Fri·Apr 5, 2024Friday·April 5, 2024

1. 01*

   Direct Experimental Constraints on the Spatial Extent of a Neutrino Wavepacket

   Joseph Smolsky🇺🇸 · Kyle G Leach🇺🇸 · Ryan Abells🇨🇦 · Pedro Amaro🇵🇹 · Adrien Andoche🇫🇷 · Keith Borbridge🇺🇸 · Connor Bray🇺🇸 · Robin Cantor🇺🇸 · David Diercks🇺🇸 · Spencer Fretwell🇺🇸 · Stephan Friedrich🇺🇸 · Abigail Gillespie🇺🇸 and 26 other authors

   Despite their high relative abundance in our Universe, neutrinos are the least understood fundamental particles of nature. They also provide a unique system to study quantum coherence and the wavelike nature of particles in fundamental systems due to their extremely weak interaction probabilities. In fact, the quantum properties of neutrinos emitted in experimentally relevant sources are virtually unknown and the spatial extent of the neutrino wavepacket is only loosely constrained by reactor neutrino oscillation data with a spread of 13 orders of magnitude. Here, we present the first direct limits of this quantity through a new experimental concept to extract the energy width, ${\sigma }_{\text{N},E}$, of the recoil daughter nucleus emitted in the nuclear electron capture (EC) decay of ${}^7$Be. The final state in the EC decay process contains a recoiling ${}^7$Li nucleus and an electron neutrino (${\nu }_e$) which are entangled at their creation. The ${}^7$Li energy spectrum is measured to high precision by directly embedding ${}^7$Be radioisotopes into a high resolution superconducting tunnel junction that is operated as a cryogenic sensor. The lower limit on the spatial uncertainty of the recoil daughter was found to be ${\sigma }_{\text{N},x}\ge 6.2$\,pm, which implies the final-state system is localized at a scale more than a thousand times larger than the nucleus itself. From this measurement, the first direct lower limits on the spatial extent of the neutrino wavepacket were extracted using two different theoretical methods. These results have wide-reaching implications in several areas including the nature of spatial localization at sub-atomic scales, interpretation of neutrino physics data, and the potential reach of future large-scale experiments.

   nucl-exhep-exquant-phNature(2025)·22 citations
2. 02*

   A first extraction of the weak magnetism form factor and Fierz interference term from the ${}^{114}$In $\to$ ${}^{114}$Sn Gamow-Teller transition

   L. De Keukeleere🇧🇪 · D. Rozpedzik🇵🇱 · N. Severijns🇧🇪 · K. Bodek🇵🇱 · L. Hayen🇫🇷 · K. Lojek🇵🇱 · M. Perkowski🇵🇱 · S. Vanlangendonck🇧🇪

   Spectrum shape measurements in nuclear $\beta$ decay can be used to test physics beyond the Standard Model with results being complementary to high-energy collider experiments. In particular, Beyond Standard Model sensitivity of the weak interaction is expressed through the so-called Fierz interference term. Additionally, the $\beta$ spectrum shape is a useful tool to probe Standard Model effects, among which the most prominent is \textit{weak magnetism}, a higher-order recoil correction induced by nuclear pion exchange. To study effects in the $\beta$ spectrum shape at a precision level competitive with the LHC, a new spectrometer was designed and built. It consists of a 3D low-pressure gas electron tracker and a plastic scintillator used for triggering the data acquisition and recording the $\beta$ particle energy. In this Letter, the results from $\beta$ spectrum shape measurements on the allowed Gamow-Teller transition ${}^{114}\text{In}{\to }^{114}\text{Sn}$ are presented, including a first extraction of the weak magnetism form factor in the high nuclear mass range and a new estimate of the $90\%$ confidence interval for the Fierz interference term.

   nucl-ex4 citations
3. 03*

   Information entropy for central ${}^{197}$Au+${}^{197}$Au collisions with the ultrarelativistic quantum molecular dynamics model

   Xian-Gai Deng🇨🇳 · Yu-Gang Ma🇨🇳

   This study investigates the multiplicity information entropy of hadrons, anti-hadrons, baryons, and net-protons in central \(^{197}\)Au+\(^{197}\)Au collisions with impact parameters of 0$-$3 fm, using the ultrarelativistic quantum molecular dynamics model (UrQMD) across various center-of-mass energies (\(\sqrt{s_{\rm NN}}\)) from 5.0 to 54.4 GeV. Our simulations employ hydrodynamic modes with different equations of state (EoS) and a default mode without hydrodynamics. The results reveal that the information entropies of baryons and net-protons are sensitive to the selected EoS. In particular, enhancements of the information entropies around \(\sqrt{s_{\rm NN}} \sim 30\) GeV, especially with chiral hadron gas and Bag model EoS, indicate a phase transition or critical endpoint behavior. These findings highlight the importance of the EoS in understanding the thermodynamic properties of matter produced in high-energy collisions.

   ↳ nucl-thnucl-exPRC(2025)·4 citations
4. 04*

   Nuclear uncertainties associated with the ejecta of a neutron-star black-hole accretion disk

   M. R. Mumpower🇺🇸 · T. M. Sprouse🇺🇸 · J. M. Miller🇺🇸 · K. A. Lund🇺🇸 · J. Cabrera Garcia🇲🇽 · N. Vassh🇨🇦 · G. C. McLaughlin🇺🇸 · R. Surman🇺🇸

   The simulation of heavy element nucleosynthesis requires input from yet-to-be-measured nuclear properties. The uncertainty in the values of these off-stability nuclear properties propagates to uncertainties in the predictions of elemental and isotopic abundances. However, for any given astrophysical explosion, there are many different trajectories, i.e. temperature and density histories, experienced by outflowing material and thus different nuclear properties can come into play. We consider combined nucleosynthesis results from 460,000 trajectories from a neutron star-black hole accretion disk and the find spread in elemental predictions due solely to unknown nuclear properties to be a factor of a few. We analyze this relative spread in model predictions due to nuclear variations and conclude that the uncertainties can be attributed to a combination of properties in a given region of the abundance pattern. We calculate a cross-correlation between mass changes and abundance changes to show how variations among the properties of participating nuclei may be explored. Our results provide further impetus for measurements of multiple quantities on individual short-lived neutron-rich isotopes at modern experimental facilities.

   ↳ astro-ph.HEastro-ph.SRnucl-exnucl-thApJ(2024)·7 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.