Search

Collective flow has been found similar between small colliding systems (p+p and p+A collisions) and large colliding systems (peripheral A+A collisions) at the CERN Large Hadron Collider (LHC). In order to study the difference of collective flow between small and large colliding systems, we employ a point cloud network to identify $p$ $+$ Pb collisions and peripheral Pb $+$ Pb collisions at $\sqrt{s_{NN}} =$ 5.02 TeV from a multiphase transport model (AMPT). After removing the discrepancies in the pseudorapidity distribution and the $p_{\rm T}$ spectra, we capture the discrepancy in anisotropic flow. Although the verification accuracy of our PCN is limited due to similar event-by-event distributions of elliptic and triangular flow, we demonstrate that collective flow between $p$ $+$ Pb collisions and peripheral Pb $+$ Pb collisions becomes more different with increasing final hadron multiplicity and parton scattering cross section., 9 pages, 11 figures

The search for the chiral magnetic effect (CME) in relativistic heavy-ion collisions helps us understand the $\mathcal{CP}$ symmetry breaking in strong interactions and the topological nature of the QCD vacuum. Since the background and signal of the CME have different correlations with respect to the spectator and participant planes, a two-plane method has been proposed to extract the fraction of the CME signal inside the CME observable of $\Delta\gamma$ from the experimental measurements relative to the two planes. Using a multiphase transport model with different strengths of the CME, we reexamine the two-plane method in isobar collisions at $\sqrt{s_{_{\rm NN}}} = 200$ GeV. The ratios of the CME signal and background relative to the two different planes are found to be different, which is inconsistent with the assumptions made in the current experimental measurements. The difference arises from the decorrelation of the chiral magnetic effect relative to spectator and participant planes, which originates from final state interactions. Our finding suggests that the current experimental measurements may overestimate the fraction of the CME signal in the CME observable in relativistic heavy-ion collisions., Comment: 8 pages, 9 figures

We calculate the cumulants and correlation functions of net-kaon multiplicity distributions in Au+Au collisions at $\sqrt{s_{NN}} = 7.7$ GeV using a multiphase transport model (AMPT) with both a new coalescence mechanism and all charge conservation laws. The AMPT model can qualitatively describe the centrality dependences of the net-kaon cumulants and cumulant ratios measured by the STAR experiment. By focusing on the stage evolution of the cumulants, cumulant ratios, and correlation functions, we reveal several key effects on the fluctuations and correlations of strangeness during the dynamical evolution of relativistic heavy-ion collisions, including strangeness production and diffusion, hadronization, hadronic rescatterings, and weak decays. Without considering the quantum chromodynamics critical fluctuations in the dynamic model, we demonstrate that the net-kaon fluctuations can largely represent the net-strangeness fluctuations. Our results provide a baseline for understanding the net-kaon and net-strangeness fluctuations, which help to search for the possible critical behaviors at the critical end point in relativistic heavy-ion collisions., 11 pages, 7 figures; final published version

The transverse momentum $j_{\rm T}$-dependent jet fragmentation functions have been investigated in proton+proton (p $+$ p) and proton+lead (p $+$ Pb) collisions at $\sqrt{s_{\rm NN}} = 5.02~{\rm TeV}$ with a multiphase transport model containing both the simple quark coalescence mechanism and a new hybrid hadronization mechanism with coalescence and fragmentation processes. Hadronized by the new hadronization mechanism, the AMPT model achieves a quantitative description of the $j_{\rm T}$-dependent jet fragmentation functions measured by ALICE. Besides, no obvious jet-medium interaction and cold nuclear matter effects on the $j_{\rm T}$-dependent jet fragmentation functions in p $+$ Pb collisions were observed. We found the $j_{\rm T}$-dependent jet fragmentation functions are dominated by the quark coalescence contribution for the new hadronization mechanism, which can be decomposed into narrow and wide parts. The root mean square value of the wide part depends on the jet radius $R$ and jet transverse momentum $p_{\rm{T, jet}}$, which is sensitive to different hadronization mechanisms and their components. Therefore, the $j_{\rm T}$-dependent jet fragmentation functions are proposed as a sensitive probe to study the non-perturbative hadronization effect of jets in small colliding systems., Comment: 9 pages, 7 figures

Impacts of nuclear structure on multiplicity ($N_{ch}$) and anisotropic flows ($v_{2}$ and $v_{3}$) in the isobaric collisions of $^{96}_{44}$Ru + $^{96}_{44}$Ru and $^{96}_{40}$Zr + $^{96}_{40}$Zr at $\sqrt{s_{NN}}$ = 7.7, 27, 62.4 and 200 GeV are investigated by using the string melting version of A MultiPhase Transport (AMPT) model. In comparison with the experimental data released recently by the STAR collaboration, it is found that the impact of quadrupole deformation $\beta_{2}$ on the $v_{2}$ difference is mainly manifested in the most central collisions, while the octupole deformation $\beta_{3}$ is in the near-central collisions, and the neutron skin effect dominates in the mid-central collisions. Viewing from the energy dependence, these effects are magnified at lower energies., Comment: 10 pages, 7 figures, 1 table

Higher-order cumulants of the distributions of conserved charges, such as net-baryon number, are sensitive to the quantum chromodynamics(QCD) phase transition and the QCD critical point. We calculate the cumulants and correlation functions of proton, antiproton, and net-proton multiplicity distributions in Au+Au collisions at $\sqrt{s_{NN}} = 7.7$ GeV using a multiphase transport model(AMPT). The AMPT model can basically describe the trends of cumulants, cumulant ratios, (normalized) correlation functions of the proton and net-proton measured by the STAR experiment. The multiproton (baryon) correlations in the AMPT model are consistent with the expectation from baryon number conservation. We demonstrate that multiproton (baryon) correlations suffer the dynamical evolution of heavy-ion collisions. Our results provide a baseline for searching for the possible critical behaviors at the critical end point in relativistic heavy-ion collisions., Comment: 13 pages, 15 figures

The presence of $α$-clustered structure in the light nuclei produces different exotic shapes in nuclear structure studies at low energies. Recent phenomenological studies suggest that collision of heavy nuclei with $α$-clustered carbon ($^{12}$C) at relativistic energies can lead to large initial state anisotropies. This is expected to impact the final momentum anisotropies of the produced particles significantly. The emission of electromagnetic radiations is considered to be more sensitive to the initial state compared to hadronic observables and thus photon observables are expected to be affected by the initial clustered structure profoundly. In this work we estimate the production and anisotropic flow of photons from most-central collisions of triangular $α$-clustered carbon and gold at $\sqrt{s_{\rm NN}}=200$ GeV using an event-by-event hydrodynamic framework and compare the results with those obtained from unclustered carbon and gold collisions. We show that the thermal photon $v_3$ for most central collisions is significantly large for the clustered case compared to the case with unclustered carbon, whereas the elliptic flow parameter does not show much difference for the two cases. In addition, the ratio of anisotropic flow coefficients is found to be a potential observable to constrain the initial state produced in relativistic heavy-ion collisions and also to know more about the $α$-clustered structure in carbon nucleus., 8 pages, 7 figures, final published version

The extended RΨm(2)(ΔS2) correlator is presented and examined for its efficacy to detect and characterize the quadrupole charge separation (ΔS2) associated with the purported Chiral Magnetic Wave (CMW) produced in heavy-ion collisions. Sensitivity tests involving varying degrees of charge separation injected into events simulated with the Multi-Phase Transport Model (AMPT) show that the RΨm(2)(ΔS2) correlators provide discernible responses for the background- and signal-driven quadrupole charge separation. This distinction could help identify CMW-induced quadrupole charge separation via measurements of the RΨ2(2)(ΔS2) and RΨ3(2)(ΔS2) correlators, relative to the second- (Ψ2) and third-order (Ψ3) event planes. The tests also indicate a sensitivity level that would allow for robust experimental characterization of possible CMW-induced charge separation.

The extended $R^{(2)}_{\Psi_{m}}(\Delta S_{2})$ correlator is presented and examined for its efficacy to detect and characterize the quadrupole charge separation ($\Delta S_{2}$) 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 $R^{(2)}_{\Psi_{m}}(\Delta S_{2})$ correlator provides discernible responses for the background- and CMW-driven charge separation. This distinction could aid identification of the CMW via measurements of the $R^{(2)}_{\Psi_{2}}(\Delta S_{2})$ and $R^{(2)}_{\Psi_{3}}(\Delta S_{2})$ correlators, relative to the second- ($\Psi_2$) and third-order ($\Psi_3$) event planes. The tests also indicate a level of sensitivity that would allow for robust experimental characterization of the CMW signal., Comment: 7 pages 5 figures - submitted for publication

Based on Monte Carlo (MC) simulations of the interaction of energetic noble gas ions with carbon nanostructures, we have derived the ion-deposited energy formulas and their applications for the above interaction. We also have studied the nuclear point mass effects i.e. the well-known mass ratio effects, and the nuclear point charge effects on the ion-deposited energy then the damage regularities. In particular, we, for first time, find a straight line of the penetrating point threshold energies for energetic noble gas ions. Near this straight line, the nuclear point charge effects dominate the ion-deposited energy then the damage regularities., Comment: 19 pages, 5 figures

Different orientations of $��$-clustered carbon nuclei colliding with heavy ions can result in a large variation in the value of anisotropic flow. Thus, photon flow observables from clustered ${\rm^{12}C}$ and ${\rm^{197}Au}$ collisions could be a potential probe to study the `direct photon puzzle'. We calculate the transverse momentum spectra and anisotropic flow coefficients ($v_n$) of thermal photons from collisions of triangular $��$-clustered carbon and gold at $\sqrt{s_{\rm NN}}=200$ GeV at RHIC using a hydrodynamic model framework and compare the results with those obtained from unclustered carbon and gold collisions. The slope of the thermal photon spectra is found to vary moderately for different orientations of collisions. However, we find that the elliptic ($v_2$) and triangular flow ($v_3$) coefficients of direct photons for specific configurations are significantly larger and predominantly formed by the QGP radiation. A strong anti-correlation between initial spatial ellipticity and triangularity is observed in an event-by-event framework of $��$-clustered ${\rm C+Au}$ collisions. These special features provide us an opportunity to detect the exotic nature of cluster structure inside carbon nucleus using the photon probe in the future experiments., 10 pages, 10 figures; final published version

The extended $R^{(2)}_{��_{m}}(��S_{2})$ correlator is presented and examined for its efficacy to detect and characterize the quadrupole charge separation ($��S_{2}$) 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 $R^{(2)}_{��_{m}}(��S_{2})$ correlator provides discernible responses for the background- and CMW-driven charge separation. This distinction could aid identification of the CMW via measurements of the $R^{(2)}_{��_{2}}(��S_{2})$ and $R^{(2)}_{��_{3}}(��S_{2})$ correlators, relative to the second- ($��_2$) and third-order ($��_3$) event planes. The tests also indicate a level of sensitivity that would allow for robust experimental characterization of the CMW signal., 7 pages 5 figures - submitted for publication

In this study, the degradation effects of inverted metamorphic four-junction (IMM4J) solar cells were investigated after 1 MeV electron irradiation using spectral response and electrical property measurements. The results show that, similar to traditional tri-junction (TJ) GaInP/GaAs/Ge solar cells, the electrical properties (such as I sc , V oc , and P max ) degrade as a function of logφ, where φ represents the electron fluence. In particular, the degradation of V oc is more serious than that of I sc because of the sum rule for V oc and the limit rule for I sc in IMM4J cells. Analysis of the spectral response curves indicates that, unlike traditional TJ cells, the In 0.3 Ga 0.7 As (1.0 eV) sub-cell exhibits the most severe damage in the irradiated IMM4J cells and the In 0.58 Ga 0.42 As sub-cell becomes a limits part for the electrical properties of the IMM4J solar cells.

Because the traditional observable of charge-dependent azimuthal correlator $\gamma$ contains both contributions from the chiral magnetic effect (CME) and its background, a new observable of $R_{\Psi_{m}}$ 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 $R_{\Psi_{m}}$ using a multiphase transport model without or with introducing a percentage of CME-induced charge separation. We demonstrate that the shape of final $R_{\Psi_{2}}$ 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 $R_{\Psi_{2}}$ and $\gamma$ 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 $R_{\Psi_{2}}$ has an advantage in measuring a small amount of the CME, although it requires large event statistics., Comment: 9 pages, 7 figures, add Figure 7 and more details in subsection III B

The overall transverse momentum balance and the redistribution of the lost energy from hard jets for asymmetric dijet events in PbPb collisions at 2.76A TeV at the LHC is studied within a multiphase transport (AMPT) model. A detailed analysis is performed for the projected transverse momentum 〈p/T||〉 contributed from the final charged hadrons carrying different transverse momenta and emitted from different angular directions. We find that the transverse momentum projection 〈p/T||〉 in the leading jet direction is mainly contributed by hard hadrons (pT>8.0GeV/c) in both peripheral and central PbPb collisions, while the opposite direction in central collisions is dominated by soft hadrons (pT=0.5–2.0GeV/c). The study of in-cone and out-of-cone contributions to 〈p/T||〉 shows that these soft hadrons are mostly emitted at large angles away from the dijet axis. Our AMPT calculation is in qualitative agreement with the CMS measurements and the primary mechanism for the energy transported to large angles in the AMPT model is the elastic scattering at the partonic stage. Future studies including also inelastic processes should be helpful in understanding the overestimation of the magnitudes of in-cone and out-of-cone imbalances from our AMPT calculations, and shed light on different roles played by radiative and collisional processes in the redistribution of the lost energy from hard jets.

The isobaric collisions of $^{96}_{44}$Ru + $^{96}_{44}$Ru and $^{96}_{40}$Zr + $^{96}_{40}$Zr have recently been proposed to discern the charge separation signal of the chiral magnetic effect (CME). In this article, we employ the string melting version of a multiphase transport model to predict various charged-particle observables, including $dN/d\eta$, $p_T$ spectra, elliptic flow ($v_2$), and particularly possible CME signals in Ru + Ru and Zr + Zr collisions at $\sqrt{s_{_{\rm NN}}}$ = 200 GeV. Two sets of the nuclear structure parametrization have been explored, and the difference between the two isobaric collisions appears to be small, in terms of $dN/d\eta$, $p_T$ spectra, and $v_2$ for charged particles. We mimic the CME by introducing an initial charge separation that is proportional to the magnetic field produced in the collision, and study how the final-state interactions affect the CME observables. The relative difference in the CME signal between the two isobaric collisions is found to be robust, insensitive to the final-state interactions., Comment: 8 pages, 10 figures; final published version

Three questions should be interesting, for better understanding of the basic physics of damage creation and stopping ions of different types, in the damaged tube: 1) Between the mass and charge effects, i.e. potential- independent and potential- dependent effects on the damaged tube, Which ones may the cross- section $\sigma$ effects belong to? 2) One method has calculated number of energetic recoils (both ions and carbon atoms), which hit the metal layer below the damaged tube, to study the stopping of both incident ions and recoil carbon atoms in it. Another method has calculated the ion- deposited energy $E_0-E_{penetrating}$ in the damaged tube, to distinguish between penetrating and stopped ions. Which method is better for studying the stopping between two ones? 3) Why can tens of the graphitic shells easily stop energetic ions with energies up to 10 keV? Which effects on the stopping? In kinetic energy formulas, we give answers for discussion., Comment: 7 pages

High-energy heavy-ion collisions produce abundant hyperons and nucleons. A dynamical coalescence model coupled with the ART model is employed to study the production probabilities of light clusters, deuteron (d), triton (t), helion ((3)He), and hypertriton ((3)(A)H) at subthreshold energy of A production (approximate to 1 GeV per nucleon). We study the dependence on the reaction system size of the coalescence penalty factor per additional nucleon and entropy per nucleon. The Strangeness Population Factor (S(3) =(3)(A)H/((3)He x A/p)) shows an extra suppression of hypertriton comparing to light clusters of the same mass number. This model predicts a hypertriton production cross-section of a few mu b in (36)Ar+(36)Ar, (40)Ca+(40)Ca and (56)Ni+(56)Ni in 1 A GeV reactions. The production rate is as high as a few hypertritons per million collisions, which shows that the fixed-target heavy-ion collisions at CSR (Lanzhou/China) at A subthreshold energy are suitable for breaking new ground in hypernuclear physics.

Production and properties of -meson under the extreme hot dense matter which is formed in Au + Au collisions at RHIC energy have been briefly reviewed. The issues are focused on transverse momentum (pT) spectra of , elliptic flow of , nuclear modification factor of , the ratio of ?(pT)/(pT) versus pT, the ratio of ?(pT/3)/(pT/2) versus pT/nq, spin alignment of and the enhancement of etc. These observables give the significant information of the strange quark dynamics in hot dense matter under the extreme condition.

We present predictions from the string melting version of a multi-phase transport model on various observables in Pb+Pb collisions at $\sqrt {s_{NN}}=5.02$ TeV. We use the same version of the model as an earlier study that reasonably reproduced dN/dy, $p_{\rm T}$-spectra and elliptic flow of charged pions and kaons at low-$p_{\rm T}$ for central and semi-central heavy ion collisions at 200 GeV and 2.76 TeV. While we compare with the already-available centrality dependence data on charged particle $dN/d\eta$ at mid-pseudorapidity in Pb+Pb collisions at 5.02 TeV, we make predictions on identified particle dN/dy, $p_{\rm T}$-spectra, azimuthal anisotropies $v_n (n=2,3,4)$, and factorization ratios $r_{n}(\eta^{a},\eta^{b}) (n=2,3)$ for longitudinal correlations., Comment: 27 pages, 18 figures, added a new figure, v_2 analysis method modified for some figures; matches published version

The overall transverse momentum balance and the redistribution of the lost energy from hard jets for asymmetric dijet events in PbPb collisions at 2.76~ATeV at the LHC is studied within A Multi-Phase Transport (AMPT) model. A detailed analysis is performed for the projected transverse momentum $\langle \slashed{p}_{T}^{||} \rangle$ contributed from the final charged hadrons carrying different transverse momenta and emitted from different angular directions. We find that the transverse momentum projection $\langle \slashed{p}_{T}^{||} \rangle $ in the leading jet direction is mainly contributed by hard hadrons ($p_T > 8.0$~GeV/$c$) in both peripheral and central PbPb collisions, while the opposite direction in central collisions is dominated by soft hadrons ($p_T = 0.5$-$2.0$~GeV/$c$). The study of in-cone and out-of-cone contributions to $\langle \slashed{p}_{T}^{||} \rangle$ shows that these soft hadrons are mostly emitted at large angles away from the dijet axis. Our AMPT calculation is in qualitative agreement with the CMS measurements and the primary mechanism for the energy transported to large angles in the AMPT model is the elastic scattering at the partonic stage. Future studies including also inelastic processes should be helpful in understanding the overestimation of the magnitudes of in-cone and out-of-cone imbalances from our AMPT calculations, and shed light on different roles played by radiative and collisional processes in the redistribution of the lost energy from hard jets., 11 pages, 7 figures

Ne and Mg isotope chains are investigated based on constrained calculations in the framework of a deformed relativistic mean-field (RMF) model with the NL075 parameter set. The calculated quadrupole deformation and binding energy are compared with other theoretical results as well as the available experimental data. It shows that the calculated deformations of Ne and Mg with the NL075 are more accurate than those obtained with the NL-SH. It is predicted that 19,29,32Ne and 20,31Mg maybe have a triaxial deformation and 25−28Ne and 27−30Mg exhibit a shape coexistence probably. The closure effect of neutron number N=8 for 20Mg is predicted to be very weak.

We perform a complete calculation for the dilepton production from the processes q (q) over bar -> l (l) over bar, Compton-like (qg -> ql (l) over bar, (q) over barg ->(q) over barl (l) over bar), q (q) over bar -> gl (l) over bar, gluon fusion g (g) over bar -> c (c) over bar, annihilation q (q) over bar -> c (c) over bar as well as multiple scattering of quarks in a chemically equilibrating quark-gluon plasma system at finite baryon density. It is found that quark-antiquark annihilation, Compton-like, gluon fusion and multiple scattering of quarks give important contribution. Moreover, the increase of the quark phase life-time with increasing initial quark chemical potential makes the dilepton yield as an increasing function of the initial quark chemical potential.

Distribution of the parallel momentum of $^{28}$Si fragments from the breakup of 30.7 MeV/nucleon $^{29}$P has been measured on C targets. The distribution has the FWHM with the value of 110.5 $\pm$ 23.5 MeV/c which is consistent quantitatively with Galuber model calculation assuming by a valence proton in $^{29}$P. The density distribution is also predicted by Skyrme-Hartree-Fock calculation. Results show that there might exist the proton-skin structure in $^{29}$P., Comment: 4 pages, 4 figures

A candidate for proton halo nucleus 23Al is investigated based on the constrained calculations in the framework of the deformed relativistic mean field (RMF) model with the NL075 parameter set. It is shown by the constrained calculations that the ground state of 23Al has a large deformation that corresponds to the prolate shape. With that large deformation, the non-constrained RMF calculation predicts that there appears an inversion between the 2s1/2 [211] and 1d5/2 [202] shells. The valence proton of 23Al is weakly bound and occupies 2s1/2 [211] and 1d5/2 [202] with the weights of 56% and 29%, respectively. The calculated RMS radius for matter is in agreement with the experimental one. It is also predicted that the difference between the proton RMS radius and the neutron one is very large. This suggests that there exists a proton halo in 23Al.

Based on the relaxation equations describing the chemical equilibration of gluons, quarks and s quarks at finite baryon density derived from the Juttner distribution of partons, with the help of a rapid phase transition scenario from quark phase to hadron phase, we calculate strangeness production in the quark phase and hadron phase. It is found that the K−/π− ratio is enhanced to be larger than that in pp collisions by about a factor 3.

We study the strangeness of a chemically equilibrating quark–gluon plasma at finite baryon density based on the Juttner distribution of partons. We find that the strangeness production depends obviously on the initial values, and will accelerate with the change of the initial system from a chemically non-equilibrated to an equilibrated system. We also find that the calculated strangeness is very different from the one in the thermodynamic equilibrium system. This study may be helpful to understand the formation of quark–gluon plasma via a chemically non-equilibrated evolution framework.

An evolution model of the chemically equilibrating quark–gluon plasma system has been established based on the Juttner distribution function of partons. By studying the dilepton production of the system, we find that due to high initial temperature, large gluon density of the system as well as large gluon fusion gg→c cross section in the intermediate mass region, a dominant contribution to dileptons with intermediate masses is provided by quark–antiquark annihilation q→l and, especially, thermal charmed quarks from the gluon fusion gg→c and quark–antiquark annihilation q→c.

The structures of two couples of mirror nuclei 17F and 17O, 17Ne and 17N in the ground state and in the first excited state are investigated using the relativistic mean-field approach. Two-proton halo in 17Ne in the first excited state and in the ground state and two-neutron halo in 17N in the first excited state are suggested. Meanwhile, one-proton halo in 17F in the first excited state and one-neutron halo in 17O in the first excited state are also suggested. The skin structure appears in 17F and 17N in the ground state.

We illustrate typical experimental reaction cross sections sigma(R) which have obtained on RIBLL at Heavy Ion Research Facility of the Institute of Modern Physics (IMP) at Lanzhou. The corresponding nuclear radii are extracted from the measured experimental sigma(R) using the Glauber model. Meanwhile, theoretical nuclear radii are also calculated using Relativistic density-dependent Hartree and spherical relativistic mean-field theory with Pauli blocking. For comparison, the nuclear radii of these nuclei are also calculated using the empirical radius format in which the deformation has been taken into account. From the given experimental and theoretical nuclear radii, we suggest that there may exist proton halo structure in Al-23, P-27 and may exist proton skin structure in Al-24. We also End that the deformation plays a great role to the nuclear radii.

Properties of nuclei N-13,N-15 and B-9 are investigated in the relativistic mean-field theory with NLZ and NL3 force parameters. The calculated binding energies are very close to the experimental ones. The calculations show that the first excited state (1p(1/2)) in B-9, the first excited state (2s(1/2)) in N-13 and the second excited state (2s(1/2)) in N-15 are weakly bound. In particular, for N-13 and N-15, the proton density distributions in the two above excited states have a long tail and the rms radii of the last proton are greatly larger compared with their respective matter radii. It is predicted that a proton halo exists in the first excited state of N-13 and in the second excited state of N-15, respectively. It also indicates that the first excited state in B-9 is a proton skin state.

The properties of fully reconstructed jet are investigated in p + p and Pb + Pb collisions at sNN = 2.76 TeV within a multiphase transport (AMPT) model with both partonic scatterings and hadronic rescatterings. A large transverse momentum (pT) asymmetry of dijet or photon-jet arises from the strong interactions between jet and partonic matter. The ξ-dependent jet fragmentation function in Pb + Pb collisions is decomposed into two contributions from different jet hadronization mechanisms, that is, fragmentation versus coalescence. The medium modification of differential jet shape displays that the jet energy is redistributed towards a larger radius owing to jet-medium interactions in heavy-ion collisions. Jet triangular azimuthal anisotropy coefficient, v3jet, which shows a smaller magnitude than the elliptic coefficient v2jet, decreases more quickly with increasing jet pT, which can be attributed to a path-length effect of jet energy loss. All of these properties of full jet are consistent with the jet energy loss mechanism in a stronglyinteracting partonic matter in high-energy heavy-ion collisions.

In this paper, a nonlinear dynamic model and multi attitude controllers are developed for Multi-rotor Helicopter. First, different type of Multi-rotor Helicopter and its flight theory is introduced. Secondly, based on the forces and moments on the Multi-rotor Aircraft during its flight, kinematic and dynamic model is founded. Then, the mathematical model is simplified to design attitude controllers. Finally, the model and attitude controllers are established in Simulink, and the controllers are proved to be effective.

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., 5 pages, 6 figures, final published version

With a multi-phase transport (AMPT) model, a γ-jet with known production point and momentum is triggered to search for the origin of double-peak structure in di-hadron azimuthal correlation in central Au+Au collisions at RHIC energy. The different configurations of triggered γ-jet produce different shapes of medium responses. The key of the double-peak structure is found to be a strong shadowing effect of dense core, which is related to transverse expansion and radial flow of partonic matter.

Hanbury–Brown–Twiss (HBT) results of the nucleon–nucleon correlation function have been presented for the nuclear reactions with neutron-rich projectiles using an event-generator, i.e. the isospin-dependent quantum molecular dynamics model. A good agreement of our calculation for the two-halo-neutron correlation function of 11Li with the experimental data has been reached. In addition, we explore the relationship between the single-neutron separation energy and the strength of the HBT results. It is feasible to investigate the exotic structure of neutron-rich nuclei with the HBT method.

Within a multi-phase transport (AMPT) model, dijet asymmetry is studied in Pb+Pb collisions at $\sqrt{s_{_{\rm NN}}}$ = 2.76 TeV. It is found that a large dijet asymmetry ($A_{J}$) is produced by strong interactions between jets and partonic matter. It is demonstrated that hadronization and final-state hadronic rescatterings have little effects on $A_{J}$. The final $A_{J}$ is found to be driven by both initial $A_{J}$ and partonic jet energy loss, which is consistent with an increasing jet energy loss in a hot and strongly interacting partonic medium in more central Pb+Pb collisions., Comment: 6 pages, 7 figures (final published version)

Within a multi-phase transport (AMPT) model with string melting scenario, the transverse momentum imbalance between prompt photon and jet is studied in Pb+Pb collisions at $\sqrt{s_{_{\rm NN}}}$ = 2.76 TeV. Jet loses more energy in more central collisions due to strong partonic interactions between jet parton shower and partonic matter, which is more significant than due to hadronic interactions only. The hadronization and final-state hadronic interactions have little influences on the imbalance. The imbalance ratio $x_{j��}$ is sensitive to both production position and passing direction of $��$-jet, which provides an opportunity to do detail $��$-jet tomography on the formed partonic matter by selecting different $x_{j��}$ ranges. It is also proposed that $��$-hadron azimuthal correlation associated with photon+jet is a probe to see the medium responses to different $��$-jet production configurations., 5 pages, 4 figures, final published version

The binding energies of Al isotopes are investigated by using the Skyrme-Hartree-Fock approach with the SKIII force parameter. Special emphasis is placed on the influence of the isospin effect of the pairing correlation on the proton separation energy. Calculations show that the Skyrme-Hartree-Fock approach provides a good description of the binding energy of Al isotopes with different forms of pairing correlation. Meanwhile, it is found that the isospin effect of the pairing correlation plays a great role to the separation energy when the Al isotopes approach the proton drip line.

Jets, jet-medium interaction and hydrodynamic evolution of fluctuations in initial parton density all lead to the final anisotropic dihadron azimuthal correlations in high-energy heavy-ion collisions. We remove the harmonic flow background and study the net correlations from different sources with different initial conditions within the AMPT model. We also study $��$-hadron correlations which are only influenced by jet-medium interactions., 4 pages, Proceedings for Quark Matter 2011 Conference, May 23-28, 2011, Annecy, France; v2: final published version

MMedium excitation by jet shower propagation inside a quark-gluon plasma is studied within a linear Boltzmann transport and a multiphase transport model. Contrary to the naive expectation, it is the deflection of both the jet shower and the Mach-cone-like excitation in an expanding medium that is found to gives rise to a double-peak azimuthal particle distribution with respect to the initial jet direction. Such deflection is the strongest for hadron-triggered jets which are often produced close to the surface of dense medium due to trigger-bias and travel against or tangential to the radial flow. Without such trigger bias, the effect of deflection on $��$-jet showers and their medium excitation is weaker. Comparative study of hadron and $��$-triggered particle correlations can therefore reveal the dynamics of jet-induced medium excitation in high-energy heavy-ion collisions., 4 pages in RevTeX with 5 figures, finally version in PRL

Within the AMPT Monte Carlo model, hot spots in the initial transverse parton density are shown to lead to harmonic flows which all contribute to dihadron azimuthal correlation. The net back-to-back dihadron correlation after subtraction of harmonic flows still has a double-peak that is independent of the initial geometric triangularity at a fixed impact-parameter and unique to the structure of jet-induced Mach cone and expanding hot spots dragged by radial flow. The longitudinal structure of hot spots also leads to a near-side ridge in dihadron correlation with a large rapidity gap. By successively randomizing the azimuthal angle of the transverse momenta and positions of initial partons, one can isolate the effects of jet-induced medium excitation and expanding hot spots on the dihadron azimuthal correlation with both small and large rapidity gap. The double-peak in the net dihadron correlation is quantitatively different from that in $��$-hadron that is free of the contributions from harmonic flow and hot spots and caused only by jet-induced Mach cone., 4 pages in RevTEx, 7 figures (final published version)

Polyethylene/carbon nanotube (PE/CNT) composites with high hydrogen content as a kind of structural material for space radiation shielding have extensive potential applications in future aerospace field due to their unusual radiation shielding, lightweight, and easy processing. In the space irradiation environment, the composites are sensitive to radiation damage, which changes their microstructures, directly affecting their mechanical performances and shielding effectiveness. Low energy electrons (200 keV) are important radiation environmental factors. Effects and mechanisms for mechanical damage of PE/CNTs composites induced by low energy electrons are studied, which has important academic value and practical significance. Previous research mainly involves the qualitative evaluations of the changes in the mechanical performance index of polymer nanocomposites. The inner relationship between microstructural change induced by radiation and mechanical behavior of the nanocomposites, especially in the PE/CNTs composites has not been studied in depth so far. In this paper, low-density polyethylene (LDPE)/ multi-walled carbon nanotube (MWCNT) composites are chosen as a research object. Based on 110 keV electron irradiation, tensile deformation mechanism of the LDPE/MWCNT composite is studied. The synchrotron radiation X-ray small angle scattering (SAXS) and wide angle diffraction (WAXD) are used to reveal the real-time microstructure evolutions of the nanocomposites after and before irradiation in the process of stretching. Tensile deformation mechanisms of LDPE/MWCNT composite after and before the 110 keV electron irradiation are revealed. Experimental results show that the tensile deformation behavior for the irradiated LDPE by 110 keV electrons is different from that for unirradiated sample. The electron irradiation increases the tensile strength of the LDPE/MWCNT composite and reduces the elongation at break. Moreover, with increasing the irradiation fluence, the tensile strength and the elongation at break of the LDPE/MWCNT composite significantly increases and decreases, respectively. The electron irradiation could hinder the deformations of the LDPE matrix including crystalline case and amorphous case, constrain the fragmentation of original lamellae, the directional arrangement of the MWCNTs, the formation of new crystal and the rotation of lamellae, especially in higher irradiation fluence. During tensile deformation, the main strengthening mechanism for the irradiated LDPE/MWCNT composites by the 110 keV electrons is crosslinking strengthening effect in LDPE matrix. On the other hand, enhanced interaction (mainly interface strengthening) between MWCNTs and LDPE matrix induced by irradiation is attributed to the main strengthening mechanism for the irradiated LDPE/MWCNT composites. These results could provide a theoretical basis and technical support for the reasonable design and successful application of CNT-based polymer composites as structural material for space radiation shielding.

Electrons are an important constituent part of radiation space of charged particles and could damage microelectronic devices. Therefore, effective radiation protection is very important for the electronic device. So, a radiation protecting material with lightweight, high performance and low cost is urgently needed. Polyethylene (PE) with high hydrogen content/carbon nanotube (CNT) composite as a space shielding material is very promising for spacecraft application in the future. In order to meet the requirement of space applications for PE/CNT composite, it is of important academic value and practical significance to explore melting and crystallization behaviors of LDPE/MWCNT composites. In this paper, melting and crystallization behaviours of the irradiated LDPE/MWCNT composites irradiated by 110 keV electrons are studied by differential scanning calorimetry (DSC), synchrotron radiation X-ray small angle scattering (SAXS) and wide angle diffraction (WAXD). Experimental results show that the irradiation by 110 keV electrons does not affect the thermal characteristics of the LDPE, but can enhance the initial melting temperature and the melting-terminating temperature of LDPE/2% MWCNT composites during melting. Also, the radiation by 110 keV electrons could reduce the initial crystallization temperature and the crystallization-terminating temperature during crystallization. MWCNTs could enhance the initial melting temperature and reduce the melting-terminating temperature of LDPE/2% MWCNT composites during melting. Moreover, MWCNTs could enhance the initial crystallization temperature and crystallinity, and reduce the crystallization-terminating temperature during crystallization. SAXS and WAXD analyses show that with increasing the temperature, long periods of the irradiated/unirradiated LDPE increase during melting. Compared with that of the unirradiated LDPE, at a given temperature, long period of the irradiated LDPE is small. During crystallization, with reducing the temperature, long period of the irradiated/unirradiated LDPE begins to appear and gradually decreases. At the same temperature, long period of the irradiated LDPE is larger than that of the unirradiated one. For LDPE/2% MWCNT composites, long periods of the irradiated/unirradiated samples during melting and crystallization do not exist. The 110 keV electron irradiation mainly influences LDPE matrix of LDPE/2% MWCNT composites during melting and crystallization. The 110 keV electron irradiation can slow down the amorphous region expansion and the initial melting of lamellae of the LDPE matrix during melting. The 110 keV electron irradiation can slow down the amorphous region shrinkage and inhibit crystal from growing up during crystallization. During melting, MWCNTs can hinder the amorphous and crystalline molecular chains of LDPE from moving, which hinders the LDPE matrix from initially melting, but promotes the melting process after the initial melting has begun. During crystallization, MWCNTs could promote the formation of crystal of the LDPE matrix and inhibit the crystal from growing up.

Owing to their unique structure and excellent electrical property, carbon nanotubes (CNTs) as an ideal candidate for making future electronic components have great application potentiality. In order to meet the requirements for space application in electronic components, it is necessary to study structural changes and damage mechanisms of multi-walled carbon nanotubes (MWCNTs), caused by the irradiations of 70 and 110 keV electrons. In the paper, the changes of structure and damage mechanisms in the irradiated MWCNTs, induced by the irradiations of 70 and 110 keV electrons, are investigated. The changes in surface morphology and structure of the irradiated MWCNT film are characterized using scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, x-ray diffraction analysis (XRD), and electron paramagnetic resonance (EPR) spectroscopy. It is found that the MWCNTs show different behaviors in structural changes after 70 and 110 keV electron irradiation due to different damage mechanisms. SEM results reveal that the irradiation of 70 keV electrons does not change surface morphology of the MWCNT film, while the irradiation of 110 keV electrons with a high fluence of 5 × 1015 cm−2 leads to evident morphological changes, such as the formation of a rough surface, the entanglement of nanotubes and the shrinkage of nanotubes. Based on Raman spectroscopy, XPS, and XRD analyses, it is confirmed that the irradiation of 70 keV electrons increases the interlayer spacing of the MWCNTs and disorders their structure through electronic excitations and ionization effects, while the irradiation of 110 keV electrons obviously reduces the interlayer spacing of the MWCNTs and improves their graphitic order through knock-on atom displacements. The improvement of the irradiated MWCNTs by 110 keV electrons is attributed to the restructuring of defect sites induced by knock-on atom displacements. EPR spectroscopic analyses reveal that the MWCNTs exposed to both 70 keV electrons and 110 keV electrons suffer ionization damage to some extent.

In this paper, compressive behavior of electrodeposited nano-crystalline (nc) Ni at various temperatures and strain rates is studied using a low temperature mechanic test system. Plastic deformation mechanisms of nc Ni caused by compression are characterized by the strain rate sensitivity index, the activation volume, and examined by scanning electron microscopy and high resolution transmission electron microscopic analysis. Results show that at low temperatures, the plastic deformation of nc Ni is mainly dominated by grain boundary accommodated dislocations. In other words, during plastic deformation of nc Ni at low temperatures, the intrinsic dislocation at the grain boundary bends up and expands without obstacles to the opposite grain boundary in the inner grain dislocation-free zone, until the occurrence of similar cutting forest-dislocation behavior appearing at opposite grain boundary. Moreover, the residual dislocations in the grain boundary bending out during plastic deformation could increase the strain compatibility and decrease the stress concentration. At room temperature, the plastic deformation mechanism of nc Ni is controlled by the deformation of grain boundary accommodated dislocations and grain slipping/rotating. Based on the above analyses, differences in compressive behavior of nc Ni at various temperatures and strain rates can be revealed by the correlation of deformation mechanisms of grain boundary accommodated dislocations and residual dislocation movement, temperature and defects in nc Ni.

Due to their unusual electrical conductivity, carbon nanotubes as the ideal candidates for making future electronic components have extensive application potentiality. In order to meet the requirements in space electronic components for carbon nanotubes, effect of 170 keV proton irradiation on structure and electrical conductivity of multi-walled carbon nanotubes (MWCNTs) film is investigated in this paper. Surface morphologies and microstructure of the carbon nanotube films are examined by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) spectroscopy, respectively. Electrical conductivities of the carbon nanotube films before and after 170 keV proton irradiation are measured using four-point probe technique. SEM analysis reveals that when proton irradiation fluence is greater than 51015 p/cm2, the surface of the carbon nanotube film becomes rough and loose, and obvious bending, shrinkage, and entanglement of nanotubes are observed. Moreover, the shrinkage phenomenon of MWCNTs caused by proton irradiation is found the first time so far as we know. Based on Raman and XPS analyses, it is confirmed that 170 keV protons can improve the ordered structure of the MWCNTs, and irradiation fluence plays a key role in reducing the disorder in the MWCNTs. Improvement of the irradiated MWCNTs by 170 keV protons can be attributed to restructuring of defect sites induced by knock-on atom displacements. On the other hand, carbon impurities on surface of the MWCNT film are reduced due to the effect of sputtering by the 170 keV proton irradiation, which is also helpful to the improvement of the structure of carbon nanotubes. EPR spectra show that the electrons delocalized over carbon nanotubes decrease with increasing irradiation fluence, implying that the carbon nanotube film is not sensitive to ionizing radiation induced by the 170 keV protons, and the electrical conductivities of the MWCNTs films may be decreased. Four-point probe technical analysis shows that with increasing irradiation fluence, electrical properties of the carbon nanotubes film deteriorate, which can be attributed to the changes in electronic properties and morphology of the MWCNT films induced by 170 keV protons. Acquired results could be beneficial to tailoring of structure and properties for the carbon nanotubes film irradiated by protons to develop nanoelectronics of radiation-resistant systems.

In this paper, compression test is carried on electrodeposited nano-crystalline (NC) Ni at 77 K. The results show that the NC Ni has extremely high compressive strengths: around 2.5 GPa at room temperature (RT), 3.5 GPa at 77 K, and moderate plasticity with 0.1 fracture strain at RT, 0.05 at 77 K. The strain rate sensitivity m and activation volume v are calculated, and scanning election microscope and high-resolution transmission election microscope are used to verify the deformation mechanism. Analysis indicates that the dislocation interaction with grain boundary (GB) dominates the deformation of NC Ni both at 77 K and RT. Based on the calculated values of m and v, the deformation process is described by considering the intrinsic dislocation of GB bowing out and expanding towards opposite GB in the inner grain dislocation-free zone. And the mechanism is studied in the residual dislocation parts affecting the increase of strain compatibility and the decrease of stress concentration. It is indicated that the difference in compression property between at RT and 77 K is relatated to grain boundary-dislocation coordination mechanism and relation between residual dislocation motion and temperature.

The high performance nano-crystal Ni material was prepared by the pulse electrodeposition process; the intensity, composition and the microscopic structure of the nano-crystal Ni material were investigated by various measurements. In this paper, the 1 MeV electron was chosen as the irradiation source to investigate the energy loss of high energy electron in the nano-crystal Ni material and conventional bulk Ni material, and the energy deposition process during the electron irradiation was measured by the absorbed dose tablets. The results show that the grain size affects the energy loss process during the 1MeV electron irradiation seriously. The absorbed dose of 1 MeV electron in the nano-crystal Ni material is lower than that in the common Ni material with the same thickness, which indicates that the energy deposition of high energy electron in nano-crystal metal is lower than that in the conventional bulk metal, and the nano-crystal metal has an advantage of radiation resistance.

The local temperature effect on strangeness enhancement in relativistic heavy ion collisions is discussed in the framework of the thermal model in which the K+/h+ ratio becomes smaller with increasing freeze-out temperature. Considering that most strangeness particles of final-state particles are from the kaon meson, the temperature effect may play a role in strangeness production in hot dense matter where a slightly different temperature distribution in different areas could be produced by jet energy loss. This phenomenon is predicted by thermal model calculation at RHIC energy. The Ξ−/ ratio in central Au+Au collisions at 200 GeV from the thermal model depends on the freeze-out temperature obviously when γS is different. It should be one of the reasons why strangeness enhancements of Ξ and are different though they include two strange quarks. These results indicate that thermodynamics is an important factor for strangeness production and the strangeness enhancement phenomenon.