Effective field theory calculation of nd radiative capture at thermal energies

Sadeghi, Hossein; Bayegan, S.; Grießhammer, Harald W.

doi:10.1016/j.physletb.2006.10.023

Cited by 54 publications

(70 citation statements)

References 20 publications

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“…Neglecting e 44 , it reads 11) and therefore the value attained by R c is driven by the ratio |m 22 /m 44 |, which is about 0.79 at LO and ranges from 1.63 to 1.23 for Λ = 500-800 MeV. We conclude this section by remarking that recent calculations of n-d capture observables [31], based on an effective field theory formulated in terms of nucleon, deuteron, and triton fields with gradient couplings, seem to lead to predictions which are in agreement with data. However, it should be stressed that such a theory cannot be applied to other processes, for example the n-3 He capture, without including additional degrees of freedom.…”

Section: Electromagnetic Observables At N 2 Lo In A=2-3 Systemsmentioning

confidence: 70%

Electromagnetic two-body currents of one- and two-pion range

2008

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Nuclear electromagnetic currents are derived in time-ordered perturbation theory within an effective-field-theory framework including explicit nucleons, ∆ isobars, and pions up to one loop, or N 3 LO. The currents obtained at N 2 LO, i.e. ignoring loop corrections, are used in a study of neutron radiative captures on protons and deuterons at thermal energies, and of A=2 and 3 nuclei magnetic moments. The wave functions for A=2 are derived from solutions of the Schrödinger equation with the Argonne v 18 (AV18) or CD-Bonn (CDB) potentials, while those for A=3 are obtained with the hyperspherical-harmonics-expansion method from a realistic Hamiltonian including, in addition to the AV18 or CDB two-nucleon, also a three-nucleon potential. With the strengths of the ∆-excitation currents occurring at N 2 LO determined to reproduce the n-p cross section and isovector combination of the trinucleon magnetic moments, we find that the cross section and photon circular polarization parameter, measured in n-d and n-d processes, are underpredicted by theory, for example the cross section by (11-38)% as the cutoff is increased from 500 to 800 MeV. A complete analysis of the results, in particular their large cutoff dependence, is presented.

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Section: Electromagnetic Observables At N 2 Lo In A=2-3 Systemsmentioning

confidence: 70%

Electromagnetic two-body currents of one- and two-pion range

2008

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“…Indeed, the rate of convergence in observables provides ample evidence that Q 3 R is much smaller than its a priori estimate, see, e.g., Refs. [12,21,23,[58][59][60][61], and is suggestive that Q 4 R is smaller, too [29,32,46]. There is also circumstantial evidence that this may hold for A > 4 [10].…”

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confidence: 94%

Nuclear Physics Around the Unitarity Limit

et al. 2017

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We argue that many features of the structure of nuclei emerge from a strictly perturbative expansion around the unitarity limit, where the two-nucleon S waves have bound states at zero energy. In this limit, the gross features of states in the nuclear chart are correlated to only one dimensionful parameter, which is related to the breaking of scale invariance to a discrete scaling symmetry and set by the triton binding energy. Observables are moved to their physical values by small perturbative corrections, much like in descriptions of the fine structure of atomic spectra. We provide evidence in favor of the conjecture that light, and possibly heavier, nuclei are bound weakly enough to be insensitive to the details of the interactions but strongly enough to be insensitive to the exact size of the two-nucleon system. DOI: 10.1103/PhysRevLett.118.202501 For the purposes of nuclear physics, QCD, the theory of strong interactions, has essentially two independent parameters, namely the up and down quark masses. Their average controls the pion mass and consequently, the range of the nuclear force R ∼ M −1 π ≃ 1.4 fm. Their difference, plus electromagnetism, generates small differences in masses and interactions between neutrons and protons. At the physical point, the two-nucleon (NN) scattering length in the 3 S 1 channel is a t ≃ 5.4 fm, with the deuteron as a shallow bound state (B D ≃ 2.224 MeV); in the 1 S 0 channel, a s ≃ −23.7 fm, and a shallow virtual bound state exists at B NN Ã ≃ 0.068 MeV. With relatively small changes in quark masses, these states become, respectively, unbound and bound [1][2][3][4]. In the physics of cold atoms near Feshbach resonances, external magnetic fields play a role similar to the quark masses and allow the scattering length to be tuned arbitrarily [5].Approximate correlations B D;NN Ã ≈ 1=ðM N a 2 t;s Þ, with M N ≃ 940 MeV the nucleon mass, hold because the size of all these scales is unnatural compared to the typical interaction range R. The NN system therefore appears close to the unitarity (or unitary) limit, where both states cross zero energy, the scattering lengths become infinite (1=a t;s ¼ 0), and cross sections saturate the unitarity bound. It has indeed been suggested that this happens not far from the physical point [6]. While this presumed proximity has been discussed qualitatively for a long time, it has traditionally not played any special role in constructing nuclear forces, and it is neither assessed nor exploited in order to simplify the description of nuclei. As an exception, Refs. [7,8] use potential models to map out correlations between observables in three-and fournucleon systems as the limit is approached at fixed a t =a s .Here, we argue that the typical particle binding momentum Q A of the A-nucleon system satisfies 1=a s;t < Q A < 1=R so that a combined expansion in Q A R and 1=ðQ A a s;t Þ converges quickly and quantitatively reproduces the physical systems. With this, the gross features of states in the nuclear chart are determined by a very simple le...

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“…[7] for a review) has been used with great success in the two-body sector calculating deuteron electromagnetic form factors [8,9], NN scattering [8,10,11], neutron-proton (np) capture [8,9,12] to (<∼1%) [13], proton-proton fusion [14][15][16], and neutrino deuteron scattering [17]. Progress has also been made in the three-body sector with calculations of nd scattering [6,[18][19][20][21][22][23], pd scattering [24][25][26], nd capture [27][28][29], and the energy difference between 3 H and 3 He [25,30,31]. Previous three-body calculations of nd scattering in EFT(/ π) made use of the partial resummation technique [21].…”

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confidence: 99%

Triton charge radius to next-to-next-to-leading order in pionless effective field theory

Vanasse¹

2017

Phys. Rev. C

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The triton point charge radius is calculated to next-to-next-to-leading order (NNLO) in pionless effective field theory (EFT(/ π)), yielding a prediction of 1.14±0.19 fm (leading order), 1.59±0.08 fm (next-to leading order), and 1.62 ± 0.03 fm (NNLO) in agreement with the current experimental extraction of 1.5978 ± 0.040 fm [1]. The error at NNLO is due to cutoff variation (∼ 1%) within a reasonable range of calculated cutoffs and from a EFT(/ π) error estimate (∼ 1.5%). In addition new techniques are introduced to add perturbative corrections to bound and scattering state calculations for short range effective field theories, but with a focus on their use in EFT(/ π).

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Effective field theory calculation of nd radiative capture at thermal energies

Cited by 54 publications

References 20 publications

Electromagnetic two-body currents of one- and two-pion range

Electromagnetic two-body currents of one- and two-pion range

Nuclear Physics Around the Unitarity Limit

Triton charge radius to next-to-next-to-leading order in pionless effective field theory

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