Journal Club

Seminar Room, Mondays at 14:00

Monday 15th of February, 2016

A Broadband Approach to Axion Dark Matter Detection

When ultralight axion dark matter encounters a static magnetic field, it sources an effective electric current that follows the magnetic field lines and oscillates at the axion Compton frequency. We propose a new experiment to detect this axion effective current. In the presence of axion dark matter, a large toroidal magnet will act like an oscillating current ring, whose induced magnetic flux can be measured by an external pickup loop inductively coupled to a SQUID magnetometer. We consider both resonant and broadband readout circuits and show that a broadband approach has advantages at small axion masses. We estimate the reach of this design, taking into account the irreducible sources of noise, and demonstrate potential sensitivity to axion dark matter with masses in the range of 10^{-13} eV to 10^{-6} eV, particularly the QCD axion with a GUT-scale decay constant.
Comments: 5+3 pages, 3 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
Report number: MIT-CTP 4763, PUPT 2497
Cite as: arXiv:1602.01086 [hep-ph]
  (or arXiv:1602.01086v1 [hep-ph] for this version)
Presented by R. Vega-Morales

Dark Sunshine: Detecting Dark Matter through Dark Photons from the Sun

Dark matter may interact with the Standard Model through the kinetic mixing of dark photons, A, with Standard Model photons. Such dark matter will accumulate in the Sun and annihilate into dark photons. The dark photons may then leave the Sun and decay into pairs of charged Standard Model particles that can be detected by the Alpha Magnetic Spectrometer. The directionality of this "dark sunshine" is distinct from all astrophysical backgrounds, providing an opportunity for unambiguous dark matter discovery by AMS. We perform a complete analysis of this scenario including Sommerfeld enhancements of dark matter annihilation and the effect of the Sun's magnetic field on the signal, and we define a set of cuts to optimize the signal probability. With the three years of data already collected, AMS may discover dark matter with mass 1 TeV mX 10 TeV, dark photon masses mA(100) MeV, and kinetic mixing parameters 1011ε108. The proposed search extends beyond existing beam dump and supernova bounds, and it is complementary to direct detection, probing the same region of parameter space for elastic dark matter, but potentially far more in the case of inelastic dark matter.
Comments: 30 Pages, 10 Figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Experiment (hep-ex)
Report number: UCI-TR-2016-02
Cite as: arXiv:1602.01465 [hep-ph]
  (or arXiv:1602.01465v1 [hep-ph] for this version)
Presented by R. Vega-Morales

One-loop effective lagrangians after matching

We discuss the shortcomings of the recently proposed functional method to compute the one-loop Standard Model (SM) effective lagrangian when the heavy fields couple linearly to the SM. In particular, one-loop contributions resulting from the exchange of both heavy and light fields must be explicitly taken into account through matching because the proposed functional approach alone does not account for them. We review a simple case with a heavy scalar singlet of charge 1 to illustrate the argument. As two other examples where this matching is needed and the functional method gives a vanishing result, up to renormalization of the heavy sector parameters, we re-evaluate the one-loop corrections to the T--parameter due to a heavy scalar triplet of hypercharge 1 coupling to the Brout-Englert-Higgs boson and to a heavy vector-like quark singlet of charged 2/3 mixing with the top quark, respectively. In all cases we make use of a new code for matching fundamental and effective theories in models with arbitrary heavy field additions.
Comments: 22 pages
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex)
Report number: UG-FT-319/16; CAFPE-189/16
Cite as: arXiv:1602.00126 [hep-ph]
  (or arXiv:1602.00126v1 [hep-ph] for this version)
Presented by J. Santiago