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Alexander Kusenko

Publications and source records attributed to Alexander Kusenko.

At least 163 records · Page 9Linked to original sources
arXiv2004

Pulsar kicks and dark matter from a sterile neutrino

The observed velocities of radio pulsars, which range in the hundreds kilometers per second, and many of which exceed 1000 km/s, are not explained by the standard physics of the supernova explosion. However, if a sterile neutrino with mass in the 1-20 keV range exists, it would be emitted asymmetrically from a cooling neutron star, which could give it a sufficient recoil to explain the pulsar motions. The same particle can be the cosmological dark mater. Future observations of X-ray telescopes and gravitational wave detectors can confirm or rule out this explanation.

astro-ph↗
arXiv2003

Long and short gamma-ray bursts, and the pulsar kicks

One of the mysteries that surround gamma-ray bursts (GRB) is the origin of two classes of events: long and short GRB. The short GRB are similar to the first second of a long GRB. We suggest that the short bursts are interrupted long bursts, we point out a plausible mechanism for the interruption, and we explain the observed time scales. The supernova-like central engine may contain a neutron star or a black hole surrounded by an accretion disk and jets. In the case of a neutron star, the same mechanism that is responsible for the pulsar kicks can disrupt the central engine, thus producing an interrupted, short GRB. If a black hole is produced, the absence of the kick ensures the long duration of the GRB. The time delay of the kick and the absence of the kick for a black hole are natural consequences of a model based on neutrino oscillations.

astro-ph↗
arXiv2003

Pulsar velocities and dark matter hint at a singlet neutrino

Two astrophysical puzzles, the origin of pulsar velocities and that of dark matter, may have a simultaneous explanation if there exists a sterile neutrino with a mass in the 1-20 keV range and a small mixing (of order 10^{-4}) with the electron neutrino. Although the mixing is too small for direct detection, future observations of the X-ray telescopes, as well as the gravity waves detectors, such as LIGO and LISA, may be able to confirm or rule out the existence of such a neutrino.

astro-ph↗
arXiv2003

Pulsar kicks from a dark-matter sterile neutrino

We show that a sterile neutrino with mass in the 1-20 keV range and a small mixing with the electron neutrino can simultaneously explain the origin of the pulsar motions and the dark matter in the universe. An asymmetric neutrino emission from a hot nascent neutron star can be the explanation of the observed pulsar velocities. In addition to the pulsar kick mechanism based on resonant neutrino transitions, we point out a new possibility: an asymmetric off-resonant emission of sterile neutrinos. The two cases correspond to different values of the masses and mixing angles. In both cases we identify the ranges of parameters consistent with the pulsar kick, as well as cosmological constraints.

astro-ph↗
arXiv2003

The origin of the matter-antimatter asymmetry

Although the origin of matter-antimatter asymmetry remains unknown, continuing advances in theory and improved experimental limits have ruled out some scenarios for baryogenesis, for example the sphaleron baryogenesis at the electroweak phase transition in the standard model. At the same time, the success of cosmological inflation and the prospects for discovering supersymmetry at the LHC have put some other models in sharper focus. We review the current state of our understanding of baryogenesis with the emphasis on those scenarios that we consider most plausible.

hep-ph↗
arXiv2002

Interactions of ultrahigh-energy neutrinos

Future detection of ultrahigh-energy neutrinos will open a new window on physics at center-of-mass energy 10^5 GeV and higher. In particular, observations of neutrino-initiated showers will help test the Standard Model predictions for the neutrino-nucleon cross section.

hep-ph↗
arXiv2002

CP violation and cosmology

Microscopic CP violation has profound cosmological consequences. In particular, it is related to the baryon asymmetry of the universe. A successful baryogenesis requires new sources of CP violation in addition to the Cabibbo-Kobayashi-Maskawa phase. I give a brief review of the possibilities.

hep-ph↗
arXiv2002

Experimental identification of non-pointlike dark-matter candidates

We show that direct dark matter detection experiments can distinguish between pointlike and non-pointlike dark-matter candidates. The shape of the nuclear recoil energy spectrum from pointlike dark-matter particles, e.g., neutralinos, is determined by the velocity distribution of dark matter in the galactic halo and by nuclear form factors. In contrast, typical cross sections of non-pointlike dark matter, for example, Q-balls, have a new form factor, which decreases rapidly with the recoil energy. Therefore, a signal from non-pointlike dark matter is expected to peak near the experimental threshold and to fall off rapidly at higher energies. Although the width of the signal is practically independent of the dark matter velocity dispersion, its height is expected to exhibit an annual modulation due to the changes in the dark matter flux.

hep-ph↗
arXiv2002

Future determination of the neutrino-nucleon cross section at extreme energies

Future detectors of cosmic rays, such as EUSO and OWL, can test the Standard Model predictions for the neutrino interactions at energies well beyond the reach of any terrestrial experiment. The relative rates of horizontal and upgoing air showers, combined with the angular distribution of upgoing air showers will allow one to measure the neutrino-nucleon cross section at center-of-mass energy 10^5 GeV or higher.

hep-ph↗
arXiv2002

Neutrino cross sections at high energies and the future observations of ultrahigh-energy cosmic rays

We show that future detectors of ultrahigh-energy cosmic-ray neutrinos will be able to measure neutrino-nucleon cross section at energies as high as 10^{11}GeV or higher. We find that the flux of up-going charged leptons per unit surface area produced by neutrino interactions below the surface is inversely proportional to the cross section. This contrasts with the rate of horizontal air showers (HAS) due to neutrino interactions in the atmosphere, which is proportional to the cross section. Thus, by comparing the HAS and up-going air shower (UAS) rates, the neutrino-nucleon cross section can be inferred. Taken together, up-going and horizontal rates ensure a healthy total event rate, regardless of the value of the cross section.

hep-ph↗
arXiv2001

Baryogenesis in the wake of inflation

Electroweak baryogenesis could be very efficient at the end of an electroweak-scale inflation. Reheating that followed inflation could create a highly non-equilibrium plasma, in which the baryon number violating transitions were rapid. In addition, the time-dependent motions of the scalar degrees of freedom could provide the requisite CP violation. If the final reheat temperature was below 100 GeV, there was no wash-out of the baryon asymmetry after thermalization. The observed value of the baryon asymmetry can be attained in a number of models, some of which do not require a significant departure from the Standard Model.

hep-ph↗
arXiv2001

Q-ball candidates for self-interacting dark matter

We show that non-topological solitons, known as Q-balls, are promising candidates for self-interacting dark matter. They can satisfy the cross-section requirements for a broad range of masses. Unlike previously considered examples, Q-balls can stick together after collision, reducing the effective self-interaction rate to a negligible value after a few collisions per particle. This feature modifies predictions for halo formation. We also discuss the possibility that Q-balls have large interaction cross-sections with ordinary matter.

astro-ph↗
arXiv2001

Possible galactic sources of ultrahigh-energy cosmic rays and a strategy for their detection via gravitational lensing

If decays of superheavy relic particles in the galactic halo are responsible for ultrahigh-energy cosmic rays, these particles must be clustered to account for small-scale anisotropy in the AGASA data. We show that the masses of such clusters are large enough for them to gravitationally lens stars and galaxies in the background. We propose a general strategy that can be used to detect such clusters via gravitational lensing, or to rule out the hypothesis of decaying relic particles as the origin of highest-energy cosmic rays.

astro-ph↗
arXiv2000

Neutrinos produced by ultrahigh-energy photons at high red shift

Some of the proposed explanations for the origin of ultrahigh-energy cosmic rays invoke new sources of energetic photons (e.g., topological defects, relic particles, etc.). At high red shift, when the cosmic microwave background has a higher temperature but the radio background is low, the ultrahigh-energy photons can generate neutrinos through pair-production of muons and pions. Neutrinos produced at high red shift by slowly evolving sources can be detected. Rapidly evolving sources of photons can be ruled out based on the existing upper limit on the neutrino flux.

hep-ph↗
arXiv2000

Baryonic Q-balls as dark matter

Supersymmetric extensions of the Standard Model predict the existence of Q-balls, some of which can be entirely stable. Affleck-Dine baryogenesis can result in a copious production of stable baryonic Q-balls, which can presently exist as a form of dark matter.

hep-ph↗
arXiv2000

Signature neutrinos from ultrahigh-energy photons

At high red shift, the temperature of cosmic microwave background is sufficiently high for the ultrahigh-energy photons to pair-produce muons and pions through interactions with the background photons. At the same time, the radio background and magnetic fields are too weak to drain energy out of the electromagnetic cascade before the muons and pions are produced. Decays of the energetic muons and pions yield neutrinos with some distinctive spectral properties that can be detected and can indicate the presence of ultrahigh-energy photons at high red shift. The neutrino signature can help identify the origin of cosmic rays beyond the Greisen-Zatsepin-Kuzmin cutoff.

astro-ph↗
arXiv2000

Unstable superheavy relic particles as a source of neutrinos responsible for the ultrahigh-energy cosmic rays

Decays of superheavy relic particles may produce extremely energetic neutrinos. Their annihilations on the relic neutrinos can be the origin of the cosmic rays with energies beyond the Greisen-Zatsepin-Kuzmin cutoff. The red shift acts as a cosmological filter selecting the sources at some particular value z_e, for which the present neutrino energy is close to the Z pole of the annihilation cross section. We predict no directional correlation of the ultrahigh-energy cosmic rays with the galactic halo. At the same time, there can be some directional correlations in the data, reflecting the distribution of matter at red shift z=z_e. Both of these features are manifest in the existing data. Our scenario is consistent with the neutrino mass reported by Super-Kamiokande and requires no lepton asymmetry or clustering of the background neutrinos.

hep-ph↗