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論文

First observation of the decay of the 13/2$$^+$$ isomer in $$^{183}$$Hg and $$B$$(${it M}$2) systematics of neutron transitions across the nuclear chart

Huang, H.*; Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Li, Z. H.*; Guo, C. Y.*; Barzakh, A. E.*; Van Duppen, P.*; Andel, B.*; et al.

Physics Letters B, 833, p.137345_1 - 137345_8, 2022/10

https://doi.org/10.1016/j.physletb.2022.137345
 被引用回数：0 パーセンタイル：0.02(Astronomy & Astrophysics)

The decay of the 13/2$$^+$$ isomeric state in $$^{183}$$Hg was observed for the first time following the $$alpha$$ decay of the 13/2$$^+$$ isomer in $$^{187}$$Pb produced in the $$^{142}$$Nd$$(^{50}$$Cr$$, 2p3n)$$ reaction. Using $$alpha$$-$$gamma$$ delayed coincidence measurements, the half-life of this isomer was measured to be 290(30) $$mu$$s. This isomer is proposed to deexcite by an unobserved low-energy $$M$$2 transition to the known 9/2$$^-$$ member of a strongly prolate-deformed 7/2$$^-$$[514] band, followed by a 105-keV $$M$$1 transition to the bandhead. A lower limit of B($$M$$2)$$geq$$0.018 W.u. was deduced for the unobserved transition. The presumed retardation is proposed to be due to the notable shape change between the initial, nearly spherical, and the final, strongly deformed, states. A similar scenario is also considered for the 13/2$$^+$$ isomer in $$^{181}$$Hg, suggesting both are cases of shape isomers. The B($$M$$2) systematics of neutron transitions across the nuclear chart is discussed.

論文

Search for axionlike particles produced in $$e^+e^-$$ collisions at Belle II

Abudin$'e$n, F.*; 谷田 聖; Belle II Collaboration*; 他334名*

Physical Review Letters, 125(16), p.161806_1 - 161806_9, 2020/10

https://doi.org/10.1103/PhysRevLett.125.161806
 被引用回数：37 パーセンタイル：91.79(Physics, Multidisciplinary)

We present a search for the direct production of a light pseudoscalar $$a$$ decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process $${e^+e^-togamma a, a togammagamma}$$ in the mass range $${0.2} , < m_a < {9.7},$$${GeV/$c^2$}$ using data corresponding to an integrated luminosity of $$(445pm 3),$$pb$$^{-1}$$. Light pseudoscalars interacting predominantly with standard model gauge bosons (so-called axion-like particles or ALPs) are frequently postulated in extensions of the standard model. We find no evidence for ALPs and set 95% confidence level upper limits on the coupling strength $$g_{agammagamma}$$ of ALPs to photons at the level of $$10^{-3},$$GeV$$^{-1}$$. The limits are the most restrictive to date for $$0.2, < ,m_a, < ,1,$$GeV/$$c^2$$.

論文

Population of a low-spin positive-parity band from high-spin intruder states in $$^{177}$$Au; The Two-state mixing effect

Venhart, M.*; Balogh, M.*; Herz$'a$$v{n}$, A.*; Wood, J. L.*; Ali, F. A.*; Joss, D. T.*; Andreyev, A. N.; Auranen, K.*; Carroll, R. J.*; Drummond, M. C.*; et al.

Physics Letters B, 806, p.135488_1 - 135488_6, 2020/07

https://doi.org/10.1016/j.physletb.2020.135488
 被引用回数：6 パーセンタイル：59.56(Astronomy & Astrophysics)

The extremely neutron-deficient isotopes $$^{177,179}$$Au were studied by means of in-beam $$gamma$$-ray spectroscopy. Specific tagging techniques, $$alpha$$-decay tagging in $$^{177}$$Au and isomer tagging in $$^{179}$$Au, were used for these studies. Feeding of positive-parity, nearly spherical states, which are associated with 2$$d_{3/2}$$ and 3$$s_{1/2}$$ proton-hole configurations, from the 1$$i_{13/2}$$ proton-intruder configuration was observed in $$^{177}$$Au. Such a decay path has no precedent in odd-Au isotopes and it is explained by the effect of mixing of wave functions of the initial state.

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