Resonance width distribution in RMT: Weak-coupling regime beyond Porter-Thomas

Fyodorov, Yan V.; Savin, Dmitry V.

doi:10.1209/0295-5075/110/40006

Cited by 25 publications

(35 citation statements)

References 60 publications

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“…Alternatively, using a realistic description of the coupling strength of the gamma channels, the width distribution for any number of gamma channels may be calculated using the analytic results of Ref. [6]. However, given the large number of channels, the evaluation of the formulas derived in Ref.…”

Section: Introductionmentioning

confidence: 99%

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Statistical-model description of γ decay from compound-nucleus resonances

2020

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The statistical model of compound-nucleus reactions predicts that the fluctuations of the partial gamma decay widths for a compound-nucleus resonance are governed by the Porter-Thomas distribution (PTD), and that consequently the distribution of total gamma-decay widths is very narrow. However, a recent experiment [1] reported large fluctuations of the total gamma-decay widths in the 95 Mo(n, γ) 96 Mo* reaction, contrary to this expectation. Furthermore, in recent theoretical works it was argued that sufficiently strong channel couplings can cause deviations of the partial width distributions from PTD. Here, we investigate whether the combined influence of a large number of nonequivalent gamma-decay channels, each of which couples weakly to the compound-nucleus resonances, can modify the statistics of the partial widths. We study this effect in neutron scattering off 95 Mo within a random-matrix model that includes coupling to the entrance neutron channel and to the large number of gamma channels. Using realistic coupling parameters obtained from empirical models for the level density and the gamma strength function, we find that the PTD describes well the distribution of partial widths for all decay channels, in agreement with the statistical-model expectation. Furthermore, we find that the width of the distribution of the total gamma-decay widths is insensitive to wide variations in the parameters of the gamma strength function, as well as to deviations of the partial-width distributions from the PTD. Our results rule out an explanation of the recent experimental data within a statistical-model description of the compound nucleus. arXiv:1909.06250v1 [nucl-th]

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Section: Introductionmentioning

confidence: 99%

“…However, given the large number of channels, the evaluation of the formulas derived in Ref. [6] is impractical. Therefore, it is not known yet whether the combined effect of a large number of weakly coupled gamma-decay channels in the 95 Mo(n, γ) 96 Mo* reaction might modify the distribution of the partial gamma-decay widths.…”

Section: Introductionmentioning

confidence: 99%

Statistical-model description of γ decay from compound-nucleus resonances

2020

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“…Mainly, some analytical results were obtained up to now in the limiting case of infinitely large number of resonances, [4][5][6][7]. Quite opposite, we show below that the principal influence on a chosen resonance comes from a restricted number of its near neighbors.…”

Section: Overlapping Resonancesmentioning

confidence: 55%

Neutron Resonances: Widths Distribution versus the Porter-Thomas Law

Соколов

2017

Acta Phys. Pol. A

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The neutron resonance scattering off heavy nuclei is a paradigmatic example of the chaotic processes that are well described within the framework of the standard Random Matrix Theory (RMT). In zero approximation of non-overlapping resonances, the resonance width distribution is given by the standard Porter-Thomas law (PTD), where x = Γ / Γ is the resonance width measured in the units of its mean value. We analyze the influence of the resonance overlapping and show that the experimentally observed deviations from of the PTD arise due to the influence of a moderate number of neighboring resonances located inside a restricted energy interval within which the mean level spacing D remains constant.

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“…[8] motivated closer studies of the effect of these interactions on the fluctuations of the partial widths. It was shown numerically [9] and analytically [10] that even a relatively weak imaginary term could cause the partial width fluctuations to deviate from the PTD. However, it is unclear if the coupling for isolated resonances is strong enough to cause this effect.…”

Section: Introductionmentioning

confidence: 99%

Neutron width statistics in a realistic resonance-reaction model

2018

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A basic prediction of the statistical model of compound nucleus reactions is that the partial widths for decay into any open channel channel fluctuate according to the Porter-Thomas distribution (PTD). A recent experiment on sand p-wave neutron scattering from platinum isotopes found that the experimental s-wave partial neutron width distributions deviated substantially from the PTD. Several explanations for this finding have been proposed within the statistical model, but none has resolved this issue. Here, we review the application of a realistic resonance-reaction model to s-wave neutron scattering from 194 Pt. Our main conclusion is that the PTD provides an excellent description of the partial neutron width distribution, provided that the secular energy dependence of the average neutron width is correctly described. Within a realistic range of model parameters, there can be a near-threshold bound or virtual state of the neutron channel that changes this secular dependence from the usual √ E dependence, as proposed by Weidenmüller [1]. In this case, the use of the √ E dependence to analyze the data will lead to apparent deviations from the PTD. We discuss the limited parameter range where such a near threshold state can have a significant effect.

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Resonance width distribution in RMT: Weak-coupling regime beyond Porter-Thomas

Cited by 25 publications

References 60 publications

Statistical-model description of γ decay from compound-nucleus resonances

Statistical-model description of γ decay from compound-nucleus resonances

Neutron Resonances: Widths Distribution versus the Porter-Thomas Law

Neutron width statistics in a realistic resonance-reaction model

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