Tue·Aug 29, 2023Tuesday·August 29, 2023

1. 01*

   Double-pion electroproduction off protons in deuterium: Quasifree cross sections and final-state interactions

   Iu.A. Skorodumina · G.V. Fedotov · R.W. Gothe · the CLAS Collaboration

   The single-differential and fully integrated cross sections for quasifree ${\pi }^{+}{\pi }^{-}$ electroproduction off protons bound in deuterium have been extracted for the first time. The experimental data were collected at Jefferson Laboratory with the CLAS detector. The measurements were performed in the kinematic region of the invariant mass $W$ from 1.3 to 1.825 GeV and the photon virtuality $Q^2$ from 0.4 to 1.0 GeV${}^2$. Sufficient experimental statistics allowed for narrow binning in all kinematic variables, while maintaining a small statistical uncertainty. The extracted cross sections were compared with the corresponding cross sections off free protons, which allowed us to obtain an estimate of the contribution from events in which interactions between the final-state hadrons and the spectator neutron took place.

   nucl-exhep-exPRC(2024)·3 citations
2. 02*

   Core destruction in knockout reactions

   C.A. Bertulani🇺🇸

   A model is presented to calculate projectile core destruction in knockout reactions. It incorporates physics arguments similar to the formulation of the state of the art theory to calculate stripping and diffraction dissociation cross sections in heavy ion collisions with bombarding energies around 100 MeV/nucleon and larger. It is shown that secondary collisions between the incoming and struck nucleons and the projectile core decrease the core survival probability by as much as 9.5\%. However, no clear evidence is found for reduction of the cross section with increasing binding energy of the removed nucleon.

   ↳ nucl-thnucl-exPLB(2023)·11 citations
3. 03*

   Constraining the pion distribution amplitude using Drell-Yan reactions on a proton

   H.-Y. Xing🇨🇳 · M. Ding🇩🇪 · Z.-F. Cui🇨🇳 · A. V. Pimikov🇷🇺 · C. D. Roberts🇨🇳 · S. M. Schmidt🇩🇪

   Using a reaction model that incorporates pion bound state effects and continuum results for proton parton distributions and the pion distribution amplitude, ${\phi }_{\pi }$, we deliver parameter-free predictions for the ${\mu }^{+}$ angular distributions in $\pi N\to {\mu }^{+}{\mu }^{-}X$ reactions on both unpolarised and polarised targets. The analysis indicates that such angular distributions are sensitive to the pointwise form of ${\phi }_{\pi }$ and suggests that unpolarised targets are practically more favourable. The precision of extant data is insufficient for use in charting ${\phi }_{\pi }$; hence, practical tests of this approach to charting ${\phi }_{\pi }$ must await data with improved precision from new-generation experiments. The reaction model yields a nonzero single-spin azimuthal asymmetry, without reference to $T$-odd parton distribution functions (DFs). This may necessitate additional care when attempting to extract such $T$-odd DFs from data.

   ↳ hep-phhep-exhep-latnucl-ex+1PLB(2024)·7 citations
4. 04*

   Ab initio investigation of the ${}^7$Li($p,e^{+}{e}^{-}$)${}^8$Be process and the X17 boson

   P. Gysbers🇨🇦 · P. Navratil🇨🇦 · K. Kravvaris🇺🇸 · G. Hupin🇫🇷 · S. Quaglioni🇺🇸

   Observations of anomalies in the electron-positron angular correlations in high-energy decays in ${}^4$He, ${}^8$Be, and ${}^{12}$C have been reported recently by the ATOMKI collaboration. These could be explained by the creation and subsequent decay of a new boson with a mass of $\sim 17$ MeV. Theoretical understanding of pair creation in the proton capture reactions used in these experiments is important for the interpretation of the anomalies. We apply the ab initio No-Core Shell Model with Continuum (NCSMC) to the proton capture on ${}^7$Li. The NCSMC describes both bound and unbound states in light nuclei in a unified way with chiral two- and three-nucleon interactions as the only input. We investigate the structure of ${}^8$Be, the $p{+}^7$Li elastic scattering, the ${}^7$Li($p,\gamma$)${}^8$Be cross section and the internal pair creation ${}^7$Li($p,e^{+}{e}^{-}$)${}^8$Be. We discuss the impact of a proper treatment of the initial scattering state on the electron-positron angular correlation spectrum and compare our results to available ATOMKI data sets. Finally, we calculate ${}^7$Li($p,X$)${}^8$Be cross sections for several proposed models of the hypothetical X17 particle.

   ↳ nucl-thhep-phnucl-exPRC(2024)·11 citations
5. 05*

   Production of various elements in ultraperipheral ${}^{208}$Pb-${}^{208}$Pb collisions at the LHC

   U.A. Dmitrieva🇷🇺 · I.A. Pshenichnov🇷🇺

   As predicted by theory and confirmed by measurements, one, two or three neutrons are emitted frequently in ultraperipheral collisions (UPCs) of heavy relativistic nuclei, in particular, ${}^{208}$Pb. The exchange of low-energy Weizsäcker--Williams photons dominates in such interactions. This leads to the excitation and decay of Giant Dipole Resonances (GDR) in colliding nuclei below the proton emission threshold. Less is known about the electromagnetic dissociation of ${}^{208}$Pb induced by energetic photons leading to violent fragmentation of ${}^{208}$Pb. The UPCs of lead nuclei at the LHC were modelled with Relativistic ELectromagnetic Dissociation (RELDIS) model to evaluate the contribution of photonuclear reactions in the domain of quasideuteron absorption and at higher photon energies. It was demonstrated that due to the presence of a single heavy residue in the final state mostly accompanied by free protons and neutrons, the cross sections of the production of specific elements can be well approximated by the proton emission cross sections, which can be measured in the ALICE experiment at the LHC.

   ↳ nucl-thnucl-exPhys.Part.Nucl.Lett.(2023)·3 citations
6. 06*

   Charm balance function in relativistic heavy-ion collisions

   Tribhuban Parida🇮🇳 · Piotr Bozek🇵🇱 · Sandeep Chatterjee🇮🇳

   We calculate the balance function for charm in relativistic heavy-ion collisions. The distribution of pairs of charm-anticharm quarks produced in hard processes in the early stages of the nucleus-nucleus collision evolves in the dense fireball formed in the collision. The evolution of the dense matter is described using a relativistic viscous hydrodynamic model and the quark diffusion with a Langevin equation. The evolution of the charm quark balance function from the formation of the charm-anticharm pair up to the freeze-out traces the partial thermalization of the heavy quarks in the dense matter. For the balance function in azimuthal angle we reproduce the collimation effect due to the transverse flow. The evolution in rapidity shows the thermalization of the longitudinal velocity of the quark in the fluid. We provide predictions for the one and two-dimensional balance functions for $D^0$-$\overline{D^0}$ mesons produced in ultarelativistic Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV. The shape of the charm balance function in relative rapidity is sensitive to the rescattering of heavy quarks in the early stages of the collision, while the shape of the balance function in azimuthal angle is sensitive to the rescattering in the latter stages.

   ↳ nucl-thhep-phnucl-exPRC(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.