A direct comparison and analysis of published spectra for the 7$\alpha$ disassembly of $^{28}$Si projectiles excited in collisions with $^{12}$C at 35 MeV/u reveals striking agreement in the derived excitation energies of high excitation energy resonances observed in two different experiments, in contrast to some earlier conclusions reported in the literature. Many of the observed resonances have excitation energies consistent with those arrived at in recent theoretical investigations explicitly predicting the excitation energies and spins of toroidal nuclei. Some additional peaks are observed and the possibility that they correspond to other favored geometries is discussed.

Using a multiphase transport model (AMPT) we calculate the elliptic, $v_2$, and triangular, $v_3$, Fourier coefficients of the two-particle azimuthal correlation function in proton-nucleus (p+Pb) and peripheral nucleus-nucleus (Pb+Pb) collisions. Our results for $v_3$ are in a good agreement with the CMS data collected at the Large Hadron Collider. The $v_2$ coefficient is very well described in p+Pb collisions and is underestimated for higher transverse momenta in Pb+Pb interactions. The characteristic mass ordering of $v_2$ in p+Pb is reproduced whereas for $v_3$ this effect is not observed. We further predict the pseudorapidity dependence of $v_2$ and $v_3$ in p+Pb and observe that both are increasing when going from a proton side to a Pb-nucleus side. Predictions for the higher order Fourier coefficients, $v_4$ and $v_5$, in p+Pb are also presented.

Contact angle is an essential characteristic in wetting, capillarity and moving contact line; however, although contact angle phenomena are effectively simulated, an accurate and real-time measurement for contact angle has not been well studied in computational fluid dynamics, especially in dynamic environments. Here, we design a geometry-based mesoscopic scheme to onthesport measure the contact angle in the lattice Boltzmann method. The computational results without gravity effect are in excellent agreement with the benchmarks from the spherical cap method. The qualities of the scheme are further verified in gravitational environments by simulating sessile and pendent droplets on smooth solid surfaces and contact angle hysteresis on chemically heterogeneous surfaces. This scheme is simple, efficient and requires only the local data. It is independent of multiphase models and can be easily extended to 3D dynamic contact angle measurements.

A system size scan program was recently proposed for the STAR experiments at the Relativistic Heavy Ion Collider(RHIC). In this study, we employ a multiphase transport (AMPT) model for considering the bulk properties at the freeze-out stage for $\mathrm{^{10}B+^{10}B}$, $\mathrm{^{12}C+^{12}C}$, $\mathrm{^{16}O+^{16}O}$, $\mathrm{^{20}Ne+^{20}Ne}$, $\mathrm{^{40}Ca+^{40}Ca}$, $\mathrm{^{96}Zr+^{96}Zr}$, and $\mathrm{^{197}Au+^{197}Au}$ collisions at RHIC energies $\sqrt{s_{NN}}$ of 200, 20, and 7.7 GeV. The results for $\mathrm{^{197}Au+^{197}Au}$ collisions are comparable with those of previous experimental STAR data. The transverse momentum $p_{T}$ spectra of charged particles ($\pi^{\pm}$, $K^{\pm}$, $p$, and $\bar{p}$) at the kinetic freeze-out stage, based on a blast-wave model, are also discussed. In addition, we use a statistical thermal model to extract the parameters at the chemical freeze-out stage, which agree with those from other thermal model calculations. It was found that there is a competitive relationship between the kinetic freeze-out parameter $T_{kin}$ and the radial expansion velocity $\beta_{T}$, which also agrees with the STAR or ALICE results. We found that the chemical freeze-out strangeness potential $\mu_{s}$ remains constant in all collision systems and that the fireball radius $R$ is dominated by $\left\langle \mathrm{N_{Part}}\right\rangle$, which can be well fitted by a function of $a \left\langle \mathrm{N_{Part}}\right\rangle^{b}$ with $b \approx 1/3$. In addition, we calculated the nuclear modification factors for different collision systems with respect to the $\mathrm{{}^{10}B} + \mathrm{{}^{10}B}$ system, and found that they present a gradual suppression within a higher $p_{T}$ range from small to large systems.

We apply a multi-phase transport (AMPT) model to study two-particle angular correlations in $pp$ collisions at $\sqrt{s}= 7$ TeV. Besides being able to describe the angular correlation functions of meson-meson pairs, a large improvement for the angular correlations of baryon-baryon and antibaryon-antibaryon is achieved. We further find that the AMPT model with new quark coalescence provides an even better description on the anti-correlation feature of baryon-baryon correlations observed in the experiments. We also extend the study to p-Pb collisions at $\sqrt{s}= 5.02$ TeV and obtained similar results. These results help us better understand the particle production mechanism in $pp$ and p-Pb collisions at LHC energies.

We report a measurement of high-p_T inclusive pi^0, eta, and direct photon production in p+p and d+Au collisions at sqrt(s_NN) = 200 GeV at midrapidity (0 < eta < 1). Photons from the decay pi^0 -> gamma gamma were detected in the Barrel Electromagnetic Calorimeter of the STAR experiment at the Relativistic Heavy Ion Collider. The eta -> gamma gamma decay was also observed and constituted the first eta measurement by STAR. The first direct photon cross section measurement by STAR is also presented, the signal was extracted statistically by subtracting the pi^0, eta, and omega(782) decay background from the inclusive photon distribution observed in the calorimeter. The analysis is described in detail, and the results are found to be in good agreement with earlier measurements and with next-to-leading order perturbative QCD calculations.

The expanding applications call for novel new-generation wide-bandgap semiconductors. Here, we show that a compound only composed of the ordinary elements Na and Cl, namely three-dimensional NaCl2 crystal, is a wide-bandgap semiconductor. This finding benefits from the breaking of conventional stoichiometry frameworks in the theoretical design, leading to the discovery of three-dimensional XY2 (X = Na, Li, K; Y = Cl, F, Br, I) crystals, with covalent bonds of Y pairs inducing the wide bandgap from 2.24 to 4.45 eV. Crucially, such an unexpected NaCl2 crystal was successfully synthesized under ambient conditions. The unconventional stoichiometric strategy with other chemical elements potentially yields more wide-bandgap semiconductors, offering the capability for bandgap tuning. These unconventional stoichiometric materials may also exhibit superconductivity, transparent inorganic electrides, high-energy-density, and beyond.

In this paper, we introduce the design of electrostatic septum (ESS) for the accelerator of Shanghai Advanced Proton Therapy (SAPT), and discuss its mechanical structure and the material selection of the electrode. The beam loss on the septum is studied, and the calculation results are given by the particle simulation and by the formula which is related to the placement angle and the divergence angle in the horizontal direction. Considering the thermal effect of the beam loss on the head of the septum, the equilibrium temperature at work is calculated. In addition, the distribution of the electric field and the trajectory of the particles are also simulated. The phenomenon of vacuum discharge in the working ESS is analyzed in detail on the relationship between the working current and the enhancement factor of the electric field on the electrode surface. Based on the discharge mechanism, the importance of degassing and cleaning of ESS is analyzed. We also analyzed the effect of external series resistance from circuit and discharge mechanism. It is considered that series resistance within a certain range can increase the breakdown voltage between vacuum electrodes and reduce the irreversible damage to the surface of the electrode system caused by the discharge process. The formula for the value of the resistance is given.

We present measurements of elliptic flow ($v_2$) of electrons from the decays of heavy-flavor hadrons ($e_{HF}$) by the STAR experiment. For Au+Au collisions at $\sqrt{s_{\rm NN}} =$ 200 GeV we report $v_2$, for transverse momentum ($p_T$) between 0.2 and 7 GeV/c using three methods: the event plane method ($v_{2}${EP}), two-particle correlations ($v_2${2}), and four-particle correlations ($v_2${4}). For Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 62.4 and 39 GeV we report $v_2${2} for p_T&lt; 2 GeV/c. $v_2${2} and $v_2${4} are non-zero at low and intermediate $p_T$ at 200 GeV, and $v_2${2} is consistent with zero at low $p_T$ at other energies. The $v_2${2} at the two lower beam energies is systematically lower than at $\sqrt{s_{\rm NN}} =$ 200 GeV for p_T &lt; 1 GeV/c. This difference may suggest that charm quarks interact less strongly with the surrounding nuclear matter at those two lower energies compared to $\sqrt{s_{\rm NN}} = 200$ GeV.

Because they may provide ultrathin, high-flux, and energy-efficient membranes for precise ionic and molecular sieving in aqueous solution, GO membranes (partially oxidized, stacked sheets of graphene) have shown great potential in water desalination and purification, gas and ion separation, biosensors, proton conductors, lithium-based batteries and super-capacitors. Unlike carbon nanotube (CNT) membranes, in which the nanotube pores have fixed sizes, the pores of GO membranes - the interlayer spacing between GO sheets - are of variable size. This presents a challenge for using GO membranes for filtration. Despite the great efforts to tune and fix the interlayer spacing, it remains difficult both to reduce the interlayer spacing sufficiently to exclude small ions while keeping this separation constant against the tendency of GO membranes to swell when immersed in aqueous solution, which greatly affects the applications of GO membranes. Here, we demonstrate experimentally that highly efficient and selective ion rejection by GO membranes can be readily achieved by controlling the interlayer spacing of GO membranes using cations (K+, Na+, Ca2+, Li+ and Mg2+) themselves. The interspacing can be controlled with precision as small as 1 A, and GO membranes controlled by one kind of cation can exclude other cations with a larger hydrated volume, which can only be accommodated with a larger interlayer spacing. First-principles calculations reveal that the strong noncovalent cation-pi interactions between hydrated cations in solution and aromatic ring structures in GO are the cause of this unexpected behavior. These findings open up new avenues for using GO membranes for water desalination and purification, lithium-based batteries and super-capacitors, molecular sieves for separating ions or molecules, and many other applications.

We develop a novel field effect transistor (FET) device using solid ion conductor (SIC) as a gate dielectric, and we can tune the carrier density of FeSe by driving lithium ions in and out of the FeSe thin flakes, and consequently control the material properties and its phase transitions. A dome-shaped superconducting phase diagram was mapped out with increasing Li content, with $T_c$ $\sim$ 46.6 K for the optimal doping, and an insulating phase was reached at the extremely overdoped regime. Our study suggests that, using solid ion conductor as a gate dielectric, the SIC-FET device can achieve much higher carrier doping in the bulk, and suit many surface sensitive experimental probes, and can stabilize novel structural phases that are inaccessible in ordinary conditions.

We present a systematic analysis of two-pion interferometry in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV using the STAR detector at RHIC. We extract the HBT radii and study their multiplicity, transverse momentum, and azimuthal angle dependence. The Gaussianess of the correlation function is studied. Estimates of the geometrical and dynamical structure of the freeze-out source are extracted by fits with blast wave parameterizations. The expansion of the source and its relation with the initial energy density distribution is studied.

We report on mid-rapidity mass spectrum of di-electrons and cross sections of pseudoscalar and vector mesons via $e^{+}e^{-}$ decays, from $\sqrt{s} = 200$ GeV $p+p$ collisions, measured by the large acceptance experiment STAR at RHIC. The ratio of the di-electron continuum to the combinatorial background is larger than 10% over the entire mass range. Simulations of di-electrons from light-meson decays and heavy-flavor decays (charmonium and open charm correlation) are found to describe the data. The extracted $\omega\rightarrow e^{+}e^{-}$ invariant yields are consistent with previous measurements. The mid-rapidity yields ($dN/dy$) of $\phi$ and $J/\psi$ are extracted through their di-electron decay channels and are consistent with the previous measurements of $\phi\rightarrow K^{+}K^{-}$ and $J/\psi\rightarrow e^{+}e^{-}$. Our results suggest a new upper limit of the branching ratio of the $\eta \rightarrow e^{+}e^{-}$ of $1.7\times10^{-5}$ at 90% confidence level.

We report new results on identified (anti)proton and charged pion spectra at large transverse momenta (3<$p_{T}$<10 GeV/c) from Cu+Cu collisions at $\sqrt{s_{NN}}$=200 GeV using the STAR detector at the Relativistic Heavy Ion Collider (RHIC). This study explores the system size dependence of two novel features observed at RHIC with heavy ions: the hadron suppression at high-$p_{T}$ and the anomalous baryon to meson enhancement at intermediate transverse momenta. Both phenomena could be attributed to the creation of a new form of QCD matter. The results presented here bridge the system size gap between the available pp and Au+Au data, and allow the detailed exploration for the on-set of the novel features. Comparative analysis of all available 200 GeV data indicates that the system size is a major factor determining both the magnitude of the hadron spectra suppression at large transverse momenta and the relative baryon to meson enhancement.

The density distributions of large nuclei are typically modeled with a Woods-Saxon distribution characterized by a radius $R_{0}$ and skin depth $a$. Deformation parameters $\beta$ are then introduced to describe non-spherical nuclei using an expansion in spherical harmonics $R_{0}(1+\beta_2Y^0_2+\beta_4Y^0_4)$. But when a nucleus is non-spherical, the $R_{0}$ and $a$ inferred from electron scattering experiments that integrate over all nuclear orientations cannot be used directly as the parameters in the Woods-Saxon distribution. In addition, the $\beta_2$ values typically derived from the reduced electric quadrupole transition probability B(E2)$\uparrow$ are not directly related to the $\beta_2$ values used in the spherical harmonic expansion. B(E2)$\uparrow$ is more accurately related to the intrinsic quadrupole moment $Q_{0}$ than to $\beta_2$. One can however calculate $Q_0$ for a given $\beta_2$ and then derive B(E2)$\uparrow$ from $Q_0$. In this paper we calculate and tabulate the $R_0$, $a$, and $\beta_2$ values that when used in a Woods-Saxon distribution, will give results consistent with electron scattering data. We then present calculations of the eccentricity $\varepsilon_2$ and $\varepsilon_3$ with the new and old parameters. We demonstrate that $\varepsilon_3$ is particularly sensitive to $a$ and argue that using the incorrect value of $a$ has important implications for the extraction of $\eta/s$ from the QGP created in Heavy Ion collisions.

The quark-gluon matter produced in relativistic heavy-ion collisions may contain local domains in which P and CP symmetries are not preserved. When coupled with an external magnetic field, such P- and CP-odd domains will generate electric currents along the magnetic field --- a phenomenon called the chiral magnetic effect (CME). Recently, the STAR Collaboration at RHIC and the ALICE Collaboration at the LHC released data of charge-dependent azimuthal-angle correlators with features consistent with the CME expectation. However, the experimental observable is contaminated with significant background contributions from elliptic-flow-driven effects, which makes the interpretation of the data ambiguous. In this Letter, we show that the collisions of isobaric nuclei, $^{96}_{44}$Ru + $^{96}_{44}$Ru and $^{96}_{40}$Zr + $^{96}_{40}$Zr, provide an ideal tool to disentangle the CME signal from the background effects. Our simulation demonstrates that the two collision types at $\sqrt{s_{\rm NN}}=200$ GeV have more than $10\%$ difference in the CME signal and less than $2\%$ difference in the elliptic-flow-driven backgrounds for the centrality range of $20-60\%$.

Elliptic flow ($v_{2}$) values for identified particles at mid-rapidity in Au+Au collisions, measured by the STAR experiment in the Beam Energy Scan at RHIC at $\sqrt{s_{NN}}=$ 7.7--62.4 GeV, are presented. A beam-energy dependent difference of the values of $v_{2}$ between particles and corresponding anti-particles was observed. The difference increases with decreasing beam energy and is larger for baryons compared to mesons. This implies that, at lower energies, particles and anti-particles are not consistent with the universal number-of-constituent-quark (NCQ) scaling of $v_{2}$ that was observed at $\sqrt{s_{NN}}=$ 200 GeV.

The PandaX-II experiment employed a 580kg liquid xenon detector to search for the interactions between dark matter particles and the target xenon atoms. The accidental coincidences of isolated signals result in a dangerous background which mimic the signature of the dark matter. We performed a detailed study on the accidental coincidence background in PandaX-II, including the possible origin of the isolated signals, the background level and corresponding background suppression method. With a boosted-decision-tree algorithm, the accidental coincidence background is reduced by 70% in the dark matter signal region, thus the sensitivity of dark matter search at PandaX-II is improved.

Microstructure characterization is of great value to understanding nuclear graphite's properties and irradiation behavior. However, graphite is soft and could be easily damaged during sample preparation. A three-step polishing method involving mechanical polishing, ion milling and rapid oxidation is proposed for graphite. Ion milling is adopted to remove the broken graphite pieces produced by mechanical polishing. Rapid oxidation is then adopted to remove irradiation-induced damage layer during ion milling. The Raman spectra show very low G peak width and ID/IG ratio after rapid oxidation, indicating a surface completely free from artificial defects. The micro-cracks which were conventionally observed via a transmission electron microscope can be observed on rapid-oxidized surface in a scanning electron microscope. By digital image processing, the micro-cracks along with the gas-escape pores in nuclear graphite IG-110 are statistically analyzed. Porosity's distributions on crack (pore) size (spanning from 10 nm to 100 um) are given, which could help to understand and simulate graphite's performances in reactors.