title: Isoscalar monopole resonance of the alpha particle: a prism to nuclear Hamiltonians.
abstract: We present an ab initio study of the isoscalar monopole excitations of (4)He using different realistic nuclear interactions, including modern effective field theory potentials. In particular we concentrate on the transition form factor F(M) to the narrow 0(+) resonance close to threshold. F(M) exhibits a strong potential model dependence, and can serve as a kind of prism to distinguish among different nuclear force models. Compared to the measurements obtained from inelastic electron scattering off ^{4}He, one finds that the state-of-the-art theoretical transition form factors are at variance with experimental data, especially in the case of effective field theory potentials. We discuss some possible reasons for such a discrepancy, which still remains a puzzle.
authors.affiliation: TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada V6J 2A3.
authors.forename: Sonia
authors.initials: S
authors.lastname: Bacca
authors.affiliation: Racah Institute of Physics, The Hebrew University, 91904 Jerusalem, Israel.
authors.forename: Nir
authors.initials: N
authors.lastname: Barnea
authors.affiliation: Dipartimento di Fisica, Università di Trento, I-38123 Trento, Italy and Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Trento, I-38123 Trento, Italy.
authors.forename: Winfried
authors.initials: W
authors.lastname: Leidemann
authors.affiliation: Dipartimento di Fisica, Università di Trento, I-38123 Trento, Italy and Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Trento, I-38123 Trento, Italy.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Orlandini