Beneke, M., Hellmann, C., & Ruiz-Femenia, P. (2013). Non-relativistic pair annihilation of nearly mass degenerate neutralinos and charginos I. General framework and S-wave annihilation. J. High Energy Phys., 03(3), 148–48pp.
Abstract: We compute analytically the tree-level annihilation rates of a collection of non-relativistic neutralino and chargino two-particle states in the general MSSM, including the previously unknown off-diagonal rates. The results are prerequisites to the calculation of the Sommerfeld enhancement in the MSSM, which will be presented in subsequent work. They can also be used to obtain concise analytic expressions for MSSM dark matter pair annihilation in the present Universe for a large number of exclusive two-particle final states.
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Beneke, M., Hellmann, C., & Ruiz-Femenia, P. (2015). Heavy neutralino relic abundance with Sommerfeld enhancements – a study of pMSSM scenarios. J. High Energy Phys., 03(3), 162–37pp.
Abstract: We present a detailed discussion of Sommerfeld enhancements in neutralino dark matter relic abundance calculations for several popular benchmark scenarios in the general MSSM. Our analysis is focused on models with heavy wino- and higgsino-like neutralino LSI' and models interpolating between these two scenarios. This work is the first phenomenological application of effective field theory methods that we have developed in earlier work and that allow for the consistent study of Sommerfeld enhancements in nonrelativistic neutralino and chargino co-annihilation reactions within the general MSSM, away from the pure-wino and pure-higgsino limits.
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Jantzen, B., & Ruiz-Femenia, P. (2013). Next-to-next-to-leading order nonresonant corrections to threshold top-pair production from e(+)e(-) collisions: Endpoint-singular terms. Phys. Rev. D, 88(5), 054011–20pp.
Abstract: We analyze the subleading nonresonant contributions to the e(+)e(-) -> W(+)W(-)b (b) over bar cross section at energies near the top-antitop threshold. These correspond to next-to-next-to-leading-order (NNLO) corrections with respect to the leading-order resonant result. We show that these corrections produce 1/epsilon endpoint singularities which precisely cancel the finite-width divergences arising in the resonant production of the W(+)W(-)b (b) over bar final state from on-shell decays of the top and antitop quarks at the same order. We also provide analytic results for the (m(t)/Lambda)(2), (m(t)/Lambda) and (m(t)/Lambda)(0) log Lambda terms that dominate the expansion in powers of (Lambda/m(t)) of the complete set of NNLO nonresonant corrections, where Lambda is a cut imposed on the invariant masses of the bW pairs that is neither too tight nor too loose (m(t)Gamma(t) << Lambda(2) << m(t)(2)).
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Beneke, M., Hellmann, C., & Ruiz-Femenia, P. (2015). Non-relativistic pair annihilation of nearly mass degenerate neutralinos and charginos III. Computation of the Sommerfeld enhancements. J. High Energy Phys., 05(5), 115–57pp.
Abstract: This paper concludes the presentation of the non-relativistic effective field theory formalism designed to calculate the radiative corrections that enhance the pair-annihilation cross sections of slowly moving neutralinos and charginos within the general minimal supersymmetric standard model (MSSM). While papers I and II focused on the computation of the tree-level annihilation rates that feed into the short-distance part, here we describe in detail the method to obtain the Sommerfeld factors that contain the enhanced long-distance corrections. This includes the computation of the potential interactions in the MSSM, which are provided in compact analytic form, and a novel solution of the multi-state Schrodinger equation that is free from the numerical instabilities generated by large mass splittings between the scattering states. Our results allow for a precise computation of the MSSM neutralino dark matter relic abundance and pair-annihilation rates in the present Universe, when Sommerfeld enhancements are important.
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Filipuzzi, A., Portoles, J., & Ruiz-Femenia, P. (2012). Zeros of the W(L)Z(L) -> W(L)Z(L) amplitude: where vector resonances stand. J. High Energy Phys., 08(8), 080–22pp.
Abstract: A Higgsless electroweak theory may be populated by spin-1 resonances around E similar to 1 TeV as a consequence of a new strong interacting sector, frequently proposed as a tool to smear the high-energy behaviour of scattering amplitudes, for instance, elastic gauge boson scattering. Information on those resonances, if they exist, must be contained in the low-energy couplings of the electroweak chiral effective theory. Using the facts that: i) the scattering of longitudinal gauge bosons, W-L, Z(L), can be well described in the high-energy region (E >> M-W) by the scattering of the corresponding Goldstone bosons (equivalence theorem) and ii) the zeros of the scattering amplitude carry the information on the heavier spectrum that has been integrated out; we employ the O(p(4)) electroweak chiral Lagrangian to identify the parameter space region of the low-energy couplings where vector resonances may arise. An estimate of their masses is also provided by our method.
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