The ALPS collaboration runs a light-shining-through-walls (LSW) experiment to search for photon oscillations into "weakly interacting sub-eV particles" (WISPs) inside of a superconducting HERA dipole magnet at the site of DESY. In this paper we report on the first successful integration of a large-scale optical cavity to boost the available power for WISP production in this type of experiments. The key elements are a frequency tunable narrow line-width continuous wave laser acting as the primary light source and an electronic feed-back control loop to stabilize the power build-up. We describe and characterize our apparatus and demonstrate the data analysis procedures on the basis of a brief exemplary run.
In the last years it has been realized, that extensions of the Standard Model may manifest itself also at meV energy scales. The low energy frontier is a rich complement to the conventional high-energy particle physics landscape. The search for these new particles initiated experimental activities around the world. "Light shining through a wall" (LSW) experiments search for Weakly Interacting Sub-eV Particles (WISP). Potential WISP candidates are axion-like particles or hidden sector photons. The ALPS (Any Light Particle Search) experiment located at DESY in Hamburg exploits resonant laser pow…
Light-shining-through-walls experiments are the search experiments for weakly interacting slim particles (WISPs) with the smallest model dependence. They have the advantage that not only the detection, but also the production of the WISPs takes place in the laboratory and can thus be controlled. Using lasers is the preferred option for most of the mass region and has led to the world's most stringent laboratory limits (ALPS I) there. At CERN, OSQAR promises to surpass these and at DESY ALPS II is currently set up, which is planning to probe the axion-like particle to photon coupling down to $|…
Physics beyond the Standard Model predicts the possible existence of new particles that can be searched at the low energy frontier in the sub-eV range. The OSQAR photon regeneration experiment looks for "Light Shining through a Wall" from the quantum oscillation of optical photons into "Weakly Interacting Sub-eV Particles", such as axion or Axion-Like Particles (ALPs), in a 9 T transverse magnetic field over the unprecedented length of $2 \times 14.3$ m. In 2014, this experiment has been run with an outstanding sensitivity, using an 18.5 W continuous wave laser emitting in the green at the sin…
The ALPS collaboration runs a "Light Shining through a Wall" (LSW) experiment to search for photon oscillations into "Weakly Interacting Sub-eV Particles" (WISPs) often predicted by extensions of the Standard Model. The experiment is set up around a superconducting HERA dipole magnet at the site of DESY. Due to several upgrades of the experiment we are able to place limits on the probability of photon-WISP-photon conversions of a few 10^{-25}. These limits result in today's most stringent laboratory constraints on the existence of low mass axion-like particles, hidden photons and minicharged p…
ALPS II is a light shining through a wall style experiment that will use optical cavities to resonantly enhance the coupling between photons and axion-like particles in the mass range below 0.1 meV. In the last year there has been significant experimental progress in the development of the optical system and the single photon detection schemes, as well as progress related to the preparation of the magnets and the on site infrastructure.
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 repor…
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 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…
Axion-like particles (ALPs) with couplings to electromagnetism have long been postulated as extensions to the Standard Model. String theory predicts an "axiverse" of many light axions, some of which may make up the dark matter in the universe and/or solve the strong CP problem. We propose a new experiment using superconducting radiofrequency (SRF) cavities which is sensitive to light ALPs independent of their contribution to the cosmic dark matter density. Off-shell ALPs will source cubic nonlinearities in Maxwell's equations, such that if a SRF cavity is pumped at frequencies $ω_1$ and $ω_2$,…
The application of cryogenic single photon detectors has found great use in high precision particle physics experiments such as ALPS (Any Light Particle Search) II, which implements it for fundamental studies to search for new particles. ALPS II is a light-shining-through-a-wall experiment searching for axion-like-particles, which couple to photons. The extremely low rate of photons generated by the conversion of such axion-like-particles necessitates a detector setup capable of low energy (~ 1 eV; as dictated by cavity optics) single photon detection with high efficiency and an ultra-low back…
This document constitutes an excerpt of the Technical Design Report for the second stage of the "Any Light Particle Search" (ALPS-II) at DESY as submitted to the DESY PRC in August 2012 and reviewed in November 2012. ALPS-II is a "Light Shining through a Wall" experiment which searches for photon oscillations into weakly interacting sub-eV particles. These are often predicted by extensions of the Standard Model and motivated by astrophysical phenomena. The first phases of the ALPS-II project were approved by the DESY management on February 21st, 2013.
Single crystals have high atomic electric fields as much as 10^{11} V/m, which correspond to magnetic fields of \sim 10^3 T. These fields can be utilized to convert X rays into Axion Like Particles (ALPs) coherently similar to X-ray diffraction. In this paper, we perform the first theoretical calculation of the Laue-case conversion in crystals based on the Darwin dynamical theory of X-ray diffraction. The calculation shows that the Laue-case conversion has longer interaction length than the Bragg case, and that ALPs in the keV range can be resonantly converted by tuning an incident angle of X …
Light-shining-through-a-wall experiments represent a new experimental approach in the search for undiscovered elementary particles not accessible with accelerator based experiments. The next generation of these experiments, such as ALPS II, require high finesse, long baseline optical cavities with fast length control. In this paper we report on a length stabilization control loop used to keep a 9.2 m cavity resonant. The finesse of this cavity was measured to be 101,300$\pm$500 for 1064 nm light. Fluctuations in the differential cavity length as seen with 1064 nm and 532 nm light were measured…
ALPS II, the Any Light Particle Search, is a second-generation Light Shining through a Wall experiment that hunts for axion-like particles. The experiment is currently transitioning from the design and construction phase to the commissioning phase, with science runs expected to start in 2021. ALPS II plans to use two different sensing schemes to confirm the potential detection of axion-like particles or to verify an upper limit on their coupling strength to two photons of $g_{aγγ}\leq2\times10^{-11}\text{GeV}^{-1}$. This paper discusses a heterodyne sensing scheme (HET) which will be the first…
The ALPS II experiment, Any Light Particle Search II at DESY in Hamburg, will look for light (m< 10-4 eV) new fundamental bosons (e.g., axion-like particles, hidden photons and other WISPs) in the next years by the mean of a light-shining-through-the-wall setup. The ALPS II photosensor is a Transition-Edge Sensor (TES) optimized for lambda = 1064 nm photons. The detector is routinely operated at 80 mK, allowing single infrared photon detections as well as non-dispersive spectroscopy with very low background rates. The demonstrated quantum efficiency for such TES is up to 95% at lambda =1064 nm…
The Any Light Particle Search II (ALPS II) is an experiment currently being built at DESY in Hamburg, Germany, that will use a light-shining-through-a-wall (LSW) approach to search for axion-like particles. ALPS II represents a significant step forward for these types of experiments as it will use 24 superconducting dipole magnets, along with dual, high-finesse, 122 m long optical cavities. This paper gives the first comprehensive recipe for the realization of the idea, proposed over 30 years ago, to use optical cavities before and after the wall to increase the power of the regenerated photon…
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 $2\times 10^{-11}\,\mathrm{GeV^{-1}}$, 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 $\times$ 106\,m …
Challenging optical resonant gain achieved via the use of two geometrically modematched Fabry-Perot cavities is anticipated in Any Light Particle Search II (ALPS II) to extend the search sensitivity of light-weight sub-eV dark matter candidates to uncharted parameter space of scientific interest. We report on the precision optomechanics developed for geometrical modematching of optical cavities. The general concept, the mechanical mounting scheme, and the use of an autocollimator to streamline the metrology procedure are rigorously examined using optical interferometry, all of which meet the r…
Using microwave cavities one can build a resonant ``light-shining-through-walls'' experiment to search for hidden sector photons and axion like particles, predicted in many extensions of the standard model. In this note we make a feasibility study of the sensitivities which can be reached using state of the art technology.
Axion-like particles (ALPs) are undiscovered pseudo-scalar particles that are candidates for ultralight dark matter. ALPs interact with photons slightly and cause the rotational oscillation of linearly polarized light. Dark matter Axion search with riNg Cavity Experiment (DANCE) searches for ALP dark matter by amplifying the rotational oscillation with a bow-tie ring cavity. Simultaneous resonance of linear polarizations is necessary to amplify both the carrier field and the ALP signal, and to achieve the design sensitivity. The sensitivity of the current prototype experiment DANCE Act-1 is le…
The CERN Resonant WISP Search (CROWS) probes the existence of Weakly Interacting Sub-eV Particles (WISPs) like axions or hidden sector photons. It is based on the principle of an optical light shining through the wall experiment, adapted to microwaves. Critical aspects of the experiment are electromagnetic shielding, design and operation of low loss cavity resonators and the detection of weak sinusoidal microwave signals. Lower bounds were set on the coupling constant $g = 4.5 \cdot 10^{-8} $GeV$^{-1}$ for axion like particles with a mass of $m_a = 7.2 μ$eV. For hidden sector photons, lower bo…
Light axion-like particles (ALPs) that couple to two photons are allowed in a number of proposed extensions to the Standard Model of elementary particles. Of particular interest from a theoretical and observational standpoint is the energy regime near 0.1 meV. We present results from a pilot experiment to search for a signal from a 0.14 meV scalar ALP by way of its coupling to two photons. Using a copper resonant cavity cooled to four degrees Kelvin while immersed in a seven Tesla magnetic field, and coupled to a low noise cryogenic amplifier and room temperature receiver, we exclude an ALP-dr…
