Dominance of nucleon-nucleon bremsstrahlung in mass-asymmetric heavy-ion collisions at 15 MeV/nucleon

Breitbach, Gisbert; Koch, G.; Koch, Sascha; Kühn, W.; Ruckelshausen, Arno; Metag, V.; Novotny, R.; Rieß, S.; Habs, D.; Schwalm, D.; Grosse, E.; Ströher, H.

doi:10.1103/physrevc.40.2893

Cited by 9 publications

(6 citation statements)

References 14 publications

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“…3) [18], typically exhibit 3 main features: soft photons below 10 MeV due to statistical emission from excited reaction products after nucleon evaporation, a bump arising from the y-rle-excitation of giant resonances, and hard photons above 25MeV. At the lower bombarding energies @ / A 5 100 MeV/u) discussed here the conipctition between proton-neutron bremsstrahlung and thermal photon emission from highly excited reaction products has to be considerecl.…”

Section: Competition Between Proton-neutron Bremsstrahlungmentioning

confidence: 93%

“…As an example Fig. 4 shows the angular distribution of photons in the 160 + natW reaction a t 19.5 MeV/u [18]. The data are shown for three photon energy intervals ( The amount of statistical photon emission contributing to the photon spectrum of Fig.…”

Section: Competition Between Proton-neutron Bremsstrahlungmentioning

confidence: 99%

“…/ E , , s); p=(6.0+-In-medium hard photon (Ey > 30 MeV) production probability per proton-neutron co Ilision as a function of the Coulomb corrected projectile velocity in the nucleon-nucleon system. The data points are derived from inclusive cross section date[2][3][4][5][6][7][8][9][10][11][12][13][14][15]18,19] with eq. (1).…”

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confidence: 99%

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Reaction Dynamics of Heavy Ion Collisions Studied by Hard Photon Emission

Metag

1991

Annalen der Physik

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Dedicated to the 200th Anniversary of Annalen der Physik.-Abstract. Tlic role of photons 11s n probe of heavy ion reaction dynamics is discus..ed. Experimental dtrta on tlie systems lUO + \V and 92310 + **Mo illustrate that hard photons render a time differentid information on the evolution of heavy ion collisions ranging from protonneutron brc.rnsstralilung in the initid phase to thermal emission from highly excited reaction products in the 1;ut stage of the reaction. Meuured hard photon multiplicities provide in addition a ncw approach to determine the impact parameter of heavy ion collisions. A systematics of hard photon emission prohxbilities reveals the role of tlie nucleonic Permi motion in the collision zone. Prospects for future c*.upcriments focussing on photon m d neutrnl meson production a t relativistic b o m b d i n g energies i~r e outlined. tTntorsuchungcn dcr Reaktionsdynamik yon Schwarionenreaktionen uher dio Emission hochenergetischer Photoneri lnlinltsubersiclit. Die Bedeutung von Photonen ills Sonden fur die Reaktionsdynamik voiiSchwerionenstoBcn wird diskutiert. Experimentelle Daten zu den Systemen l 6 0 + W und g2Mo -+-9 2 & I~ xeigen, daB Photonen iiber Proton-Neutron Brcmsstrahlung ~u s der Anfangsphase bis zur thcrmisclien Emission aus hochangeregten Reaktionsprodukten in der Endphase der Reaktion Aussagen zum zeitlichcn Ablauf von SchwerionenstoBcn ermoglichen. Gemessene Photonenmultiplizitten bieten zusgtzlich ein neues Verfahren zur Bestimmung des StoBparametera in Schwerionenreaktionen. Eine Systematik der Photonenemissionswahrscheinlichkeiten verdeutlicht, daB aus den Photonendaten auf die Impulsverteilung der Nukleonen in der Reaktionszone geschloesen werden kann. Ab-schlieBend werden die Perspektiven fiir zukunftige Experimente und neue physikalische Fragestel-1 ungen bei relativistischen Schwerionenstohn dargelegt.

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Section: Competition Between Proton-neutron Bremsstrahlungmentioning

confidence: 93%

Section: Competition Between Proton-neutron Bremsstrahlungmentioning

confidence: 99%

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Reaction Dynamics of Heavy Ion Collisions Studied by Hard Photon Emission

Metag

1991

Annalen der Physik

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“…3 shows a typical γ-ray spectrum that includes both the statistical and hard photons produced by 16 O + 184 W interactions at T p = 15 A MeV [21]. We see that the low energy statistical photons have larger cross sections compared to hard photons for E γ > 30 MeV.…”

Section: Hard Photons Production Cross Sectionsmentioning

confidence: 97%

Parametrization of the nucleus-nucleus γ -ray production cross sections below 100 GeV/nucleon: Subthreshold pions and hard photons

Kafexhiu

2016

Phys. Rev. C

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"Subthreshold pions" and so-called "hard photons" are two important channels for producing less than 1 GeV γ-rays and e ± pairs from nuclear collisions with energy per nucleon below the π-meson production threshold. I use publicly available experimental data to parametrize these two channels' γ-ray and e ± production cross sections and extend the pion contribution to these particles spectra at higher energies using their corresponding spectra from pp interactions. These parametrizations are valid for collision energy Tp ≤ 100 A GeV and agree reasonably well with the available experimental data. The new parametrizations allow, for the first time, accurate studies of astrophysical γ-rays below 1 GeV.

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“…At beam energies above E/A = 20 MeV the high energy photons are shown to be produced primarily by incoherent nucleon-nucleon bremsstrahlung. Recent work [2][3][4] has concentrated on lower incident energies (5 MeV/nucleon < Ein c < 20 MeV/nucleon). Experiments by Vojtech et al [3] and Gossett et al [4], studied the isotopic effect on the production mechanism of high energy photons, using the same beam on different isotopes of the same element, and, in the case of Gossett et al [4], beams of different isotopes as well.…”

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Target isotope effect in high energy photon production atE/A=10 MeV

Pfaff

Young

Benenson

et al. 1993

Z. Physik A - Hadrons and Nuclei

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Abstract.A comparison has been made between the production of high energy (Ey>30 MeV) 7 rays from the bombardment of I24Sn and 112Sn targets with E/A= 10 MeV ~2C ions. The results are well explained by the n-p bremsstrahlung model and do not indicate the need for any new processes. 25.20.Lj In the past few years there have been many studies, both experimental and theoretical, on high energy photon production in heavy ion collisions. These studies are thoroughly reviewed in a recent article by Nifenecker and Pinston [ 1 ]. At beam energies above E/A = 20 MeV the high energy photons are shown to be produced primarily by incoherent nucleon-nucleon bremsstrahlung. Recent work [2][3][4] has concentrated on lower incident energies (5 MeV/nucleon < Ein c < 20 MeV/nucleon). Experiments by Vojtech et al. [3] and Gossett et al. [4], studied the isotopic effect on the production mechanism of high energy photons, using the same beam on different isotopes of the same element, and, in the case of Gossett et al. [4], beams of different isotopes as well. A ratio of the production of high energy y rays from the higher A target to that from the lower A target which was higher than that expected in the n-p bremsstrahlung model was observed in the work of Vojtech et al. [3]. The present experiment is an attempt to corroborate this interesting and surprising result. The experiment was performed at the National Superconducting Cyclotron Laboratory with a 12C beam from the K500 Cyclotron at an energy of E/A = 10 MeV. The beam was incident upon self-supporting foil targets of 112Sn (3.29 mg/cm 2) and 1248n (3.44mg/cm2). Both targets had isotopic purity greater than 98.9%. The y-ray detection system consisted of two 12.5 cm diameter by 22.9 cm long cylindrical barium fluoride (BaF2) crystals surrounded by 2.54cm thick plastic anticoincidence shielding. Polyethylene bars 35 cm or 40 cm in length with a diameter of 12.5 cm were placed in front of the BaF 2 detectors in order to reduce the reduce the background due to fast neutrons. The y-ray yield was corrected for the attenuation in these bars. The BaF 2 detector energy vs. time of flight (for a 1 m flight path) relative to the cyclotron radio frequency was recorded with a time resolution of 2 ns FWHM for y-ray energies above 15 MeV. This combined with pulse shape discrimination led to excellent neutron/gamma separation. To minimize the effects of drifts on the ratio of the yield from the two isotopes, the targets were interchanged periodically during the experiment. The detectors were calibrated during the experiment occasionally using the 15.1 MeV ~ ray from a ~2C+12C reaction on a 1 mg/cm 2 target and several cosmic ray muon runs which yield an energy of 81 MeV. PACS:Four silicon surface barrier detectors in a cloverleaf pattern were located 17.1 cm downstream in order to monitor target thickness and beam current. Each of the four detectors was collimated by a 0.32 cm diameter circular hole centered about 20 ~ , just inside the grazing angle for 120 MeV ~2C on the tin isotopes. The...

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Dominance of nucleon-nucleon bremsstrahlung in mass-asymmetric heavy-ion collisions at 15 MeV/nucleon

Cited by 9 publications

References 14 publications

Reaction Dynamics of Heavy Ion Collisions Studied by Hard Photon Emission

Reaction Dynamics of Heavy Ion Collisions Studied by Hard Photon Emission

Parametrization of the nucleus-nucleus γ -ray production cross sections below 100 GeV/nucleon: Subthreshold pions and hard photons

Target isotope effect in high energy photon production atE/A=10 MeV

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