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Exploring the Unknown Lambda-neutron Interaction

by Benjamin F. Gibson and Iraj. R. Afnan

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Submission summary

Authors (as registered SciPost users): Benjamin Gibson
Submission information
Preprint Link: scipost_201910_00033v2  (pdf)
Date accepted: 2020-01-28
Date submitted: 2020-01-15 01:00
Submitted by: Gibson, Benjamin
Submitted to: SciPost Physics Proceedings
Proceedings issue: 24th European Few Body Conference (EFB2019)
Ontological classification
Academic field: Physics
  • Nuclear Physics - Experiment
Approach: Theoretical


No published Λn scattering data exist. A relativistic heavy-ion experiment has suggested that a Λnn bound state was seen. However, several theoretical analyses have cast serious doubt on the bound-state assertion. Nevertheless, there could exist a three-body Λnn resonance. Such a resonance could be used to constrain the Λn interaction. We dis- cuss Λnn calculations using nn and Λn pairwise interactions of rank-one, separable form that fit effective range parameters of the nn system and those hypothesized for the as yet unobserved Λn system based upon four different ΛN potentials. The use of rank-one separable potentials allows one to analytically continue the Λnn Faddeev equations onto the second complex energy plane in search of resonance poles, by examining the eigenvalue spectrum of the kernel of the Faddeev equations. Although each of the potential models predicts a Λnn sub-threshold resonance pole, scaling of the Λn interaction by as little as ∼5% does produce a physical resonance. This suggests that one may use photo- (electro-)production of the Λnn system from tritium as a tool to examine the strength of the Λn interaction.

Published as SciPost Phys. Proc. 3, 025 (2020)

Submission & Refereeing History

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Resubmission scipost_201910_00033v2 on 15 January 2020

Reports on this Submission

Report 1 by Paul Stevenson on 2020-1-21 (Invited Report)

  • Cite as: Paul Stevenson, Report on arXiv:scipost_201910_00033v2, delivered 2020-01-21, doi: 10.21468/SciPost.Report.1464


1. Well-written
2. Good summary of current state of lambda+n resarch
3. Good reflection of conference presentation


This proceeding deals with what may be currently understood about the lambda-n interaction, based on putative observation of a lambda+nn state (or at least a resonance), and theoretical consideration, with consequent predictions for what might observed at JLab or J-Parc. Potential models based on lambda-p scattering data with assumptions about how these translate to the lambda-n interaction are used to explore the lambda+nn resonance using analytic continuation.

The paper is well-written and a suitable reflection of the work presented at the conference, and should be published in the proceedings.

No typos or particular deficiencies were spotted in the written presentation, though the sentence "[...] the position of the pole would be less sensitive to one of the two effective range parameters, e.g. the effective range." (p7) reads oddly (because of the effective range being but one of the effective range parameters) but it does make sense. If the authors agree and have a suggestion for improvement, they can re-word this in the proof stage.

Requested changes

Some small issues with the references:

1. I note that the to-be-published component of ref [10] was published in 2018 with doi 10.1016/j.physletb.2018.05.041.
2. Ref [30]'s doi appears to point to the erratum for the paper. Ref [12] appears to be published in PRC as well as having an arXiv designation.
3. The first paper listed amongst those in [4] has a badly-formatted doi.

  • validity: high
  • significance: high
  • originality: high
  • clarity: top
  • formatting: excellent
  • grammar: perfect

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