Tue·Oct 5, 2021Tuesday·October 5, 2021

1. 01*

   Search for $\alpha$ condensed states in ${}^{13}$C using $\alpha$ inelastic scattering

   K. Inaba🇯🇵 · Y. Sasamoto · T. Kawabata🇯🇵 · M. Fujiwara🇯🇵 · Y. Funaki🇯🇵 · K. Hatanaka🇯🇵 · K. Itoh · M. Itoh🇯🇵 · K. Kawase · H. Matsubara · Y. Maeda🇯🇵 · K. Suda and 8 other authors

   We searched for the $\alpha$ condensed state in ${}^{13}$C by measuring the $\alpha$ inelastic scattering at $E_{\alpha }=388$ MeV at forward angles including 0 degrees. We performed the distorted-wave Born-approximation calculation with the single-folding potential and the multipole decomposition analysis to determine the isoscalar transition strengths in ${}^{13}$C. We found a bump structure around $E_x=12.5$ MeV due to the isoscalar monopole ($IS0$) transition. A peak-fit analysis suggested that this bump consisted of several $1/2^{-}$ states. We propose that this bump is due to the mirror state of the 13.5 MeV-state in ${}^{13}$N, which dominantly decays to the $\alpha$ condensed state in ${}^{12}$C. It was speculated that the $1/2^{-}$ states around $E_x=12.5$ MeV were candidates for the $\alpha$ condensed state, but the $3\alpha +n$ orthogonality condition model suggests that the $\alpha$ condensed state is unlikely to emerge as the negative parity states. We also found two $1/2^{+}$ or $3/2^{+}$ states at $E_x=14.5$ and 16.1 MeV excited with the isoscalar dipole ($IS1$) strengths. We suggest that the 16.1-MeV state is a possible candidate for the $\alpha$ condensed state predicted by the cluster-model calculations on the basis of the good correspondence between the experimental and calculated level structures. However, the theoretical $IS1$ transition strength for this state is significantly smaller than the measured value. Further experimental information is strongly desired to establish the $\alpha$ condensed state in ${}^{13}$C.

   nucl-exnucl-thPTEP(2021)·5 citations
2. 02*

   Competition between $(\gamma ,p)$ and $(\gamma ,n)$ photo-disintegration yields

   José Nicolás Orce🇿🇦

   A comprehensive analysis of the competition between photo-proton and photo-neutron disintegration yields is undertaken by constraining photo-absorption data with physics principles -- namely, dipole sum rules, decay properties to open channels, isospin selection rules and statistical evaporation from compound nucleus formation. The trend and magnitude of disintegration yields for self-conjugate nuclei are in agreement with the evaporation model of Blatt and Weisskopf. A substantial improvement is found between the exponential trend presented in this work and that determined by Morinaga using a similar approach. This work allows for the evaluation of frequently missing or inconsistent photo-proton contributions, which impacts the photo-disintegration of light and neutron-deficient nuclei, where photo-proton contributions are relevant.

   nucl-exnucl-thAtom.Data Nucl.Data Tabl.(2022)·7 citations
3. 03*

   Unraveling the reaction mechanism for large alpha production and incomplete fusion in reactions involving weakly bound stable nuclei

   S. K. Pandit🇮🇳 · A. Shrivastava🇮🇳 · K. Mahata · N. Keeley · V. V. Parkar🇮🇳 · R. Palit🇮🇳 · P. C. Rout · K. Ramachandran🇮🇳 · A. Kumar · S. Bhattacharyya · V. Nanal🇮🇳 · S. Biswas🇮🇳 and 4 other authors

   The origin of the large $\alpha$ particle production and incomplete fusion in reactions involving weakly-bound $\alpha$+$x$ cluster nuclei still remains unresolved. While the (two-step) process of breakup followed by capture of the ``free" complementary fragment ($x$) is widely believed to be responsible, a few recent studies suggest the dominant role of (direct) cluster stripping. To achieve an unambiguous experimental discrimination between these two processes, a coincidence measurement between the outgoing $\alpha$ particles and $\gamma$ rays from the heavy residues has been performed for the ${}^7$Li($\alpha$+triton)+${}^{93}$Nb system. Proper choice of kinematical conditions allowed for the first time a significant population of the region accessible only to the direct triton stripping process and not to breakup followed by the capture of the ``free'' triton (from the three-body continuum). This result, also supported by a cluster-transfer calculation, clearly establishes the dominance of the direct cluster-stripping mechanism in the large alpha production.

   nucl-exPLB(2021)·28 citations
4. 04*

   Jet substructure and correlations in hadronic final states from ALICE

   James Mulligan (for the ALICE Collaboration)🇺🇸

   Jets of high energy collimated particles provide a rich phenomenology to study quantum chromodynamics, from first-principles tests of perturbative calculations to investigations of the emergent properties of the strongly-coupled quark-gluon plasma. In these proceedings, we highlight several recent jet measurements by the ALICE Collaboration, with a focus on jet substructure observables.

   nucl-exhep-exPoS(2021)·1 citation
5. 05*

   Proton inelastic scattering reveals deformation in ${}^8$He

   M. Holl🇸🇪 · R. Kanungo🇨🇦 · Z. H. Sun🇺🇸 · G. Hagen🇺🇸 · J. A. Lay🇪🇸 · A. M. Moro🇪🇸 · P. Navrátil🇨🇦 · T. Papenbrock🇺🇸 · M. Alcorta · D. Connolly · B. Davids🇨🇦 · A. Diaz Varela🇨🇦 and 18 other authors

   A measurement of proton inelastic scattering of ${}^8$He at $8.25A$~MeV at TRIUMF shows a resonance at 3.54(6)~MeV with a width of 0.89(11)~MeV. The energy of the state is in good agreement with coupled cluster and no-core shell model with continuum calculations, with the latter successfully describing the measured resonance width as well. Its differential cross section analyzed with phenomenological collective excitation form factor and microscopic coupled reaction channels framework consistently reveals a large deformation parameter ${\beta }_2$ = 0.40(3), consistent with no-core shell model predictions of a large neutron deformation. This deformed double-closed shell at the neutron drip-line opens a new paradigm.

   nucl-exnucl-thPLB(2021)·26 citations
6. 06*

   First observation of isolated nuclear recoils following neutron capture for dark matter calibration

   A.N. Villano🇺🇸 · M. Fritts🇺🇸 · N. Mast🇺🇸 · S. Brown🇺🇸 · P. Cushman🇺🇸 · K. Harris🇺🇸 · V. Mandic🇺🇸

   Low-energy nuclear recoils (NRs) are hard to measure because they produce few e${}^{-}$/h${}^{+}$ pairs in solids -- i.e. they have low "ionization yield". A silicon detector was exposed to thermal neutrons over 2.5\,live-days, probing NRs down to 450\,eV. The observation of a neutron capture-induced component of NRs at low energies is supported by the much-improved fit upon inclusion of a capture NR model. This result shows that thermal neutron calibration of very low recoil energy NRs is promising for dark matter searches, coherent neutrino experiments, and improving understanding of ionization dynamics in solids.

   nucl-exhep-exPRD(2022)·15 citations
7. 07*

   Monte Carlo simulations of {\gamma}-directional correlations and their application on FIFRELIN cascades

   A. Chalil (1) · T. Materna (1) · O. Litaize (2) · A. Chebboubi (2) · F. Gunsing (1) ( (1) IRFU, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France (2) CEA, DES, IRESNE, DER, Cadarache F-13108 Saint-Paul-Lez-Durance, France)

   Angular distribution and correlation measurements are an essential part in nuclear structure experiments, especially when spectroscopic information of a specific nucleus is unknown. In most cases, the experimental determination of the spins, parities of the studied nuclear states, as well as the possible mixing between two electric/magnetic multipoles of a transition are determined using angular correlation measurements. In this work, the full effect of directional {\gamma}-correlations is simulated, by using the formal theory of angular distributions. The density matrix formalism along with its multipole expansions called statistical tensors is employed, enabling to perform a full simulation of the angular correlation effects in a cascade of an arbitrary number of {\gamma} transitions. A triple {\gamma} angular correlation simulation is demonstrated for the first time. The present approach was coupled with the Monte Carlo code FIFRELIN, which can simulate the de-excitation of fission fragments or of excited nuclei after neutron capture. It provides a complete description of the spatial distributions of all the {\gamma} rays in the cascade, that can be used for simulation purposes in various applications both in nuclear and particle physics. The potential for a novel approach in data analysis of angular correlation measurements is discussed thoroughly.

   ↳ nucl-thnucl-exEPJA(2022)·7 citations
8. 08*

   Enhanced symmetry energy bears universality of the r-process

   José Nicolás Orce🇿🇦 · Balaram Dey · Cebo Ngwetsheni · Srijit Bhattacharya · Deepak Pandit🇮🇳 · Brenden Lesch · Andile Zulu

   The abundance of about half of the stable nuclei heavier than iron via the rapid neutron capture process or $r$-process is intimately related to the competition between neutron capture and $\beta$-decay rates, which ultimately depends on the binding energy of neutron-rich nuclei. The well-known Bethe-Weizsäcker semi-empirical mass formula\cite{weiz,bethe} describes the binding energy of ground states -- i.e. nuclei with temperatures of $T\approx 0$ MeV -- with the symmetry energy parameter converging between $23-27$ MeV for heavy nuclei. Here we find an unexpected enhancement of the symmetry energy at higher temperatures, $T\approx 0.7-1.0$ MeV, from the available data of giant dipole resonances built on excited states. Although these are likely the temperatures where seed elements are created -- during the cooling down of the ejecta following neutron-star mergers\cite{mergersnucleo} or collapsars\cite{collapsar} -- the fact that the symmetry energy remains constant between $T\approx 0.7-1.0$ MeV, suggests a similar trend down to $T\approx 0.5$ MeV, where neutron-capture may start occurring. Calculations using this relatively larger symmetry energy yield a reduction of the binding energy per nucleon for heavy neutron-rich nuclei and inhibits radiative neutron-capture rates. This results in a substantial close in of the neutron dripline -- where nuclei become unbound -- which elucidates the long sought universality of heavy-element abundances through the $r$-process; as inferred from the similar abundances found in extremely metal-poor stars and the Sun.

   ↳ astro-ph.HEnucl-exnucl-thMNRAS(2023)·5 citations
9. 09*

   Charm and multi-charm baryon measurements via strangeness tracking with the upgraded ALICE detector

   David Dobrigkeit Chinellato (for the ALICE Collaboration)🇧🇷

   We present a new method for detection of multiply charmed baryons via their decays into strange baryons, using `strangeness tracking'. This method makes use of the state-of-the-art upgraded silicon detectors in ALICE during Runs 3, 4 and beyond will enable the novel possibility of tracking strange hadrons directly before they decay, leading to a very significant improvement in impact-parameter resolution. In this work, we will discuss how this new technique will be crucial to distinguish secondary strange baryons originating from charm decays from primary strange baryons. This is a particularly interesting possibility for the ${\Omega }^{-}$ baryon coming from ${\Omega }_{\mathrm{c}}^0\to {\Omega }^{-}{\pi }^{+}$ decays, since there is no other relevant feeddown source for ${\Omega }^{-}$. This, in turn, means that the main ${\Omega }^{-}$ background for the ${\Omega }_{\mathrm{c}}$ measurement will point most accurately to the primary vertex, unlike pions or protons from other charm baryon decays. We will illustrate the achievable performance of strangeness tracking for the Run 3 configuration of ALICE with the upgraded Inner Tracking System, which is fully instrumented with silicon pixel detectors. Moreover, we will discuss the potential of this technique in a future experiment with an extensive silicon tracking detector with a first layer very close to the interaction point. Finally, we will also cover other potential major applications of strangeness tracking, including measurements of hypernuclei such as the ${}_{\Lambda }^3\mathrm{H}$.

   ↳ hep-exnucl-exEPJ Web Conf.(2022)·5 citations
10. 10*

    Derivation of the M${}_n$/M${}_p$ ratio in exotic nuclei

    E. Khan🇫🇷

    A generalized formula is provided, to calculate the M${}_n$/M${}_p$ ratio of the multipole transition matrix elements, in the framework of the so-called phenomenological analysis. It takes into account the possible difference between the neutron and proton radii and diffuseness, which can occur, especially in exotic nuclei. The validity domain of the original Bernstein formula is discussed, in the case of the proton scattering probe at few tens of MeV. The largest discrepancies are obtained for very neutron-rich nuclei (N/Z$\gtrsim$1.6) or when the electromagnetic deformation parameter is larger than the proton scattering one. The reduction of the statistical error bars, and the study of very neutron-rich nuclei at facilities of exotic beams of new generation, should favor the use of the generalized Bernstein formula.

    ↳ nucl-thnucl-exPRC(2022)·2 citations
11. 11*

    Kiloton-scale xenon detectors for neutrinoless double beta decay and other new physics searches

    A. Avasthi🇺🇸 · T.W. Bowyer🇺🇸 · C. Bray🇺🇸 · T. Brunner🇨🇦 · N. Catarineu🇺🇸 · E. Church🇺🇸 · R. Guenette🇺🇸 · S.J. Haselschwardt🇺🇸 · J.C. Hayes🇺🇸 · M. Heffner🇺🇸 · S.A. Hertel🇺🇸 · P.H. Humble🇺🇸 and 22 other authors

    Large detectors employing xenon are a leading technology in existing and planned searches for new physics, including searches for neutrinoless double beta decay ($0\nu \beta \beta$) and dark matter. While upcoming detectors will employ target masses of a ton or more, further extending gas or liquid phase Xe detectors to the kton scale would enable extremely sensitive next-generation searches for rare phenomena. The key challenge to extending this technology to detectors well beyond the ton scale is the acquisition of the Xe itself. We describe the motivation for extending Xe time projection chambers (TPCs) to the kton scale and possible avenues for Xe acquisition that avoid existing supply chains. If acquisition of Xe in the required quantities is successful, kton-scale detectors of this type could enable a new generation of experiments, including searches for $0\nu \beta \beta$ at half-life sensitivities as long as $10^{30}$ yr.

    ↳ physics.ins-dethep-exhep-phnucl-exPRD(2021)·31 citations
12. 12*

    Simulation studies for source optimization in ${}^{96}$Zr $\beta$ decay

    S. Thakur🇮🇳 · V. Nanal🇮🇳 · P.P. Singh🇮🇳 · R.G. Pillay🇮🇳 · H. Krishnamoorthy🇮🇳 · A. Mazumdar🇮🇳 · A. Reza🇮🇳 · P.K. Raina🇮🇳 · V. Vatsa🇮🇳

    The single $\beta$ decay of ${}^{96}$Zr to the ground state of ${}^{96}$Nb is spin forbidden and poses a great experimental challenge. The $\beta$ decay of ${}^{96}$Zr can be studied via coincident detection of de-exciting gamma rays in ${}^{96}$Mo, which is the end product of ${}^{96}$Nb $\beta$ decay. Simulations are done with four HPGe detector setup (~33% relative efficiency each) to optimize the source configuration. The results suggest that ~70g of 50% enriched ${}^{96}$Zr will yield sensitivity comparable to the reported results.

    ↳ physics.ins-detnucl-exNuovo Cim.C(2021)·2 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.