This Article is brought to you for free and open access by the Physics at ODU Digital Commons. It has been accepted for inclusion in Physics Faculty Publications by an authorized administrator of ODU Digital Commons. For more information, please contact digitalcommons@odu.edu. Repository Citation Urciuoli, G. M.; Hayes, D.; Hyde, C. E.; Ibrahim, H. F.; Ulmer, P.E.; and Jefferson Lab Hall A Collaboration, "Spectroscopy of Li-9 (Lambda) by Electroproduction" (2015). Physics Faculty Publications. 152. https://digitalcommons.odu.edu/physics_fac_pubs/152

In the absence of accurate data on the free two-body hyperon-nucleon interaction, the spectra of hypernuclei can provide information on the details of the effective hyperon-nucleon interaction. Electroproduction of the hypernucleus Lambda-9Li has been studied for the first time with sub-MeV energy resolution in Hall A at Jefferson Lab on a 9Be target. In order to increase the counting rate and to provide unambiguous kaon identification, two superconducting septum magnets and a Ring Imaging CHerenkov detector (RICH) were added to the Hall A standard equipment. The cross section to low-lying states of Lambda-9Li is concentrated within 3 MeV of the ground state and can be fitted with four peaks. The positions of the doublets agree with theory while a disagreement could exist with respect to the relative strengths of the peaks in the doublets. A Lambda separation energy of 8.36 +- 0.08 (stat.) +- 0.08 (syst.) MeV was measured, in agreement with an earlier experiment.

The characteristics of the Jefferson Lab electron beam, together with those of the experimental equipment, offer a unique opportunity to study hypernuclear spectroscopy via electromagnetic induced (e,e′K+) reactions. Experiment 94-107 started a systematic study on 1p-shell targets, C12, Be9 and O16. For C12 for the first time measurable strength in the core-excited part of the spectrum between the ground state and the p state was shown in the BΛ12 spectrum. For O16 a high-quality NΛ16 spectrum was produced for the first time with sub-MeV energy resolution. A very precise Λ binding energy value for NΛ16, calibrated against the elementary (e,e′K+) reaction on hydrogen, has also been obtained. Preliminary data on the LiΛ9 spectrum shows some disagreement in strength for the second and third doublet with respect to the theory.

The kaon electroproduction reaction 1H(e,e'K+)Lambda was studied as a function of the virtual-photon four-momentum, Q2, total energy, W, and momentum transfer, t, for different values of the virtual- photon polarization parameter. Data were taken at electron beam energies ranging from 3.40 to 5.75 GeV. The center of mass cross section was determined for 21 kinematics corresponding to Q2 of 1.90 and 2.35 GeV2 and the longitudinal, sigmaL, and transverse, sigmaT, cross sections were separated using the Rosenbluth technique at fixed W and t. The separated cross sections reveal a flat energy dependence at forward kaon angles not satisfactorily described by existing electroproduction models. Influence of the kaon pole on the cross sections was investigated by adopting an off-shell form factor in the Regge model which better describes the observed energy dependence of sigmaT and sigmaL.

An experimental study of the (16)O(e,e'K(+))(Lambda)(16)N reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the p(e,e'K(+))Lambda, Sigma(0) exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of 13.76+/-0.16 MeV was obtained for (Lambda)(16)N with better precision than previous measurements on the mirror hypernucleus (Lambda)(16)O. Precise energies have been determined for peaks arising from a Lambda in s and p orbits coupled to the p(1/2) and p(3/2) hole states of the (15)N core nucleus.

An experiment measuring electroproduction of hypernuclei has been performed in hall A at Jefferson Lab on a 12C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring imaging Cherenkov detector were added to the hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed (Lambda)(12)B spectrum shows for the first time identifiable strength in the core-excited region between the ground-state s-wave Lambda peak and the 11 MeV p-wave Lambda peak.

We measured angular distributions of differential cross section, beam analyzing power, and recoil polarization for neutral pion electroproduction at Q^2 = 1.0 (GeV/c)^2 in 10 bins of W across the Delta resonance. A total of 16 independent response functions were extracted, of which 12 were observed for the first time. Comparisons with recent model calculations show that response functions governed by real parts of interference products are determined relatively well near 1.232 GeV, but variations among models is large for response functions governed by imaginary parts and for both increases rapidly with W. We performed a nearly model-independent multipole analysis that adjusts complex multipoles with high partial waves constrained by baseline models. Parabolic fits to the W dependence of the multipole analysis around the Delta mass gives values for SMR = (-6.61 +/- 0.18)% and EMR = (-2.87 +/- 0.19)% that are distinctly larger than those from Legendre analysis of the same data. Similarly, the multipole analysis gives Re(S0+/M1+) = (+7.1 +/- 0.8)% at W=1.232 GeV, consistent with recent models, while the traditional Legendre analysis gives the opposite sign because its truncation errors are quite severe. Finally, using a unitary isobar model (UIM), we find that excitation of the Roper resonance is dominantly longitudinal with S1/2 = (0.05 +/- 0.01) GeV^(-1/2) at Q^2=1. The ReS0+ and ReE0+ multipoles favor pseudovector coupling over pseudoscalar coupling or a recently proposed mixed-coupling scheme, but the UIM does not reproduce the imaginary parts of 0+ multipoles well.

G.M. Urciuoli, F. Cusanno, A. Acha, P. Ambrozewicz, K.A. Aniol, P. Baturin, P.Y. Bertin, H. Benaoum, K.I. Blomqvist, W.U. Boeglin, H. Breuer, P. Brindza, P. Bydžovský, A. Camsonne, C.C. Chang, J.-P. Chen, Seonho Choi, E.A. Chudakov, E. Cisbani, S. Colilli, L. Coman, B.J. Craver, G. De Cataldo, C.W. de Jager, R. De Leo, A.P. Deur, C. Ferdi, R.J. Feuerbach, E. Folts, R. Fratoni, S. Frullani, F. Garibaldi, O. Gayou, F. Giuliani, J. Gomez, M. Gricia, J.O. Hansen, D. Hayes, D.W. Higinbotham, T.K. Holmstrom, C.E. Hyde, 5 H.F. Ibrahim, M. Iodice, X. Jiang, L.J. Kaufman, K. Kino, B. Kross, L. Lagamba, J.J. LeRose, R.A. Lindgren, M. Lucentini, D.J. Margaziotis, P. Markowitz, S. Marrone, Z.E. Meziani, K. McCormick, R.W. Michaels, D.J. Millener, T. Miyoshi, B. Moffit, P.A. Monaghan, M. Moteabbed, C. Muñoz Camacho, S. Nanda, E. Nappi, V.V. Nelyubin, B.E. Norum, Y. Okasyasu, K.D. Paschke, C.F. Perdrisat, E. Piasetzky, V.A. Punjabi, Y. Qiang, B. Raue, P.E. Reimer, J. Reinhold, B. Reitz, R.E. Roche, V.M. Rodriguez, A. Saha, F. Santavenere, A.J. Sarty, J. Segal, A. Shahinyan, J. Singh, S. Širca, R. Snyder, P.H. Solvignon, M. Sotona, R. Subedi, V.A. Sulkosky, T. Suzuki, H. Ueno, P.E. Ulmer, P. Veneroni, E. Voutier, B.B. Wojtsekhowski, X. Zheng, and C. Zorn