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Nuclear Theory·nucl-th

Wednesday·March 18, 2015

8 papers—3 primary·5 cross-listed

All8Primary3Cross-lists5
  1. 04

    Chiral power counting of one- and two-body currents in direct detection of dark matter

    Martin Hoferichter🇩🇪 · Philipp Klos🇩🇪 · Achim Schwenk🇩🇪

    We present a common chiral power-counting scheme for vector, axial-vector, scalar, and pseudoscalar WIMP-nucleon interactions, and derive all one- and two-body currents up to third order in the chiral expansion. Matching our amplitudes to non-relativistic effective field theory, we find that chiral symmetry predicts a hierarchy amongst the non-relativistic operators. Moreover, we identify interaction channels where two-body currents that so far have not been accounted for become relevant.

    ↳ hep-phastro-ph.COnucl-thPLB(2015)·133 citations
  2. 05

    Spallation Backgrounds in Super-Kamiokande Are Made in Muon-Induced Showers

    Shirley Weishi Li🇺🇸 · John F. Beacom (Ohio State University)🇺🇸

    Crucial questions about solar and supernova neutrinos remain unanswered. Super-Kamiokande has the exposure needed for progress, but detector backgrounds are a limiting factor. A leading component is the beta decays of isotopes produced by cosmic-ray muons and their secondaries, which initiate nuclear spallation reactions. Cuts of events after and surrounding muon tracks reduce this spallation decay background by (at a cost of deadtime), but its rate at 6--18 MeV is still dominant. A better way to cut this background was suggested in a Super-Kamiokande paper [Bays {\it et al.}, Phys.~Rev.~D {\bf 85}, 052007 (2012)] on a search for the diffuse supernova neutrino background. They found that spallation decays above 16 MeV were preceded near the same location by a peak in the apparent Cherenkov light profile from the muon; a more aggressive cut was applied to a limited section of the muon track, leading to decreased background without increased deadtime. We put their empirical discovery on a firm theoretical foundation. We show that almost all spallation decay isotopes are produced by muon-induced showers and that these showers are rare enough and energetic enough to be identifiable. This is the first such demonstration for any detector. We detail how the physics of showers explains the peak in the muon Cherenkov light profile and other Super-K observations. Our results provide a physical basis for practical improvements in background rejection that will benefit multiple studies. For solar neutrinos, in particular, it should be possible to dramatically reduce backgrounds at energies as low as 6 MeV.

    ↳ hep-phastro-ph.HEhep-exnucl-ex+1PRD(2015)·72 citations
  3. 06

    Light-front representation of chiral dynamics in peripheral transverse densities

    C. Granados🇸🇪 · C. Weiss🇺🇸

    The nucleon's electromagnetic form factors are expressed in terms of the transverse densities of charge and magnetization at fixed light-front time. At peripheral transverse distances the densities are governed by chiral dynamics and can be calculated model-independently using chiral effective field theory (EFT). We represent the leading-order chiral EFT results for the peripheral transverse densities as overlap integrals of chiral light-front wave functions, describing the transition of the initial nucleon to soft pion-nucleon intermediate states and back. The new representation (a) explains the parametric order of the peripheral transverse densities; (b) establishes an inequality between the spin-independent and -dependent densities; (c) exposes the role of pion orbital angular momentum in chiral dynamics; (d) reveals a large left-right asymmetry of the current in a transversely polarized nucleon and suggests a simple interpretation. The light-front representation enables a first-quantized, quantum-mechanical view of chiral dynamics that is fully relativistic and exactly equivalent to the second-quantized, field-theoretical formulation. It relates the charge and magnetization densities measured in low-energy elastic scattering to the generalized parton distributions probed in peripheral high-energy scattering processes. The method can be applied to nucleon form factors of other operators, e.g. the energy-momentum tensor.

    ↳ hep-phnucl-thJHEP(2015)·14 citations
  4. 07

    Probing the substructure of

    Amir H. Fariborz🇺🇸 · Azizollah Azizi🇮🇷 · Abdorreza Asrar🇮🇷

    Within an effective nonlinear chiral Lagrangian framework the substructure of is studied. The investigation is conducted in the context of a global picture of scalar mesons in which the importance of the underlying connections among scalar mesons below and above 1 GeV is recognized and implemented. These connections are due to the mixings among various quark-antiquarks, four-quarks and glue components and play a central role in understanding the properties of scalar mesons. Iterative Monte Carlo simulations are first performed on the 14-dimensional parameter space of the model and sets of points in this parameter space (the global sets) that give an overall agreement with all experimental data on mass spectrum, various decay widths and decay ratios of all isosinglet scalar states below 2 GeV are determined. Then within each global set, subsets that give closest agreement for the properties of are studied. Unlike the properties of other isosinglet states that show a range of variation within each global set, it is found that there is a clear signal for to be predominantly a quark-antiquark state with a substantial component, together with small remnants of four-quark and glue components.

    ↳ hep-phhep-exnucl-thPRD(2015)·14 citations
  5. 08

    production in photon - induced interactions at the AFTER@LHC experiment as a probe of the Odderon

    V. P. Goncalves🇧🇷 · W. K. Sauter🇧🇷

    One of the open questions of the strong interaction theory is the existence of the Odderon, which is an unambiguous prediction of Quantum Chromodynamics, but still not confirmed experimentally. An alternative to probe the Odderon is the exclusive photoproduction in hadronic collisions. As the Pomeron exchange cannot contribute to this process, its observation would indicate the existence of the Odderon. In this paper we estimate the production in photon - induced interactions in hadronic collisions at the AFTER@LHC experiment. We demonstrate that the experimental analysis of this process is feasible in the AFTER@LHC experiment and that the observation of the production in nuclear collisions is a unambiguous signature of the Odderon.

    ↳ hep-phhep-exnucl-exnucl-thPRD(2015)·37 citations

Affiliations

first authorsco-authorsvia INSPIRE