Wed·Jun 7, 2023Wednesday·June 7, 2023

1. 01*

   The Gallium Anomaly

   Steven R. Elliott🇺🇸 · Vladimir Gavrin🇷🇺 · Wick Haxton🇺🇸

   In order to test the end-to-end operations of gallium solar neutrino experiments, intense electron-capture sources were fabricated to measure the responses of the radiochemical SAGE and GALLEX/GNO detectors to known fluxes of low-energy neutrinos. Such tests were viewed at the time as a cross-check, given the many tests of ${}^{71}$Ge recovery and counting that had been routinely performed, with excellent results. However, the four ${}^{51}$Cr and ${}^{37}$Ar source experiments yielded rates below expectations, a result commonly known as the Ga anomaly. As the intensity of the electron-capture sources can be measured to high precision, the neutrino lines they produce are fixed by known atomic and nuclear rates, and the neutrino absorption cross section on ${}^{71}$Ga is tightly constrained by the lifetime of ${}^{71}$Ge, no simple explanation for the anomaly has been found. To check these calibration experiments, a dedicated experiment BEST was performed, utilizing a neutrino source of unprecedented intensity and a detector optimized to increase statistics while providing some information on counting rate as a function of distance from the source. The results BEST obtained are consistent with the earlier solar neutrino calibration experiments, and when combined with those measurements, yield a Ga anomaly with a significance of approximately $4\sigma$, under conservative assumptions. But BEST found no evidence of distance dependence and thus no explicit indication of new physics. In this review we describe the extensive campaigns carried out by SAGE, GALLEX/GNO, and BEST to demonstrate the reliability and precision of their experimental procedures, including ${}^{71}$Ge recovery, counting, and analysis. We also describe efforts to define uncertainties in the neutrino capture cross section. With the results from BEST, an anomaly remains.

   nucl-exnucl-thPPNP(2024)·40 citations
2. 02*

   Entanglement Maximization in Low-Energy Neutron-Proton Scattering

   Gerald A. Miller🇺🇸

   The entanglement properties of neutron-proton scattering are investigated using a measure that counts the number of entangled pairs produced by the action of a scattering operator on a given initial neutron-proton state. All phase shifts relevant for scattering at laboratory energies up to 350 MeV are used. Entanglement is found to be maximized in very low energy scattering. At such energies the Hamiltonian obeys Wigner SU(4) symmetry, and an entanglement maximum is a sign of that symmetry. At higher energies the angular dependence of entanglement is strong and the entanglement is large for many scattering angles. The tensor force is shown to play a significant role in producing entanglement at lab kinetic energies greater than about 50 MeV.

   ↳ nucl-thhep-phnucl-exquant-phPRC(2023)·46 citations
3. 03*

   All-Orders Evolution of Parton Distributions: Principle, Practice, and Predictions

   Pei-Lin Yin🇨🇳 · Yin-Zhen. XuID · Zhu-Fang Cui🇨🇳 · Craig D. Roberts🇨🇳 · José Rodríguez-Quintero🇪🇸

   Parton distribution functions (DFs) are defining expressions of hadron structure. Exploiting the role of effective charges in quantum chromodynamics, an algebraic scheme is described which, given any hadron's valence parton DFs at the hadron scale, delivers predictions for all its DFs -- unpolarised and polarised -- at any higher scale. The scheme delivers results that are largely independent of both the value of the hadron scale and the pointwise form of the charge; and, inter alia, enables derivation of a model-independent identity that relates the strength of the proton's gluon helicity DF, $\Delta G_p^{\zeta }$, to that of the analogous singlet polarised quark DF and valence quark momentum fraction. Using available data fits and theory predictions, the identity yields $\Delta G_p({\zeta }_{\mathrm{C}}=\surd 3\mathrm{GeV})=1.48(10)$. It furthermore entails that the measurable quark helicity contribution to the proton spin is ${\tilde{a}}_{0p}^{{\zeta }_{\mathrm{C}}}=0.32(3)$, thereby reconciling contemporary experiment and theory.

   ↳ hep-phhep-exhep-latnucl-ex+1Chin.Phys.Lett.(2023)·30 citations
4. 04*

   Effect of a magnetic field on the thermodynamic properties of a high-temperature hadron resonance gas with van der Waals interactions

   Bhagyarathi Sahoo🇮🇳 · Kshitish Kumar Pradhan🇮🇳 · Dushmanta Sahu🇮🇳 · Raghunath Sahoo🇮🇳

   We study the behavior of a hadronic matter in the presence of an external magnetic field within the van der Waals hadron resonance gas model, considering both attractive and repulsive interactions among the hadrons. Various thermodynamic quantities like pressure ($P$), energy density ($\epsilon$), magnetization ($\mathcal{M}$), entropy density ($s$), squared speed of sound ($c_{\mathrm{s}}^2$), and specific-heat capacity at constant volume ($c_v$) are calculated as functions of temperature ($T$) and static finite magnetic field ($eB$). We also consider the effect of baryochemical potential (${\mu }_B$) on the above-mentioned thermodynamic observables in the presence of a magnetic field. Further, we estimate the magnetic susceptibility (${\chi }_{\mathrm{M}}^2$), relative permeability (${\mu }_{\mathrm{r}}$), and electrical susceptibility (${\chi }_{\mathrm{Q}}^2$) which can help us to understand the system better. Through this model, we quantify a liquid-gas phase transition in the T-eB-${\mu }_B$ phase space.

   ↳ hep-phhep-exhep-thnucl-ex+1PRD(2023)·24 citations
5. 05*

   Multiplicity and Transverse Spherocity dependence of $⟨p_{\mathrm{T}}⟩$ fluctuations of charged particles in p$-$p collisions at $\sqrt{s}$ = 7 and 13 TeV

   Subhadeep Roy🇮🇳 · Tulika Tripathy🇮🇳 · Sadhana Dash🇮🇳

   The multiplicity dependence of event-by-event fluctuations in mean transverse momentum, $⟨p_{\mathrm{T}}⟩$, of charged particles has been studied in p$-$p collisions at $\sqrt{s}$ = 7 TeV and 13 TeV using the PYTHIA 8 event generator. The charged particles were selected in kinematic range of $0.15<p_{\mathrm{T}}<2$ GeV$/c$ and $|\eta |<0.8$. The dynamical fluctuations would indicate towards the correlated emission of particles. The measurements in A$-$A and p$-$p collisions has shown a decrease in the strength of $⟨p_{\mathrm{T}}⟩$ fluctuations with the average charged particle multiplicity. The effects of various microscopic processes like color reconnection and multi-partonic interactions has been studied. A minimal dependency on the collision energy is also observed. Furthermore, the fluctuation observables are investigated in the intervals of transverse spherocity in order to comprehend the relative contributions resulting from hard scattering and underlying events. The present study would act as a baseline for future measurements in A$-$A as well as p$-$p collisions at the LHC.

   ↳ hep-phnucl-ex1 citation
6. 06*

   Potential Constraints to Neutrino-Nucleus Interactions Based on Electron Scattering Data

   V. Pandey🇺🇸

   A thorough understanding of neutrino-nucleus interactions physics is crucial to achieving precision goals in broader neutrino physics programs. The complexity of nuclei comprising the detectors and limited understanding of their weak response constitutes one of the biggest systematic uncertainties in neutrino experiments - both at intermediate energies affecting the short- and long-baseline neutrino programs as well as at lower energies affecting coherent scattering neutrino programs. While electron and neutrino interactions are different at the primary vertex, many underlying relevant physical processes in the nucleus are the same in both cases, and electron scattering data collected with precisely controlled kinematics, large statistics and high precision allows one to constrain nuclear properties and specific interaction processes. To this end, electron-nucleus scattering experiments provide vital complementary information to test, assess and validate different nuclear models and event generators intended to be used in neutrino experiments. In fact, for many decades, the study of electron scattering off a nucleus has been used as a tool to probe the properties of that nucleus and its electromagnetic response. While previously existing electron scattering data provide important information, new and proposed measurements are tied closely to what is required for the neutrino program in terms of expanding kinematic reach, the addition of relevant nuclei and information on the final states hadronic system.

   ↳ hep-exhep-phnucl-exnucl-thPhys.Sci.Forum(2023)·2 citations
7. 07*

   Fast trajectory reconstruction techniques for the large acceptance magnetic spectrometer VAMOS++

   A. Lemasson🇫🇷 · M. Rejmund🇫🇷

   The large angular and momentum acceptance magnetic spectrometer VAMOS++, at GANIL, France, is frequently used for nuclear structure and reaction dynamics studies. It provides an event-by-event identification of heavy ions produced in nuclear reactions at beam energies around the Coulomb barrier. The highly non-linear ion optics of VAMOS++ requires the use of the heavy ion trajectory reconstruction methods in the spectrometer to obtain the high-resolution definition of the measured atomic mass number. Three different trajectory reconstruction methods, developed and used for VAMOS++, are presented in this work. The performances obtained, in terms of resolution of reconstructed atomic mass number, are demonstrated and discussed using a single data-set of fission fragments detected in the spectrometer.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2023)·12 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.