Production of charged pions in intermediate-energy heavy-ion collisions

Bernard, Véronique; Girard, J.; Julien, J.; Légrain, R.; Poitou, J.; Öskarsson, A.; Carlén, L.; Gustafsson, H. Å.; Jakobsson, B.; Kristiansson, P.; Norén, Bertil; Otterlund, I.; Ryde, H.; Johansson, T.; Tibell, G.; Bertholet, R.; Guet, C.; Maurel, Marie‐Christine; Nifenecker, H.; Perrin, Paul B.; Schüßler, F.; Buénerd, M.; Lebrun, D.; Martin, P.; Løvhøiden, G.; Bondorf, J.P.; Nielsen, O.B.; Palmeri, A.

doi:10.1016/0375-9474(84)90038-1

Cited by 48 publications

(18 citation statements)

References 10 publications

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“…The energy-integrated differential n-crosssection da/d(2 at zero degrees presents a variation with incident bombarding energy similar to the n ~ data. Even with the crude assumption of an isotropic distribution (this is certainly not the case, see [2][3][4][5] for example), the corresponding total cross-section a(n-) is comparable in magnitude to a(~ ~ as shown in Fig. 1.…”

Section: Pacsmentioning

confidence: 77%

“…Steeper slopes were already observed for n + data when compared to ~z ~ [13]; it was suggested that this could come from an experimental artefact [14]. But here the technique used to identify n-(magnetic field and energy loss) is quite different than usual n § detection technique used so far in comparable studies (range telescope [2]). Differences in the energy resolution could be an explanation [1] or may be some new interesting behaviour has to be investigated further.…”

Section: Pacsmentioning

confidence: 79%

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?? Production in16O +27Al at 38, 65 and 93 MeV/u

Lebrun¹,

Chauvin²,

Julien³

et al. 1990

Z. Physik A - Atomic Nuclei

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Negative pion production cross-sections are measured at 38, 65 and 93 MeV per nucleon in O + A1 reaction. Rough estimations of the total cross sections are given and compared to previous neutral pion data. Double differential cross sections at 93 and 65 MeV/u show enhancement for pions with velocity close to the beam. At variance no effect is observed at 38 MeV, where n-and s o distributions are identical. Few n + detected at 38 MeV support this result. This indicates that at the lowest incident energy nearly the whole projectile participates in the production reaction. 25.70.-z; 25.90. +k Pion production in heavy ion collisions at subthreshold incident energy per nucleon was intensively studied these last years, see e.g. [1]. The rather large production yield still observed at the lowest incident energies (mainly below 50 MeV per nucleon) requires the cooperative action between a large amount of participating nucleons. This implies that production should occur when a large overlap of the colliding nuclei is achieved in rather central reactions. Below 85 MeV/u, all the experiments but one [-2] are concerned with neutral pion measurements [3][4][5][6]. This lack of data comes mainly from the difficulty to detect low energy charged pions in a high level of charged particle background. Due to this limitation, and due also to differences in the detection techniques, charged pion data usually cover a narrower region of phase space than neutral pion data. At first order, from isospin conservation, in a symmetric (N--Z) nuclear collision, each pion charge state should be produced with an equal amount. Differences may come either from an unprobable exotic production reaction, or rather from Coulomb effects due to the nuclear fragment charge distribution at the time the pion production occurs. Then, from the differences between the three charge states, one can expect to get some information on the dynamics of the collision. PACS:We report here on the cross-section measurement of negative pions produced in 160+27A1 collisions at three incident energies. The oxygen beam was delivered by two accelerators: 38 MeV/u at SARA (Grenoble), 65 and 93 MeV/u at GANIL (Caen). Pions were detected around zero degrees in the field of a circular magnet by a detection ensemble including multiwire proportional chambers backed with several plastic scintillators. Experimental details can be found in [-8, 9]. The pion energy measurement covered the range T~ = 7 to 40 MeV, with an angular acceptance centered at O = 0~ ~ We concentrated on low energy pions emitted at zero degrees since Coulomb distortion effects were expected to be maximum in this domain of energy and angle [10]. Indeed the detection system was symmetric for n + and n-, and n + were recorded at 93 and 65 MeV per nucleon [9]. But at 38 MeV/u, the very low pion cross section together with the very important background of positively charged particles, prevented any detailed result. Only 15 counts could be unambiguously attributed to n § (via the detection of the monoenergetic de...

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Section: Pacsmentioning

confidence: 77%

Section: Pacsmentioning

confidence: 79%

?? Production in16O +27Al at 38, 65 and 93 MeV/u

Lebrun¹,

Chauvin²,

Julien³

et al. 1990

Z. Physik A - Atomic Nuclei

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“…It was important to minimize both the electronic noise through proper grounding and the room background through concrete shielding. After such precautions, we found that plastic scintillator telescopes of the CHIC design [14] were very effective at selecting pions.…”

Section: Pion Detectorsmentioning

confidence: 99%

“…All effects have been calculated analytically following the procedure in Ref. [14] and also by Monte-Carlo simulations using GEANT4 [15]. Table 2 shows the results.…”

Section: Determination Of the π + Detection Efficiencymentioning

confidence: 99%

Pion emission in 2H, 12C, 27Al() reactions at threshold

et al. 2008

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The very first data from MAX-lab in Lund, Sweden on pion photoproduction at threshold energies are presented. The decrease of the total π + yield in γ + 12 C, 27 Al reactions below 200 MeV as well as the dσ/dΩ cross-section data essentially follow the predictions of an intranuclear-cascade model with an attractive potential for the pion-nucleus interaction. However, d 2 σ/dΩdT, cross-section data at 176 MeV show deviations which call for refinements of the model and possibly also for the inclusion of coherent pion-production mechanisms.

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“…This seems to be the case in general for the rc-+-production. Experimental data from [54,56] able cm-energy Tcm of 360-960 MeV depending on the targets. Therefore we refrain from the analysis of 7r~ data.…”

Section: Applicationsmentioning

confidence: 99%

Pion production in nuclear collisions

Harzheim

Huber

Metsch

1991

Z. Physik A - Hadrons and Nuclei

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The production of pions in nuclear collisions is analyzed in terms of a microscopic reaction model, where the free energy of the entrance channel is transferred to the final channel through the coupling of the relative motion to the internal excitation of N*-resonances. Such a model allows quite naturally for a consistent analysis of the exclusive and the inclusive production of pions. It turns out that the pionic fusion cross section is determined predominantly by the spectroscopic parentage between the initial target projectile combination and the final nucleus, whereas the inclusive part is dominated by the energy dependence of the phase space factor, i.e. by the number of the degrees of freedom which are relevant in a given kinematical situation. This model is applied to the analysis of available experimental data from threshold to the A(1232)-region. A consistent analysis of both the inclusive and the exclusive part of the pion spectrum is presented. 24.90.+d; 25.10.+s; where A 1 and A 2 denote the target and the projectile and A the (bound) united nucleus, the total free energy of the system available in the entrance channel is converted into the creation of the outgoing pion. Thus the transition operator for this process necessarily has to be a genuine many body operator. In such a coherent reaction there are no spectator nucleons. In the exclusive two body reaction -in the following referred to as pionic fusion -it is evident that the microscopic properties of nuclei, i.e. the nuclear structure, both in the entrance channel (e.g. the target projectile combinations) and in the final channel determine the probability for this cold fusion process. Furthermore, the internal structure of the nuclear constituents plays an important r61e since in the relevant energy range the internal quark excitations of the nucleons, i.e. the baryon resonances, couple strongly to mesonic decay channels. These aspects will be discussed in Sect. 3.

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Production of charged pions in intermediate-energy heavy-ion collisions

Cited by 48 publications

References 10 publications

?? Production in16O +27Al at 38, 65 and 93 MeV/u

?? Production in16O +27Al at 38, 65 and 93 MeV/u

Pion emission in 2H, 12C, 27Al() reactions at threshold

Pion production in nuclear collisions

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