Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1992. / Includes bibliographical references. / by Christopher J. Corcoran. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006. / Includes bibliographical references (p. 121-130). / This thesis details construction of a new apparatus for the production of 87Rb Bose-Einstein condensates and a subsequent quantum Zeno effect experiment. An experimental apparatus for producing large Bose-Einstein condensates of 87Rb is described in detail. A high flux thermal atomic beam is decelerated by a Zeeman slower and is then captured and cooled in a magneto-optical trap. The atoms are then transfered into a cloverleaf style Ioffe-Pritchard magnetic trap and cooled to quantum degeneracy with radio frequency induced forced evaporation. Condensates containing up to 20 million atoms can be produced every few minutes. The quantum Zeno effect is the suppression of transitions between quantum states by frequent measurement. Oscillation between two ground hyperfine states of a magnetically trapped 87Rb Bose-Einstein condensate, externally driven at a transition rate WR, was substantially suppressed by destructively measuring one of the levels with resonant optical scattering. While an ideal continuous measurement will stop the transition, any real measurement method will occur at a finite rate. The suppression of the transition rate in the two level system was quantified for pulsed measurements with a time between pulses t and weak continuous measurements with a scattering rate y. We observe that the weak continuous measurements exhibit the same suppression in the transition rate as the pulsed measurements when ySt = 3.60(0.43). This is in agreement with the previously predicted value of 4. Increasing the measurement frequency suppressed the transition rate to 0.005WR. / by Erik William Streed. / Ph.D.

Massachusetts Institute of Technology. Dept. of Physics. Thesis. 1970. Ph.D. / Vita. / Bibliography: leaves 114-115. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2006. / Includes bibliographical references (leaves 61-64). / We consider geometrically thin accretion disks around millisecond X-ray pulsars. We start with the Shakura-Sunyaev thin disk model as a basis and modify the disk equations with a magnetic torque from the central neutron star. Disk solutions are computed for a range of neutron star magnetic fields. We also investigate the effect of different equations of state and opacities on the disk solutions. We show that there are indications of thermal instability in some of the disk solutions, especially for the higher values of 3M. We also explain how the time evolution of the disk solutions can be calculated. / by Antonia Stefanova Savcheva. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 47-48). / The Dark Matter Time Projection Chamber (DMTPC) is a low pressure (CF 4) detector that measures the two-dimensional vector direction of nuclear recoils, and it aims to directly detect dark matter. This paper explores cosmic ray interactions with the four charge-coupled devices (CCDs) of the 4-shooter detector, the largest existing prototype detector in the DMTPC project, by looking at surface runs at MIT with detector voltages off. Through this, the depth of the depletion region of each CCD is found, which can be further used in understanding not only background rejection but also in understanding the relationship between measured CCD counts and energy deposited in the detector. / by HyoJeong Choi. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2007. / Includes bibliographical references (p. 49-50). / Helical ribbons form in a many multi-component solutions containing sterols similar to cholesterol, but remarkably, almost all the helices have a pitch angle of 11⁰ or 54⁰. The consistent pitch angle of the ribbons may be due to an underlying crystal structure. In order to determine the crystal structure, I undertook x-ray scattering studies of individual helical ribbons taken from two particular solutions: Chemically Defined Lipid Solution and model bile. Using a synchrotron x-ray source I observed Bragg reflections from ribbons with a pitch angle of 11⁰. From the diffraction patterns, I was able to deduce the parameters of the unit cell. The crystal structure of these ribbons is similar to that of cholesterol monohydrate, with the important difference that the length of the unit cell perpendicular to the cholesterol layers is tripled. Furthermore, I found that adjacent layers are shifted relative to each other along a single direction, and that the shift varies periodically with a period of 3 bilayers. I also found that the growth direction of the crystal is along one of the unit cell axes. / by Chintan Hossain. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2007. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / In title on title page, "[right arrow] appears as the symbol; and "[rho]", "[omega]" and "[gamma]" appear as lower-case Greek letters. / Includes bibliographical references (leaves 203-205). / This document describes the measurements of the branching fractions and isospin violations of the radiative electroweak penguin decays B [right arrow] ([rho]/[omega]) [gamma] at the asymmetric energy e+e- PEP-II collider with the BABAR detector. Together with the previously measured branching fractions of the decays ... the ratio of CKM-matrix elements Vtd=Vts are extracted and the length of the far side of the unitarity triangle is determined. / by Karsten Köneke. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2015. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 163-170). / A precision measurement of the Boron to Carbon ratio in cosmic rays is carried out in the range 1 GeV/n to 670 GeV/n using the first 30 months of flight data of AMS-02 located on the International Space Station. Above 20 GeV/n, it is the first accurate measurement. About 5 million clean Boron and Carbon nuclei are identified. The experimental and analysis challenges in achieving a high precision measurement are addressed. Boron is exclusively produced as a secondary particle by spallation from primary elements like Carbon in collisions with interstellar medium. The unprecedented precision and energy range of this measurement deepen the knowledge of cosmic ray propagation. Using this measurement, the diffusion coefficient in Gal-Prop model is determined to be (6.05 ± 0.05)10 28 cm2/s, and the Alfven velocity is (33.9 ± 1.0) km/s. This makes the prediction of secondary anti-proton background in dark matter search one order of magnitude more accurate. / by Wei Sun. / Ph. D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2017. / All instances of the symbol "±" appear as superscript. Cataloged from PDF version of thesis. / Includes bibliographical references (pages 90-94). / The CMS detector at the CERN LHC is sensitive to Standard Model predictions regarding the production of two W bosons with the same charge accompanied by two jets. In particular, when these particles are produced in a topology where the jets have a high invariant mass and are largely separated in pseudo-rapidity, the data can be used to test Standard Model predictions relating to vector boson scattering i.e. processes which have two incoming vector bosons and two outgoing vector bosons. This is interesting because it can be used to probe the couplings of the newly discovered Higgs boson to vector bosons. The channel in which the W bosons decay to charged leptons and neutrinos is the most sensitive and is thus the one that is used by the CMS Collaboration for the initial observation of this process. The data that is used is the 36 fb-1 of data that the CMS detector collected in 2016 at a proton-proton center-of-mass energy of 13 TeV. The main result is the observed significance for electroweak production of W±W± JJ, which is 5.5 standard deviations, consistent with the Standard Model expectation of 5.7 standard deviations. Additionally, limits are set on anomalous quartic gauge couplings and on the vector boson fusion production cross section times branching ratio to W± W± of doubly charged Higgs bosons in the Georgi-Macachek model. / by Andrew Levin. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, February 2003. / In title on t.p., double-underscored "x" appears as subscript. / Includes bibliographical references (p. 138-144). / by Philip Morgan Singer. / Ph.D.