VTechWorks Repository :: Browsing by Author "Blecher, Marvin"

Browsing by Author "Blecher, Marvin"

Now showing 1 - 19 of 19

An analysis of pion photoproduction
Li, Zhujun L. (Virginia Tech, 1992-04-05)
A partial-wave analysis of pion photoproduction data up to a photon lab energy of 1.8 GeV has been performed. Both energy-dependent and energy-independent solutions have been obtained. The energy-dependent parametrization incorporates the recently determined elastic pion nucleon scattering amplitudes in such a way as to satisfy unitarity and utilize the resonance structure contained in the pion nucleon elastic amplitudes. Starting from the energy-dependent solution, energy-independent partial-wave solutions are obtained at a set of energies from threshold to 1.8 GeV. The data base used in the analysis contains 11,911 data from the reactions. The predictions of our solution are compared with the experimental data and previous analyses. Suggestions are made for future experiments. A total of sixteen resonances exist in the energy range from threshold to 1.8 GeV. These resonance states are studied using our energy-independent solutions. Photon decay couplings to the sixteen resonances are extracted. These couplings are also compared with previous solutions and quark model predictions.
An analysis of pion-nucleon scattering
Ford, John Marshall (Virginia Polytechnic Institute and State University, 1988)
A phase-shift analysis of elastic pion-nucleon scattering data g from threshold to a pion kinetic energy of 1100 MeV was performed. The resulting partial-wave amplitudes were investigated in the complex energy plane, and the resonance states with their associated zeros and poles were determined. Particular emphasis was given on elucidating the nature of the P₁₁ partial wave. The phase-shift analysis consisted of both energy-independent and energy-dependent analyses. The energy dependent partial waves were parametrized as a coupled channel K-matrix whose elements are polynomials in energy plus an explicit pole term. A complete description of the investigation and the experimental data used are included as is a description of the theoretical models used for interpretation of the results.
Charged Pion Photoproduction Cross Section and Beam Asymmetry Measurement on HD
Meyer, Holger (Virginia Tech, 2002-08-08)
The charged pion production reactions d(gamma,pi⁺n), d(gamma,pi^-p), HD(gamma,pi⁺n)X were studied using linearly polarized gamma-rays with energies in the range from 260 MeV to 370 MeV at the Laser Electron Gamma Source (LEGS). A solid HD target was used in this experiment for the first time. The beam asymmetry data for the d(gamma,pi^-p) reaction significantly add to the previously available data. This gives new input to multipole analysis of pion production. A slight deviation from the beam asymmetry predicted for the free neutron is observed. The cross sections in the d(gamma,pi^-p) channel agree with previous measurements.
Classical and quantum gravity with Ashtekar variables
Soo, Chopin (Virginia Tech, 1992)
This thesis is a study of classical and quantum gravity with Ashtekar variables. The Ashtekar constraints are shown to capture the essence of the constraints and constraint algebra of General Relativity in four dimensions. A classification scheme of the solution space of the Ashtekar constraints is proposed and the corresponding physics is investigated. The manifestly covariant equations of motion for the Ashtekar variables are derived. Explicit examples are discussed and new classical solutions of General Relativity are constructed by exploiting the properties of the Ashtekar variables. Non-perturbative canonical quantization of the theory is performed. The ordering of the quantum constraints as well as the formal closure of the quantum constraint algebra are explored. A detailed Becchi-Rouet-Stora-Tyutin (BRST) analysis of the theory is given. The results demonstrate explicitly that in quantum gravity, fluctuations in topology can occur and there are strong evidences of phases in the theory. There is a phase which is described by a topological quantum field theory (TQFT) of the Donaldson-Witten type and an Abelian antiinstanton phase wherein self-interactions of the gravitational fields produce symmetry breaking from SO(3) to U(1). The full theory is much richer and includes fluctuations which bring the system out of the various restricted sectors while preserving diffeomorphism invariance. Invariants of the quantum theory with are constructed through BRST descents. They provide a clear and systematic characterization of non-local observables in quantum gravity, and can yield further differential invariants of four-manifolds.
Differential algebraic methods for obtaining approximate numerical solutions to the Hamilton-Jacobi equation
Pusch, Gordon D. (Virginia Tech, 1990)
I present two differential-algebraic (DA) methods for approximately solving the Hamilton- Jacobi (HJ) equation. I use the “automatic differentiation” property of DA to convert the nonlinear partial-differential HJ equation into a initial-value problem for a DA-valued first-order ordinary differential equation (ODE), the “HJ/DA equation”. The solution of either form of the HJ/DA equation is equivalent to a perturbative expansion of Hamilton’s principle function about some reference trajectory (RT) through the system. The HJ/DA method also extracts the equations of motion for the RT itself. Hamilton’s principle function generates the canonical transformation, or mapping, between the initial and final state of every trajectory through the system. Since the map is represented by a generating function, it must automatically be symplectic, even in the presence of round-off error. The DA-valued ODE produced by either form of HJ/DA is equivalent tc a hierarchically-ordered system of real-valued ODEs without “feedback” terms; therefore the hierarchy may be truncated at any (arbitrarily high) order without loss of self consistency. The HJ/DA equation may be numerically integrated using standard algorithms, if all mathematical operations are done in DA. I show that the norm of the DA-valued part of the solution is bounded by linear growth. The generating function may be used to track either particles or the moments of a particle distribution through the system. In the first method, all information about the perturbative dynamics is contained in the DA-valued generating function. I numerically integrate the HJ/DA equation, with the identity as the initial generating function. A difficulty with this approach is that not all canonical transformations can be represented by the class of generating functions connected to the identity; one finds that with the required initial conditions, the generating function becomes singular near caustics or foci. One may continue integrating through a caustic by using a Legendre transformation to obtain a new (but equivalent) generating function which is singular near the identity, but nonsingular near the caustic. However the Legendre transformation is a numerically costly procedure, so one would not want to do this often. This approach is therefore not practical for systems producing periodic motions, because one must perform a Legendre transformation four times per period. The second method avoids the caustic problem by representing only the nonlinear part of the dynamics by a generating function. The linearized dynamics is treated separately via matrix techniques. Since the nonlinear part of the dynamics may always be represented by a near-identity transformation, no problem occurs when passing through caustics. I successfully verify the HJ/DA method by applying it to three problems which can be solved in closed form. Finally, I demonstrate the method’s utility by using it to optimize the length of a lithium lens for minimum beam divergence via the moment-tracking technique.
DNA Electronics
Zwolak, Michael Philip (Virginia Tech, 2003-05-07)
DNA is a potential component in molecular electronics. To explore this end, there has been an incredible amount of research on how well DNA conducts and by what mechanism. There has also been a tremendous amount of research to find new uses for it in nanoscale electronics. DNA's self-assembly and recognition properties have found a unique place in this area. We predict, using a tight-binding model, that spin-dependent transport can be observed in short DNA molecules sandwiched between ferromagnetic contacts. In particular, we show that a DNA spin-valve can be realized with magnetoresistance values of as much as 26% for Ni and 16% for Fe contacts. Spin-dependent transport can broaden the possible applications of DNA as a component in molecular electronics and shed new light into the transport properties of this important biological molecule.
Fermion Quantum Field Theory In Black-hole Spacetimes
Ahmad, Syed Alwi B. (Virginia Tech, 1997-04-18)
The need to construct a fermion quantum field theory in black-hole spacetimes is an acute one. The study of gravitational collapse necessitates the need of such. In this dissertation, we construct the theory of free fermions living on the static Schwarzschild black-hole and the rotating Kerr black-hole. The construction capitalises upon the fact that both black-holes are stationary axisymmetric solutions to Einstein's equation. A factorisability ansatz is developed whereby simple quantum modes can be found, for such stationary spacetimes with azimuthal symmetry. These modes are then employed for the purposes of a canonical quantisation of the corresponding fermionic theory. At the same time, we suggest that it may be impossible to extend a quantum field theory continuously across an event horizon. This split of a quantum field theory ensures the thermal character of the Hawking radiation. In our case, we compute and prove that the spectrum of neutrinos emitted from a black-hole via the Hawking process is indeed thermal. We also study fermion scattering amplitudes off the Schwarzschild black-hole.
Gamma Veto Detectors in the KOPIO Experiment
Graham, Nicholas L. (Virginia Tech, 2006-02-05)
KOPIO is an experiment designed to search for the CP-symmetry-violating reaction K_L⁰ → π⁰νν̅. Measurement of the branching ratio of this reaction, depending on the accuracy of the measurement, could be the most precise measurement of the CP-violation parameters of the Standard Model to date. The K_L⁰ → π⁰νν̅ reaction is exceedingly rare, with an expected branching ratio of (2.6 ± 1.2) ·10⁻¹¹ . The rareness of this reaction means two things: 1) that we need prodigious numbers of kaons, and 2) that a multitude of "improper" decays will have to be screened out by means of a veto detector system, part of which is being designed here at Virginia Tech. This detector must be able to detect the passage of daughters of the undesired decay reactions (charged particles and gammas). It must be operational inside a magnetic field, and must have signal timing fast enough to accommodate the rate at which these decays occur. A detector consisting of alternating layers of scintillator and lead, with wavelength-shifting fibers embedded in the scintillator, provides the characteristics sought after. This paper presents methodology used in design and construction of this detector, as well as results of signal property tests, using both cosmic rays and gammas as event triggers. Also included is a discussion on transporting the detector signal outside of the magnetic field so it can be read by photomultiplier tubes resting outside of the sweeping magnet.
Investigation of the optical properties of Bi₂Sr₂Ca_n-1Cu_nO_y (n=1,2) by transmission electron energy loss spectroscopy
Wang, Yun-Yu (Virginia Tech, 1990)
A high energy resolution transmission electron energy loss spectrometer was reassembled for this research project. The vacuum system, electron optical lenses, electronic control elements, and high voltage system were reconditioned. A CAMAC interface system was installed into the spectrometer, and a data collecting software package was developed which included a direct convolution method for removing the contributions of multiple scattering from the data. The spectrometer is running very well. Samples can be changed routinely without disturbing the performance of the spectrometer. The research conducted for this thesis was an investigation of the optical properties of the high temperature superconductors of Bi₂Sr₂Ca_{n - 1}Cu_nO₃(n = 1,2) by transmission electron energy loss spectroscopy. A thin film of Bi₂Sr₂CaCu₂O₈ was prepared by the flux method. A single crystal of Bi₂Sr₂CuO₆ also was grown from which a self-supporting thin film was prepared. The energy loss spectra of Bi₂Sr₂CaCu₂O₈ and Bi₂Sr₂CuO₆ materials were investigated, and the dielectric functions of these materials were derived by Kramers-Kronig analysis. A broad excitation centered at 2.7eV was identified as associated with the Cu — O₂ layer by comparing the spectrum of Bi₂Sr₂CaCu₂O₈ with that of Bi₂Sr₂CuO₆. A pseudo gap of 1.2eV in the spectrum of Bi₂Sr₂CuO₆ suggests that the one electron approximation for states derived from the hybridization of O 2p_σ and Cu3d_{x² - y²} orbital might not be valid. Two excitations at 3.6eV and 4.6eV were observed in both spectra. Comparing the spectrum of Bi₂Sr₂CaCu₂O₈ with that of Bi₂Sr₂CuO₆ suggests that the 3.6eV excitation is associated with the Bi — O layer. It was concluded that the 3.6eV and 4.6eV excitation are a spin-orbit doublet derived from the atomic bismuth 6p level. This identification is based on a comparison of Bi core level excitations from electron energy loss spectroscopy with X-ray photoemission measurements. A simplified atomic energy level picture of Bi in Bi₂Sr₂Ca_{n - 1}Cu_nO₃(n = 1, 2) is presented. A 1.0eV excitation in the energy loss spectrum of Bi₂Sr₂CaCu₂O₈ was observed, and its dispersion relationship with the momentum transfer q is presented. A Drude model was used to describe this controversial excitation.
Measurement of the Ratio of Charged and Neutral 𝐵 Mesons in Υ (4𝑆) Events via Partial Reconstruction of the Semileptonic Decays 𝛣̅⁰⟶𝐷^∗⁺ℓ⁻_𝜈̅ℓ and 𝛣̅⁻⟶𝐷^∗⁰ℓ_𝜈̅ℓ
Godang, Romulus (Virginia Tech, 2000-08-23)
The decays, and are studied using data collected at the CLEO II detector at the Cornell Electron Storage Ring. Both decays are identified using a partial reconstruction method where the D^* is detected only through a pion daughter from the decay . Because of the similarities in the analyses of the two modes, the ratio of the rates is measured in a way that is independent of the decay model, limited mainly by the uncertainty in the relative efficiency for detecting neutral and charged pions. This ratio is equivalent to the ratio of the product of production fraction and lifetime for charged and neutral B mesons, . It is combined with measurements of the lifetime ratio to obtain the ratio of charged and neutral B meson production at the Y(4S) resonance, .
Parity-Violating Elastic Electron Nucleon Scattering: Measurement of the Strange Quark Content of the Nucleon and Towards a Measurement of the Weak Charge of the Proton
Mammei, Juliette Mae (Virginia Tech, 2010-04-30)
The experiments discussed in this thesis exploit parity violation in elastic electron proton scattering in order to measure properties of the nucleon. Both experiments make use of the high quality, highly polarized electron beam available at Thomas Jefferson National Accelerator Facility. Q_weak will measure the weak mixing angle, sin²θ_W, via a measurement of the weak charge of the proton, at a four-momentum transfer, Q² ~ 0.026 GeV²/c². The precision of this measurement gives Q_weak access to new physics at the scale of 2.3 TeV, making it a test of the standard model. The G⁰ experimental program provides the fully separated contributions of the strange quark to the charge and magnetization distributions of the nucleon at two different values of four-momentum transfer, Q² ~ 0.22 and 0.63 GeV²/c². The measurement of the strange quark content of the proton in the G⁰ experimental program and other parity-violating electron scattering experiments provides a measurement of the hadronic contribution to the asymmetry in Q_weak. In addition, G⁰ was able to measure the parity-conserving beam normal single spin asymmetries that provide a measurement of the imaginary part of two photon exchange. The measurement of this asymmetry is necessary to understand the systematic contribution to measurements of parity-violating asymmetries, but it is also an important physics result. Recent theoretical work has shown that higher order radiative effects, such as two photon exchange, may be able to explain discrepancies between experiments which measure the ratio of the electric and magnetic form factors of the proton. The measurement of the transverse or beam normal single spin asymmetries provides a benchmark for theories that estimate the size of radiative corrections that are important for precision electroweak scattering experiments such as those described in this thesis. The results of the measurement of the transverse asymmetries at backward angles in G⁰ are presented at the two values of Q² ~ 0.22 and 0.63 GeV²/c² for hydrogen. Results for deuterium, which can provide the first measurements of the beam normal single spin asymmetries on the neutron, are also presented.
Positive and negative pion elastic scattering on [58]Ni, [60]Ni, and [64]Ni at 50 MeV and 65 MeV
Fick, Brian Edwin (Virginia Polytechnic Institute and State University, 1985)
Elastic scattering data was successfully taken using the new "Clamshell" spectrometer. Angular distributions of elastic differential cross sections were obtained at 50 MeV and 65 MeV using positive and negative pions scattered from ⁵⁶Ni, ⁶⁰Ni, and ⁶⁴Ni. The data were compared to predictions made using the MSU optical potential, The π⁺ data agreed fairly well with the predictions at both 50 MeV and 65 MeV while the corresponding π⁻ data significantly disagreed with the predictions. The absorption parameters in the MSU potential were varied in an attempt to fit the data. A suitable fit was achieved for both π⁺ and π⁻ data at 50 MeV and 65 MeV. The real part of the p-wave absorption parameter was well determined but showed two distinct values for π⁺ and π⁻ indicating that there is a separate potential for π⁺ and π⁻ or that the absorption part of the potential is inadequately formulated.
Proton Compton scattering with polarized γ rays
Zhao, Xi-jun (Virginia Tech, 1993)
Proton Compton scattering has been studied from 220 to 330 MeV at 90 degree center of mass scattering angle with the polarized photon beam at LEGS. Compton scattering is an important probe of the nucleon structure and its excited states. Polarization degrees of freedom reveal more information than unpolarized observables. This experiment measured, for the first time, the polarized cross sections of proton Compton scattering up to the Δ resonance. The parallel and perpendicular cross sections were measured at the same time. All the photons were tagged so that the energy dependent systematic errors are small. The measured unpolarized cross section is above the lower bound from unitary at all energies. The cross section asymmetry is obtained as a function of energy for the first time. The unpolarized cross section is compared with previous data and with calculations from the fixed-t dispersion model, the isobar model and the finite energy dispersion model. Although all these calculations agree fairly well with unpolarized cross section data, the photon asymmetry data show that the isobar model contains serious defects. The ratio of polarized cross sections, dσ_⫫/dσ_⟂, is compared with a model independent result. The results from the present experiment can be used in the calculation of the E2/M1 ratio in the N — Δ transition, which is an important signature of the tensor interaction between quarks.
Radiative muon capture on nuclear targets
Serna, Alvaro (Virginia Tech, 1991)
A large acceptance pair spectrometer to detect photons from the radiative muon capture (RMC) process was built. The spectrometer was used to measure the RMC branching ratio for AI, Si, Ca, Mo, Sn and Pb. Two recent theoretical models were used to extract the RMC branching ratio in Ca. The experin1ental result is in good agreement with the world average value, but yields a value for the pseudoscalar coupling constant, gp, which is lower than the Goldberger-Treiman PCAC prediction. In the absence of a theoretical model to predict the R11C rates for Al and 5i, only the branching ratios for these targets are reported. For Mo, 5n, and Pb, the branching ratios found were consistent with the Fermi gas n10del for which a nill contribution from the pseudoscalar coupling was assumed. Good agreement was found between the experimental results and what is predicted fron1 using the simple, closure approximation. The RMC world data indicates a close connection between the branching ratios and Q, where Q is the ratio between the difference and the sum of neutrons and protons for any element, (Q = ~Z~~J). It is suggested that future experiments study different isotopes to isolate the Z and the Q dependence of the R11C rates. This experiment also served as a test ground for the RMC experin1ent in liquid hydrogen which is now in progress at TRIUMF.
The Scattering of H-alpha Emission Associated with the Rosette Nebula in the Monoceros Region Studied Using Polarimetry
Topasna, Gregory A. (Virginia Tech, 1999-05-07)
Polarimetric CCD images of HII regions were obtained using a rotating polarizer device designed, built, and used in conjunction with the Spectral Line Imaging Camera (SLIC) at Virginia Tech's Martin Observatory in Giles County, Virginia. The SLIC uses a narrow bandpass interference filter coupled with a 58 mm camera lens and cryogenically cooled CCD camera to image diffuse, extended H-alpha emission over a 10° angular extent. A rotating polarizer device was placed in front of the H-alpha filter with images recorded at every 45° with respect to a fiducial setting. Stoke's parameters and were obtained and polarization maps of selected HII regions were created. Maps of the Monoceros supernova remnant and the Rosette Nebula (NGC 2237-9) were made in an attempt to detect polarization by selective extinction in H light. While this was not detected, polarization by scattering in a dust shell around the Rosette Nebula (NGC 2237-9) was observed. Scattered continuum light from the central star cluster NGC 2244 in the H-alpha bandpass was ruled out. Using Celnik's (1985) map of extinction across the Rosette Nebula at the H wavelength, coupled with Serkowski's empirical relationship between maximum polarization and color excess, it was shown that the maximum degree of polarization seen in the Rosette Nebula should be no more than 3% to 4%. The polarization observed in this project reaches values as high as 10%. It was found that a correlation exists between the H-alpha intensity and infrared emission by dust grains in all four IRAS waveband images in the suspected scattering region of the Rosette Nebula. A radial comparison between [SII] images and H-alpha images in the region of high polarization showed that the H-alpha intensity in that region is dominated by scattered H-alpha light from the Rosette Nebula. A single scattering model was constructed in an effort to predict the observed polarization. The model used parameters based on 21 cm observations by Kuchar and Bania (1993) of the HI shell which surrounds the HII region of the Rosette Nebula. The single scattering model can not accurately predict the degree of polarization. It was concluded that a multiple scattering model is required. A spatial comparison of the 12 m emission with the degree of polarization strongly suggested that multiple scattering is important in describing the observed radial behavior of polarization. Polarization images of regions in Cygnus were obtained. A polarization map of the North America Nebula (NGC 7000) and surroundings reveals a large amount of polarization. The map reveals that scattering of H-alpha light from the North America Nebula is the most likely cause of polarization in these images. From the analysis in this thesis, I conclude that in the northwest quadrant, at radial distances greater than 40 from the center of the Rosette Nebula, the observed H-alpha intensity is due to scattered H light from the nebula itself. This implies that, in H-alpha , the Rosette Nebula appears slightly larger than it actually is. With evidence of polarization by scattered H supported by the polarization map of the North America Nebula (NGC 7000), it is concluded that other HII regions may very well appear larger in H-alpha than they actually are. Thus, scattered H-alpha light may account for a small part of the more extended warm ionized medium as well.
Search for evidence of fermi surface nesting in Bi₂Sr₂Ca₁Cu₂O₈
Potter, Charles D. (Virginia Tech, 1992)
The electron energy loss spectrometer at Virginia Tech has been modified with new momentum deflectors and various other hardware improvements. In addition to some hardware changes all the software to run the spectrometer and analyze the data has been rewritten. It was suggested by Tsuei (1990) that a nested Fermi surface could be used to explain both the fact that these materials have high superconducting transition temperatures and have linear relaxation rates. It was suggested in that same paper that EELS might be able to confirm the presence of Fermi surface nesting. We have attempted to use transmission electron energy loss spectroscopy in a novel way to search for evidence of Fermi surface nesting in the high T_c superconductor Bi₂Sr₂Ca₁Cu₂O₈. High quality single crystal samples were obtained and thinned for use in the EELS. Data was taken at low energy (<1.0eV) and momentum was scanned along three different momentum transfer directions for |q| =0.0 to 3.0Å⁻¹. The data was scaled to be Im(-1/ε). A calculation of Im(-1/ε) was performed using a tight binding model and it was found that the features associated with the Fermi surface (from this TB calculation) were too small to be seen in our spectra. We interpret this problem to be associated with the presence of thermal diffuse scattering.
Search for massive neutrinos in the decay pi -> e nu
Aoki, M.; Blecher, Marvin; Bryman, D. A.; Chen, S.; Ding, M.; Doria, L.; Gumplinger, P.; Hurst, C.; Hussein, A.; Igarashi, Y.; Ito, N.; Kettell, S. H.; Kurchaninov, L.; Littenberg, L.; Malbrunot, C.; Numao, T.; Poutissou, R.; Sher, A.; Sullivan, T.; Vavilov, D.; Yamada, K.; Yoshida, M.; Pienu Collaboration (American Physical Society, 2011-09-06)
Evidence of massive neutrinos in the pi(+) -> e(+)nu decay spectrum was sought with the background pi(+) -> mu(+) -> e(+) decay chain highly suppressed. Upper limits (90% C. L.) on the neutrino mixing matrix element vertical bar U(ei)vertical bar(2) in the neutrino mass region 60-129 MeV/c(2) were set at the level of 10(-8).
Search for the rare decay of the muon into a positron and a photon
Zhang, Yiding (Virginia Tech, 1995)
This dissertation examines some of the more subjective aspects of individuals' experiences of isolation within the context of racialized and gendered work organizations. This research develops two constructs--institutional and social isolation--and attempts to ascertain the extent to which racial and gender groups experience isolation similarly. Other attitudes, such as intent to turnover, affective commitment, and alienation, are analyzed with respect to feelings of isolation for these groups. Finally, because current thinking has advocated the use of organizational interventions, such as mentoring programs, to ameliorate individuals' feelings of separateness within the organization, the relationship of mentoring to the aforementioned constructs was examined for its usefulness in understanding similarities and differences between these groups. This research extends previous work by providing support for new conceptualizations of social isolation and isolation. It extends work done by Nkomio and Cox (1990) and others who found that individuals who had achieved some objective measures of success in organizations, still did not feel, subjectively, as if they were a part of the organization. Thus, the use of these isolation constructs will expand our knowledge of organizational processes in examining groups based on gender and race/ethnicity. The results indicate that isolation docs exist on two dimensions: institutional isolation and social isolation. Asian-Americans have higher levels of institutional isolation, and African-Americans have higher levels of social isolation than any other group. Females experience higher levels of social isolation--but not institutional isolation--than males. There are some differences when race and gender are examined simultaneously in levels of experienced institutional and social isolation. Younger faculty feel more institutionally and socially isolated than older faculty. There is no significant effect of the presence of mentoring on institutional or social isolation; nor is there differential access to mentoring relationships by race. However, females enter mentoring relationships in greater proportions than males. There are also effects from cross-racial mentoring relationships. Finally, there are no significant differences, by race or gender, in the levels of affective organizational commitment or intent to turnover.
Study of pion production from the two-nucleon system within a relativistic unitary model
Sammarruca-Machleidt, Francesca (Virginia Polytechnic Institute and State University, 1988)
In this work, we explore the NN → πNN reaction within a relativistic model, consistent with two- and three-body unitarity, for the NN and πNN coupled systems. The model is based on effective hadronic interactions. After describing the theoretical input, we compare the predicted NN phase parameters with the phase shift analysis. Our predictions for the NN → πNN spin observables are compared with the available data and with predictions from other models. A clear model dependence is observed. We also examine systematically the dependence of these spin observables on various components of the dynamical input. We identify and isolate some problems related to the present approach and we point out possible directions for future research.

Browsing by Author "Blecher, Marvin"

Results Per Page

Sort Options