Power Counting of Contact-Range Currents in Effective Field Theory

We analyze the power counting of two-body currents in nuclear effective field theories (EFTs). We find that the existence of non-perturbative physics at low energies, which is manifest in the existence of the deuteron and the 1S0 NN virtual bound state, combined with the appearance of singular potentials in versions of nuclear EFT that incorporate chiral symmetry, modifies the renormalization-group flow of the couplings associated with contact operators that involve nucleon-nucleon pairs and external fields. The order of these couplings is thereby enhanced with respect to the naive-dimensional-analysis estimate. Consequently, short-range currents enter at a lower order in the chiral EFT than has been appreciated up until now, and their impact on low-energy observables is concomitantly larger. We illustrate the changes in the power counting with a few low-energy processes involving external probes and the few-nucleon systems, including electron-deuteron elastic scattering and radiative neutron capture by protons.Comment: 5 pages. Minor revisions. Conclusions unchanged. Version to appear in Physical Review Letter

New Lepidoptera-Parasitoid Associations in Weedy Corn Plantings: A Potential Alternate Host for \u3ci\u3eOstrinia Nubilalis\u3c/i\u3e (Lepidoptera: Pyralidae) Parasitoids

Larvae of the common sooty wing, Pholisora catullus, and pupae of the yellow-collared scape moth, Cisseps Fulvicollis, were collected in corn plantings containing different manipulated, indigenous weed communities to determine if these Lepidoptera had parasitoid species in common with the European corn borer, Ostrinia nubilalis. Pholisora catullus larvae were collected from lambsquarter, Chenopodium album, and redroot pigweed, Amaranthus retroflexus, whereas pupae of C. Julvicollis were obtained from corn. Four parasitoid species were reared from P. catulIus: Cotesia pholisorae, Oncophanes americanu (Hymenoptera: Braconidae), Gambrus ultimus, and Sinophorus albipalpus (Hymenoptera: Ichneumonidae). Of these, O. americanus and S. albipalpus represent new host records. Gambrus ultimus, however, was probably parasitizing a primary parasitoid of P. catullus. Itoplectis conquisitor and Vulgichneumon brevicinctor (Hymenoptera: Ichneumonidae) were reared from C. fulvicollis; V. brevicinctor had not previously been associated with this host. Both species reared from C. fulvicollis and Gambrus ultimus have been reported from O. nubilalis

Models, measurements, and effective field theory: proton capture on Beryllium-7 at next-to-leading order

We employ an effective field theory (EFT) that exploits the separation of scales in the p-wave halo nucleus $^8\mathrm{B}$ to describe the process $^7\mathrm{Be}(p,\gamma)^8\mathrm{B}$ up to a center-of-mass energy of 500 keV. The calculation, for which we develop the lagrangian and power counting, is carried out up to next-to-leading order (NLO) in the EFT expansion. The power counting we adopt implies that Coulomb interactions must be included to all orders in $\alpha_{\rm em}$. We do this via EFT Feynman diagrams computed in time-ordered perturbation theory, and so recover existing quantum-mechanical technology such as the two-potential formalism for the treatment of the Coulomb-nuclear interference. Meanwhile the strong interactions and the E1 operator are dealt with via EFT expansions in powers of momenta, with a breakdown scale set by the size of the ${}^7$Be core, $\Lambda \approx 70$ MeV. Up to NLO the relevant physics in the different channels that enter the radiative capture reaction is encoded in ten different EFT couplings. The result is a model-independent parametrization for the reaction amplitude in the energy regime of interest. To show the connection to previous results we fix the EFT couplings using results from a number of potential model and microscopic calculations in the literature. Each of these models corresponds to a particular point in the space of EFTs. The EFT structure therefore provides a very general way to quantify the model uncertainty in calculations of $^7\mathrm{Be}(p,\gamma)^8\mathrm{B}$. We also demonstrate that the only N$^2$LO corrections in $^7\mathrm{Be}(p,\gamma)^8\mathrm{B}$ come from an inelasticity that is practically of N$^3$LO size in the energy range of interest, and so the truncation error in our calculation is effectively N$^3$LO. We also discuss the relation of our extrapolated $S(0)$ to the previous standard evaluation.Comment: 68 pages, 10 figures, and 4 table