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《Nuclear Physics A》1988,489(4):763-780
Charged pions have been measured at 70° in coincidence with projectile-like fragments in 12C + 12C, 12C + 116Sn and 12C + 124Sn reactions at 85A MeV. Neither the π+ emission nor the π−/π+ ratio exhibit differences for 124Sn and 116Sn targets outside those expected from the isospin difference. Inconsistencies in the target mass dependence of the pion yield disappear if a correction for reabsorption is included. After this correction, we observe a strong, ~ A1.1, mass dependence. The projectile breakup is significantly stronger for pion-producing collisions than for the average collision indicating a much stronger abundance of central collisions. 相似文献
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利用同位旋相关的量子分子动力学模型,研究了112Sn+112Sn和124Sn+124Sn两反应系统在不同入射能量、不同碰撞参数、不同势场和不同核子-核子碰撞截面下的粒子发射特征.阐述了发射体系的同位旋对轻粒子产额比的影响.发现轻粒子产额比是同位旋的敏感观测量.另外,还发现中快度区发射的粒子有更高的丰中子程度.同时,轻粒子的比不敏感于核子核子碰撞截面,而敏感于核态方程,这使得从轻粒子比提取同位旋相关的核态方程变成一种可能.
关键词:
同位旋相关的量子分子动力学
同位旋效应
轻粒子产额比 相似文献
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Tsang MB Liu TX Shi L Danielewicz P Gelbke CK Liu XD Lynch WG Tan WP Verde G Wagner A Xu HS Friedman WA Beaulieu L Davin B de Souza RT Larochelle Y Lefort T Yanez R Viola VE Charity RJ Sobotka LG 《Physical review letters》2004,92(6):062701
Using symmetric 112Sn+112Sn, 124Sn+124Sn collisions as references, we probe isospin diffusion in peripheral asymmetric 112Sn+124Sn, 124Sn+112Sn systems at an incident energy of E/A=50 MeV. Isoscaling analyses imply that the quasiprojectile and quasitarget in these collisions do not achieve isospin equilibrium, permitting an assessment of isospin transport rates. We find that comparisons between isospin sensitive experimental and theoretical observables, using suitably chosen scaled ratios, permit investigation of the density dependence of the asymmetry term of the nuclear equation of state. 相似文献
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The isospin effect in peripheral heavy-ion collisions was thoroughly investigated within the framework of the Lanzhou quantum molecular dynamics (LQMD) transport model. A coalescence approach was used to recognize the primary fragments formed in nucleus-nucleus collisions. The secondary decay process of these fragments was described using the statistical code GEMINI. The production mechanism and isospin effect of the projectile-like and target-like fragments were analyzed using the combined approach. It was found that the isospin migration from the high-isospin density to the low-density matter occurred in the neutron-rich nuclear reactions, i.e., 48Ca+208Pb, 86Kr+48Ca/208Pb/124Sn, 136Xe+208Pb, 124Sn+124Sn, and 136Xe+136Xe. A hard symmetry energy was available for creating the neutron-rich fragments, particularly in the medium-mass region. The isospin effect of the neutron-to-proton (n/p) ratio of the complex fragments was reduced when the secondary decay process was included. However, a soft symmetry energy enhanced the n/p ratio of the light particles, particularly at kinetic energies greater than 15 MeV/nucleon. 相似文献
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J. Rapaport Mohammed Mirzaa H. Hadizadeh D.E. Bainum R.W. Finlay 《Nuclear Physics A》1980,341(1):56-74
Accurate measurements of neutron differential elastic cross sections have been obtained from even isotopes of Sn. Data are presented for the elastic scattering of 11 MeV neutrons from 116, 118, 120, 122, 124Sn, the elastic scattering for 24 MeV neutrons from 116, 118, 124Sn and the neutron total cross section from 118, 120, 122, 124Sn in the energy ranges 5.0–10.6 MeV and 20.0–26.0 MeV. The elastic scattering data are analyzed in terms of an empirical optical-model potential. The obtained optical-potential parameters are analyzed in terms of energy and isospin dependence and compared with those obtained from proton elastic scattering on even Sn isotopes. 相似文献
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Isospin splitting of nucleon effective mass and symmetry energy in isotopic nuclear reactions
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Ya-Fei Guo Peng-Hui Chen Fei Niu Hong-Fei Zhang Gen-Ming Jin Zhao-Qing Feng 《中国物理C(英文版)》2017,41(10):104104-104104
Within an isospin and momentum dependent transport model, the dynamics of isospin particles(nucleons and light clusters) in Fermi-energy heavy-ion collisions are investigated for constraining the isospin splitting of nucleon effective mass and the symmetry energy at subsaturation densities. The impacts of the isoscalar and isovector parts of the momentum dependent interaction on the emissions of isospin particles are explored, i.e., the mass splittings of m_n~*=m_p~* and m_n~* m_p~*(m_n~* m_p~*). The single and double neutron to proton ratios of free nucleons and light particles are thoroughly investigated in the isotopic nuclear reactions of ~(112)Sn+~(112)Sn and ~(124)Sn+~(124)Sn at incident energies of 50 and 120 MeV/nucleon, respectively. It is found that both the effective mass splitting and symmetry energy impact the kinetic energy spectra of the single ratios, in particular at the high energy tail(larger than 20 Me V). The isospin splitting of nucleon effective mass slightly impacts the double ratio spectra at the energy of 50 MeV/nucleon. A soft symmetry energy with stiffness coefficient of γ_s =0.5 is constrained from the experimental data with the Fermi-energy heavy-ion collisions. 相似文献
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Isospin Effect on Relative State Population Temperature in the Reactions 40Ar+ 112,124Sn at 30MeV/u
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HU Rong-Jiang WU He-Yu ZHU Yong-Tai JIN Gen-Ming DUAN Li-Min XIAO Zhi-Gang WANG Hong-Wei LI Zu-Yu WANG Su-Fang ZHANG Bao-Guo WEI Zhi-Yong LU Zhao-Hui ZHU Hai-Dong FENG Zhao-Qing YUAN Xiao-Hua 《中国物理C(英文版)》2004,28(2):152-157
An array of 13 detector telescopes has been used for detecting small-angle particle-particle correlations in the reactions 40Ar+112,124Sn at 30MeV/u. The α-α correlation functions were extracted from two-particle coincident events. A three-body trajectory code MENEKA was used to calculate the background correlation function. The detection efficiency was calculated by using the Monte-Carlo method. After subtracting the background correlation and making the detection efficiency correction, the temperatures of 4.18±0.25 0.21 MeV and 4.10±0.22 0.20MeV are obtained from relative populations of 8Be states for the reaction systems with different isospin,40Ar+112Sn and 40Ar+124Sn, respectively. From the relationship between the state population temperature and outgoing particle energies, it is found that the emission temperature decreases with increase of the particle energies for both studied reaction systems. For the neutron deficient system 40Ar+112Sn the emission temperature is 5.13±0.30 0.26MeV for the lower emitting particle energies and 3.87±0.37 0.29MeV for the higher emitting particle energies. And for the neutron rich system 40Ar+124Sn the emission temperature is 5.39±0.30 0.26MeV for the lower emitting particle energies and 3.32± 0.28 0.23MeV for the higher emitting particle energies. This kind of isospin dependence is discussed. 相似文献
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H.Y. Zhang W.Q. Shen Y.G. Ma X.Z. Cai D.Q. Fang L.P. Yu C. Zhong Y.B. Wei 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):399-404
The directed and elliptic flows for different light particles and fragments in collisions of 40Ca + 40Ca and 112Sn + 112Sn at energies from 30MeV/nucleon to 100MeV/nucleon were studied in the isospin-dependent quantum molecule dynamics model
(IQMD). With increasing incident energy, the directed flow rises from negative to positive, while the elliptic flow decreases
with increasing the incident energies. The directed flow for the 40Ca + 40Ca system is not sensitive to the nuclear equation of states (EOS), but the directed flow for the 112Sn + 112Sn system is sensitive to the EOS. However, the elliptic flows for both 40Ca + 40Ca and 112Sn + 112Sn systems are not sensitive to EOS. A study of the dependence of directed and elliptic flows on the fragment charge (mass)
is also performed.
Received: 15 March 2002 / Accepted: 14 June 2002 / Published online: 19 November 2002
RID="a"
ID="a"e-mail: Zhanghy@sinr.ac.cn; Permanent address: Shanghai Institute of Nuclear Research, Chinese Academy of Sciences, P.O. Box 800-204(2), Shanghai 201800, China.
Communicated by W. Henning 相似文献
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XIAO Zhi-Gang WU He-Yu LI Zu-Yu JIN Gen-Ming WANG Hong-Wei DUAN Li-Min ZHANG Bao-Guo HU Rong-Jiang WEI Zhi-Yong LIU Yong-Ying WANG Su-Fang LU Zhao-Hui ZHU Yong-Tai ZHU Hai-Dong 《中国物理C(英文版)》2001,25(6):494-499
Isotope ratios,defined as the yield ratio of two isotopes with the same charge,were analyzed as a function of kinetic energy of outgoing particles at 20° in the reactions of 40Ar+112,124Sn and 5°in36Ar+112,124Sn at incident energy of 35MeV/u. Isotope ratios between the neutron-deficient isotopes and stable isotope increase with kinetic energy,while those between the neutron rich isotopes and stable isotope decrease. This different behavior was observed similar for both 112Sn and 124Sn targets. The isotope ratios show rather obvious target dependence at 20° and little target dependence at 5°. As the outgoing energy getting down,the N/Z ratio of the fragmentation products at 5° diverts gradually from the N/Z ratio of the projectile to that of the system. These observations indicate that the isospin degree of freedom does not reach complete equilibrium in the peripheral or semi-peripheral collision at this bombarding energy. 相似文献
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Using the isospin- and momentum-dependent hadronic transport model IBUU04, we have in-vestigated the influence of the entrance-channel isospin asymmetry on the sensitivity of the pre-equilibrium neutron/proton ratio to symmetry energy in central heavy-ion collisions induced by high-energy radioactive beams. Our analysis and discussion are based on the dynamical simulations of the three isotopic reaction systems 132Sn+124Sn, 124Sn+112Sn and 112Sn+112Sn which are of the same total proton number but different isospin asymmetry. We find that the kinetic-energy distributions of the pre-equilibrium neutron/proton ratio are quite sensitive to the density-dependence of symmetry energy at incident beam energy E/A = 400 MeV,and the sensitivity increases as the isospin asymmetry of the reaction system increases. 相似文献
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Effect of the momentum dependence of nuclear symmetry potential on the transverse and elliptic flows
Lei Zhang Yuan Gao Yun Du Guang-Hua Zuo Gao-Chan Yong 《The European Physical Journal A - Hadrons and Nuclei》2012,48(3):30
In the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, the effect of the momentum dependence
of nuclear symmetry potential on nuclear transverse and elliptic flows in the neutron-rich reaction 132Sn+124Sn at a beam energy of 400MeV/nucleon is studied. We find that the momentum dependence of nuclear symmetry potential affects
the rapidity distribution of the free neutron to proton ratio, the neutron and the proton transverse flows as a function of
rapidity. The momentum dependence of nuclear symmetry potential affects the neutron-proton differential transverse flow more
evidently than the difference of neutron and proton transverse flows as well as the difference of proton and neutron elliptic
flows. It is thus better to probe the symmetry energy by using the difference of neutron and proton flows since the momentum
dependence of nuclear symmetry potential is still an open question. And it is better to probe the momentum dependence of nuclear
symmetry potential by using the neutron-proton differential transverse flow the rapidity distribution of the free neutron
to proton ratio. 相似文献
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X.H. Zhou M. Oshima Y. Toh Y.H. Zhang Y. Zheng M. Koizumi A. Osa T. Hayakawa Y. Hatsukawa T. Shizuma M. Sugawara 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):285-289
Based on the systematic investigation of the data available for nuclei with A≥ 40, a Z
1/3-dependence for the nuclear charge radii is shown to be superior to the generally accepted A
1/3 law. A delicate scattering of data around R
c/Z
1/3 is inferred as owing to the isospin effect and a linear dependence of R
c/Z
1/3 on N/Z (or (N - Z)/2) is found. This inference is well supported by the microscopic Relativistic Continuum Hartree-Bogoliubov (RCHB) calculation
conducted for the proton magic Ca, Ni, Zr, Sn and Pb isotopes including the exotic nuclei close to the neutron drip line.
With the linear isospin dependence provided by the data and RCHB theory, a new isospin-dependent Z
1/3 formula for the nuclear charge radii is proposed.
Received: 23 September 2001 / Accepted: 21 January 2002 相似文献
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The isospin dependence, recently observed in Sn + Sn reactions at
40 MeV/nucleon, is discussed within the framework of two simple nuclear multifragmentation models, namely the site percolation and the nucleation-evaporation models. It is shown that both the models are able to discriminate between 112Sn+ 112Sn and 124Sn+ 124Sn reactions. The nucleation-evaporation model succeeds to
reproduce nicely the experimental data, but the site percolation model fails in doing that, even if the cluster
noncompactive effect is taken into account. The calculations indicate
that the data are originated mainly from
a single source. 相似文献
20.
Isospin Effect on the Emission Mechanism of Hot Nuclei in 35MeV/u 40Ar +112Sn/124Sn Reactions
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Wu Heyu Xiao Zhigang Li Zuyu Wang Hpmgweo Duan Limin Zhang Baoguo Liu Yongying Wang Sufang Jin Genming Xiao Guoqing Guo Zhongyan Zhu Yongtai 《中国物理C(英文版)》1999,23(11):1115-1118
As an extension of radioactive ion beam physics, the research on isospin dependent properties of hot nuclei has increasingly attracted considerable interest. The isospin effect on the decay of hot nuclei in reactions 35MeV/u 40Ar+112Sn/124Sn has been investigared. It is concluded that due to Coulomb repulsion and instability, proton-rich hot nuclei probably emit prides such as a with high energy to increase their neutron-proton ratio. Moreover, the decay chain for those particles is seemingly long and the emission Probability is high. Thus, the conventional observations, for instance, the ‘slope temperature’ extracted from energy spectrum, may very appreciably with the measured particles. 相似文献