New excited states in the halo nucleus 6He

Mougeot, X.; Lapoux, V.; Mittig, W.; Alamanos, N.; Auger, F.; Avez, B.; Beaumel, D.; Blumenfeld, Y.; Dayras, R.; Drouart, A.; Force, C.; Gaudefroy, L.; Gillibert, A.; Guillot, J.; Iwasaki, H.; Kalanee, T. Al; Keeley, N.; Nalpas, L.; Pollacco, E.; Roger, T.; Roussel‐Chomaz, P.; Suzuki, D.; Kemper, K. W.; Mertzimekis, T. J.; Pakou, A.; Rusek, K.; Scarpaci, J. A.; Simenel, C.; Strojek, I.; Wolski, R.

doi:10.1016/j.physletb.2012.10.054

Cited by 50 publications

(108 citation statements)

References 31 publications

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“…The energy spectrum of states obtained with the SRG-evolved chiral NN potential with λ = 1.5 fm −1 is shown in Figure 7. We find the known J π = 2 + resonance as well as results consistent with two new resonances recently observedat the SPIRAL facility of Ganil [32]: a second 2 + and a 1 + (the parity of the 4.3 MeV J = 1 state was not determined in the experiment). Additional resonant states, not observed, emerged in the 0 − and 2 − negative-parity channels.…”

Section: Ab Initio Description Of Three-cluster Dynamicssupporting

confidence: 89%

Toward a Fundamental Understanding of Nuclear Reactions and Exotic Nuclei

Quaglioni¹,

Hupin²,

Langhammer³

et al. 2015

Proceedings of the Conference on Advances in Radioactive Isotope Science (ARIS2014)

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Nuclear systems near the drip lines offer an exciting opportunity to advance our understanding of the interactions among nucleons, which has so far been mostly based on the study of stable nuclei. However, this is not a goal devoid of challenges. From a theoretical standpoint, it requires the capability to address within an ab initio framework not only bound, but also resonant and scattering states, all of which can be strongly coupled. In recent years, significant progress has been made in ab initio nuclear structure and reaction calculations based on input from Quantum Chromodynamics employing Hamiltonians constructed within chiral effective field theory. In this contribution, we present a brief overview of one of such methods, the ab initio no-core shell model with continuum, and its applications to nucleon and deuterium scattering on light nuclei. The first investigation of the low-lying continuum spectrum of 6 He within an ab initio framework that encompasses the 4 He+n+n three-cluster dynamics characterizing its lowest particle-decay channel will also be briefly presented.KEYWORDS: ab initio calculations, exotic nuclei, low-energy reactions Ab initio nuclear theory including the continuumLight exotic nuclei offer an exciting opportunity to test our understanding of nuclear properties in terms of forces emerging from the underlying theory of Quantum Chromodynamics (QCD). This is not a goal devoid of challenges. Experimentally, the study of rare nuclei is challenged by their short half lives and minute production cross sections. A major stumbling block in nuclear theory has to deal with the low breakup thresholds, which can lead to multi-particle emissions, and can cause bound, resonant and scattering states to be strongly coupled. Even worse, many of the systems we are interested in are simply unbound. Hence, to achieve a fundamental understanding of exotic nuclei we need both advanced experimental techniques and an ab initio nuclear theory including the continuum. In the following we briefly outline the elements of one of such theories, the ab initio no-core shell model with continuum (NCSMC). Nuclear forcesTo develop such an ab initio theory, we start from nuclear interactions grounded in the underlying theory of Quantum Chromodynamics via chiral effective field theory [1][2][3], where nucleons and pions are the only explicit degrees of freedom and the strong interaction is systematically expanded in terms of positive powers of small momenta Q (the generic momentum in the nuclear process or the pion mass) over the chiral symmetry breaking scale Λ ∼ 1 GeV. The nuclear forces emerging from such a procedure order by order are schematically represented by the diagrams of Fig. 1. In particular, we 1

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Section: Ab Initio Description Of Three-cluster Dynamicssupporting

confidence: 89%

Toward a Fundamental Understanding of Nuclear Reactions and Exotic Nuclei

Quaglioni¹,

Hupin²,

Langhammer³

et al. 2015

Proceedings of the Conference on Advances in Radioactive Isotope Science (ARIS2014)

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“…6 of the cited paper is the only published theoretical prediction for E2 strength distribution in 6 He and with some little differences, we essentially confirm that result. According to our calculations the second peak does not match with the recently identified 2 + strength at 2.6 MeV [8]. Possibly other components, like s and d continuum states of 5 He, when taken into account theoretically might affect the quadrupole response of 6 He.…”

contrasting

confidence: 93%

“…The unperturbed energies of these configurations are 1.578, 2.06 and 2.54 MeV respectively, as indicated in the second column of Fig.(1). Ab initio theories [8,11] (at the level of 12 ω) find the sequence of levels (0 + , 2 + , 2 + , 1 + , 0 + ) with a third 0 + lowering rapidly as the basis is increased (see Fig.1 of cited Ref. [11]), confirming our simpler scheme.…”

supporting

confidence: 60%

“…Several theories are listed in Ref. [8] and compared with the available experimental information. Most of them show the same set of levels that we have constructed on p orbitals.…”

mentioning

confidence: 99%

“…For example in Ref. [8] one might wonder that the procedure of extracting the posi-tion and width of the secondary 2 + state from the shoulder of the primary 2 + resonance peak is not free from arbitrariness in the choice of background. This is all the more true when dealing with exotic beams with low intensity and when several competing processes might create a background, as in the present case.…”

mentioning

confidence: 99%

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Pairing in the continuum: The quadrupole response of the Borromean nucleusHe6

et al. 2014

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The ground state and low-lying continuum states of 6 He are found within a shell model scheme, in a basis of two-particle states built out of continuum p-states of the unbound 5 He nucleus, using a simple pairing contact-delta interaction. This accounts for the Borromean character of the bound ground state, revealing its composition. We investigate the quadrupole response of the system and we put our calculations into perspective with the latest experimental results. The calculated quadrupole strength distribution reproduces the narrow 2 + resonance, while a second wider peak is found at about 3.9 MeV above the g.s. energy.

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Excited Nuclear States for He-6 (Helium)

Sukhoruchkin¹,

Soroko²

2015

Supplement to I/25 a-E

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New excited states in the halo nucleus 6He

Cited by 50 publications

References 31 publications

Toward a Fundamental Understanding of Nuclear Reactions and Exotic Nuclei

Toward a Fundamental Understanding of Nuclear Reactions and Exotic Nuclei

Pairing in the continuum: The quadrupole response of the Borromean nucleusHe6

Excited Nuclear States for He-6 (Helium)

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