1202.1292 (Hai-Yang Cheng et al.)

Revisiting Scalar and Pseudoscalar Couplings with Nucleons    [PDF]

Hai-Yang Cheng, Cheng-Wei Chiang

Certain dark matter interactions with nuclei are mediated possibly by a
scalar or pseudoscalar Higgs boson. The estimation of the corresponding cross
sections requires a correct evaluation of the couplings between the scalar or
pseudoscalar Higgs boson and the nucleons. Progress has been made in two
aspects relevant to this study in the past few years. First, recent lattice
calculations show that the strange-quark sigma term $\sigma_s$ and the
strange-quark content in the nucleon are much smaller than what are expected
previously. Second, lattice and model analyses imply sizable SU(3) breaking
effects in the determination on the axial-vector coupling constant $g_A^8$ that
in turn affect the extraction of the isosinglet coupling $g_A^0$ and the
strange quark spin component $\Delta s$ from polarized deep inelastic
scattering experiments. Based on these new developments, we re-evaluate the
relevant nucleon matrix elements and compute the scalar and pseudoscalar
couplings of the proton and neutron. We also find that the strange quark
contribution in both types of couplings is smaller than previously thought.

View original: http://arxiv.org/abs/1202.1292