We use the world data on the pion form factor for space-like kinematics and a technique previously used to extract the proton transverse densities, to extract the transverse pion charge density and its uncertainty due the incomplete knowledge of the pion form factor at large values of Q 2 and the experimental uncertainties. The pion charge density at small values of impact parameter b < 0.1 fm is dominated by this incompleteness error while the range between 0.1-0.3 fm is relatively well constrained. A comparison of pion and proton transverse charge densities shows that the pion is denser than the proton for values of b < 0.2 fm. The pion and proton transverse charge densities seem to be the same for values of b=0.3-0.6 fm. Future data from JLab 12 GeV and the EIC will increase the dynamic extent of the form factor data to higher values of Q 2 and thus reduce the uncertainties in the extracted pion transverse charge density.

The 1 H(e, e ′ K + )Λ reaction was studied as a function of the Mandelstam variable −t using data from the E01-004 (FPI-2) and E93-018 experiments that were carried out in Hall C at the 6 GeV Jefferson Lab. The cross section was fully separated into longitudinal and transverse components, and two interference terms at four-momentum transfers Q 2 of 1.00, 1.36 and 2.07 GeV 2 . The kaon form factor was extracted from the longitudinal cross section using the Regge model by Vanderhaeghen, Guidal, and Laget. The results establish the method, previously used successfully for pion analyses, for extracting the kaon form factor. Data from 12 GeV Jefferson Lab experiments are expected to have sufficient precision to distinguish between theoretical predictions, for example recent perturbative QCD calculations with modern parton distribution amplitudes. The leadingtwist behavior for light mesons is predicted to set in for values of Q 2 between 5-10 GeV 2 , which makes data in the few GeV regime particularly interesting. The Q 2 dependence at fixed x and −t of the longitudinal cross section we extracted seems consistent with the QCD factorization prediction within the experimental uncertainty.The description of hadrons in terms of their constituents, the quarks and gluons, is a fundamental challenge in nuclear physics. Properties such as total charge and magnetic moments are well described in a constituent quark framework. However, charge and current distributions, which are more sensitive to the underlying dynamic processes in hadrons, are still not well described. The 1 H(e, e ′ K + )Λ reaction provides the simplest system including strangeness, and is thus an effective experimental test of flavor degrees of freedom.The electromagnetic form factors of hadrons are di-rectly connected to their internal structure. Measurements of the onset of the asymptotic, pointlike regime are an essential experimental verification of a key prediction of Quantum Chromodynamics (QCD) [1]. The form factors of light, two-quark hadronic systems like pions and kaons are of special importance as their asymptotic behavior is expected to set in earlier than that of threequark systems. The relevance of pion and kaon form factors, for both experiment and theory, is evident in the literature [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. A comprehensive review can be found in Ref. [19].

This paper discusses the quality and performance of currently available PbWO4 crystals of relevance to high-resolution electromagnetic calorimetry, e.g. detectors for the Neutral Particle Spectrometer at Jefferson Lab or those planned for the Electron-Ion Collider. Since the construction of the Compact Muon Solenoid (CMS) at the Large Hadron Collider (LHC) and early PANDA (The antiProton ANnihilations at DArmstadt) electromagnetic calorimeter (ECAL) the worldwide availability of high quality PbWO4 production has changed dramatically. We report on our studies of crystal samples from SICCAS/China and CRYTUR/Czech Republic that were produced between 2014 and 2019.

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