[Paper Review] BSM photon interaction for ALPS-II and beyond

Babette Döbrich|arXiv (Cornell University)|Dec 12, 2012

Dark Matter and Cosmic Phenomena14 references3 citations

TL;DR

This paper presents the ALPS-II experiment, a next-generation light-shining-through-a-wall setup at DESY designed to probe axion-like particles and hidden photons via photon-ALP conversion in strong magnetic fields. By enhancing laser power, employing resonant regeneration cavities, and using ultra-sensitive detectors, ALPS-II aims to improve sensitivity by up to 3,082× over ALPS-I, enabling discovery of weakly coupled particles beyond the Standard Model and probing asymptotically safe quantum gravity via photon-photon scattering.

ABSTRACT

High-intensity photon beams can provide for a viable probe for many particles of Standard Model extensions. This workshop contribution briefly reviews the status of the second stage of the Any Light Particle Search (ALPS-II) at DESY, an experiment of the light-shining-through-a-wall type, as well as an idea to test asymptotically safe quantum gravity in a photon-scattering experiment.

Motivation & Objective

• To extend the sensitivity of laboratory-based searches for weakly interacting slim particles (WISPs) such as axion-like particles and hidden photons.
• To test the viability of a high-power, resonant regeneration cavity setup for photon regeneration in light-shining-through-a-wall experiments.
• To explore parameter spaces relevant to dark matter, dark radiation, and string-scale physics.
• To assess the feasibility of using laser-based setups to probe quantum gravity effects, particularly asymptotically safe gravity.
• To develop a background-free detection system using transition edge sensors for improved signal sensitivity.

Proposed method

• Utilize a 468 Tm magnetic field formed by 20 HERA dipoles to enhance photon-ALP conversion efficiency in the generation region.
• Implement resonant regeneration cavities in both the generation and regeneration regions, locked to each other to increase effective photon flux.
• Operate the laser at 1064 nm instead of 532 nm to improve long-term cavity mirror stability and reduce thermal noise.
• Employ a nearly background-free transition edge sensor for high detection efficiency, with a CCD as fallback.
• Use gas-filled vacuum tubes to close conversion probability minima at low magnetic field gradients.
• Apply scaling laws to estimate sensitivity gains: $ g_{a\gamma} \propto (BL)^{-1} $, $ P_{\text{laser}}^{-1/4} $, $ P_{\text{RC}}^{-1/4} $, and $ DC^{1/8} $.

Experimental results

Research questions

• RQ1 Can ALPS-II achieve a sensitivity improvement of over 3,000× for axion-like particles compared to ALPS-I?
• RQ2 Can resonant regeneration cavities be stably locked in the optical regime to enhance effective laser power?
• RQ3 Can the transition edge sensor achieve sufficient detection efficiency and background suppression for sub-eV WISP searches?
• RQ4 Is the 468 Tm magnetic field configuration feasible using repurposed HERA dipoles and straightened beam pipes?
• RQ5 Can laser-based experiments probe signatures of asymptotically safe quantum gravity via enhanced photon-photon scattering?

Key findings

• ALPS-IIc is projected to achieve a sensitivity gain of up to 3,082× for axion-like particles compared to ALPS-I, primarily driven by increased magnetic field length (468 Tm) and enhanced laser power (150 kW).
• The resonant regeneration cavity setup is expected to boost sensitivity by a factor of 14, based on power build-up in the regeneration cavity.
• The use of 1064 nm infrared light instead of 532 nm green light is expected to improve cavity stability and reduce thermal noise, contributing to a 1.2× gain in effective photon flux.
• The transition edge sensor is expected to improve detection efficiency and reduce background, contributing to a 0.96× gain in sensitivity compared to ALPS-I.
• For hidden photons, the sensitivity gain is estimated at 147×, primarily due to the increased magnetic field length and improved detection system.
• The experiment is designed in three stages: ALPS-IIa (10m+10m, no magnets) to test optics and cavity locking, ALPS-IIb (100m+100m, no magnets) for long baseline operation, and ALPS-IIc (with magnets) for axion-like particle searches.