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

Pseudoscalar Conversion and X-rays from the Sun

We investigate the detection of a pseudoscalar $\phi$ that couples electromagnetically via an interaction ${1\over4}g \phi F {\tilde F}$. In particular, we focus on the conversion of pseudoscalars produced in the sun's interior in the presence of the sun's external magnetic dipole field and sunspot-related magnetic fields. We find that the sunspot approach is superior. Measurements by the SXT on the Yohkoh satellite can measure the coupling constant down to $g=0.5$--$1 \times 10^{-10}\,\rm GeV^{-1}$, provided the pseudoscalar mass $m < 7{\times} 10^{-6}\,$eV, which makes it competitive with other astrophysical approaches.Comment: 15 pages, RevTex file. Figures available upon request to [email protected]. (please include full mailing address in request). Submitted to Physics Letters

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

New analysis of the SN 1987A neutrinos with a flexible spectral shape

We analyze the neutrino events from the supernova (SN) 1987A detected by the Kamiokande II (KII) and Irvine-Michigan-Brookhaven (IMB) experiments. For the time-integrated flux we assume a quasi-thermal spectrum of the form $(E/E_0)^\alpha e^{-(\alpha+1)E/E_0}$ where $\alpha$ plays the role of a spectral index. This simple representation not only allows one to fit the total energy $E_{\rm tot}$ emitted in $\bar\nu_e$ and the average energy , but also accommodates a wide range of shapes, notably anti-pinched spectra that are broader than a thermal distribution. We find that the pile-up of low-energy events near threshold in KII forces the best-fit value for $\alpha$ to the lowest value of any assumed prior range. This applies to the KII events alone as well as to a common analysis of the two data sets. The preference of the data for an ``unphysical'' spectral shape implies that one can extract meaningful values for and $E_{\rm tot}$ only if one fixes a prior value for $\alpha$. The tension between the KII and IMB data sets and theoretical expectations for $$ is not resolved by an anti-pinched spectrum.Comment: to appear in PRD (6 pages, 6 eps figures

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

Supernova and neutron-star limits on large extra dimensions reexamined

In theories with large extra dimensions, supernova (SN) cores are powerful sources of Kaluza-Klein (KK) gravitons. A large fraction of these massive particles are gravitationally retained by the newly born neutron star (NS). The subsequent slow KK decays produce potentially observable gamma rays and heat the NS. We here show that the back-absorption of the gravitationally trapped KK gravitons does not significantly change our previous limits. We calculate the graviton emission rate in a nuclear medium by combining the low-energy classical bremsstrahlung rate with detailed-balancing arguments. This approach reproduces the previous thermal emission rate, but it is much simpler and allows for a calculation of the absorption rate by a trivial phase-space transformation. We derive systematically the dependence of the SN and NS limits on the number of extra dimensions.Comment: Erratum included (small numerical correction of neutron-star limits