The effect of neutrinos on the initial fireballs in gamma-ray bursts

We investigate the fate of very compact, sudden energy depositions that may lie at the origin of gamma-ray bursts. Following on from the work of Cavallo and Rees (1978), we take account of the much higher energies now believed to be involved. The main effect of this is that thermal neutrinos are present and energetically important. We show that these may provide sufficient cooling to tap most of the explosion energy. However, at the extreme energies usually invoked for gamma-ray bursts, the neutrino opacity suffices to prevent dramatic losses, provided that the heating process is sufficiently fast. In a generic case, a few tens of percent of the initial fireball energy will escape as an isotropic millisecond burst of thermal neutrinos with a temperature of about 60 MeV, which is detectable for nearby gamma-ray bursts and hypernovae. For parameters we find most likely for gamma-ray burst fireballs, the dominant processes are purely leptonic, and thus the baryon loading of the fireball does not affect our conclusions.Comment: 10 pages, 4 figures. To be submitted to MNRA

Status of neutrino astronomy

Astrophysical neutrinos can be produced in proton interactions of charged cosmic rays with ambient photon or baryonic fields. Cosmic rays are observed in balloon, satellite and air shower experiments every day, from below 1e9 eV up to macroscopic energies of 1e21 eV. The observation of different photon fields has been done ever since, today with detections ranging from radio wavelengths up to very high-energy photons in the TeV range. The leading question for neutrino astronomers is now which sources provide a combination of efficient proton acceleration with sufficiently high photon fields or baryonic targets at the same time in order to produce a neutrino flux that is high enough to exceed the background of atmospheric neutrinos. There are only two confirmed astrophysical neutrino sources up to today: the sun and SuperNova 1987A emit and emitted neutrinos at MeV energies. The aim of large underground Cherenkov telescopes like IceCube and KM3NeT is the detection of neutrinos at energies above 100 GeV. In this paper, recent developments of neutrino flux modeling for the most promising extragalactic sources, gamma ray bursts and active galactic nuclei, are presented.Comment: Talk given at Neutrino 2008, Christchurch (New Zealand) 6 pages, 4 figures, 1 tabl

Status of neutrino astronomy

Astrophysical neutrinos can be produced in proton interactions of charged cosmic rays with ambient photon or baryonic fields. Cosmic rays are observed in balloon, satellite and air shower experiments every day, from below 1e9 eV up to macroscopic energies of 1e21 eV. The observation of different photon fields has been done ever since, today with detections ranging from radio wavelengths up to very high-energy photons in the TeV range. The leading question for neutrino astronomers is now which sources provide a combination of efficient proton acceleration with sufficiently high photon fields or baryonic targets at the same time in order to produce a neutrino flux that is high enough to exceed the background of atmospheric neutrinos. There are only two confirmed astrophysical neutrino sources up to today: the sun and SuperNova 1987A emit and emitted neutrinos at MeV energies. The aim of large underground Cherenkov telescopes like IceCube and KM3NeT is the detection of neutrinos at energies above 100 GeV. In this paper, recent developments of neutrino flux modeling for the most promising extragalactic sources, gamma ray bursts and active galactic nuclei, are presented.Comment: Talk given at Neutrino 2008, Christchurch (New Zealand) 6 pages, 4 figures, 1 tabl

Status of neutrino astronomy

Astrophysical neutrinos can be produced in proton interactions of charged cosmic rays with ambient photon or baryonic fields. Cosmic rays are observed in balloon, satellite and air shower experiments every day, from below 1e9 eV up to macroscopic energies of 1e21 eV. The observation of different photon fields has been done ever since, today with detections ranging from radio wavelengths up to very high-energy photons in the TeV range. The leading question for neutrino astronomers is now which sources provide a combination of efficient proton acceleration with sufficiently high photon fields or baryonic targets at the same time in order to produce a neutrino flux that is high enough to exceed the background of atmospheric neutrinos. There are only two confirmed astrophysical neutrino sources up to today: the sun and SuperNova 1987A emit and emitted neutrinos at MeV energies. The aim of large underground Cherenkov telescopes like IceCube and KM3NeT is the detection of neutrinos at energies above 100 GeV. In this paper, recent developments of neutrino flux modeling for the most promising extragalactic sources, gamma ray bursts and active galactic nuclei, are presented.Comment: Talk given at Neutrino 2008, Christchurch (New Zealand) 6 pages, 4 figures, 1 tabl

A Three-Point Cosmic Ray Anisotropy Method

The two-point angular correlation function is a traditional method used to search for deviations from expectations of isotropy. In this paper we develop and explore a statistically descriptive three-point method with the intended application being the search for deviations from isotropy in the highest energy cosmic rays. We compare the sensitivity of a two-point method and a "shape-strength" method for a variety of Monte-Carlo simulated anisotropic signals. Studies are done with anisotropic source signals diluted by an isotropic background. Type I and II errors for rejecting the hypothesis of isotropic cosmic ray arrival directions are evaluated for four different event sample sizes: 27, 40, 60 and 80 events, consistent with near term data expectations from the Pierre Auger Observatory. In all cases the ability to reject the isotropic hypothesis improves with event size and with the fraction of anisotropic signal. While ~40 event data sets should be sufficient for reliable identification of anisotropy in cases of rather extreme (highly anisotropic) data, much larger data sets are suggested for reliable identification of more subtle anisotropies. The shape-strength method consistently performs better than the two point method and can be easily adapted to an arbitrary experimental exposure on the celestial sphere.Comment: Fixed PDF erro

Quantum treatment of neutrino in background matter

Motivated by the need of elaboration of the quantum theory of the spin light of neutrino in matter ($SL\nu$), we have studied in more detail the exact solutions of the Dirac equation for neutrinos moving in the background matter. These exact neutrino wavefunctions form a basis for a rather powerful method of investigation of different neutrino processes in matter, which is similar to the Furry representation of quantum electrodynamics in external fields. Within this method we also derive the corresponding Dirac equation for an electron moving in matter and consider the electromagnetic radiation ("spin light of electron in matter", $SLe$) that can be emitted by the electron in this case.Comment: 10 pages, in: Proceedings of QFEXT'05 (The Seventh Workshop on Quantum Field Theory under the Influence of External Conditions, IEEC, CSIC and University of Barcelona, Barcelona, Catalonia, Spain, 5-9 September 2005.), ed. by Emilio Elizalde and Sergei Odintsov; published in Journal of Physics

A Search for Correlation of Ultra-High Energy Cosmic Rays with IRAS-PSCz and 2MASS-6dF Galaxies

We study the arrival directions of 69 ultra-high energy cosmic rays (UHECRs) observed at the Pierre Auger Observatory (PAO) with energies exceeding 55 EeV. We investigate whether the UHECRs exhibit the anisotropy signal expected if the primary particles are protons that originate in galaxies in the local universe, or in sources correlated with these galaxies. We cross-correlate the UHECR arrival directions with the positions of IRAS-PSCz and 2MASS-6dF galaxies taking into account particle energy losses during propagation. This is the first time that the 6dF survey is used in a search for the sources of UHECRs and the first time that the PSCz survey is used with the full 69 PAO events. The observed cross-correlation signal is larger for the PAO UHECRs than for 94% (98%) of realisations from an isotropic distribution when cross-correlated with the PSCz (6dF). On the other hand the observed cross-correlation signal is lower than that expected from 85% of realisations, had the UHECRs originated in galaxies in either survey. The observed cross-correlation signal does exceed that expected by 50% of the realisations if the UHECRs are randomly deflected by intervening magnetic fields by 5 degrees or more. We propose a new method of analysing the expected anisotropy signal, by dividing the predicted UHECR source distribution into equal predicted flux radial shells, which can help localise and constrain the properties of UHECR sources. We find that the 69 PAO events are consistent with isotropy in the nearest of three shells we define, whereas there is weak evidence for correlation with the predicted source distribution in the two more distant shells in which the galaxy distribution is less anisotropic.Comment: 23 pages, version published in JCA

Search for Anisotropy of Ultra-High Energy Cosmic Rays with the Telescope Array Experiment

We study the anisotropy of Ultra-High Energy Cosmic Ray (UHECR) events collected by the Telescope Array (TA) detector in the first 40 months of operation. Following earlier studies, we examine event sets with energy thresholds of 10 EeV, 40 EeV, and 57 EeV. We find that the distributions of the events in right ascension and declination are compatible with an isotropic distribution in all three sets. We then compare with previously reported clustering of the UHECR events at small angular scales. No significant clustering is found in the TA data. We then check the events with E>57 EeV for correlations with nearby active galactic nuclei. No significant correlation is found. Finally, we examine all three sets for correlations with the large-scale structure of the Universe. We find that the two higher-energy sets are compatible with both an isotropic distribution and the hypothesis that UHECR sources follow the matter distribution of the Universe (the LSS hypothesis), while the event set with E>10 EeV is compatible with isotropy and is not compatible with the LSS hypothesis at 95% CL unless large deflection angles are also assumed. We show that accounting for UHECR deflections in a realistic model of the Galactic magnetic field can make this set compatible with the LSS hypothesis.Comment: 10 pages, 9 figure

CORRELATIONS OF THE ARRIVAL DIRECTIONS OF ULTRA-HIGH ENERGY COSMIC RAYS WITH EXTRAGALACTIC OBJECTS AS OBSERVED BY THE TELESCOPE ARRAY EXPERIMENT

We search for correlations between the positions of extragalactic objects and the arrival directions of ultra-high energy cosmic rays (UHECRs) with primary energy E ??? 40 EeV as observed by the surface detector array of the Telescope Array (TA) experiment during the first 40 months of operation. We examine several public astronomical object catalogs, including the Veron-Cetty and Veron catalog of active galactic nuclei. We count the number of TA events correlated with objects in each catalog as a function of three parameters: the maximum angular separation between a TA event and an object, the minimum energy of the events, and the maximum redshift of the objects. We determine the combination of these parameters that maximizes the correlations, and we calculate the probability of having the same levels of correlations from an isotropic distribution of UHECR arrival directions. No statistically significant correlations are found when penalties for scanning over the above parameters and for searching in several catalogs are taken into account.open4