The dineutron as a bound chargeless nucleus of two identical nucleons has been attracting attention for many decades. In addition to the study of the formation of a bound dineutron in the outgoing channel of specific nuclear reactions, cross-section estimates have been gaining interest as research targets. We used a traditional neutron activation technique to irradiate Lu samples followed by measurements of the induced activity with HPGe spectrometer in order to detect gamma-peaks of the 175Lu ( <italic>n</italic>, 2 <italic>n</italic>) 174 gLu reaction product when this reaction channel is not open for incident neutron energies. Based on two measurements of the instrumental gamma-ray spectra of Lu samples we reliably identified the presence of the 174 gLu isotope in the outgoing channel of the 175Lu ( <italic>n</italic>, 2 <italic>n</italic>) 174 gLu nuclear reaction. Also, the cross-section for this nuclear reaction was obtained and to be equal <math altimg='si1.svg'><mrow><mn>33</mn><mo>.</mo><msubsup><mn>5</mn><mrow><mo>&#8722;</mo><mn>6.7</mn></mrow><mrow><mo>+</mo><mn>7.0</mn></mrow></msubsup></mrow></math> mb. For the first time, the dineutron as a nuclearreaction product was indirectly detected via statistically significant observation of the induced activity of 174 gLu with a corresponding cross-section estimate.

Ukraine

Ihor Kadenko

Hungary

Barna Biró

Mihály Braun

András Fenyvesi

Kateryna Okopna

Nadiia Sakhno

Loránd Zakàny

Formation of bound dineutrons in the 175Lu ( <italic>n</italic>, 2 <italic>n</italic>) 174 gLu nuclear reaction and its cross-section

We revisit the proton emitter $^{149}$Lu utilizing the recently developed triaxial relativistic Hartree-Bogoliubov theory in continuum (TRHBc). By incorporating the microscopic nuclear structure properties from the TRHBc theory into the WKB approximation, we successfully reproduce the measured proton-emission half-life of $^{149}$Lu within experimental uncertainties. A triaxial ground state characterized by (<math><mi>β</mi><mo>=</mo><mn>0.17</mn><mo>,</mo><mi>γ</mi><mo>=</mo><msup><mrow><mn>31</mn></mrow><mrow><mo>∘</mo></mrow></msup></math>) has been clarified for $^{149}$Lu. The inclusion of triaxiality significantly changes nuclear density distributions and potentials, which results in enhanced binding of both the nuclear system and the proton-emitting orbital. As a result, a slightly extended half-life for the proton emission of $^{149}$Lu is achieved after considering triaxial deformation degrees of freedom. The examination of the dependence of the decay width on triaxial deformation parameters highlights the significance of microscopic description of nuclear deformation beyond the proton dripline.

China

Qi Lu

Kai-Yuan Zhang

Shi-Sheng Zhang

Triaxial shape of the one-proton emitter Lu

One-proton radioactivity in $^{149}$Lu, the latest identified proton emitter, is studied in the Wentzel-Kramers-Brillouin (WKB) approach with the proton-nucleus potential extracted from the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) for the first time. The predicted half-life turns out to be consistent with the experimental measurement within uncertainties and (almost) independent of the density functionals in the DRHBc theory. Such a microscopic self-consistent calculation reveals that $^{149}$Lu is oblately deformed with a quadrupole deformation <math><msub><mrow><mi>β</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>≈</mo><mo>−</mo><mn>0.18</mn></math>, and rules out the possibility of a prolate quadrupole deformation suggested in the nonadiabatic quasiparticle model. We also check the validity of this approach in the description of $^{150,151}$Lu and their isomeric states. The deviations of the predicted half-lives from their experimental counterparts are mostly smaller than those of the theoretical studies without considering deformation effects. Furthermore, we predict $^{148}$Lu to be a more oblately deformed proton-emitter with a longer half-life than that of $^{149}$Lu, which can be checked in the future. Our studies show that the DRHBc + WKB approach provides a new alternative method to evaluate the half-lives of well-deformed proton emitters.

Yang Xiao

Si-Zhe Xu

Ru-You Zheng

Germany

Xiang-Xiang Sun

Li-Sheng Geng

One-proton emission from Lu in the DRHBc+WKB approach

The Bu → ψM decays are studied with the perturbative QCD approach, where the psion ψ = ψ(2S), ψ(3770), ψ(4040) and ψ(4160), and the light meson M = π, K, ρ and K*. The factorizable and non-factorizable contributions, and the S-D wave mixing effects on the psions, are considered in the calculation. With appropriate inputs, the branching ratios for the Bu → ψK decays are generally coincident with the experimental data within errors. However, due to the large theoretical and experimental errors, it is impossible for the moment to give a severe constraint on the S-D wave mixing angles.

Yueling Yang

Yupei Guo

Junfeng Sun

Na Wang

Qin Chang

Gongru Lu

Bu → ψM decays and S-D wave mixing effectsSupported by the National Natural Science Foundation of China (11705047, U1632109, 11547014, 11475055) and Open Research Program of Large Research Infrastructures (2017), Chinese Academy of Sciences

The quenching of the experimental spectroscopic factor for proton emission from the short-lived d3/2 isomeric state in 151 m Lu was a long-standing problem. In the present work, proton emission from this isomer has been reinvestigated in an experiment at the Accelerator Laboratory of the University of Jyväskylä. The proton-decay energy and half-life of this isomer were measured to be 1295(5) keV and 15.4(8) μs, respectively, in agreement with another recent study. These new experimental data can resolve the discrepancy in the spectroscopic factor calculated using the spherical WKB approximation. Using the R-matrix approach it is found that the proton formation probability indicates no significant hindrance for the proton decay of 151 m Lu.

F. Wang

B.H. Sun

United Kingdom

Z. Liu

R.D. Page

Sweden

C. Qi

Finland

C. Scholey

S.F. Ashley

L. Bianco

I.J. Cullen

Austria

I.G. Darby

S. Eeckhaudt

Canada

A.B. Garnsworthy

W. Gelletly

Spain

M.B. Gomez-Hornillos

T. Grahn

P.T. Greenlees

D.G. Jenkins

G.A. Jones

South Africa

P. Jones

D.T. Joss

R. Julin

S. Juutinen

S. Ketelhut

S. Khan

A. Kishada

M. Leino

Japan

M. Niikura

Belgium

M. Nyman

J. Pakarinen

S. Pietri

Z. Podolyak

P. Rahkila

S. Rigby

J. Saren

T. Shizuma

J. Sorri

S. Steer

J. Thomson

N.J. Thompson

J. Uusitalo

P.M. Walker

Netherlands

S. Williams

H.F. Zhang

W.Q. Zhang

L.H. Zhu

Spectroscopic factor and proton formation probability for the d 3/2 proton emitter 151 m Lu

Inspired by the potential prospects of ϒ(nS) data samples ( n=1,2,3 ) at LHC and SuperKEKB, ϒ(nS)→Bcρ , BcK⁎ decays are studied phenomenologically with pQCD approach. Branching ratios for ϒ(nS)→Bcρ and BcK⁎ decays are estimated to reach up to O(10−11) and O(10−12) , respectively. Given the identification and detection efficiency of final states, searching for these weak decay modes should be fairly challenging experimentally in the future.

Jinshu Huang

ϒ( nS )→ B c ρ , B c K ⁎ decays with perturbative QCD approach

Besides the traditional strong and electromagnetic decay modes, <math id="M2"><mi>Υ</mi><mo>(</mo><mi>n</mi><mi>S</mi><mo>)</mo></math> meson can also decay through the weak interactions within the standard model of elementary particle. With anticipation of copious <math id="M3"><mi>Υ</mi><mo>(</mo><mi>n</mi><mi>S</mi><mo>)</mo></math> data samples at the running LHC and coming SuperKEKB experiments, the two-body nonleptonic bottom-changing <math id="M4"><mi>Υ</mi><mo>(</mo><mi>n</mi><mi>S</mi><mo>)</mo><mo>→</mo><msubsup><mrow><mi>B</mi></mrow><mrow><mi>c</mi></mrow><mrow><mo>⁎</mo></mrow></msubsup><mi>π</mi><mo>,</mo><msubsup><mrow><mi>B</mi></mrow><mrow><mi>c</mi></mrow><mrow><mo>⁎</mo></mrow></msubsup><mi>K</mi></math> decays (<math id="M5"><mi>n</mi><mo>=</mo><mn>1,2</mn><mo>,</mo><mn>3</mn></math>) are investigated with perturbative QCD approach firstly. The absolute branching ratios for <math id="M6"><mi>Υ</mi><mo>(</mo><mi>n</mi><mi>S</mi><mo>)</mo><mo>→</mo><msubsup><mrow><mi>B</mi></mrow><mrow><mi>c</mi></mrow><mrow><mo>⁎</mo></mrow></msubsup><mi>π</mi></math> and <math id="M7"><msubsup><mrow><mi>B</mi></mrow><mrow><mi>c</mi></mrow><mrow><mo>⁎</mo></mrow></msubsup><mi>K</mi></math> decays are estimated to reach up to about <math id="M8"><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>-</mo><mn>10</mn></mrow></msup></math> and <math id="M9"><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>-</mo><mn>11</mn></mrow></msup></math>, respectively, which might possibly be measured by the future experiments.

Decays with Perturbative QCD Approach

With the potential prospects of the ϒ(1S) data samples at the running LHC and upcoming SuperKEKB, the ϒ(1S)→Bcρ weak decay is studied with the pQCD approach. It is found that (1) the lion's share of branching ratio comes from the longitudinal polarization helicity amplitudes; (2) branching ratio for the ϒ(1S)→Bcρ decay can reach up to O(10−9) , which might be hopefully measurable.

Qingxia Li

The ϒ(1 S )→ B c ρ decay with perturbative QCD approach