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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016., Cataloged from PDF version of thesis., Includes bibliographical references (pages 265-273)., OLYMPUS is a particle physics experiment that collected data in 2012 at DESY, in Hamburg, Germany, on the asymmetry between positron-proton and electron-proton elastic scattering cross sections. A non-zero asymmetry is evidence of hard two-photon exchange, which has been hypothesized to cause the discrepancy in measurements of the proton's electromagnetic form factors. Alternating electron and positron beams, accelerated to 2 GeV, were directed through a windowless, gaseous, hydrogen target, and the scattered lepton and recoiling proton were detected in coincidence using a large acceptance magnetic spectrometer. Determining the relative integrated luminosity between the electron and positron data sets was critical, and a new technique, involving multi-interaction events, was developed to achieve the desired sub-percent accuracy. A detailed Monte Carlo simulation was built in order to reproduce the convolution of systematic effects at every stage of the experiment. The first stage in the simulation was new radiative event generator, which permitted the full simulation of the non-trivial radiative corrections to the measurement. The analysis of the data and simulation showed that the lepton sign asymmetry rises by several percent between a momentum transfer of 0.5 GeV2 /c2 and 2.25 GeV2 /c2 . This rise as a function of increasing momentum transfer confirms that two photon exchange at least partially contributes to the proton form factor discrepancy., by Axel Schmidt., Ph. D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016., Cataloged from PDF version of thesis., Includes bibliographical references (pages 275-288)., Measurements of the ratio of the proton elastic form factors ([mu]pGe/Gm) using Rosenbluth separation and those using polarization-based techniques show a strong discrepancy, which has persisted both in modern experimental results and in re-analyses of previous data. The most widely accepted hypothesis to explain this discrepancy is the treatment of the contributions from hard two-photon exchange (TPE) to elastic electron-proton scattering in the radiative corrections applied to the Rosenbluth separation measurements. Calculations of the hard TPE contribution are highly model dependent, but the effect may be measured experimentally with a precise determination of the ratio of the positron-proton and electron-proton elastic scattering cross sections. The OLYMPUS experiment collected approximately 4 fb-1 of e+p and e-p scattering data at the DORIS storage ring at DESY in 2012, with the goal of measuring the elastic [sigma]e+p/[sigma]e-p ratio over the kinematic range (0.4 < c < 0.9), (0.6 < Q2 < 2.2) GeV2 /c 2 at a fixed lepton beam energy of 2.01 GeV. The detector for the OLYMPUS experiment consisted of refurbished elements of the Bates Large Acceptance Spectrometer Toroid (BLAST) surrounding an internal gaseous hydrogen target, with the addition of multiple systems for the monitoring of the luminosity collected by the experiment. A detailed simulation of the experiment was developed to account for both radiative corrections and various systematic effects. This work presents preliminary results from the OLYMPUS data, demonstrating that the elastic [sigma]e+p/[sigma]e-p ratio rises to several percent at [epsilon] ~~ 0.4 and indicating a significant contribution from TPE to e± p scattering. Additionally, the value of [sigma]e+p/[sigma]e-p has been measured to unprecedented precision at [epsilon] = 0.98, which provides a valuable normalization point for other experimental data., by Brian Scott Henderson., Ph. D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016., Cataloged from PDF version of thesis., Includes bibliographical references (pages 265-273)., OLYMPUS is a particle physics experiment that collected data in 2012 at DESY, in Hamburg, Germany, on the asymmetry between positron-proton and electron-proton elastic scattering cross sections. A non-zero asymmetry is evidence of hard two-photon exchange, which has been hypothesized to cause the discrepancy in measurements of the proton's electromagnetic form factors. Alternating electron and positron beams, accelerated to 2 GeV, were directed through a windowless, gaseous, hydrogen target, and the scattered lepton and recoiling proton were detected in coincidence using a large acceptance magnetic spectrometer. Determining the relative integrated luminosity between the electron and positron data sets was critical, and a new technique, involving multi-interaction events, was developed to achieve the desired sub-percent accuracy. A detailed Monte Carlo simulation was built in order to reproduce the convolution of systematic effects at every stage of the experiment. The first stage in the simulation was new radiative event generator, which permitted the full simulation of the non-trivial radiative corrections to the measurement. The analysis of the data and simulation showed that the lepton sign asymmetry rises by several percent between a momentum transfer of 0.5 GeV2 /c2 and 2.25 GeV2 /c2 . This rise as a function of increasing momentum transfer confirms that two photon exchange at least partially contributes to the proton form factor discrepancy., by Axel Schmidt., Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009., In title on title page, "the square root of sigma" appears as the mathematical symbol, and "sigma" appears as the lower-case Greek letter. Cataloged from PDF version of thesis., Includes bibliographical references (p. 123-126)., Twenty years of polarized lepton-nucleon scattering experiments have found that the contribution from quark spins (1/2[delta] [sigma]) to the spin of the proton is only ~ 35%. This has lead researchers to look elsewhere, specifically to gluon spin ([delta sigma]) for a large contribution to proton spin. [delta sigma] has been only loosely constrained in polarized DIS and SIDIS experiments. Polarized proton-proton collisions at RHIC provide sensitivity to [delta sigma] through measurements of the longitudinal double-spin asymmetry, ALL. This work presents a measurement of ALL for inclusive 7ro production in polarized proton-proton collisions using the STAR detector and data from RHIC Run 6. 7r0s are abundantly produced at mid-rapidity in proton-proton collisions, making them natural candidates for studies of [delta] [sigma]. Novel techniques for reconstructing 7ros at STAR are discussed, and a measurement of the unpolarized cross section presented. Finally, the measured ALL is compared to perturbative QCD predictions and from this comparison constraints are placed on [delta] [sigma]., by Alan Michael Hoffman., Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2009., Includes bibliographical references (p. 53-55)., The OLYMPUS experiment seeks to measure the ratio of the cross sections for e--p and e+-p scattering in order to determine the magnitude of two photon interactions in lepton nucleon scattering. Measuring this observable to the accuracy required is dependent on a good understanding of the systematic uncertainties associated with the scattering experiment. To accomplish this, a simulation using the GEANT4 library and reconstruction code was written and studies were performed. This paper serves to document the software written and its use in understanding the experiment and some systematic uncertainties., by Nicholas Lee Harrington., S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2009., In title on title page, "the square root of sigma" appears as the mathematical symbol, and "sigma" appears as the lower-case Greek letter. Cataloged from PDF version of thesis., Includes bibliographical references (p. 123-126)., Twenty years of polarized lepton-nucleon scattering experiments have found that the contribution from quark spins (1/2[delta] [sigma]) to the spin of the proton is only ~ 35%. This has lead researchers to look elsewhere, specifically to gluon spin ([delta sigma]) for a large contribution to proton spin. [delta sigma] has been only loosely constrained in polarized DIS and SIDIS experiments. Polarized proton-proton collisions at RHIC provide sensitivity to [delta sigma] through measurements of the longitudinal double-spin asymmetry, ALL. This work presents a measurement of ALL for inclusive 7ro production in polarized proton-proton collisions using the STAR detector and data from RHIC Run 6. 7r0s are abundantly produced at mid-rapidity in proton-proton collisions, making them natural candidates for studies of [delta] [sigma]. Novel techniques for reconstructing 7ros at STAR are discussed, and a measurement of the unpolarized cross section presented. Finally, the measured ALL is compared to perturbative QCD predictions and from this comparison constraints are placed on [delta] [sigma]., by Alan Michael Hoffman., Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005., Includes bibliographical references (p. 207-217)., Elastic form factors are fundamental quantities that characterize the electromagnetic structure of the nucleon. High precision measurements of these quantities are essential in understanding the structure of hadronic matter. Although the proton elastic form factors are well known, knowledge of the neutron form factors has been limited due to the lack of pure neutron targets. Few nucleon targets, deuterium in particular, are typically used to study the electromagnetic structure of the neutron. Cross section measurements are not sufficient for high precision determination of the electric form factor of the neutron, ..., due to its small value. Recently, experiments using polarization observables which are proportional to the product of the electric and magnetic form factors of the neutron have been used instead. Such measurements require highly polarized electron beams and either a vector polarized neutron target (typically ²H) or else a neutron final state polarimeter. The Bates Large Acceptance Spectrometer Toroid (BLAST) provides a unique opportunity to measure! the shape of the neutron electric form factor at low momentum transfers. BLAST combines a high duty-factor polarized electron beam in the South Hall Ring (SHR), an Atomic Beam Source (ABS) target of highly polarized deuterium atoms and a large acceptance detector. This work reports the results of measurements of the neutron electric form factor using the ... reaction at five 4-momentum transfer squared, Q², points of 0.14, 0.20, 0.29, 0.38 and 0.50 (GeV/c)² using data taken in 2004. The experimental setup is discussed in detail and the results for ... are presented and discussed in the context of various theoretical predictions., (cont.) A fit to the world's data including new BLAST data determines ... to ... over 0 < Q² < 1 ((GeV/c)². The best fit includes contributions from a low Q² bump and a smooth dipole term., by Vitaliy Ziskin., Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005., Includes bibliographical references (p. 207-217)., Elastic form factors are fundamental quantities that characterize the electromagnetic structure of the nucleon. High precision measurements of these quantities are essential in understanding the structure of hadronic matter. Although the proton elastic form factors are well known, knowledge of the neutron form factors has been limited due to the lack of pure neutron targets. Few nucleon targets, deuterium in particular, are typically used to study the electromagnetic structure of the neutron. Cross section measurements are not sufficient for high precision determination of the electric form factor of the neutron, ..., due to its small value. Recently, experiments using polarization observables which are proportional to the product of the electric and magnetic form factors of the neutron have been used instead. Such measurements require highly polarized electron beams and either a vector polarized neutron target (typically ²H) or else a neutron final state polarimeter. The Bates Large Acceptance Spectrometer Toroid (BLAST) provides a unique opportunity to measure! the shape of the neutron electric form factor at low momentum transfers. BLAST combines a high duty-factor polarized electron beam in the South Hall Ring (SHR), an Atomic Beam Source (ABS) target of highly polarized deuterium atoms and a large acceptance detector. This work reports the results of measurements of the neutron electric form factor using the ... reaction at five 4-momentum transfer squared, Q², points of 0.14, 0.20, 0.29, 0.38 and 0.50 (GeV/c)² using data taken in 2004. The experimental setup is discussed in detail and the results for ... are presented and discussed in the context of various theoretical predictions., (cont.) A fit to the world's data including new BLAST data determines ... to ... over 0 < Q² < 1 ((GeV/c)². The best fit includes contributions from a low Q² bump and a smooth dipole term., by Vitaliy Ziskin., Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005., Includes bibliographical references (p. 207-217)., Elastic form factors are fundamental quantities that characterize the electromagnetic structure of the nucleon. High precision measurements of these quantities are essential in understanding the structure of hadronic matter. Although the proton elastic form factors are well known, knowledge of the neutron form factors has been limited due to the lack of pure neutron targets. Few nucleon targets, deuterium in particular, are typically used to study the electromagnetic structure of the neutron. Cross section measurements are not sufficient for high precision determination of the electric form factor of the neutron, ..., due to its small value. Recently, experiments using polarization observables which are proportional to the product of the electric and magnetic form factors of the neutron have been used instead. Such measurements require highly polarized electron beams and either a vector polarized neutron target (typically ²H) or else a neutron final state polarimeter. The Bates Large Acceptance Spectrometer Toroid (BLAST) provides a unique opportunity to measure! the shape of the neutron electric form factor at low momentum transfers. BLAST combines a high duty-factor polarized electron beam in the South Hall Ring (SHR), an Atomic Beam Source (ABS) target of highly polarized deuterium atoms and a large acceptance detector. This work reports the results of measurements of the neutron electric form factor using the ... reaction at five 4-momentum transfer squared, Q², points of 0.14, 0.20, 0.29, 0.38 and 0.50 (GeV/c)² using data taken in 2004. The experimental setup is discussed in detail and the results for ... are presented and discussed in the context of various theoretical predictions., (cont.) A fit to the world's data including new BLAST data determines ... to ... over 0 < Q² < 1 ((GeV/c)². The best fit includes contributions from a low Q² bump and a smooth dipole term., by Vitaliy Ziskin., Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006., In title on t.p., double-underscored characters: "n" appears as superscript and under subscript "M"; [right arrow] appears as the symbol above the letters "H" and "e"., Includes bibliographical references (p. 200-207)., The neutron magnetic form factor GnM has been measured using the inclusive electro-disintegration 2H(e, e') of the deuteron for the first time. The longitudinally polarized electron beam of the MIT-Bates Linear Accelerator was used in conjunction with an isotopically pure, polarized deuterium internal gas target. The Bates Large Acceptance Spectrometer Toroid (BLAST) was used for the measurement. The form factor GnM was extracted from the ratio of the inclusive asymmetry [alpha]Ved in perpendicular over parallel kinematics and at Q2 = 0.135, 0.189, 0.252, 0.316 (GeV/c)2., by Nikolas Meitanis., Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2004., MIT Institute Archives copy: leaves 2-22 bound in reverse order., Includes bibliographical references (leaf 22)., This study is concerned with the percentage of [gamma]-rays of a certain energy having their energy correctly measured by a high purity Germanium [gamma]-ray detector. The ratio between the total counts and the counts within the energy peak (total-to-peak ratio) is determined for seven energies ranging from 89 keV to 1275 keV. A Monte Carlo based on the physical parameters of the detector was used to extrapolate between these points and after an energy independent scaling factor fit the data with a reduced [chi]² slightly below 1. The same experiment was repeated with a lead brick and then a β detector near the Ge detector and these objects were found to not have an effect on the total-to-peak ratios within the precision of the experiment., by Justin Matthew Nelson., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2004., MIT Institute Archives copy: leaves 2-22 bound in reverse order., Includes bibliographical references (leaf 22)., This study is concerned with the percentage of [gamma]-rays of a certain energy having their energy correctly measured by a high purity Germanium [gamma]-ray detector. The ratio between the total counts and the counts within the energy peak (total-to-peak ratio) is determined for seven energies ranging from 89 keV to 1275 keV. A Monte Carlo based on the physical parameters of the detector was used to extrapolate between these points and after an energy independent scaling factor fit the data with a reduced [chi]² slightly below 1. The same experiment was repeated with a lead brick and then a β detector near the Ge detector and these objects were found to not have an effect on the total-to-peak ratios within the precision of the experiment., by Justin Matthew Nelson., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2004., MIT Institute Archives copy: leaves 2-22 bound in reverse order., Includes bibliographical references (leaf 22)., This study is concerned with the percentage of [gamma]-rays of a certain energy having their energy correctly measured by a high purity Germanium [gamma]-ray detector. The ratio between the total counts and the counts within the energy peak (total-to-peak ratio) is determined for seven energies ranging from 89 keV to 1275 keV. A Monte Carlo based on the physical parameters of the detector was used to extrapolate between these points and after an energy independent scaling factor fit the data with a reduced [chi]² slightly below 1. The same experiment was repeated with a lead brick and then a β detector near the Ge detector and these objects were found to not have an effect on the total-to-peak ratios within the precision of the experiment., by Justin Matthew Nelson., S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2004., MIT Institute Archives copy: leaves 2-22 bound in reverse order., Includes bibliographical references (leaf 22)., This study is concerned with the percentage of [gamma]-rays of a certain energy having their energy correctly measured by a high purity Germanium [gamma]-ray detector. The ratio between the total counts and the counts within the energy peak (total-to-peak ratio) is determined for seven energies ranging from 89 keV to 1275 keV. A Monte Carlo based on the physical parameters of the detector was used to extrapolate between these points and after an energy independent scaling factor fit the data with a reduced [chi]² slightly below 1. The same experiment was repeated with a lead brick and then a β detector near the Ge detector and these objects were found to not have an effect on the total-to-peak ratios within the precision of the experiment., by Justin Matthew Nelson., S.B.

In dealing with problems of inheritance in domestic animals the emphasis tends to be placed on those factors which are of economic importance. Such factors are likely to be the result of many interacting and related causes, both genetic and environmental. This has resulted in the use of an approach based on the concepts of multifactorial and population genetics of Fisher, Wright and other workers. Using these concepts, the existence of certain genetic and phenotypic correlations can be shown and the results of certain selection policies predicted. However it is of considerable interest to know the mechanisms whereby these correlations arise. One such mechanism is pleiotropy, and it is proposed in this thesis to show how N-type Romney sheep (Dry and Fraser 1947) can, by a study of the pleiotropy of the gene N, be used to investigate the chain of events leading to various genetic and environmental correlations amongst fleece and body characters of the sheep. The first part of the thesis is concerned with preliminary investigations of the growth of the N-type sheep, which were initiated as part of a study of the carcass quality of lambs from these sheep. It was as a result of this study that the potentialities for the second year's work were realised. The second part is concerned with realising these potentialities in a study of the relationship of the body growth of the lamb and the development of the fleece.