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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.

We report on the highest precision yet achieved in the measurement of the polarization of a low-energy, O(1GeV) , continuous-wave (CW) electron beam, accomplished using a new polarimeter based on electron-photon scattering, in Hall C at Jefferson Lab. A number of technical innovations were necessary, including a novel method for precise control of the laser polarization in a cavity and a novel diamond microstrip detector that was able to capture most of the spectrum of scattered electrons. The data analysis technique exploited track finding, the high granularity of the detector, and its large acceptance. The polarization of the 180−μA , 1.16-GeV electron beam was measured with a statistical precision of <1% per hour and a systematic uncertainty of 0.59%. This exceeds the level of precision required by the Qweak experiment, a measurement of the weak vector charge of the proton. Proposed future low-energy experiments require polarization uncertainty <0.4% , and this result represents an important demonstration of that possibility. This measurement is the first use of diamond detectors for particle tracking in an experiment. It demonstrates the stable operation of a diamond-based tracking detector in a high radiation environment, for two years.

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 surface tensions of melts in the system CaO-FeO-SiO2 have been measured in the temperature range 1573 to 1708 K using the hollow cylinder technique. The iron oxide content was maintained constant at 30 wt pct and the CaO/SiO2 wt pct ratio was varied in the range 0.43 to 1.5. Surface tension increases with increasing basicity and with decreasing temperature. The data were used to test published correlations of slag foaming indexes with surface tension and viscosity. Foam life increases with increasing viscosity and with decreasing surface tension.

Argues that answering questions seeking information on when certain major life events occurred, as well as information about the frequency of certain mundane habits like TV viewing, is more difficult than it may initially seem. Types of errors that respondents (Rs) typically make are discussed, highlighting the error of temporal displacement, also known as \"telescoping.\" Interview data were gathered in 1992 from 2,109 British Rs asked to recall two landmark news events, the resignation of Margaret Thatcher & the Hillsborough football disaster. Only a small % of Rs were correct to within a month about the events, with Thatcher's resignation being forward telescoped most frequently, & the Hillsborough disaster being backward telescoped. Correlations between different demographic characteristics & the type of telescoping observed are reported. It is argued that people's temporal estimations are complex, & the likelihood of telescoping errors should be taken into account by those examining surveys. 3 Tables, 21 References. D. Weibel

The Qweak experiment, which took data at Jefferson Lab in the period 2010 - 2012, will precisely determine the weak charge of the proton by measuring the parity-violating asymmetry in elastic e-p scattering at 1.1 GeV using a longitudinally polarized electron beam and a liquid hydrogen target at a low momentum transfer of Q2 = 0.025 (GeV/c)2. The weak charge of the proton is predicted by the Standard Model and any significant deviation would indicate physics beyond the Standard Model. The technical challenges and experimental apparatus for measuring the weak charge of the proton will be discussed, as well as the method of extracting the weak charge of the proton. The results from a small subset of the data, that has been published, will also be presented. Furthermore an update will be given of the current status of the data analysis.

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.

The proton is one of the main building blocks of all visible matter in the universe. Among its intrinsic properties are its electric charge, mass, and spin. These emerge from the complex dynamics of its fundamental constituents, quarks and gluons, described by the theory of quantum chromodynamics (QCD). Using electron scattering its electric charge and spin, shared among the quark constituents, have been the topic of active investigation until today. An example is the novel precision measurement of the proton's electric charge radius. In contrast, little is known about the proton's inner mass density, dominated by the energy carried by the gluons, which are hard to access through electron scattering since gluons carry no electromagnetic charge. In the present work we chose to probe this gluonic gravitational density using a small color dipole, theJ/ψparticle, through its threshold photoproduction. From our data we determined, for the first time, the proton's gluonic gravitational form factors, which encode its mass density. We used a variety of methods and determined in all cases a mass radius that is notably smaller than the electric charge radius. In some cases, the determined radius is in excellent agreement with first-principle predictions from lattice QCD. This work paves the way for a deeper understanding of the salient role of gluons in providing gravitational mass to visible matter.

Here, 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.

Deep exclusive meson production (DEMP) reactions, such as \\(p(e,e'^+)n\\), provide opportunities to study the three-dimensional structure of the nucleon through differential cross section and beam- and target-spin asymmetry measurements. This work aims to probe the onset of the hard/soft factorization regime through the exclusive \\(p(e,e'^+)n\\) reaction, as measured in the KaonLT experiment at Jefferson Lab Hall C. A 10.6 GeV longitudinally polarized electron beam was incident on an unpolarized liquid hydrogen target, and the scattered electron and produced meson were detected in two magnetic focusing spectrometers, enabling precision cross section measurements. The cross section ratio \\(_LT'/_0\\) was extracted from the beam-spin asymmetry \\(A_LU\\). The \\(t\\)-dependence of \\(_LT'/_0\\) was determined at fixed \\(Q^2\\) and \\(x_B\\) over a range of kinematics from \\(22\\) GeV). Furthermore, these data are combined with recent results from CLAS/CLAS12 to determine the \\(Q^2\\)-dependence of \\(_LT'/_0\\) at two (\\(x_B\\), \\(t\\)) settings. This was fairly flat, with \\(Q^2\\) not having a measurable effect on the value of \\(_LT'/_0\\) in the range explored. Results are compared to predictions from the generalized parton distribution (GPD) formalism, which relies explicitly on hard/soft factorization, and Regge formalism. The Regge models better predict \\(_LT'/_0\\), which suggests that the factorization regime is not yet reached.