Neutron-proton bremsstrahlung from low-energy heavy-ion reactions

Gan, N.; Brinkmann, K.-Th.; Caraley, A. L.; Fineman, B. J.; Kernan, Warnick J.; McGrath, Robert; Danielewicz, Paweł

doi:10.1103/physrevc.49.298

Cited by 29 publications

(30 citation statements)

References 17 publications

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“…It is seen that both results are in reasonable agreement with experimental data except for very energetic photons. Quantitatively, the agreement is at about the same level as previous calculations by others in the literature [577,579,585]. The uncertainty in the elementary pn → pnγ probability leads to an appreciable effect on the inclusive γ-production in heavy-ion reactions.…”

Section: Hard Photon Production As a Probe Of The Symmetry Energysupporting

confidence: 78%

“…It is seen that the two models give quite similar but quantitatively different results especially near the kinematic limit where the p a γ is significantly higher than the p b γ , as noticed already in Ref. [585]. Shown in the right window of Fig.…”

Section: Hard Photon Production As a Probe Of The Symmetry Energymentioning

confidence: 60%

“…While these reaction models were able to reproduce the qualitative features of experimental data, the quantitative agreement was normally within about a factor of 2. One of the major uncertainties is the input elementary pn → pnγ probability p γ which is still rather model dependent [582][583][584][585][586][587][588]. Early model studies usually could only describe within a factor of 2 the few existing data for the pn → pnγ process [538].…”

Section: Hard Photon Production As a Probe Of The Symmetry Energymentioning

confidence: 99%

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Recent progress and new challenges in isospin physics with heavy-ion reactions

2008

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The ultimate goal of studying isospin physics via heavy-ion reactions with neutron-rich, stable and/or radioactive nuclei is to explore the isospin dependence of in-medium nuclear effective interactions and the equation of state of neutron-rich nuclear matter, particularly the isospin-dependent term in the equation of state, i.e., the density dependence of the symmetry energy. Because of its great importance for understanding many phenomena in both nuclear physics and astrophysics, the study of the density dependence of the nuclear symmetry energy has been the main focus of the intermediate-energy heavy-ion physics community during the last decade, and significant progress has been achieved both experimentally and theoretically. In particular, a number of phenomena or observables have been identified as sensitive probes to the density dependence of the nuclear symmetry energy. Experimental studies have confirmed some of these interesting isospin-dependent effects and allowed us to constrain relatively stringently the symmetry energy at sub-saturation densities. The impacts of this constrained density dependence of the symmetry energy on the properties of neutron stars have also been studied, and they were found to be very useful for the astrophysical community. With new opportunities provided by the various radioactive beam facilities being constructed around the world, the study of isospin physics is expected to remain one of the forefront research areas in nuclear physics. In this report, we review the major progress achieved during the last decade in isospin physics with heavy ion reactions and discuss future challenges to the most important issues in this field.Key words: Equation of state of asymmetric nuclear matter, Nuclear symmetry energy, Heavy-ion reactions with neutron-rich nuclei, Neutron skin thickness of heavy nuclei, Neutron stars Constraining the Skyrme effective interactions and the neutron skin thickness of heavy nuclei using terrestrial nuclear laboratory data 216 8

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Section: Hard Photon Production As a Probe Of The Symmetry Energysupporting

confidence: 78%

Section: Hard Photon Production As a Probe Of The Symmetry Energymentioning

confidence: 60%

Section: Hard Photon Production As a Probe Of The Symmetry Energymentioning

confidence: 99%

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Recent progress and new challenges in isospin physics with heavy-ion reactions

2008

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“…Another is based on the one-boson exchange model involving more quantum mechanical effects [41] as follows,…”

Section: +016mentioning

confidence: 99%

Probing the neutron-skin thickness by photon production from reactions induced by intermediate-energy protons

Wei

2015

Phys. Rev. C

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Photon from neutron-proton bremsstrahlung in p+Pb reactions is examined as a potential probe of the neutron-skin thickness in different centralities and at different proton incident energies. It is shown that the best choice of reaction environment is about 140MeV for the incident proton and the 95%-100% centrality for the reaction system since the incident proton mainly interacts with neutrons inside the skin of the target and thus leads to different photon production to maximal extent. Moreover, considering two main uncertainties from both photon production probability and nucleon-nucleon cross section in the reaction, I propose to use the ratio of photon production from two reactions to measure the neutron-skin thickness because of its cancellation effects on these uncertainties simultaneously, but the preserved about 13%-15% sensitivities on the varied neutron-skin thickness from 0.1 to 0.3fm within the current experimental uncertainty range of the neutron-skin size in 208 Pb. The neutron-skin of nuclei is a fundamental physical quantity in nuclear physics, and has received considerable attention due to its importance in determining the structure of neutron-rich nuclei in nuclear physics and the property of neutron-rich matter in astrophysics. To determine the neutron-skin thickness of nuclei, one should known the proton density distribution and neutron density distribution, and then determines the corresponding neutron-skin thickness by calculating the rootmean-square (rms) radius difference between proton and neutron. Presently, the proton rms radius can be determined precisely, typically with an error of 0.02fm or better for many nuclei [1][2][3]; the neutron rms radius is much less well-known although many efforts have been devoted to probing the neutron density distribution by theoretical and experimental methods such as the nucleon elastic scattering [4][5][6][7], the inelastic excitation of the giant dipole and spin-dipole resonances [8,9], the pygmy dipole resonance [10,11] and experiments in exotic atoms [12][13][14][15][16][17]. This is because almost all of these probes are hadronic ones and need model assumptions to deal with the strong force introducing possible systematic uncertainties even if some of them reach small errors [18]. In this situation, the Parity Radius Experiment (PREX-I) at the Jefferson Laboratory (J-Lab) [19] has been performed to measure the neutron-skin thickness of 208 Pb using parity violating e-Pb scattering, the measured value of 0.33 +0.16−0.18 fm in 208 Pb obviously differs from previous value of 0.11 ± 0.06 fm of 208 Pb from π + -Pb scattering [20] albeit largely overlapping with each other within error bars. However, the obtained results from PREX-I experiment suffer from large uncertain- * Email address: wei.gaofeng@foxmail.com ties although the PREX-I experiment aims to a modelindependent measurement of the neutron-skin thickness of 208 Pb. It is interesting, however, to note that the neutron-skin for 208 Pb as thick as 0.33+0.16 fm reported by the PREX-I experimen...

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“…These can form background pairs either with a correlated γ or deuteron, or with themselves. The bremsstrahlung of photons is known to take place at very low rates for high energy photons [1,9], comparable to the rates of production for the d − γ channel. This 2 The Mott condition (1) implies that the deuterons are mostly emitted in the direction of c.m.…”

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confidence: 99%

Observation of the Mott effect in heavy ion collisions

et al. 1998

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Possibility of observing the Mott momentum in the distribution of the deuterons produced in the process p + n → d + γ, in the first stage of a nuclear reaction is presented. The correlation of a hard photon with a deuteron allows to select those deuterons produced at the beginning of a reaction.PACS numbers: 25., 25.90.+k, 25.70.Lm Corresponding author : M. Ploszajczak GANIL, BP 5027 F-14076 Caen Cedex 05 France * E-mail : bozek@solaris.if j.edu.pl 1 Recent analysis of the hard photon production in heavy ion collisions shows the importance of the two-body process π + N → N + γ in the description of the high energy part of the photon spectrum observed experimentally by the TAPS collaboration [1]. The inclusion of the processes p + n → d + π and p + n → d + γ seems to be necessary in order to improve, simultaneously, the description of the data for the pion and photon production. The two body phase-space and a weak dependence of the cross section σ np→dγ on energy make the p + N → d + γ process important for the high energy part of the photon spectrum. The deuteron in the final state is not Pauli-blocked. If we allowed for all deuteron momenta, that process would be the dominant source of high energy photons (E γ > 30MeV). However, the process p + n → d + γ requires the existence of the bound state of the final deuteron. That means, that the deuteron momentum p d must be above the Mott momentum p Mott [2][3][4], if the influence of the surrounding nucleons is taken into account. In particular, deuterons with low momentum cannot exist at a normal nuclear density. Typically, one finds the condition p d /2 > p Mott /2 ≃ 1.2p F for the existence of a deuteron around the normal nuclear density [4].The process involving a deuteron was not previously discussed in the context of hard photon production in heavy ion reactions [5]. Thus it seems important to test the relevance of that process in a more specific way, using the d − γ correlation. The correlation to a hard photon allows us to select the deuterons from this 2-body process. Additional condition on the minimal energy of the photon or the maximal energy of deuteron allows to select the deuteron production at the early stage of a nuclear reaction. Another way of producing deuterons involves 3-body collisions [4] and it also utilizes as a basic ingredient the value of the Mott momentum. Below, we show how in a more direct way the Mott effect can be tested in heavy ion reactions using the simpler p + n → d + γ process, where both the photon and the deuteron in the final state can be detected experimentally.To understand basic elements of the production process, the d − γ correlations will be studied in a simple firstchance collision model (FCCM). In this model of the initial phase of a heavy ion reaction, the initial momentum distribution of nucleons, that limits the deuteron momenta, is given by the two Fermi spheres 1 . For that distribution, the deuterons are emitted predominantly at 90• in the nucleus-nucleus center of mass (c.m.). In describing the p + n → d +...

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Neutron-proton bremsstrahlung from low-energy heavy-ion reactions

Cited by 29 publications

References 17 publications

Recent progress and new challenges in isospin physics with heavy-ion reactions

Recent progress and new challenges in isospin physics with heavy-ion reactions

Probing the neutron-skin thickness by photon production from reactions induced by intermediate-energy protons

Observation of the Mott effect in heavy ion collisions

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