Fri·Jan 12, 2024Friday·January 12, 2024

1. 01*

   First investigation on the isomeric ratio in multinucleon transfer reactions: Entrance channel effects on the spin distribution

   D. Kumar · T. Dickel · A. Zadvornaya · O. Beliuskin · A. Kankainen · P. Constantin · S. Purushothaman · A. Spataru · M. Stryjczyk · L. Al Ayoubi · M. Brunet · L. Canete and 30 other authors

   The multinucleon transfer (MNT) reaction approach was successfully employed for the first time to measure the isomeric ratios (IRs) of ${}^{211}$Po (25/2${}^{+}$) isomer and its (9/2${}^{+}$) ground state at the IGISOL facility using a 945 MeV ${}^{136}$Xe beam impinged on ${}^{209}$Bi and ${}^{\mathrm{nat}}$Pb targets. The dominant production of isomers compared to the corresponding ground states was consistently revealed in the $\alpha$-decay spectra. Deduced IR of ${}^{211}$Po populated through the ${}^{136}$Xe+${}^{\mathrm{nat}}$Pb reaction was found to enhance $\approx$1.8-times than observed for ${}^{136}$Xe+${}^{209}$Bi. State-of-the-art Langevin-type model calculations have been utilized to estimate the spin distribution of an MNT residue. The computations qualitatively corroborate with the considerable increase in IRs of ${}^{211}$Po produced from ${}^{136}$Xe+${}^{\mathrm{nat}}$Pb compared to ${}^{136}$Xe+${}^{209}$Bi. Theoretical investigations indicate a weak influence of target spin on IRs. The enhancement of the ${}^{211}$Po isomer in the ${}^{136}$Xe+${}^{\mathrm{nat}}$Pb over ${}^{136}$Xe+${}^{209}$Bi can be attributed to the different proton ($p$)-transfer production routes. Estimations demonstrate an increment in the angular momentum transfer, favorable for isomer production, with increasing projectile energy. Comparative analysis indicates the two entrance channel parameters, projectile mass and $p$-transfer channels, strongly influencing the population of the high-spin isomer of ${}^{211}$Po (25/2${}^{+}$). This is the first experimental and theoretical investigation on the IRs of nuclei produced via different channels of MNT reactions, with the latter quantitatively underestimating the former by a factor of two.

   nucl-exPLB(2024)·7 citations
2. 02*

   Orbital Angular Momentum Small-$x$ Evolution: Exact Results in the Large-$N_c$ Limit

   Brandon Manley🇺🇸

   We construct an exact solution to the revised small-$x$ orbital angular momentum (OAM) evolution equations derived recently, based on an earlier work. These equations are derived in the double logarithmic approximation (summing powers of ${\alpha }_s{\ln }^2(1/x)$ with ${\alpha }_s$ the strong coupling constant and $x$ the Bjorken $x$ variable) and the large-$N_c$ limit, with $N_c$ the number of quark colors. From our solution, we extract the small-$x$, large-$N_c$ expressions of the quark and gluon OAM distributions. Additionally, we determine the large-$N_c$ small-$x$ asymptotics of the OAM distributions to be \begin{align} \notag L_{q+\bar{q}}(x,Q^2) \sim L_G(x,Q^2) \sim \Delta \Sigma (x,Q^2) \sim \Delta G(x,Q^2) \sim \left(\frac{1}{x} \right)^{\alpha_h}, \end{align} with the intercept ${\alpha }_h$ the same as obtained in the small-$x$ helicity evolution, which can be approximated as ${\alpha }_h\approx 3.66074\sqrt{\frac{{\alpha }_s{N}_c}{2\pi }}$. This result is in complete agreement with the literature. Additionally, we calculate the ratio of the quark and gluon OAM distributions to the flavor-singlet quark and gluon helicity parton distribution functions respectively in the small-$x$ region.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2024)·15 citations
3. 03*

   Axially Symmetric Quadrupole-Octupole Model incorporating Sextic Potential

   M. Chabab🇲🇦 · A. El Batoul · L. El Ouaourti

   We present an extended application of the analytic quadrupole octupole axially symmetric model, originally employed to study the octupole deformation and vibrations in light actinides using an infinite well potential (IW). In this work, we extend the model's applicability to a broader range of nuclei exhibiting octupole deformation by incorporating a sextic potential instead of the Davidson potential.Similarly to conventional models, such as AQOA-IW (for infinite square potential) and AQOA-D (for the Davidson potential), our proposed model is referred to as AQOA-S. By employing the sextic potential, phenomenologically represented as $v(\tilde{\beta })=a_1{\tilde{\beta }}^2+a_2{\tilde{\beta }}^4+a_3{\tilde{\beta }}^6$, we can derive analytical expressions for the energy spectra and transition rates (B(E1), B(E2), B(E3)). The energy spectra of the model are essentially governed by two critical parameters: ${\varphi }_0$, indicating the balance between octupole and quadrupole strain, and $\alpha$, a key factor in adjusting the shape and behavior of the spectra through the sextic potential. In terms of applications, the study encompasses five isotopes, namely ${}^{222-226}$Ra and ${}^{224,226}$Th. Significantly, our model demonstrates remarkable agreement with the corresponding experimental data, particularly for the recently determined B(EL) transition rates of ${}^{224}$Ra, surpassing the performance of the model that employs the Davidson potential. The stability of the octupole deformation in ${}^{224}$Ra adds particular significance to these findings.

   ↳ nucl-thnucl-exNPA(2024)·2 citations
4. 04*

   Landscape of nuclear deformation softness with spherical quasi-particle random phase approximation

   Le-Anh Nguyen · Minh-Loc Bui · Panagiota Papakonstantinou🇰🇷 · Naftali Auerbach

   We investigate the stability and softness of nuclei against quadrupole, octupole, and hexadecapole deformation. By applying the spherical Skyrme-force Hartree-Fock Bardeen-Cooper-Schrieffer quasi-particle random phase approximation, we diagnose ground-state deformation when imaginary solutions are obtained, i.e., the spherical ground state {\em collapses}. We also calculate the multipole polarizability in spherical nuclei with no collapse, as a measure of softness. This numerically light and theoretically sound method is found able to capture deformation patterns across the nuclide chart. The connection between the intrinsic shape of nuclei and the dynamics of their low-lying collective states is established and the role of shell structure is discussed.

   ↳ nucl-thnucl-exPRC(2024)·6 citations
5. 05*

   Xenon-gas ionization chamber to improve particle identification of heavy ion beams with Z>70

   Masahiro Yoshimoto🇯🇵 · Naoki Fukuda🇯🇵 · Riku Matsumura🇯🇵 · Daiki Nishimura🇯🇵 · Hideaki Otsu🇯🇵 · Yohei Shimizu🇯🇵 · Toshiyuki Sumikama🇯🇵 · Hiroshi Suzuki · Hiroyuki Takahashi · Hiroyuki Takeda🇯🇵 · Junki Tanaka🇯🇵 · Koichi Yoshida🇯🇵

   In conventional ionization chambers (ICs) using P-10 (Ar+CH4) gas, as the atomic number (Z) of the ion beams increases in the energy region of 200-300 MeV/u, the Z resolution deteriorates rapidly when Z>70. This degradation is attributed to substantial energy loss straggling caused by charge state fluctuation when the beams traverse a gas medium. The energy loss straggling increases when the beams cannot attain charge state equilibrium in the IC gas. In this study, a xenon-based gas (Xe+CH4), exhibiting a sufficiently large charge state changing cross section, was used in the IC to reach charge state equilibrium. The responses of ICs with P-10 and the xenon-based gases were examined using 238U beams and cocktail radioactive isotope (RI) beams with Z=40-90 at the RI Beam Factory (RIBF). For 238U beams at 165-344 MeV/u, the P-10 gas IC yielded an energy resolution of 1.9-3.0% in full width at half maximum (FWHM), which proved inadequate for Z identification in the uranium region. In contrast, the xenon-based gas IC demonstrated a satisfactory energy resolution of 1.4-1.6%. When using cocktail RI beams, a Z resolution of 1.28 and 0.74 was achieved by the P-10 and the xenon-based gas ICs, respectively, for beams with Z=84-88 at 200 MeV/u. The contrast in Z resolutions between the P-10 and the xenon-based gas ICs was effectively elucidated by the energy loss straggling model, incorporating collisional straggling and straggling due to charge state changes in the IC gases. The xenon-based gas IC, with more than 3sigma Z separation across a broad Z range (Z=40-90), emerged as a practical solution for Z identification of heavy ion beams.

   ↳ physics.ins-dethep-exnucl-exPTEP(2025)·1 citation

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.