Mon·Feb 7, 2022Monday·February 7, 2022

1. 01*

   Directional-dependence of the event-by-event neutron-$\gamma$ multiplicity correlations in ${}^{252}$Cf(sf)

   Stefano Marin🇺🇸 · Eoin P. Sansevero🇺🇸 · M. Stephan Okar🇺🇸 · Isabel E. Hernandez🇺🇸 · Shaun D. Clarke🇺🇸 · Ramona L. Vogt🇺🇸 · Jorgen Randrup🇺🇸 · Vladimir A. Protopopescu🇺🇸 · Sara A. Pozzi🇮🇹

   We differentiate the event-by-event n-$\gamma$ multiplicity data from \ce{^{252}Cf}(sf) with respect to the energies of the emitted particles as well as their relative angles of emission. We determine that neutron emission enhances $\gamma$-ray emission around $0.7$ and $1.2$ MeV, but the only directional alignment was observed for $E_{\gamma }\le 0.7$ MeV and tended to be parallel and antiparallel to neutrons emitted in the same event. The emission of $\gamma$ rays at other energies was determined to be nearly isotropic. The presence of the emission and alignment enhancements is explained by positive correlations between neutron emission and quadrupole $\gamma$-ray emission along rotational bands in the de-exciting fragments. This observation corroborates the hypothesis of positive correlations between the angular momentum of a fragment and its intrinsic excitation energy. The results of this work are especially relevant in view of the recent theoretical and experimental interest in the generation of angular momentum in fission. Specifically, we have determined an alignment of the fragments angular momenta in a direction perpendicular to the direction of motion. We interpret the lack of $n$-$\gamma$ angular correlations for fission fragments near closed shells as a weakening of the alignment process for spherical nuclei. Lastly, we have observed that statistical $\gamma$ rays are emitted isotropically, indicating that the average angular momentum removed by this radiation is small. These results, and the analysis tools presented in this work, represent a stepping stone for future analysis of $n$-$\gamma$ emission correlations and their connection to angular momentum properties.

   nucl-exPRC(2022)·13 citations
2. 02*

   A Challenge for Discrimination of Color-Singlet versus Color-Octet Quarkonium Production

   Andrew J. Larkoski🇺🇸

   The precise mechanism for production of quarkonium at hadron colliders is still an open question. Within non-relativistic quantum chromodynamics, quarkonium production cross sections can be factorized into short-distance, perturbative contributions and universal, non-perturbative, long-distance matrix elements, and then summed over quantum numbers of the heavy quark pair. In principle, at short-distances, the heavy quark pair can be either in a color-singlet or color-octet state, and it is desirable to establish the relative contributions to compare with data and to make predictions in different experimental environments. From the explicit form of the lowest-order perturbative matrix elements for color-singlet and color-octet production, we show that the structure of the optimal observable for discrimination on phase space, the likelihood ratio, has strong dependence on the angular momentum state of the heavy quark pair. This presents an obstruction for construction of a single, robust discrimination observable that can be applied to production of an arbitrary quarkonium state.

   ↳ hep-phhep-exnucl-exnucl-th1 citation
3. 03*

   Observing true tauonium via two-photon fusion at $e^{+}{e}^{-}$ and hadron colliders

   David d'Enterria🇨🇭 · Hua-Sheng Shao🇫🇷

   The feasibility of observing true tauonium, the bound state of two tau leptons, ${\mathcal{T}}_0\equiv ({\tau }^{+}{\tau }^{-}{)}_0$, via photon-photon collisions at $e^{+}{e}^{-}$ colliders and at the LHC, is studied. The production cross sections of the process $\gamma \gamma \to {\mathcal{T}}_0\to \gamma \gamma$ -- as well as those of all relevant backgrounds: spin-0 and 2 charmonium resonances decaying to diphotons, and light-by-light scattering -- are computed in the equivalent photon approximation for $e^{+}{e}^{-}$ collisions at BES III ($\sqrt{s}=3.8$ GeV), Belle II ($\sqrt{s}=10.6$ GeV), and FCC-ee ($\sqrt{s}=91.2$ GeV), as well as for ultraperipheral p-p, p-Pb, and Pb-Pb collisions at the LHC. Despite small ${\mathcal{T}}_0$ production cross sections and a final state swamped by decays from overlapping pseudoscalar and tensor charmonium states -- the ${\chi }_{c2}$, ${\eta }_{\mathrm{c}}(2S)$, and ${\chi }_{c0}$ states have masses only 2.5, 84, and 139 MeV away, respectively, from the ${\mathcal{T}}_0$ peak -- evidence and observation of the ground state of the heaviest leptonium appears feasible at Belle II and FCC-ee, respectively, with in-situ high-precision measurements of the irreducible backgrounds.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2022)·24 citations
4. 04*

   Muon Track Reconstruction in a Segmented Bolometric Array Using Multi-Objective Optimization

   J. Yocum🇺🇸 · D. Mayer🇺🇸 · J. L. Ouellet🇺🇸 · L. Winslow🇺🇸

   Recent advances in segmented solid-state detector arrays for rare-event searches have allowed the technology to approach the ton-scale in detector mass and the scale of meters in size. Often focused around searches for neutrinoless double-beta decay or direct dark matter detection, such experiments also have the capability to search for exotic particles that leave track-like signatures across their volume. However, the segmented nature of such detector arrays often sets the spatial resolution and makes the problem of reconstructing track-like paths non-trivial. In this paper, we present an algorithm that improves reconstruction of track-like events in segmented detectors using multi-objective optimization - a computational technique that optimizes more than one cost function at a time without specifying a quantitative weighting between them. Such a technique allows the reconstruction of tracks through a detector and the determination of path-lengths through individual elements. When combined with the reconstructed energy depositions in each element this allows for a calculation of the stopping power of track-like particles and opens the door to searches for particles with abnormal stopping power like monopoles or lightly-ionizing particles (LIPs). Results are presented which evaluate the precision of the reconstruction tools as they currently stand against Monte Carlo generated data. The algorithm is presented in the context of the CUORE experiment, but has applications to other segmented calorimeter detectors.

   ↳ physics.ins-detnucl-exJINST(2022)·4 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.