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The proton is one of the main building blocks of all visible matter in the Universe 1 . Among its intrinsic properties are its electric charge, mass and spin 2 . These properties emerge from the complex dynamics of its fundamental constituents—quarks and gluons—described by the theory of quantum chromodynamics 3 – 5 . The electric charge and spin of protons, which are shared among the quarks, have been investigated previously using electron scattering 2 . An example is the highly precise measurement of the electric charge radius of the proton 6 . By contrast, little is known about the inner mass density of the proton, which is dominated by the energy carried by gluons. Gluons are hard to access using electron scattering because they do not carry an electromagnetic charge. Here we investigated the gravitational density of gluons using a small colour dipole, through the threshold photoproduction of the J / ψ particle. We determined the gluonic gravitational form factors of the proton 7 , 8  from our measurement. We used a variety of models 9 – 11 and determined, in all cases, a mass radius that is notably smaller than the electric charge radius. In some, but not all cases, depending on the model, the determined radius agrees well with first-principle predictions from lattice quantum chromodynamics 12 . This work paves the way for a deeper understanding of the salient role of gluons in providing gravitational mass to visible matter. The gluonic gravitational form factor of the proton was determined using various models, and these analyses showed that the mass radius of the proton was smaller than the electric charge radius.

The visible world is founded on the proton, the only composite building block of matter that is stable in nature. Consequently, understanding the formation of matter relies on explaining the dynamics and the properties of the proton’s bound state. A fundamental property of the proton involves the response of the system to an external electromagnetic field. It is characterized by the electromagnetic polarizabilities 1 that describe how easily the charge and magnetization distributions inside the system are distorted by the electromagnetic field. Moreover, the generalized polarizabilities 2 map out the resulting deformation of the densities in a proton subject to an electromagnetic field. They disclose essential information about the underlying system dynamics and provide a key for decoding the proton structure in terms of the theory of the strong interaction that binds its elementary quark and gluon constituents. Of particular interest is a puzzle in the electric generalized polarizability of the proton that remains unresolved for two decades 2 . Here we report measurements of the proton’s electromagnetic generalized polarizabilities at low four-momentum transfer squared. We show evidence of an anomaly to the behaviour of the proton’s electric generalized polarizability that contradicts the predictions of nuclear theory and derive its signature in the spatial distribution of the induced polarization in the proton. The reported measurements suggest the presence of a new, not-yet-understood dynamical mechanism in the proton and present notable challenges to the nuclear theory. Measurements of the proton’s electromagnetic structure show enhancement of its electric generalized polarizability compared with theoretical expectations, confirming the presence of a new dynamical mechanism not accounted for by current theories.

Study design: This was a cross-over efficacy study design. Objective: To determine spasticity differences between static and dynamic standing training in individuals with spinal cord injury (SCI). Setting: Vancouver, Canada. Methods: Ten individuals with SCI who could stand with or without bracing or supports participated in both dynamic and static standing training (one session each, 2 days apart) using a Segway. The primary outcome was spasticity as measured by Visual Analog Scale (VAS), Modified Ashworth Scale (MAS) and electromyography (EMG) of the quadriceps, hamstrings, adductors and gastrocnemius. Results: There was no statistically detectable difference in spasticity between dynamic and static standing training in individuals with SCI as measured by VAS, MAS or EMG, although there was a trend towards decreased spasticity after the dynamic training. Conclusion: There is no significant difference in spasticity outcomes between static and dynamic standing training on a Segway for individuals with SCI. Sponsorship: This research was funded by Natural Sciences and Engineering Research Council of Canada and International Collaboration on Repair Discoveries.

We report new pion electroproduction measurements in the Δ ( 1232 ) resonance, utilizing the SHMS - HMS magnetic spectrometers of Hall C at Jefferson Lab. The data focus on a region that exhibits a strong and rapidly changing interplay of the mesonic cloud and quark-gluon dynamics in the nucleon. The results are in reasonable agreement with models that employ pion cloud effects and chiral effective field theory calculations, but at the same time they suggest that an improvement is required to the theoretical calculations and provide valuable input that will allow their refinements. The data illustrate the potential of the magnetic spectrometers setup in Hall C towards the study the Δ ( 1232 ) resonance. These first reported results will be followed by a series of measurements in Hall C, that will expand the studies of the Δ ( 1232 ) resonance offering a high precision insight within a wide kinematic range from low to high momentum transfers.

Study design: Cross-sectional. Objectives: To determine the relationships between (1) wheeling parameters using the SmartWheel Clinical Protocol (SCP) and wheelchair skills (wheelchair skills test 4.1 (WST)) and (2) push effectiveness (m per push) and the WST, among individuals with spinal cord injury. Setting: Biomechanics Laboratory, Canada. Methods: Sixteen adults and eight children participated in this study. Multiple regression analyses were used to determine significant SCP predictors (that is, weight-normalised peak force, speed, push frequency and mechanical effectiveness) of WST score. To determine relationships between push effectiveness and WST scores, Pearson’s correlations were calculated. Results: SCP-TILE: speed and mechanical effectiveness explained 36% of the variance in the WST score. SCP-RAMP and SCP-CARPET: speed explained 58% and 37% of the variance in the WST score, respectively. Push effectiveness was significantly correlated with the WST score on all three surfaces (tile, ramp and carpet). Conclusion: Wheeling speed was a significant predictor of the WST score for all surfaces tested. Regression analyses demonstrated that SCP-RAMP had the strongest relationship with WST score. Therefore, when time is restricted, the SCP-RAMP may be the most predictive test and speed may be the most useful variable to evaluate. However, the authors do not believe that one single variable should ever replace a full assessment of skills.

Study design: A pilot prospective pre- and post-intervention study. Objectives: To determine whether a dynamic standing program using the Segway Personal Transporter results in any measurable physiological effects in individuals with spinal cord injury (SCI) using both qualitative and quantitative measures of spasticity, pain and fatigue. Setting: International Collaboration of Repair Discoveries (ICORD) Research Centre, Vancouver, BC, Canada. Methods: Eight individuals with SCI ASIA (American Spinal Injury Association) A–D, who could stand with or without the assistance of bracing or supports, participated in a 4-week dynamic standing program using a Segway (3 per week, 30-min sessions). The main outcome was spasticity as measured by the Modified Ashworth Scale (MAS). Secondary measures included the SCI-Spasticity Evaluation Tool, Pain Outcomes Questionnaire, and Fatigue Severity Scale. Results: The dynamic standing sessions were associated with immediate improvements in spasticity (MAS) ( P <0.001) and self-reported pain ( P <0.05). Fatigue levels decreased, however this was not significant. There is little evidence to suggest that these beneficial outcomes may have lasting effects. Conclusions: Dynamic standing on the Segway may be effective for short-term spasticity reduction and decreased pain and fatigue. Future work should examine a larger sample size and help to propose mechanisms for potential reductions in spasticity.

Missing-mass spectroscopy with the 3 H( e , e′K + ) reaction was carried out at Jefferson Lab’s (JLab) Hall A in Oct–Nov, 2018. The differential cross section for the 3 H( γ ∗ , K + )Λ nn was deduced at ω = Ee − E e′ = 2.102 GeV and at the forward K + -scattering angle (0 ° ≤ θ γ ∗ K ≤ 5 ° ) in the laboratory frame. Given typical predicted energies and decay widths, which are ( B Λ , Γ) = (−0.25, 0.8) and (−0.55, 4.7) MeV, the cross sections were found to be 11.2 ± 4.8(stat.) +4.1 −2.1 (sys.) and 18.1 ± 6.8(stat.) +4.2 −2.9 (sys.) nb/sr, respectively. The obtained result would impose a constraint for interaction models particularly between Λ and neutron by comparing to theoretical calculations.

An nnΛ is a neutral baryon system with no charge. The study of the pure Λ-neutron system such as nnΛ gives us information on the Λn interaction. The nnΛ search experiment (E12-17-003) was performed at JLab Hall A in 2018. In this article, the Λn FSI was investigated by a shape analysis of the 3H(e, e′K+)X missing mass spectrum, and a preliminary result for the Λn FSI study is given.

JLab E12-19-002 Experiment is planned to measure the Λ-binding energies of 3 Λ H [ J π = 1/2 + or 3/2 + ( T = 0)] and 4 Λ H (1 + ) at JLab Hall C. The expected accuracy for the binding-energy measurement is |Δ B total Λ | ≃ 70 keV. The accurate spectroscopy for these light hypernuclei would shed light on the puzzle of the small binding energy and short lifetime of 3 Λ H, and the chargesymmetry breaking in the ΛN interaction. We aim to perform the experiment in 2025.

We performed an experiment using tritium and hydrogen cryogenic gas targets at Thomas Jefferson National Accelerator Facility (JLab) in 2018 (E12-17-003)[1, 2]. In this article, we discuss the Λ/Σ0 hyperon electroproduction from hydrogen target. Elementary Λ/Σ0 hyperon production processes are important not only for an absolute mass scale calibration in our experiment, but also for the study of the electroproduction mechanisms themselves. In this article, we reported the results of the differential cross section for the p(e, e’K+)Λ/Σ0 reaction at Q2 ∼ 0.5 (GeV/c)2.