The Scientific Fair is an informal get-together among people who work in the field of astroparticle phyiscs: students, researchers and academics of the GSSI, of the University of L'Aquila and the National Labs of Gran Sasso.
On Nov. 7 we are going to welcome the new students (GSSI Library).
On Nov. 8 the meeting involves LNGS and UNIVAQ researchers and academics (GSSI Library).
On Nov. 9 the GSSI students of the XXX PhD cycle are going to present their theses in GSSI Main Lecture Hall, according to the following schedule:
- 15.00 M.Celoria
- 15.15 V. Della Rocca
- 15.30 M. Durocher
- 15.45 J-P. Fontaine
- 16.00 S. Haridasu
- 16.15 A. Mandarano
- 16.30 L. Pagnanini
- 16.45 A. Palladino
- 17.00 C. Savarese
- 17.15 A. Subramanian
- 17.30 S. Tiwari
- 17.45 G. Wang
In my thesis, I study the effective description of self-gravitating continuous media as a tool for modified gravity. Particularly, I investigate both the theoretical aspects (symmetries, stability, thermodynamics) and the phenomenological applications in cosmology and astrophysics, in order to describe the dark sectors of the Universe.
Valeria Della Rocca
Following the recent developments in the description of light even-even nuclei within the framework of the cluster model, we propose an extension of this model in the case of odd-even nuclei. Having in mind applications to 9Be, 13C and 17O, we discuss the single particle energy levels of a fermion in the potential generated by 2, 3 and 4 clusters assumed to have Z2, D3h and Td point group symmetry, respectively. The two cluster configuration is then further investigated. We are able to compute the energy spectrum and the wave functions of 9Be and to evaluate electromagnetic transition rates and form factors. Finally, we provide a comparison with the currently known experimental data.
The KM3NeT is the next generation neutrino telescope to be installed in the Mediterranean Sea. It will have a detector volume of several cubic kilometres of sea water. The KM3NeT Research Infrastructure will host two di_erent neutrino detectors: the Oscillation Research with Cosmics in the Abyss (ORCA) detector which will be located 40 km o_shore Toulon (France) and is optimised for the study of atmospheric neutrino oscillations; whereas the Atroparticle Research with Cosmics in the Abyss (ARCA) detector will be located 80 km offshore Capo Passero (Italy) and is dedicated to the search for very high-energy cosmic neutrinos and to explore the IceCube signal using different methods. The Phase-1 of ARCA will incorporate 24 strings and later on the Phase-2 will consist of two building blocks, each composed of 115 detection strings. An array of thousands of sentitive optical sensors will detect the faint Cherenkov light produced by relativistic charged particles emerging from neutrino interactions in order to reconstruct the direction of the neutrinos and attemps to associate them with distant astrophysical sources.
Using Monte Carlo simulations, a performance analysis will be carried out for the Phase-1 of the ARCA installation. It focuses on the neutrino diffuse flux using two track reconstruction methods. Firstly, the neutrino effective area and volume are obtained. Secondly, applying the Feldman-Cousins method and assuming the IceCube isotropic diffuse neutrino flux, the minimal flux normalisation factor is obtained for a 10 year period. And thirdly, the likelihood ratio test will be carried out.
In this thesis, we investigate the nature and localization of dark matter in galaxies. It has been proved that dwarf galaxies are amongst the most dark matter dominated galaxies, even in the inner regions. It has also been widely studied that their dark matter profile tends to be more cored (Burkert for instance) than cuspy (NFW for instance). The thesis will be to exergue some methodologies to study dark matter in these galaxies as well as in the others. For dwarf irregulars, and bright compact dwarfs, we look for possible radial Tully-Fisher relations. It has been proved in the past (Salucci and Yegorova, 2007) that the radial Tully-Fisher relations can be investigated in regular spirals and can lead to conclusions about the localization and nature of the dark matter in these galaxies. A similar work is done in this thesis for dark-matter dominated objects. Later on, we will investigate other means to study dark matter for other types of galaxies like ellipticals for which the Tully-Fisher relations cannot hold.
The technical advancement of observational cosmology in the last few decades has helped us to collect a wealth of data. In particular, the Cosmic Microwave Background (CMB) anisotropies have played a very crucial role in the modelling of our universe. In contrast to the CMB at the early-times, several low-redshift observations such as Supernova type Ia (SN Ia) and Baryon Acoustic Oscillations (BAO) have come to aid in understanding the late-time evolution of our universe. Owing to these observations, the current accelerated expansion phase of the universe has come to light, which initiated the need to have an extra component, often referred to as "Dark Energy" (DE), prior to which a universe consisting of baryons and cold dark matter was the model of interest. The exotic features of DE led to a cascade of theoretical scenarios. Among these, the simple cosmological constant model (_CDM) stands out as it remarkably _ts in concert with both CMB and low-redshift observations. The current work is aimed to understand better the DE component, by using the available cosmological data-sets such as CMB, supernova, measurements of the expansion rate of the universe, BAO etc. Which will be followed by testing the validity of the cosmological models given the combination of di_erent data-sets and to check model performance. Model preference to these data-sets can be tested via statistical analysis, which will give us insight into nature of DE, such as the equation of state, contribution to the total energy density of our universe etc. As a second part of this thesis, We study the dark matter halo density pro_les speci_cally aimed for the galaxy-galaxy lensing data. The choice of a speci_c DM halo density pro_le such as NFW or Burkert pro_le have signi_cant e_ect on the theoretical estimation of the lensing signal. It is important to test the di_erent models with the data, to understand better the nature of the dark matter.
WIMPs detection is a challenging topic in astroparticle physics. Among the many technologies developed throughout the years, a very promising detection technique consists in observing the light produced by nuclear recoils of WIMPs with a sensitive target. The DarkSide-50 experiment makes use of a dual-phase time projection chamber _lled with liquid Argon (LAr-TPC), in which the light is collected by 38 cryogenic low-radioactivity photomultiplier tubes. For the next step of the DarkSide program, DarkSide-20k, the photomultiplier tubes will be replaced with tiles (i.e. SiPM arrays) designed to operate at cryogenic temperature with high quantum e_ciency. The R&D performed on the SiPMs will be reported, including the characterization at cryogenic temperatures of the devices that were tested, together with the next steps about the realization of the tiles and the study of their performance in a small-scale test detector at LNGS.
CUPID-0 will be the first array of scintillating bolometers, made with 95%- enriched crystals, for 0vBB decay search. The assembly ended in October and the data taking is planned to start before the end of this year. All the phases of the CUPID-0 project, from the material selection to the data analysis, will be detailed. Moreover the first limit on the half-life of the 0vBB decay of 82Se, obtained with the available data, will be calculated to fine tune the analysis tools developed in view of a next generation experiment.
The discovery of high energy extraterrestrial neutrinos, provided by the IceCube collaboration, has opened a new era for the neutrino astronomy. Anyway this is a newborn discipline, since lots of questions are still without an answer. First of all, we do not know the origin of these neutrinos. It is probable that they are of extragalactic origin, due to the almost isotropic distribution of events, but there are no reasons to exclude also a possible Galactic origin of a certain fraction of IceCube neutrinos. Moreover, also assuming the extragalactic origin it is very hard to associate a speci_c source. Some candidates were proposed, such as Blazars, AGN, Gamma Ray Burst but the correlations with the direction of neutrinos are weak. Before to discuss these aspects a theoretical background is proposed, discussing the mechanisms of production of high energy neutrinos, their propagation and their interaction with the detector. The intent is to provide a review of the present situation in the field of high energy neutrinos.
Silicon PhotoMultipliers (SiPM) are a new promising technology in the photo-detectors sector. They are used in a wide range of scientific fields, ranging from medical applications to particle and astro-particle physics. In particular SiPMs result to be a strong candidate for the next generation of multi-ton noble liquid detectors for neutrino physics and dark matter searches due to their extremely low radioactivity: this feature will allow to push forward the sensitivity of this kind of experiments which require the lowest background possible. Higher photon detection efficiency (PDE) and resolution with respect to traditional photo-tubes are also valid reasons to switch to this innovative technology in the near future. The first scientific activities of this thesis work consisted of cryogenic characterization of SiPM prototypes produced at FBK. More recent work was done toward the objective to assemble a 25 cm^2 array made of SiPMs (Tile) to be readout as a single channel. The challenge of this task lies in the pre-amplification stage of such a device, which will be immersed in liquid argon together with the tile itself. Signal to noise ratio has to be kept at an acceptable level, together with a reasonable bandwidth to preserve the timing information lying in the signal. With the most recent developments we achieved such results with a 12 cm^2 array. Other activities are planned, such as PDE measurements of single SiPMs at cryogenic temperatures. Finally, a C++ based simulation of the full electronic chain and DAQ system is helping in studying the impact of the SiPMs and electronics noises on the performances of the detector. It is also used in the DAQ logic design process and studies are planned for electron/nuclear recoil discrimination optimization.
In the thesis investigations are done on various statistical models to explain the structure and formation of the galaxies. To do this we employ the kinematics of stars in the central region and various tracers ranging from globular cluster to Planetary nebule out to a large radii where they are dark matter dominated.This in turn leads to the constraining mass profiles of galaxies. Specially we investigate the case of elliptical galaxies where dark matter dominance is observed and several studies have indicated the presence of Cored dark matter profile as opposed to the classic NFW profile as obtained from simulations.
We are living in the era of gravitational waves astronomy, the two events of binary black hole mergers detected by the LIGO is already starting to fill up the gravitational waves sky. VIRGO detector in Italy is expected soon to join two LIGOs and hence improving the sky localisation of the observed event. These are exciting times for astronomy as we expect more of such sources and hopefully some surprises to be seen in era of advanced detectors.
Gravitational waves transient signals can be classified practically as compact binary coalescence (CBC) and generic short and long duration transients (bursts), the search techniques/algorithms for them differs on various levels and hence the background and sensitivity for both these searches are quite different, however even when they target different sources, they are not completely mutually exclusive of each other, this means the same source can be captured by both CBC and bursts searches but not always.
I am currently exploring the parameter space for the poorly modelled and un modelled signals (in particular eccentric black hole binaries) studying their detectability, estimating parameters and interpretation with current generation of gravitational waves interferometers.
I am also involved in the understanding how we can use neutrinos to trigger GWs searches for core collapsing stars and detecting late time quasi normal modes of binary black hole mergers from multiple detections.
The success of the first Advanced LIGO observing run opened the gravitational wave (GW) astronomy era. In the meantime, multimessenger astronomy is entering a new era. During the first run, two unambiguous events, GW150914 and GW151226, and one lowersignificant event, LVT151012 were detected, all identified as binary black holes coalescences. So far, binary neutron stars (BNS) and neutron star-black hole (NSBH) merger as the putative progenitor of short Gamma-Ray Burst (GRB) are not yet detected. Nevertheless, with the improvement of GW detector sensitivity and continuous observations, the BNS and NSBH coalescence is expected to be detected by Advanced LIGO and Advanced Virgo in the coming years. The joint search for the GW and electromagnetic (EM) radiation will boost the understanding of physical processes behind the compact binary system coalescences. Simulations of joint observations with the forthcoming GW detector network configurations and gamma-ray telescopes show the realistic scenarios of neutron star compact binary coalescence associated with GW and gamma-ray. Some new simulation results to demonstrate the prospects for GW and GRB coincidence observations will be reported in my thesis.