Stephen Cotanch | North Carolina State University (original) (raw)
Papers by Stephen Cotanch
This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government Neither the United States Governmtnt nor any agency thereof, nor any of their anpioy#s makes any warranty, express or implied, or assumes any legal liabity or responsibility for the accuracy, completeness, or usefulness of any infomation, apparatus, product, or proass discios4 or rrpresents that its usc would not infringe privately owned rights. Rcfcrcacc henin to any specific commercial product, proass, or service by trade name, trademark, inanufacturcr, or otherwise does not n#.+ssarily constitute or imply its endorsux~cnt, m mmendrtion. or favoring by tbc United States Government or any agency thereof. The views and opinions of authors c x p d herein do not llcQsJani 'y state or reflect those of the United States Government or any agency thenof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.
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](This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom-_1 mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the-United States Government or any agency thereof.
Physical Review Letters, Mar 1, 2006
We report an odderon Regge trajectory emerging from a field theoretical Coulomb gauge QCD model f... more We report an odderon Regge trajectory emerging from a field theoretical Coulomb gauge QCD model for the odd signature J P C (P = C =-1) glueball states (oddballs). The trajectory intercept is clearly smaller than the pomeron and even the ω trajectory's intercept which provides an explanation for the nonobservation of the odderon in high energy scattering data. To further support this result we compare to glueball lattice data and also perform calculations with an alternative model based upon an exact Hamiltonian diagonalization for three constituent gluons.
arXiv: High Energy Physics - Phenomenology, 2006
We analyze the f0(1810) state recently reported by the BES collaboration in a radiative decay of ... more We analyze the f0(1810) state recently reported by the BES collaboration in a radiative decay of the J/psi yielding a new phi\omega spectrum, and contrast it against DM2 data and glueball theory. Clearly the DM2 omega\omega data does not allow for a flavor-symmetric decaying particle. A rescattering mechanism from Kx-anti Kx is proposed that could account for the flavor asymmetry. We conclude that this new scalar meson is a solid glueball candidate and deserves further experimental investigation, especially in Kx-anti Kx channels. Some remarks about decays of positive C-parity charmonia strengthen our case. Finally we comment on other, seemingly less likely or less attractive, possible assignments for this state.
Bulletin of the American Physical Society, 1992
The electromagnetic properties of a relativistic constituent-quark model of light nonstrange and ... more The electromagnetic properties of a relativistic constituent-quark model of light nonstrange and strange mesons are investigated within the framework of light-front Hamiltonian dynamics. The authors demonstrate that the Poincare invariant quark model of the pion and kaon can give charge form factors in agreement with all available data. The relativistic features of the model are essential for the result. The radial confinement scale is much smaller than the charge radius due to the sizable effect from the spin-orbit coupling in the meson system.
Using their previously developed crossing and duality constrained model for kaon photo/electropro... more Using their previously developed crossing and duality constrained model for kaon photo/electroproduction and radiative capture, the authors make predictions for the reactions p(K{sup {minus}}, e{sup +}e{sup {minus}})Y for Y = {Lambda}, {Sigma}{sup o}, and {Lambda}(1405). The K{sup {minus}} induced pair production reactions offer an opportunity to study kaon and nucleon form factors in the time-like region. Very large resonance effects are observed when the time-like 4-momentum transfer of the photon (q{sup 2} > O) approaches a vector meson pole. Due to the nearly equal total mass energy in the final and initial states, the {rho}, {omega}, and {phi} dominance regions are all kinematically accessible, in contrast to annihilation processes (eg. p{bar p} {leftrightarrow} e{sup +}e{sup {minus}}, K{sup +}K{sup {minus}} {leftrightarrow} e{sup +}e{sup {minus}}).
AIP Conference Proceedings, 1981
ABSTRACT
Physical Review Letters, 1973
Discrepancies between observed ratios of d, 3 He and d f t yields populating analog states in 18 ... more Discrepancies between observed ratios of d, 3 He and d f t yields populating analog states in 18 0 and 18 F and ratios calculated by standard distorted-wave theory, which were thought to provide evidence for a charge-dependent nuclear interaction, are resolved by extending the conventional theory to include both an explicit charge-exchange channel in the continuum and form factors generated from a microscopic analysis.
Physical Review Letters, 1979
A Lane-model analysis of the 9 Be+nucleon system has provided a detailed description of both cros... more A Lane-model analysis of the 9 Be+nucleon system has provided a detailed description of both cross-section and polarization data for (p,p) elastic, (n,n) elastic, and (p,n) quasielastic scattering over a range of energies. Emphasis is placed on consistency in isospin conservation, data-set completeness, and multichannel constraints. Results favor a symmetry potential which is energy dependent with volume and surface form factors for the real and imaginary wells, respectively. A symmetry spin-orbit (T-d)^' T) interaction was found to be unnecessary.
Nuclear Physics A, 1993
A new type of high resolution pair spectrometer for medium energy photons has been used for studi... more A new type of high resolution pair spectrometer for medium energy photons has been used for studies of the exclusive (P,7) and (p,e"e-) reactions on light nuclei in the energy region 100 to 200 MeV. From the current experiments we present angular distributions of the differential cross section for transitions to the ground state and first three excited states in 12C. The distributions from the ground state and first excited state are compared with predictions from a microscopic continuum shell model calculation which uses a realistic finite-range effective interaction with tensor components. Based on preliminary data, the salient features of the (P, 7) reaction on 12C and the (p,e÷e-) reaction on lib are also discussed.
Physics Letters B, 2013
The spectrum of tetraquark states with hidden charm is studied within an effective Coulomb gauge ... more The spectrum of tetraquark states with hidden charm is studied within an effective Coulomb gauge Hamiltonian approach. Of the four independent color schemes, two are investigated, the (qc) 1 (cq) 1 singlet-singlet (molecule) and the (qc) 3 (qc) 3 triplettriplet (diquark), for selected J P C states using a variational method. The predicted masses of triplet-triplet tetraquarks are roughly a GeV heavier than the singletsinglet states. There is also an interesting flavor dependence with (qq) 1 (cc 1) states about half a GeV lighter than (qc) 1 (qc) 1. The lightest 1 ++ and 1 −− predictions are in agreement with the observed X(3872) and Y (4008) masses suggesting they are molecules with ωJ/ψ and ηh c , rather than D * D * and DD, type structure, respectively. Similarly, the lightest isovector 1 ++ molecule , having a ρJ/ψ flavor composition, has mass near the recently observed charged Z c (3900) value. These flavor configurations are consistent with observed X, Y and Z c decays to ππJ/ψ.
Few-Body Systems, 1995
Using a relativistic quark model approach that successfully described flavored meson systems, ele... more Using a relativistic quark model approach that successfully described flavored meson systems, electromagnetic form factors and structure functions are calculated for the low mass baryons. The observed proton, neutron and lambda moments, rms radii and form factors are all reproduced and predictions are made for other baryon observables which will be measured at CEBAF. Most significantly, by properly including the quark potential energy the long standing neutron to proton structure function ratio anomaly for x ~ 1 has been resolved.
Physics Letters B, 1992
A new type of high resolution pair spectrometer for medium energy photons has been used for studi... more A new type of high resolution pair spectrometer for medium energy photons has been used for studies of the exclusive (p, ~/) reaction on ~ ~B at 98 MeV. Angular distributions of the differential cross section for transitions to the ground state and first excited state in J2C are presented. The distributions show good agreement with predictions from a microscopic continuum shell model calculation which uses a realistic finite-range effective interaction with tensor components.
Physical Review Letters, 1976
ABSTRACT
Physical Review D, 1999
Extending previous QCD Hamiltonian studies, we present a new renormalization procedure which gene... more Extending previous QCD Hamiltonian studies, we present a new renormalization procedure which generates an effective Hamiltonian for the gluon sector. The formulation is in the Coulomb gauge where the QCD Hamiltonian is renormalizable and the Gribov problem can be resolved. We utilize elements of the G lazek and Wilson regularization method but now introduce a continuous cutoff procedure which eliminates non-local counterterms. The effective Hamiltonian is then derived to second order in the strong coupling constant. The resulting renormalized Hamiltonian provides a realistic starting point for approximate many-body calculations of hadronic properties for systems with explicit gluon degrees of freedom.
Physical Review C, 1976
The direct reaction A(a, b)B is described by exactly solving the Schrodinger equation for a few-b... more The direct reaction A(a, b)B is described by exactly solving the Schrodinger equation for a few-body Hamiltonian within a restricted model space. The model space allows for coupling to rearrangement channels by including basis vectors classified according to different mass partitions. The nonorthogonality of basis vectors that correspond to different mass partitions is investigated in detail. A surface approximation is developed to understand the magnitudes of multistep amplitudes produced by channel coupling to rearranged partitions. The surface approximation uses a separable Green's function approximation to the multistep series, and gives a convenient closed-form expression. Finite-range coupled-channels calculations are presented for the reactions (d, d), (d, p), and (p, p) on oxygen and zirconium targets, and for (' 0, ' 0), (' 0,"C), and ("C,"C) on silicon and sulfur targets. To assess higher-order effects, these results are consistently compared with lowest-order results using folded distorting potentials. The calculations indicate that the effects of nonorthogonality are small for these reactions, but the light-ion reactions showed much larger effects. Theoretical explanations of the behavior of nonorthogonality and channel-coupling effects are given, and lead to criteria for predicting when such effects may be important. Channel-coupling effects are expected to be important whenever the distorted-wave Born-approximation transfer amplitude is unusually sensitive to the intermediate channel optical potential. Nonorthogonality efFects are roughly proportional to channel-coupling effects, but are much smaller than coupling effects except when a small mass is transferred between two large masses.
Physical Review C, 1978
ABSTRACT
This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government Neither the United States Governmtnt nor any agency thereof, nor any of their anpioy#s makes any warranty, express or implied, or assumes any legal liabity or responsibility for the accuracy, completeness, or usefulness of any infomation, apparatus, product, or proass discios4 or rrpresents that its usc would not infringe privately owned rights. Rcfcrcacc henin to any specific commercial product, proass, or service by trade name, trademark, inanufacturcr, or otherwise does not n#.+ssarily constitute or imply its endorsux~cnt, m mmendrtion. or favoring by tbc United States Government or any agency thereof. The views and opinions of authors c x p d herein do not llcQsJani 'y state or reflect those of the United States Government or any agency thenof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.
This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom-_1 mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the-United States Government or any agency thereof.
Physical Review Letters, Mar 1, 2006
We report an odderon Regge trajectory emerging from a field theoretical Coulomb gauge QCD model f... more We report an odderon Regge trajectory emerging from a field theoretical Coulomb gauge QCD model for the odd signature J P C (P = C =-1) glueball states (oddballs). The trajectory intercept is clearly smaller than the pomeron and even the ω trajectory's intercept which provides an explanation for the nonobservation of the odderon in high energy scattering data. To further support this result we compare to glueball lattice data and also perform calculations with an alternative model based upon an exact Hamiltonian diagonalization for three constituent gluons.
arXiv: High Energy Physics - Phenomenology, 2006
We analyze the f0(1810) state recently reported by the BES collaboration in a radiative decay of ... more We analyze the f0(1810) state recently reported by the BES collaboration in a radiative decay of the J/psi yielding a new phi\omega spectrum, and contrast it against DM2 data and glueball theory. Clearly the DM2 omega\omega data does not allow for a flavor-symmetric decaying particle. A rescattering mechanism from Kx-anti Kx is proposed that could account for the flavor asymmetry. We conclude that this new scalar meson is a solid glueball candidate and deserves further experimental investigation, especially in Kx-anti Kx channels. Some remarks about decays of positive C-parity charmonia strengthen our case. Finally we comment on other, seemingly less likely or less attractive, possible assignments for this state.
Bulletin of the American Physical Society, 1992
The electromagnetic properties of a relativistic constituent-quark model of light nonstrange and ... more The electromagnetic properties of a relativistic constituent-quark model of light nonstrange and strange mesons are investigated within the framework of light-front Hamiltonian dynamics. The authors demonstrate that the Poincare invariant quark model of the pion and kaon can give charge form factors in agreement with all available data. The relativistic features of the model are essential for the result. The radial confinement scale is much smaller than the charge radius due to the sizable effect from the spin-orbit coupling in the meson system.
Using their previously developed crossing and duality constrained model for kaon photo/electropro... more Using their previously developed crossing and duality constrained model for kaon photo/electroproduction and radiative capture, the authors make predictions for the reactions p(K{sup {minus}}, e{sup +}e{sup {minus}})Y for Y = {Lambda}, {Sigma}{sup o}, and {Lambda}(1405). The K{sup {minus}} induced pair production reactions offer an opportunity to study kaon and nucleon form factors in the time-like region. Very large resonance effects are observed when the time-like 4-momentum transfer of the photon (q{sup 2} > O) approaches a vector meson pole. Due to the nearly equal total mass energy in the final and initial states, the {rho}, {omega}, and {phi} dominance regions are all kinematically accessible, in contrast to annihilation processes (eg. p{bar p} {leftrightarrow} e{sup +}e{sup {minus}}, K{sup +}K{sup {minus}} {leftrightarrow} e{sup +}e{sup {minus}}).
AIP Conference Proceedings, 1981
ABSTRACT
Physical Review Letters, 1973
Discrepancies between observed ratios of d, 3 He and d f t yields populating analog states in 18 ... more Discrepancies between observed ratios of d, 3 He and d f t yields populating analog states in 18 0 and 18 F and ratios calculated by standard distorted-wave theory, which were thought to provide evidence for a charge-dependent nuclear interaction, are resolved by extending the conventional theory to include both an explicit charge-exchange channel in the continuum and form factors generated from a microscopic analysis.
Physical Review Letters, 1979
A Lane-model analysis of the 9 Be+nucleon system has provided a detailed description of both cros... more A Lane-model analysis of the 9 Be+nucleon system has provided a detailed description of both cross-section and polarization data for (p,p) elastic, (n,n) elastic, and (p,n) quasielastic scattering over a range of energies. Emphasis is placed on consistency in isospin conservation, data-set completeness, and multichannel constraints. Results favor a symmetry potential which is energy dependent with volume and surface form factors for the real and imaginary wells, respectively. A symmetry spin-orbit (T-d)^' T) interaction was found to be unnecessary.
Nuclear Physics A, 1993
A new type of high resolution pair spectrometer for medium energy photons has been used for studi... more A new type of high resolution pair spectrometer for medium energy photons has been used for studies of the exclusive (P,7) and (p,e"e-) reactions on light nuclei in the energy region 100 to 200 MeV. From the current experiments we present angular distributions of the differential cross section for transitions to the ground state and first three excited states in 12C. The distributions from the ground state and first excited state are compared with predictions from a microscopic continuum shell model calculation which uses a realistic finite-range effective interaction with tensor components. Based on preliminary data, the salient features of the (P, 7) reaction on 12C and the (p,e÷e-) reaction on lib are also discussed.
Physics Letters B, 2013
The spectrum of tetraquark states with hidden charm is studied within an effective Coulomb gauge ... more The spectrum of tetraquark states with hidden charm is studied within an effective Coulomb gauge Hamiltonian approach. Of the four independent color schemes, two are investigated, the (qc) 1 (cq) 1 singlet-singlet (molecule) and the (qc) 3 (qc) 3 triplettriplet (diquark), for selected J P C states using a variational method. The predicted masses of triplet-triplet tetraquarks are roughly a GeV heavier than the singletsinglet states. There is also an interesting flavor dependence with (qq) 1 (cc 1) states about half a GeV lighter than (qc) 1 (qc) 1. The lightest 1 ++ and 1 −− predictions are in agreement with the observed X(3872) and Y (4008) masses suggesting they are molecules with ωJ/ψ and ηh c , rather than D * D * and DD, type structure, respectively. Similarly, the lightest isovector 1 ++ molecule , having a ρJ/ψ flavor composition, has mass near the recently observed charged Z c (3900) value. These flavor configurations are consistent with observed X, Y and Z c decays to ππJ/ψ.
Few-Body Systems, 1995
Using a relativistic quark model approach that successfully described flavored meson systems, ele... more Using a relativistic quark model approach that successfully described flavored meson systems, electromagnetic form factors and structure functions are calculated for the low mass baryons. The observed proton, neutron and lambda moments, rms radii and form factors are all reproduced and predictions are made for other baryon observables which will be measured at CEBAF. Most significantly, by properly including the quark potential energy the long standing neutron to proton structure function ratio anomaly for x ~ 1 has been resolved.
Physics Letters B, 1992
A new type of high resolution pair spectrometer for medium energy photons has been used for studi... more A new type of high resolution pair spectrometer for medium energy photons has been used for studies of the exclusive (p, ~/) reaction on ~ ~B at 98 MeV. Angular distributions of the differential cross section for transitions to the ground state and first excited state in J2C are presented. The distributions show good agreement with predictions from a microscopic continuum shell model calculation which uses a realistic finite-range effective interaction with tensor components.
Physical Review Letters, 1976
ABSTRACT
Physical Review D, 1999
Extending previous QCD Hamiltonian studies, we present a new renormalization procedure which gene... more Extending previous QCD Hamiltonian studies, we present a new renormalization procedure which generates an effective Hamiltonian for the gluon sector. The formulation is in the Coulomb gauge where the QCD Hamiltonian is renormalizable and the Gribov problem can be resolved. We utilize elements of the G lazek and Wilson regularization method but now introduce a continuous cutoff procedure which eliminates non-local counterterms. The effective Hamiltonian is then derived to second order in the strong coupling constant. The resulting renormalized Hamiltonian provides a realistic starting point for approximate many-body calculations of hadronic properties for systems with explicit gluon degrees of freedom.
Physical Review C, 1976
The direct reaction A(a, b)B is described by exactly solving the Schrodinger equation for a few-b... more The direct reaction A(a, b)B is described by exactly solving the Schrodinger equation for a few-body Hamiltonian within a restricted model space. The model space allows for coupling to rearrangement channels by including basis vectors classified according to different mass partitions. The nonorthogonality of basis vectors that correspond to different mass partitions is investigated in detail. A surface approximation is developed to understand the magnitudes of multistep amplitudes produced by channel coupling to rearranged partitions. The surface approximation uses a separable Green's function approximation to the multistep series, and gives a convenient closed-form expression. Finite-range coupled-channels calculations are presented for the reactions (d, d), (d, p), and (p, p) on oxygen and zirconium targets, and for (' 0, ' 0), (' 0,"C), and ("C,"C) on silicon and sulfur targets. To assess higher-order effects, these results are consistently compared with lowest-order results using folded distorting potentials. The calculations indicate that the effects of nonorthogonality are small for these reactions, but the light-ion reactions showed much larger effects. Theoretical explanations of the behavior of nonorthogonality and channel-coupling effects are given, and lead to criteria for predicting when such effects may be important. Channel-coupling effects are expected to be important whenever the distorted-wave Born-approximation transfer amplitude is unusually sensitive to the intermediate channel optical potential. Nonorthogonality efFects are roughly proportional to channel-coupling effects, but are much smaller than coupling effects except when a small mass is transferred between two large masses.
Physical Review C, 1978
ABSTRACT