GZK Cutoff Research Articles

Propagation and fluxes of ultra-high energy cosmic rays in f(R)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varvec{f(R)}$$\\end{document} gravity theory

In this work, we study the effect of diffusion of ultra-high energy cosmic ray (UHECR) protons in the presence of turbulent magnetic fields (TMFs) in the light of the f(R) theory of gravity. The f(R) theory of gravity is a successful modified theory of gravity in explaining the various aspects of the observable Universe including its current state of expansion. For this work, we consider two most studied f(R) gravity models, viz., the power-law model and the Starobinsky model. With these two models, we study the diffusive character of the propagation of UHECR protons in terms of their density enhancement. The density enhancement is a measure of how the density of CRs changes due to their diffusion in the intergalactic medium and interaction with the cosmic microwave background (CMB) radiation. Ankle, instep and Greisen–Zatsepin–Kuzmin (GZK) cutoff are all spectrum characteristics that extragalactic UHECRs acquire when they propagate through the CMB. We analyse all these characteristics through the diffusive flux as well as its modification factor. Model dependence of the modification factor is minimal compared to the diffusive flux. We compare the UHECR proton spectra calculated for the considered f(R) gravity models with the available data of the Telescope Array (TA) and Pierre Auger Observatory (PAO). We see that both models of f(R) gravity predict energy spectra of UHECRs with all experimentally observed features, which lay well within the range of combined data of both experiments throughout the energy range of concern. It is to be noted that our present work is only to investigate the possible effects of f(R) gravity theory on the UHECRs propagation, using pure proton composition as a simplified case study since protons are least affected by magnetic fields. Hence, at this stage, our results cannot be used to favor or disfavor f(R) cosmology over Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda $$\\end{document}CDM cosmology as more work is needed in this regard.

Abnormal threshold behaviors of photo-pion production off the proton in the GZK region

The cosmic-ray spectrum structures help to study the acceleration and propagation mechanism of ultra-high energy cosmic rays, and these structures were predicted to culminate in a cut-off, named the Greisen–Zatsepin–Kuzmin (GZK) cut-off, near 5×1019eV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$5\ imes 10^{19}~\ extrm{eV}$$\\end{document} as a result of the inelastic interaction of protons with the 2.73K\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2.73~\ extrm{K}$$\\end{document} black body radiation. The confirmation of the existence of GZK cut-off was tortuous, leading to activities to explore new physics, such as the cosmic-ray new components, unidentified cosmic-ray origins, unknown propagation mechanism and the modification of fundamental physics concepts like the tiny Lorentz invariance violation (LV). The confirmation of the GZK cut-off provides an opportunity to constrain the LV effect. We use a phenomenological framework to restudy the GZK mechanism under the Planck scale deformation of the proton and pion dispersion relations. Restudying the photon induced pion production of the proton p+γ→p+π0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{p}+\\gamma \\rightarrow \ extrm{p}+\\pi ^0$$\\end{document}, we predict abnormal threshold behaviors of this reaction under different LV modifications. Therefore we can study the LV effects not only from the conventional GZK cut-off, but also from potentially threshold anomalies of the pion production process. We divide the LV parameter space into three regions, and analyze the constraints from current observations in each region. The current observations have set strict restrictions on a certain LV region. However, for others LV regions, further experimental observations and theoretical researches are still needed, and we also find survival space for some theoretical explorations that permit specific LV effects.

Constraints on the proton fraction of cosmic rays at the highest energies and the consequences for cosmogenic neutrinos and photons

Over the last decade, observations have shown that the mean mass of ultra-high-energy cosmic rays (UHECRs) increases progressively toward the highest energies. However, the precise composition is still unknown and several theoretical studies hint at the existence of a subdominant proton component up to the highest energies. Motivated by the exciting prospect of performing charged-particle astronomy with ultra-high-energy (UHE) protons we quantify the level of UHE-proton flux that is compatible with present multimessenger observations and the associated fluxes of neutral messengers produced in the interactions of the protons. We study this scenario with numerical simulations of two independent populations of extragalactic sources and perform a fit to the combined UHECR energy spectrum and composition observables, constrained by diffuse gamma-ray and neutrino observations. We find that up to of order 10% of the cosmic rays at the highest energies can be UHE protons, although the result depends critically on the selected hadronic interaction model for the air showers. Depending on the maximum proton energy (E max p) and the redshift evolution of sources, the associated flux of cosmogenic neutrinos and UHE gamma rays can significantly exceed the multimessenger signal of the mixed-mass cosmic rays. Moreover, if E max p is above the GZK limit, we predict a large flux of UHE neutrinos above EeV energies that is absent in alternate scenarios for the origin of UHECRs. We present the implications and opportunities afforded by these UHE proton, neutrino and photon fluxes for future multimessenger observations.

A relook at the GZK neutrino-photon connection: impact of extra-galactic radio background & UHECR properties

Ultra-high energy cosmic rays (UHECRs) beyond the Greisen-Zatsepin-Kuzmin (GZK) cut-off provide us with a unique opportunity to understand the universe at extreme energies. Secondary GZK photons and GZK neutrinos associated with the same interaction are indeed interconnected and render access to multi-messenger analysis of UHECRs. The GZK photon flux is heavily attenuated due to the interaction with Cosmic Microwave Background (CMB) and the Extra-galactic Radio Background (ERB). The present estimate of the ERB comprising of several model uncertainties together with the ARCADE2 radio results in large propagation uncertainties in the GZK photon flux. On the other hand, the weakly interacting GZK neutrino flux is unaffected by these propagation effects. In this work, we make an updated estimate of the GZK photon and GZK neutrino fluxes considering a wide variation of both the production and propagation properties of the UHECR like, the spectral index, the cut-off energy of the primary spectrum, the distribution of sources and the uncertainties in the ERB estimation. We explore the detection prospects of the GZK fluxes with various present and upcoming UHECR and UHE neutrino detectors such as Auger, TA, GRAND, ANITA, ARA, IceCube and IceCube-Gen2. The predicted fluxes are found to be beyond the reach of the current detectors. In future, proposed IceCube-Gen2, Auger upgrade and GRAND experiments will have the sensitivity to the predicted GZK photon and GZK neutrino fluxes. Such detection can put constraints on the UHECR source properties and the propagation effects due to the ERB. We also propose an indirect limit on the GZK photon flux using the neutrino-photon connection for any future detection of GZK neutrinos by the IceCube-Gen2 detector. We find this limit to be consistent with our GZK flux predictions.

GZK Cutoff in Presence of a Specified Modified Dispersion Relation

GZK Cutoff in Presence of a Specified Modified Dispersion Relation

Signatures of wakefield acceleration in astrophysical jets via gamma-rays and UHECRs

ABSTRACT We present six case studies from a comprehensive mass range (1–109 M⊙) of astrophysical objects, each of which possess jets, emit high-energy gamma radiation and in some instances spatially identifiable ultra-high-energy cosmic rays (UHECRs). All sources are strong candidates for UHECR emission, if not already known to emit them. We surmise that wakefield acceleration in conjunction with the magnetorotational instability of the accretion disc explains both structural properties of the jets and details in their emission signals, such as correlations in neutrino and gamma-ray bursts, and in the case of blazars, anticorrelations in flux and spectral index. Furthermore, our model predicts an upper bound for the energy of UHECRs emitted from a source given the mass of its central compact object and total jet luminosity. To provide context for our model predictions, we quantitatively compare them with observational data, however, we have not accounted for the GZK limit and assumed universal values for several model parameters (e.g. jet-spreading index, p) that likely differ between sources. Since the accretion and acceleration mechanisms are independent of mass, aside from determining maximum values, blazars (∼109 M⊙), radio galaxies ($\sim 10^8\, {\rm M}_{\odot }$ ), Seyfert galaxies ($\sim 10^6 \, {\rm M}_{\odot }$ ), starburst galaxies ($\sim 10^{3}\, {\rm M}_{\odot }$ ), even microquasars (1–10 M⊙) interestingly exhibit the same physics. Other radiation bands, such as X-ray, ultraviolet, or radio, may harbour additional information, but we chose not to focus on them for brevity. However, such an endeavour may open the door to a new multimessenger approach for understanding these objects.

The dark dimension and the Swampland

Motivated by principles from the Swampland program, which characterize requirements for a consistent UV completion of quantum gravity, combined with observational data, we are led to a unique corner of the quantum gravity landscape. In particular, using the Distance/Duality conjecture and the smallness of dark energy, we predict the existence of a light tower of states and a unique extra mesoscopic dimension of length lsim {Lambda}^{-frac{1}{4}}sim {10}^{-6}m , with extra massless fermions propagating on it. This automatically leads to a candidate for a tower of sterile neutrinos, and an associated active neutrino mass scale {m}_{nu}sim {leftlangle Hrightrangle}^2{Lambda}^{-frac{1}{12}}{M}_{textrm{pl}}^{-frac{2}{3}} . Moreover, assuming the mechanism for stabilization of this dark dimension leads to similar masses for active and sterile neutrinos we are led to the prediction of a Higgs vev leftlangle Hrightrangle sim {Lambda}^{frac{1}{6}}{M}_{textrm{pl}}^{frac{1}{3}} . Another prediction of the scenario is a species scale hat{M}sim {Lambda}^{frac{1}{12}}{M}_{textrm{pl}}^{frac{2}{3}}sim {10}^9hbox{--} {10}^{10} GeV, corresponding to the higher-dimensional Planck scale. This energy scale may be related to the resolution of the instability of the Higgs effective potential present at a scale of ~1011 GeV. We also speculate about the interplay between this energy scale and the GZK limit on ultra-high energy cosmic rays.

Revealing ultra-high-energy cosmic ray acceleration with multi-messenger observations of the nearby GRB 980425/SN 1998bw

The origin of ultra-high energy cosmic rays (UHECRs) is one of the most mystifying issues in astroparticle physics. It has been suggested that gamma-ray bursts (GRBs) are excellent acceleration sites for cosmic rays. The propagation of UHECRs from the GRB host galaxy to the Earth should generate delayed secondary photons and neutrinos. Here we present a dedicated search for delayed UHECR and neutrino emission centered around the position of nearby GRB 980425/SN 1998bw. Located at a distance of 36.9 Mpc, GRB 980425/SN 1998bw is well within the Greisen-Zatsepin-Kuzmin (GZK) distance horizon. We find no evidence for UHECR or neutrino clustering around the GRB 980425/SN 1998bw position between 2004 and 2020. Under ideal propagation conditions, we propose that it might be possible to detect an excess from delayed UHECRs around GRB 980425/SN 1998bw within the next 100 years if the intergalactic magnetic field (IGMF) strength is B ≤ 3 × 10-13 G.

Energy Spectrum Measured by the Telescope Array Surface Detectors

Located in the west desert of Utah, USA, the Telescope Array experiment is the largest ultra-high energy cosmic ray observatory in the northern hemisphere. It consists of two types of detectors: scintillator surface detectors (SDs) and air fluorescence detectors (FDs). A total of 507 SDs consisting of two-layer plastic scintillation counters is deployed with 1.2 km spacing, making measurements over an area of approximately 700 km2. There are 3 FD stations, having 38 fluorescence telescopes viewing 3°–31°in elevation, overlooking the SD array. In this work, we update the Telescope Array energy spectrum as measured by the SD array for 14 years. We verify the linearity in TA SD energy reconstruction using three different energy comparisons: Monte Carlo comparison, FD/SD comparison, and Constant Intensity Cut method. The spectral features of ankle, softening, and GZK cutoff are seen in 14 years of TA SD data. Also, we consistently observe that the cutoff energy depends on declination.

“The more things change the more they stay the same” Minimum lengths with unmodified uncertainty principle and dispersion relation

Broad arguments indicate that quantum gravity should have a minimal length scale. In this paper, we construct a minimum length model by generalizing the time-position and energy–momentum operators while keeping much of the structure of quantum mechanics and relativity intact: the standard position-momentum commutator, the special relativistic time-position, and energy–momentum relationships all remain the same. Since the time-position and energy–momentum relationships for the modified operators remain the same, we retain a form of Lorentz symmetry. This avoids the constraints on these theories coming from lack of photon dispersion while holding the potential to address the Greisen–Zatsepin–Kuzmin (GZK) puzzle of ultra high-energy cosmic rays.

A new probe of relic neutrino clustering using cosmogenic neutrinos

We propose a new probe of cosmic relic neutrinos (CνB) using their resonant scattering against cosmogenic neutrinos. Depending on the lightest neutrino mass and the energy spectrum of the cosmogenic neutrino flux, a Standard Model vector meson (such as a hadronic ρ) resonance can be produced via νν¯ annihilation. This leads to a distinct absorption feature in the cosmogenic neutrino flux at an energy solely determined by the meson mass and the neutrino mass, apart from redshift. By numerical coincidence, the position of the ρ-resonance overlaps with the originally predicted peak of the Greisen-Zatsepin-Kuzmin (GZK) neutrino flux, which offers an enhanced effect at higher redshifts. We show that this absorption feature in the GZK neutrino flux may be observable in future radio-based neutrino observatories, such as IceCube-Gen2 radio, provided there exists a large overdensity in the CνB distribution. This therefore provides a new probe of CνB clustering at large redshifts, complementary to the laboratory probes (such as KATRIN) at zero redshift.

Ultra-High-Energy Particles at the Border of Kerr Black Holes Triggered by Magnetocentrifugal Winds

The source, origin, and acceleration mechanisms of ultra-high-energy cosmic rays (UHECR) (E>1020 eV, beyond the GZK limit) remain uncertain and unclear. The main explanations are associated with particular mechanisms, such as the Fermi mechanism, in which charged particles could be accelerated by clouds of magnetized gas moving within our Galaxy, or by the magnetic reconnection of field lines at, e.g., the core of high-energy astrophysical sources, where the topology of the magnetic field is rearranged and magnetic energy is converted into kinetic energy. However, the recent observation of extragalactic neutrinos may suggest that the source of UHECRs is likely an extragalactic supermassive black hole. In the present work, we propose that charged particles can be accelerated to ultrahigh energies in marginally bound orbits near extreme rotating black holes and could be triggered by collisions of magnetocentrifugal winds; the accretion disk surrounding the black hole would provide such winds. The ultra-high-energy process is governed by the frame-dragging effects of the black hole spacetime.

“Super GZK” Particles in a Classic Kramers’ Diffusion-over-a-barrier Model. I. The Case of Protons

Abstract In interactions of ultra-high-energy cosmic ray (UHECR) protons with cosmic microwave background photons, we focus in this work on photopion production reactions and the effects of the measured, broad, energy-loss distributions in these reactions on the evolution of the protons’ density functions in energy space. We rely on a Fokker–Planck transport equation in energy space whose transport coefficients are calculated using laboratory measurements. We also derive a Fokker–Planck potential that accounts for both systematic (drift) and stochastic (dispersive) energy losses due to photopion production reactions. Our results show that dispersive energy losses have significant effects on estimating the protons’ horizon distance and their energy spectrum, as well as to elucidate a broadness in the GZK cutoff. We use the derived Fokker–Planck potential to assign a characteristic probability for a proton to clear the potential barrier as a function of energy. This estimate of probability can be used to assist observations in distinguishing between protons and heavy ions as charged particles. Our model is able to account for the so-called super GZK particles as a classic diffusion-over-a-barrier manifestation of the transport of UHECR protons in energy space in quantifying the extent and broadness of the GZK cutoff.

Cosmic Rays and Ultra High Energy Cosmic Rays (UHECR), GZK (Greisen-Zatsepin-Kuzmin) cutoff, Deflection angle of high energy cosmic rays in the propagation through the galactic and extragalactic magnetic fields, Auger Surface Detector and the Monitoring Data, Measurement of the Lifetime of Muons and Pions and The Variant Mass for a Particle in a Gravitational Field and the Binary Stars: The

The Surface Detector of the Pierre Auger Observatory consists of 1600 water Cherenkov tanks sampling ground particles of air showers produced by energetic cosmic rays. Every water tank is equipped with three photomultipliers (PMTs). Every 7 minutes monitoring data are recorded from each surface detector to ensure that they are performing as intended and also to understand the detector behavior. The monitoring data set is used to study the evolution of parameters of the PMTs as a function of both time and temperature. The main objective of the monitoring data is to monitor the stability of the PMTs. In case there is abnormal behavior detected, an alarm entry is created in the database. The classification of the alarms into different categories, corresponding to the observed patterns of the PMT variables and the decision of the alarm level are subject of this work. It is also researched the photomultipliers parameters and the alarm creation with examples of it: the Free Disk and High PMT gain change Alarms using c++, root and mysql. For other hand, it is researched about the measurement of the lifetime of muons and pions theoretically, experimentally and with the application of Statistics for the uncertainties of the results. The results have high accuracy and in accordance with the values of the literature. In addition, it is to analyze theoretically the deflection angle of the high energy cosmic rays in the propagation through the galactic and extragalactic magnetic fields. It is used the magnetic force formula and the Larmor radius, trigonometry, and the tables for the values of the galactic and extragalactic magnetic field and the distances to the galactic and extragalactic sources. It is possible to observe from this analysis that the deflection angles are very small for the considered cases. Thus, UHECR arrival directions should point back to their sources in the sky. Besides, it is researched about the GZK (Greisen-Zatsepin-Kuzmin) cutoff. A sharp cutoff at approximately several times 1019 eV in the energy spectrum of the cosmic rays is expected due to the energy degradation of the cosmic rays through their interaction with photons of the microwave background radiation. It is known as the GZK (Greisen-Zatsepin-Kuzmin) cutoff. A nucleon with an initial energy above Eo=1020 eV lose about 1/5 of Eo (initial energy) in each interaction. Thus, a nucleon of initial energy above 1020 eV will reduce its energy to 6*1019 eV (GZK cutoff energy) after traveling a distance of approximately 50 Mpc. For other hand, Albert Einstein wrote in a research article: “Does the inertia of a body depend on its energy content?” (Ist die Tragheit eines Korpers von seimen Energienhalt abhangig?): “If a body emits energy E in the form of radiation, its mass decreases by E/c2”. Thus, Maxwell's theory shows that electromagnetic waves are radiated whenever charges accelerate as for example for the electron. Then, this electromagnetic radiation (photons) produces a decrease in the mass of the electron which is given by the formula of the Variant Mass for an Accelerated Charged Particle which was demonstrated by me at this research [34] and at the research of the Variant Mass of the Electron at the Atom. This is true for any type of radiation emitted: electromagnetic or gravitational energy which produce a decrease in the mass of the body. Therefore, other objective of this article is to demonstrate the discovered formula which describes exactly the variant mass for a particle which emits gravitational energy. An example of the effect of this Gravitational energy emission is the light deflection for the light passing close the Sun (gravitational redshift frequency) and the Perihelion Precession of Mercury. Thus, the results of the mass formula are of great relevance for Gravitational Interactions. The results are in accordance with the classic result for the emission of the total gravitational energy (bond total energy) for a particle orbiting a large Planet or Sun and for a Binary Star. It is in agreement with the experiment result and with the Theory of General Relativity.

Modeling the spectrum and composition of ultrahigh-energy cosmic rays with two populations of extragalactic sources

We fit the ultrahigh-energy cosmic-ray (UHECR, Egtrsim 0.1 EeV) spectrum and composition data from the Pierre Auger Observatory at energies Egtrsim 5cdot 10^{18} eV, i.e., beyond the ankle using two populations of astrophysical sources. One population, accelerating dominantly protons (^1H), extends up to the highest observed energies with maximum energy close to the GZK cutoff and injection spectral index near the Fermi acceleration model; while another population accelerates light-to-heavy nuclei (^4He, ^{14}N, ^{28}Si, ^{56}Fe) with a relatively low rigidity cutoff and hard injection spectrum. A significant improvement in the combined fit is noted as we go from a one-population to two-population model. For the latter, we constrain the maximum allowed proton fraction at the highest-energy bin within 3.5sigma statistical significance. In the single-population model, low-luminosity gamma-ray bursts turn out to match the best-fit evolution parameter. In the two-population model, the active galactic nuclei is consistent with the best-fit redshift evolution parameter of the pure proton-emitting sources, while the tidal disruption events could be responsible for emitting heavier nuclei. We also compute expected cosmogenic neutrino flux in such a hybrid source population scenario and discuss possibilities to detect these neutrinos by upcoming detectors to shed light on the sources of UHECRs.

Particle dynamics and GZK limit in relativity with a preferred frame

The theory termed ‘special relativity (SR) with a preferred frame’ incorporates the preferred frame into special relativity while retaining the fundamental space-time symmetry which, in the standard SR, manifests itself as Lorentz invariance. In this paper, the theory is extended to particle dynamics based on the concept of the ‘modified spacetime symmetry’ which allows to develop the theory along the lines of the standard relativity theory. The modified relativistic dynamics is applied to describing the interactions of the Ultra High Energy Cosmic Rays (UHECR) with universal diffuse background radiation and, in particular, to calculating the Greisen–Zatsepin–Kuzmin (GZK) threshold for the energy suppression due to pion photoproduction by UHECR protons. The result, that the GZK cutoff energy depends on the distance (cosmological redshift z) to the source of particles, may contribute to interpretation of the data on the mass composition of UHECR.

Supermassive Black Holes as Possible Sources of Ultrahigh-energy Cosmic Rays

Abstract The production and acceleration mechanisms of ultrahigh-energy cosmic rays (UHECRs) of energy >1020 eV, clearly beyond the GZK cutoff limit, remain unclear, which points to the exotic nature of the phenomena. Recent observations of extragalactic neutrinos may indicate that the source of UHECRs is an extragalactic supermassive black hole (SMBH). We demonstrate that ultraefficient energy extraction from a rotating SMBH driven by the magnetic Penrose process (MPP) could indeed fit the bill. We envision ionization of neutral particles, such as neutron beta decay, skirting close to the black hole horizon that energizes protons to over 1020 eV for an SMBH of mass 109 M ⊙ and magnetic field 104 G. Applied to the Galactic center SMBH, we have a proton energy of order ≈1015.6 eV that coincides with the knee of the cosmic-ray spectra. We show that large γ z factors of high-energy particles along the escaping directions occur only in the presence of an induced charge of the black hole, which is known as the Wald charge in the case of a uniform magnetic field. It is remarkable that the process requires neither an extended acceleration zone nor fine-tuning of accreting-matter parameters. Further, this leads to certain verifiable constraints on the SMBH’s mass and magnetic field strength as the source of UHECRs. This clearly makes the ultraefficient regime of the MPP one of the most promising mechanisms for fueling the UHECR powerhouse.

Bounds on extra dimensions from micro black holes in the context of the metastable Higgs vacuum

We estimate the rate at which collisions between ultra-high energy cosmic rays can form small black holes in models with extra dimensions. If recent conjectures about false vacuum decay catalyzed by black hole evaporation apply, the lack of vacuum decay events in our past light cone may place new bounds on the black hole formation rate and thus on the fundamental scale of gravity in these models. For theories with fundamental scale $E_{*}$ above the Higgs instability scale of the Standard Model, we find a lower bound on $E_{*}$ that is within about an order of magnitude of the energy where the cosmic ray spectrum begins to show suppression from the GZK effect. Otherwise, the abundant formation of semiclassical black holes with short lifetimes would likely initiate vacuum decay. Assuming a Higgs instability scale at the low end of the range compatible with experimental data, the excluded range is approximately $10^{17} \,\text{eV} \lesssim E_{*} \leq 10^{18.8}\,\text{eV}$ for theories with $n=1$ extra dimension, narrowing to $10^{17}\,\text{eV} \lesssim E_{*} \leq 10^{18.1}\,\text{eV}$ for $n=6$. These bounds rule out regions of parameter space that are inaccessible to collider experiments, small-scale gravity tests, or estimates of Kaluza-Klein processes in neutron stars and supernovae.

Dark matter, neutrino mass, cutoff for cosmic-ray neutrino, and the Higgs boson invisible decay from a neutrino portal interaction

We study an effective theory beyond the standard model (SM) where either of the two additional gauge singlets, a Majorana fermion and a real scalar, constitutes all or some fraction of dark matter. In particular, we focus on the masses of the two singlets in the range of (10) MeV- (10) GeV with a neutrino portal interaction, which plays an important role not only in particle physics but also in cosmology and astronomy. We point out that the thermal dark matter abundance can be explained by (co-)annihilation, where the dark matter with a mass greater than 2 GeV can be tested in future lepton colliders, CEPC, ILC, FCC-ee and CLIC, in the light of the Higgs boson invisible decay. When the gauge singlets are lighter than (100) MeV, the interaction can affect the neutrino propagation in the universe due to its annihilation with cosmic background neutrino into the gauge singlets. Although in this case it can not be the dominant dark matter, the singlets are produced by the invisible decay of the Higgs boson at such a rate which is fully within reach of future lepton colliders. In particular, a high energy cutoff of cosmic-ray neutrino, which may account for the non-detection of Greisen-Zatsepin-Kuzmin (GZK) neutrino or the non-observation of the Glashow resonance, can be set. Interestingly, given the cutoff and the mass (range) of WIMPs, a neutrino mass can be " measured” kinematically.

Ultra high energy cosmic rays simulated with CONEX code

Today, many experiments around the world (Auger Observatory, Telescope Array, and soon Jem-Euso experiment...) are tracking ultra-high energy cosmic rays. They try to collect some exceptional data that would lift the veil on this type of cosmic rays , mainly to answer why does their energies exceed the GZK cutoff without pointing to astrophysical sources close to our galaxy. Furthermore, we do not really know neither the identity nor the acceleration processes that can provide them with such colossal energy. We have performed, using the CONEX program version 2r6.40 coupled to different hadronic interaction models (QGSJET01, EPOS LHC , SIBYLL 2.1 and QGSJETII-04) simulations focused on the slant depth Xmax of the maximum of the shower longitudinal profile and the charged particle number Nmax. Theses parameters and their fluctuations are very sensitive to the primary particle mass (identity) and energy. The obtained results are compared for proton and iron primaries at the energy range 1018-1021 eV.