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Background. Young people and athletes willing to gain muscle mass and strength are likely to consume whey protein supplements. The effect of milk as a dietary source of whey protein on acne is still controversial. At the same time, a few studies have suggested an acnegenic impact of whey protein supplements. Objectives. To examine the association of whey protein supplements on acne risk among male adolescents and young adults. Materials and Methods. 201 male teenagers and young adults attending fitness centers in Irbid/Jordan were involved in an observational case-control research; those with acne were deemed cases, and those without acne were considered controls. The primary outcome was a comparison of the proportion of participants in each group who consumed whey protein supplements within the previous three months. Results. 100 acne-afflicted participants were compared to 101 healthy controls with similar demographics, including age, body mass index, educational level, and smoking habits, as well as intake of vitamin B12, corticosteroids, and anabolic steroids. However, considerably more participants in the acne group (47%) were taking whey protein supplements than in the control group (27.7%) (p=0.0047). The significance of this difference was maintained after multivariate analysis. Conclusion. This case-control study provides evidence of a positive association between whey protein consumption and acne risk.

[...]CEBAF today, and with an energy upgrade, will continue to operate with several orders of magnitude higher luminosity than what is planned at the Electron-Ion Collider (EIC). Photoproduction cross sections of exotic states could be decisive in understanding the nature of a subset of the pentaquark and tetraquark candidates that contain charm and anti-charm quarks. [...]in Hall B the high-intensity flux of quasi-real photons at high energy will add the extra capability of studying the Q2 evolution of any new state produced. JLab will be able to explore the proton’s gluonic structure by unique precise measurements of the photo and electroproduction cross section near threshold of J/ψ and higher-mass charmonium states, χc and ψ(2S) . [...]with an increase of the polarization figure-of-merit by an order of magnitude, GlueX will be able to measure polarization observables that are critical to disentangle the reaction mechanism and draw conclusions about the mass properties of the proton. [...]JLab has a uniquely fundamental role to play in the EIC era in the realm of precision separation measurements between the longitudinal ( σL ) and transverse ( σT ) photon contributions to the cross section, which are critical for studies of both semi-inclusive and exclusive processes.

The internal structure of nucleons (protons and neutrons) remains one of the greatest outstanding problems in modern nuclear physics. By scattering high-energy electrons off a proton we are able to resolve its fundamental constituents and probe their momenta and positions. Here we investigate the dynamics of quarks and gluons inside nucleons using deeply virtual Compton scattering (DVCS)—a highly virtual photon scatters off the proton, which subsequently radiates a photon. DVCS interferes with the Bethe-Heitler (BH) process, where the photon is emitted by the electron rather than the proton. We report herein the full determination of the BH-DVCS interference by exploiting the distinct energy dependences of the DVCS and BH amplitudes. In the regime where the scattering is expected to occur off a single quark, measurements show an intriguing sensitivity to gluons, the carriers of the strong interaction. It remains a challenge to find the structure and the distribution of the constituents of nucleons. Here the authors use a scattering method to get information about the gluons and quarks inside a proton and separate the contribution of Bethe-Heitler from the deeply virtual Compton scattering process.

The three-dimensional structure of nucleons (protons and neutrons) is embedded in so-called generalized parton distributions, which are accessible from deeply virtual Compton scattering. In this process, a high-energy electron is scattered off a nucleon by exchanging a virtual photon. Then, a highly energetic real photon is emitted from one of the quarks inside the nucleon, which carries information on the quark’s transverse position and longitudinal momentum. By measuring the cross-section of deeply virtual Compton scattering, Compton form factors related to the generalized parton distributions can be extracted. Here, we report the observation of unpolarized deeply virtual Compton scattering off a deuterium target. From the measured photon-electroproduction cross-sections, we have extracted the cross-section of a quasifree neutron and a coherent deuteron. Due to the approximate isospin symmetry of quantum chromodynamics, we can determine the contributions from the different quark flavours to the helicity-conserved Compton form factors by combining our measurements with previous ones probing the proton’s internal structure. These results advance our understanding of the description of the nucleon structure, which is important to solve the proton spin puzzle. The internal structure of the neutron has now been probed by highly energetic photons scattering off it. Combined with previous results for protons, these measurements reveal the contributions of quark flavours to the nucleon structure.

This document presents the initial scientific case for upgrading the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab) to 22 GeV. It is the result of a community effort, incorporating insights from a series of workshops conducted between March 2022 and April 2023. With a track record of over 25 years in delivering the world's most intense and precise multi-GeV electron beams, CEBAF's potential for a higher energy upgrade presents a unique opportunity for an innovative nuclear physics program, which seamlessly integrates a rich historical background with a promising future. The proposed physics program encompass a diverse range of investigations centered around the nonperturbative dynamics inherent in hadron structure and the exploration of strongly interacting systems. It builds upon the exceptional capabilities of CEBAF in high-luminosity operations, the availability of existing or planned Hall equipment, and recent advancements in accelerator technology. The proposed program cover various scientific topics, including Hadron Spectroscopy, Partonic Structure and Spin, Hadronization and Transverse Momentum, Spatial Structure, Mechanical Properties, Form Factors and Emergent Hadron Mass, Hadron-Quark Transition, and Nuclear Dynamics at Extreme Conditions, as well as QCD Confinement and Fundamental Symmetries. Each topic highlights the key measurements achievable at a 22 GeV CEBAF accelerator. Furthermore, this document outlines the significant physics outcomes and unique aspects of these programs that distinguish them from other existing or planned facilities. In conclusion, this document provides an exciting rationale for the energy upgrade of CEBAF to 22 GeV, outlining the transformative scientific potential that lies within reach, and the remarkable opportunities it offers for advancing our understanding of hadron physics and related fundamental phenomena.

Here, the purpose of this document is to outline the developing scientific case for pursuing an energy upgrade to 22 GeV of the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Accelerator Facility (TJNAF, or JLab). This document was developed with input from a series of workshops held in the period between March 2022 and April 2023 that were organized by the JLab user community and staff with guidance from JLab management (see Sec. 10). The scientific case for the 22 GeV energy upgrade leverages existing or already planned Hall equipment and world-wide uniqueness of CEBAF high-luminosity operations.

We report a precise measurement of the parity-violating asymmetry \\(A_{\\rm PV}\\) in the elastic scattering of longitudinally polarized electrons from \\(^{48}{\\rm Ca}\\). We measure \\(A_{\\rm PV} =2668\\pm 106\\ {\\rm (stat)}\\pm 40\\ {\\rm (syst)}\\) parts per billion, leading to an extraction of the neutral weak form factor \\(F_{\\rm W} (q=0.8733\\) fm\\(^{-1}) = 0.1304 \\pm 0.0052 \\ {\\rm (stat)}\\pm 0.0020\\ {\\rm (syst)}\\) and the charge minus the weak form factor \\(F_{\\rm ch} - F_{\\rm W} = 0.0277\\pm 0.0055\\). The resulting neutron skin thickness \\(R_n-R_p=0.121 \\pm 0.026\\ {\\rm (exp)} \\pm 0.024\\ {\\rm (model)}\\)~fm is relatively thin yet consistent with many model calculations. The combined CREX and PREX results will have implications for future energy density functional calculations and on the density dependence of the symmetry energy of nuclear matter.

We report a precision measurement of the parity-violating asymmetry \\(A_{PV}\\) in the elastic scattering of longitudinally polarized electrons from \\(^{208}\\)Pb. We measure \\(A_{PV}=550\\pm 16 {\\rm (stat)}\\pm 8\\ {\\rm (syst)}\\) parts per billion, leading to an extraction of the neutral weak form factor \\(F_W(Q^2 = 0.00616\\ {\\rm GeV}^2) = 0.368 \\pm 0.013\\). Combined with our previous measurement, the extracted neutron skin thickness is \\(R_n-R_p=0.283 \\pm 0.071\\)~fm. The result also yields the first significant direct measurement of the interior weak density of \\(^{208}\\)Pb: \\(\\rho^0_W = -0.0796\\pm0.0036\\ {\\rm (exp.)}\\pm0.0013\\ {\\rm (theo.)}\\ {\\rm fm}^{-3}\\) leading to the interior baryon density \\(\\rho^0_b = 0.1480\\pm0.0036\\ {\\rm (exp.)}\\pm0.0013\\ {\\rm (theo.)}\\ {\\rm fm}^{-3}\\). The measurement accurately constrains the density dependence of the symmetry energy of nuclear matter near saturation density, with implications for the size and composition of neutron stars.

We report the first longitudinal/transverse separation of the deeply virtual exclusive \\(\\pi^0\\) electroproduction cross section off the neutron and coherent deuteron. The corresponding four structure functions \\(d\\sigma_L/dt\\), \\(d\\sigma_T/dt\\), \\(d\\sigma_{LT}/dt\\) and \\(d\\sigma_{TT}/dt\\) are extracted as a function of the momentum transfer to the recoil system at \\(Q^2\\)=1.75 GeV\\(^2\\) and \\(x_B\\)=0.36. The \\(ed \\to ed\\pi^0\\) cross sections are found compatible with the small values expected from theoretical models. The \\(en \\to en\\pi^0\\) cross sections show a dominance from the response to transversely polarized photons, and are in good agreement with calculations based on the transversity GPDs of the nucleon. By combining these results with previous measurements of \\(\\pi^0\\) electroproduction off the proton, we present a flavor decomposition of the \\(u\\) and \\(d\\) quark contributions to the cross section.

We present deeply virtual \\(\\pi^0\\) electroproduction cross-section measurements at \\(x_B\\)=0.36 and three different \\(Q^2\\)--values ranging from 1.5 to 2 GeV\\(^2\\), obtained from experiment E07-007 that ran in the Hall A at Jefferson Lab. The Rosenbluth technique was used to separate the longitudinal and transverse responses. Results demonstrate that the cross section is dominated by its transverse component, and thus is far from the asymptotic limit predicted by perturbative Quantum Chromodynamics. An indication of a non-zero longitudinal contribution is provided by the interference term \\(\\sigma_{LT}\\) also measured. Results are compared with several models based on the leading twist approach of Generalized Parton Distributions (GPDs). In particular, a fair agreement is obtained with models where the scattering amplitude is described by a convolution of chiral-odd (transversity) GPDs of the nucleon with the twist-3 pion distribution amplitude. Therefore, neutral pion electroproduction may offer the exciting possibility of accessing transversity GPDs through experiment.