Measurements of the reaction on a 4 He target have been carried out using both unpolarised and polarised photons. This work is the latest in a series of experiments conducted by the Edinburgh University Nuclear Physics group in collaboration with the Universities of Glasgow and Tubingen. The experiment was carried out using the 855 MeV MAMI­B electron accelerator at the Institut fur Kernphysik, Mainz, between March and August of 1996. The 855 MeV electrons from the accelerator were directed either, on to a 4 micron Nickel foil to produce unpolarised photons or on to a 0.1 mm Diamond to produce polarised photons. These photons were then tagged with a resolution of 2 MeV using a spectrometer. The photons then impinged on a 4 He cryotarget. Two sets of detectors were used to detect the reaction products. PiP, a plastic scintillator hodoscope, was used to detect the positive pions; and TOF a time ­of­ flight array, was used to detect the neutrons. Data was analysed for unpolarised photon energy regions centred at E =260,300,340 and 380 MeV and two polarised regions centred at E =258 and 338 MeV. The unpolarised data is presented as double and triple differential cross sec­ tions while the polarised data is presented as photon asymmetries of the corres­ ponding double differential cross section. A comparison is made with Plane Wave Impulse Approximation (PWIA) calculations by Louis Wright, both with and without final state interaction corrections. It is concluded that for the unpolar­ ised data a more sophisticated treatment of the final state interactions is required while for the polarised data reasonable agreement is found between experiment and theory.

Li King Fai = 額外次元模型內由額外力所導致的可測結果 / 李敬輝. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 101-105). / Text in English; abstracts in English and Chinese. / Li King Fai = E wai ci yuan mo xing nei you e wai li suo dao zhi de ke ce jie guo / Li Jinghui. / Chapter 1 --- Prologue --- p.1 / Chapter 1.1 --- Research Background --- p.1 / Chapter 1.2 --- Statement of the Problem --- p.4 / Chapter 1.3 --- Organization of the Thesis --- p.5 / Chapter 2 --- Review of Various Extra Dimensional Models --- p.6 / Chapter 2.1 --- General Relativity --- p.6 / Chapter 2.2 --- Kaluza-Klein Theory --- p.9 / Chapter 2.3 --- Space-Time-Matter Theory --- p.13 / Chapter 2.4 --- Arkani-Hamed-Dimopoulos-Dvali Scenario --- p.16 / Chapter 2.5 --- Randall-Sundrum Scenario --- p.19 / Chapter 3 --- Review of Extra Forces --- p.27 / Chapter 3.1 --- Definition of Force in 4D --- p.27 / Chapter 3.2 --- Extra Forces in STM Theory --- p.28 / Chapter 3.3 --- Variation of4D Mass --- p.31 / Chapter 3.4 --- Position-Momentum Uncertainty Relation --- p.32 / Chapter 3.5 --- Extra Forces in Brane Theories --- p.34 / Chapter 4 --- Extra Forces in the 5D Friedmann Universe --- p.37 / Chapter 4.1 --- Generalized Robertson-Walker Metric --- p.38 / Chapter 4.2 --- Unobserved Motions in Extra Dimensions --- p.43 / Chapter 4.3 --- Equations of Motion with Three Extra Spatial Dimensions --- p.51 / Chapter 4.4 --- Summary --- p.53 / Chapter 5 --- Extra Forces in the Randall-Sundrum Model --- p.55 / Chapter 5.1 --- Model Development - Evolving Extra Dimension --- p.56 / Chapter 5.2 --- Classical Particle Trajectories --- p.59 / Chapter 5.3 --- Unobserved Motions in Extra Dimensions --- p.66 / Chapter 5.4 --- Modification of RSI model --- p.72 / Chapter 5.5 --- Summary --- p.77 / Chapter 6 --- Comments on Extra Forces as the Source of Quantum Fluctuations --- p.78 / Chapter 7 --- Particle-Antiparticle Pairs as an Observable Effect of Extra Force --- p.80 / Chapter 7.1 --- Reasons for Antiparticles --- p.81 / Chapter 7.2 --- Attempts in Classical Physics --- p.85 / Chapter 7.3 --- 5D Kaluza-Klein Scenario --- p.86 / Chapter 7.4 --- Generalizations to Brane Theories --- p.89 / Chapter 7.5 --- Summary --- p.97 / Chapter 8 --- A Summary of this Thesis --- p.99 / Bibliography --- p.101

The goal of the MuSun experiment is to measure the rate lambda d of nuclear muon capture on the deuteron (mu + d rightarrow nu mu + n + n) with a precision of 1.5%. From this high precision measurement, MuSun will determine the sole unknown low-energy constant involved in modern, QCD-based, effective field theory calculations of weak nuclear reactions and provide unique constraints on electro-weak astrophysical processes of fundamental importance, whose rates have never been measured directly. These include pp fusion, which is the primary energy source in the sun and the main sequence stars, and the nu d reaction, which provided convincing evidence for solar neutrino oscillations at the Sudbury Neutrino Observatory. The two best measurements of Lambda d were performed over twenty years ago at the Paul Scherrer Institute and Vienna. The two experimental results agree but with large error bars on their measurements. Recent theoretical advances predict Lambda d = 399 Hz and Lambda d = 389 Hz, both with a relative uncertainty of only 1%. The uncertainties are low yet they clearly disagree with each other. The MuSun result will improve the experimental knowledge by a factor of 5 and help clarify the current uncertainties in the theoretical prediction. This dissertation describes the experimental design and setup of MuSun, an analysis of the data taken during the 2011 experimental run and approaches with which to tackle systematic effects that interfere with the measurement of the muon capture rate.

We calculate matrix elements for kaon to two pion decays in the Delta I = 3/2 channel using lattice gauge theory simulations. From these we can extract the decay amplitude A2, for which the real part is related to the decay rate and can be compared to the experimental result Re(A2) = 1.484 x 10^(-8) GeV, and for which the imaginary part is related to direct charge-parity violation in the neutral kaon system. We report the results of one simulation with nearly physical particle masses and kinematics, specifically mK = 509.0(9.1) MeV, mPi = 142.8(2.5) MeV, and EPiPi = 485.7(8.0) MeV. This simulation was performed on RBC/UKQCD 32^3 x 64, Ls = 32 lattices, using 2+1 dynamical flavors of domain wall fermions and a Dislocation Suppressing Determinant Ratio plus Iwasaki gauge action, and with an inverse lattice spacing a^(-1) = 1.373(24) GeV so that the spatial extent of the lattice is 4.60 fm and mPi*L = 3.3. We find that Re(A2) = 1.461(87)stat(200)sys x 10^(-8) GeV, in good agreement with the experimental value. We also find Im(A2) = -8.67(45)stat(1.95)sys x 10^(-13) GeV, and Im(A2)/Re(A2) = -5.93(27)stat(1.42)sys x 10^(-5), however the value of Im(A2) depends on a rough hypothesis for some of the renormalization constants which have not yet been calculated, and thus we quote a large systematic error. We also report the results of a simulation involving a variety of kaon and pion masses and momenta, which was conducted in order to study the dependence of the decay amplitude on particle masses and kinematics, and to study the effect of not having exactly physical masses and kinematics in the first simulation. The use of the quenched approximation and smaller spatial volume in this second simulation allowed for multiple masses to be simulated in a reasonable amount of time, but introduced an uncontrolled approximation and forced us to use pion masses a bit larger than the phys- ical mass. The study was conducted on 24^3 x 64, Ls = 16 lattices, with the quenched Doubly Blocked Wilson 2 gauge action, and an inverse lattice spacing of a^(-1) = 1.31(2) GeV. We find that an extrapolation to physical masses and kinematics yields values Re(A2) = 2.25(18)stat x 10^(-8) GeV and Im(A2) = -13.44(84)stat x 10^(-13) GeV. These results are significantly larger than those of the full dynamical simulation and of experiment. We attribute this mainly to the an inaccurate determination of the lattice spacing a using the rho mass, since it comes in as a^(-3) in the calculation of A2. Finally, a third simulation is performed with 2+1 dynamical flavors of domain wall fermions on a finer 32^3 x 64, Ls = 16 lattice, but only with pions that have nearly zero momentum. It, and the quenched simulation, are used mainly to estimate the systematic error in the first simulation, which is taken as the final result.

This dissertation describes a search for resonant WW and WZ production in the lvjj decay channel using 4.701 fb-1 of sqrt(s) = 7 TeV LHC collision data collected by the ATLAS detector. Events with a single charged lepton, at least two jets and missing transverse energy are analyzed and no significant deviation from the Standard Model prediction is observed. Upper limits on the production cross section are interpreted as lower limits on the mass of a resonance and are derived assuming two warped extra-dimension production modes: the original Randall-Sundrum (RS1) model and the more recent "bulk" Randal-Sundrum (Bulk RS) model. The mass range for both models is excluded at 95% CL with a lower mass limit for an RS1 graviton of 936 GeV and 714 GeV for the Bulk RS graviton.

This dissertation presents results from a search for reactor antineutrinoₑ flavor oscillations using the Double Chooz Far Detector. The search was performed by observing the rate and energy spectrum of antineutrinoₑ interacting via Inverse Beta Decay in a Gd-doped liquid scintillator detector, and comparing the observation to an expectation based on a prediction of the emitted reactor flux. The Columbia University neutrino group was instrumental in construction of the Double Chooz Outer Veto, as well as the analysis efforts leading to two oscillation measurement results. The most recent analysis is presented herein, focusing on 251.27 days of data (or 33.71 GW-ton-years of exposure). In these data, 8249 IBD candidates were observed, compared to a signal+background prediction of 8936.8. A fit to a two-neutrino oscillation model considering event rate, spectral shape, and time yields a best-fit value of sin² (2θ₁₃) = 0.109 ± 0.030 (stat.) ± 0.025 (syst.) at Δm 2/31 = 2.32 × 10⁻³ eV², with χ²_RS/d.o.f. = 42.1/35. A frequentist method deems the null-oscillation hypothesis excluded by the data at 99.8% C.L., or 2.9σ. These results are in agreement with the measurements of other modern reactor antineutrinoₑ experiments.

We report our recent development in algorithms and progress in measurements in lattice QCD. The algorithmic development includes the forecasted force gradient integrator, and further theoretical development and implementation of the Möbius domain wall fermions. These new technologies make it practical to simulate large 48^3*96 and 64^3*128 lattice ensembles with (5.5fm)^3 boxes and 140MeV pion. The calculation was performed using the Möbius domain wall fermions and the Iwasaki gauge action. Simulated directly at physical quark masses, these ensembles are of great value for our ongoing and future lattice measurement projects.With the help of measurement techniques such as the eigCG algorithm and the all mode averaging method, we perform a direct, precise lattice calculation of the semileptonic kaon decay K→πlν using these newly generated high quality lattice ensembles. Our main result is the form factor f^+_{Kπ}(q^2) evaluated directly at zero momentum transfer q^2=0. Free of various systematic errors, this new result can be used to determine the CKM matrix element Vus to a very high precision when combined with experimental input. The calculation also provides results for various low energy strong interaction constants such as the pseudoscalar decay constants f_K and f_π, and the neutral kaon mixing matrix element B_K. These calculations are naturally performed by reusing the propagators calculated for the kaon semileptonic decay mentioned above. So they come with no or very low additional cost. The results allow us to also determine these important low energy constants on the lattice to unprecedented accuracy.

We report our recent development in algorithms and progress in measurements in lattice QCD. The algorithmic development includes the forecasted force gradient integrator, and further theoretical development and implementation of the Möbius domain wall fermions. These new technologies make it practical to simulate large 48^3*96 and 64^3*128 lattice ensembles with (5.5fm)^3 boxes and 140MeV pion. The calculation was performed using the Möbius domain wall fermions and the Iwasaki gauge action. Simulated directly at physical quark masses, these ensembles are of great value for our ongoing and future lattice measurement projects. With the help of measurement techniques such as the eigCG algorithm and the all mode averaging method, we perform a direct, precise lattice calculation of the semileptonic kaon decay K→πlν using these newly generated high quality lattice ensembles. Our main result is the form factor f^+_{Kπ}(q^2) evaluated directly at zero momentum transfer q^2=0. Free of various systematic errors, this new result can be used to determine the CKM matrix element Vus to a very high precision when combined with experimental input. The calculation also provides results for various low energy strong interaction constants such as the pseudoscalar decay constants f_K and f_π, and the neutral kaon mixing matrix element B_K. These calculations are naturally performed by reusing the propagators calculated for the kaon semileptonic decay mentioned above. So they come with no or very low additional cost. The results allow us to also determine these important low energy constants on the lattice to unprecedented accuracy.

A search for short baseline muon antineutrino disappearance with the SciBooNE and MiniBooNE experiments at Fermi National Accelerator Laboratory in Batavia, Illinois is presented. Short baseline muon antineutrino disappearance measurements help constrain sterile neutrino models. The two detectors observe muon antineutrinos from the same beam, therefore the combined analysis of their data sets serves to partially constrain some of the flux and cross section uncertainties. A likelihood ratio method was used to set a 90% confidence level upper limit on muon antineutrino disappearance that dramatically improves upon prior sterile neutrino oscillation limits in the Δm^2=0.1-100 eV^2 region.

A measurement of the jet multiplicity in di-leptonically decaying ttbar events (i.e. ttbar → (ee, μμ, eμ) + missing transverse momentum + jets) is presented, using 4.66 fb -1 of data collected from √ s = 7 TeV pp collisions at the CERN Large Hadron Collider. In order to mitigate the effects of systematic uncertainties associated with jet energy measurements, a measurement of the ratio of the number of di-lepton ttbar events with N + 2 jets to Z → ℓ ℓ + N jet events is also determined. The results are unfolded for detector effects and compared to the particle-level predictions of several Monte Carlo generators, showing generally good agreement.