Tue·Mar 2, 2021Tuesday·March 2, 2021

1. 01*

   Experimental electronic stopping cross section of tungsten for light ions in a large energy interval

   M. V. Moro🇸🇪 · P. M. Wolf🇸🇪 · B. Bruckner🇸🇪 · F. Munnik🇩🇪 · R. Heller🇩🇪 · P. Bauer🇩🇪 · D. Primetzhofer🇸🇪

   Electronic stopping cross section of tungsten for light ions was experimentally measured in a wide energy interval (20 to 6000 keV for protons and 50 to 9000 keV for helium) in backscattering and transmission geometries. The measurements were carried out in three laboratories (Austria, Germany and Sweden) using five different set-ups, the stopping data deduced from different data sets showed excellent agreement amongst each other, with total uncertainty varying within 1.5 - 3.8\% for protons and 2.2 - 5.5\% for helium, averaged over the respective energy range of each data set. The final data is compared to available data and to widely adopted semi-empirical and theoretical approaches, and found to be in good agreement with most adopted models at energies around and above the stopping maximum. Most importantly, our results extend the energy regime towards lower energies, and are thus of high technological relevance, e.g., in fusion research. At these low energies, our findings also revealed that tungsten - featured with fully and partially occupied f- and d-subshells, respectively, can be modeled as an electron gas for the energy loss process.

   nucl-exNucl.Instrum.Meth.B(2021)·0 citations
2. 02*

   Hybrid model of proton structure functions

   S. A. Kulagin🇷🇺 · V. V. Barinov🇷🇺

   We develop a "hybrid" model of the proton inelastic structure functions applicable in a wide region of invariant mass of produced states $W$ and invariant momentum transfer $Q$ including deep inelastic scattering (DIS), nucleon resonance production as well as the region close to inelastic threshold. DIS is described in terms of the parton distributions together with higher-twist corrections from an available global QCD fit. The resonant part is addressed in terms of the Breit-Wiegner contributions from five states including the $\Delta (1232)$ resonance, the $N(1440)$ Roper resonance, and three effective resonances describing the second and third resonance regions. The couplings of the nucleon resonances to photon are described in terms of helicity amplitudes. The nonresonant background is addressed in terms of DIS structure functions smoothly extrapolated to low-$W$ and low-$Q$ values with the proper behavior at the real photon limit $Q^2=0$ as well as near the inelastic threshold. We independently treat the transverse $F_T$ and the longitudinal $F_L$ structure function and fix the model parameters from a global analysis of the world hydrogen electroproduction and photoproduction cross-section data. We demonstrate a very good performance of the model by comparing our predictions with data on differential cross sections and the structure functions $F_2$ and $R=F_L/F_T$.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2022)·4 citations
3. 03*

   Rosenbluth separation of $\mathbf{d}{\mathbf{\sigma }}_{\mathbf{L}}/\mathbf{dt}$ and $\mathbf{d}{\mathbf{\sigma }}_{\mathbf{T}}/\mathbf{dt}$ in ${\mathbf{\pi }}^0$ deeply virtual electroproduction from the proton

   I. Korover🇺🇸 · R.G. Milner🇺🇸

   We report on a Rosenbluth separation using previously published data by the CLAS collaboration in Hall B, Jefferson Lab for exclusive ${\pi }^0$ deeply virtual electroproduction (DVEP) from the proton at a mean $Q^2$ of $\approx$ 2 (GeV/c)${}^2$. The central question we address is the applicability of factorization in ${\pi }^0$ DVEP at these kinematics. The results of our Rosenbluth separation clearly demonstrate the dominance of the longitudinal contribution to the cross section. The extracted longitudinal and transverse contributions are in agreement with previous data from Hall A at Jefferson Lab, but over a much wider $-t$ range (0.12 - 1.8 (GeV/c)${}^2$). The measured dominance of the longitudinal contribution at $Q^2\approx$ 2 (GeV/c)${}^2$ is consistent with the expectation of the handbag factorization theorem. We find that ${\sigma }_L(t)\sim 1/(-t)$ for $-t>$ 0.5 (GeV/c)${}^2$. Determination of both longitudinal and transverse contributions to the deeply virtual ${\pi }^0$ electroproduction cross section allows extraction of additional GPDs.

   ↳ hep-phnucl-exnucl-th2 citations
4. 04*

   High-precision determination of the $K_{e3}$ radiative corrections

   Chien-Yeah Seng🇩🇪 · Daniel Galviz🇩🇪 · Mikhail Gorchtein🇩🇪 · Ulf-G. Meißner🇩🇪

   We report a high-precision calculation of the Standard Model electroweak radiative corrections in the $K\to \pi e^{+}\nu (\gamma )$ decay as a part of the combined theory effort to understand the existing anomaly in the determinations of $V_{us}$. Our new analysis features a chiral resummation of the large infrared-singular terms in the radiative corrections and a well-under-control strong interaction uncertainty based on the most recent lattice QCD inputs. While being consistent with the current state-of-the-art results obtained from chiral perturbation theory, we reduce the existing theory uncertainty from $10^{-3}$ to $10^{-4}$. Our result suggests that the Standard Model electroweak effects cannot account for the $V_{us}$ anomaly.

   ↳ hep-phhep-exhep-latnucl-ex+1PLB(2021)·35 citations
5. 05*

   The PRad Windowless Gas Flow Target

   J. Pierce🇺🇸 · J. Brock🇺🇸 · C. Carlin🇺🇸 · C. Keith🇺🇸 · J. Maxwell🇺🇸 · D. Meekins🇺🇸 · X. Bai🇺🇸 · A. Deur🇺🇸 · D. Dutta🇺🇸 · H. Gao🇺🇸 · A. Gasparian🇺🇸 · K. Gnanvo🇺🇸 and 12 other authors

   We report on a windowless, high-density, gas flow target at Jefferson Lab that was used to measure $r_p$, the root-mean-square charge radius of the proton. To our knowledge, this is the first such system used in a fixed-target experiment at a (non-storage ring) electron accelerator. The target achieved its design goal of an areal density of 2$\times$10${}^{18}$ atoms/cm${}^2$, with the gas uniformly distributed over the 4 cm length of the cell and less than 1% residual gas outside the cell. This design eliminated scattering from the end caps of the target cell, a problem endemic to previous measurements of the proton charge radius in electron scattering experiments, and permitted a precise, model-independent extraction of $r_p$ by reaching unprecedentedly low values of $Q^2$, the square of the electron's transfer of four-momentum to the proton.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2021)·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.