Tue·Apr 4, 2023Tuesday·April 4, 2023

1. 01*

   Direct measurement of the scattering cross sections of liquid ortho-deuterium for ultracold neutrons and comparison with model calculations

   Stefan Döge🇫🇷 · Jürgen Hingerl🇫🇷 · Winfried Petry🇩🇪 · Christoph Morkel🇩🇪

   Liquid deuterium is a fluid between the quantum and classical regimes. It attracts interest from fundamental research for the verification of quantum calculations but also from neutron physics as it is a widely used neutron moderator medium. We have measured the scattering cross sections of liquid ortho-deuterium in the ultracold-neutron range for four different temperatures (19-23 K) and compared them with calculations from a parameter-free analytical calculation model as well as with previous measurements at 19 K by another research group. All three show remarkable agreement, which establishes the validity of the calculation model and proves it is a reliable basis for the derivation of scattering kernels. The deconvolution of our measured transmission data changed the cross section results noticeably only for neutrons faster than 10 m/s. We found the total scattering cross section of liquid deuterium to be inversely proportional to velocity, as is predicted by theory.

   nucl-excond-mat.mtrl-sciPRB(2022)·0 citations
2. 02*

   Invariant-mass spectroscopy in projectile fragmentation reactions

   Robert Charity🇺🇸 · Lee Sobotka🇺🇸

   The fragmentation of a projectile into a number of pieces can lead to the creation of many resonances in different nuclei. We discuss application of the invariant-mass method to the products from such reactions to find some of the most exotic resonances located furthest beyond the proton drip line. We show examples from fragmentation of a fast ${}^{13}$O beam including the production of the newly identified ${}^9$N resonance. In extracting resonance parameters from invariant-mass spectra, accurate estimates of the background from non-resonant prompt protons are needed. This is especially important in determining the widths of wide resonances typically found at the edge of the chart of nuclides. An event-mixing recipe, where the mixed events have reduced weighting for the smaller invariant-masses, is proposed to describe this background. The weighting is based on the measured correlations of heavier hydrogen isotopes with the resonances or the projectile residues.

   nucl-exPRC(2023)·14 citations
3. 03*

   Hadron Structure using Continuum Schwinger Function Methods

   Craig D. Roberts🇨🇳

   The vast bulk of visible mass emerges from nonperturbative dynamics within quantum chromodynamics (QCD) -- the strong interaction sector of the Standard Model. The past decade has revealed the three pillars that support this emergent hadron mass (EHM); namely, a nonzero gluon mass-scale, a process-independent effective charge, and dressed-quarks with constituent-like masses. Theory is now working to expose their manifold and diverse expressions in hadron observables and highlighting the types of measurements that can be made in order to validate the paradigm. In sketching some of these developments, this discussion stresses the role of EHM in forming nucleon electroweak structure and the wave functions of excited baryons through the generation of dynamical diquark correlations; producing and constraining the dilation of the leading-twist pion distribution amplitude; shaping pion and nucleon parton distribution functions -- valence, glue and sea, including the antisymmetry of antimatter; and moulding pion and proton charge and mass distributions.

   ↳ hep-phhep-exhep-latnucl-ex+1Few Body Syst.(2023)·10 citations
4. 04*

   Energy flow in ultra-high energy cosmic ray interactions as a probe of thermalization: a potential solution to the muon puzzle

   Ronald Scaria🇮🇳 · Suman Deb🇫🇷 · Captain R. Singh🇮🇳 · Raghunath Sahoo🇮🇳

   Signatures of the formation of a strongly interacting thermalized matter of partons have been observed in nucleus-nucleus, proton-nucleus, and high-multiplicity proton-proton collisions at LHC energies. Strangeness enhancement in such ultra-relativistic heavy-ion collisions is considered to be a consequence of this thermalized phase, known as quark-gluon plasma (QGP). Simultaneously, proper modeling of hadronic energy fraction in interactions of ultra-high energy cosmic rays (UHECR) has been proposed as a solution for the muon puzzle, an unexpected excess of muons in air showers. These interactions have center-of-mass collision energies of the order of energies attained at the LHC or even higher, indicating that the possibility of a thermalized partonic state cannot be overlooked in UHECR-air interactions. This work investigates the hadronic energy fraction and strangeness enhancement to explore QGP-like phenomena in UHECR-air interactions using various high-energy hadronic models. A core-corona system with a thermalized core undergoing statistical hadronization is considered through the EPOS LHC model. In contrast, PYTHIA 8, QGSJET II-04, and SYBILL 2.3d consider string fragmentation without thermalization. We have found that EPOS LHC gives a better description of strangeness enhancement as compared to other models. We conclude that adequately treating all the relevant effects and further retuning the models is necessary to explain the observed effects.

   ↳ hep-phastro-ph.HEhep-exhep-th+1PLB(2023)·5 citations
5. 05*

   Polaronic Proton and Diproton Clustering in Neutron-Rich Matter

   Hiroyuki Tajima🇯🇵 · Hajime Moriya🇯🇵 · Wataru Horiuchi🇯🇵 · Eiji Nakano🇯🇵 · Kei Iida🇯🇵

   We show that strong spin-triplet neutron-proton interaction causes polaronic protons to occur in neutron matter at subnuclear densities and nonzero temperature. As the neutron density increases, proton spectra exhibit a smooth crossover from a bare impurity to a repulsive polaron branch; this branch coexists with an attractive polaron branch. With the neutron density increased further, the attractive polarons become stable with respect to deuteron formation. For two adjacent protons, we find that the polaron effects and the neutron-mediated attraction are sufficient to induce a bound diproton, which leads possibly to diproton formation in the surface region of neutron-rich nuclei in laboratories as well as in neutron stars.

   ↳ nucl-thastro-ph.HEcond-mat.quant-gascond-mat.supr-con+1PLB(2024)·10 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.