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Measurement of single-target spin asymmetries in the electroproduction of negative pions in the semi-inclusive deep inelastic reaction n{up_arrow}(e,e'{pi}{sup -})X on a transversely polarized {sup 3}He target

Description: The experiment E06010 measured the target single spin asymmetry (SSA) in the semiinclusive deep inelastic (SIDIS) n{up_arrow}(e, e'{pi}{sup -})X reaction with a transversely polarized {sup 3}He target as an e#11;ective neutron target. This is the very #12;rst independent measurement of the neutron SSA, following the measurements at HERMES and COMPASS on the proton and the deuteron. The experiment acquired data in Hall A at Je#11;erson Laboratory with a continuous electron beam of energy 5.9 GeV, probing the valence quark region, with x = 0.13 {rt_arrow} 0.41, at Q{sup 2} = 1.31 {rt_arrow} 3.1 GeV{sup 2}. The two contributing mechanisms to the measured asymmetry, viz, the Collins effect and the Sivers effect can be realized through the variation of the asymmetry as a function of the Collins and Sivers angles. The neutron Collins and Sivers moments, associated with the azimuthal angular modulations, are extracted from the measured asymmetry for the very #12;first time and are presented in this thesis. The kinematics of this experiment is comparable to the HERMES proton measurement. However, the COMPASS measurements on deuteron and proton are in the low-x region. The results of this experiment are crucial as the first step toward the extraction of quark transversity and Sivers distribution functions in SIDIS. With the existing results on proton and deuteron, these new results on neutron will provide powerful constraints on the transversity and Sivers distributions of both the u and d-quarks in the valence region.
Date: June 1, 2010
Creator: Dutta, Chiranjib
Partner: UNT Libraries Government Documents Department

Photodisintegration of Light Nuclei with CLAS

Description: We report preliminary results of photodisintegration of deuteron and {sup 3}He measured with CLAS at Jefferson Lab. We have extracted the beam-spin asymmetry for the {vector {gamma}}d {yields} pn reaction at photon energies from 1.1 GeV to 2.3 GeV and proton center-of-mass (c.m.) angles between 35{degrees}#14; and 135{degrees}#14;. Our data show interesting evolution of the angular dependence of the observable as the photon energy increases. The energy dependence of the beam-spin asymmetry at 90#14; shows a change of slope at photon energy of 1.6 GeV. A comparison of our data with model calculations suggests that a fully non-perturbative treatment of the underlying dynamics may be able to describe the data better than a model based on hard scattering. We have observed onset of dimensional scaling in the cross section of two-body photodisintegration of {sup 3}He at remarkably low energy and momentum transfer, which suggests that partonic degrees of freedom may be relevant for the description of nuclei at energies lower than previously considered.
Date: August 1, 2013
Creator: Ilieva, Yordanka Yordanova & Zachariou, Nicholas
Partner: UNT Libraries Government Documents Department

Nuclear electromagnetic charge and current operators in Chiral EFT

Description: We describe our method for deriving the nuclear electromagnetic charge and current operators in chiral perturbation theory, based on time-ordered perturbation theory. We then discuss possible strategies for fixing the relevant low-energy constants, from the magnetic moments of the deuteron and of the trinucleons, and from the radiative np capture cross sections, and identify a scheme which, partly relying on {Delta} resonance saturation, leads to a reasonable pattern of convergence of the chiral expansion.
Date: August 1, 2013
Creator: Girlanda, Luca; Marcucci, Laura Elisa; Pastore, Saori; Piarulli, Maria; Schiavilla, Rocco & Viviani, Michele
Partner: UNT Libraries Government Documents Department

Meausrement of the Neutron Radius of {sup 208}Pb Through Parity Violation in Electron Scattering

Description: In contrast to the nuclear charge densities, which have been accurately measured with electron scattering, the knowledge of neutron densities still lack precision. Previous model-dependent hadron experiments suggest the difference between the neutron radius, R{sub n}, of a heavy nucleus and the proton radius, R{sub p}, to be in the order of several percent. To accurately obtain the difference, R{sub n}-R{sub p}, which is essentially a neutron skin, the Jefferson Lab Lead ({sup 208}Pb) Radius Experiment (PREX) measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from {sup 208}Pb at an energy of 1.06 GeV and a scattering angle of 5{degrees}#14;. Since Z{sup 0} boson couples mainly to neutrons, this asymmetry provides a clean measurement of R{sub n} with respect to R{sub p}. PREX was conducted at the Jefferson lab experimental Hall A, from March to June 2010. The experiment collected a final data sample of 2x#2;10{sup 7} helicity-window quadruplets. The measured parity-violating electroweak asymmetry A{sub PV} = 0.656 {+-}#6; 0.060 (stat) {+-}#6; 0.014 (syst) ppm corresponds to a difference between the radii of the neutron and proton distributions, R{sub n}-R{sub p} = 0.33{sup +0.16}{sub -0.18} fm and provides the #12;first electroweak observation of the neutron skin as expected in a heavy, neutron-rich nucleus. The value of the neutron radius of {sup 208}Pb has important implications for models of nuclear structure and their application in atomic physics and astrophysics such as atomic parity non-conservation (PNC) and neutron stars.
Date: May 31, 2013
Creator: Saenboonruang, Kiadtisak
Partner: UNT Libraries Government Documents Department

Study of the (e,e'p) quasi-elastic reaction in complex nuclei: theory and experiment

Description: Experimental coincidence cross section and transverse-longitudinal asymmetry A{sub TL} have been obtained for the quasielastic (e,e'p) reaction in {sup 16}O, {sup 12}C, and {sup 208}Pb in constant q-ω kinematics in the missing momentum range -350 < p{sub miss} < 350 MeV/c. In these experiments, performed in experimental Hall A of the Thomas Jefferson National Accelerator Facility (JLAB), the beam energy and the momentum and angle of the scattered electrons were kept fixed, while the angle between the proton momentum and the momentum transfer q was varied in order to map out the missing momentum distribution. The experimental cross section and A{sub TL} asymmetry have been compared with Monte Carlo simulations based on Distorted Wave Impulse Approximation (DWIA) calculations with both relativistic and non-relativistic spinor structure. The spectroscopic factors obtained for both models are in agreement with previous experimental values, while A{sub TL} measurements favor the relativistic DWIA calculation. This thesis describes the details of the experimental setup, the calibration of the spectrometers, the techniques used in the data analysis to derive the final cross sections and the A{sub TL}, the ingredients of the theoretical calculations employed and the comparison of the results with the simulations based on these theoretical models.
Date: March 1, 2010
Creator: Herraiz, Joaquin Lopez
Partner: UNT Libraries Government Documents Department

GFMC calculations of electromagnetic moments and M1 transitions in A {<=} 9 nuclei

Description: We present recent Green’s function Monte Carlo calculations of magnetic moments and M1 transitions in A{<=}#20;9 nuclei, which include corrections arising from two-body meson-exchange electromagnetic currents. Two-body effects provide significant corrections to the calculated observables, bringing them in excellent agreement with the experimental data. In particular, we find that two body corrections are especially large in the A = 9, T = 3/2 systems, in which they account for up to ~#24; 20% (~#24; 40%) of the total predicted value for the {sup 9}Li ({sup 9}C) magnetic moment.
Date: August 1, 2013
Creator: Pastore, Saori; Pieper, Steven C.; Schiavilla, Rocco & Wiringa, Robert Bruce
Partner: UNT Libraries Government Documents Department

Caught in the Act

Description: Representing the Center for Defect Physics (CDP), this document is one of the entries in the Ten Hundred and One Word Challenge. As part of the challenge, the 46 Energy Frontier Research Centers were invited to represent their science in images, cartoons, photos, words and original paintings, but any descriptions or words could only use the 1000 most commonly used words in the English language, with the addition of one word important to each of the EFRCs and the mission of DOE: energy. The mission of the CDP is to enhance our fundamental understanding of defects, defect interactions, and defect dynamics that determine the performance of structural materials in extreme environments.
Date: July 18, 2013
Creator: Stocks, G. Malcolm; Morris, James; Sproles, Andrew; Henson, Priscilla & Graham, Kathy
Partner: UNT Libraries Government Documents Department

Measurement of the Electric and Magnetic Elastic Structure Functions of the Deuteron at Large Momentum Transfers

Description: The deuteron elastic structure functions, A(Q{sup 2}) and B(Q{sup 2}), have been extracted from cross section measurements of elastic electron-deuteron scattering in coincidence using the Continuous Electron Beam Accelerator and Hall A Facilities of Jefferson Laboratory. Incident electrons were scattered off a high-power cryogenic deuterium target. Scattered electrons and recoil deuterons were detected in the two High Resolution Spectrometers of Hall A. A(Q{sup 2}) was extracted from forward angle cross section measurements in the squared four-momentum transfer range 0.684 ≤ Q{sup 2} ≤ 5.90 (GeV/c){sup 2}. B(Q{sup 2}) was determined by means of a Rosenbluth separation in the range 0.684 ≤ Q{sup 2} ≤ 1.325 (GeV/c){sup 2}. The data are compared to theoretical models based on the impulse approximation with the inclusion of meson-exchange currents and to predictions of quark dimensional scaling and perturbative quantum chromodynamics. The results are expected to provide insights into the transition from meson-nucleon to quark-gluon descriptions of the nuclear two-body system.
Date: October 1, 1999
Creator: Suleiman, Riad
Partner: UNT Libraries Government Documents Department

Measurement of the deuteron elastic structure functions at large momentum transfers

Description: The cross section for elastic electron-deuteron scattering has been measured using the Hall A Facility of Jefferson Laboratory. Scattered electrons and recoiling deuterons were detected in coincidence in the two 4 GeV/c High Resolution Spectrometers (HRS) of Hall A. The deuteron elastic structure functions A(Q{sup 2}) and B(Q{sup 2}) have been extracted from these data. Results for the measurement of A(Q{sup 2}) in the range of 0.7 ≤ Q{sup 2} ≤ 6.0 (GeV/c){sup 2} are reported. Results for the magnetic structure function, B(Q{sup 2}), are presented in the range of 0.7 ≤ Q{sup 2} ≤ 1.35 (GeV/c){sup 2}. The results for both structure functions are compared to predictions of meson-nucleon based models, both with and without the inclusion of meson-exchange currents. The A(Q{sup 2}) results are compared to predictions of the dimensional scaling quark model and perturbative quantum chromodynamics. The results can provide insights into the transition from meson-nucleon to quark-gluon descriptions of the nuclear two-body system.
Date: August 1, 1999
Creator: McCormick, Kathy
Partner: UNT Libraries Government Documents Department

A study of the {sup 16}O (e, e'p) reaction at deep missing energies

Description: The {sup 16}O(e,e'p)#8; reaction was studied in the #6;first physics experiment performed at Jefferson lab Hall A. In the quasielastic region cross sections were measured for both quasi#11;parallel and perpendicular kinematics at q = 1000 MeV and #2;{omega} = 445#14;#14;#15; MeV. From the data acquired in quasi#11;parallel kinematics#4; longitudinal and transverse response functions#4; R{sub L} and R{sub T} were separated for E{sub miss} < 60 MeV. The perpendicular kinematics data were used to extract R{sub LT}, #4; R{sub T},#4; and R{sub L#16;} + V{sub TT}/V{sub L}R{sub TT} response functions for the same E{sub miss} range and for P{sub miss} < 310 MeV#18;c. The {sub 16}O(#7;e,#4;e'p)#8; cross section was measured in the dip region at q = 1026 MeV and #2; {omega} = 586#12;#15;#19;#2; MeV for 10 MeV <#3; E{sub miss} < 320 MeV. This thesis presents the results for the missing energy continuum (#7;E{sub miss}>25#4; #3;#15; MeV)#8; from this experiment.
Date: February 1, 1999
Creator: Liyanage, Nilanga
Partner: UNT Libraries Government Documents Department

ANGULAR MOMENTUM MISALIGNMENT IN DEEP INELASTIC PROCESSES AND ANGULAR DISTRIBUTION OF SEQUENTIALLY EMITTED PARTICLES AND GAMMA RAYS

Description: The angular momentum misalignment for fragments produced in deep inelastic scattering is discussed in terms of the thermal excitation of angular-momentum-bearing modes in the intermediate complex. Analytical expressions for the in- and out-of-plane angular distributions are obtained for sequentially emitted particles and fission fragments. The angular momentum dependence of the ratio between particle and neutron decay width is explicitly treated and found to be quite important. Similarly angular distributions are obtained both for dipole and quadrupole gamma decay. The theoretical results are compared with experimental angular distributions of sequential fission fragments, sequential alphas and gamma rays and a good agreement is found.
Date: December 1, 1980
Creator: Moretto, L.G.; Blau, S. & Pacheco, A.
Partner: UNT Libraries Government Documents Department

FISSION OF {sup 238}U INDUCED BY INELASTIC SCATTERING OF 120 MeV {alpha}-PARTICLES

Description: The fission decay of {sup 238}U has been measured as function of excitation energy in inelastic scattering of 120 MeV {alpha}-particles. Total kinetic energies and masses of fission fragments were measured by the double energy method. It is observed that the total kinetic energy E{sub K} decreases and that the valley in the mass distribution is reduced when the excitation energy of the system is increased. No indication of anomalous total kinetic energy release in the region of the giant quadrupole resonance has been found. A qualitative interpretation of the data is given on the basis of a static scission point model.
Date: September 1, 1980
Creator: Back, B.B.; Shotter, A.C.; Symons, T.J.M.; Bice, A.; Gelbke, C.K.; Awes, T.C. et al.
Partner: UNT Libraries Government Documents Department

GROUND STATE PROPERTIES OF O{sup 16}, Ca{sup 40} AND Ca{sup 48} IN A RELATIVISTIC HARTREE THEORY OF NUCLEAR MATTER

Description: A relativistic field theory model of nuclear matter is solved in a Hartree approximation for finite nuclei. We show that the theory predicts small shell effects for the charge density distributions in magic nuclei and is in agreement with recent electron scattering data. The effects of the small component of the relativistic wave function are investigated as well as the role of the isospin dependent force generated by the rho field.
Date: December 1, 1980
Creator: Boguta, J.
Partner: UNT Libraries Government Documents Department

ANGULAR MOMENTUM TRANSFER AND PARTITION IN THE DEEP-INELASTIC REACTION: 664 MeV {sup 84}Kr + {sup nat}Ag.

Description: In- and out-of plane angular distributions have been measured for sequential alpha decay from target-like fragments produced in fully relaxed heavy-ion collisions. At angles equal to or larger than the target-recoil direction, the {alpha}-particle energy spectra are evaporation- like and the in-plane angular distributions are consistent with isotropy in the rest frame of the target recoil. The out-of-plane distributions exhibit an anisotropy of approximately two. Fragment spins were extracted from these distributions as a function of mass asymmetry. These spins are in agreement with those obtained from a simultaneous gamma-ray multiplicity measurement. Both the fragment kinetic energies and intrinsic spins are consistent with rigid rotation of an intermediate complex consisting of two substantially deformed spheroids in near proximity.
Date: April 1, 1981
Creator: Sobotka, L.G.; Hsu, C.C.; Wozniak, G.J.; Morrissey, D.J. & Moretto, L.G.
Partner: UNT Libraries Government Documents Department

JETS OF NUCLEAR MATTER FROM HIGH ENERGY HEAVY ION COLLISIONS

Description: The nuclear fluid dynamical model with final thermal breakup is used to study the reactions {sup 20}Ne + {sup 238}U and {sup 40}Ar + {sup 40}Ca at E{sub LAB} = 390 MeV/n. The calculated double differential cross sections d{sup 2}{sigma}/d{Omega}dE are in agreement with recent experimental data. However, it is shown that the azimuthal dependence of the triple differential distributions d{sup 3}{sigma}/dEdcos{theta}d{phi}, to be obtained from 4{pi} exclusive experiments with single event analysis, can yield considerably deeper insight into the collision process and allow for snapshots of the reactions. Strongly correlated jets of nuclear matter are predicted.
Date: February 1, 1981
Creator: Stocker, H.; Csernai, L.P.; Graebner, G.; Buchwald, G.; Kruse, H.; Cusson, R.Y. et al.
Partner: UNT Libraries Government Documents Department

JETS OF NUCLEAR MATTER FROM HIGH ENERGY HEAVY ION COLLISIONS

Description: The nuclear fluid dynamical model with final thermal breakup is used to study the reactions {sup 20}Ne + {sup 238}U and {sup 40} Ar + {sup 40}Ca at E{sub LAB}=390 MeV/n. Calculated double differential cross sections d{sup 2}{sigma}/d{Omega}dE are in agreement with recent experimental data. It is shown that azimuthally dependent triple differential cross sections d{sup 3}{sigma}/dEd cos{theta}d{phi} yield considerably deeper insight into the collision process and allow for snapshots of the reactions. Strongly correlated jets of nuclear matter are predicted.
Date: November 1, 1980
Creator: Stocker, H.; Csernai, L.P.; Graebner, G.; Buchwald, G.; Kruse, H.; Cusson, R.Y. et al.
Partner: UNT Libraries Government Documents Department

CALCULATION OF MUON FINAL PROBABILITIES AFTER MUON-INDUCED FISSION IN FOUR-STATE BASIS

Description: Our earlier theoretical work on the relative muon capture between heavy and light fission fragments is extended by including 2p{sigma} states as well as 1s{sigma}. We calculate about 0.8% population of the 2p state in the heavy fragment with negligible change from our earlier two-state basis regarding the ls population of light and heavy fragments.
Date: May 1, 1981
Creator: Zhong-yu, Ma; Xi-zhen, Wu; Jing-shang, Zhang; Yi-zhong, Zhuo; Rasmussen, J.O.; Xi-zhen, Wu et al.
Partner: UNT Libraries Government Documents Department

SEARCH FOR QUARK EFFECTS IN THE d+{sup 4}He SYSTEM

Description: It has been suggested that bags containing more than three interacting quarks may be formed in high energy collisions; these states would appear as narrow reasonances in the inelastic channels. We have measured the inclusive cross section d+ {sup 4}He{yields}p+X at E{sub cm} =6.25 to 7.91 GeV in steps of 50 to 100 MeV to search for a eighteen quark bag resonance. Upper limits on the production cross section are presented.
Date: March 1, 1980
Creator: McClelland, J.B.; Carroll, J.B.; Igo, G.J.; Oostens, J.; Brochard, F.; Perez-Mendez, V. et al.
Partner: UNT Libraries Government Documents Department

FINITE PARTICLE NUMBER EFFECTS IN HIGH-ENERGY NUCLEAR COLLISIONS: IMPLICATIONS ON PION SPECTRA

Description: We study pion production from high energy nuclear collisions by means of a simple statistical model. The shapes of the observed spectra exclude that all pions result from freely decaying delta resonances. Rather, they have to participate in kinetic equilibration processes. Finite particle number effects are found to be very important: equilibration does not occur globally but rather in groups of only a few particles. The pion production rates cannot be explained in terms of a chemical equilibrium.
Date: May 1, 1980
Creator: Bohrmann, Steffen & Knoll, Jorn
Partner: UNT Libraries Government Documents Department

ONE- AND TWO-PROTON INCLUSIVE SPECTRA IN 800 MeV PROTON-NUCLEUS COLLISIONS AND THE MEAN FREE PATH OF PROTONS IN NUCLEI

Description: One- and two-proton inclusive spectra have been measured in collisions of 800 MeV protons with C, NaF, KCl, Cu, and Pb targets. The single proton inclusive yield increases monotonically with target mass, while the two-proton yield at {theta}{sub Lab}=± 40° associated with pp quasi-elastic scatterings shows a maximum at a mass number of about 50. A model calculation reproduces the observed target mass dependence with a mean free path of ~2.5 fm for 800 MeV protons inside the nucleus.
Date: October 1, 1980
Creator: Tanihata, I.; Nagamiya, S.; Schnetzer, S. & Steiner, H.
Partner: UNT Libraries Government Documents Department