@article{xie_mo_wang_cotanch_2013, title={Coulomb gauge model for hidden charm tetraquarks}, volume={725}, ISSN={["1873-2445"]}, DOI={10.1016/j.physletb.2013.07.003}, abstractNote={Abstract 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 ( q c ¯ ) 1 ( c q ¯ ) 1 singlet–singlet (molecule) and the ( q c ) 3 ( q ¯ c ¯ ) 3 triplet–triplet (diquark), for selected J PC states using a variational method. The predicted masses of triplet–triplet tetraquarks are roughly a GeV heavier than the singlet–singlet states. There is also an interesting flavor dependence with ( q q ¯ ) 1 ( c c ¯ 1 ) states about half a GeV lighter than ( q c ¯ ) 1 ( q ¯ c ) 1 . The lightest 1 + + and 1 − − predictions are in agreement with the observed X ( 3872 ) and Y ( 4008 ) masses suggesting they are molecules with ω J / ψ and η h c , rather than D ⁎ D ¯ ⁎ and D D ¯ , type structure, respectively. Similarly, the lightest isovector 1 + + molecule, having a ρ J / 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 π π J / ψ .}, number={1-3}, journal={PHYSICS LETTERS B}, author={Xie, W. and Mo, L. Q. and Wang, Ping and Cotanch, Stephen R.}, year={2013}, month={Aug}, pages={148–152} }
 @article{cotanch_2010, title={Coupled channels optical theorem and non-elastic cross section sum rule}, volume={842}, ISSN={["0375-9474"]}, DOI={10.1016/j.nuclphysa.2010.04.011}, abstractNote={Within a coupled channels framework a theorem, similar to the optical theorem, is proved which provides a new formula for total non-elastic (inelastic, rearrangement and absorption) cross sections. An approximate cross section energy sum rule is also developed in terms of the trace of the imaginary part of an energy independent, but non-local optical potential. Corrections to sum rule are found small indicating that the result is a good approximation. The theorem and sum rule are applied to the Lane model describing charge exchange reactions.}, journal={NUCLEAR PHYSICS A}, author={Cotanch, Stephen R.}, year={2010}, month={Oct}, pages={48–58} }
 @article{wang_cotanch_general_2008, title={Meson and tetra-quark mixing}, volume={55}, ISSN={["1434-6044"]}, DOI={10.1140/epjc/s10052-008-0605-7}, abstractNote={The mixing between qq̄ meson and qq̄qq̄ tetra-quark states is examined within an effective QCD Coulomb gauge Hamiltonian model. Mixing matrix elements of the Hamiltonian are computed and then diagonalized yielding an improved prediction for the low-lying JPC=0±+,1– isoscalar spectra. Mixing effects were found significant for the scalar hadrons but not for the 1– states, which is consistent with the ideal mixing of vector mesons. A perturbative assessment of the exact QCD kernel is also reported.}, number={3}, journal={EUROPEAN PHYSICAL JOURNAL C}, author={Wang, Ping and Cotanch, Stephen R. and General, Ignacio J.}, year={2008}, month={Jun}, pages={409–415} }
 @article{general_llanes-estrada_cotanch_2007, title={Coulomb gauge approach to (qqg)over-bar hybrid mesons}, volume={51}, ISSN={["1434-6052"]}, DOI={10.1140/epjc/s10052-007-0298-3}, abstractNote={An effective Coulomb gauge Hamiltonian, Heff, is used to calculate the light (uūg), strange (ss̄g) and charmed (cc̄g) hybrid meson spectra. For the same two parameter Heff providing glueball masses consistent with lattice results and a good description of the observed u,d,s and c quark mesons, a large-scale variational treatment predicts that the lightest hybrid has JPC=0++ and mass 2.1 GeV. The lightest exotic 1-+ state is just above 2.2 GeV, near the upper limit of lattice and flux tube predictions. These theoretical formulations all indicate that the observed 1-+ π1(1600) and, more clearly, π1(1400) are not hybrid states. The Coulomb gauge approach further predicts that in the strange and charmed sectors, respectively, the ground state hybrids have 1+- with masses 2.1 and 3.8 GeV, while the first exotic 1-+ states are at 2.4 and 4.0 GeV. Finally, using our hybrid wavefunctions and the Franck–Condon principle, a novel experimental signature is presented to assist heavy hybrid meson searches.}, number={2}, journal={EUROPEAN PHYSICAL JOURNAL C}, author={General, I. J. and Llanes-Estrada, F. J. and Cotanch, S. R.}, year={2007}, month={Jul}, pages={347–358} }
 @article{general_wang_cotanch_llanes-estrada_2007, title={Light 1(-+) exotics: Molecular resonances}, volume={653}, ISSN={["1873-2445"]}, DOI={10.1016/j.physletb.2007.08.015}, abstractNote={Highlights in the search for nonconventional (non-qq¯) meson states are the π1(1400) and π1(1600) exotic candidates. Should they exist, mounting theoretical arguments suggest that they are tetraquark molecular resonances excitable by meson rescattering. We report a new tetraquark calculation within a model field theory approximation to Quantum Chromodynamics in the Coulomb gauge supporting this conjecture. We also strengthen this claim by consistently contrasting results with exotic state predictions for hybrid (qq¯g) mesons within the same theoretical framework. Our findings confirm that molecular-like configurations involving two color singlets (a resonance, not a bound state) are clearly favored over hybrid or color-exotic tetraquark meson (qq¯qq¯ atoms) formation. Finally, to assist needed further experimental searches we document a useful off-plane correlator for establishing the structure of these exotic systems along with similar, but anticipated much narrower, states that should exist in the charmonium and bottomonium spectra.}, number={2-4}, journal={PHYSICS LETTERS B}, author={General, Ignacio J. and Wang, Ping and Cotanch, Stephen R. and Llanes-Estrada, Felipe J.}, year={2007}, month={Sep}, pages={216–223} }
 @article{cotanch_general_wang_2007, title={QCD Coulomb gauge approach to exotic hadrons}, volume={31}, ISSN={["1434-6001"]}, DOI={10.1140/epja/i2006-10234-2}, abstractNote={The Coulomb gauge Hamiltonian model is used to calculate masses for selected JPC states consisting of exotic combinations of quarks and gluons: ggg glueballs (oddballs), q¯g hybrid mesons and q¯q¯ tetraquark systems. An odderon Regge trajectory is computed for the J- glueballs with intercept much smaller than the pomeron, explaining its nonobservation. The lowest 1-+ hybrid-meson mass is found to be just above 2.2GeV while the lightest tetraquark state mass with these exotic quantum numbers is predicted around 1.4GeV consistent with the observed π(1400).}, number={4}, journal={EUROPEAN PHYSICAL JOURNAL A}, author={Cotanch, S. R. and General, I. J. and Wang, P.}, year={2007}, month={Mar}, pages={656–661} }
 @article{bicudo_cotanch_llanes-estrada_robertson_2007, title={The BES f(0)(1810): a new glueball candidate}, volume={52}, ISSN={["1434-6052"]}, DOI={10.1140/epjc/s10052-007-0377-5}, abstractNote={We analyze the f0(1810) state recently observed by the BES collaboration via radiative J/ψ decay to a resonant φω spectrum and confront it with DM2 data and glueball theory. The DM2 group only measured ωω decays and reported a pseudoscalar but no scalar resonance in this mass region. A rescattering mechanism from the open flavored KK̄ decay channel is considered to explain why the resonance is only seen in the flavor asymmetric ωφ branch along with a discussion of positive C-parity charmonia decays to strengthen the case for preferred open flavor glueball decays. We also calculate the total decay width of a glueball with this mass to be roughly 100 MeV, in agreement with the narrow, newly found f0, and smaller than the expected estimate of 200–400 MeV. We conclude that this discovered scalar hadron deserves further experimental investigation, especially in the KK̄ channel, and if shown to be different from the f0(1710), will become a solid glueball candidate. Finally we comment on other, but less likely, possible assignments for this state.}, number={2}, journal={EUROPEAN PHYSICAL JOURNAL C}, author={Bicudo, P. and Cotanch, S. R. and Llanes-Estrada, F. J. and Robertson, D. G.}, year={2007}, month={Oct}, pages={363–374} }
 @article{llanes-estrada_bicudo_cotanch_2006, title={J(--) glueballs and a low odderon intercept}, volume={96}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.96.081601}, abstractNote={We report an odderon Regge trajectory emerging from a field theoretical Coulomb gauge QCD model for the odd signature J(PC) (P = C = -1) glueball states. The trajectory intercept is clearly smaller than the Pomeron and even the omega 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.}, number={8}, journal={PHYSICAL REVIEW LETTERS}, author={Llanes-Estrada, FJ and Bicudo, P and Cotanch, SR}, year={2006}, month={Mar} }
 @article{schafer_kao_cotanch_2005, title={Many body methods and effective field theory}, volume={762}, ISSN={["1873-1554"]}, url={http://inspirehep.net/record/681694}, DOI={10.1016/j.nuclphysa.2005.08.006}, abstractNote={In the framework of pionless nucleon-nucleon effective field theory we study different approximation schemes for the nuclear many body problem. We consider, in particular, ladder diagrams constructed from particle-particle, hole-hole, and particle-hole pairs. We focus on the problem of finding a suitable starting point for perturbative calculations near the unitary limit (k_Fa)->infinity and (k_Fr)-> 0, where k_F is the Fermi momentum, a is the scattering length and r is the effective range. We try to clarify the relationship between different classes of diagrams and the large g and large D approximations, where g is the fermion degeneracy and D is the number of space time dimensions. In the large D limit we find that the energy per particle in the strongly interacting system is 1/2 the result for free fermions.}, number={1-2}, journal={NUCLEAR PHYSICS A}, author={Schafer, T and Kao, CW and Cotanch, SR}, year={2005}, month={Nov}, pages={82–101} }
 @article{cotanch_williams_2005, title={Tensor glueball photoproduction and decay}, volume={621}, ISSN={["1873-2445"]}, DOI={10.1016/j.physletb.2005.06.069}, abstractNote={Using vector meson dominance (VMD), tensor glueball photoproduction cross sections, asymmetries and widths are calculated. The predicted hadronic VV' decays are comparable for different vector meson (V = rho, omega and phi) channels with the omega phi width the largest but the radiative omega gamma and phi gamma decays are suppressed relative to rho gamma by over a factor of 2. This decay profile is distinct from typical meson branching rates and may be a useful glueball detection signature. Results are compared to a previous VMD scalar glueball study.}, number={3-4}, journal={PHYSICS LETTERS B}, author={Cotanch, SR and Williams, RA}, year={2005}, month={Aug}, pages={269–275} }
 @article{cotanch_2005, title={Time-like compton scattering and the Bethe-Heitler process}, volume={24}, DOI={10.1007/3-540-26345-4_22}, journal={European Physical Journal. A, Hadrons and Nuclei}, author={Cotanch, Stephen}, year={2005}, pages={101–102} }
 @article{salwen_sheets_cotanch_2004, title={BCS and attractive Hubbard model comparative study}, volume={70}, ISSN={["1098-0121"]}, DOI={10.1103/physrevb.70.064511}, abstractNote={We extend previous studies of the BCS canonical approach for the attractive Hubbard model. A derivation of the BCS formulation is presented for both the Hubbard and a simpler reduced Hamiltonian. Using direct diagonalization, exact one and two dimensional solutions for both Hamiltonians are compared to BCS variational calculations. Approximate and exact ground state energies and energy gaps are computed for different electron number systems as well as correlation observables not previously predicted. Reproducing published one dimensional findings, the BCS is an excellent approximation for the Hubbard ground state energy but not energy gap, a finding that remains true in two dimensions. Propagators and correlators are found more sensitive to wavefunctions and appreciable differences are computed with the Hubbard model exhibiting a weaker degree of superconductivity than the BCS. However for the reduced Hamiltonian model the BCS is an excellent approximation for all observables in both one and two dimensions.}, number={6}, journal={PHYSICAL REVIEW B}, author={Salwen, N and Sheets, SA and Cotanch, SR}, year={2004}, month={Aug} }
 @article{cotanch_williams_2004, title={Glueball enhancements in p(gamma, VV)p through vector meson dominance}, volume={70}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.70.055201}, abstractNote={Double vector meson photoproduction, $p(\ensuremath{\gamma},G\ensuremath{\rightarrow}VV)p$, mediated by a scalar glueball $G$ is investigated. Using vector meson dominance (VMD) and Regge∕pomeron phenomenology, a glueball enhancement is predicted in the invariant $VV=\ensuremath{\rho}\ensuremath{\rho}$ and $\ensuremath{\omega}\ensuremath{\omega}$ mass spectra. The resonant cross-section profile is sensitive to the total glueball width, ${\mathrm{\ensuremath{\Gamma}}}_{G}$, but is discernable for ${\mathrm{\ensuremath{\Gamma}}}_{G}=125\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ or less. The scalar glueball is assumed to be the lightest physical state on the daughter pomeron trajectory governing diffractive vector meson photoproduction. In addition to cross sections, calculations for hadronic and electromagnetic glueball decays, $G\ensuremath{\rightarrow}V{V}^{\ensuremath{'}}(V,{V}^{\ensuremath{'}}=\ensuremath{\rho},\ensuremath{\omega},\ensuremath{\phi},\ensuremath{\gamma})$, and ${\ensuremath{\gamma}}_{v}V\ensuremath{\rightarrow}G$ transition form factors are presented based upon flavor universality, VMD, and phenomenological couplings from $\ensuremath{\phi}$ photoproduction analyses. Due to limited phase space, the predicted glueball $VV$ decay widths are sensitive to the uncertain glueball mass, however the extracted glueball $VV$ coupling constant is similar to an independent theoretical study. Possible signatures for glueball detection are also discussed.}, number={5}, journal={PHYSICAL REVIEW C}, author={Cotanch, SR and Williams, RA}, year={2004}, month={Nov} }
 @article{general_cotanch_2004, title={Goldberger-Treiman constraint criterion for hyperon coupling constants}, volume={69}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.69.035202}, abstractNote={After a half century of investigating meson-baryon interactions, it is somewhat surprising that there are still several important coupling constants not accurately known. While theN coupling constant, gNN, has been determined to within a few percent, significant un- certainty in the two hyperon couplings, gK(Y =�,�)N, re- mains and even recently published values for both vary by more than a factor of four. This large variance is due to limited experimental information and also shortcom- ings in theoretical models. Further, analyses of purely hadronic processes typically yield larger couplings than those obtained from hyperon electromagnetic production studies. Fortunately, with the advent of new accelerator facilities, such as Jefferson Lab and SPring-8, more ac- curate and abundant data are now becoming available. Related, the recently reported (1) discovery of the ex- otic strangeness +1 pentaquark resonance, � + , is also attracting attention which should spawn additional KN measurements.}, number={3}, journal={PHYSICAL REVIEW C}, author={General, IJ and Cotanch, SR}, year={2004}, month={Mar} }
 @article{llanes-estrada_cotanch_szczepaniak_swanson_2004, title={Hyperfine meson splittings: chiral symmetry versus transverse gluon exchange}, volume={70}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.70.035202}, abstractNote={Meson spin splittings are examined within an effective Coulomb gauge QCD Hamiltonian incorporating chiral symmetry and a transverse hyperfine interaction necessary for heavy quarks. For light and heavy quarkonium systems the pseudoscalar-vector meson spectrum is generated by approximate Bardeen-Cooper- Schrieffer, random-phase approximation diagonalizations. This relativistic formulation includes both S and D waves for the vector mesons which generates a set of coupled integral equations. A smooth transition from the heavy to the light quark regime is found with chiral symmetry dominating the p-r mass difference. A reasonable description of the observed meson spin splittings and chiral quantities, such as the quark condensate and the p mass, is obtained. Similar comparisons with Tamm-Dancoff diagonalizations, which violate chiral symmetry, are deficient for light pseudoscalar mesons, indicating the need to simultaneously include both chiral symmetry and a hyperfine interaction. The hb mass is predicted to be around 9400 MeV, consistent with other theoretical expectations and above the unconfirmed 9300 MeV candidate. Finally, for comparison with lattice results, the J reliability parameter is also evaluated.}, number={3}, journal={PHYSICAL REVIEW C}, author={Llanes-Estrada, FJ and Cotanch, SR and Szczepaniak, AP and Swanson, ES}, year={2004}, month={Sep} }
 @article{cotanch_maris_2003, title={Ladder Dyson-Schwinger calculation of the anomalous gamma-3 pi form factor}, volume={68}, ISSN={["2470-0029"]}, DOI={10.1103/physrevd.68.036006}, abstractNote={The anomalous processes, \gamma \to 3 \pi and \gamma \pi \to \pi\pi, are investigated within the Dyson-Schwinger framework using the rainbow-ladder approximation. Calculations reveal that a complete set of ladder diagrams beyond the impulse approximation are necessary to reproduce the fundamental low-energy theorem for the anomalous form factor. Higher momentum calculations also agree with the limited form factor data and exhibit the same resonance behavior as the phenomenological vector meson dominance model.}, number={3}, journal={PHYSICAL REVIEW D}, author={Cotanch, SR and Maris, P}, year={2003}, month={Aug} }
 @article{cotanch_2003, title={Unified many-body approach to mesons, glueballs and hybrids}, volume={50}, ISBN={["*************"]}, ISSN={["0146-6410"]}, DOI={10.1016/S0146-6410(03)00028-0}, abstractNote={A unified quark and gluon description of mesons, glueballs and exotic hybrids is presented for a relativistic field theoretical Hamiltonian in the Coulomb gauge. The effective QCD Hamiltonian entails a linear confining interaction with slope predetermined by lattice theory and is approximately diagonalized using different many-body techniques: BCS for the vacuum ground state; TDA and RPA for the excited hadron spectrum. Chiral symmetry rigorously emerges and is spontaneously broken by the model BCS vacuum which contains dynamically generated constituent quark and gluon condensates described by respective gap equations. The observed low energy meson spectrum and the quenched lattice glueball measurements are reproduced along with a Regge trajectory consistent with the Pomeron. Using generalized vector meson dominance, glueball decays are predicted and a glueball photoproduction experimental signature is predicted. Finally, a variational relativistic three quasiparticle calculation for hybrid mesons is reported which concurs with alternative model predictions that the lightest hybrid states are near but above 2 GeV. This strongly indicates that the recently observed JPC = 1 −+ exotics at 1.4 and 1.6 GeV are more likely four quark states.}, number={2}, journal={PROGRESS IN PARTICLE AND NUCLEAR PHYSICS, VOL 50, NO 2}, author={Cotanch, SR}, year={2003}, pages={353–362} }
 @article{bicudo_cotanch_llanes-estrada_maris_ribeiro_szczepaniak_2002, title={Chirally symmetric quark description of low energy pi-pi scattering}, volume={65}, ISSN={["0556-2821"]}, DOI={10.1103/physrevd.65.076008}, abstractNote={Weinberg’s theorem for π-π scattering, including the Adler zero at threshold in the chiral limit, is analyticall proved for microscopic quark models that preserve chiral symmetry. Implementing Ward-Takahashi identities, the isospin 0 and 2 scattering lengths are derived in exact agreement with Weinberg’s low energy results. Our proof applies to alternative quark formulations including the Hamiltonian and Euclidean space Dyson-Schwinger approaches. Finally, the threshold π-π scattering amplitudes are calculated using the Dyson- Schwinger equations in the rainbow-ladder truncation, confirming the formal derivation.}, number={7}, journal={PHYSICAL REVIEW D}, author={Bicudo, P and Cotanch, S and Llanes-Estrada, F and Maris, P and Ribeiro, E and Szczepaniak, A}, year={2002}, month={Apr} }
 @article{cotanch_williams_2002, title={Probing proton strangeness with time-like virtual Compton scattering}, volume={549}, ISSN={["1873-2445"]}, DOI={10.1016/S0370-2693(02)02869-1}, abstractNote={We document that p(gamma,e+e-)p measurements will yield new, important information about the off-shell time-like nucleon form factors, especially in the phi meson region (q^2 = M^2_{phi}) governing the phi N couplings g^{V,T}_{ϕN N}. Calculations for p(gamma,e+e-)p, utilizing vector meson dominance, predict measurable phi enhancements at high |t| compared to the expected phi background production from pi, eta and Pomeron exchange. The phi form factor contribution generates a novel experimental signature for OZI violation and the proton strangeness content. The phi N couplings are determined independently from a combined analysis of the neutron electric form factor and recent high |t| phi photoproduction. The pi, eta and Pomeron transition form factors are also predicted and the observed pi and eta transition moments are reproduced.}, number={1-2}, journal={PHYSICS LETTERS B}, author={Cotanch, SR and Williams, RA}, year={2002}, month={Nov}, pages={85–92} }
 @article{cotanch_maris_2002, title={QCD based quark description of pi-pi scattering up to the sigma and rho regions}, volume={66}, ISSN={["1550-2368"]}, DOI={10.1103/physrevd.66.116010}, abstractNote={We study forward and backward pi-pi scattering within a QCD model based on the Dyson--Schwinger, Bethe--Salpeter equations truncated to the rainbow-ladder level. Our microscopic relativistic quark formulation preserves chiral symmetry and reproduces the observed scattering lengths for total isospin zero, one and two. At higher energies both scalar and vector meson resonances naturally occur in the scattering amplitudes. We also report a comparative study with phenomenological meson-exchange models and find such approaches are reasonable especially near pi-pi resonances.}, number={11}, journal={PHYSICAL REVIEW D}, author={Cotanch, SR and Maris, P}, year={2002}, month={Dec} }
 @article{llanes-estrada_cotanch_bicudo_ribeiro_szczepaniak_2002, title={QCD glueball Regge trajectory and the pomeron}, volume={710}, ISSN={["1873-1554"]}, DOI={10.1016/S0375-9474(02)01090-4}, abstractNote={Implementing many-body techniques successful in other fields, we report a glueball Regge trajectory emerging from diagonalizing a confining Coulomb gauge Hamiltonian for constituent gluons. Through a BCS vacuum ansatz and gap equation, the dressed gluons acquire a dynamic mass, of order 0.8 GeV, providing the quasiparticle degrees of freedom for a TDA glueball formulation. The TDA eigenstates for two constituent gluons have orbital, L, excitations with a characteristic energy of 0.4 GeV revealing a clear Regge trajectory. In particular, the JPC=2++ glueball coincides with the pomeron given by αP(t)=1.08+(0.25GeV−2)t. We also ascertain that lattice data supports our result. Finally, we conjecture on the odderon puzzle.}, number={1-2}, journal={NUCLEAR PHYSICS A}, author={Llanes-Estrada, FJ and Cotanch, SR and Bicudo, PJD and Ribeiro, JEFT and Szczepaniak, A}, year={2002}, month={Nov}, pages={45–54} }
 @article{llanes-estrada_cotanch_2002, title={Relativistic many-body Hamiltonian approach to mesons}, volume={697}, ISSN={["1873-1554"]}, DOI={10.1016/S0375-9474(01)01237-4}, abstractNote={We represent QCD at the hadronic scale by means of an effective Hamiltonian, H, formulated in the Coulomb gauge. As in the Nambu–Jona-Lasinio model, chiral symmetry is explicitly broken, however our approach is renormalizable and also includes confinement through a linear potential with slope specified by lattice gauge theory. This interaction generates an infrared integrable singularity and we detail the computationally intensive procedure necessary for numerical solution. We focus upon applications for the u,d,s and c quark flavors and compute the mass spectrum for the pseudoscalar, scalar and vector mesons. We also perform a comparative study of alternative many-body techniques for approximately diagonalizing H: BCS for the vacuum ground state; TDA and RPA for the excited hadron states. The Dirac structure of the field theoretical Hamiltonian naturally generates spin-dependent interactions, including tensor, spin–orbit and hyperfine, and we clarify the degree of level splitting due to both spin and chiral symmetry effects. Significantly, we find that roughly two-thirds of the π–ρ mass difference is due to chiral symmetry and that only the RPA preserves chiral symmetry. We also document how hadronic mass scales are generated by chiral symmetry breaking in the model vacuum. In addition to the vacuum condensates, we compute meson decay constants and detail the Nambu–Goldstone realization of chiral symmetry by numerically verifying the Gell-Mann–Oakes–Renner relation.}, number={1-2}, journal={NUCLEAR PHYSICS A}, author={Llanes-Estrada, FJ and Cotanch, SR}, year={2002}, month={Jan}, pages={303–337} }
 @article{llanes-estrada_cotanch_2001, title={Many-body Coulomb gauge exotic and charmed hybrids}, volume={504}, ISSN={["0370-2693"]}, DOI={10.1016/S0370-2693(01)00290-8}, abstractNote={Utilizing an effective QCD Coulomb gauge Hamiltonian with linear confinement specified by lattice, we report a relativistic many-body calculation for the light exotic and charmed hybrid mesons. The Hamiltonian successfully describes both quark and gluon sectors, with vacuum and quasiparticle properties generated by a BCS transformation and more elaborate TDA and RPA diagonalizations for the meson (qq̄) and glueball (gg) masses. Hybrids entail a computationally intense relativistic three quasiparticle (qq̄g) calculation with the 9-dimensional Hamiltonian matrix elements evaluated variationally by Monte Carlo techniques. Our new TDA (RPA) spectrum for the nonexotic 1−− charmed (cc̄ and cc̄g) system provides an explanation for the overpopulation of the observed J/ψ states. For the important 1−+ light exotic channel we obtain hybrid masses above 2 GeV, in broad agreement with lattice and flux tube models, indicating that the recently observed resonances at 1.4 and 1.6 GeV are of different, perhaps four quark, structure.}, number={1-2}, journal={PHYSICS LETTERS B}, author={Llanes-Estrada, FJ and Cotanch, SR}, year={2001}, month={Apr}, pages={15–20} }
 @article{cotanch_llanes-estrada_2001, title={Relativistic many-body approach to exotic and charmed hybrid mesons}, volume={689}, DOI={10.1016/s0375-9474(01)00886-7}, abstractNote={A relativistic many-body calculation for an effective QCD Hamiltonians reported for exotic and charmed hybrid mesons. The nonexotic J(PC) = 1(--) charmonium spectrum now resolves the anonymous overpopulation of observed J/psi states. The exotic hybrid states are near but above 2 GeV, in agreement with lattice and flux-tube calculations, indicating the recently observed J(PC) = 1(+-) resonances at 1.4 and 1.6 GeV are not hybrids.}, number={1-2}, journal={Nuclear Physics. A}, author={Cotanch, Stephen and Llanes-Estrada, F. J.}, year={2001}, pages={481C–484} }
 @article{llanes-estrada_cotanch_2000, title={Coulomb gauge hybrid mason calculation}, volume={90}, ISSN={["0920-5632"]}, DOI={10.1016/S0920-5632(00)00883-5}, abstractNote={We report a relativistic many-body calculation for the hybrid meson spectrum utilizing a QCD inspired Coulomb gauge Hamiltonian.Our approach is comprehensive and unifies the quark and gluon sectors.The vacuum and quasiparticle properties are generated by a BCS transformation, whereas the meson and glueball spectra are described by the TDA and RPA approximations.Using the quark and gluon gap solutions, we formulate hybrid mesons as states composed of three quasiparticles (quark, antiquark and gluon) and compute the mass spectrum variationally with trial wavefunctions.We predict the important exotic 1 -+ states to have masses above 2 GeV in rough agreement with lattice and flux tube models, implying the recently observed resonances are not hybrids.}, number={2000 Dec.}, journal={NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS}, author={Llanes-Estrada, FJ and Cotanch, SR}, year={2000}, month={Dec}, pages={117–119} }
 @article{gubankova_ji_cotanch_2000, title={Flow equations for gluodynamics in the Coulomb gauge}, volume={62}, ISSN={["0556-2821"]}, DOI={10.1103/physrevd.62.074001}, abstractNote={A systematic procedure to consistently formulate a field theoretical, QCD bound state problem with a fixed number of constituents is outlined. The approach entails applying the Hamiltonian flow equations, which are a set of continuous unitary transformations, to a QCD motivated Hamiltonian with a confining interaction. The method is developed in detail for gluodynamics in the Coulomb gauge to obtain an effective block-diagonal Hamiltonian appropriate to a reduced Fock space with a fixed number of dynamical gluons. Standard many-body techniques are used to numerically diagonalize this Hamiltonian in a constituent two gluon Fock space. The calculated gluon condensates and glueball masses are in good agreement with QCD sum rule and lattice results. (c) 2000 The American Physical Society.}, number={7}, journal={PHYSICAL REVIEW D}, author={Gubankova, EL and Ji, CR and Cotanch, SR}, year={2000}, month={Oct} }
 @article{gubankova_ji_cotanch_2000, title={Flow equations for quark-gluon interactions in light-front QCD}, volume={62}, ISSN={["0556-2821"]}, DOI={10.1103/physrevd.62.125012}, abstractNote={The flow-equation method of continuous unitary transformations is used to eliminate the minimal quark-gluon interaction in the light-front quantized QCD Hamiltonian. The coupled differential equations in the two lowest Fock sectors correspond to the renormalization of the light-front gluon mass and the generation of an effective quark-antiquark (as well as gluon-gluon) interaction. The original gauge field coupling is completely eliminated, even in the presence of degenerate states connected by this interaction. Further, a more singular 1/q{sup 4} behavior for the quark and gluon effective interactions at small gluon momenta is obtained, due to the asymptotic behavior of the effective gluon mass for small cutoff. We discuss the consequences of this asymptotic behavior and possible confinement implications.}, number={12}, journal={PHYSICAL REVIEW D}, author={Gubankova, E and Ji, CR and Cotanch, SR}, year={2000}, month={Dec} }
 @article{llanes-estrada_cotanch_2000, title={Meson structure in a relativistic many-body approach}, volume={84}, ISSN={["1079-7114"]}, DOI={10.1103/PhysRevLett.84.1102}, abstractNote={Results from an extensive relativistic many-body analysis utilizing a realistic effective QCD Hamiltonian are presented for the meson spectrum. A comparative numerical study of the BCS, Tamm-Dancoff (TDA), and RPA treatments provides new, significant insight into the condensate structure of the vacuum, the chiral symmetry governance of the pion, and the meson spin, orbital, and flavor mass splitting contributions. In contrast to a previous glueball application, substantial quantitative differences are computed between TDA and RPA for the light quark sector with the pion emerging as a Goldstone boson only in the RPA.}, number={6}, journal={PHYSICAL REVIEW LETTERS}, author={Llanes-Estrada, FJ and Cotanch, SR}, year={2000}, month={Feb}, pages={1102–1105} }
 @article{robertson_swanson_szczepaniak_ji_cotanch_1999, title={Renormalized effective QCD Hamiltonian: Gluonic sector}, volume={59}, ISSN={["2470-0029"]}, DOI={10.1103/physrevd.59.074019}, abstractNote={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 Glazek and Wilson regularization method but now introduce a continuous cut-off 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. {copyright} {ital 1999} {ital The American Physical Society}}, number={7}, journal={PHYSICAL REVIEW D}, author={Robertson, DG and Swanson, ES and Szczepaniak, AP and Ji, CR and Cotanch, SR}, year={1999}, month={Apr} }
 @article{cotanch_williams_1998, title={Probing nucleon strangeness using vector meson dominance}, volume={631}, DOI={10.1016/s0375-9474(98)00051-7}, abstractNote={Calculations for N(π, e+e−)N reactions are reported to motivate measurements of the nucleon time-like form factors in the φ meson mass region. Using vector meson dominance and a field theoretical model which describes pion photoproduction data, crossing predictions for N(π, e+e−)N are detailed exhibiting dramatic, several order of magnitude enhancements from φN coupling in the nucleon form factors. These narrow, dual peaked resonances provide a novel experimental signature for OZI violation and the related strangeness content of the nucleon. A low energy analysis of the limited p(γ, φ)p data is also presented using a similar dynamic model and φN coupling.}, number={1998 Mar. 2}, journal={Nuclear Physics. A}, author={Cotanch, Stephen and Williams, R. A.}, year={1998}, pages={C478–481} }
 @article{cotanch_szczepaniak_swanson_ji_1998, title={QCD Hamiltonian approach for the glueball spectrum}, volume={631}, DOI={10.1016/s0375-9474(98)00082-7}, abstractNote={A new, comprehensive relativistic many-body approach utilizing the Coulomb gauge QCD Hamiltonian is advanced for hadron physics. The formalism properly incoporates renormalization for regularizing divergences and also manifests the Nambu-Goldstone realization of chiral symmetry. Using standard many-body techniques, calculations for the constitutuent quark, gluon condensates and masses and gluon spectrum are found to be in good agreement with QCD sum-rules and quenched lattice gauge results.}, number={1998 Mar. 2}, journal={Nuclear Physics. A}, author={Cotanch, Stephen and Szczepaniak, A. P. and Swanson, E. S. and Ji, Chueng-Ryong}, year={1998}, pages={C640–643} }
 @article{bright_hoistad_johansson_traneus_cotanch_1997, title={Radiative proton capture to discrete states in N-31 at 98 and 176 MeV}, volume={621}, ISSN={["0375-9474"]}, DOI={10.1016/S0375-9474(97)00185-1}, abstractNote={Abstract A high resolution magnetic pair spectrometer for medium energy photons has been used for studies of the exclusive (p,γ) reaction on 12 C at 98 and 176 MeV. We present angular distributions of the differential cross section for transitions to the ground state and the first three excited states of 13 N. The distributions from these four states are compared with predictions from a microscopic continuum shell model calculation using a realistic finite-ranged effective interaction with tensor components. In general, reasonable agreement is obtained for reactions to states described by p shell single particle wave functions, but poor agreement is obtained for transitions described by sd shell single particle wave functions. Nevertheless we find, however, that the dominant reaction mechanism is a direct capture process. We also compare the (p,γ) data with existing data on the exclusive (p,π) reaction at 185 MeV revealing notable differences between the two reactions.}, number={3}, journal={NUCLEAR PHYSICS A}, author={Bright, TB and Hoistad, B and Johansson, R and Traneus, E and Cotanch, SR}, year={1997}, month={Aug}, pages={754–766} }