arXiv subjects

Teresa Montaruli

Publications and source records attributed to Teresa Montaruli.

At least 37 records · Page 2Linked to original sources

arXiv2010

IceCube and Searches for Astrophysical Sources

Understanding cosmic acceleration mechanisms, such as jet formation in black holes, star collapses or binary mergers, and the propagation of accelerated particles in the universe is still a `work in progress' and requires a multi-messenger approach, exploiting the complementarities across all possible probes: ultra-high energy cosmic rays (UHECR), gamma-rays and neutrinos. In this report I will summarize some of the IceCube results concerning searches for astrophysical neutrino point sources and diffuse fluxes from populations of sources widely distributed in the sky or from the interactions of protons on the cosmic microwave background producing the GZK cut-off in the cosmic ray spectrum. I will compare the results to other neutrino telescopes and to astrophysical models of neutrino production in sources. Another unresolved question concerns the nature of dark matter. Indirect searches have the opportunity to observe where it is located in the universe through the observation of secondary photons, neutrinos or antiparticles such as positrons and antiprotons. The potential for the search of neutrinos from the annihilation of WIMPs in IceCube is greatly enhanced by the addition of more compact strings, the DeepCore.

astro-ph.HE↗

arXiv2010

Spectra of neutrinos from dark matter annihilations

We study the fluxes of neutrinos from annihilations of dark matter particles in the Sun and the Earth. We give the spectra of all neutrino flavors for the main known annihilation channels: nu-antinu, b-bbar, tau-taubar, c-cbar, light quarks, ZZ, W^+W^-. We present the appropriate formalism for computing the combined effect of oscillations, absorptions, nu_tau-regeneration. Total rates are modified by an O(0.1--10) factor, comparable to astrophysical uncertainties, that instead negligibly affect the spectra. We then calculate different signal topologies in neutrino telescopes: through-going muons, contained muons, showers, and study their capabilities to discriminate a dark matter signal from backgrounds. We finally discuss how measuring the neutrino spectra can allow to reconstruct the fundamental properties of the dark matter: its mass and its annihilation branching ratios.

hep-ph↗

arXiv2009

Time-Dependent Point Source Search Methods in High Energy Neutrino Astronomy

We present maximum-likelihood search methods for time-dependent fluxes from point sources, such as flares or periodic emissions. We describe a method for the case when the time dependence of the flux can be assumed a priori from other observations, and we additionally describe a method to search for bursts with an unknown time dependence. In the context of high energy neutrino astronomy, we simulate one year of data from a cubic-kilometer scale neutrino detector and characterize these methods and equivalent binned methods with respect to the duration of neutrino emission. Compared to standard time-integrated searches, we find that up to an order of magnitude fewer events are needed to discover bursts with short durations, even when the burst time and duration are not known a priori.

astro-ph.IM↗

arXiv2009

In Search for Extraterrestrial High Energy Neutrinos

In this paper we review the search for astrophysical neutrinos. We begin by summarizing the various theoretical predictions which correlate the expected neutrino flux with data from other messengers, specifically gammas and ultra-high energy cosmic rays. We then review the status and results of neutrino telescopes in operation and decommissioned, the methods used for data analysis and background discrimination. Particular attention is devoted to the challenge enforced by the highly uncertain atmospheric muon and neutrino backgrounds in relation to searches of diffuse neutrino fluxes. Next, we examine the impact of existing limits on neutrino fluxes on studies of the chemical composition of cosmic rays. After that, we show that not only do neutrinos have the potential to discover astrophysical sources, but the huge statistics of atmospheric muons can be a powerful tool as well. We end by discussing the prospects for indirect detection of dark matter with neutrino telescopes.

astro-ph.HE↗

arXiv2009

Rapporteur Summary of Sessions HE 2.2-2.4 and OG 2.5-2.7

The physics items presented in the HE 2.2-2.5 sessions include a variety of results concerning neutrino oscillations, dark matter and anti-matter, supernova neutrinos and proton decay. The OG 2.5-2.7 sessions concern detector R&D and operations in gamma and neutrino astronomy. I report here about a selection of the presented results.

hep-ph↗

arXiv2009

Neutrino Astronomy in the Ice

The South Pole is an optimal location for hosting astrophysical observatories. The status of the construction of the IceCube Observatory and some selected physics results will be discussed. Moreover prospects for detection of Ultra-High Energy cosmogenic neutrinos and techniques that can address this energy region will be considered.

astro-ph.IM↗

arXiv2009

Review on Neutrino Telescopes

I will discuss the motivations for Neutrino Astronomy and its prospects given the current experimental scenario, which is the main focus of this paper. I will also go through the first results of the IceCube detector deep in the ice and of the ANTARES undersea telescope underlying complementary aspects, common and different challenges. It is an exciting time for this science since the first completed undersea detector is successfully taking data and the first cubic kilometer detector is going to be shortly more than half-way from its completion in Antarctica.

astro-ph.IM↗

arXiv2008

The ANTARES underwater neutrino telescope

ANTARES is the first undersea neutrino telescope. It is in its complete configuration since May 2008 at about 2.5 km below the sea surface close to Marseille. Data from 12 lines are being analyzed and are producing first results. Here we discuss first analysis results for 5 lines and 10 lines, and we also comment on the performance of the full detector. We show that the detector has capabilities for discriminating upgoing neutrino events from the much larger amount of downgoing atmospheric muons and that data and simulation are in good agreement. We then discuss the physics reach of the detector for what concerns point-like source and dark matter searches.

astro-ph↗

arXiv2008

Charm Production in DPMJET

In this work, charm production in the {\sc dpmjet} hadronic jet simulation is compared to experimental data. Since the major application of {\sc dpmjet} is the simulation of cosmic ray-induced air showers, the version of the code integrated in the CORSIKA simulation package has been used for the comparison. Wherever necessary, adjustments have been made to improve agreement between simulation and data. With the availability of new muon/neutrino detectors that combine a large fiducial volume with large amounts of shielding, investigation of prompt muons and neutrinos from cosmic ray interactions will be feasible for the first time. Furthermore, above $\gtrsim 100$ TeV charmed particle decay becomes the dominant background for diffuse extraterrestrial neutrino flux searches. A reliable method to simulate charm production in high-energy proton-nucleon interactions is therefore required.

hep-ex↗

arXiv2008

Methods for point source analysis in high energy neutrino telescopes

Neutrino telescopes are moving steadily toward the goal of detecting astrophysical neutrinos from the most powerful galactic and extragalactic sources. Here we describe analysis methods to search for high energy point-like neutrino sources using detectors deep in the ice or sea. We simulate an ideal cubic kilometer detector based on real world performance of existing detectors such as AMANDA, IceCube, and ANTARES. An unbinned likelihood ratio method is applied, making use of the point spread function and energy distribution of simulated neutrino signal events to separate them from the background of atmospheric neutrinos produced by cosmic ray showers. The unbinned point source analyses are shown to perform better than binned searches and, depending on the source spectral index, the use of energy information is shown to improve discovery potential by almost a factor of two.

astro-ph↗

arXiv2007

Neutrino Flux from Cosmic Ray Accelerators in the Cygnus Spiral Arm of the Galaxy

Intriguing evidence has been accumulating for the production of cosmic rays in the Cygnus region of the Galactic plane. We here show that the IceCube experiment can produce incontrovertible evidence for cosmic ray acceleration by observing neutrinos from the decay of charged pions accompanying the TeV photon flux observed in the HEGRA, Whipple, Tibet and Milagro experiments. Our assumption is that the TeV photons observed are the decay products of neutral pions produced by cosmic ray accelerators in the nearby spiral arm of the Galaxy. Because of the proximity of the sources, IceCube will obtain evidence at the 5sigma level in 15 years of observation.

astro-ph↗

arXiv2006

IceCube: The state of the art

In this paper we describe the performance of the 9 instrumented IceCube strings and 16 surface IceTop stations taking data at the Geographical South Pole after 2 deployment seasons. We will focus on the description of the array and on the construction and data analysis status. The expected full array performance is discussed and compared to other results for the relevant physics studies using high energy neutrinos for astrophysical neutrino searches.

astro-ph↗

arXiv2006

Microquasar LS 5039: a TeV gamma-ray emitter and a potential TeV neutrino source

The recent detection of TeV gamma-rays from the microquasar LS 5039 by HESS is one of the most exciting discoveries of observational gamma-ray astronomy in the very high energy regime. This result clearly demonstrates that X-ray binaries with relativistic jets (microquasars) are sites of effective acceleration of particles (electrons and/or protons) to multi-TeV energies. Whether the gamma-rays are of hadronic or leptonic origin is a key issue related to the origin of Galactic Cosmic Rays. We discuss different possible scenarios for the production of gamma-rays, and argue in favor of hadronic origin of TeV photons, especially if they are produced within the binary system. If so, the detected gamma-rays should be accompanied by a flux of high energy neutrinos emerging from the decays of π^\pm mesons produced at pp and/or p γinteractions. The flux of TeV neutrinos, which can be estimated on the basis of the detected TeV gamma-ray flux, taking into account the internal γγ\to e^+e^- absorption, depends significantly on the location of gamma-ray production region(s). The minimum neutrino flux above 1 TeV is expected to be at the level of 10^{-12} cm^{-2} s^{-1}; however, it could be up to a factor of 100 larger. The detectability of the signal of multi-TeV neutrinos significantly depends on the high energy cutoff in the spectrum of parent protons; if the spectrum of accelerated protons continues to 1 PeV and beyond, the predicted neutrino fluxes can be probed by the planned km^3-scale neutrino detector.

astro-ph↗

arXiv2005

TeV photons and Neutrinos from giant soft-gamma repeaters flares

During the last 35 years three giant flares were observed from so-called Soft Gamma Repeaters (SGR's). They are assumed to be associated with star-quakes of pulsars accelerating electrons and, possibly, protons to high energy in the huge magnetic fields as inferred from the observations. Because of this and the observation of non-thermal emission it has been speculated that they may be cosmic ray accelerators producing gamma-rays up to TeV energies. Neutrino telescopes, such as AMANDA and the ANTARES now under construction, could be used as TeV-gamma detectors for very short emissions by measuring underground muons produced in $γ$ showers. We estimate signal and background rates for TeV photons from SGR giant flares in AMANDA, and we provide an estimate of the gamma shower events that Milagro could detect. Moreover, we consider that, if hadrons are accelerated in these sources, high energy neutrinos would be produced together with photons. These may be detected in neutrino telescopes using neutrino-induced cascades and upgoing muons. We argue that the Antarctic Muon and Neutrino Detector Array AMANDA may have observed the December 27, 2004 giant flare from the soft gamma-ray repeater SGR 1806-20 if the non-thermal component of the spectrum extends to TeV energies (at present the actual data is subject to blind analysis). Rates should be scaled by about two orders of magnitude in km3 detectors, such as IceCube, making SGR flares sources of primary interest.

astro-ph↗

arXiv2004

Effect of neutral current interactions on high energy muon and electron neutrino propagation through the Earth

High energy electron and muon neutrino propagation through the Earth has been performed using the Monte Carlo technique. We focused our attention on the effect of neutral current deep inelastic interactions compared to that of charged current ones. We have found that NCs do not produce any significant effect with respect to the case in which only CCs are considered. Therefore we conclude that NC interactions can be neglected without considerable loss of accuracy. When computing upward-going neutrino fluxes a simple formula describing the transmission probability, that depends on the neutrino direction and energy and the CC cross section, can be used to account for the Earth shadowing effect.

hep-ph↗

arXiv2004

Neutrino Astronomy with ANTARES

ANTARES is a project aiming at the operation of an underwater detector at a depth of 2.5 km close to Toulon in the South of France. The detector is expected to be completed at the beginning of 2007. The main purpose of the experiment is the detection of high energy neutrinos produced in astrophysical sources. Being weakly interacting, neutrinos could potentially be more powerful messengers of the universe compared to photons, but their detection is challenging. The technique employs phototubes to detect the arrival time and the amplitude of photons emitted by neutrino charged secondaries due to the Cherenkov effect. ANTARES will contribute significantly in the field of neutrino astronomy, observing the Galactic Centre with unprecedented pointing capabilities.

hep-ex↗

arXiv2004

Propagation of tau neutrinos and tau leptons through the Earth and their detection in underwater/ice neutrino telescopes

If muon neutrinos produced in cosmological sources oscillate, neutrino telescopes can have a chance to detect tau-neutrinos. In contrast to muon neutrinos the Earth is completely transparent for tau neutrinos thanks to the short life time of tau-leptons produced in charged current interactions. Tau-lepton decaysin flight producing another tau neutrino (regeneration chain). Thus, tau neutrinos cross the Earth without being absorbed, though loosing energy both in regeneration processes and in neutral current interactions. Neutrinos of all flavors can be detected in deep underwater/ice detectors by means of Cherenkov light emitted by charged leptons produced in neutrino interactions. Muon and tau-leptons have different energy loss features, which provide opportunities to identify tau-events among the multitude of muons. Some signatures of tau-leptons that can be firmly established and are background free have been proposed in literature, such as 'double bang' events. In this paper we present results of Monte Carlo simulations of tau-neutrino propagation through the Earth accounting for neutrino interactions, tau energy losses and tau decays. Parameterizations for hard part and corrections to the soft part of the photonuclear cross-section (which contributes a major part to tau energy losses) are presented. Different methods of tau-lepton identification in large underwater/ice neutrino telescopes are discussed. Finally, we present a calculation of tau neutrino double bang event rates in cubic km scale detectors.

hep-ph↗

arXiv2003

High Energy Neutrino Astrophysics

Astroparticle physics is a field rich of perspectives in investigating the ultra-high energy region which will never be accessible to man made machines. Many efforts are underway in order to detect the first cosmic neutrinos, messengers of the unobserved universe. The motivations of this field of research, the current and next future experimental status are reviewed.

astro-ph↗