We explore the role of a scalar meson exchange interaction between quarks in a semirelativistic constituent quark model where the quarks are subject to a linear confinement. We search for a variational solution and show that the gap between the N=1 band and the ground state N=0 band increases with the strength of the scalar meson exchange interaction potential. This result has good implications on the description of the low-lying baryon resonances, especially on the Roper vs. negative parity resonances ordering.

P. Stassart Fl. Stancu J. -M. Richard

The photoproduction of pion off nucleon is investigated within a dynamical coupled-channels approach based on the Juelich pi-N model, which has been quite successful in the description of pi-N to pi-N scattering for center-of-mass energies up to 1.9 GeV. The full pion photoproduction amplitude is constructed to satisfy the generalized Ward-Takahashi identity and hence, it is fully gauge invariant. The calculated differential cross sections and photon spin asymmetries up to 1.65 GeV center-of-mass energy for the reactions gamma p to pi^+ n, gamma p to pi^0 p and gamma n to pi^- p are in good agreement with the experimental data.

F. Huang M. Döring H. Haberzettl J. Haidenbauer C. Hanhart S. Krewald U. -G. Meißner K. Nakayama

We are designing and fabricating two new thermionic sources of magnetized electrons for use in the electron lens project in the Integrable Optics Test Accelerator (IOTA) at Fermilab. These electron sources will be used for cooling 2.5 MeV protons. One source will be used to compensate for emittance growth due to Intra Beam Scattering in experiments with weak space-charge, while the other source will be used to research the interplay between electron cooling and intense space charge. In this paper we present the progress made so far and the upcoming steps for the thermionic electron sources.

M. K. Bossard J. Brandt Y. -K. Kim S. Kladov N. Banerjee B. Cathey G. Stancari S. Nagaitsev

The Integrable Optics Test Accelerator at Fermilab will explore beam dynamics in a ring with intense space-charge using 2.5 MeV proton beams with an incoherent tune shift approaching -0.5. We will use this machine to explore the interplay between electron cooling, intense space-charge, and coherent instabilities. In this contribution, we describe the machine setup including the design of the electron cooler and the lattice, list specific experiments and discuss the results of numerical simulations which include the effects of electron cooling and transverse space-charge forces.

N. Banerjee G. Stancari M. K. Bossard J. Brandt Y-K. Kim S. Nagaitsev

We present two low-mass YSOs in IC5070 (V1490Cyg, V1706Cyg) with deep recurring eclipses.

D. Froebrich A. Scholz J. Campbell-White J. Crumpton E. D'Arcy S. V. Makin T. Zegmott. S. J. Billington R. Hibbert R. J. Newport C. R. Fisher

The Spin Asymmetries of the Nucleon Experiment (SANE) measured two double spin asymmetries using a polarized proton target and polarized electron beam at two beam energies, 4.7 GeV and 5.9 GeV. A large-acceptance open-configuration detector package identified scattered electrons at 40$^{\circ}$ and covered a wide range in Bjorken $x$ ($0.3 < x < 0.8$). Proportional to an average color Lorentz force, the twist-3 matrix element, $\tilde{d}_2^p$, was extracted from the measured asymmetries at $Q^2$ values ranging from 2.0 to 6.0 GeV$^2$. The data display the opposite sign compared to most quark models, including the lattice QCD result, and an apparently unexpected scale dependence. Furthermore when combined with the neutron data in the same $Q^2$ range the results suggest a flavor independent average color Lorentz force.

W. Armstrong H. Kang A. Liyanage J. Maxwell J. Mulholland L. Ndukum A. Ahmidouch I. Albayrak A. Asaturyan O. Ates H. Baghdasaryan W. Boeglin P. Bosted E. Brash C. Butuceanu M. Bychkov P. Carter C. Chen J. -P. Chen S. Choi M. E. Christy S. Covrig D. Crabb S. Danagoulian A. Daniel A. M. Davidenko B. Davis D. Day W. Deconinck A. Deur J. Dunne D. Dutta L. El Fassi C. Ellis R. Ent D. Flay E. Frlez D. Gaskell O. Geagla J. German R. Gilman T. Gogami J. Gomez Y. M. Goncharenko O. Hashimoto D. Higinbotham T. Horn G. M. Huber M. Jones M. K. Jones N. Kalantarians H-K. Kang D. Kawama C. Keith C. Keppel M. Khandaker Y. Kim P. M. King M. Kohl K. Kovacs V. Kubarovsky Y. Li N. Liyanage W. Luo D. Mack V. Mamyan P. Markowitz T. Maruta D. Meekins Y. M. Melnik Z. -E. Meziani A. Mkrtchyan H. Mkrtchyan V. V. Mochalov P. Monaghan A. Narayan S. N. Nakamura A. Nuruzzaman L. Pentchev D. Pocanic M. Posik A. Puckett X. Qiu J. Reinhold S. Riordan J. Roche O. A. Rondón B. Sawatzky M. Shabestari K. Slifer G. Smith L. F. Soloviev P. Solvignon V. Tadevosyan L. Tang A. N. Vasiliev M. Veilleux T. Walton F. Wesselmann S. Wood H. Yao Z. Ye J. Zhang L. Zhu

We report on the calculation by the MILC Collaboration of the electromagnetic effects on kaon and pion masses. These masses are computed in QCD with dynamical (asqtad staggered) quarks plus quenched photons at three lattice spacings varying from 0.12 to 0.06 fm. The masses are fit to staggered chiral perturbation theory with NLO electromagnetic terms, as well as analytic terms at higher order. We extrapolate the results to physical light-quark masses and to the continuum limit. At the current stage of the analysis, most, but not all, of the systematic errors have been estimated. The main goal is the comparison of kaon electromagnetic splittings to those of the pion, i.e., an evaluation of the corrections to "Dashen's theorem." This in turn will allow us to significantly reduce the systematic errors in our determination of m_u/m_d.

S. Basak A. Bazavov C. Bernard C. DeTar E. Freeland W. Freeman J. Foley Steven Gottlieb U. M. Heller J. E. Hetrick J. Laiho L. Levkova M. Oktay J. Osborn R. L. Sugar A. Torok D. Toussaint R. S. Van de Water R. Zhou

We present some piloting calculations of the masses of the doubly heavy baryons in the framework of the simple approximation within the nonperturbative string approach. The simple analytical results for dynamical masses of heavy and light quarks and eigenvalues of the effective QCD Hamiltonian are presented.

I. M. Narodetskii M. A. Trusov

The average mass composition of cosmic rays with primary energies between $10^{17}$eV and $10^{18}$eV has been studied using a hybrid detector consisting of the High Resolution Fly's Eye (HiRes) prototype and the MIA muon array. Measurements have been made of the change in the depth of shower maximum, $X_{max}$, and in the change in the muon density at a fixed core location, $\rho_\mu(600m)$, as a function of energy. The composition has also been evaluated in terms of the combination of $X_{max}$ and $\rho_\mu(600m)$. The results show that the composition is changing from a heavy to lighter mix as the energy increases.

T. Abu-Zayyad K. Belov D. J. Bird J. Boyer Z. Cao M. Catanese G. F. Chen R. W. Clay C. E. Covault J. W. Cronin H. Y. Dai B. R. Dawson J. W. Elbert B. E. Fick L. F. Fortson J. W. Fowler K. G. Gibbs M. A. K. Glasmacher K. D. Green Y. Ho A. Huang C. C. Jui M. J. Kidd D. B. Kieda B. C. Knapp S. Ko C. G. Larsen W. Lee E. C. Loh E. J. Mannel J. Matthews J. N. Matthews B. J. Newport D. F. Nitz R. A. Ong K. M. Simpson J. D. Smith D. Sinclair P. Sokolsky P. Sommers C. Song J. K. K. Tang S. B. Thomas J. C. van der Velde L. R. Wiencke C. R. Wilkinson S. Yoshida X. Z. Zhang

We study the spectrum and average mass composition of cosmic rays with primary energies between 10^{17} eV and 10^{18} eV using a hybrid detector consisting of the High Resolution Fly's Eye (HiRes) prototype and the MIA muon array. Measurements have been made of the change in the depth of shower maximum as a function of energy. A complete Monte Carlo simulation of the detector response and comparisons with shower simulations leads to the conclusion that the cosmic ray intensity is changing f rom a heavier to a lighter composition in this energy range. The spectrum is consistent with earlier Fly's Eye measurements and supports the previously found steepening near 4 \times 10^{17} eV .

T. Abu-Zayyad K. Belov D. J. Bird J. Boyer Z. Cao M. Catanese G. F. Chen R. W. Clay C. E. Covault H. Y. Dai B. R. Dawson J. W. Elbert B. E. Fick L. F. Fortson J. W. Fowler K. G. Gibbs M. A. K. Glasmacher K. D. Green Y. Ho A. Huang C. C. Jui M. J. Kidd D. B. Kieda B. C. Knapp S. Ko C. G. Larsen W. Lee E. C. Loh E. J. Mannel J. Matthews J. N. Matthews B. J. Newport D. F. Nitz R. A. Ong K. M. Simpson J. D. Smith D. Sinclair P. Sokolsky P. Sommers C. Song J. K. K. Tang S. B. Thomas J. van der Velde L. R. Wiencke C. R. Wilkinson S. Yoshida X. Z. Zhang