K. Altenmüller’s research while affiliated with University of Zaragoza and other places


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Publications (112)


A new upper limit on the axion-photon coupling with an extended CAST run with a Xe-based Micromegas detector
  • Preprint
  • File available

June 2024

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88 Reads

CAST Collaboration

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K. Altenmüller

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V. Anastassopoulos

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[...]

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Hypothetical axions provide a compelling explanation for dark matter and could be emitted from the hot solar interior. The CERN Axion Solar Telescope (CAST) has been searching for solar axions via their back conversion to X-ray photons in a 9-T 10-m long magnet directed towards the Sun. We report on an extended run with the IAXO (International Axion Observatory) pathfinder detector, doubling the previous exposure time. The detector was operated with a xenon-based gas mixture for part of the new run, providing technical insights for future detector configurations in IAXO. No counts are detected in the 95\% signal-encircling region during the new run, while one is expected. The new data improve the axion-photon coupling limit to 5.7×1011\times 10^{-11}\,GeV1^{-1} at 95\% C.L., the most restrictive experimental limit to date.

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FIG. 1. The result of the Monte Carlo numerical simulations for the azimuthal distribution of axion flux Pa(θ) on the surface of the Earth, adopted from [22]. A relative orientation of the Earth's axis of rotation and DM galactic wind generates the flux asymmetry sensitive to the latitude θ, which consequently leads to the daily modulation effect.
FIG. 5. Time series (left) and Lomb Scargle periodograms (right) for data taken between 13/08/2020 and 20/09/2020 with cavity 3 and B = 8.8 T. The results for the ambient environmental temperature as well as the cavity temperature are also shown.
FIG. 6. Time series (left) and Lomb Scargle periodograms (right) for data taken between 13/07/2020 and 13/08/2020 with cavity 2 and B = 0 T. The results for the ambient environmental temperature as well as the cavity temperature are also shown.
The daily modulations and broadband strategy in axion searches. An application with CAST-CAPP detector

May 2024

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62 Reads

It has been previously advocated that the presence of the daily and annual modulations of the axion flux on the Earth's surface may dramatically change the strategy of the axion searches. The arguments were based on the so-called Axion Quark Nugget (AQN) dark matter model which was originally put forward to explain the similarity of the dark and visible cosmological matter densities ΩdarkΩvisible\Omega_{\rm dark}\sim \Omega_{\rm visible}. In this framework, the population of galactic axions with mass 106eVma103eV 10^{-6} {\rm eV}\lesssim m_a\lesssim 10^{-3}{\rm eV} and velocity va103c\langle v_a\rangle\sim 10^{-3} c will be accompanied by axions with typical velocities va0.6c\langle v_a\rangle\sim 0.6 c emitted by AQNs. Furthermore, in this framework, it has also been argued that the AQN-induced axion daily modulation (in contrast with the conventional WIMP paradigm) could be as large as (1020)%(10-20)\%, which represents the main motivation for the present investigation. We argue that the daily modulations along with the broadband detection strategy can be very useful tools for the discovery of such relativistic axions. The data from the CAST-CAPP detector have been used following such arguments. Unfortunately, due to the dependence of the amplifier chain on temperature-dependent gain drifts and other factors, we could not conclusively show the presence or absence of a dark sector-originated daily modulation. However, this proof of principle analysis procedure can serve as a reference for future studies.


Ultra low background Micromegas detectors for BabyIAXO solar axion search

October 2023

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30 Reads

Journal of Instrumentation

The International AXion Observatory (IAXO) is a large scale axion helioscope that will look for axions and axion-like particles produced in the Sun with unprecedented sensitivity. BabyIAXO is an intermediate experimental stage that will be hosted at DESY (Germany) and that will test all IAXO subsystems serving as a prototype for IAXO but at the same time as a fully-fledged helioscope with potential for discovery. One of the crucial components of the project is the ultra-low background X-ray detectors that will image the X-ray photons produced by axion conversion in the experiment. The baseline detection technology for this purpose are Micromegas (Microbulk) detectors. We will show the quest and the strategy to attain the very challenging levels of background targeted for BabyIAXO that need a multi-approach strategy coming from ground measurements, screening campaigns of components of the detector, underground measurements, background models, in-situ background measurements as well as powerful rejection algorithms. First results from the commissioning of the BabyIAXO prototype will be shown.


Ultra low background Micromegas detectors for BabyIAXO solar axion search

March 2023

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28 Reads

The International AXion Observatory (IAXO) is a large scale axion helioscope that will look for axions and axion-like particles produced in the Sun with unprecedented sensitivity. BabyIAXO is an intermediate experimental stage that will be hosted at DESY (Germany) and that will test all IAXO subsystems serving as a prototype for IAXO but at the same time as a fully-fledged helioscope with potential for discovery. One of the crucial components of the project is the ultra-low background X-ray detectors that will image the X-ray photons produced by axion conversion in the experiment. The baseline detection technology for this purpose are Micromegas (Microbulk) detectors. We will show the quest and the strategy to attain the very challenging levels of background targeted for BabyIAXO that need a multi-approach strategy coming from ground measurements, screening campaigns of components of the detector, underground measurements, background models, in-situ background measurements as well as powerful rejection algorithms. First results from the commissioning of the BabyIAXO prototype will be shown.







X-ray detectors for the BabyIAXO solar axion search

December 2022

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29 Reads

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3 Citations

Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment

BabyIAXO is a helioscope under construction to search for an emission of the axion particle from the Sun. At the same time it serves as an intermediate stage towards the International Axion Observatory (IAXO). An integral component of this experiment is a low background X-ray detector with a high efficiency in the 1–10 keV energy range. Micromegas detectors are considered as baseline technology for BabyIAXO thanks to the relatively high efficiency and very low background level. Other detector technologies developed to reach better energy resolution while maintaining high efficiency and low background level are also under study. In this paper, we review the BabyIAXO design and present the analysis of data taken with the prototype of an IAXO Micromegas detector. A background level of 8.8×10−7counts keV−1cm−2s−1 was reached.


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Citations (48)


... Micromegas detectors at present offer even lower background rates, currently demonstrating more than two orders of magnitude reduction compared to the previously mentioned (unshielded) MMC rate [72]. This brings us closer to our assumption and the IAXO target of an effectively background-free experiment. ...

Reference:

Axion helioscopes as solar thermometers
X-ray detectors for the BabyIAXO solar axion search
  • Citing Article
  • December 2022

Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment

... The colored band region depicts the allowed region from our analysis with the uncertainty due to parametric resonance and numerical precision. The haloscope experiments [63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78] have already excluded some of the parameter space for axion masses of O(10 −6 ) eV as shown in red. The dashed line refers to the projected sensitivity from future haloscope experiments [77,[79][80][81][82][83], which is expected to cover most of the allowed parameter space corresponding to m a > O(10 −12 ) eV. ...

Search for Dark Matter Axions with CAST-CAPP

... There are several types of search strategies depending on the source of the axion. These include (i) haloscope searches for dark-matter axions in the galactic halo (CAPP [28][29][30][31][32], ADMX [33][34][35], HAYSTAC [36][37][38], QUAX [39][40][41], ORGAN [42,43], MADMAX [44][45][46], DM Radio [47], CAST-CAPP [48], FLASH [49], etc.), (ii) helioscopes pointing at the Sun to look for solar axions (CAST [50] and IAXO [51]), and (iii) light-shining-through-the-wall schemes, which are configured to generate and detect axions in the lab (OSQAR [52] and ALPS (II) [53,54]). Among these, the cavity haloscope method provides the most sensitive approach, particularly in the microwave region under the assumption that axions contribute significantly to the local density of dark matter. ...

Search for Dark Matter Axions with CAST-CAPP
Nature Communications

... Recently the Borexino collaboration [1] reported at Neutrino2020 the results of first detection of solar neutrinos from CNO cycle and published the arXiv [2]. They used of two types of analysis of experimental data: Counting Analysis and Multivariable fit. ...

First Detection of Solar Neutrinos from the CNO Cycle with Borexino
  • Citing Article
  • September 2022

Moscow University Physics Bulletin

... Recently the concept Theia [74] was put forward, which proposes to enhance existing liquid scintillators with cuttingedge photon detectors to simultaneously detect Cherenkov light alongside scintillation. This signal -which is now utilised by Borexino [75][76][77] -enables directional sensitivity at lower energies than has been possible so far in the field. The concept we propose here would enable significantly lower energy and directionality thresholds for both nuclear and electron recoils, and could potentially enable a more precise and direct measurement of the incoming neutrino direction. ...

First Directional Measurement of Sub-MeV Solar Neutrinos with Borexino

Physical Review Letters

... Recently the concept Theia [74] was put forward, which proposes to enhance existing liquid scintillators with cuttingedge photon detectors to simultaneously detect Cherenkov light alongside scintillation. This signal -which is now utilised by Borexino [75][76][77] -enables directional sensitivity at lower energies than has been possible so far in the field. The concept we propose here would enable significantly lower energy and directionality thresholds for both nuclear and electron recoils, and could potentially enable a more precise and direct measurement of the incoming neutrino direction. ...

Correlated and integrated directionality for sub-MeV solar neutrinos in Borexino

Physical Review D

... Further, the physical insight that isotope production often happens in hadronic showers with multiple neutrons will also be important for scintillator detectors like JUNO [36][37][38], which is also at a shallower depth. As detailed in the Appendices, our insight significantly generalizes upon a single-neutron technique used to reject 11 C backgrounds in scintillator detectors [39][40][41][42]. ...

Identification of the cosmogenic 11^{11}C background in large volumes of liquid scintillators with Borexino

The European Physical Journal C

... Background events induced in the vessel walls by cosmic muons and the external gamma radioactivity are efficiently suppressed by electrostatic and magnetic shielding [16,17]. A contribution of the Penning trap between the main spectrometer and the pre-spectrometer to the background rate was Fig. 1 The KATRIN main spectrometer with its system of air coils and inner electrodes and illustration of the MAC-E-Filter principle studied in detail and a dedicated electron catcher system is used to remove trapped electrons from the inter-spectrometer region [18]. The focal-plane detector of KATRIN contributes ∼ 35 mcps to the background rate due to radioactivity and cosmic muons. ...

Suppression of Penning discharges between the KATRIN spectrometers
  • Citing Article
  • September 2020

... KATRIN features a 10 11 Bq high-activity windowless gaseous molecular tritium source, where the β-electrons are emitted and are magnetically guided through the setup [23] towards the detector. In the KATRIN spectrometer, the electrons' momenta are magnetically collimated and the electrons are electrostatically filtered based on their kinetic energy with a filter width of O(1 eV) [24][25][26]. ...

The design, construction, and commissioning of the KATRIN experiment

Journal of Instrumentation

... Recently, a new upper limit of 0.45 eV (90 % CL) based on the first five science runs, with 259 measurement days, was reported [12]. The sensitivity of KATRIN is achieved via the high statistics measurement of the tritium β-decay spectrum near its endpoint with eV energy resolution and excellent control of systematic uncertainties [13]. The ultimate statistical sensitivity of KATRIN depends strongly on the background rate. ...

Analysis methods for the first KATRIN neutrino-mass measurement

Physical Review D