Thu·Nov 16, 2023Thursday·November 16, 2023

1. 01*

   Measurement of the Hoyle State Radiative Transition Width

   T. K. Rana · Deepak Pandit🇮🇳 · S. Manna · S. Kundu · K. Banerjee🇮🇳 · A. Sen · R. Pandey🇮🇳 · G. Mukherjee🇮🇳 · T. K. Ghosh🇮🇳 · S. S. Nayak · R. Shil · P. Karmakar🇪🇪 and 21 other authors

   The radiative decay of the Hoyle state is the doorway to the production of heavier elements in stellar environment. Here we report, an exclusive measurement of electric quadruple (E${}_2$) transitions of the Hoyle state to the ground state of ${}^{12}$C through the ${}^{12}$C(p, p${}^{\prime }$$\gamma$$\gamma$)${}^{12}$C reaction. Triple coincidence measurement yields a value of radiative branching ratio ${\Gamma }_{rad}$/$\Gamma$ = 4.01 (30) $\times$ 10${}^{-4}$. The result has been corroborated by an independent experiment based on the complete kinematical measurement $via.$ ${}^{12}$C(p, p${}^{\prime }$)${}^{12}$C reaction (${\Gamma }_{rad}$/$\Gamma$ = 4.04 (30) $\times$ 10${}^{-4}$). Using our results together with the currently adopted values of ${\Gamma }_{\pi }$(E${}_0$)/$\Gamma$ and ${\Gamma }_{\pi }$($E_0$), the radiative width of the Hoyle state is found to be 3.75 (40) $\times$ 10${}^{-3}$ eV. We emphasize here that our result is not in agreement with 34 $\%$ increase in the radiative decay width of the Hoyle state measured recently but consistent with the currently adopted value.

   nucl-exPLB(2024)·5 citations
2. 02*

   Systematic study of the low-lying electric dipole strength in Sn isotopes and its astrophysical implications

   M. Markova🇳🇴 · A. C. Larsen🇳🇴 · P. von Neumann-Cosel🇩🇪 · E. Litvinova🇺🇸 · A. Choplin🇧🇪 · S. Goriely🇧🇪 · S. Martinet🇧🇪 · L. Siess🇧🇪 · M. Guttormsen🇳🇴 · F. Pogliano🇳🇴 · S. Siem🇳🇴

   The $\gamma$-ray strength functions (GSF) and nuclear level densities (NLD) below the neutron threshold have been extracted for ${}^{111-113,116-122,124}$Sn from particle-$\gamma$ coincidence data with the Oslo method. The evolution of bulk properties of the low-lying electric dipole response has been investigated on the basis of the Oslo GSF data and results of a recent systematic study of electric and magnetic dipole strengths in even-even Sn isotopes with relativistic Coulomb excitation. The obtained GSFs reveal a resonance-like peak on top of the tail of the isovector giant dipole resonance, centered at $\approx$8 MeV and exhausting $\approx$2\% of the classical Thomas-Reiche-Kuhn (TRK) sum. In contrast to predictions of the relativistic quasiparticle random-phase and time-blocking approximation calculations (RQRPA and RQTBA), no monotonous increase in the total low-lying $E1$ strength was observed in the experimental data from ${}^{111}$Sn to ${}^{124}$Sn, demonstrating rather similar strength distributions in these nuclei. The Oslo GSFs and NLDs were further used as inputs to constrain the cross sections and Maxwellian-averaged cross sections of $(n,\gamma )$ reactions in the Sn isotopic chain using TALYS. The obtained results agree well with other available experimental data and the recommended values from the JINA REACLIB, BRUSLIB, and KADoNiS libraries. Despite relatively small exhausted fractions of the TRK sum rule, the low-lying electric dipole strength makes a noticeable impact on the radiative neutron-capture cross sections in stable Sn isotopes. Moreover, the experimental Oslo inputs for the ${}^{121,123}$Sn$(n,\gamma )$${}^{122,124}$Sn reactions were found to affect the production of Sb in the astrophysical $i$-process, providing new constraints on the uncertainties of the resulting chemical abundances from multi-zone low-metallicity Asymptotic Giant Branch stellar models.

   nucl-exnucl-thPRC(2024)·23 citations
3. 03*

   Nuclear level densities and $\gamma -$ray strength functions of ${}^{111,112,113}$Sn isotopes studied with the Oslo method

   M. Markova🇳🇴 · A. C. Larsen🇳🇴 · G. M. Tveten🇳🇴 · P. von Neumann-Cosel🇩🇪 · T. K. Eriksen🇳🇴 · F. L. Bello Garrote🇳🇴 · L. Crespo Campo🇳🇴 · F. Giacoppo🇩🇪 · A. Görgen🇳🇴 · M. Guttormsen🇳🇴 · K. Hadynska-Klek🇳🇴 · M. Klintefjord and 4 other authors

   The ${}^{111,112,113}$Sn isotopes have been studied with ($p,d\gamma$), ($p,p^{\prime }\gamma$), and ($d,p\gamma$) reactions to extract the nuclear level densities (NLDs) and $\gamma$-ray strength functions (GSFs) of these nuclei below the neutron separation energy by means of the Oslo method. The experimental NLDs for all three nuclei demonstrate a trend compatible with the constant-temperature model below the neutron separation energy while also being in good agreement with the NLDs of neighboring Sn isotopes, obtained previously with the Oslo-type and neutron evaporation experiments. The extracted microcanonical entropies yield $\approx 1.5$ $k_B$ entropy of a valence neutron in both ${}^{111}$Sn and ${}^{113}$Sn. Moreover, the deduced microcanonical temperatures indeed suggest a clear constant-temperature behavior above $\approx$ 3 MeV in ${}^{111,113}$Sn and above $\approx$ 4.5 MeV in ${}^{112}$Sn. We observe signatures for the first broken neutron pairs between 2 and 4 MeV in all three nuclei. The GSFs obtained with the Oslo method are found to be in good agreement below the neutron threshold with the strengths of ${}^{112,114}$Sn extracted in the ($p,p^{\prime }$) Coulomb excitation experiments.

   nucl-exPRC(2023)·15 citations
4. 04*

   Measurements of evaporation residue cross-sections and evaporation residue-gated $\gamma$-ray fold distributions for ${}^{32}$S+${}^{154}$Sm system

   R. Sariyal · I. Mazumdar🇮🇳 · D. Mehta · N. Madhvan · S. Nath · J. Gehlot · Gonika · S. M. Patel · P. B. Chavan · S. Panwar🇮🇳 · V. Ranga · A. Parihari · A. K. Nasirov · B. M. Kayumov

   Evaporation Residue (ER) cross-sections and ER-gated $\gamma$-ray fold distributions are measured for the ${}^{32}$S + ${}^{154}$Sm nuclear reaction above the Coulomb barrier at six different beam energies from 148 to 191 MeV. $\gamma$-ray multiplicities and spin distributions are extracted from the ER-gated fold distributions. The ER cross-sections measured in the present work are found to be much higher than what was reported in a previous work using a very different target-projectile (${}^{48}$Ti + ${}^{138}$Ba) combination, leading to the same compound nucleus ${}^{186}$Pt, with much less mass asymmetry in the entrance channel than the present reaction. This clearly demonstrates the effect of the entrance channel on ER production cross-section. The ER cross-sections measured in the present work are compared with the results of both the statistical model calculations and the dynamical model calculations. Statistical model calculations have been performed to generate a range of parameter space for both the barrier height and Kramers' viscosity parameter over which the ER cross-section data can be reproduced. The calculations performed using the dinuclear system (DNS) model reproduce the data considering both complete and incomplete fusion processes. DNS calculations indicate the need for the inclusion of incomplete fusion channel at higher energies to reproduce the ER cross-sections.

   nucl-exPRC(2024)·1 citation
5. 05*

   Identifying the spin trapped character of the ${}^{32}$Si isomeric state

   J. Williams🇨🇦 · G. Hackman🇨🇦 · K. Starosta🇨🇦 · R. S. Lubna🇺🇸 · Priyanka Choudhary🇮🇳 · P. C. Srivastava🇮🇳 · C. Andreoiu🇨🇦 · D. Annen🇨🇦 · H. Asch🇨🇦 · M. D. H. K. G. Badanage🇨🇦 · G. C. Ball🇨🇦 · M. Beuschlein🇩🇪 and 21 other authors

   The properties of a nanosecond isomer in ${}^{32}$Si, disputed in previous studies, depend on the evolution of proton and neutron shell gaps near the `island of inversion'. We have placed the isomer at 5505.2(2) keV with $J^{\pi }=5^{-}$, decaying primarily via an $E3$ transition to the $2_1^{+}$ state. The $E3$ strength of 0.0841(10) W.u. is unusually small and suggests that this isomer is dominated by the $(\nu d_{3/2}{)}^{-1}\otimes (\nu f_{7/2}{)}^1$ configuration, which is sensitive to the $N=20$ shell gap. A newly observed $4_1^{+}$ state is placed at 5881.4(13) keV; its energy is enhanced by the $Z=14$ subshell closure. This indicates that the isomer is located in a `yrast trap', a feature rarely seen at low mass numbers.

   nucl-exPRC(2023)·8 citations
6. 06*

   Observation of strangeness enhancement with charmed mesons in high-multiplicity $p\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}}=8.16$TeV

   LHCb collaboration: R. Aaij · A.S.W. Abdelmotteleb · C. Abellan Beteta · F. Abudinén · T. Ackernley · B. Adeva · M. Adinolfi · P. Adlarson · H. Afsharnia · C. Agapopoulou · C.A. Aidala · Z. Ajaltouni and 1097 other authors

   The production of prompt $D_s^{+}$ and $D^{+}$ mesons is measured by the LHCb experiment in proton-lead ($p\mathrm{Pb}$) collisions in both the forward ($1.5<y^{\ast }<4.0$) and backward ($-5.0<y^{\ast }<-2.5$) rapidity regions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{\mathrm{NN}}}=8.16$TeV. The nuclear modification factors of both $D_s^{+}$ and $D^{+}$ mesons are determined as a function of transverse momentum, $p_{\mathrm{T}}$, and rapidity. In addition, the $D_s^{+}$ to $D^{+}$ cross-section ratio is measured as a function of the charged particle multiplicity in the event. An enhanced $D_s^{+}$ to $D^{+}$ production in high-multiplicity events is observed for the whole measured $p_{\mathrm{T}}$ range, in particular at low $p_{\mathrm{T}}$ and backward rapidity, where the significance exceeds six standard deviations. This constitutes the first observation of strangeness enhancement in charm quark hadronization in high-multiplicity $p\mathrm{Pb}$ collisions. The results are also qualitatively consistent with the presence of quark coalescence as an additional charm quark hadronization mechanism in high-multiplicity proton-lead collisions.

   ↳ hep-exnucl-exPRD(2024)·29 citations
7. 07*

   Pion distribution functions from low-order Mellin moments

   Ya Lu🇨🇳 · Yin-Zhen Xu🇪🇸 · Khépani Raya🇪🇸 · Craig D. Roberts🇨🇳 · José Rodríguez-Quintero🇪🇸

   Exploiting an evolution scheme for parton distribution functions (DFs) that is all-orders exact, contemporary lattice-QCD (lQCD) results for low-order Mellin moments of the pion valence quark DF are shown to be mutually consistent. The analysis introduces a means by which key odd moments can be obtained from the even moments in circumstances where only the latter are available. Combining these elements, one arrives at parameter-free lQCD-based predictions for the pointwise behaviour of pion valence, glue, and sea DFs, with sound uncertainty estimates. The behaviour of the pion DFs at large light-front momentum fraction, $x>0.85$, is found to be consistent with QCD expectations and continuum analyses of pion structure functions, i.e., damping like $(1-x{)}^{{\beta }_{\mathrm{parton}}}$, with ${\beta }_{\mathrm{valence}}\approx 2.4$, ${\beta }_{\mathrm{glue}}\approx 3.6$, ${\beta }_{\mathrm{sea}}\approx 4.6$. It may be possible to test these predictions using data from forthcoming experiments.

   ↳ hep-phhep-exhep-latnucl-ex+1PLB(2024)·35 citations

* 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.