Tue·May 30, 2023Tuesday·May 30, 2023

1. 01*

   Deep-underground search for the decay of 180m-Ta with an ultra-low-background HPGe detector

   R. Cerroni🇮🇹 · S. Dell'Oro🇮🇹 · A. Formicola🇮🇹 · S. Ghislandi🇮🇹 · L. Ioannucci🇮🇹 · M. Laubenstein🇮🇹 · B. Lehnert🇺🇸 · S.S. Nagorny🇨🇦 · S. Nisi🇮🇹 · L. Pagnanini🇮🇹

   ${}^{180m}$Ta is the longest-lived metastable state presently known. Its decay has not been observed yet. In this work, we report a new result on the decay of \mTa obtained with a $2015.12$-g tantalum sample measured for $527.7$ d with an ultra-low background HPGe detector in the STELLA laboratory of the Laboratori Nazionali del Gran Sasso (LNGS), in Italy. Before the measurement, the sample has been stored deep-underground for ten years, resulting in subdominant background contributions from cosmogenically activated ${}^{182}$Ta. We observe no signal in the regions of interest and set half-life limits on the process for the two channels EC and ${\beta }^{-}$: $T_{1/2,\mathrm{EC}}>1.6\times 10^{18}$ yr and $T_{1/2,{\beta }^{-}}>1.1\times 10^{18}$ yr ($90$\% C.\,I.), respectively. We also set the limit on the $\gamma$ de-excitation / IC channel: $T_{1/2,\mathrm{IC}}>4.1\times 10^{15}$ yr ($90$\% C.\,I.). These are, as of now, the most stringent bounds on the decay of ${}^{180m}$Ta worldwide. Finally, we test the hypothetical scenarios of de-excitation of ${}^{180m}$Ta by cosmological Dark Matter and constrain new parameter space for strongly-interacting dark-matter particle with mass up to $10^5$ GeV.

   nucl-exEPJC(2023)·8 citations
2. 02*

   Measurement of the ${}^{25}\mathrm{Al}(\mathrm{d},\mathrm{n}{)}^{26}\mathrm{Si}$ reaction and impact on the ${}^{25}\mathrm{Al}(\mathrm{p},\gamma {)}^{26}\mathrm{Si}$ reaction rate

   Eli Temanson🇺🇸 · Jessica Baker🇺🇸 · Sean Kuvin · Ken Hanselman🇺🇸 · Gordon W. McCann🇺🇸 · Lagy T. Baby · Alexander Volya🇺🇸 · Peter Höflich · Ingo Wiedenhöver🇺🇸

   The ${}^{25}\mathrm{Al}(\mathrm{p},\gamma {)}^{26}\mathrm{Si}$ reaction is part of a reaction network with impact on the observed galactic ${}^{26}$Al abundance. A new determination of the proton strength of the lowest $\ell =0$ proton-resonance in ${}^{26}$Si is required to more precisely calculate the thermal reaction rate. To this end, the ${}^{25}\mathrm{Al}(\mathrm{d},\mathrm{n}{)}^{26}\mathrm{Si}$ proton-transfer reaction is measured in inverse kinematics using an in-flight radioactive beam at the RESOLUT facility. Excitation energies of the lowest ${}^{26}$Si proton resonances are measured and cross sections are determined for the lowest $\ell =0$ resonance associated with the $3_3^{+}$ state at 5.92(2) MeV. Coupled reaction channels (CRC) calculations using FRESCO are performed to extract the $\ell =0$ spectroscopic factor for the $3_3^{+}$ state. The proton width for the $3_3^{+}$ state in ${}^{26}$Si is determined to be ${\Gamma }_p$=2.19(45) eV and the $(p,\gamma )$ resonance strength for the $3_3^{+}$ state is extracted as 26(10) meV. This resonance dominates the ${}^{25}\mathrm{Al}(\mathrm{p},\gamma {)}^{26}\mathrm{Si}$ reaction rate above 0.2 GK.

   nucl-exPRC(2023)·3 citations
3. 03*

   QCD-based charge symmetry breaking interaction and the Okamoto-Nolen-Schiffer anomaly

   Hiroyuki Sagawa🇯🇵 · Tomoya Naito🇯🇵 · Xavier Roca-Maza🇮🇹 · Tetsuo Hatsuda🇯🇵

   An approach is proposed to link the charge symmetry breaking (CSB) nuclear interaction and the low-energy constants in quantum chromodynamics (QCD) by matching the CSB effect in nuclear matter. The resulting CSB interaction is applied to study the Okamoto-Nolen-Schiffer anomaly, still lacking a satisfactory microscopic understanding, on the energy differences of mirror nuclei by taking ${}^{17}\mathrm{F}$-${}^{17}\mathrm{O}$, ${}^{15}\mathrm{O}$-${}^{15}\mathrm{N}$, ${}^{41}\mathrm{Sc}$-${}^{41}\mathrm{Ca}$, and ${}^{39}\mathrm{Ca}$-${}^{39}\mathrm{K}$ as typical examples. The magnitude and sign of the QCD-based CSB interactions are found to resolve the anomaly successfully within theoretical uncertainties.

   ↳ nucl-thhep-lathep-phnucl-exPRC(2024)·11 citations
4. 04*

   The asymptotic behaviour of the many-body coupled cluster amplitudes

   Saar Beck🇩🇪 · Ronen Weiss🇺🇸 · Nir Barnea🇮🇱

   We analyze the asymptotic behaviour of the coupled cluster many-body wave-function in the limit of highly excited two- and three-particles states. We find that in this limit the different coupled cluster amplitudes exhibit a recurring behaviour, factorizing into a common asymptotic two- or three-body term. These asymptotic terms depend on the potential and in general are system specific. We also suggest that the knowledge of the asymptotic behaviour can potentially help solving the coupled cluster equations in a more efficient way.

   ↳ nucl-thnucl-ex0 citations
5. 05*

   A schematic model for the direct cross-section in reactions induced by exotic and stable projectiles

   A.Serra · R.Lichtenthäler · O.C.B. Santos · K.C.C. Pires · U. Umbelino

   A geometric model for the direct contribution of the reaction cross section induced by light ions on different targets is presented. The model separates the total reaction cross section into two components, one for total fusion and another for direct reactions. We show that the direct part scales as $2\pi Ra$, where $R$ is related to the nuclear radius and $a$ is the width of a ring, which is related to the nuclear diffuseness. A simple expression is presented to calculate the radius $R$ and the width parameter $a$ in terms of the masses and charges of the system. The method is applied to experimental data of exotic, weakly bound, and strongly bound projectiles on several targets. Different diffuseness parameters were obtained for different types of projectiles: exotic n-rich, stable weakly bound, stable strongly bound and exotic p-rich exotic projectiles.

   ↳ nucl-thnucl-ex0 citations
6. 06*

   Absolute light yield of the EJ-204 plastic scintillator

   J. A. Brown · T. A. Laplace · B. L. Goldblum🇺🇸 · J. J. Manfredi🇺🇸 · T. S. Johnson · F. Moretti · A. Venkatraman

   The absolute light yield of a scintillator, defined as the number of scintillation photons produced per unit energy deposited, is a useful quantity for scintillator development, research, and applications. Yet, literature data on the absolute light yield of organic scintillators are limited. The goal of this work is to assess the suitability of the EJ-204 plastic scintillator from Eljen Technology to serve as a reference standard for measurements of the absolute light yield of organic scintillators. Four EJ-204 samples were examined: two manufactured approximately four months prior and stored in high-purity nitrogen, and two aged approximately eleven years and stored in ambient air. The scintillator response was measured using a large-area avalanche photodiode calibrated using low energy $\gamma$-ray and X-ray sources. The product of the quantum efficiency of the photodetector and light collection efficiency of the housing was characterized using an experimentally-benchmarked optical photon simulation. The average absolute light yield of the fresh samples, 9100 $\pm$ 400 photons per MeV, is lower than the manufacturer-reported value of 10400 photons per MeV. Moreover, the aged samples demonstrated significantly lower light yields, deviating from the manufacturer specification by as much as 26\%. These results are consistent with recent work showcasing environmental aging in plastic scintillators and suggest that experimenters should use caution when deploying plastic scintillators in photon counting applications.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2023)·0 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.