The shape factor of the 20F beta spectrum

Hetherington, D.W.; Alousi, A.; Moore, Robert B.

doi:10.1016/0375-9474(89)90196-6

Cited by 11 publications

(3 citation statements)

References 23 publications

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“…This seems to be too small for a meaningful check of the "strong" CVC hypothesis [23] in free-neutron-decay experiments. This hypothesis has been verified by nuclear P-decay measurements to the -10% level [24,25]; therefore, we can safely use the K = ( p p -p, )/2 CVC value in our calculations. The total decay rate is obtained by integrating Eq.…”

Section: Electron Energy Spectrum and Total Decay Ratesupporting

confidence: 58%

Measurable distributions of unpolarized neutron decay

Glück

1993

Phys. Rev. D

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Several two-and one-dimensional distributions of unpolarized free-neutron decay are calculated. The results of the order-a model-independent radiative correction calculations are tabulated numerically. With these corrections the theoretical distributions become precise enough to make possible the determination of the ratio of the axial-vector to the vector weak coupling constants to a precision of -0.001.

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Section: Electron Energy Spectrum and Total Decay Ratesupporting

confidence: 58%

Measurable distributions of unpolarized neutron decay

Glück

1993

Phys. Rev. D

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“…A new approach to measure the β-spectrum shape consists to implant the radioactive isotope sufficiently deep into a large active detector so that all radiation from the source, except for part of the bremsstrahlung radiation, is contained inside the detector [115,260]. Most importantly, this avoids issues with (back)scattering in the source and on the detector, a major problem in, and often even limiting, β-spectrum shape measurements [74,239]. In the setup at Michigan State University, radioactive nuclei are produced by a fragmentation reaction, with the fragments being mass separated to obtain an isotopically pure beam [115].…”

Section: β-Spectrum Shapementioning

confidence: 99%

New physics searches in nuclear and neutron β decay

González–Alonso

Naviliat‐Cuncic

Severijns

2019

Progress in Particle and Nuclear Physics

244

282

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The status of tests of the standard electroweak model and of searches for new physics in allowed nuclear β decay and neutron decay is reviewed including both theoretical and experimental developments. The sensitivity and complementarity of recent and ongoing experiments are discussed with emphasis on their potential to look for new physics. Measurements are interpreted using a model-independent effective field theory approach enabling to recast the outcome of the analysis in many specific new physics models. Special attention is given to the connection that this approach establishes with high-energy physics. A new global fit of available β-decay data is performed incorporating, for the first time in a consistent way, superallowed 0 + → 0 + transitions, neutron decay and nuclear decays. The constraints on exotic scalar and tensor couplings involving left-or right-handed neutrinos are determined while a constraint on the pseudoscalar coupling from neutron decay data is obtained for the first time as well. The values of the vector and axial-vector couplings, which are associated within the standard model to V ud and g A respectively, are also updated. The ratio between the axial and vector couplings obtained from the fit under standard model assumptions is C A /C V = −1.27510(66). The relevance of the various experimental inputs and error sources is critically discussed and the impact of ongoing measurements is studied. The complementarity of the obtained bounds with other low-and high-energy probes is presented including ongoing searches at the Large Hadron Collider.

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“…Calculations with an improved USDB interaction, including the Coulomb corrections and isospin dependence of Ref. [30] Ab initio predictions in MBPT framework with the chiral NN+3N interaction [22], IMSRG framework with EM, N 2 LOsat, NN+3N(400) and NN-N 4 LO+3N(lnl) interactions, CCEI framework with the EM, NN+3N(400) and NN-N 4 LO+3N(lnl) interactions, and shell model with USDB interactions without and with isospin dependence. The spins of the predicted states are indexed in the figure . state while the observed second excited state is midway between the predicted 4 + 1 and 2 + 2 states.…”

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confidence: 99%

Observation of excited states in Mg20 sheds light on nuclear forces and shell evolution

Randhawa¹,

Kanungo²,

Holl³

et al. 2019

Phys. Rev. C

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The exotic Borromean nucleus 20 Mg with N = 8, located at the proton drip-line provides a unique testing ground for nuclear forces and the evolution of shell structure in the neutron-deficient region. We report on the first observation of proton unbound resonances together with bound states in 20 Mg from the 20 Mg(d,d ) reaction performed at TRIUMF. Phenomenological shell-model calculations offer a reasonable description. However, our experimental results present a challenge for current first-principles nuclear structure approaches and point to the need for improved chiral forces and ab initio calculations. Furthermore, the differential cross section of the first excited state is compared with distorted-wave Born approximation calculations to deduce a neutron quadrupole deformation parameter of βn=0.46±0.21. This provides the first indication of a possible weakening of the N = 8 shell closure at the proton drip-line. PACS numbers: 24.50+g, 25.45.De, 25.60.-t, 25.70.EfThe evolution of shell structure over the nuclear landscape is a manifestation of strong interactions in the complex nuclear many-body system. Properties of nuclei at the neutron and proton drip-lines provide new arenas to investigate the effects of large proton-neutron asymmetry and understand the persistence of mirror symmetry. Shell structure evolution in neutron-rich and proton-rich nuclei [1][2][3][4][5][6][7][8][9][10][11][12] are leading to new insights into nuclear forces, including the role of three-body forces [13,14]. The region around the N = 8 shell closure draws particular interest, since this shell gap disappears at the neutron drip-line and leads to the formation of a twoneutron halo in the Borromean nucleus 11 Li. The small two-neutron separation energy (S 2n = 360 keV) of 11 Li results in the excited states of 11 Li being unbound. Less is known about the structure of nuclei at the proton drip- * Present address: KVI-CART, University of Groningen, 9747 AA Groningen, The Netherlands line. The N = 8 isotone at the proton drip-line, 20 Mg, is also a Borromean system whose two-proton separation energy is S 2p = 2.337(27) MeV [15]. There is no experimental information on resonances above the proton threshold in 20 Mg. In this work we present the first observation of a resonance in 20 Mg through deuteron inelastic scattering. This measurement provides new insight into shell evolution as well as tests of ab initio predictions. The resonance(s) in 20 Mg could also contribute to a potential breakout path from the hot CNO cycle via two-proton capture on the waiting point nucleus 18 Ne in Type-I x-ray bursts [16].Microscopic cluster model [17] predictions for the 2 + state agree with the experiment [18,19]. A 4 + state is predicted at 3 MeV, this state is predicted around 3.8 MeV, using a beyond the mean field approach [20]. Predictions based on an angular momentum projected generator coordinate framework [21], find the 2 + 1 and the 4 + 1 states to be higher in energy around, 3.5 MeV and 7.8 MeV, respectively. Ab initio calculations in a manyb...

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The shape factor of the 20F beta spectrum

Cited by 11 publications

References 23 publications

Measurable distributions of unpolarized neutron decay

Measurable distributions of unpolarized neutron decay

New physics searches in nuclear and neutron β decay

Observation of excited states in Mg20 sheds light on nuclear forces and shell evolution

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