Mon·Apr 12, 2021Monday·April 12, 2021

1. 01*

   Exploring the N$\Lambda$-N$\Sigma$ coupled system with high precision correlation techniques at the LHC

   ALICE Collaboration

   The interaction of $\Lambda$ and $\Sigma$ hyperons (Y) with nucleons (N) is strongly influenced by the coupled-channel dynamics. Due to the small mass difference of the $\mathrm{N\Lambda }$ and $\mathrm{N\Sigma }$ systems, the sizeable coupling strength of the $\mathrm{N\Sigma }\leftrightarrow \mathrm{N\Lambda }$ processes constitutes a crucial element in the determination of the N$\Lambda$ interaction. In this letter we present the most precise measurements on the interaction of p$\Lambda$ pairs, from zero relative momentum up to the opening of the $\mathrm{N\Sigma }$ channel. The correlation function in the relative momentum space for $\mathrm{p}\Lambda \oplus \overline{\mathrm{p}}\overline{\Lambda }$ pairs measured in high-multiplicity triggered pp collisions at $\sqrt{s}=13$ TeV at the LHC is reported. The opening of the inelastic N$\Sigma$ channels is visible in the extracted correlation function as a cusp-like structure occurring at relative momentum $k^{\ast }$ = 289 MeV/$c$. This represents the first direct experimental observation of the $\mathrm{N\Sigma }\to \mathrm{N\Lambda }$ coupled channel in the p$\Lambda$ system. The correlation function is compared with recent chiral effective field theory calculations, based on different strengths of the $\mathrm{N\Sigma }\leftrightarrow \mathrm{N\Lambda }$ transition potential. A weaker coupling, as possibly supported by the present measurement, would require a more repulsive three-body NN$\Lambda$ interaction for a proper description of the $\Lambda$ in-medium properties, which has implications on the nuclear equation of state and for the presence of hyperons inside neutron stars.

   nucl-exhep-exPLB(2022)·94 citations
2. 02*

   Rigorous constraints on three-nucleon forces in chiral effective field theory from fast and accurate calculations of few-body observables

   S. Wesolowski🇺🇸 · I. Svensson🇸🇪 · A. Ekström🇸🇪 · C. Forssén🇸🇪 · R. J. Furnstahl🇺🇸 · J. A. Melendez🇺🇸 · D. R. Phillips🇺🇸

   We explore the constraints on the three-nucleon force (3NF) of chiral effective field theory ($\chi$EFT) that are provided by bound-state observables in the $A=3$ and $A=4$ sectors. Our statistically rigorous analysis incorporates experimental error, computational method uncertainty, and the uncertainty due to truncation of the $\chi$EFT expansion at next-to-next-to-leading order. A consistent solution for the ${}^3$H binding energy, the ${}^4$He binding energy and radius, and the ${}^3$H $\beta$-decay rate can only be obtained if $\chi$EFT truncation errors are included in the analysis. All of these except the $\beta$-decay rate give essentially degenerate constraints on the 3NF low-energy constants, so it is crucial for estimating these parameters. We use eigenvector continuation for fast and accurate emulation of No-Core Shell Model calculations of the considered few-nucleon observables. This facilitates sampling of the posterior probability distribution, allowing us to also determine the distributions of the hyperparameters that quantify the truncation error. We find a $\chi$EFT expansion parameter of $Q=0.33\pm 0.06$ for these observables.

   ↳ nucl-thhep-phnucl-exphysics.data-anPRC(2021)·103 citations
3. 03*

   Fast FPGA algorithm for neutron-gamma discrimination

   Haoqi Ye · Ge Jin · Lian Chen

   Various pulse shape discrimination methods have been used to solve the neutron-gamma discrimination problem. But most of them are limited to off-line calculation due to the computation amount and FPGA performance. In order to realize real time discriminating neutron and gamma, a new algorithm based on the traditional pulse shape discrimination methods was proposed in this paper. The new algorithm takes into account the physical properties of the pulse signal, which greatly reduces the computation and dead time without losing the precision, and can work on FPGA directly. It has a good performance in the actual experiment based on CLLB scintillation detector.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2022)·1 citation

* 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.