Search for the tetraneutron by the double-charge-exchange of negative pions

Ungar, J. E.; McKeown, R. D.; Geesaman, D. F.; Specht, Janet K.; Stephenson, K.; Zeidman, B.; Morris, C. L.

doi:10.1016/0370-2693(84)91272-3

Cited by 37 publications

(39 citation statements)

References 13 publications

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“…In Refs. [28,29] these wavefunctions were used to calculate DCX cross sections in 4 He using the exact same form of the double scattering operator as used by Gibbs et al [26]. Surprisingly, agreement was found with both the incorrect data of Kaufman [3] and the presumably correct data of Gilly et al [2].…”

Section: Introductionmentioning

confidence: 93%

“…A series of papers containing theoretical predictions for DCX cross sections in 3 He and 4 He was published by Jibuti and Kezerashvili [28,29,30,31,32,33]. Their basic approach was to expand initial and final nuclear wavefunctions in a hyperspherical basis, solving fourbody equations for the 4 He nucleus using various models of the NN potential. In Refs.…”

Section: Introductionmentioning

confidence: 99%

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Inclusive pion double charge exchange inHe4at intermediate energies

et al. 2005

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A systematic experimental study of inclusive pion double charge exchange in 4 He has been undertaken. The reaction 4 He(π + , π − )4p was observed at incident energies 120, 150, 180, 240 and 270 MeV; the 4 He(π − , π + )4n reaction was observed at incident energies 180 and 240 MeV. At each incident energy, the doubly differential cross section was measured at three to five outgoing pion laboratory angles between 25 • and 130 • . At each angle, cross sections were measured over the range of outgoing pion energies from 10 MeV up to the kinematic limit for the reaction in which the final state consists of the oppositely charged pion plus four free nucleons.The spectra of outgoing pions are strikingly different from those observed for the inclusive double charge exchange reaction in heavier nuclei, but resemble those observed in the (π − , π + ) reaction in 3 He. The forward-angle spectra in the 3 He and 4 He reactions exhibit a prominent peak at high outgoing pion energies. Interpretation of the peaks in 3 He ( 4 He) as a three-(four-)nucleon resonance is ruled out by kinematic analysis. The results of a calculation, wherein the double charge exchange reaction is assumed to proceed as two sequential single charge exchange interactions, suggest that the high-energy peak is naturally explained by this double scattering mechanism.Non-static treatment of the πN interactions and the inclusion of nuclear binding effects appear to be important in reproducing the shape of the energy spectra at forward angles.Pion double charge exchange (DCX), a nuclear reaction in which two units of charge are exchanged between a pion and a nucleus, is an important tool with which to investigate the details of the pion-nucleus interactions as well as correlations between nucleons within the nucleus. DCX is unique among pion-nuclear scattering reactions, as it must involve at least two nucleons in order to conserve charge. Thus, the physiognomy of the DCX process revealed by the experimental cross section depends on the coordinates of two particles in the wavefunction of the nucleus. As a probe of the pion-nucleus interaction, DCX may be used to isolate contributions from different types of reaction mechanisms. Other pion-nucleus reactions appear to be dominated by single scattering mechanisms, but DCX must proceed through less simple mechanisms such as double scattering, as shown in Fig. 1(a).An experimental investigation of DCX in 4 He at intermediate energies has been performed in order to study the multiple scattering mechanisms of the π-nucleus reaction directly. The choice of 4 He as a nuclear target allows an investigation of DCX in an extensively studied few-body system for which microscopic treatment of the dynamics is possible in principle. At the same time, the 4 He nucleus has a large density which may allow some effects of the nuclear medium to be investigated. The final state is also relatively simple, consisting of a pion and either four protons or four neutrons, resulting from, respectively, the reactions 4 He(π + , π − )...

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Inclusive pion double charge exchange inHe4at intermediate energies

et al. 2005

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“…The LAMPF experiment deduced the upper limit of the differential cross section of a bound tetraneutron to be 22 nb/sr at the 1σ confidence level [7]. Taking into account theoretically-calculated energy dependence for the analog transition [17], it is reasonable to aim at a sensitivity of 1 nb/sr in our measurement at 850 MeV.…”

Section: Tetraneutron Search At the Hihr Beamlinementioning

confidence: 97%

“…In 1980's two experiments to search for a bound tetraneutron in the 4 He(π − , π + ) reaction were conducted at LAMPF [7] and TRIUMF [8], but neither could find a signature of the bound state. The incident beam energies were 165 and 80 MeV, respectively.…”

Section: Introductionmentioning

confidence: 99%

Search for Tetraneutron by Pion Double Charge Exchange Reaction at J-PARC

Fujioka¹,

Fukuda²,

Harada³

et al. 2017

Proceedings of the 14th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU2016)

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Tetraneutron ( 4 n) has come back in the limelight, because of recent observation of a candidate resonant state at RIBF. We propose to investigate the pion double charge exchange (DCX) reaction, i.e. 4 He(π − , π + ), as an alternative way to populate tetraneutron. An intense π − beam with the kinetic energy of ∼ 850 MeV, much higher than that in past experiments at LAMPF and TRIUMF, will open up a possibility to improve the experimental sensitivity of the formation cross section, which will be much smaller than hitherto known DCX cross sections such as 9 Be(π − , π + ) 9 He (g.s.).

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“…Several attempts have been made to find a bound tetraneutron system by using a uranium fission reaction [1,8], a pion double-charge-exchange (DCX) reaction 4 Heðπ − ; π þ Þ [9][10][11], and several transfer reactions [12,13]. The existence of the bound tetraneutron system was also discussed in theoretical studies [14][15][16].…”

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confidence: 99%

Can Four Neutrons Tango?

Orr

2016

Physics

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A candidate resonant tetraneutron state is found in the missing-mass spectrum obtained in the doublecharge-exchange reaction 4 Heð 8 He; 8 BeÞ at 186 MeV=u. The energy of the state is 0.83 AE 0.65ðstatÞ AE 1.25ðsystÞ MeV above the threshold of four-neutron decay with a significance level of 4.9σ. Utilizing the large positive Q value of the ð 8 He; 8 BeÞ reaction, an almost recoilless condition of the four-neutron system was achieved so as to obtain a weakly interacting four-neutron system efficiently. DOI: 10.1103/PhysRevLett.116.052501 Multineutron systems have attracted considerable attention in nuclear physics [1]. Few-body systems comprising chargeless nucleons such as the tetraneutron system have long fascinated nuclear physicists and have motivated investigations of pure neutron-neutron interactions possible for these systems. These systems are located beyond the neutron drip line and can serve as a unique test case for understanding nuclear structure at the limit of nuclear stability [2]. They are also closely related to the structure of neutron-rich hypernuclei [3]. Information on multineutron forces obtained in studies of multineutron systems is a critical input into theories of neutron stars [4,5]. Possible testing of universality in many fermion systems is another interesting application of these studies. The weakly coupled many-neutron systems can provide an opportunity to investigate the universality in systems governed by a strong interaction; the BCS-BEC crossover found in cold atoms is a good example [6,7].Several attempts have been made to find a bound tetraneutron system by using a uranium fission reaction [1,8], a pion double-charge-exchange (DCX) reaction 4 Heðπ − ; π þ Þ [9-11], and several transfer reactions [12,13]. The existence of the bound tetraneutron system was also discussed in theoretical studies [14][15][16]. Previously, no evidence was reported for the existence of either a bound tetraneutron system or resonant tetraneutron state. However, Marqués et al. [17] reported the possible existence of a bound tetraneutron observed in a breakup reaction of the 14 Be → 10 Be þ 4n channel. Following this experimental result, several theoretical studies were performed to confirm this result, but all results from these studies were negative [18][19][20].The possibility of the tetraneutron system forming a resonant state remains an open and fascinating question. Ab initio calculations incorporating realistic nuclear interactions [20] suggest that a broad resonance of a tetraneutron state may exist at 2 MeV above the threshold based on the extrapolation of the calculated energy with an external potential well. An investigation of a resonant state by solving the Faddeev-Yakubovsky equations with a complex energy plane shows that a resonant state can be generated only in the presence of a strong four-body force, which is incompatible with the current understanding of nuclear interactions [21]. A calculation assuming a compound system with coexisting 3 n þ n and 2 n þ 2 n coupled cluster configu...

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Search for the tetraneutron by the double-charge-exchange of negative pions

Cited by 37 publications

References 13 publications

Inclusive pion double charge exchange inHe4at intermediate energies

Inclusive pion double charge exchange inHe4at intermediate energies

Search for Tetraneutron by Pion Double Charge Exchange Reaction at J-PARC

Can Four Neutrons Tango?

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