Nuclear Theory·nucl-th

Monday·March 13, 2023

7 papers—2 primary·5 cross-listed

03
Towards Resolving the Gallium Anomaly
Vedran Brdar🇨🇭 · Julia Gehrlein🇨🇭 · Joachim Kopp🇨🇭
A series of experiments studying neutrinos from intense radioactive sources have reported a deficit in the measured event rate which, in combination, has reached a statistical significance of $\sim 5 σ$ . In this paper, we explore avenues for explaining this anomaly, both within the Standard Model and beyond. First, we discuss possible biases in the predicted cross section for the detection reaction $ν_{e} +^{71} Ga \to e^{-} +^{71} Ge$ , which could arise from mismeasurement of the inverse process, $^{71} Ge$ decay, or from the presence of as yet unknown low-lying excited states of $^{71} Ga$ . The latter would imply that not all $^{71} Ge$ decays go to the ground state of $^{71} Ga$ , so the extraction of the ground state-to-ground state matrix element relevant for neutrino capture on gallium would be incorrect. Second, we scrutinize the measurement of the source intensity in gallium experiments, and we point out that a $\sim 2%$ error in the branching ratios for $^{51} Cr$ decay would be enough to explain the anomaly. Third, we investigate the calibration of the radiochemical germanium extraction efficiency as a possible origin of anomaly. Finally, we outline several new explanations beyond the Standard Model, including scenarios with sterile neutrinos coupled to fuzzy dark matter or to dark energy, as well as a model with decaying sterile neutrinos. We critically assess the viability of these scenarios, and others that have been proposed, in a summary table.
↳ hep-phhep-exnucl-thJHEP(2023)·30 citations
04
Simulating jets and heavy quarks in the Glasma using the colored particle-in-cell method
Dana Avramescu🇫🇮 · Virgil Băran🇷🇴 · Vincenzo Greco🇮🇹 · Andreas Ipp🇦🇹 · David. I. Müller🇦🇹 · Marco Ruggieri🇮🇹
We explore the impact of strong classical color fields, which occur in the earliest stages of heavy-ion collisions and are known as the Glasma, on the classical transport of hard probes, namely heavy quarks and jets. To achieve this, we simulate SU(3) color fields using classical real-time lattice gauge theory and couple them to an ensemble of test particles whose dynamics are described by Wong's equations. We provide an overview of how classical color algebras are constructed and introduce a method to generate random classical SU(3) color charges. We extensively test our numerical particle solver in the limits of infinitely massive heavy quarks and ultra-relativistic light-like jets and obtain excellent quantitative agreement with previous studies. Going towards realistic masses and initial moment, we extract longitudinal and transverse momentum broadening for heavy quarks and jets. The resulting accumulated momenta and the anisotropy of these dynamical hard probes exhibit deviations from limiting scenarios, showing that the full dynamics have a significant effect.
↳ hep-phhep-latnucl-thPRD(2023)·84 citations
05
A similarity renormalization group approach to Green's function methods
Antoine Marie · Pierre-François Loos
The family of Green's function methods based on the $G W$ approximation has gained popularity in the electronic structure theory thanks to its accuracy in weakly correlated systems combined with its cost-effectiveness. Despite this, self-consistent versions still pose challenges in terms of convergence. A recent study \href{https://doi.org/10.1063/5.0089317}{[J. Chem. Phys. 156, 231101 (2022)]} has linked these convergence issues to the intruder-state problem. In this work, a perturbative analysis of the similarity renormalization group (SRG) approach is performed on Green's function methods. The SRG formalism enables us to derive, from first principles, the expression of a naturally static and Hermitian form of the self-energy that can be employed in quasiparticle self-consistent $G W$ (qs $G W$ ) calculations. The resulting SRG-based regularized self-energy significantly accelerates the convergence of qs $G W$ calculations, slightly improves the overall accuracy, and is straightforward to implement in existing code.
↳ physics.chem-phcond-mat.mtrl-scicond-mat.str-elnucl-thJ.Chem.Theor.Comput.(2023)·11 citations
06
Femtoscopic correlation function for the $T_{cc} (3875)^{+}$ state
I. Vidana🇮🇹 · A. Feijoo🇪🇸 · M. Albaladejo🇪🇸 · J. Nieves🇪🇸 · E. Oset🇪🇸
We have conducted a study of the femtoscopic correlation functions for the $D^{0} D^{*+}$ and $D^{+} D^{* 0}$ channels that build the $T_{cc}$ state. We develop a formalism that allows us to factorize the scattering amplitudes outside the integrals in the formulas, and the integrals involve the range of the strong interaction explicitly. For a source of size of 1 fm, we find values for the correlation functions of the $D^{0} D^{*+}$ and $D^{+} D^{* 0}$ channels at the origin around 30 and 2.5, respectively, and we see these observables converging to unity already for relative momenta of the order of 200 MeV. We conduct tests to see the relevance of the different contributions to the correlation function and find that it mostly provides information on the scattering length, since the presence of the source function in the correlation function introduces an effective cut in the loop integrals that makes them quite insensitive to the range of the interaction.
↳ hep-phnucl-thPLB(2023)·62 citations
07
New Constraints on Sodium Production in Globular Clusters From the $^{23}$ Na $(^{3}$ He $, d)^{24}$ Mg Reaction
C.Marshall · K.Setoodehnia · G.C.Cinquegrana · J.H.Kelly · F.Portillo Chaves · A.Karakas · R.Longland
The star to star anticorrelation of sodium and oxygen {is} a defining feature of globular clusters, but, to date, the astrophysical site responsible for this unique chemical signature remains unknown. Sodium enrichment within these clusters depends sensitively on reaction rate of the sodium destroying reactions $^{23}$ Na $(p, γ)$ and $^{23}$ Na $(p, α)$ . In this paper, we report the results of a $^{23}$ Na $(^{3} He, d)^{24}$ Mg transfer reaction carried out at Triangle Universities Nuclear Laboratory using a $21$ MeV $^{3}$ He beam. Astrophysically relevant states {in $^{24}$ Mg} between $11 < E_{x} < 12$ MeV were studied using high resolution magnetic spectroscopy, thereby allowing the extraction of excitation energies and spectroscopic factors. Bayesian methods are combined with the distorted wave Born approximation to assign statistically meaningful uncertainties to the extracted spectroscopic factors. For the first time, these uncertainties are propagated through to the estimation of proton partial widths. Our experimental data are used to calculate the reaction rate. The impact of the new rates are investigated using asymptotic giant branch star models. It is found that while the astrophysical conditions still dominate the total uncertainty, intra-model variations on sodium production from the $^{23}$ Na $(p, γ)$ and $^{23}$ Na $(p, α)$ reaction channels are a lingering source of uncertainty.
↳ nucl-exnucl-thPRC(2023)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE

Towards Resolving the Gallium Anomaly

Simulating jets and heavy quarks in the Glasma using the colored particle-in-cell method

A similarity renormalization group approach to Green's function methods

Femtoscopic correlation function for the Tcc​(3875)+ state

New Constraints on Sodium Production in Globular Clusters From the 23Na(3He,d)24Mg Reaction

Affiliations

Femtoscopic correlation function for the $T_{cc} (3875)^{+}$ state

New Constraints on Sodium Production in Globular Clusters From the $^{23}$ Na $(^{3}$ He $, d)^{24}$ Mg Reaction