J. Galán

Towards a new generation axion helioscope

We study the feasibility of a new generation axion helioscope, the most ambitious and promising detector of solar axions to date. We show that large improvements in magnetic field volume, x-ray focusing optics and detector backgrounds are possible beyond those achieved in the CERN Axion Solar Telescope (CAST). For hadronic models, a sensitivity to the axion-photon coupling of gaγ few × 10−12 GeV−1 is conceivable, 1–1.5 orders of magnitude beyond the CAST sensitivity. If axions also couple to electrons, the Sun produces a larger flux for the same value of the Peccei-Quinn scale, allowing one to probe a broader class of models. Except for the axion dark matter searches, this experiment will be the most sensitive axion search ever, reaching or surpassing the stringent bounds from SN1987A and possibly testing the axion interpretation of anomalous white-dwarf cooling that predicts ma of a few meV. Beyond axions, this new instrument will probe entirely unexplored ranges of parameters for a large variety of axion-like particles (ALPs) and other novel excitations at the low-energy frontier of elementary particle physics.

Search for Sub-eV Mass Solar Axions by the CERN Axion Solar Telescope with 3He Buffer Gas

S. Aune, K. Barth, A. Belov, S. Borghi, ∗ H. Bräuninger, G. Cantatore, J. M. Carmona, S. A. Cetin, J. I. Collar, T. Dafni, M. Davenport, C. Eleftheriadis, N. Elias, C. Ezer, G. Fanourakis, E. Ferrer-Ribas, P. Friedrich, J. Galán, J. A. Garćıa, A. Gardikiotis, E. N. Gazis, T. Geralis, I. Giomataris, S. Gninenko, H. Gómez, E. Gruber, T. Guthörl, R. Hartmann, † F. Haug, M. D. Hasinoff, D. H. H. Hoffmann, F. J. Iguaz, ‡ I. G. Irastorza, J. Jacoby, K. Jakovčić, M. Karuza, K. Königsmann, R. Kotthaus, M. Krčmar, M. Kuster, 16, § B. Lakić, ¶ J. M. Laurent, A. Liolios, A. Ljubičić, V. Lozza, G. Lutz, † G. Luzón, J. Morales, ∗∗ T. Niinikoski, †† A. Nordt, 16, ‡‡ T. Papaevangelou, M. J. Pivovaroff, G. Raffelt, T. Rashba, H. Riege, A. Rodŕıguez, M. Rosu, J. Ruz, 2 I. Savvidis, P. S. Silva, S. K. Solanki, L. Stewart, A. Tomás, M. Tsagri, ‡‡ K. van Bibber, §§ T. Vafeiadis, 9, 12 J. Villar, J. K. Vogel, 20, ¶¶ S. C. Yildiz, and K. Zioutas 12

Conceptual design of the International Axion Observatory (IAXO)

The International Axion Observatory (IAXO) will be a forth generation axion helioscope. As its primary physics goal, IAXO will look for axions or axion-like particles (ALPs) originating in the Sun via the Primakoff conversion of the solar plasma photons. In terms of signal-to-noise ratio, IAXO will be about 4–5 orders of magnitude more sensitive than CAST, currently the most powerful axion helioscope, reaching sensitivity to axion-photon couplings down to a few × 10−12 GeV−1 and thus probing a large fraction of the currently unexplored axion and ALP parameter space. IAXO will also be sensitive to solar axions produced by mechanisms mediated by the axion-electron coupling gae with sensitivity — for the first time — to values of gae not previously excluded by astrophysics. With several other possible physics cases, IAXO has the potential to serve as a multi-purpose facility for generic axion and ALP research in the next decade. In this paper we present the conceptual design of IAXO, which follows the layout of an enhanced axion helioscope, based on a purpose-built 20 m-long 8-coils toroidal superconducting magnet. All the eight 60cm-diameter magnet bores are equipped with focusing x-ray optics, able to focus the signal photons into ~ 0.2 cm2 spots that are imaged by ultra-low-background Micromegas x-ray detectors. The magnet is built into a structure with elevation and azimuth drives that will allow for solar tracking for ~ 12 h each day.

Search for solar axions by the CERN axion solar telescope with 3He buffer gas: closing the hot dark matter gap.

Introduction.—The most promising method to searchfor axions and axion-likeparticles (ALPs) [1–4], low-massbosons with a two-photon interaction vertex, is their con-version to photons in macroscopic magnetic fields [5–7].This approach includes the search for solar axions by thehelioscope technique [8–15], photon regeneration exper-iments (“shining light through a wall”) [16–18], axion-photon conversion in astrophysical B fields [19–22], andthe search for galactic axion dark matter [23–27].One limiting factor in any of these efforts is the mo-mentum difference between freely propagating photonsand axions caused by the axion mass m

The NEXT experiment

Neutrinoless double beta decay measurements are the most promising experiments both to reveal the Majorana nature of the neutrino and to set a value for its mass. The NEXT project propose to build a High pressure Xenon TPC in the Canfranc Underground Laboratory (Huesca, Spain) to measure double-beta decay of 136Xe, both normal and neutrinoless, with a source mass of 100 kg of enriched xenon.

Readout technologies for directional WIMP Dark Matter detection

The measurement of the direction of WIMP-induced nuclear recoils is a compelling but technologically challenging strategy to provide an unambiguous signature of the detection of Galactic dark matter. Most directional detectors aim to reconstruct the dark-matter-induced nuclear recoil tracks, either in gas or solid targets. The main challenge with directional detection is the need for high spatial resolution over large volumes, which puts strong requirements on the readout technologies. In this paper we review the various detector readout technologies used by directional detectors. In particular, we summarize the challenges, advantages and drawbacks of each approach, and discuss future prospects for these technologies.

Gaseous time projection chambers for rare event detection: results from the T-REX project. II. Dark matter

As part of the T-REX project, a number of R&D and prototyping activities have been carried out during the last years to explore the applicability of gaseous Time Projection Chambers (TPCs) with Micromesh Gas Structures (Micromegas) in rare event searches like double beta decay, axion research and low-mass WIMP searches. While in the companion paper we focus on double beta decay, in this paper we focus on the results regarding the search for dark matter candidates, both axions and WIMPs. Small (few cm wide) ultra-low background Micromegas detectors are used to image the axion-induced x-ray signal expected in axion helioscopes like the CERN Axion Solar Telescope (CAST) experiment. Background levels as low as 0.8 × 10−6 counts keV−1 cm−2 s−1 have already been achieved in CAST while values down to ~10−7 counts keV−1 cm−2 s−1 have been obtained in a test bench placed underground in the Laboratorio Subterraneo de Canfranc (LSC). Prospects to consolidate and further reduce these values down to ~10−8 counts keV−1 cm−2 s−1 will be described. Such detectors, placed at the focal point of x-ray telescopes in the future International Axion Observatory (IAXO), would allow for 105 better signal-to-noise ratio than CAST, and search for solar axions with gaγ down to few 1012 GeV−1, well into unexplored axion parameter space. In addition, a scaled-up version of these TPCs, properly shielded and placed underground, can be competitive in the search for low-mass WIMPs. The TREX-DM prototype, with ~ 0.300 kg of Ar at 10 bar, or alternatively ~ 0.160 kg of Ne at 10 bar, and energy threshold well below 1 keV, has been built to test this concept. We will describe the main technical solutions developed, as well as the results from the commissioning phase on surface. The anticipated sensitivity of this technique might reach ~10−44 cm2 for low mass (<10 GeV) WIMPs, well beyond current experimental limits in this mass range.

New solar axion search using the CERN Axion Solar Telescope with He 4 filling

M. Arik, a S. Aune, K. Barth, A. Belov, H. Bräuninger, J. Bremer, V. Burwitz, G. Cantatore, J. M. Carmona, S. A. Cetin, J. I. Collar, E. Da Riva, T. Dafni, M. Davenport, A. Dermenev, C. Eleftheriadis, N. Elias, b G. Fanourakis, E. Ferrer-Ribas, J. Galán, J. A. Garćıa, c A. Gardikiotis, J. G. Garza, E. N. Gazis, T. Geralis, E. Georgiopoulou, I. Giomataris, S. Gninenko, M. Gómez Marzoa, d M. D. Hasinoff, D. H. H. Hoffmann, F. J. Iguaz, I. G. Irastorza, J. Jacoby, K. Jakovčić, M. Karuza, 17 M. Kavuk, a M. Krčmar, M. Kuster, 14, e B. Lakić, J. M. Laurent, A. Liolios, A. Ljubičić, G. Luzón, S. Neff, T. Niinikoski, f A. Nordt, 14, b I. Ortega, 3 T. Papaevangelou, M. J. Pivovaroff, G. Raffelt, A. Rodŕıguez, M. Rosu, J. Ruz, I. Savvidis, I. Shilon, 3, g S. K. Solanki, h L. Stewart, A. Tomás, T. Vafeiadis, 9, 11 J. Villar, J. K. Vogel, S. C. Yildiz, i and K. Zioutas 11

A Piggyback resistive Micromegas

A novel read-out architecture has been developed for the Micromegas detector. The anode element is made of a resistive layer on a ceramic substrate. The detector part is entirely separated from the read-out element. Without significant loss, signals are transmitted by capacitive coupling to the read-out pads. The detector provides high gas gain, good energy resolution and the resistive layer assures spark protection to the electronics. This assembly could be combined with modern pixel array electronic ASICs. This readout organization is free on how the pixels are designed, arranged and connected. We present first results taken with a Medipix2 read-out chip.

Status of R&D on Micromegas for Rare Event Searches : The T-REX project

The T-REX project aims at developing novel readout techniques for Time Projection Chambers in experiments searching for rare events. The enhanced performance of the latest Micromegas readouts in issues like energy resolution, gain stability, homogeneity, material budget, combined with low background techniques, is opening new windows of opportunity for their application in this field. Here we review the latest results regarding the use and prospects of Micromegas readouts in axion physics (CAST and the future helioscope), as well as the R&D carried out within NEXT, to search for the neutrinoless double-beta decay.