Verification of the space-star anomaly in nd breakup

We analyze the results by chiral N N models for the two-nucleon system and calculate the predictions for the nucleon vector analyzing power of elastic nucleon-deuteron (N d) scattering, A y , by these models. Our conclusion is that a quantitative chiral two-nucleon potential does not resolve the N d A y puzzle (when only two-body forces are included).PACS numbers: 21.30.+y, 21.45.+v, 25.10.+s, 27.10+h The term A y puzzle refers to the inability to explain the nucleon vector analyzing power A y in elastic nucleon-deuteron (Nd) scattering below 30 MeV laboratory energy for the incident nucleon by means of three-body calculations in which only two-nucleon forces are applied. The problem showed up as soon as it was possible to conduct three-body continuum calculations with realistic NN potentials. The first such calculation was performed by Stolk and Tjon [1] in 1978 using the Reid soft-core potential [2], and the first calculations with (a separable representation of) the Paris potential [3] were conducted by the Graz-Osaka group in 1987 [4]; in both cases, the A y predictions showed the characteristic problem. Finally, the 'puzzle' became proverbial when rigorous three-nucleon continuum Faddeev calculations using realistic forces were started on a large scale [5]. Over the years, many measurements and calculations of Nd A y were performed (including the pd reaction that involves the Coulomb force [6]) which all confirmed that the problem was real (see Ref.[7] for a review): For energies below 20 MeV, the A y is predicted about 30% too small in the angular region around 120 deg center-of-mass angle where the maximum occurs.There have been many attempts to solve the problem. Already in the very early stages of three-body continuum calculations, when only schematic NN potentials were applied, it was noticed that the Nd A y predictions depend very sensitively on the strength of the input NN potential in the triplet P waves [8,9]-a sensitivity that was confirmed in later calculations using realistic forces [10]. Based upon this experience, Wita la and Glöckle [11] showed in 1991 that small changes in those 3 P wave potentials could remove the discrepancy. This finding gave rise to systematic investigations of the question whether the small variations of the low-energy phase shifts of, particularly, those triplet P waves necessary to explain the Nd A y are consistent with the NN data base. While Tornow and coworkers [12] suggest that the low-energy NN data may leave some lattitude in the NN 3 P waves that could * On leave from University of Salamanca, Spain. Another important observation has been that conventional three-nucleon forces (when added to a realistic two-nucleon potential) change the predictions for Nd A y only slightly and do not improve them [14,6]. Therefore, the general perception in the community has shifted towards the believe that the A y puzzle is the 'smoking gun' for new types of three-nucleon forces [15][16][17][18] or new physics [19].However, very recently, there has been an apparent indicatio...

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“…The circles are pd data from [52]. The crosses and squares are nd data from [53] and [54], respectively.…”

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confidence: 99%

ChiralNNmodel andAypuzzle

2002

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“…The nd data (full circles) are from [6] with standard 3N forces, provide practically the same SST and QFS cross sections. Also, the chiral N 3 LO 3NF is no exception and cannot explain the discrepancy with the data found for the SST configuration [8]. At low energies the cross sections in the SST and QFS configurations are dominated by S-waves.…”

Section: The Dineutron and Its Influence On Nd Observablesmentioning

confidence: 58%

Calculations of Three-Nucleon Reactions

et al. 2013

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Faddeev calculations using the chiral three-nucleon force in next-to-next-to-next-to-leading-order show that this force is too weak to provide an explanation for the low-energy A y puzzle. The large discrepancy between data and theory for the neutron-neutron quasi-free-scattering cross section in low energy neutrondeuteron breakup requires a modification of the 1 S 0 neutron-neutron force. We discuss the consequences that a bound 1 S 0 state of two neutrons has on neutron-deuteron scattering observables. At higher energies we compare the solutions of the non-relativistic three-nucleon Faddeev equations with three-nucleon force included to the solutions of its Poincaré invariant version.

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“…The pd data [26] plotted with the star symbols are about 10% This figure is from Ref. [24]. The data are nd breakup from Ref.…”

Section: Three-nucleon Interactionsmentioning

confidence: 99%

“…The data are nd breakup from Ref. [24] (solid circles), nd breakup from Ref. [25] (open circles) and pd breakup from Ref.…”

Section: Three-nucleon Interactionsmentioning

confidence: 99%

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Few-Nucleon Research at TUNL: Probing Two- and Three-Nucleon Interactions with Neutrons

Howell

Tornow

Witała

2016

EPJ Web of Conferences

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Abstract. The central goal of few-nucleon research at the Triangle Universities Nuclear Laboratory (TUNL) is to perform measurements that contribute to advancing ab-initio calculations of nuclear structure and reactions. The program aims include evaluating theoretical treatments of few-nucleon reaction dynamics through strategically comparing theory predictions to data, determining properties of the neutron-neutron interaction that are not accessible in two-nucleon reactions, and searching for evidence of longrange features of three-nucleon interactions, e.g., spin and isospin dependence. This paper will review studies of three-and four-nucleon systems at TUNL conducted using unpolarized and polarized neutron beams. Measurements of neutron-induced reactions performed by groups at TUNL over the last six years are described in comparison with theory predictions. The results are discussed in the context of the program goals stated above. Measurements of vector analyzing powers for elastic scattering in A=3 and A=4 systems, differential cross sections for neutron-deuteron elastic scattering and neutrondeuteron breakup in several final-state configurations are described. The findings from these studies and plans for the coming three years are presented in the context of worldwide activities in this front, in particular, research presented in this session.

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Verification of the space-star anomaly in nd breakup

Cited by 54 publications

References 26 publications

ChiralNNmodel andAypuzzle

ChiralNNmodel andAypuzzle

Calculations of Three-Nucleon Reactions

Few-Nucleon Research at TUNL: Probing Two- and Three-Nucleon Interactions with Neutrons

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