Limits on a CP-violating scalar axion-nucleon interaction

Axions or similar hypothetical pseudoscalar bosons may have a small CP-violating scalar Yukawa interaction g_s(N) with nucleons, causing macroscopic monopole-dipole forces. Torsion-balance experiments constrain g_p(e) g_s(N), whereas g_p(N) g_s(N) is constrained by the depolarization rate of ultra-cold neutrons or spin-polarized nuclei. However, the pseudoscalar couplings g_p(e) and g_p(N) are strongly constrained by stellar energy-loss arguments and g_s(N) by searches for anomalous monopole-monopole forces, together providing the most restrictive limits on g_p(e) g_s(N) and g_p(N) g_s(N). The laboratory limits on g_s(N) are currently the most restrictive constraints on CP-violating axion interactions.Comment: 5 pages, 4 figures, small textual changes in v2, matches published versio

Axions - Motivation, limits and searches

The axion solution of the strong CP problem provides a number of possible windows to physics beyond the standard model, notably in the form of searches for solar axions and for galactic axion dark matter, but in a broader context also inspires searches for axion-like particles in pure laboratory experiments. We briefly review the motivation for axions, astrophysical limits, their possible cosmological role, and current searches for axions and axion-like particles.Comment: Contribution to IRGAC 06, Barcelona. New figure for allowed axion parameters, including hot dark matter limit

New Supernova Limit on Large Extra Dimensions

If large extra dimensions exist in nature, supernova (SN) cores will emit large fluxes of Kaluza-Klein gravitons, producing a cosmic background of these particles with energies and masses up to about 100 MeV. Radiative decays then give rise to a diffuse cosmic gamma-ray background with E_gamma < 100 MeV which is well in excess of the observations if more than 0.5-1% of the SN energy is emitted into the new channel. This argument complements and tightens the well-known cooling limit from the observed duration of the SN1987A neutrino burst. For two extra dimensions we derive a conservative bound on their radius of R < 0.9 x 10^-4 mm, for three extra dimensions it is R < 1.9 x 10^-7 mm.Comment: 4 pages, 3 figures, slightly expanded discussion, matches version to appear in PR

Reconstructing the supernova bounce time with neutrinos in IceCube

Generic model predictions for the early neutrino signal of a core-collapse supernova (SN) imply that IceCube can reconstruct the bounce to within about +/- 3.5 ms at 95% CL (assumed SN distance 10 kpc), relevant for coincidence with gravitational-wave detectors. The timing uncertainty scales approximately with distance-squared. The offset between true and reconstructed bounce time of up to several ms depends on the neutrino flavor oscillation scenario. Our work extends the recent study of Pagliaroli et al. [PRL 103, 031102 (2009)] and demonstrates IceCube's superb timing capabilities for neutrinos from the next nearby SN.Comment: 4 pages, 1 figure, some references and caveats added, matches final version in PR

Constraining invisible neutrino decays with the cosmic microwave background

Precision measurements of the acoustic peaks of the cosmic microwave background indicate that neutrinos must be freely streaming at the photon decoupling epoch when T ~ 0.3 eV. This requirement implies restrictive limits on ``secret neutrino interactions,'' notably on neutrino Yukawa couplings with hypothetical low-mass (pseudo)scalars \phi. For diagonal couplings in the neutrino mass basis we find g < 1 x 10^-7, comparable to limits from supernova 1987A. For the off-diagonal couplings and assuming hierarchical neutrino masses we find g < 1 x 10^-11 (0.05 eV/m)^2 where m is the heavier mass of a given neutrino pair connected by g. This stringent limit excludes that the flavor content of high-energy neutrinos from cosmic-ray sources is modified by \nu -> \nu' + \phi decays on their way to Earth.Comment: Revtex, 4 page

Solar constraints on hidden photons re-visited

We re-examine solar emission of hidden photons gamma' (mass m) caused by kinetic mixing. We calculate the emission rate with thermal field theory methods and with a kinetic equation that includes "flavor oscillations" and photon absorption and emission by the thermal medium. In the resonant case both methods yield identical emission rates which, in the longitudinal channel, are enhanced by a factor w_P^2/m^2 (plasma frequency w_P) in agreement with An, Pospelov and Pradler (2013). The Sun must not emit more energy in a "dark channel" than allowed by solar neutrino measurements, i.e., not more than 10% of its photon luminosity. Together with the revised emission rate, this conservative requirement implies a bound \chi<4\times 10^-12 eV/m for the kinetic mixing parameter. This is the most restrictive stellar limit below m ~ 3 eV, whereas for larger masses the transverse channel dominates together with limits from other stars. A recent analysis of XENON10 data marginally improves the solar limit, leaving open the opportunity to detect solar hidden photons with future large-scale dark matter experiments. Detecting low-mass hidden photons with the ALPS-II photon-regeneration experiment also remains possible.Comment: 17 pages, 4 figure