National Laboratory. The dependences of $v_{2}$ on transverse momentum $p_T$ and collision centrality are presented and the rescattering effect of $ϕ$ mesons in the hadronic phase is also investigated. The results show that experimental measurement of $v_{2}$ for $ϕ$ mesons can retain the early collision information before $ϕ$ decays and that the $ϕ$ $v_2$ value obeys the constituent quark number scaling which has been observed for other mesons and baryons. Our study indicates that the $ϕ$ $v_2$ mostly reflects partonic level collectivity developed during the early stage of the nucleus-nucleus collision and the strange and light up/down quarks have developed similar angular anistropy properties at the hadronization.

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arXiv2006

Di-hadron and Tri-hadron correlation and Mach-like cone structure

In a framework of a multi-phase transport model with both partonic and hadronic interactions, azimuthal correlations between trigger particles and associated scattering particles in Au + Au collisions at $\sqrt{s_{NN}}$ = 200 GeV/$c$ have been studied by the mixing-event technique. The Mach-like structure has been observed in correlation function for central collisions. It is shown that the Mach-like structure is basically born in the partonic process and further developed in hadronic rescattering process. However, hadronic rescattering alone cannot reproduce the amplitude of Mach-like cone on away side, therefore partonic cascade process is necessary to describe the amplitude of Mach-like cone on away side in experiment. In addition, three-particle correlations have been investigated in central Au + Au collisions with the AMPT model, and the results support the conclusion that partonic cascade processes enhance the opening angle of Mach-like cone structures.

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