Possible CP-violation effects in core-collapse supernovae

We study CP-violation effects when neutrinos are present in dense matter, such as outside the proto-neutron star formed in a core-collapse supernova. Using general arguments based on the Standard Model, we confirm that there are no CP-violating effects at the tree level on the electron neutrino and anti-neutrino fluxes in a core-collapse supernova. On the other hand significant effects can be obtained for muon and tau neutrinos even at the tree level. We show that CP-violating effects can be present in the supernova electron (anti-)neutrino fluxes as well, if muon and tau neutrinos have different fluxes at the neutrinosphere. Such differences could arise due to physics beyond the Standard Model, such as the presence of flavor-changing interactions.     

Re-research on the size of proto-neutron star in core-collapse supernova

The electron capture timescale may be shorter than hydrodynamic timescale in inner iron core of core-collapse supernova according to a recent new idea. Based on the new idea, this paper carries out a numerical simulation on supernova explosion for the progenitor model Ws15M. The numerical result shows that the size of proto-neutron star has a significant change （decrease about 20%）, which may affects the propagation of the shock wave and the final explosion energy.     

超新星的前身星阶段fp壳层的电子俘获

基于核的壳层模型，本文讨论了大质量恒星的超新星前身星阶段核的fp壳层电子俘获，分析中引入了一高斯函数来表征Gamow-Teller跃迁强度分布，结果表明，由于这一修正，在高密度下，电子俘获率较前人给出的结果有较大幅度的增加。     

Detection of supernova neutrinos at spallation neutron sources

After considering supernova shock effects, Mikheyev-Smirnov-Wolfenstein effects, neutrino collective effects, and Earth matter effects, the detection of supernova neutrinos at the China Spallation Neutron Source is studied and the expected numbers of different flavor supernova neutrinos observed through various reaction channels are calculated with the neutrino energy spectra described by the Fermi-Dirac distribution and the "beta fit"distribution respectively. Furthermore, the numerical calculation method of supernova neutrino detection on Earth is applied to some other spallation neutron sources, and the total expected numbers of supernova neutrinos observed through different reactions channels are given.     

超新星爆发环境核素56,57,59,60Co的电子俘获

基于壳模型与Random Phase Approximation理论, 利用Shell-Model Monte Carlo方法, 研究了超新星爆发环境核素^56,57,59,60Co的电子俘获与电子丰度变化率. 我们的结果与利用Aufderheide方法计算的结果进行了误差对比. 结果表明: 电子俘获率受温度和密度的影响大大增加, 甚至增加达6个数量级以上(如在ρ₇=0.43, Y_e=0.48核素^57,59,60Co). 另一方面, 随着温度和密度的增大, 电子丰度变化率大大降低, 甚至减小达5个数量级以上(如在ρ₇=5.86, Y_e=0.47核素⁵⁹Co). 通过对误差因子的分析表明, 在低温低密度环境二种结果误差较大; 而在高温高密度环境, 二种结果误差相对较小. 关键词： 电子俘获 超新星     

Relevance of thermally populated first excited state of 44Ti to the abundance problem of cassiopiea A: A model study

We examine the possible role of electron-capture on the thermally populated first 2⁺ excited state of ⁴⁴Ti in hot astrophysical environments pertaining to post explosive nucleosynthesis supernova debris. We find in a simple schematic model that the astrophysical weak interaction rate for electron-capture decay of ⁴⁴Ti can depend considerably on temperature and hence on time. We propose a time varying decay rate for the evolving supernova debris and demonstrate its consequence for the ⁴⁴Ti mass yield of the supernova Cas A, observed through the measured 1.157 MeV γ-ray flux from the electron-capture decay of ⁴⁴Ti.     

Investigating the abundance enrichment pattern of heavy elements in the only observed CEMP-r/s star J004441.04-732136.4 of the SMC

The post-AGB star J004441 is the first and the only one CEMP-r/s star found in SMC.Herein,we investigate the observed abundance pattern of the heavy elements using our parametric model.A consistent fitting results was obtained for the sample star.Based on the low r=0.08,the s-process nucleosynthesis occurred in the interior is supposed to belong to the single neutron-exposure event.The median value ofτ0=0.44(T90.348)1/2mbarn-1supports a higher efficiency of the s-process nucleosynthesis relative to J004441 than that of the solar system,however,the value is not sufficiently high to favor the formation of a lead star.Thus,J004441does not belong to lead star group.The large Csvalue of J004441 supports the intrinsic characteristic of the s-enrichment.The Crvalue is similar with that found in halo CEMP-r/s stars,which indicates that the r-process contributions is critical during heavy element enrichment.This star has a metallicity of[Fe/H]=-1.34,which is larger than that of Galaxy halo CEMP-r/s stars.The reason may be because of the different history of metallicity enrichment between the SMC and the Galaxy halo.     

Effect of pressure grads on convection in inner core of type II supernova

By adjusting the pressure grads in the stage of formation of the shock wave, a successful prompt explosion process has been numerically simulated through a progenitor model of 15Msolar, in which the effects of pressure grads on various convections, including the Rayleigh-Taloy （R-T） convection, the lepton driven convection and the negative entropy grads driven convection, in an inner core are analysed. The simulation results showthat the increase of the pressure grads in the inner core region may cause a powerful convection, which causes energy transfer from the inner core to the shock wave rapidly and efficiently.     

Nuclear Masses and the r- and p-Processes of Nucleosynthesis

Although important efforts have been devoted in the last decades to measure atomic masses, the modelling of the r- and p-processes of nucleosynthesis still requires the use of theoretical predictions to estimate experimentally unknown masses in the neutron-rich and neutron-deficient regions. Different mass models are available to extrapolate nuclear masses far away from the experimentally known region. These models are compared and used to estimate the reaction rates of relevance in the r- and p-processes. The impact of the different mass models on the astrophysics predictions are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

实验室模拟研究超新星遗迹演化动力学过程

文章详细分析讨论了超新星遗迹演化过程中冲击波动力学过程以及激光等离子体喷流的动力学的特点,阐述了利用激光等离子体实验产生与超新星遗迹演化动力学类似的冲击波结构来模拟研究超新星遗迹动力学与演化过程.这些分析与讨论对于实验室利用高能激光模拟研究超新星遗迹演化动力学过程具有重要的意义.     

Spectral hardening of cosmic ray protons and helium nuclei in supernova remnant shocks

The observed hardening of the spectra of cosmic ray protons and helium nuclei is studied within the model of nonlinear diffusive shock acceleration of supernova remnants(SNRs). In this model, the injected particles with energies below the spectral "knee" are assumed to be described by two populations with different spectral indexes around 200 GeV. The high-energy population is dominated by the particles with energies above 200 GeV released upstream of the shock of SNR, and the low-energy population is attributed to the particles with energies below 200 GeV released downstream of the shock of SNR. In this scenario, the spectral hardening of cosmic ray protons and helium nuclei observed by PAMELA, AMS-02, and CREAM experiments can be reproduced.     

The mass effect of the quark phase transition in supernova core

Constituent quark mass model is adopted as a tentative one to study the phase transition between two-flavour quark matter and more stable three-flavour quark matter in the core of supernovae. The result shows that the transition has a significant influence on the increasing of the core temperature, the neutrino abundance and the neutrino energies, which contributes to the enhancement of the successful probability of supernova explosion. However, the equilibrium values of these parameters （except the temperature） from the constituent quark mass model in this work are slightly bigger than those obtained from the other model. And we find that the constituent quark mass model is also applicable to describing the transition in the supernova core.     

On the possibility to determine neutrino mass hierarchy via supernova neutrinos with short-time characteristics

In this paper, we investigate whether it is possible to determine the neutrino mass hierarchy via a high-statistics and real-time observation of supernova neutrinos with short-time characteristics. The essential idea is to utilize distinct times-of-flight for different neutrino mass eigenstates from a core-collapse supernova to the Earth, which may significantly change the time distribution of neutrino events in the future huge water-Cherenkov and liquid-scintillator detectors. For illustration, we consider two different scenarios. The first case is the neutronization burst of emitted in the first tens of milliseconds of a core-collapse supernova, while the second case is the black hole formation during the accretion phase for which neutrino signals are expected to be abruptly terminated. In the latter scenario, it turns out only when the supernova is at a distance of a few Mpc and the fiducial mass of the detector is at the level of gigaton, might we be able to discriminate between normal and inverted neutrino mass hierarchies. In the former scenario, the probability for such a discrimination is even less due to a poor statistics.     

电荷屏蔽对Ⅱ型超新星瞬时爆发能量的影响

讨论了电荷屏蔽效应对WS15M_⊙前身星模型瞬时爆发能量的影响,对电子俘获率的计算基于平均重核模型,数值模拟表明电荷屏蔽降低了电子俘获率,延长了爆发时间,使中微子泄漏的总能量增加,从而导致激波的能量略微降低.给出的方法可以适用于其他考虑电荷屏蔽效应的超新星数值模拟. 关键词： 超新星 瞬时爆发 数值模拟 电荷屏蔽     

超新星核中的夸克相变及夸克质量效应

分别基于组夸克质量模型和流夸克质量模型, 讨论了超新星核心区两味夸克物质到更稳定的三味夸克物质的相变过程. 结果表明, 两种质量模型下相变的特征时标都短于10^-8s, 且质量越小的流夸克质量模型的相变速率越快;组分夸克质量模型下所得到的超新星核区的s夸克丰度, 中微子丰度及中微子总能量(除温度)相比前人的结果有轻微的增加, 而流夸克质量模型下所得到的这些参量的增加更为明显, 采用流夸克质量模型更有利于超新星的中微子延迟爆发机理的成功. 关键词： 夸克相变 组分夸克质量 流夸克质量 超新星     

Nuclear matter at high density: Phase transitions,multiquark states,and supernova outbursts

Phase transition from hadronic matter to quark-gluon matter is discussed for various regimes of temperature and baryon number density. For small and medium densities, the phase transition is accurately described in the framework of the Field Correlation Method, whereas at high density predictions are less certain and leave room for the phenomenological models. We study formation of multiquark states (MQS) at zero temperature and high density. Relevant MQS components of the nuclear matter can be described using a previously developed formalism of the quark compound bags (QCB). Partialwave analysis of nucleon-nucleon scattering indicates the existence of 6QS which manifest themselves as poles of P matrix. In the framework of the QCB model, we formulate a self-consistent system of coupled equations for the nucleon and 6QS propagators in nuclear matter and the G matrix. The approach provides a link between high-density nuclear matter with the MQS components and the cumulative effect observed in reactions on the nuclei, which requires the admixture of MQS in the wave functions of nuclei kinematically. 6QS determines the natural scale of the density for a possible phase transition into theMQS phase of nuclear matter. Such a phase transition can lead to dynamic instability of newly born protoneutron stars and dramatically affect the dynamics of supernovae. Numerical simulations show that the phase transition may be a good remedy for the triggering supernova explosions in the spherically symmetric supernovamodels. A specific signature of the phase transition is an additional neutrino peak in the neutrino light curve. For a Galactic core-collapse supernova, such a peak could be resolved by the present neutrino detectors. The possibility of extracting the parameters of the phase of transition from observation of the neutrino signal is discussed also.     

Resonant nuclear reaction ~(23)Mg(p,γ) ~(24)Al in strongly screening magnetized neutron star crust

Based on the relativistic theory of superstrong magnetic fields(SMF), by using three models those of Lai(LD), Fushiki(FGP), and our own(LJ), we investigate the influence of SMFs due to strong electron screening(SES) on the nuclear reaction ~(23)Mg(p,γ) ~(24)Al in magnetars. In a relatively low density environment(e.g., ρ_7 0.01)and 1 B_(12) 10~2, our screening rates are in good agreement with those of LD and FGP. However, in relatively high magnetic fields(e.g., B_(12) 10~2), our reaction rates can be 1.58 times and about three orders of magnitude larger than those of FGP and LD, respectively(B_(12), ρ~7 are in units of 10~(12)G, 10~7 g cm~(-3)). The significant increase of strong screening rate can imply that more ~(23)Mg will escape from the Ne-Na cycle due to SES in a SMF. As a consequence,the next reaction, ~(24)Al(+β, ν) ~(24)Mg, will produce more ~(24)Mg to participate in the Mg-Al cycle. Thus, it may lead to synthesis of a large amount of A20 nuclides in magnetars.