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

We investigate the weak decays of the triply heavy baryon $$\Omega _{QQQ}$$ <math> <msub> <mi>Ω</mi> <mrow> <mi>QQQ</mi> </mrow> </msub> </math> in the light-front quark model. Since $$\Omega _{QQQ}$$ <math> <msub> <mi>Ω</mi> <mrow> <mi>QQQ</mi> </mrow> </msub> </math> consists of three indistinguishable identical heavy quarks, the commonly adopted quark–diquark picture does not seem to be valid anymore. Instead, we employ the three-quark picture for baryons where the three quarks are regarded as individual quarks. We calculate the hadronic form factors for the transitions and give predictions for the decay widths of the semi-leptonic decay modes $$\Omega _{ccc}\rightarrow \Xi _{cc}/ \Omega _{cc}+ l^+\nu _l$$ <math> <mrow> <msub> <mi>Ω</mi> <mrow> <mi>ccc</mi> </mrow> </msub> <mo>→</mo> <msub> <mi>Ξ</mi> <mrow> <mi>cc</mi> </mrow> </msub> <mo>/</mo> <msub> <mi>Ω</mi> <mrow> <mi>cc</mi> </mrow> </msub> <mo>+</mo> <msup> <mi>l</mi> <mo>+</mo> </msup> <msub> <mi>ν</mi> <mi>l</mi> </msub> </mrow> </math> , $$\Omega _{bbb}\rightarrow \Xi _{bb}+ l^-\bar{\nu }_l$$ <math> <mrow> <msub> <mi>Ω</mi> <mrow> <mi>bbb</mi> </mrow> </msub> <mo>→</mo> <msub> <mi>Ξ</mi> <mrow> <mi>bb</mi> </mrow> </msub> <mo>+</mo> <msup> <mi>l</mi> <mo>-</mo> </msup> <msub> <mover> <mrow> <mi>ν</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mi>l</mi> </msub> </mrow> </math> and the non-leptonic decay modes $$\Omega _{ccc}\rightarrow \Xi _{cc}/\Omega _{cc}+ M$$ <math> <mrow> <msub> <mi>Ω</mi> <mrow> <mi>ccc</mi> </mrow> </msub> <mo>→</mo> <msub> <mi>Ξ</mi> <mrow> <mi>cc</mi> </mrow> </msub> <mo>/</mo> <msub> <mi>Ω</mi> <mrow> <mi>cc</mi> </mrow> </msub> <mo>+</mo> <mi>M</mi> </mrow> </math> , $$\Omega _{bbb}\rightarrow \Xi _{bb}+ M$$ <math> <mrow> <msub> <mi>Ω</mi> <mrow> <mi>bbb</mi> </mrow> </msub> <mo>→</mo> <msub> <mi>Ξ</mi> <mrow> <mi>bb</mi> </mrow> </msub> <mo>+</mo> <mi>M</mi> </mrow> </math> . Our study can be a guide for future experiments to discover the triply heavy baryons.

Fang Lu

Hong-Wei Ke

Xiao-Hai Liu

Weak decays of the triply heavy baryons in the three-quark picture with the light-front quark model

The measurements on a few pentaquarks states $$P_c(4440)$$ <math> <mrow> <msub> <mi>P</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mn>4440</mn> <mo>)</mo> </mrow> </mrow> </math> , $$P_c(4457)$$ <math> <mrow> <msub> <mi>P</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mn>4457</mn> <mo>)</mo> </mrow> </mrow> </math> and $$P_{cs}(4459)$$ <math> <mrow> <msub> <mi>P</mi> <mrow> <mi>cs</mi> </mrow> </msub> <mrow> <mo>(</mo> <mn>4459</mn> <mo>)</mo> </mrow> </mrow> </math> excite our new interests about their structures. Since the masses of $$P_c(4440)$$ <math> <mrow> <msub> <mi>P</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mn>4440</mn> <mo>)</mo> </mrow> </mrow> </math> and $$P_c(4457)$$ <math> <mrow> <msub> <mi>P</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mn>4457</mn> <mo>)</mo> </mrow> </mrow> </math> are close to the threshold of $$\Sigma _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Σ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> , in the earlier works, they were regarded as molecular states of $$\Sigma _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Σ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> with quantum numbers $$I(J^P)=\frac{1}{2}(\frac{1}{2}^-)$$ <math> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <msup> <mi>J</mi> <mi>P</mi> </msup> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msup> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mo>-</mo> </msup> <mo>)</mo> </mrow> </mrow> </math> and $$\frac{1}{2}(\frac{3}{2}^-)$$ <math> <mrow> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msup> <mfrac> <mn>3</mn> <mn>2</mn> </mfrac> <mo>-</mo> </msup> <mo>)</mo> </mrow> </mrow> </math> , respectively. In a similar way $$P_{cs}(4459)$$ <math> <mrow> <msub> <mi>P</mi> <mrow> <mi>cs</mi> </mrow> </msub> <mrow> <mo>(</mo> <mn>4459</mn> <mo>)</mo> </mrow> </mrow> </math> is naturally considered as a $$\Xi _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Ξ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> bound state with $$I=0$$ <math> <mrow> <mi>I</mi> <mo>=</mo> <mn>0</mn> </mrow> </math> . Within the Bethe-Salpeter (B-S) framework we systematically study the possible bound states of $$\Lambda _c\bar{D}^*$$ <math> <mrow> <msub> <mi>Λ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> , $$\Sigma _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Σ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> , $$\Xi _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Ξ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> and $$\Xi _c'{\bar{D}}^*$$ <math> <mrow> <msubsup> <mi>Ξ</mi> <mi>c</mi> <mo>′</mo> </msubsup> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> . Our results indicate that $$\Sigma _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Σ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> can form a bound state with $$I(J^P)=\frac{1}{2}(\frac{1}{2}^-)$$ <math> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <msup> <mi>J</mi> <mi>P</mi> </msup> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msup> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mo>-</mo> </msup> <mo>)</mo> </mrow> </mrow> </math> , which corresponds to $$P_c(4440)$$ <math> <mrow> <msub> <mi>P</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mn>4440</mn> <mo>)</mo> </mrow> </mrow> </math> . However for the $$I(J^P)=\frac{1}{2}(\frac{3}{2}^-)$$ <math> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <msup> <mi>J</mi> <mi>P</mi> </msup> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msup> <mfrac> <mn>3</mn> <mn>2</mn> </mfrac> <mo>-</mo> </msup> <mo>)</mo> </mrow> </mrow> </math> system the attraction between $$\Sigma _c$$ <math> <msub> <mi>Σ</mi> <mi>c</mi> </msub> </math> and $${\bar{D}}^*$$ <math> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </math> is too weak to constitute a molecule, so $$P_{c}(4457)$$ <math> <mrow> <msub> <mi>P</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mn>4457</mn> <mo>)</mo> </mrow> </mrow> </math> may not be a bound state of $$\Sigma _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Σ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> with $$I(J^P)=\frac{1}{2}(\frac{3}{2}^-)$$ <math> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <msup> <mi>J</mi> <mi>P</mi> </msup> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msup> <mfrac> <mn>3</mn> <mn>2</mn> </mfrac> <mo>-</mo> </msup> <mo>)</mo> </mrow> </mrow> </math> . As $$\Xi _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Ξ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> and $$\Xi _c'{\bar{D}}^*$$ <math> <mrow> <msubsup> <mi>Ξ</mi> <mi>c</mi> <mo>′</mo> </msubsup> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> systems we take into account of the mixing between $$\Xi _c$$ <math> <msub> <mi>Ξ</mi> <mi>c</mi> </msub> </math> and $$\Xi '_c$$ <math> <msubsup> <mi>Ξ</mi> <mi>c</mi> <mo>′</mo> </msubsup> </math> and the eigenstets should include two normal bound states $$\Xi _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Ξ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> and $$\Xi _c'{\bar{D}}^*$$ <math> <mrow> <msubsup> <mi>Ξ</mi> <mi>c</mi> <mo>′</mo> </msubsup> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> with $$I(J^P)=\frac{1}{2}(\frac{1}{2}^-)$$ <math> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <msup> <mi>J</mi> <mi>P</mi> </msup> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msup> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mo>-</mo> </msup> <mo>)</mo> </mrow> </mrow> </math> and a loosely bound state $$\Xi _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Ξ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> with $$I(J^P)=\frac{1}{2}(\frac{3}{2}^-)$$ <math> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <msup> <mi>J</mi> <mi>P</mi> </msup> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msup> <mfrac> <mn>3</mn> <mn>2</mn> </mfrac> <mo>-</mo> </msup> <mo>)</mo> </mrow> </mrow> </math> . The conclusion that two $$\Xi _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Ξ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> bound states exist, supports the suggestion that the observed peak of $$P_{cs}(4459)$$ <math> <mrow> <msub> <mi>P</mi> <mrow> <mi>cs</mi> </mrow> </msub> <mrow> <mo>(</mo> <mn>4459</mn> <mo>)</mo> </mrow> </mrow> </math> may hide two states $$P_{cs}(4455)$$ <math> <mrow> <msub> <mi>P</mi> <mrow> <mi>cs</mi> </mrow> </msub> <mrow> <mo>(</mo> <mn>4455</mn> <mo>)</mo> </mrow> </mrow> </math> and $$P_{cs}(4468)$$ <math> <mrow> <msub> <mi>P</mi> <mrow> <mi>cs</mi> </mrow> </msub> <mrow> <mo>(</mo> <mn>4468</mn> <mo>)</mo> </mrow> </mrow> </math> . Based on the computations we predict a bound state $$\Xi _c'{\bar{D}}^*$$ <math> <mrow> <msubsup> <mi>Ξ</mi> <mi>c</mi> <mo>′</mo> </msubsup> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> with $$I(J^P)=\frac{1}{2}(\frac{1}{2}^-)$$ <math> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <msup> <mi>J</mi> <mi>P</mi> </msup> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msup> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mo>-</mo> </msup> <mo>)</mo> </mrow> </mrow> </math> but not that with $$I(J^P)=\frac{1}{2}(\frac{3}{2}^-)$$ <math> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <msup> <mi>J</mi> <mi>P</mi> </msup> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msup> <mfrac> <mn>3</mn> <mn>2</mn> </mfrac> <mo>-</mo> </msup> <mo>)</mo> </mrow> </mrow> </math> . Further more accurate experiments will test our approach and results.

Hai Pang

Xue-Qian Li

Study on the possible molecular states composed of $$\Lambda _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Λ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> , $$\Sigma _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Σ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> , $$\Xi _c{\bar{D}}^*$$ <math> <mrow> <msub> <mi>Ξ</mi> <mi>c</mi> </msub> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> and $$\Xi _c'{\bar{D}}^*$$ <math> <mrow> <msubsup> <mi>Ξ</mi> <mi>c</mi> <mo>′</mo> </msubsup> <msup> <mrow> <mover> <mrow> <mi>D</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> <mo>∗</mo> </msup> </mrow> </math> in the Bethe–Salpeter frame based on the pentaquark states $$P_c(4440)$$ <math> <mrow> <msub> <mi>P</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mn>4440</mn> <mo>)</mo> </mrow> </mrow> </math> , $$P_c(4457)$$ <math> <mrow> <msub> <mi>P</mi> <mi>c</mi> </msub> <mrow> <mo>(</mo> <mn>4457</mn> <mo>)</mo> </mrow> </mrow> </math> and $$P_{cs}(4459)$$ <math> <mrow> <msub> <mi>P</mi> <mrow> <mi>cs</mi> </mrow> </msub> <mrow> <mo>(</mo> <mn>4459</mn> <mo>)</mo> </mrow> </mrow> </math>

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

In this work, we study the weak decay between two heavy baryons $${\mathcal {B}}_i(\frac{1}{2}^+)\rightarrow {\mathcal {B}}_f(\frac{3}{2}^+)$$ <math> <mrow> <msub> <mi>B</mi> <mi>i</mi> </msub> <mrow> <mo>(</mo> <msup> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mo>+</mo> </msup> <mo>)</mo> </mrow> <mo>→</mo> <msub> <mi>B</mi> <mi>f</mi> </msub> <mrow> <mo>(</mo> <msup> <mfrac> <mn>3</mn> <mn>2</mn> </mfrac> <mo>+</mo> </msup> <mo>)</mo> </mrow> </mrow> </math> in the light-front quark model where three-quark picture is employed for baryon. We derive general form of transition amplitude of $$ {\mathcal {B}}_i(\frac{1}{2}^+)\rightarrow {\mathcal {B}}_f(\frac{3}{2}^+)$$ <math> <mrow> <msub> <mi>B</mi> <mi>i</mi> </msub> <mrow> <mo>(</mo> <msup> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mo>+</mo> </msup> <mo>)</mo> </mrow> <mo>→</mo> <msub> <mi>B</mi> <mi>f</mi> </msub> <mrow> <mo>(</mo> <msup> <mfrac> <mn>3</mn> <mn>2</mn> </mfrac> <mo>+</mo> </msup> <mo>)</mo> </mrow> </mrow> </math> , and analyze two specific cases of transitions: the weak decays of single heavy baryon $$\Sigma _{b} \rightarrow \Sigma _{c}^*$$ <math> <mrow> <msub> <mi>Σ</mi> <mi>b</mi> </msub> <mo>→</mo> <msubsup> <mi>Σ</mi> <mrow> <mi>c</mi> </mrow> <mo>∗</mo> </msubsup> </mrow> </math> and the decays of double-charmed baryon $$\Xi _{cc}\rightarrow \Sigma _{c}^*(\Xi _{c}^*)$$ <math> <mrow> <msub> <mi>Ξ</mi> <mrow> <mi>cc</mi> </mrow> </msub> <mo>→</mo> <msubsup> <mi>Σ</mi> <mrow> <mi>c</mi> </mrow> <mo>∗</mo> </msubsup> <mrow> <mo>(</mo> <msubsup> <mi>Ξ</mi> <mrow> <mi>c</mi> </mrow> <mo>∗</mo> </msubsup> <mo>)</mo> </mrow> </mrow> </math> . We compute the hadronic form factors for the transitions and apply them to study the decay widths of the semi-leptonic $${\mathcal {B}}_i(\frac{1}{2}^+)\rightarrow {\mathcal {B}}_f(\frac{3}{2}^+) l\bar{\nu }_l$$ <math> <mrow> <msub> <mi>B</mi> <mi>i</mi> </msub> <mrow> <mo>(</mo> <msup> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mo>+</mo> </msup> <mo>)</mo> </mrow> <mo>→</mo> <msub> <mi>B</mi> <mi>f</mi> </msub> <mrow> <mo>(</mo> <msup> <mfrac> <mn>3</mn> <mn>2</mn> </mfrac> <mo>+</mo> </msup> <mo>)</mo> </mrow> <mi>l</mi> <msub> <mover> <mrow> <mi>ν</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> <mi>l</mi> </msub> </mrow> </math> and non-leptonic $${\mathcal {B}}_i(\frac{1}{2}^+)\rightarrow {\mathcal {B}}_f(\frac{3}{2}^+)M$$ <math> <mrow> <msub> <mi>B</mi> <mi>i</mi> </msub> <mrow> <mo>(</mo> <msup> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mo>+</mo> </msup> <mo>)</mo> </mrow> <mo>→</mo> <msub> <mi>B</mi> <mi>f</mi> </msub> <mrow> <mo>(</mo> <msup> <mfrac> <mn>3</mn> <mn>2</mn> </mfrac> <mo>+</mo> </msup> <mo>)</mo> </mrow> <mi>M</mi> </mrow> </math> . Previously we studied the transition $$\Sigma _{b} \rightarrow \Sigma _{c}^*$$ <math> <mrow> <msub> <mi>Σ</mi> <mi>b</mi> </msub> <mo>→</mo> <msubsup> <mi>Σ</mi> <mrow> <mi>c</mi> </mrow> <mo>∗</mo> </msubsup> </mrow> </math> with the quark–diquark picture of baryon in the light-front quark model. Here we revisit this transition with three-quark picture of baryon. At the quark level, the transition $$\Sigma _{b} \rightarrow \Sigma _{c}^*$$ <math> <mrow> <msub> <mi>Σ</mi> <mi>b</mi> </msub> <mo>→</mo> <msubsup> <mi>Σ</mi> <mrow> <mi>c</mi> </mrow> <mo>∗</mo> </msubsup> </mrow> </math> is induced by the $$b\rightarrow c$$ <math> <mrow> <mi>b</mi> <mo>→</mo> <mi>c</mi> </mrow> </math> transition.The subsystem of the two unchanged light quarks which possesses definite and same spin in initial and final state can be viewed as a spectator, so the spectator approximation can be applied directly. For the weak decay of doubly charmed baryon $$\Xi _{cc}$$ <math> <msub> <mi>Ξ</mi> <mrow> <mi>cc</mi> </mrow> </msub> </math> , a c quark decays to a light quark $$q_1$$ <math> <msub> <mi>q</mi> <mn>1</mn> </msub> </math> , so both the initial state cc and final state $$q_1q_2$$ <math> <mrow> <msub> <mi>q</mi> <mn>1</mn> </msub> <msub> <mi>q</mi> <mn>2</mn> </msub> </mrow> </math> ( $$q_1$$ <math> <msub> <mi>q</mi> <mn>1</mn> </msub> </math> and the original $$q_2$$ <math> <msub> <mi>q</mi> <mn>2</mn> </msub> </math> in initial state may be the same flavor quarks) which possess definite spin are no longer spectators. A rearrangement of quarks for initial and final states is adopted to isolate the unchanged subsystem $$cq_2$$ <math> <mrow> <mi>c</mi> <msub> <mi>q</mi> <mn>2</mn> </msub> </mrow> </math> which can be viewed as the spectator approximately. Future measurements on these channels will constrain the nonperturbative parameter in the wavefunctions and test the model predictions.

United States

Yan-Liang Shi

Study on the weak decay between two heavy baryons $${\mathcal {B}}_i(\frac{1}{2}^+)\rightarrow {\mathcal {B}}_f(\frac{3}{2}^+)$$ <math> <mrow> <msub> <mi>B</mi> <mi>i</mi> </msub> <mrow> <mo>(</mo> <msup> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mo>+</mo> </msup> <mo>)</mo> </mrow> <mo>→</mo> <msub> <mi>B</mi> <mi>f</mi> </msub> <mrow> <mo>(</mo> <msup> <mfrac> <mn>3</mn> <mn>2</mn> </mfrac> <mo>+</mo> </msup> <mo>)</mo> </mrow> </mrow> </math> in the light-front quark model

In this work we study the weak decays of $$\Xi _{cc}\rightarrow \Xi _c$$ <math><mrow><msub><mi>Ξ</mi><mrow><mi>cc</mi></mrow></msub><mo>→</mo><msub><mi>Ξ</mi><mi>c</mi></msub></mrow></math> and $$\Xi _{cc}\rightarrow \Xi '_c$$ <math><mrow><msub><mi>Ξ</mi><mrow><mi>cc</mi></mrow></msub><mo>→</mo><msubsup><mi>Ξ</mi><mi>c</mi><mo>′</mo></msubsup></mrow></math> in the light-front quark model. Generally, a naive, but reasonable conjecture suggests that the cc subsystem in $$\Xi _{cc}$$ <math><msub><mi>Ξ</mi><mrow><mi>cc</mi></mrow></msub></math> ( us pair in $$\Xi ^{(')}_c$$ <math><msubsup><mi>Ξ</mi><mi>c</mi><mrow><msup><mo>(</mo><mo>′</mo></msup><mo>)</mo></mrow></msubsup></math> ) stands as a diquark with definite spin and color assignments. During the concerned processes, the diquark of the initial state is not a spectator, namely must be broken. A Racah transformation would decompose the original (cc)q into a combination of c(cq) components. Thus we may deal with the decaying c quark alone while keeping the (cq) subsystem as a spectator. With the re-arrangement of the inner structure we calculate the form factors numerically and then obtain the rates of semi-leptonic decays and non-leptonic decays, which will be measured in the future.

Study on $$\Xi _{cc}\rightarrow \Xi _c$$ <math><mrow><msub><mi>Ξ</mi><mrow><mi>cc</mi></mrow></msub><mo>→</mo><msub><mi>Ξ</mi><mi>c</mi></msub></mrow></math> and $$\Xi _{cc}\rightarrow \Xi '_c$$ <math><mrow><msub><mi>Ξ</mi><mrow><mi>cc</mi></mrow></msub><mo>→</mo><msubsup><mi>Ξ</mi><mi>c</mi><mo>′</mo></msubsup></mrow></math> weak decays in the light-front quark model

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