Gonzalo Alonso-Álvarez
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
Research Interests
Gonzalo Alonso-Álvarez has a total of 138 co-authors. Here are the top co-authors by number of shared publications:
- James M. Cline
McGill University
9 shared publications - Joerg Jaeckel
Universität Heidelberg
8 shared publications - Miguel Escudero
CERN
6 shared publications - Gilly Elor
Department of Physics, University of Washington, Seattle, Washington, D.C. 98195, USA
5 shared publications - Tianzhuo Xiao
Department of Physics McGill University Trottier Space Institute 3600 Rue University H3A 2T8 Montréal QC Canada
4 shared publications - David Curtin
University of Toronto
3 shared publications
Latest Publications
- 25 March 2026
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 136 (12) , 121802
Wideband Search for Axionlike Dark Matter Using Octupolar Nuclei in a Crystal
Most of the matter in the Universe is in the form of dark matter, which has evaded detection so far. Ultralight axionlike particles (ALPs) are a class of dark matter candidates that produce measurable signatures in the form of oscillating violations of discrete symmetries in nuclei. We report results from a search for an oscillating parity-odd time-reversal-odd nuclear Schiff moment of ^{153}Eu ions in a crystal, which leads to constraints on ALP-gluon coupling strength across a wide band spanning eight decades in ALP mass.
- 25 March 2026
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 136 (12) , 121802
Wideband Search for Axionlike Dark Matter Using Octupolar Nuclei in a Crystal
Most of the matter in the Universe is in the form of dark matter, which has evaded detection so far. Ultralight axionlike particles (ALPs) are a class of dark matter candidates that produce measurable signatures in the form of oscillating violations of discrete symmetries in nuclei. We report results from a search for an oscillating parity-odd time-reversal-odd nuclear Schiff moment of ^{153}Eu ions in a crystal, which leads to constraints on ALP-gluon coupling strength across a wide band spanning eight decades in ALP mass.
- Open Access
- 10 June 2025
- Published by Springer Nature in The European Physical Journal C
- Vol. 85 (6) , 1-8
Dark photon distortions of NO$\nu $A and T2K neutrino oscillationsDark photons coupling to $$L_\mu -L_\tau $$ lepton number difference are a highly studied light dark matter candidate, with potential to be discovered through their impact on terrestrial neutrino oscillation experiments. We re-examine this in the light of claimed tensions between the NO $$\nu $$ A and T2K long baseline experiments, also taking into account data from the MINOS experiment. We obtain leading limits on the $$L_\mu -L_\tau $$ gauge coupling $$g'$$ versus dark photon mass $$m_{A'}$$ , improving upon previous bounds by up to a factor of five. We find no statistically significant alleviation of the tension from inclusion of the new physics effect.- 10 June 2025
- Published by Springer Nature in The European Physical Journal C
- Vol. 85 (6) , 1-8
Open AccessDark photon distortions of NO$\nu $A and T2K neutrino oscillationsDark photons coupling to $$L_\mu -L_\tau $$ lepton number difference are a highly studied light dark matter candidate, with potential to be discovered through their impact on terrestrial neutrino oscillation experiments. We re-examine this in the light of claimed tensions between the NO $$\nu $$ A and T2K long baseline experiments, also taking into account data from the MINOS experiment. We obtain leading limits on the $$L_\mu -L_\tau $$ gauge coupling $$g'$$ versus dark photon mass $$m_{A'}$$ , improving upon previous bounds by up to a factor of five. We find no statistically significant alleviation of the tension from inclusion of the new physics effect. - Open Access
- 1 May 2025
- Published by IOP Publishing in Journal of Cosmology and Astroparticle Physics
- Vol. 2025 (05)
Dark astronomy with dark matter detectors
We present a novel way of probing non-gravitational dark matter interactions: dark astronomy, which leverages the dark radiation emitted by dissipative dark sectors. If the mediator of the dark matter self interactions is a dark photon with a small mass that kinetically mixes with the visible photon, the dark radiation flux becomes accessible to underground experiments. We argue that the emission may be dominantly longitudinally polarized, thereby enhancing the sensitivity of direct detection experiments such as XENON and SENSEI to this signal. We introduce a new detection mechanism based on resonant dark-photon-to-photon conversion at the surface of conducting materials, which offers unique directional sensitivity to dark radiation. This mechanism facilitates the development of experiments that combine dark matter detection techniques with methods of traditional astronomy, opening the possibility to map dark radiation sources within our galaxy.
- 1 May 2025
- Published by IOP Publishing in Journal of Cosmology and Astroparticle Physics
- Vol. 2025 (05)
Open AccessDark astronomy with dark matter detectors
We present a novel way of probing non-gravitational dark matter interactions: dark astronomy, which leverages the dark radiation emitted by dissipative dark sectors. If the mediator of the dark matter self interactions is a dark photon with a small mass that kinetically mixes with the visible photon, the dark radiation flux becomes accessible to underground experiments. We argue that the emission may be dominantly longitudinally polarized, thereby enhancing the sensitivity of direct detection experiments such as XENON and SENSEI to this signal. We introduce a new detection mechanism based on resonant dark-photon-to-photon conversion at the surface of conducting materials, which offers unique directional sensitivity to dark radiation. This mechanism facilitates the development of experiments that combine dark matter detection techniques with methods of traditional astronomy, opening the possibility to map dark radiation sources within our galaxy.
- Open Access
Dark Astronomy with Dark Matter Detectors
We present a novel way of probing non-gravitational dark matter interactions: dark astronomy, which leverages the dark radiation emitted by dissipative dark sectors. If the mediator of the dark matter self interactions is a dark photon with a small mass that kinetically mixes with the visible photon, the dark radiation flux becomes accessible to underground experiments. We argue that the emission may be dominantly longitudinally polarized, thereby enhancing the sensitivity of direct detection experiments such as XENON and SENSEI to this signal. We introduce a new detection mechanism based on resonant dark-photon-to-photon conversion at the surface of conducting materials, which offers unique directional sensitivity to dark radiation. This mechanism facilitates the development of experiments that combine dark matter detection techniques with methods of traditional astronomy, opening the possibility to map dark radiation sources within our galaxy.
Open AccessDark Astronomy with Dark Matter Detectors
We present a novel way of probing non-gravitational dark matter interactions: dark astronomy, which leverages the dark radiation emitted by dissipative dark sectors. If the mediator of the dark matter self interactions is a dark photon with a small mass that kinetically mixes with the visible photon, the dark radiation flux becomes accessible to underground experiments. We argue that the emission may be dominantly longitudinally polarized, thereby enhancing the sensitivity of direct detection experiments such as XENON and SENSEI to this signal. We introduce a new detection mechanism based on resonant dark-photon-to-photon conversion at the surface of conducting materials, which offers unique directional sensitivity to dark radiation. This mechanism facilitates the development of experiments that combine dark matter detection techniques with methods of traditional astronomy, opening the possibility to map dark radiation sources within our galaxy.
- Open Access
- 9 July 2024
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 133 (2) , 021401
Self-Interacting Dark Matter Solves the Final Parsec Problem of Supermassive Black Hole Mergers
Evidence for a stochastic gravitational wave (GW) background, plausibly originating from the merger of supermassive black holes (SMBHs), is accumulating with observations from pulsar timing arrays. An outstanding question is how inspiraling SMBHs get past the “final parsec” of separation, where they have a tendency to stall before GW emission alone can make the binary coalesce. We argue that dynamical friction from the dark matter (DM) spike surrounding the black holes is sufficient to resolve this puzzle, if the DM has a self-interaction cross section of order . The same effect leads to a softening of the GW spectrum at low frequencies as suggested by the current data. For collisionless cold DM, the friction deposits so much energy that the spike is disrupted and cannot bridge the final parsec, while for self-interacting DM, the isothermal core of the halo can act as a reservoir for the energy liberated from the SMBH orbits. A realistic velocity dependence, such as generated by the exchange of a massive mediator like a dark photon, is favored to give a good fit to the GW spectrum while providing a large enough core. A similar velocity dependence has been advocated for solving the small-scale structure problems of cold DM.- 9 July 2024
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 133 (2) , 021401
Open AccessSelf-Interacting Dark Matter Solves the Final Parsec Problem of Supermassive Black Hole Mergers
Evidence for a stochastic gravitational wave (GW) background, plausibly originating from the merger of supermassive black holes (SMBHs), is accumulating with observations from pulsar timing arrays. An outstanding question is how inspiraling SMBHs get past the “final parsec” of separation, where they have a tendency to stall before GW emission alone can make the binary coalesce. We argue that dynamical friction from the dark matter (DM) spike surrounding the black holes is sufficient to resolve this puzzle, if the DM has a self-interaction cross section of order . The same effect leads to a softening of the GW spectrum at low frequencies as suggested by the current data. For collisionless cold DM, the friction deposits so much energy that the spike is disrupted and cannot bridge the final parsec, while for self-interacting DM, the isothermal core of the halo can act as a reservoir for the energy liberated from the SMBH orbits. A realistic velocity dependence, such as generated by the exchange of a massive mediator like a dark photon, is favored to give a good fit to the GW spectrum while providing a large enough core. A similar velocity dependence has been advocated for solving the small-scale structure problems of cold DM. - Open Access
- 31 May 2024
- Published by Springer Nature in The European Physical Journal C
- Vol. 84 (5) , 1-6
The first limit on invisible decays of $B_s$ mesons comes from LEPMotivated by the recent evidence for $$B^+\rightarrow K^+\bar{\nu } \nu $$ decays at Belle II, we point out that fully invisible $$B_d$$ and $$B_s$$ meson decays are strongly constrained by LEP. A reinterpretation of an old inclusive ALEPH search for b-hadron decays with large missing energy allows us to place the limits $$\textrm{Br}(B_d \rightarrow \textrm{invisible}) < 1.4\times 10^{-4}$$ and $$\textrm{Br}(B_s \rightarrow \textrm{invisible}) < 5.6\times 10^{-4}$$ , both at $$90\%$$ CL. The $$B_d$$ limit is only a factor of 6 looser than the world-leading one provided by the BaBar collaboration, while the $$B_s$$ one is the first limit in the literature on this decay mode. These results are relevant in the context of new light states coupled to quarks and exemplify the power of a future Tera-Z factory at FCC-ee to look for B meson decays containing missing energy.- 31 May 2024
- Published by Springer Nature in The European Physical Journal C
- Vol. 84 (5) , 1-6
Open AccessThe first limit on invisible decays of $B_s$ mesons comes from LEPMotivated by the recent evidence for $$B^+\rightarrow K^+\bar{\nu } \nu $$ decays at Belle II, we point out that fully invisible $$B_d$$ and $$B_s$$ meson decays are strongly constrained by LEP. A reinterpretation of an old inclusive ALEPH search for b-hadron decays with large missing energy allows us to place the limits $$\textrm{Br}(B_d \rightarrow \textrm{invisible}) < 1.4\times 10^{-4}$$ and $$\textrm{Br}(B_s \rightarrow \textrm{invisible}) < 5.6\times 10^{-4}$$ , both at $$90\%$$ CL. The $$B_d$$ limit is only a factor of 6 looser than the world-leading one provided by the BaBar collaboration, while the $$B_s$$ one is the first limit in the literature on this decay mode. These results are relevant in the context of new light states coupled to quarks and exemplify the power of a future Tera-Z factory at FCC-ee to look for B meson decays containing missing energy. - Open Access
- 7 May 2024
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2024 (5) , 1-43
Baryogenesis through asymmetric reheating in the mirror twin Higgs
We present the νϕMTH, a Mirror Twin Higgs (MTH) model realizing asymmetric reheating, baryogenesis and twin-baryogenesis through the out-of-equilibrium decay of a right-handed neutrino without any hard $${\mathbb{Z}}_{2}$$ breaking. The MTH is the simplest Neutral Naturalness solution to the little hierarchy problem and predicts the existence of a twin dark sector related to the Standard Model (SM) by a $${\mathbb{Z}}_{2}$$ symmetry that is only softly broken by a higher twin Higgs vacuum expectation value. The asymmetric reheating cools the twin sector compared to the visible one, thus evading cosmological bounds on ∆N eff. The addition of (twin-)colored scalars allows for the generation of the visible baryon asymmetry and, by the virtue of the $${\mathbb{Z}}_{2}$$ symmetry, also results in the generation of a twin baryon asymmetry. We identify a unique scenario with top-philic couplings for the new scalars that can satisfy all cosmological, proton decay and LHC constraints; yield the observed SM baryon asymmetry; and generate a wide range of possible twin baryon DM fractions, from negligible to unity. The viable regime of the theory contains several hints as to the possible structure of the Twin Higgs UV completion. Our results motivate the search for the rich cosmological and astrophysical signatures of twin baryons, and atomic dark matter more generally, at cosmological, galactic and stellar scales.- 7 May 2024
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2024 (5) , 1-43
Open AccessBaryogenesis through asymmetric reheating in the mirror twin Higgs
We present the νϕMTH, a Mirror Twin Higgs (MTH) model realizing asymmetric reheating, baryogenesis and twin-baryogenesis through the out-of-equilibrium decay of a right-handed neutrino without any hard $${\mathbb{Z}}_{2}$$ breaking. The MTH is the simplest Neutral Naturalness solution to the little hierarchy problem and predicts the existence of a twin dark sector related to the Standard Model (SM) by a $${\mathbb{Z}}_{2}$$ symmetry that is only softly broken by a higher twin Higgs vacuum expectation value. The asymmetric reheating cools the twin sector compared to the visible one, thus evading cosmological bounds on ∆N eff. The addition of (twin-)colored scalars allows for the generation of the visible baryon asymmetry and, by the virtue of the $${\mathbb{Z}}_{2}$$ symmetry, also results in the generation of a twin baryon asymmetry. We identify a unique scenario with top-philic couplings for the new scalars that can satisfy all cosmological, proton decay and LHC constraints; yield the observed SM baryon asymmetry; and generate a wide range of possible twin baryon DM fractions, from negligible to unity. The viable regime of the theory contains several hints as to the possible structure of the Twin Higgs UV completion. Our results motivate the search for the rich cosmological and astrophysical signatures of twin baryons, and atomic dark matter more generally, at cosmological, galactic and stellar scales. - Open Access
- 2 February 2024
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2024 (2) , 1-25
Nonabelian kinetic mixing in a confining phase: a framework for composite dark photons
Dark matter from a hidden sector with SU(N) gauge symmetry can have a nonabelian kinetic mixing portal with the standard model. The dark photon becomes massive in the confining phase without the need for spontaneous symmetry breaking. Depending on the particle content of the dark sector, there can be two or more composite vectors that get kinetic mixing through a heavy mediator particle X. This provides a model of composite dark photons giving a portal for direct detection of dark baryons. Avoiding exotic charged relics requires additional couplings allowing X to decay to dark quarks and standard model fields, leading to further portals between the dark matter and the standard model. We comprehensively study the constraints on such models from colliders, rare decays, direct detection, and big bang nucleosynthesis.
- 2 February 2024
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2024 (2) , 1-25
Open AccessNonabelian kinetic mixing in a confining phase: a framework for composite dark photons
Dark matter from a hidden sector with SU(N) gauge symmetry can have a nonabelian kinetic mixing portal with the standard model. The dark photon becomes massive in the confining phase without the need for spontaneous symmetry breaking. Depending on the particle content of the dark sector, there can be two or more composite vectors that get kinetic mixing through a heavy mediator particle X. This provides a model of composite dark photons giving a portal for direct detection of dark baryons. Avoiding exotic charged relics requires additional couplings allowing X to decay to dark quarks and standard model fields, leading to further portals between the dark matter and the standard model. We comprehensively study the constraints on such models from colliders, rare decays, direct detection, and big bang nucleosynthesis.
- Open Access
The Flavor of QCD Axion Dark Matter
We argue that demanding a consistent cosmological history, including the absence of domain walls and strongly interacting relics at the Peccei-Quinn scale, singles out two concrete realizations of hadronic QCD axions as viable dark matter models. These realizations generally feature flavor-violating axion couplings to Standard Model quarks that are unsuppressed at low energies. As a consequence, experiments looking for flavor-violating hadronic processes involving the axion can be sensitive probes of QCD axion dark matter models. In particular, we show that the NA62 and KOTO experiments could detect the $K\rightarrowπ+ a$ decay for axions consistent with the observed dark matter abundance via the post-inflationary misalignment mechanism.Open AccessThe Flavor of QCD Axion Dark Matter
We argue that demanding a consistent cosmological history, including the absence of domain walls and strongly interacting relics at the Peccei-Quinn scale, singles out two concrete realizations of hadronic QCD axions as viable dark matter models. These realizations generally feature flavor-violating axion couplings to Standard Model quarks that are unsuppressed at low energies. As a consequence, experiments looking for flavor-violating hadronic processes involving the axion can be sensitive probes of QCD axion dark matter models. In particular, we show that the NA62 and KOTO experiments could detect the $K\rightarrowπ+ a$ decay for axions consistent with the observed dark matter abundance via the post-inflationary misalignment mechanism. - Open Access
Nonabelian Kinetic Mixing in a Confining Phase
Dark matter from a hidden sector with SU($N$) gauge symmetry can have a nonabelian kinetic mixing portal with the standard model. The dark photon becomes massive in the confining phase without the need for spontaneous symmetry breaking. Depending on the particle content of the dark sector, there can be two or more composite vectors that get kinetic mixing through a heavy mediator particle $X$. This provides a model of composite dark photons giving a portal for direct detection of dark baryons. Avoiding exotic charged relics requires additional couplings allowing $X$ to decay to dark quarks and standard model fields, leading to further portals between the dark matter and the standard model. We comprehensively study the constraints on such models from colliders, rare decays, direct detection, and big bang nucleosynthesis.Open AccessNonabelian Kinetic Mixing in a Confining Phase
Dark matter from a hidden sector with SU($N$) gauge symmetry can have a nonabelian kinetic mixing portal with the standard model. The dark photon becomes massive in the confining phase without the need for spontaneous symmetry breaking. Depending on the particle content of the dark sector, there can be two or more composite vectors that get kinetic mixing through a heavy mediator particle $X$. This provides a model of composite dark photons giving a portal for direct detection of dark baryons. Avoiding exotic charged relics requires additional couplings allowing $X$ to decay to dark quarks and standard model fields, leading to further portals between the dark matter and the standard model. We comprehensively study the constraints on such models from colliders, rare decays, direct detection, and big bang nucleosynthesis.