ترغب بنشر مسار تعليمي؟ اضغط هنا

Properties of Valence Nucleon Distributions for Halo Nuclei

106   0   0.0 ( 0 )
 نشر من قبل Cheng-Jian Lin
 تاريخ النشر 2002
  مجال البحث
والبحث باللغة English




اسأل ChatGPT حول البحث

With the binding energies and configurations determined experimentally, the root-mean-square radii are calculated for a number of single-particle states by numerically solving the Sch{o}rdinger equations. By studying the relations between the radii and separation energies, the new scaling laws and necessary conditions for neutron halos and proton halos are established, respectively. Especially the existence region of true proton halos is pointed out. It is found that the effects of short-distance behaviours of valence nucleons at the edges of interaction potentials can not be disregarded. Moreover, by means of the radii of interaction potentials, the contributions of outer parts are estimated as the criterions of halos.



قيم البحث

اقرأ أيضاً

40 - J. Wurzer , H. M. Hofmann 1997
The halo nuclei $^6$He and $^8$He are described in a consistent way in a microscopic multiconfiguration model, the refined resonating group method. The ground state properties have been calculated, and momentum distributions of fragments and neutrons have been determined in a simple reaction scenario, taking into account final-state interactions. The correlation of neutrons and fragments are investigated.
Realistic NN interactions and many-body approaches have been used to calculate ground-state properties of nuclei with A=3, 4, 12, 16, 40, with particular emphasis on various kinds of momentum distributions. It is shown that at proper values of the re lative (rel) and center-of-mass (c.m.) momenta, the two-nucleon momentum distribution n_A^{N_1N_2} (k_{rel}, K_{c.m.}, theta) exhibits the property of factorization, namely n_A^{N_1N_2} (k_{rel}, K_{c.m.}, theta) simeq n_{rel}(k_{rel}) n_(c.m.)( K{c.m.}). The factorization of the momentum distributions , bearing a universal character, results from a general property of realistic nuclear wave functions, namely their factorization at short inter-nucleon separations. The factorization of the two-nucleon momentum distribution allows one to develop the correlated part of the nucleon spectral function P(k,E) in terms of a convolution integral involving the product of the many-body, parameter-free relative and c.m. momentum distributions of a given nucleus. It is shown that: (i) the obtained spectral function perfectly satisfies the momentum sum rule, i.e. when it is integrated over the removal energy E, it fully reproduces the momentum distributions obtained from realistic many-body wave functions , (ii) in order to saturate the momentum sum rule at high values of the momentum (k simeq 5 fm^{-1}) the spectral function has to be integrate up to E simeq 400 MeV. To sum up a realistic, parameter-free many-body Spectral function has been developed such that : i) a phenomenological convolution spectral function developed in the past is fully justified from a many-body point of view , and (ii) the model dependence which might be present in calculations of inclusive electroweak processes could be reduced by the use of the convolution spectral function developed here.
135 - M. Alvioli 2012
Universality of short range correlations has been investigated both in coordinate and in momentum space, by means of one-and two-body densities and momentum distributions. In this contribution we discuss one- and two-body momentum distributions acros s a wide range of nuclei and their common features which can be ascribed to the presence of short range correlations. Calculations for few-body nuclei, namely 3He and 4He, have been performed using exact wave functions obtained with Argonne nucleon-nucleon interactions, while the linked cluster expansion technique is used for medium-heavy nuclei. The center of mass motion of a nucleon-nucleon pair in the nucleus, embedded in the full two-body momentum distribution n_NN(krel,KCM), is shown to exhibit the universal behavior predicted by the two-nucleon correlation model, in which the nucleon-nucleon pair moves inside the nucleus as a deuteron in a mean-field. Moreover, the deuteron-like spin-isospin (ST)=(10) contribution to the pn two-body momentum distribution is obtained, and shown to exactly scale to the deuteron momentum distribution. Universality of correlations in two-body distributions is cast onto the one-body distribution n(k1), obtained by integration of the two-body n_NN(k1, k2): in particular, the high momentum part of n(k1) exhibits the same pattern for all considered nuclei, in favor of a universal character of the short range structure of the nuclear wave function. Perspectives of this work, namely the calculation of reactions involving light and complex nuclei with realistic wave functions and effects of Final State Interactions (FSI), investigated by means of distorted momentum distributions within the Glauber multiple scattering approach, are eventually discussed.
By analyzing recent microscopic many-body calculations of few-nucleon systems and complex nuclei performed by different groups in terms of realistic nucleon-nucleon (NN) interactions, it is shown that NN short-range correlations (SRCs) have a univers al character, in that the correlation hole that they produce in nuclei appears to be almost A-independent and similar to the correlation hole in the deuteron. The correlation hole creates high-momentum components, missing in a mean-field (MF) description and exhibiting several scaling properties and a peculiar spin-isospin structure. In particular, the momentum distribution of a pair of nucleons in spin-isospin state $(ST)=(10)$, depending upon the pair relative ($k_{rel}$) and center-of-mass (c.m.) ($K_{c.m.}$) momenta, as well as upon the angle $Theta$ between them, exhibits a remarkable property: in the region $k_{rel}gtrsim 2,fm^{-1}$ and $K_{c.m.}lesssim 1,fm^{-1} $, the relative and c.m. motions are decoupled and the two-nucleon momentum distribution factorizes into the deuteron momentum distribution and an A-dependent momentum distribution describing the c.m. motion of the pair in the medium. The impact of these and other properties of one- and two-nucleon momentum distributions on various nuclear phenomena, on ab initio calculations in terms of low-momentum interactions, as well as on ongoing experimental investigations of SRCs, are briefly commented.
We consider two competing sets of nuclear magic numbers, namely the harmonic oscillator (HO) set (2, 8, 20, 40, 70, 112, 168, 240,...) and the set corresponding to the proxy-SU(3) scheme, possessing shells 0-2, 2-4, 6-12, 14-26, 28-48, 50-80, 82-124, 126-182, 184-256... The two sets provide 0+ bands with different deformation and band-head energies. We show that for proton (neutron) numbers starting from the regions where the quadrupole-quadrupole interaction, as derived by the HO, becomes weaker than the one obtained in the proxy-SU(3) scheme, to the regions of HO shell closure, the shape coexistence phenomenon may emerge. Our analysis suggests that the possibility for appearance of shape coexistence has to be investigated in the following regions of proton (neutron) numbers: 8, 18-20, 34-40, 60-70, 96-112, 146-168, 210-240,...
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا