Neutron–proton scattering length data extracted from the n + 2H → n + n + p reaction at En = 5 MeV

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Abstract

The nd breakup reaction at an energy of 5 MeV was studied on the RADEX neutron channel of the INR RAS. As a result of comparing the experimental data with the simulation results, the energy of the virtual 1S0 np state Enp = 40 ± 2 keV and the corresponding singlet np scattering length anp = −30.9 ± 0.8 fm were extracted. It was assumed that the obtained anp value, together with the data of other experiments on the study of nd and dd breakup reactions at different energies, are subject to the influence of 3N forces. The work was carried out as part of a series of studies on internucleon interactions at low energies.

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About the authors

A. A. Kasparov

Institute for Nuclear Research of the Russian Academy of Sciences

Author for correspondence.
Email: kasparov200191@gmail.com
Russian Federation, Moscow

M. V. Mordovskoy

Institute for Nuclear Research of the Russian Academy of Sciences

Email: kasparov200191@gmail.com
Russian Federation, Moscow

A. A. Afonin

Institute for Nuclear Research of the Russian Academy of Sciences

Email: kasparov200191@gmail.com
Russian Federation, Moscow

V. V. Mitsuk

Institute for Nuclear Research of the Russian Academy of Sciences

Email: kasparov200191@gmail.com
Russian Federation, Moscow

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Supplementary files

Supplementary Files
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2. Fig. 1. Schematic diagram of the experimental setup: 1 — fragment of the shielding (concrete, heavy concrete) of the neutron beam of the RADEX channel of the INR RAS, 2 — graphite collimator, 3 — active C6D6 target, 4 — assembly of cylindrical scintillation neutron detectors for recording “breakup” neutrons located at angles of 25° at a distance of 84 cm from the center of the target detector, 5 — assembly of detectors for recording recoil neutrons located at angles of 45° at a distance of 108 cm from the center of the target detector. Directions to the conjugate detectors in the two sets are shown by different types of lines.

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3. Fig. 2. Reconstructed energy spectrum of neutrons incident on a deuterium target and causing correlated events in an active C6D6 target and two neutron detectors.

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4. Fig. 3. Two-dimensional diagram of correlations of energies E(n1) – E(n2) of recoil neutrons (n1) and neutrons from the breakup of the np-system (n2): a – experiment; b – simulation at En = 5 ± 1 MeV, Θ(n1) = −45° ± 1.3°; Θ(n2) = 25° ± 1.7°. Dark gray dots in Fig. 3b – the region of simulated events with selection by the relative energy of the np-system ε ≤ 0.2 MeV.

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5. Fig. 4. Two-dimensional Ep — Θp diagram of the secondary proton from the nd-breakup reaction. Gray dots are experimental data, black dots are simulated events of the reaction n + 2H → n1 + (np)s → n1 + n2 + p, going through the stage of formation and breakup of the singlet np-system at En = 5 ± 1 MeV. Experimental conditions: Θ(n1) = −45° ± 1.3°; Θ(n2) = 25° ± 1.7°. Positive and negative angles correspond to different sides of the emission relative to the primary beam direction.

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6. Fig. 5. Comparison of the experimental dependence of the nd-breakup reaction yield on ε at the primary neutron energy En = 5 ± 1 MeV (dots) and the simulation results for different values ​​of the virtual 1S0-level energy Enp (curves): dashed line — 0.015 MeV; solid line — 0.04 MeV; dash-dotted line — 0.07 MeV. The dotted curve is the “democratic” breakup.

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7. Fig. 6. Dependence of χ2 on the energy of the virtual 1S0 level Enp in the nd-breakup reaction at En = 5 ± 1 MeV, obtained using formula (3) by summing over 48 points over ε (0.005–0.24 MeV). The curve is an approximation by a quadratic polynomial.

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8. Fig. 7. Values ​​of |anp| scattering lengths extracted from nd and dd breakup experiments as a function of incident particle energy. Points: □ — data obtained in the dd breakup reaction [19]; ​​○ — data obtained in the nd breakup reaction [5, 7, 18, 20]; ● — result of the present work. The horizontal line corresponds to the value anp = –23.748 ± 0.010 fm extracted from free np scattering experiments.

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