Pion interaction with the trinucleon up to the eta production threshold

Kamalov, S.S.; Tiator, L.; Bennhold, C.

doi:10.1103/physrevc.47.941

Cited by 30 publications

(41 citation statements)

References 58 publications

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“…The model proposed by S.Kamalov et al [21] is not based on the scattering process contrary to Shevchenko's. Indeed, this work is based on an optical model modied by the implementation of the Fermi motion, the Pauli blocking eect, real pion absorption etc ..., In the framework of this model, Kamalov has calculated the pion-induced η cross section.…”

Section: Models Formentioning

confidence: 79%

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η-PHOTOPRODUCTION OFF ³He: SEARCH FOR η-MESIC NUCLEI

Pheron

2011

Int. J. Mod. Phys. A

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Photoproduction of η-mesons off 3 He has been studied via the η → 2γ and η → 3π0 decay modes at the tagged photon beam of the Mainz MAMI accelerator using the combined 4π Crystal Ball/TAPS calorimeter. The main motivation for this experiment was the search for η-mesic nuclei. A possible signature for such states is a threshold enhancement of coherent η-photoproduction similar to what has been observed in hadronic induced reactions at COSY.8

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Section: Models Formentioning

confidence: 79%

“…The comparison is shown in Fig 9.8. The work of Kamalov et al [21] is based on an optical model modied by the implementation of the Fermi motion and the Pauli blocking eect. The Kamalov calculation shows a much smoother rise then the steep rise observed in the present data.…”

Section: Comparison To the Kamalov Model And Shevchenko Modelsmentioning

confidence: 99%

η-PHOTOPRODUCTION OFF ³He: SEARCH FOR η-MESIC NUCLEI

Pheron

2011

Int. J. Mod. Phys. A

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“…Besides this explicit medium modification of the production amplitude also the DWIA formalism for the pion-nucleus rescattering effectively accounts for a ∆ modification in the medium [11]. The quantity Σ ∆ has been deduced from an energydependent fit to a large set of π 0 photoproduction data [9,22] from 4 He and also consistently describes recent photoproduction data from 12 C, 40 Ca and 208 Pb [23].…”

Section: Modification Of the ∆mentioning

confidence: 94%

Self energies of the pion and the Δ isobar from the 3He(e,e′π+)3H reaction

et al. 2002

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In a kinematically complete experiment at the Mainz microtron MAMI, pion angular distributions of the 3 He(e,e'π + ) 3 H reaction have been measured in the excitation Preprint submitted to Elsevier Science 28 April 2018 region of the ∆ resonance to determine the longitudinal (L), transverse (T ), and the LT interference part of the differential cross section. The data are described only after introducing self-energy modifications of the pion and ∆-isobar propagators. Using Chiral Perturbation Theory (ChPT) to extrapolate the pion self energy as inferred from the measurement on the mass shell, we deduce a reduction of the π + mass of ∆m π + = −1.7 + 1.7 − 2.1 MeV/c 2 in the neutron-rich nuclear medium at a density of ρ = 0.057 + 0.085 − 0.057 fm −3 . Our data are consistent with the ∆ self energy determined from measurements of π 0 photoproduction from 4 He and heavier nuclei.

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“…Accordingly, few-nucleon production reactions, near threshold, such as pd → π • 3 He and pd → η 3 He for example, which may be exactly calculable at present, are worth being investigated experimentally at the existing strong focusing synchrotons facilities (COSY, CELSIUS), since they may confirm the proposed relation between threshold energies and number of nucleons involved in the production mechanisms. We note here also that the failure already found in reference [14] to describe by means of the impulse approximation the 3 He(π, η) 3 H reaction below the free production threshold for forward scattering, is already an evidence for a cluster-enhanced rare event.As we mentioned before, it is not our purpose to test models of interacting nuclei but to test the validity of (9) when the kinematic constraints are such that occurence of event c (pion, fast proton,. .…”

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confidence: 89%

Multiplicity distributions associated to subthreshold events in heavy-ion collisions

2001

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Subthreshold events (pion production, for instance) at energies E < m π are treated as rare events. The associated multiplicity distribution P c (n) and the unconstrained distribution P (n), when there is no rare event-trigger, are related by the model independent relation P c (n) = n 2 n 2 P (n) .This relation, and in particular its improved version inspired in clustering of nucleons, is in fair agreement with data. Moreover, it allows to extract from the multiplicity data information on the number of nucleons involved in meson production processes, occuring at energies below the production threshold in free nucleon collisions.1 Production of particles, pions or other hadrons, energetic photons or fast protons, in nucleus-nucleus collisions at energies per nucleon well below the free nucleon-nucleon threshold for such production [1] gives clear evidence for nucleonic correlations in nuclear matter. These correlations may simply reflect the fermionic nature of the nucleons or they may be seen as true collective effects, like clustering of nucleons (see [2] for a review).By clustering processes we mean here pion production mechanisms involving sub-systems with a number of nucleons between 2 and the mass number A, the simplest example being the interaction of a nucleon with a deuteron. In fact, schematically we can represent pion production in the pd→ π 0 pd reaction via resonance formation as in the diagram of Fig.1a. The threshold for the mentioned reaction is lower than the free nucleon threshold (Fig.1b). In contrast to this diagram, the one of Fig.1a is kinematically allowed at subthreshold production energies, because the two nucleons of the deuteron are correlated. Basic diagrams [3][4][5][6], like the one in Fig.1b, require a medium to be non vanishing, for energies below the production energy threshold.Higher mass resonances can be obtained if larger clusters supply the required energy. Our emphasis here is on clustering rather than on the specific mechanism of pion production (like higher-mass resonances [7,8]) In order to see, in a simplified manner, what the problem is, let us write the laboratory energy E L of nucleus A aswhere E N is the average nucleon energy. If one assumes that a collision results from the superposition of nucleon-nucleon collisions and ignores Fermi momentum and binding energy, the threshold kinetic energy per nucleon to produce, say, a pion is,This is the free nucleon threshold. In nuclear matter one may have nucleons with energy above E N and the threshold becomes lower than (2). The lowering of the threshold (2) can be very easily visualized if one allows for clustering of nucleons. If α ≤ A nucleons of nucleus A -with mass number A-collide with one nucleon of nucleus B -with mass number B -(or vice-versa) the threshold energy per nucleon becomes,This is, of course, the threshold for free nucleon-nucleus collisions. As experimental production of pions occurs even at energies bellow m π , this requires clustering from both nuclei, α ≤ A and β ≤ B,with the absolute thr...

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Pion interaction with the trinucleon up to the eta production threshold

Cited by 30 publications

References 58 publications

η-PHOTOPRODUCTION OFF ³He: SEARCH FOR η-MESIC NUCLEI

η-PHOTOPRODUCTION OFF ³He: SEARCH FOR η-MESIC NUCLEI

Self energies of the pion and the Δ isobar from the 3He(e,e′π+)3H reaction

Multiplicity distributions associated to subthreshold events in heavy-ion collisions

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Pion interaction with the trinucleon up to the eta production threshold

Cited by 30 publications

References 58 publications

η-PHOTOPRODUCTION OFF 3He: SEARCH FOR η-MESIC NUCLEI

η-PHOTOPRODUCTION OFF 3He: SEARCH FOR η-MESIC NUCLEI

Self energies of the pion and the Δ isobar from the 3He(e,e′π+)3H reaction

Multiplicity distributions associated to subthreshold events in heavy-ion collisions

Contact Info

Product

Resources

About

η-PHOTOPRODUCTION OFF ³He: SEARCH FOR η-MESIC NUCLEI

η-PHOTOPRODUCTION OFF ³He: SEARCH FOR η-MESIC NUCLEI