Pub Date : 2001-01-22DOI: 10.1103/PhysRevC.63.061303
Jorge Dukelsky, S. Pittel
A new approach to large-scale nuclear structure calculations, based on the Density Matrix Renormalization Group (DMRG), is described. The method is tested in the context of a problem involving many identical nucleons constrained to move in a single large-j shell and interacting via a pairing plus quadrupole interaction. In cases in which exact diagonalization of the hamiltonian is possible, the method is able to reproduce the exact results for the ground state energy and the energies of low-lying excited states with extreme precision. Results are also presented for a model problem in which exact solution is not feasible.
{"title":"New approach to large-scale nuclear structure calculations","authors":"Jorge Dukelsky, S. Pittel","doi":"10.1103/PhysRevC.63.061303","DOIUrl":"https://doi.org/10.1103/PhysRevC.63.061303","url":null,"abstract":"A new approach to large-scale nuclear structure calculations, based on the Density Matrix Renormalization Group (DMRG), is described. The method is tested in the context of a problem involving many identical nucleons constrained to move in a single large-j shell and interacting via a pairing plus quadrupole interaction. In cases in which exact diagonalization of the hamiltonian is possible, the method is able to reproduce the exact results for the ground state energy and the energies of low-lying excited states with extreme precision. Results are also presented for a model problem in which exact solution is not feasible.","PeriodicalId":48700,"journal":{"name":"Physical Review C","volume":"32 1","pages":"061303"},"PeriodicalIF":3.1,"publicationDate":"2001-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74442118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1999-07-28DOI: 10.1103/PHYSREVC.60.054613
P. Sedyshev, P. Mohr, P. Mohr, H. Beer, H. Oberhummer, Yu. P. Popov, W. Rochow
At the Karlsruhe and T"ubingen 3.75 MV Van de Graaff accelerators the thermonuclear ${}^{50}mathrm{Ti}(n,ensuremath{gamma}{)}^{51}mathrm{Ti}(5.8mathrm{min})$ cross section was measured by the fast cyclic activation technique via the 320.852 and 928.65 keV $ensuremath{gamma}$-ray lines of the ${}^{51}mathrm{Ti}$ decay. Metallic Ti samples of natural isotopic composition and samples of ${mathrm{TiO}}_{2}$ enriched in ${}^{50}mathrm{Ti}$ by 67.53% were irradiated between two gold foils which served as capture standards. The capture cross section was measured at the neutron energies of 25, 30, 52, and 145 keV, respectively. The direct capture cross section was determined to be $0.387ifmmodepmelsetextpmfi{}0.011mathrm{mb}$ at 30 keV. We found evidence for a bound state s-wave resonance with an estimated radiative width of 0.34 eV which destructively interferes with direct capture. The strength of a suggested s-wave resonance at 146.8 keV was determined. The present data served to calculate, in addition to the directly measured Maxwellian averaged capture cross sections at 25 and 52 keV, an improved stellar ${}^{50}mathrm{Ti}(n,ensuremath{gamma}{)}^{51}mathrm{Ti}$ rate in the thermonuclear energy region from 1 to 250 keV. The new stellar rate leads at low temperatures to much higher values than the previously recommended rate; e.g., at $kT=8mathrm{keV}$ the increase amounts to about 50%. The new reaction rate therefore reduces the abundance of ${}^{50}mathrm{Ti}$ due to s processing in asymptotic giant branch stars.
{"title":"Measurement of neutron capture on 50 Ti at thermonuclear energies.","authors":"P. Sedyshev, P. Mohr, P. Mohr, H. Beer, H. Oberhummer, Yu. P. Popov, W. Rochow","doi":"10.1103/PHYSREVC.60.054613","DOIUrl":"https://doi.org/10.1103/PHYSREVC.60.054613","url":null,"abstract":"At the Karlsruhe and T\"ubingen 3.75 MV Van de Graaff accelerators the thermonuclear ${}^{50}mathrm{Ti}(n,ensuremath{gamma}{)}^{51}mathrm{Ti}(5.8mathrm{min})$ cross section was measured by the fast cyclic activation technique via the 320.852 and 928.65 keV $ensuremath{gamma}$-ray lines of the ${}^{51}mathrm{Ti}$ decay. Metallic Ti samples of natural isotopic composition and samples of ${mathrm{TiO}}_{2}$ enriched in ${}^{50}mathrm{Ti}$ by 67.53% were irradiated between two gold foils which served as capture standards. The capture cross section was measured at the neutron energies of 25, 30, 52, and 145 keV, respectively. The direct capture cross section was determined to be $0.387ifmmodepmelsetextpmfi{}0.011mathrm{mb}$ at 30 keV. We found evidence for a bound state s-wave resonance with an estimated radiative width of 0.34 eV which destructively interferes with direct capture. The strength of a suggested s-wave resonance at 146.8 keV was determined. The present data served to calculate, in addition to the directly measured Maxwellian averaged capture cross sections at 25 and 52 keV, an improved stellar ${}^{50}mathrm{Ti}(n,ensuremath{gamma}{)}^{51}mathrm{Ti}$ rate in the thermonuclear energy region from 1 to 250 keV. The new stellar rate leads at low temperatures to much higher values than the previously recommended rate; e.g., at $kT=8mathrm{keV}$ the increase amounts to about 50%. The new reaction rate therefore reduces the abundance of ${}^{50}mathrm{Ti}$ due to s processing in asymptotic giant branch stars.","PeriodicalId":48700,"journal":{"name":"Physical Review C","volume":"205 1","pages":"054613"},"PeriodicalIF":3.1,"publicationDate":"1999-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75561575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Wisshak, F. Voss, F. Käppeler, L. Kazakov, G. Reffo
The neutron capture cross sections of {sup 142}Nd, {sup 143}Nd, {sup 144}Nd, {sup 145}Nd, {sup 146}Nd, and {sup 148}Nd have been measured in the energy range from 3 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the {sup 7}Li(p,n){sup 7}Be reaction by bombarding metallic Li targets with a pulsed proton beam. Capture events were registered with the Karlsruhe 4{pi} Barium Fluoride Detector. The cross sections were determined relative to the gold standard. The experiment was difficult due to the small cross sections of the even isotopes at or near the magic neutron number N=82, and also since the isotopic enrichment of some samples was comparably low. The necessary corrections for capture of scattered neutrons and for isotopic impurities could be determined reliably thanks to the high efficiency and the spectroscopic quality of the BaF{sub 2} detector, resulting in a consistent set of (n,{gamma}) cross sections for the six stable neodymium isotopes involved in the s process with typical uncertainties of 1.5{endash}2{percent}. From these data, Maxwellian averaged cross sections were calculated between kT=10 and 100 keV. The astrophysical implications of these results were investigated in an s-process analysis, which deals with the rolemore » of the s-only isotope {sup 142}Nd for the N{sub s}{l_angle}{sigma}{r_angle} systematics near the magic neutron number N=82, the decomposition of the Nd abundances into the respective r-, s-, and p-process components, and the interpretation of isotopic anomalies in meteoritic material. {copyright} {ital 1998} {ital The American Physical Society}« less
{"title":"Stellar neutron capture cross sections of the Nd isotopes","authors":"K. Wisshak, F. Voss, F. Käppeler, L. Kazakov, G. Reffo","doi":"10.1103/PHYSREVC.57.391","DOIUrl":"https://doi.org/10.1103/PHYSREVC.57.391","url":null,"abstract":"The neutron capture cross sections of {sup 142}Nd, {sup 143}Nd, {sup 144}Nd, {sup 145}Nd, {sup 146}Nd, and {sup 148}Nd have been measured in the energy range from 3 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the {sup 7}Li(p,n){sup 7}Be reaction by bombarding metallic Li targets with a pulsed proton beam. Capture events were registered with the Karlsruhe 4{pi} Barium Fluoride Detector. The cross sections were determined relative to the gold standard. The experiment was difficult due to the small cross sections of the even isotopes at or near the magic neutron number N=82, and also since the isotopic enrichment of some samples was comparably low. The necessary corrections for capture of scattered neutrons and for isotopic impurities could be determined reliably thanks to the high efficiency and the spectroscopic quality of the BaF{sub 2} detector, resulting in a consistent set of (n,{gamma}) cross sections for the six stable neodymium isotopes involved in the s process with typical uncertainties of 1.5{endash}2{percent}. From these data, Maxwellian averaged cross sections were calculated between kT=10 and 100 keV. The astrophysical implications of these results were investigated in an s-process analysis, which deals with the rolemore » of the s-only isotope {sup 142}Nd for the N{sub s}{l_angle}{sigma}{r_angle} systematics near the magic neutron number N=82, the decomposition of the Nd abundances into the respective r-, s-, and p-process components, and the interpretation of isotopic anomalies in meteoritic material. {copyright} {ital 1998} {ital The American Physical Society}« less","PeriodicalId":48700,"journal":{"name":"Physical Review C","volume":"43 1","pages":"391-408"},"PeriodicalIF":3.1,"publicationDate":"1998-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88921688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Previous approaches to the photo- and electro-production of strangeness off the proton, based upon effective hadronic Lagrangians, are extended here to incorporate the so called off-shell effects inherent to the fermions with spin >= 3/2. A formalism for intermediate-state, spin 3/2, nucleonic and hyperonic resonances is presented and applied to the processes $gamma + p ---> K^{+} + Lambda$, for $E_{gamma}^{lab}$ e' + K^+ + Lambda$, as well as the branching ratio for the crossed channel reaction $K^- + p ---> gamma + Lambda$, with stopped kaons. The sensitivity, from moderate to significant, of various observables to such effects are discussed.
先前基于有效强子拉格朗日量的质子奇异性的光和电产生方法，在这里进行了扩展，以纳入自旋>= 3/2的费米子固有的所谓的脱壳效应。给出了中间态、自旋3/2、核子和超子共振的一种形式，并将其应用于$E_{gamma}^{lab}$ e' + K^+ + Lambda$的过程$gamma + p -> K^+ + Lambda$，以及具有停止介子的交叉通道反应$K^- + p -> gamma + Lambda$的分支比。讨论了各种观测值对这种效应的灵敏度，从中等到显著。
{"title":"Off-shell effects in the electromagnetic production of strangeness","authors":"T. Mizutani, C. Fayard, G. Lamot, B. Saghai","doi":"10.1103/PhysRevC.58.75","DOIUrl":"https://doi.org/10.1103/PhysRevC.58.75","url":null,"abstract":"Previous approaches to the photo- and electro-production of strangeness off the proton, based upon effective hadronic Lagrangians, are extended here to incorporate the so called off-shell effects inherent to the fermions with spin >= 3/2. A formalism for intermediate-state, spin 3/2, nucleonic and hyperonic resonances is presented and applied to the processes $gamma + p ---> K^{+} + Lambda$, for $E_{gamma}^{lab}$ e' + K^+ + Lambda$, as well as the branching ratio for the crossed channel reaction $K^- + p ---> gamma + Lambda$, with stopped kaons. The sensitivity, from moderate to significant, of various observables to such effects are discussed.","PeriodicalId":48700,"journal":{"name":"Physical Review C","volume":"51 1","pages":"75-90"},"PeriodicalIF":3.1,"publicationDate":"1997-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90512394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1995-01-16DOI: 10.1103/PhysRevC.51.2310 10.1103/PhysRevC.57.1004
M. Batinic, I. Slaus, A. Švarc, B. Nefkens
The ensuremath{pi}Nensuremath{rightarrow}ensuremath{eta}N and ensuremath{eta}Nensuremath{rightarrow}ensuremath{eta}N partial-wave T matrices for the eight lowest partial waves have been obtained in a three-coupled-channel model with unitarity manifestly imposed. The two physical channels are ensuremath{pi}N and ensuremath{eta}N, and the third channel, ensuremath{pi}ensuremath{pi}N is an effective, but unphysical two-body channel which represents all remaining processes. The ensuremath{pi}N elastic phase shifts and the weighted data base of the ensuremath{pi}Nensuremath{rightarrow}ensuremath{eta}N total and differential cross sections are chosen as the input for the fitting procedure. A model containing a single resonance in each of the three partial waves that dominates the ensuremath{eta} production at lower energies is compared with previous analyses, based on similar assumptions. A multiresonance coupled-channel model is introduced which significantly improves the agreement with all input data. Our results are compared with a complementary multiresonance coupled-channel analysis that is constrained with elastic and continuum production channels. The inclusion of the fourth ${mathit{P}}_{11}$ resonance in the 1440char21{}2200 MeV region further improves the agreement between the analysis and the data.
在具有明显的一致性的三耦合通道模型中，得到了8个最低部分波的ensuremath{pi} N ensuremath{rightarrow}ensuremath{eta} N和ensuremath{eta} N ensuremath{rightarrow}ensuremath{eta} N部分波T矩阵。两个物理通道分别是ensuremath{pi} N和ensuremath{eta} N，第三个通道ensuremath{pi}ensuremath{pi} N是一个有效但非物理的两体通道，代表所有剩余的进程。选择ensuremath{pi} N个弹性相移和ensuremath{pi} N ensuremath{rightarrow}ensuremath{eta} N总截面和微分截面的加权数据库作为拟合的输入。基于类似的假设，将在较低能量下主导ensuremath{eta}产生的三个部分波中的每一个都包含单个共振的模型与先前的分析进行比较。引入了一种多共振耦合通道模型，大大提高了与所有输入数据的一致性。我们的结果与互补的多共振耦合通道分析进行了比较，该分析受弹性和连续生产通道的约束。在1440 char 212200 MeV区域加入第四次${mathit{P}}_{11}$共振进一步提高了分析与数据之间的一致性。{}
{"title":"π N →η N and η N →η N partial-wave T matrices in a coupled, three-channel model","authors":"M. Batinic, I. Slaus, A. Švarc, B. Nefkens","doi":"10.1103/PhysRevC.51.2310 10.1103/PhysRevC.57.1004","DOIUrl":"https://doi.org/10.1103/PhysRevC.51.2310 10.1103/PhysRevC.57.1004","url":null,"abstract":"The ensuremath{pi}Nensuremath{rightarrow}ensuremath{eta}N and ensuremath{eta}Nensuremath{rightarrow}ensuremath{eta}N partial-wave T matrices for the eight lowest partial waves have been obtained in a three-coupled-channel model with unitarity manifestly imposed. The two physical channels are ensuremath{pi}N and ensuremath{eta}N, and the third channel, ensuremath{pi}ensuremath{pi}N is an effective, but unphysical two-body channel which represents all remaining processes. The ensuremath{pi}N elastic phase shifts and the weighted data base of the ensuremath{pi}Nensuremath{rightarrow}ensuremath{eta}N total and differential cross sections are chosen as the input for the fitting procedure. A model containing a single resonance in each of the three partial waves that dominates the ensuremath{eta} production at lower energies is compared with previous analyses, based on similar assumptions. A multiresonance coupled-channel model is introduced which significantly improves the agreement with all input data. Our results are compared with a complementary multiresonance coupled-channel analysis that is constrained with elastic and continuum production channels. The inclusion of the fourth ${mathit{P}}_{11}$ resonance in the 1440char21{}2200 MeV region further improves the agreement between the analysis and the data.","PeriodicalId":48700,"journal":{"name":"Physical Review C","volume":"3 1","pages":"2310"},"PeriodicalIF":3.1,"publicationDate":"1995-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88815479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dilepton production from pion-pion annihilation in a hot hadronic matter is studied using an effective chiral Lagrangian that includes explicitly vector mesons. We find that the production rate for dileptons with invariant masses around the {rho}-meson resonance is suppressed as a result of the modification of the pion electromagnetic form factor at finite temperature. The relevance of this phenomenon to the partial restoration of chiral symmetry in hot hadronic matter is discussed.
{"title":"Suppression of dilepton production in hot hadronic matter","authors":"Chung-sik Song, Su Houng Lee, C. Ko","doi":"10.1103/PhysRevC.52.476","DOIUrl":"https://doi.org/10.1103/PhysRevC.52.476","url":null,"abstract":"Dilepton production from pion-pion annihilation in a hot hadronic matter is studied using an effective chiral Lagrangian that includes explicitly vector mesons. We find that the production rate for dileptons with invariant masses around the {rho}-meson resonance is suppressed as a result of the modification of the pion electromagnetic form factor at finite temperature. The relevance of this phenomenon to the partial restoration of chiral symmetry in hot hadronic matter is discussed.","PeriodicalId":48700,"journal":{"name":"Physical Review C","volume":"52 1","pages":""},"PeriodicalIF":3.1,"publicationDate":"1994-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81312251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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