A Monte Carlo generator of high energy cosmic ray interactions, relying on a very basic and transparent theoretical formalism, in the framework of the Reggeon field theory, is presented. The main motivation for our work is to provide a new cosmic ray interaction model characterized by relatively transparent physics, sufficient parameter freedom, and a high computational efficiency, which can be easily managed by external users, including a retuning of the model parameters. Such a model can be used for studying potential modifications of the interaction treatment, necessary for describing particular sets of data on extensive air showers initiated by high energy cosmic rays, at a microscopic level, thereby keeping a consistency with general restrictions, like the unitarity, energy-momentum and charge conservation, and Lorentz and isospin invariance. Importantly, this should allow one to study a compatibility of such modifications with relevant accelerator data. The model results for particle production and for basic extensive air shower characteristics are presented and discussed.

Germany

Sergey Ostapchenko

Tanguy Pierog

Günter Sigl

Basic model for high energy cosmic ray interactions

The treatment of charmed hadron production in the framework of the QGSJET-III Monte Carlo generator is developed, including both perturbative and nonperturbative contributions. For the former, a leading order (LO) perturbative formalism is employed. The so-called <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>K</mi></math> factor designed to take effectively into account higher-order corrections, which controls the magnitude of the LO perturbative contribution, is fixed based on a comparison with experimental data on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi></math> meson production at the Large Hadron Collider. For the nonperturbative intrinsic charm, a phenomenological Regge-based treatment is developed, with the corresponding normalization being chosen based on measurements of the spectra of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi mathvariant="normal">Λ</mi><mi>c</mi></msub></math> baryons at large values of Feynman <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>x</mi></math>. The model is applied for a calculation of the prompt atmospheric muon neutrino flux in the 10–100 TeV and 1–10 PeV energy intervals.

Charmed hadron production in the QGSJET-III model: Relevance to calculations of the prompt atmospheric neutrino background

We estimate collapse rates of axion stars in our galaxy based on the axion minicluster mass function of the Milky Way dark matter halo. We consider axionlike particles (ALP) with different temperature evolution of the axion mass, including the QCD axion with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>a</mi></msub><mo>=</mo><mn>50</mn><mtext> </mtext><mtext> </mtext><mi mathvariant="normal">μ</mi><mi>eV</mi></math>. Combining estimates for the present-day axion star mass function from our previous work with the axion star accretion model predicted by self-similar growth, we can infer the expected number of bosenovae occurring within the Milky Way. Our estimates suggest that for an observation time of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>t</mi><mi>obs</mi></msub><mo>=</mo><mn>1</mn><mtext> </mtext><mtext> </mtext><mi>yr</mi></math>, the majority of the up to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><msup><mn>10</mn><mn>13</mn></msup></math> bosenovae per galaxy occur in the densest miniclusters with initial overdensity parameter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Φ</mi><mo>≲</mo><msup><mn>10</mn><mn>4</mn></msup></math>. We discuss the detectability of such recurring axion bursts within our galactic vicinity and find that, for models with derivative couplings including axion-fermion interactions, potential broadband axion dark matter experiments can probe a large range of ALP masses <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>a</mi></msub><mo>≲</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>6</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></math> and with moderate improvements even the quantum chromodynamics axion case. For axions with nonderivative-type interactions like the axion-photon coupling, our analysis suggests that optimistic predictions with order-one dark matter abundance of axion stars <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>f</mi><mo>⋆</mo></msub><mo>∼</mo><mn>1</mn></math> can be probed by dedicated burst searches.

Dennis Maseizik

Sweden

Joshua Eby

Hyeonseok Seong

Detectability of accretion-induced bosenovae in the Milky Way

Flavor-dependent neutrino transport is described by a well-known kinetic equation for occupation-number matrices in flavor space. However, in the context of fast flavor conversion, we identify an unforeseen predicament: the pivotal self-induced exponential growth of small inhomogeneities strongly violates conservation of neutrino-neutrino refractive energy. We prove that it is traded with the huge reservoir of neutrino kinetic energy through gradients of neutrino flavor coherence (the off-diagonal piece of the flavor density matrix) and derive the missing gradient terms. The usual equations remain sufficient to describe flavor evolution, at the cost of renouncing energy conservation, which cannot play any role in explaining the numerically observed final state.

Denmark

Damiano F. G. Fiorillo

Georg G. Raffelt

Inhomogeneous Kinetic Equation for Mixed Neutrinos: Tracing the Missing Energy

The paradigm-changing possibility of collective neutrino-antineutrino oscillations was recently advanced in analogy to collective flavor oscillations. However, the amplitude for the backward scattering process <math><msub><mi>ν</mi><msub><mi>p</mi><mn>1</mn></msub></msub><msub><mover><mi>ν</mi><mo>¯</mo></mover><msub><mi>p</mi><mn>2</mn></msub></msub><mo>→</mo><msub><mi>ν</mi><msub><mi>p</mi><mn>2</mn></msub></msub><msub><mover><mi>ν</mi><mo>¯</mo></mover><msub><mi>p</mi><mn>1</mn></msub></msub></math> is helicity suppressed and vanishes for massless neutrinos, implying that there is no off-diagonal refractive index between <math><mi>ν</mi></math> and <math><mover><mi>ν</mi><mo>¯</mo></mover></math> of a single flavor of massless neutrinos. For a nonvanishing mass, collective helicity oscillations are possible, representing de facto <math><mi>ν</mi><mo>−</mo><mover><mi>ν</mi><mo>¯</mo></mover></math> oscillations in the Majorana case. However, such phenomena are suppressed by the smallness of neutrino masses as discussed in the previous literature.

Collective neutrino-antineutrino oscillations in dense neutrino environments?

The prompt contribution to the atmospheric neutrino flux is analyzed. We demonstrate that the corresponding theoretical uncertainties related to perturbative treatment of charm production, notably, the ones stemming from the low- and high-<math><mi>x</mi></math> behavior of parton distribution functions, can be conveniently studied at the level of charm quark production. Additionally, we discuss the nonperturbative contribution to the prompt neutrino flux, related to the intrinsic charm content of the proton and analyze its main features.

Maria Vittoria Garzelli

On the prompt contribution to the atmospheric neutrino flux

We investigate toy models for spatial and temporal instabilities in collective neutrino oscillations induced by neutrino self-interactions, with special emphasis on inhomogeneous systems with densities following a profile. Simulations are based on a Mathematica program that solves the Liouville equation with or without vacuum terms, refractive terms from a background medium, and neutrino-neutrino forward scattering, in one space dimension and in time. A discrete number of momentum modes are characterized by the neutrino velocity projection on the spatial direction. We also consider the effects of charged current interaction source terms and neutral current scattering contributions. We find that refractive effects from the medium, in particular for density distributions with a profile, and neutral current nonforward scattering off the background medium can strongly influence fast collective flavor transformations. Specifically we find that if both are present, fast flavor conversions can be strongly suppressed or at least delayed.

Simulations of fast neutrino flavor conversions with interactions in inhomogeneous media

Dark matter axion condensates may experience stimulated decays into photon pairs. This effect has been often interpreted as a parametric resonance of photons from the axion-photon coupling, leading to an exponential growth of the photon occupation number in a narrow instability band. Most of the previous literature does not consider the possible evolution of the axion field due to the photon growth. We revisit this effect presenting a mean field solution of the axion-photon kinetic equations, in terms of number of photons and pair correlations. We study the limit of no axion depletion, recovering the known instability. Moreover, we extend the results including a possible depletion of the axion field. In this case we find that the axion condensate exhibits the behavior of an inverted pendulum. We discuss the relevance of these effects for two different cases: a homogeneous axion field at recombination and a localized axion clump and discuss constraints that could result from the induced photon background.

Italy

Pierluca Carenza

Alessandro Mirizzi

Dynamical evolution of axion condensates under stimulated decays into photons

Fast flavor conversions of supernova neutrinos, possible near the neutrinosphere, depends on an interesting interplay of collisions and neutrino oscillations. Contrary to naïve expectations, the rate of self-induced neutrino oscillations, due to neutrino-neutrino forward scattering, comfortably exceeds the rate of collisions even deep inside the supernova core. Consistently accounting for collisions and oscillations, we present the first calculations to show that collisions can create the conditions for fast flavor conversions of neutrinos, but oscillations can continue without significant damping thereafter. This may have interesting consequences for supernova explosions and the nature of its associated neutrino emission.

Francesco Capozzi

India

Basudeb Dasgupta

Manibrata Sen

Collisional Triggering of Fast Flavor Conversions of Supernova Neutrinos

We study photon-ALP conversion by resonance effects in the magnetized plasma of galaxy clusters and compare the predicted distortion of the cosmic microwave background spectrum in the direction of such objects to measurements of the thermal Sunyaev-Zeldovich effect. Using galaxy cluster models based on current knowledge, we obtain upper limits on the photon-ALP coupling constant g of â²Â ðª(10â11 GeVâ1). The constraints apply to the mass range of 2Â Â·Â 10â14 eV â²Â mALPÂ â²Â 3Â Â·Â 10â12 eV in which resonant photon-ALP conversions can occur. These limits are slightly stronger than current limits, and furthermore provide an independent constraint. We find that a next generation PRISM-like experiment would allow limits down to gÂ âÂ ðªÂ (10â14 GeVâ1), two orders of magnitude stronger than the currently strongest limits in this mass range.