The cross section of atomic electron Compton scattering γ+e→γ′+e′ was measured in the 4.400–5.475 GeV photon beam energy region by the PrimEx collaboration at Jefferson Lab with an accuracy of 2.6% ...and less. The results are consistent with theoretical predictions that include next-to-leading order radiative corrections. The measurements provide the first high precision test of this elementary QED process at beam energies greater than 0.1 GeV.
New Measurement of the {pi}{sup 0} Radiative Decay Width Larin, I.; North Carolina A and T State University, Greensboro, North Carolina 27411; McNulty, D. ...
Physical review letters,
04/2011, Letnik:
106, Številka:
16
Journal Article
Recenzirano
High precision measurements of the differential cross sections for {pi}{sup 0} photoproduction at forward angles for two nuclei, {sup 12}C and {sup 208}Pb, have been performed for incident photon ...energies of 4.9-5.5 GeV to extract the {pi}{sup 0}{yields}{gamma}{gamma} decay width. The experiment was done at Jefferson Lab using the Hall B photon tagger and a high-resolution multichannel calorimeter. The {pi}{sup 0}{yields}{gamma}{gamma} decay width was extracted by fitting the measured cross sections using recently updated theoretical models for the process. The resulting value for the decay width is {Gamma}({pi}{sup 0}{yields}{gamma}{gamma})=7.82{+-}0.14(stat){+-}0.17(syst) eV. With the 2.8% total uncertainty, this result is a factor of 2.5 more precise than the current Particle Data Group average of this fundamental quantity, and it is consistent with current theoretical predictions.
Tensor polarization observables ( t(20), t(21), and t(22)) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c)(2). The ...experiment was performed at the Jefferson Laboratory in Hall C using the electron High Momentum Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q2 the deuteron charge form factors G(C) and G(Q). They are in good agreement with relativistic calculations and disagree with perturbative QCD predictions.
High precision measurements of the differential cross sections for $\pi^0$ photoproduction at forward angles for two nuclei, $^{12}$C and $^{208}$Pb, have been performed for incident photon energies ...of 4.9 - 5.5 GeV to extract the ${\pi^0 \to \gamma\gamma}$ decay width. The experiment was done at Jefferson Lab using the Hall~B photon tagger and a high-resolution multichannel calorimeter. The ${\pi^0 \to \gamma\gamma}$ decay width was extracted by fitting the measured cross sections using recently updated theoretical models for the process. The resulting value for the decay width is $\Gamma{(\pi^0 \to \gamma\gamma)} = 7.82 \pm 0.14 ~({\rm stat.}) \pm 0.17 ~({\rm syst.}) ~{\rm eV}$. With the 2.8\% total uncertainty, this result is a factor of 2.5 more precise than the current PDG average of this fundamental quantity and it is consistent with current theoretical predictions.
A rigorous extraction of the deuteron charge form factors from tensor polarization data in elastic electron-deuteron scattering, at given values of the 4-momentum transfer, is presented. Then the ...world data for elastic electron-deuteron scattering is used to parameterize, in three different ways, the three electromagnetic form factors of the deuteron in the 4-momentum transfer range 0-7 fm^-1. This procedure is made possible with the advent of recent polarization measurements. The parameterizations allow a phenomenological characterization of the deuteron electromagnetic structure. They can be used to remove ambiguities in the form factors extraction from future polarization data.
Intrabeam scattering formulas for high energy beams Kubo, Kiyoshi; Mtingwa, Sekazi K.; Wolski, Andrzej
Physical review special topics. PRST-AB. Accelerators and beams,
08/2005, Letnik:
8, Številka:
8
Journal Article
Recenzirano
Odprti dostop
We derive completely integrated formulas for emittance growth times due to intrabeam scattering for charged particle beams in the high energy limit, including the effect of lattice parameters that ...vary around the accelerator ring. Using accelerator lattices for the prototype damping ring called the Accelerator Test Facility at KEK and those for two proposed International Linear Collider damping rings, we compare our results with other calculations.
The A(Q^2) structure function in elastic electron-deuteron scattering was measured at six momentum transfers Q^2 between 0.66 and 1.80 (GeV/c)^2 in Hall C at Jefferson Laboratory. The scattered ...electrons and recoil deuterons were detected in coincidence, at a fixed deuteron angle of 60.5 degrees. These new precise measurements resolve discrepancies between older sets of data. They put significant constraints on existing models of the deuteron electromagnetic structure, and on the strength of isoscalar meson exchange currents.
In our quest to understand the nature of dark matter and discover its non-gravitational interactions with ordinary matter, we propose an experiment using a \pbo ~calorimeter to search for or set new ...limits on the production rate of i) hidden sector particles in the \(3 - 60\) MeV mass range via their \(e^+e^-\) decay (or \(\gamma\gamma\) decay with limited tracking), and ii) the hypothetical X17 particle, claimed in multiple recent experiments. The search for these particles is motivated by new hidden sector models and dark matter candidates introduced to account for a variety of experimental and observational puzzles: the small-scale structure puzzle in cosmological simulations, anomalies such as the 4.2\(\sigma\) disagreement between experiments and the standard model prediction for the muon anomalous magnetic moment, and the excess of \(e^+e^-\) pairs from the \(^8\)Be M1 and \(^4\)He nuclear transitions to their ground states observed by the ATOMKI group. In these models, the \(1 - 100\) MeV mass range is particularly well-motivated and the lower part of this range still remains unexplored. Our proposed direct detection experiment will use a magnetic-spectrometer-free setup (the PRad apparatus) to detect all three final state particles in the visible decay of a hidden sector particle allowing for an effective control of the background and will cover the proposed mass range in a single setting. The use of the well-demonstrated PRad setup allows for an essentially ready-to-run and uniquely cost-effective search for hidden sector particles in the \(3 - 60\) MeV mass range with a sensitivity of 8.9\(\times\)10\(^{-8}\) - 5.8\(\times\)10\(^{-9}\) to \(\epsilon^2\), the square of the kinetic mixing interaction constant between hidden and visible sectors. This updated proposal includes our response to the PAC49 comments.
Kaon electroproduction from light nuclei and hydrogen, using 1H, 2H, 3He, 4He, and Carbon targets has been measured at Jefferson Laboratory. The quasifree angular distributions of Lambda and Sigma ...hyperons were determined at Q^2= 0.35(GeV/c)^2 and W= 1.91GeV. Electroproduction on hydrogen was measured at the same kinematics for reference.
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