Revisiting the SN1987A gamma-ray limit on ultralight axion-like particles

We revise the bound from the supernova SN1987A on the coupling of ultralight axion-like particles (ALPs) to photons. In a core-collapse supernova, ALPs would be emitted via the Primakoff process, and eventually convert into gamma rays in the magnetic field of the Milky Way. The lack of a gamma-ray signal in the GRS instrument of the SMM satellite in coincidence with the observation of the neutrinos emitted from SN1987A therefore provides a strong bound on their coupling to photons. Due to the large uncertainty associated with the current bound, we revise this argument, based on state-of-the-art physical inputs both for the supernova models and for the Milky-Way magnetic field. Furthermore, we provide major amendments, such as the consistent treatment of nucleon-degeneracy effects and of the reduction of the nuclear masses in the hot and dense nuclear medium of the supernova. With these improvements, we obtain a new upper limit on the photon-ALP coupling: g_{a\gamma} < 5.3 x 10^{-12} GeV^{-1}, for m_a < 4.4 x 10^{-10} eV, and we also give its dependence at larger ALP masses. Moreover, we discuss how much the Fermi-LAT satellite experiment could improve this bound, should a close-enough supernova explode in the near future.Comment: Accepted for publication in JCAP (December 22nd, 2014

Axions, their Relatives and Prospects for the Future

The observation of a non-vanishing rotation of linear polarized laser light after passage through a strong magnetic field by the PVLAS collaboration has renewed the interest in light particles coupled to photons. Axions are a species of such particles that is theoretically well motivated. However, the relation between coupling and mass predicted by standard axion models conflicts with the PVLAS observation. Moreover, light particles with a coupling to photons of the strength required to explain PVLAS face trouble from astrophysical bounds. We discuss models that can avoid these bounds. Finally, we present some ideas to test these possible explanations of PVLAS experimentally.Comment: 11 pages, 4 figures. Contributed to the ``Third Symposium on Large TPCs for Low Energy Rare Event Detection'' in Paris, December 200

Any light particle search at DESY

The Any Light Particle Search (ALPS II) is a light shining through a wall (LSW) experiment searching for axion-like elementary particles in the sub-eV mass range, which are motivated by astrophysics and cosmology and fulfill the requirements for being dark matter. ALPS II aims to measure an axion-to-photon coupling of $2\times 10^{-11}\textrm{ GeV}^{-1}$, which is several orders of magnitude better than that of previous LSW experiments and will thus investigate a new parameter range. The increased performance is achieved by enhancing the magnetic field interaction length to $2\times 10^{6}$ m and by amplifying the signal in an optical cavity on each side of a light-tight barrier. The expected signal is in the order of 1 photon per day, which will be measured by photon detectors with very low dark count rates of $\mathcal{O}(10^{-6}\textrm{ Hz})$. This article gives a technical overview on the experiment design, previous and ongoing investigations, and the current status with focus on the single photon detection

Any Light Particle Search II - Status Overview

The Any Light Particle Search II (ALPS II) experiment (DESY, Hamburg) searches for photon oscillations into Weakly Interacting Sub-eV Particles (WISPs). This second generation of the ALPS light-shining-through-a-wall (LSW) experiment approaches the finalization of the preparation phase before ALPS IIa (search for hidden photons). In the last years, efforts have been put for the setting up of two optical cavities as well as the characterization of a single-photon Transition-Edge Sensor (TES) detector. In the following, we put some emphasis on the detector development. In parallel, the setting up of ALPS IIc (search for axion-like particles), including the unbending of 20 HERA dipoles, has been pursued. The latest progress in these tasks will b

Approaching the first any light particle search II science run

The Any Light Particle Search II (ALPS II) is a light-shining-through-a-wall (LSW) experiment based at DESY in Hamburg, Germany, that will search for axions and axion-like particles down to the coupling of the axion to two photons of $g_{a\gamma\gamma}$ >2$\times10^{-11}$ GeV$^{-1}$ for masses below 0.1 meV. ALPS II will use two strings of superconducting dipole magnets that are over one hundred meters in length, as well as optical cavities before and after the wall to boost the effective signal rate of the regenerated photons by more than 12 orders of magnitude when compared to previous generations of LSW experiments. Data taking with a simplified optical system is expected to begin in early 2023

ALPS II technical overview and status report

The Any Light Particle Search II (ALPS\,II) is an experiment that utilizes the concept of resonant enhancement to improve on the sensitivity of traditional light shining through a wall style experiments. These experiments attempt to detect photons passing through an opaque wall by converting to relativistic weakly interacting sub-eV particles and then reconverting back to photons. ALPS\,II at DESY in Hamburg, Germany will use dually resonant optical cavities before and after the wall to increase the probability of this interaction occurring. This paper gives a technical overview and status report of the experiment

The Any Light Particle Search Experiment at DESY

The Any Light Particle Search (ALPS II) is a light shining through a wall (LSW) experiment searching for axion-like elementary particles in the sub-eV mass range, which are motivated by astrophysics and cosmology and fulfill the requirements for being dark matter. ALPS II aims to measure an axion-to-photon coupling of $2\times 10^{-11}\textrm{ GeV}^{-1}$, which is several orders of magnitude better than that of previous LSW experiments and will thus investigate a new parameter range. The increased performance is achieved by enhancing the magnetic field interaction length to $2\times 10^{6}$ m and by amplifying the signal in an optical cavity on each side of a light-tight barrier. The expected signal is in the order of 1 photon per day, which will be measured by photon detectors with very low dark count rates of $\mathcal{O}(10^{-6}\textrm{ Hz})$. This article gives a technical overview on the experiment design, previous and ongoing investigations, and the current status with focus on the single photon detection

Status of ALPS-II at DESY

The light-shining-through-a-wall (LSW) experiment ALPS at DESY provides the current best lab-based bounds for WISP couplings. Based on this success, preparations for ALPS-II have started. The aim is to increase the sensitivity by three orders of magnitude to probe parameter regions with astrophysical hints for the existence of WISPs from white dwarf energy loss and the TeV transparency of the intergalactic medium. To reach this sensitivity, ALPS-II will be considerably longer, making use of 2 x 12 HERA dipole magnets. The laser power in the WISP-production region will be increased and a second optical cavity in the regeneration region will be constructed. Additionally, a very low-noise transition-edge photo-detector is in development. In a pre-experiment, it will be possible to probe the hidden-photon interpretation of the WMAP-7 excess in sterile neutrinos

First sensitivity limits of the ALPS TES detector

The Any Light Particle Search II (ALPS II) requires a sensitive detection of 1064~nm photons. Thus, a low dark count rate ($DC$) and a high detection efficiency ($DE$) is needed. ALPS has set up a transition-edge sensor (TES) detector system, namely the ALPS TES detector. It is found that thermal photons from room temperature surfaces are the main contribution of dark counts for 1064~nm photon signals. Furthermore, the current setup of the ALPS TES detector shows an improvement compared to using the ALPS I detector