95 research outputs found
High-energy hadron physics at future facilities
We outline several directions for future investigations of the
three-dimensional structure of nucleon, including multiparton correlations,
color transparency, and branching processes at hadron colliders and at hadron
factories. We also find evidence that pQCD regime for non-vacuum Regge
trajectories sets in for leading to nearly t-independent
trajectories.Comment: 8 pages, 1 figure, Invited talk at INPC07, Tokyo, June 3-8, 200
Measurement of nuclear transparency from A(e,e'[pi]âș) reactions
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.In title on t.p., "[pi]" appears as the lower-case Greek letter.Includes bibliographical references (p. 161-165).The color transparency phenomenon refers to the suppression of final-state interactions of a hadron propagating through the nuclear medium at large momentum transfer when the hadron is produced with small transverse size. The pion electroproduction cross section from 1H, 2H,12C, 63Cu and 197Au targets from Q2 = 1.1 to 4.8 (GeV/c)2 was measured in Jefferson Laboratory Experiment E01-107. The nuclear transparency was formed by the ratio of ([sigma]A/[sigma]H) from the data and ([sigma]A/[sigma]H) from a model of electroproduction from nuclei that does not include [pi]-N final state interactions. A signature of color transparency is the enhancement of the nuclear transparency at large Q2 compared with predictions based on Glauber multiple scattering theory. This experiment represents the first nuclear transparency data from (e,e'[pi]+) reactions.by Benjamin Michael Patrick Clasie.Ph.D
A laser-driven target of high-density nuclear polarized hydrogen gas
We report the best figure-of-merit achieved for an internal nuclear polarized
hydrogen gas target and a Monte Carlo simulation of spin-exchange optical
pumping. The dimensions of the apparatus were optimized using the simulation
and the experimental results were in good agreement with the simulation. The
best result achieved for this target was 50.5% polarization with 58.2% degree
of dissociation of the sample beam exiting the storage cell at a hydrogen flow
rate of atoms/s.Comment: Accepted as a Rapid Communication article in Phys. Rev.
Monte Carlo study of the potential reduction in out-of-field dose using a patient-specific aperture in pencil beam scanning proton therapy
This study is aimed at identifying the potential benefits of using a patientspecific aperture in proton beam scanning. For this purpose, an accurate Monte Carlo model of the pencil beam scanning (PBS) proton therapy (PT) treatment head at Massachusetts General Hospital (MGH) was developed based on an existing model of the passive double-scattering (DS) system. The Monte Carlo code specifies the treatment head at MGH with sub-millimeter accuracy. The code was configured based on the results of experimental measurements performed at MGH. This model was then used to compare out-of-field doses in simulated DS treatments and PBS treatments. For the conditions explored, the penumbra in PBS is wider than in DS, leading to higher absorbed doses and equivalent doses adjacent to the primary field edge. For lateral distances greater than 10 cm from the field edge, the doses in PBS appear to be lower than those observed for DS. We found that placing a patient-specific aperture at nozzle exit during PBS treatments can potentially reduce doses lateral to the primary radiation field by over an order of magnitude. In conclusion, using a patient-specific aperture has the potential to further improve the normal tissue sparing capabilities of PBS
Hadrons in Nuclei -- from High (200 GeV) to Low (1 GeV) energies
The study of the interaction of hadrons, produced by elementary probes in a
nucleus, with the surrounding nuclear medium can give insight into two
important questions. First, at high energies, the production process, the
time-scales connected with it and the prehadronic interactions can be studied
by using the nuclear radius as a length-scale. We do this here by analyzing
data from the EMC and HERMES experiements on nuclear attenuation. Second, at
low energies the spectral function, and thus the selfenergy of the produced
hadron, can be studied. Specifically, we analyze the CBELSA/TAPS data on
production in nuclei and discuss the importance of understanding
in-medium effects both on the primary production cross section and the final
state branching ratio. In both of these studies an excellent control of the
final state interactions is essential.Comment: Lecture given by U. Mosel at International School of Nuclear Physics:
29th Course: Quarks in Hadrons and Nuclei, Erice, Sicily, Italy, 16-24 Sep
200
The Charge Form Factor of the Neutron at Low Momentum Transfer from the Reaction
We report new measurements of the neutron charge form factor at low momentum
transfer using quasielastic electrodisintegration of the deuteron.
Longitudinally polarized electrons at an energy of 850 MeV were scattered from
an isotopically pure, highly polarized deuterium gas target. The scattered
electrons and coincident neutrons were measured by the Bates Large Acceptance
Spectrometer Toroid (BLAST) detector. The neutron form factor ratio
was extracted from the beam-target vector asymmetry
at four-momentum transfers , 0.20, 0.29 and 0.42
(GeV/c).Comment: 5 pages, 3 figures, submitted to Phys. Rev. Let
Parity-violating Electron Deuteron Scattering and the Proton's Neutral Weak Axial Vector Form Factor
We report on a new measurement of the parity-violating asymmetry in
quasielastic electron scattering from the deuteron at backward angles at Q2=
0.038 (GeV/c)2. This quantity provides a determination of the neutral weak
axial vector form factor of the nucleon, which can potentially receive large
electroweak corrections. The measured asymmetry A=-3.51 +/- 0.57(stat) +/-
0.58(sys)ppm is consistent with theoretical predictions. We also report on
updated results of the previous experiment at Q2=0.091 (GeV/c)2, which are also
consistent with theoretical predictions.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let
Parity-violating Electron Deuteron Scattering and the Proton's Neutral Weak Axial Vector Form Factor
We report on a new measurement of the parity-violating asymmetry in
quasielastic electron scattering from the deuteron at backward angles at Q2=
0.038 (GeV/c)2. This quantity provides a determination of the neutral weak
axial vector form factor of the nucleon, which can potentially receive large
electroweak corrections. The measured asymmetry A=-3.51 +/- 0.57(stat) +/-
0.58(sys)ppm is consistent with theoretical predictions. We also report on
updated results of the previous experiment at Q2=0.091 (GeV/c)2, which are also
consistent with theoretical predictions.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let
Measurement of the proton electric to magnetic form factor ratio from \vec ^1H(\vec e, e'p)
We report the first precision measurement of the proton electric to magnetic
form factor ratio from spin-dependent elastic scattering of longitudinally
polarized electrons from a polarized hydrogen internal gas target. The
measurement was performed at the MIT-Bates South Hall Ring over a range of
four-momentum transfer squared from 0.15 to 0.65 (GeV/c).
Significantly improved results on the proton electric and magnetic form factors
are obtained in combination with previous cross-section data on elastic
electron-proton scattering in the same region.Comment: 4 pages, 2 figures, submitted to PR
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