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The ALP Automatic Computing Algorithm, ALPaca, is an open source Python library devoted to studying the phenomenology of Axion-Like Particles (ALPs) with masses in the ranges $m_a \in [0.01 - 10]$ GeV. ALPaca provides a flexible and…

High Energy Physics - Phenomenology · Physics 2025-08-13 Jorge Alda , Marta Fuentes Zamoro , Luca Merlo , Xavier Ponce Díaz , Stefano Rigolin

The detection of very high-energy (VHE) gamma rays from the active galaxy M87 by LHAASO, showing a possible spectral hardening around $20$ TeV, motivates the search for new physics beyond standard emission models. One promising candidate is…

High Energy Astrophysical Phenomena · Physics 2026-04-01 A. Pratts , D Avila Rojas , J. Serna-Franco , M. M. González , R. Alfaro

High energy gamma-rays propagating in external magnetic fields may convert into axion-like particles (ALPs). In this case, the observed gamma-ray spectra are modified by the resulting energy-dependent conversion probability. In this study,…

High Energy Astrophysical Phenomena · Physics 2023-06-13 Qixin Yu , Dieter Horns

Axions and axion-like particles (ALPs) have gained immense attention in searches for beyond Standard Model (BSM) physics. Experiments searching for axions leverage their predicted couplings to Standard Model (SM) particles to look for…

High Energy Physics - Phenomenology · Physics 2026-03-24 Tanmoy Kumar , N. P. S. Mithun , Subhendra Mohanty , Sourov Roy , B. S. Bharath Saiguhan , Santosh Vadawale

The growing interest in axion-like particles (ALPs) stems from the fact that they provide successful theoretical explanations of physics phenomena, from the anomaly of the CP-symmetry conservation in strong interactions to the observation…

High Energy Astrophysical Phenomena · Physics 2021-06-08 Ivana Batković , Alessandro De Angelis , Michele Doro , Marina Manganaro

Axions and axion-like-particles (ALPs) are characterised by their two-photon coupling, which entails so-called photon-ALP oscillations as photons propagate through a magnetic field. These oscillations lead to distinctive signatures in the…

High Energy Physics - Phenomenology · Physics 2023-12-11 M. Kachelriess , J. Tjemsland

In many approaches to describe physics beyond the standard model, light Nambu-Goldstone bosons (named axion-like particles or ALPS for their similarity with the axion) are predicted to exist. For ALPs with a mass of neV, photon-ALPs…

High Energy Physics - Phenomenology · Physics 2017-11-27 Jhilik Majumdar , Francesca Calore , Dieter Horns

Axion-like particles (ALPs) can oscillate to photons and vice versa in electromagnetic fields. The photon-ALP oscillation provides an attractive solution to the apparent transparency of the Universe to TeV photons. The allowed parameter…

High Energy Physics - Phenomenology · Physics 2019-06-26 Yun-Feng Liang , Cun Zhang , Zi-Qing Xia , Lei Feng , Qiang Yuan , Yi-Zhong Fan

Background radiation fields pervade the Universe, and above a certain energy any $\gamma$-ray flux emitted by an extragalactic source should be attenuated due to $e^+e^-$ pair production. The opacity could be alleviated if photons…

High Energy Astrophysical Phenomena · Physics 2014-09-05 Manuel Meyer , Daniele Montanino , Jan Conrad

We have recently shown that axions and axion-like particles (ALPs) may emit an observable stochastic gravitational wave (GW) background when they begin to oscillate in the early universe. In this note, we identify the regions of ALP…

High Energy Physics - Phenomenology · Physics 2020-12-23 Camila S. Machado , Wolfram Ratzinger , Pedro Schwaller , Ben A. Stefanek

Axion-like particles (ALPs) belong to a class of new pseudoscalar particles that generically couple to photons, opening the possibility of oscillations from photons into ALPs in an external magnetic field. Having witnessed the turbulence of…

High Energy Astrophysical Phenomena · Physics 2013-11-14 Denis Wouters , Pierre Brun

Hypothetical axion-like particles (ALPs) are of interest because of their potential to act as dark matter or to reveal information about yet undiscovered fundamental constituents of matter. Such particles can be created when photons…

High Energy Astrophysical Phenomena · Physics 2025-08-19 Denys Malyshev , Lidiia Zadorozhna , Yuriy Bidasyuk , Andrea Santangelo , Oleg Ruchayskiy

Studies of axion-like particles (ALPs) commonly focus on a single type of interaction, for example couplings only to photons. Most ALP models however predict correlations between different couplings, which change the phenomenology in…

High Energy Physics - Phenomenology · Physics 2020-07-15 Fatih Ertas , Felix Kahlhoefer

Very high energy gamma-rays are expected to be absorbed by the extragalactic background light over cosmological distances via the process of electron-positron pair production. Recent observations of cosmologically distant gamma-ray emitters…

Astrophysics · Physics 2008-11-26 Melanie Simet , Dan Hooper , Pasquale D. Serpico

Axion-like particles (ALPs) are interesting dark matter candidates both from the theoretical as well as from the experimental perspective. Usually they are motivated as pseudo-Nambu-Goldstone bosons. In this case one of their most important…

High Energy Physics - Phenomenology · Physics 2018-08-01 Gonzalo Alonso-Álvarez , Joerg Jaeckel

We investigate axion-like particles (ALPs) in the context of asymptotically safe gravity-matter systems. The ALP-photon interaction, which facilitates experimental searches for ALPs, is a dimension-5-operator. Quantum fluctuations of…

General Relativity and Quantum Cosmology · Physics 2022-06-07 Gustavo P. de Brito , Astrid Eichhorn , Rafael R. Lino dos Santos

Axion-like particles (ALPs) can induce localised oscillatory modulations in the spectra of photon sources passing through astrophysical magnetic fields. Ultra-deep Chandra observations of the Perseus cluster contain over $5 \times 10^5$…

High Energy Astrophysical Phenomena · Physics 2017-10-04 Marcus Berg , Joseph P. Conlon , Francesca Day , Nicholas Jennings , Sven Krippendorf , Andrew J. Powell , Markus Rummel

Gamma-ray photons can convert into axion-like particles (ALPs) and vice versa when interacting with astrophysical magnetic fields. The conversions of ALPs may have important implications for astrophysics since they would imprint…

High Energy Astrophysical Phenomena · Physics 2013-05-02 Miguel A. Sanchez-Conde , Stefan Funk , Frank Krennrich , Amanda Weinstein

Oscillations between photons and axion-like particles (ALP) travelling in intergalactic magnetic fields have been invoked to explain a number of astrophysical phenomena, or used to constrain ALP properties using observations. One example is…

High Energy Astrophysical Phenomena · Physics 2016-06-15 Chen Wang , Dong Lai

Axion-Like Particles (ALPs), if exist in nature, are expected to mix with photons in the presence of an external magnetic field. The energy range of photons which undergo strong mixing with ALPs depends on the ALP mass, on its coupling with…

High Energy Astrophysical Phenomena · Physics 2013-11-13 Olga Mena , Soebur Razzaque