Nuclear Commons^™

Direct Measurements Of Two Photon Exchange On Lepton-Proton Elastic Scattering Using Simultaneous Electron-Positron Beams In Clas, Dasuni Kalhari Adikaram

Physics Theses & Dissertations

The electric (GE) and magnetic ( GM) form factors of the proton are fundamental observables which characterize its charge and magnetization distributions. There are two methods to measure the proton form factors: the Rosenbluth separation method and the polarization transfer technique. However, the ratio of the electric and magnetic form factors measured by those methods significantly disagree at momentum transfer Q² > 1 GeV². The most likely explanation of this discrepancy is the inclusion of two-photon exchange (TPE) amplitude contributions to the elastic electron-proton cross section which significantly changes the extraction of GE from the …

Photoproduction Of Π0 On Hydrogen With Clas From 1.1 Gev - 5.45 Gev Using E+E –Γ Decay, Michael C. Kunkel

Physics Theses & Dissertations

Photoproduction of the π⁰ meson was studied using the CLAS detector at the Thomas Jefferson National Accelerator Facility using tagged incident photon energies spanning the range E_γ = 1.1 GeV - 5.45 GeV. The measurement is performed on a liquid hydrogen target in the reaction γp → pe ⁺e^–(γ). The final state of the reaction is the sum of two subprocesses for π⁰ decay, the Dalitz decay mode of π⁰ → e ⁺e^–γ and conversion mode where one photon from π⁰ → γγ decay is converted into a …

Measurement Of The Spin Structure Function Gd1 Of The Deuteron And Its Moments At Low Q2, Krishna P. Adhikari

Physics Theses & Dissertations

Double polarization cross section differences (Δσ ||) for proton and deuteron targets have been measured in the EG4 experiment using the CLAS detector at Jefferson Lab. Longitudinally polarized electron beams at relatively low energies of 1.056, 1.337, 1.989, 2.256 and 3.0 GeV from the CEBAF accelerator were scattered off longitudinally polarized NH₃ and ND₃ targets. Scattered electrons were recorded at very low scattering angles (down to θ= 6°) with the help of a new dedicated Cherenkov counter and a special magnetic field setting of the CLAS detector in order to measure the cross section differences in the …

Double Spin Asymmetry In D →(E→E'P)N, Michael Mayer

Physics Theses & Dissertations

Using the CLAS detector at Jefferson Lab, double spin asymmetries (A ∥) for quasi-elastic electron scattering off the deuteron have been measured at several beam energies. The data were collected during the EG1 experiment, which scattered longitudinally polarized electrons with energies from 1.6 to 5.8 GeV off a longitudinally polarized cryogenic ND₃ target. The double spin asymmetries were measured as a function of photon virtuality Q² (0.13-3.17 (GeV/c)2), missing momentum (0.0-0.5 GeV/c), and the angle between the (inferred) "spectator" neutron and the momentum transfer direction (θ_ng). The results from EG1b are compared with a recent model …

Spin Dependence In Polarized Proton-Proton Elastic Scattering At Rhic, Donika Plyku

Physics Theses & Dissertations

The STAR (Solenoidal Tracker At RHIC - Relativistic Heavy Ion Collider) experiment is equipped with Roman Pots, insertion devices that allow detectors to be moved close to the beam for the measurement of high energy protons scattered at very small angles. This setup, together with the unique capability of RHIC to collide spin-polarized proton beams, allows STAR to study both the dynamics and the spin-dependence of the proton-proton ( pp) elastic scattering process. Silicon strip detectors, installed inside the Roman Pots, measure tracks of protons scattered diffractively at very small angles. In a dedicated run with special beam optics …

Measurement Of Polarized Proton-Proton Elastic Scattering At The Relativistic Heavy Ion Collider (Rhic), Ivan Koralt

Physics Theses & Dissertations

Elastic proton-proton (pp) scattering is one of the most fundamental processes in nature and yet, it is one of the most difficult to describe. There are two interactions involved in this process: electromagnetic (Coulomb) and hadronic (strong) interactions. Underlying exchange mechanisms of these two interactions are the virtual photon and the Pomeron exchange, respectively. The difficulty of elastic pp scattering arises from the fact that the nature of the Pomeron and its exchange are not well understood and need a theoretical approach, which is still under development.

At the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab …

Single And Double Spin Asymmetries For Pion Electro-Production From The Deuteron In The Resonance Region, Sharon L. Careccia

Physics Theses & Dissertations

The single and double spin asymmetries A_t and A_et have been measured in π^- electro-production off the deuteron using a longitudinally polarized electron beam and a polarized ND₃ target. The electron beam was polarized using a strained GaAs cathode and the target was polarized using Dynamic Nuclear Polarization. The data were collected at beam energies of 1.6, 1.7, 2.5 and 4.2 GeV in Hall B at Jefferson Lab in the spring of 2001. The final state particles were detected in the CEBAF Large Acceptance Spectrometer (CLAS). The d(e,e'π-p)p exclusive channel was identified using the missing mass …

Triple Coincidence Beam Spin Asymmetry Measurements In Deeply Virtual Compton Scattering, Mustafa Canan

Physics Theses & Dissertations

The Generalized Parton Distributions (GPDs) provides hitherto the most complete information about the quark structure of hadron. GPDs are accessible through hard-exclusive reactions, among which Deeply Virtual Compton Scattering (DVCS) is the cleanest reaction. A dedicated DVCS experiment on Hydrogen (E00-110) ran in the Hall A at Jefferson Laboratory in Fall 2004. I present here Beam Spin Asymmetry (BSA) results for the ep → epγ reaction studied in the E00-110 experiment with fully exclusive triple coincidence H(e, e'γp ) detection. I present a re-calibration of the electromagnetic calorimeter used to detect the high energy photon. This calibration …

Photoproduction Of The Φ(1020) Meson In Neutral Decay Mode Γp → Φp → K(S)K(L)P, Heghine Seraydaryan

Physics Theses & Dissertations

The Φ(1020) meson photoproduction cross sections in the neutral decay mode Φ → K_SK_L are measured for the first time. This work presents measurements of differential cross sections, dσ/dt, dσ/d cos θ^Φ_c.m.; Φ decay angular distributions, W(cos θ) and W(Φ), and spin-density matrix elements, ρ⁰, in the Helicity and Gottfried-Jackson frames, in the energy range 1.6 GeV < E_γ < 2.6 GeV. We analyzed the photoproduction data of the g11a experiment collected on an LH2 target using the CLAS detectector at Hall B, TJNAF. The measured cross sections show some differences from the charged decay mode Φ → K⁺ K⁻.

Feasibility And Conceptual Design Of A C.W. Positron Source At Cebaf, Serkan Golge

Physics Theses & Dissertations

A feasibility study of a CW positron source for the 12 GeV upgrade at Jefferson Lab (JLAB) is provided. The proposed ≥ 100 nA Continuous Wave (CW) positron source at JLAB has several unique and challenging characteristics: high current incident electron beam at 126 MeV with a high beam power (up to a MW); CW e−beam and CW e+ production. The multiple scattering is a dominant process when creating e+ in a target, which results a large phase space area of the emitted positrons. An admittance study was done at CEBAF to find the maximum phase space area, which is …

Beyond The Born Approximation: A Precise Comparison Of E+P And E-P Elastic Scattering In The Cebaf Large Acceptance Spectrometer (Clas), Megh Raj Niroula

Physics Theses & Dissertations

How well we know the structure of the proton depends on our knowledge of the form factors of the proton. The ratio of the electromagnetic form factors of the proton measured by the Rosenbluth and the polarization transfer methods differ by a factor of 3 at four momentum transfer squared (Q²)=5.6 GeV². The two photon exchange (TPE) effect is the leading candidate to explain this discrepancy. The theoretical estimates of the TPE effect are model dependent so precise measurement is required to resolve this problem. The TPE effect can be measured in a model independent way by measuring …

Nuclear Electromagnetic Currents In Chiral Effective Field Theory, Saori Pastore

Physics Theses & Dissertations

A nucleon-nucleon potential and consistent nuclear electromagnetic currents are derived in chiral effective field theory retaining pions and nucleons as explicit degrees of freedom. The calculation of the potential is carried out up to next-to-next-to leading order (N²LO), while the currents include up to N³LO corrections. The potential at N² LO and currents at N³LO consist of two-pion-exchange and contact contributions. The currents are then utilized to study a number of low-energy electromagnetic observables induced by magnetic dipole transitions, such as the deuteron and trinucleon magnetic moments and the np, nd and n …

Exclusive Π- Electro-Production From The Neutron In The Resonance Region, Jixie Zhang

Physics Theses & Dissertations

The study of baryon resonances is crucial to our understanding of nucleon structure. Although the excited states of the proton have been studied in great detail, there are very few data available for the neutron resonances because of the difficulty inherent in obtaining a free neutron target. To overcome this limitation, the spectator tagging technique was used in one of the CEBAF Large Acceptance Spectrometer (CLAS) collaboration experiments, Barely off-shell Nuclear Structure (BoNuS), in Hall-B at Jefferson Lab. We have constructed a radial time projection chamber (RTPC) based on the gaseous electron multiplier (GEM) technology to detect low momentum …

High-Energy Amplitudes In Gauge Theories In The Next-To-Leading-Order, Giovanni Antonio Chirilli

Physics Theses & Dissertations

Scattering processes play a central role in physics, and high-energies experiments give us an insight into the fine structure of matter. The high-energy behavior of amplitudes in gauge theories can be reformulated in terms of the evolution of Wilson-line operators. In the leading order this evolution is governed by the non-linear Balitsky-Kovchegov (BK) equation. In order to see if this equation is relevant for existing or future deep inelastic scattering (DIS) accelerators (like Electron Ion Collider (EIC) or Large Hadron electron Collider (LHeC)) one needs to know how large are the next-to-leading order (NLO) corrections. In addition, the NLO corrections …

Spin Structure Of The Deuteron, Nevzat Guler

Physics Theses & Dissertations

Double spin asymmetries for the proton and the deuteron have been measured in the EG1b experiment using the CLAS detector at Jefferson Lab. Longitudinally polarized electrons at energies 1.6, 2.5, 4.2 and 5.7 GeV were scattered from longitudinally polarized NH3 and ND3 targets. The double spin asymmetry A|| for the proton and the deuteron has been extracted from these data as a function of W and Q² with unprecedented precision. The virtual photon asymmetry A₁ and the spin structure function g1 can be calculated from these measurements by using parametrization to the world data for the virtual …

Neutron Structure Functions Measured With Spectator Tagging, Svyatoslav Tkachenko

Physics Theses & Dissertations

We know much less about the neutron than the proton due to the absence of free neutron targets. Neutron information has to be extracted from data on nuclear targets like deuterium. This requires corrections for off-shell and binding effects which are not known from first principles and therefore are model-dependent. As a consequence, the same data can be interpreted in different ways, leading to different conclusions about important questions such as the value of the d/u quark ratio at large momentum fraction x. The Barely Off-shell NUcleon Structure (BONUS) experiment at Jefferson Lab addressed this problem by tagging spectator protons …

Measurements Of Correlated Pair Momentum Distributions In -3he(E,E',P,P)N With Clas, Hovhannes Baghdasaryan

Physics Theses & Dissertations

Nucleon-Nucleon (NN) Short Range Correlations (SRC) represent a valuable part of the nuclear wave function. Improved knowledge of SRC will give us a better understanding of nuclear matter and nuclear interactions in extreme conditions. A study of the effects of short-range correlations using the ³He(e, e'pp)n reaction measured at Jefferson Lab is presented. Two different approaches were selected to investigate SRC. The first approach consists of the kinematics when we investigate the two active protons and neutron is the spectator (was not involved in the interaction). This kinematics dominates by Final State Interactions which are reasonably …

Running Coupling Constant And Transition From Low To High Energies In Quantum Chromodynamics, Alexander Babansky

Physics Theses & Dissertations

The remarkable feature of QCD is that the coupling constant (the strength of the interaction) depends on the energy of the interacting particles. At high energies, the coupling constant vanishes and QCD becomes asymptotically free. However, at lower energy, the running coupling constant increases, leading to the confining strong-coupling theory at energies of the order of hadron masses. We study the essential effects of the running coupling constant and analyze the transition from high to low energies in different processes.

The ²H(E, E'P)N Reaction At High Four-Momentum Transfer, Hassan F. Ibrahim

Physics Theses & Dissertations

This dissertation presents the highest four-momentum transfer, Q², quasielastic (x_Bj = 1) results from Experiment E01-020 which systematically explored the 2H(e, e'p)n reaction ("Electro-disintegration" of the deuteron) at three different four-momentum transfers, Q² = 0.8, 2.1, and 3.5 GeV² and missing momenta, p_miss = 0, 100, 200, 300, 400, and 500 GeV including separations of the longitudinal-transverse interference response function, R_LT, and extraction of the longitudinal-transverse asymmetry, A_LT. This systematic approach will help to understand the reaction mechanism and the deuteron structure down to the short …

Inclusive And Exclusive Compton Processes In Quantum Chromodynamics, A. Psaker

Physics Theses & Dissertations

In our work, we describe two types of Compton processes. As an example of an inclusive process, we consider the high-energy photoproduction of massive muon pairs off the nucleon. We analyze the process in the framework of the QCD parton model, in which the usual parton distributions emerge as a tool to describe the nucleon in terms of quark and gluonic degrees of freedom. To study its exclusive version, a new class of phenomenological functions is required, namely, generalized parton distributions. They can be considered as a generalization of the usual parton distributions measured in deeply inelastic lepton-nucleon scattering. Generalized …

Spin Structure Functions Of The Deuteron Measured With Clas In And Above The Resonance Region, Kahanawita G. Vipuli G. Dharmawardane

Physics Theses & Dissertations

Spin structure functions of the nucleon in the region of large x and small to moderate Q² continue to be of high current interest. The first moment of the spin structure function g₁, Γ₁, goes through a rapid transition from the photon point (Q² = 0), where it is constrained by the Gerasimov-Drell-Hearn sum rule, to the deep inelastic limit where it is sensitive to the nucleon spin fraction carried by quarks. The interesting behavior in the transition region is dominated by baryon resonance excitations. We concluded an experiment to measure these observables …

Electron Scattering From A High Momentum Neutron In Deuterium, Alexei V. Klimenko

Physics Theses & Dissertations

The deuterium nucleus is a system of two nucleons (proton and neutron) bound together. The configuration of the system is described by a quantum-mechanical wave function and the state of the nucleons at a given time is not known a priori. However, by detecting a backward going proton of moderate momentum in coincidence with a reaction taking place on the neutron in deuterium, the initial state of that neutron can be inferred if we assume that the proton was a spectator to the reaction. This method, known as spectator tagging, was used to study the electron scattering from high-momentum neutrons …

Some Aspects Of Deeply Virtual Compton Scattering, Elena Kuchina

Physics Theses & Dissertations

We consider different aspects of the virtual Compton amplitude in QCD on two examples: small-x physics accessible in the Regge regime and twist-3 approximation in the description of DVCS through the general parton distributions. Using this model, we give an estimate for the cross section of deeply virtual Compton scattering for the kinematics of CEBAF at Jefferson Lab.

Nucleon-Nucleon Spin Dependent Scattering Amplitudes To Describe Final State Interactions In Electromagnetic And Electroweak Nuclear Processes, William P. Ford

Physics Theses & Dissertations

There are currently no models readily available that provide nucleon-nucleon spin dependent scattering amplitudes at high energies ( s ≥ 6 GeV²⁾. This work aims to provide a model for calculating these high-energy scattering amplitudes. The foundation of the model is Regge theory since it allows for a relativistic description and full spin dependence. A parameterization of the amplitudes is presented. and comparisons of the solution to the assembled data set are shown. In addition, an application of the model to describe final state interactions in deuteron electrodisintegration is presented. Overall the model works as intended, and provides …

Measurments Of Correlated Pair Momentum Distributions In 3he(E,E'Pp)N With Clas, Rustam Niyazov

Physics Theses & Dissertations

We have measured the ³He(e,e'pp)n reaction at 2.2 and 4.4 GeV over a wide kinematic range. The kinetic energy distribution for ’fast’ nucleons (p > 250 MeV/c) peaks where two nucleons each have 20% or less and the third or ‘leading’ nucleon carries most of the transferred energy. These fast nucleon pairs (both pp and pn) are back-to-back and carry very little momentum along q, indicating that they are spectators. Experimental and theoretical evidence indicates that we have measured N N correlations in ³He(e,e'pp)n by striking the third nucleon and detecting the spectator correlated pair.

Spin Structure Functions Of The Deuteron, Junho Yun

Physics Theses & Dissertations

Inclusive double spin asymmetries have been measured in [special characters omitted] using the CLAS detector and a polarized [special characters omitted] target at. Jefferson Lab in 1998. The goal of these measurements is to study the spin structure of the deuteron and the neutron in the low Q² transition region between the real photon point, where the Gerasimov-Drell-Hearn (GDH) sum rule is expected to be satisfied, and the deep inelastic scattering limit. The analysis and the results for virtual photon asymmetries, the spin structure function [special characters omitted] and its first moment within a Q² range of 0.2 …

Measurement Of The Gπnn(T) Form Factor, Kelly Gene Vansyoc

Physics Theses & Dissertations

Cross sections were measured for the reaction ¹H(e, e′π+) n at the energy W = 1.95 GeV and momentum transfer Q² = 0.6 (GeV/c)². At this W and Q², the longitudinal cross section is dominated by t-channel production, giving a unique opportunity to examine the strong coupling form factor gπNN(t). The measured cross sections were separated using a method similar to a Rosenbluth separation. For the extraction of gπNN(t), the Actor and Körner model [42] and a parameterization of the MAID2000 …

Phenomenological Description Of Double-Pion Photoproduction, Andry M. Rakotovao

Physics Theses & Dissertations

Double pion photoproduction off proton targets is studied, in the framework of an Effective Lagrangian approach at tree level, based on the coupling of photons and pions to nucleons and resonances. We consider N, Δ(1232), N(1440), N(1520) and N(1535) as intermediate baryonic states and ρ-meson as the intermediate 2π resonance. The general form of the amplitude is presented and total cross sections of the γp → π⁺π− p, γp → π⁰π⁰p and γp → π ⁺π⁰n processes are evaluated up to Eγ …

Electroweak Structure Of Three-And Four-Body Nuclei, Laura Elisa Marcucci

Physics Theses & Dissertations

This work reports results for (i) the elastic electromagnetic form factors of the trinucleons; (ii) the nuclear response functions of interest in [e → e'] experiments, at excitation energies below the deuteron breakup threshold; (iii) the astrophysical S-factor for proton weak capture on ³He (the hep reaction). The initial and final state wave functions are calculated using the correlated hyperspherical harmonics method, from a realistic Hamiltonian consisting of the Argonne ^v18 two-nucleon and Urbana IX three-nucleon interactions. The nuclear electroweak charge and current operators include one- and many-body components. The predicted magnetic form factor of …

Precision Measurement Of The Spin Structure Of The Proton And The Deuteron, Frank R. Wesselmann

Physics Theses & Dissertations

Experiment E155 at the Stanford Linear Accelerator Center measured the spin structure functions g1 and g2 of the proton and deuteron using deep inelastic scattering of 50 GeV polarized electrons from dynamically polarized, solid ¹⁵NH₃ and ⁶LiD targets. Three independent spectrometers, covering a large kinematic region, 0.014 < x_Bjorken < 0.9 and 1 < Q² < 40 (GeV /c)^2, detected 200 million events. A fully self-consistent and statistically sound approach to calculating radiative corrections was developed, providing well-defined statistical errors for the E155 data set. Also, a comprehensive fit to the global data set was created which simultaneously …