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1. Spectroscopy of A=9 hyperlithium by the (e,e′K+) reaction

   https://doi.org/https://doi.org/10.1103/PhysRevC.103.L041301  

   T. Gogami, C. Chen (April 2021, Physical review)

   null (Ed.)

   Missing mass spectroscopy with the (e,e′K+) reaction was performed at Jefferson Laboratory's Hall C for the neutron rich Λ hypernucleus 9ΛLi. The ground state energy was obtained to be Bg.s.Λ=8.84±0.17stat.±0.15sys. MeV by using shell model calculations of a cross section ratio and an energy separation of the spin doublet states (3/2+1 and 5/2+1). In addition, peaks that are considered to be states of [8Li(3+)⊗sΛ=3/2+2,1/2+] and [8Li(1+)⊗sΛ=5/2+2,7/2+] were observed at EΛ(no. 2)=1.74±0.27stat.±0.11sys. MeV and EΛ(no. 3)=3.30±0.24stat.±0.11sys. MeV, respectively. The EΛ(no. 3) is larger than shell model predictions by a few hundred keV, and the difference would indicate that a 5He+t structure is more developed for the 3+ state than those for the 2+ and 1+ states in a core nucleus 8Li as a cluster model calculation suggests. 

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2. Power expansion for heavy quarkonium production at next-to-leading order in e+e− annihilation

   https://doi.org/10.1007/JHEP09(2020)046  

   Lee, Kyle; Sterman, George (September 2020, Journal of High Energy Physics)

   null (Ed.)

   A bstract We study heavy quarkonium production associated with gluons in e + e − annihilation as an illustration of the perturbative QCD (pQCD) factorization approach, which incorporates the first nonleading power in the energy of the produced heavy quark pair. We show how the renormalization of the four-quark operators that define the heavy quark pair fragmentation functions using dimensional regularization induces “evanescent” operators that are absent in four dimensions. We derive closed forms for short-distance coefficients for quark pair production to next-to-leading order ( $$ {\alpha}_s^2 $$ α s 2 ) in the relevant color singlet and octet channels. Using non-relativistic QCD (NRQCD) to calculate the heavy quark pair fragmentation functions up to v 4 in the velocity expansion, we derive analytical results for the differential energy fraction distribution of the heavy quarkonium. Calculations for $$ {}^3{S}_1^{\left[1\right]} $$ 3 S 1 1 and $$ {}^1{S}_0^{\left[8\right]} $$ 1 S 0 8 channels agree with analogous NRQCD analytical results available in the literature, while several color-octet calculations of energy fraction distributions are new. We show that the remaining corrections due to the heavy quark mass fall off rapidly in the energy of the produced state. To explore the importance of evolution at energies much larger than the mass of the heavy quark, we solve the renormalization group equation perturbatively to two-loop order for the $$ {}^1{S}_0^{\left[8\right]} $$ 1 S 0 8 case. 

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3. Searching for an Enhanced Signal of the Onset of Color Transparency in Baryons with D(e,e′p)n Scattering

   https://doi.org/10.3390/physics4040092  

   Li, Shujie; Yero, Carlos; West, Jennifer Rittenhouse; Bennett, Clare; Cosyn, Wim; Higinbotham, Douglas; Sargsian, Misak; Szumila-Vance, Holly (December 2022, Physics)

   Observation of the onset of color transparency in baryons would provide a new means of studying the nuclear strong force and would be the first clear evidence of baryons transforming into a color-neutral point-like size in the nucleus as predicted by quantum chromodynamics. Recent C(e,e′p) results from electron-scattering did not observe the onset of color transparency (CT) in protons up to spacelike four-momentum transfers squared, Q2=14.2 GeV2. The traditional methods of searching for CT in (e,e′p) scattering use heavy targets favoring kinematics with already initially reduced final state interactions (FSIs) such that any CT effect that further reduces FSIs will be small. The reasoning behind this choice is the difficulty in accounting for all FSIs. D(e,e′p)n, on the other hand, has well-understood FSI contributions from double scattering with a known dependence on the kinematics and can show an increased sensitivity to hadrons in point-like configurations. Double scattering is the square of the re-scattering amplitude in which the knocked-out nucleon interacts with the spectator nucleon, a process that is suppressed in the presence of point-like configurations and is particularly well-studied for the deuteron. This suppression yields a quadratic sensitivity to CT effects and is strongly dependent on the choice of kinematics. Here, we describe a possible Jefferson National Accelerator Facility (JLab) electron-scattering experiment that utilizes these kinematics and explores the potential signal for the onset of CT with enhanced sensitivity as compared to recent experiments. 

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4. Ruling out Color Transparency in Quasielastic 12C(e,e'p) up to Q2 of 14.2 (GeV/c)2

   Bhetuwal, D; Matter, J; Szumila-Vance, H; Kabir, M. L; Dutta, D; Ent, R; Abrams, D; Ahmed, Z; Aljawrneh, B; Alsalmi, S; et al (February 2021, Physical review letters)

   null (Ed.)

   Quasielastic C12(e,e′p) scattering was measured at spacelike 4-momentum transfer squared Q2=8, 9.4, 11.4, and 14.2  (GeV/c)2, the highest ever achieved to date. Nuclear transparency for this reaction was extracted by comparing the measured yield to that expected from a plane-wave impulse approximation calculation without any final state interactions. The measured transparency was consistent with no Q2 dependence, up to proton momenta of 8.5  GeV/c, ruling out the quantum chromodynamics effect of color transparency at the measured Q2 scales in exclusive (e,e′p) reactions. These results impose strict constraints on models of color transparency for protons. 

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5. The effect of solvent on determining highest occupied molecular orbital energies of semiconducting organic molecules: Insight from a combined computational approach

   https://doi.org/10.1002/jcc.27065  

   Kramer, Aaron; Pachter, Ruth; Hsu, Julia W. P.; Vandenberghe, William G. (January 2023, Journal of Computational Chemistry)

   Abstract Although cyclic voltammetry (CV) measurements in solution have been widely used to determine the highest occupied molecular orbital energy (E_HOMO) of semiconducting organic molecules, an understanding of the experimentally observed discrepancies due to the solvent used is lacking. To explain these differences, we investigate the solvent effects onE_HOMOby combining density functional theory and molecular dynamics calculations for four donor molecules with a common backbone moiety. We compare the experimentalE_HOMOvalues to the calculated values obtained from either implicit or first solvation shell theories. We find that the first solvation shell method can capture theE_HOMOvariation arising from the functional groups in solution, unlike the implicit method. We further applied the first solvation shell method to other semiconducting organic molecules measured in solutions for different solvents. We find that theE_HOMOobtained using an implicit method is insensitive to solvent choice. The first solvation shell, however, producesE_HOMOvalues that are sensitive to solvent choices and agrees with published experimental results. The solvent sensitivity arises from a hierarchy of three effects: (1) the solute electronic state within a surrounding dielectric continuum, (2) ambient temperature or solvent atoms changing the solute geometry, and (3) electronic interactions between the solute and solvents. The implicit method, on the other hand, only captures the effect of a dielectric environment. Our findings suggest thatE_HOMOobtained by CV measurements should account for the influence of solvent when the results are reported, interpreted, or compared to other molecules. 

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