R.V. Konoplich

Possible manifestations of the existence of a fourth-generation neutrino

A fourth generation of fermions predicted by the phenomenological heterotic string models can possess a new, strictly conserved charge. Among other things, this leads to the hypothesis of the existence of a fourth massive stable neutrino. A comparison of this hypothesis with the data obtained in the DAMA underground experiment to search for massive weakly-interacting cosmic particles with hidden mass and with the EGRET measurements of the >1 GeV galactic gamma-ray background gives a value m≈50 GeV for the possible mass of the fourth neutrino. It is shown that the hypothesis can be checked in accelerator experiments. The positron signal from annihilation of massive relic neutrinos in the galaxy is calculated. A search for this signal is is within the reach of planned cosmic-ray investigations.

Signature of relic heavy stable neutrinos in underground experiments

Considering heavy stable neutrinos of 4th generation we calculate the relic density of such neutrinos in the Universe. Taking into account the condensation of heavy neutrinos in the Galaxy and applying the results of calculations to experimental data from underground experiments on search for WIMPs in elastic neutral current scattering on nuclei we found an exclusion region of neutrino mass 60 GeV<m<290 GeV. The bounds obtained from present underground experiments while confirming the previous bounds derived from analysis of cosmic ray spectra are more relible ones. We discuss also the first indication of elastic scattering induced by WIMP in DAMA experiment finding a very narrow window of neutrino mass 45 GeV<m<50 GeV compatible with the possible signal rate in the detector.Considering heavy stable neutrinos of the 4th generation, we calculate the relic density of such neutrinos in the Universe. Taking into account the condensation of heavy neutrinos in the Galaxy and applying the results of calculations to experimental data from underground experiments on search for WIMPs in elastic neutral current scattering on nuclei, we find an exclusion region of neutrino mass 60 GeV<m< 290 GeV. The bounds obtained from the present underground experiments, while confirming the previous bounds derived from analysis of cosmic ray spectra, are more reliable. We also discuss the first indication of elastic scattering induced by WIMPs in the DAMA experiment, finding a very narrow window of neutrino mass 45 GeV<m<50 GeV compatible with the possible signal rate in the detector.

Evolution and observational signature of diffused antiworld

Abstract The existence of macroscopic regions with antibaryon excess in the baryon asymmetric Universe with general baryon excess is the possible consequence of practically all models of baryosynthesis. Diffusion of matter and antimatter to the border of antimatter domains defines the minimal scale of the antimatter domains surviving to the present time. A model of diffused antiworld is considered, in which the density within the surviving antimatter domains is too low to form gravitationally bound objects. The possibility to test this model by measurements of cosmic gamma ray fluxes is discussed. The expected gamma ray flux is found to be acceptable for modern cosmic gamma ray detectors and for those planned for the near future.The existence of macroscopic regions with antibaryon excess in the baryon asymmetric Universe with general baryon excess is the possible consequence of practically all models of baryosynthesis. Diffusion of matter and antimatter to the border of antimatter domains defines the minimal scale of the antimatter domains surviving to the present time. A model of diffused antiworld is considered, in which the density within the surviving antimatter domains is too low to form gravitationally bound objects. The possibility to test this model by measurements of cosmic gamma ray fluxes is discussed. The expected gamma ray flux is found to be acceptable for modern cosmic gamma ray detectors and for those planned for the near future.

Anti-helium flux as a signature for antimatter globular clusters in our galaxy

The Alpha Magnetic Spectrometer experiment is shown to be sensitive to test the hypothesis on the existence of antimatter globular cluster in our Galaxy. The hypothesis follows from the analysis of possible tests for the mechanisms of baryosynthesis and uses antimatter domains in the matter-dominated Universe as the probe for the physics underlying the origin of matter. The interval of masses for the antimatter in our Galaxy is fixed from below by the condition of antimatter domain survival in the matter-dominated Universe and from above by the observed gamma-ray flux. For this interval, the expected fluxes of anti-helium-3 and anti-helium-4 are calculated with account for their interaction with the matter in the Galaxy.

ON THE POSSIBILITY OF DETECTING THE ANNIHILATION OF VERY HEAVY NEUTRINOS IN THE GALACTIC HALO BY 1 km3 NEUTRINO DETECTOR

We consider the possibility of detecting in a hypothetical 1 km3 neutrino telescope high energy neutrinos resulting from the annihilation of very heavy neutrinos of fourth generation in the galactic halo. It is shown that such a large telescope could in principle detect this negligible component which, if it does exist, gives a contribution of order 10–2 to the dark matter of the universe.