3 research outputs found
Pion-less Effective Field Theory on Low-Energy Deuteron Electro-Disintegration
In view of its relation to Big-Bang Nucleo-Synthesis and a reported
discrepancy between nuclear models and data taken at S-DALINAC, electro-induced
deuteron break-up 2H(e,e' p)n is studied at momentum transfer q<100MeV and
close to threshold in the low-energy nuclear Effective Field Theory without
dynamical pions. The result at N2LO for electric dipole currents and at NLO for
magnetic ones converges order-by-order better than quantitatively predicted and
contains no free parameter. It is at this order determined by simple,
well-known observables. Decomposing the doubly differential cross-section into
the longitudinal-plus-transverse (L+T), transverse-transverse (TT) and
longitudinal-transverse interference (LT) terms, we find excellent agreement
with a potential-model calculation by Arenh"ovel et al using the Bonn
potential. Theory and data also agree well on \sigma_{L+T}. There is however no
space on the theory-side for the discrepancy of up to 30%, 3-\sigma between
theory and experiment in \sigma_{LT}. From universality, we conclude that no
theoretical approach with the correct deuteron asymptotic wave-function can
explain the data. Un-determined short-distance contributions that could affect
\sigma_{LT} enter only at high orders, i.e. at the few-percent level. We notice
some issues with the kinematics and normalisation of the data reported.Comment: 30 pages LaTeX2e, including 10 figures as 34 .eps files embedded with
includegraphicx. Increased figure sizes; contents identical to version
approved for publication in Phys Rev C -- spelling and grammatical
difference
Universal Correlations in Pion-less EFT with the Resonating Group Model: Three and Four Nucleons
The Effective Field Theory "without pions" at next-to-leading order is used
to analyze universal bound state and scattering properties of the 3- and
4-nucleon system. Results of a variety of phase shift equivalent nuclear
potentials are presented for bound state properties of 3H and 4He, and for the
singlet S-wave 3He-neutron scattering length a_0(3He-n). The calculations are
performed with the Refined Resonating Group Method and include a full treatment
of the Coulomb interaction and the leading-order 3-nucleon interaction. The
results compare favorably with data and values from AV18(+UIX) model
calculations. A new correlation between a_0(3He-n) and the 3H binding energy is
found. Furthermore, we confirm at next-to-leading order the correlations,
already found at leading-order, between the 3H binding energy and the 3H charge
radius, and the Tjon line. With the 3H binding energy as input, we get
predictions of the Effective Field Theory "without pions" at next-to-leading
order for the root mean square charge radius of 3H of (1.6\pm 0.2) fm, for the
4He binding energy of (28\pm 2.5) MeV, and for Re(a_0(3He-n)) of (7.5\pm
0.6)fm. Including the Coulomb interaction, the splitting in binding energy
between 3H and 3He is found to be (0.66\pm 0.03) MeV. The discrepancy to data
of (0.10\mp 0.03) MeV is model independently attributed to higher order charge
independence breaking interactions. We also demonstrate that different results
for the same observable stem from higher order effects, and carefully assess
that numerical uncertainties are negligible. Our results demonstrate the
convergence and usefulness of the pion-less theory at next-to-leading order in
the 4He channel. We conclude that no 4-nucleon interaction is needed to
renormalize the theory at next-to-leading order in the 4-nucleon sector.Comment: 24 pages revtex4, including 8 figures as .eps files embedded with
includegraphicx, leading-order results added, calculations include the LO
three-nucleon interaction explicitly, comment on Wigner bound added, minor
modification