Shortlinks
  Introduction
  Telescope Calibration
  Mirror Technologies
  Dark Matter Searches
  Atmospheric Calibration

Research Interests
Introduction. Gamma-ray Astrophysics with MAGIC and CTA telescopes
Gamma-ray astrophysics at the TeV from ground-based Imaging Atmospheric Cherenkov telescope (IACTs), takes profit of the Cherenkov light emitted during elec- tromagnetic atmospheric showers initiated by primary gamma-rays in the top atmo- sphere (and cosmic rays in general). From the very first detection of the Crab Nebula by the Whipple experiment in the 1989, the field has now reached a mature stage, with several installations around the world (mainly HESS, MAGIC and VERITAS), and more than a hundred TeV sources established. IACTs are instruments for gamma-ray astronomy at galactic and extragalactic objects like pulsar, binary systems, micro- quasars and active galactic nuclei. Nevertheless, gamma-ray studies can provide signatures of other interesting topics, namely the cosmic horizon, dark matter signa- tures, Lorentz Invariance violations, cosmic-ray physics and so on. The MAGIC experiment is currently composed by a couple of telescopes of big size, that allowed to investigate the lowest energies below 100 GeV, among the other ex- periments of its kind. It is well-known for the observation of the farthest blazars ever observed at TeV and for the detection of the Crab pulsar spectrum over three decades in energy where a spectral cutoff was expected by other experiments1 as well the most constraining results on TeV cosmic ray emission from galaxy clusters and from dark matter annihilations signature at dwarf spheroidal galaxies. CTA is a project for a new generation of Cherenkov telescope which advanced per- formance in terms of energy coverage, sensitivity, and instrument robustness. Unlike current experiment, it will be run as an observatory, thus providing data to the world- wide scientific community. It is in the Prototyping Phase now, and expected to be built in few years from now2

Calibration System of the MAGIC I telescope [2004]
At Institut de Fisica d’Altes Energies (IFAE, Barcelona, Spain), I followed the characterization of the calibration system of the MAGIC telescope in its commissioning phase, flanked to Markus Gaug. Ultra-fast avalanche transistors were used to switch LEDs at different wavelengths to simulate the fast (2 ns) pulses of Cherenkov light from atmospheric showers. The characteri- zation of the response of the calibration system and the analysis of the first calibration runs were performed. The main results of the study was, besides commissioning, that the best calibration could be obtained with a combination of LEDs that better resembles the spectrum of Cherenkov light after atmospheric absorption. The diploma thesis was performed under the supervision of Manel Martinez3 2004

Mirrors and optics for MAGIC and CTA [ 2006–2009]
IACTs demand robust mirrors with environmental ruggedness because of its constant exposure. Their large reflectors are usually tessellated with numerous mirror facets. For the MAGIC collaboration, I coordinated the design, production, test–phase, optical characterization and installa- tion of mirrors on the second MAGIC telescope (MAGIC-II), which started operation in 2009. MAGIC II INFN mirrors are 1 m2 square, all–aluminum sandwich, composed of two aluminum plates interspaced by a honeycomb layer which provides rigidity, good heat transmission and light–weight4. The optical quality of these facets is very high: mean reflectivity larger than 85% in the Cherenkov wavelengths (mainly 300-600 nm), weight reduced to 18 kg/m2, very reduced reflectivity loss (< 1%/year) and good me- chanical stability. I followed the optics qualification of the MAGIC II reflector thorough ray–tracing simulations and headed the installation of MAGIC II mirrors in 2007-2008. CTA (Cherenkov Telescope Ar- ray) is a developing project for a new generation of Cherenkov telescopes, extending the capabilities of the IACT technique as a result of the effort of world-wide gamma- ray community. The CTA mirror working group is responsible for a) definition of tech- nologies for mirror facets, b) definition of technology for mirror surface protection, c) creation of facilities for mirror massive test and performance characterization8. I was co-coordinator of the activities within this group together with Andreas Foerster and Mose’ Mariotti. In Padova, we are currently developing new technology mirror the Large Size Tele- scope of CTA, with huge size (1.5 m diameter flat-to-flat hexagons) and composite design with prealuminated glass layers interspaced by steel cilinders.

Dark Matter searches with MAGIC and CTA. [2006–today]
I was the principal investigator (PI) for three campaigns of observation of candidate sources of dark matter (DM) with the MAGIC telescope. The PI is responsible for defining the scientific case, following observation and data analysis and curing the edition and publication of the data. In 2006, I proposed the observation of steady unidentified EGRET sources as puta- tive intermediate mass black holes (IMBHs), in the scenario proposed by Bertone et al. (Phys.Rev.D72:103517,2005). A source was observed in 2006. Unfortunately, the telescope was undergoing major technical problems that prevented us from publica- tion of these data. Only upper limits were derived. A description of the analysis can be found in the Diploma Thesis of a F. Zandanel which I followed as co-advisor5. In 2008 I was the PI of the observation of Willman 1 with MAGIC. Willman 1 is one of the ultra–faint satellite galaxies with higher DM concentration (Strigari et al. arXiv:0709.1510 [astro-ph]). It was observed in 2008 for 15 hours with MAGIC. Upper limits were derived for few benchmarks neutralino models showing that prospects of detection are positive only under the assumption of relevant boosts in the models. The results were published6. Another ultra-faint satellite galaxy was observed by MAGIC between 2009 and 2010, for a total of 42 h. The source — Segue 1 — is considered among the best candidates for observation of dark matter. Despite the null detection, upper limits were produced to constrain the parameter space of some dark matter models, which were followed by the recent publication of the paper7. From 2010 to 2014, I am convener of the Astroparticle and Fundamental Physics working group. The physics covers the topics of dark matter searches, searches with cosmic ray particles, searches of pu- tative Lorenz Invariance variations and other exotic physics, like axion-like particle physics. The task of the convener is that of coordinating the proposals of observation, and follow the datataking and publication phases. In 2008, in the context of MAGIC II and CTA, the following aspects were interesting to study: a) which technical aspects may influence the detection of DM for IACTs, b) how much the increase in sensitivity and decrease of energy threshold affects the prospects of detection, c) that the internal bremm- strahlung mechanism (Bringmann et al, JHEP 0801:049,2008) introduces features in the gamma–ray spectrum that affect the detection probabilities for different mod- els of neutralino; d) which are most probable regions of the parameter space of the neutralino for observation or constraints9 I was also convening the Dark Matter and Fundamental Physics working group of CTA, together with Christian Farnier. The pur- pose of the group is currently determine which experimental characteristics are best suited for fundamental physics observation, in terms of minimum requirements and goals, begin the CTA array still in its design phase. The outcome of these studies is published in the Astroparticle Physics journal^10

Atmospheric Calibration for IACTs [2010-today]
. For CTA, it is of fundamental importance to improve the energy calibration and in general reduce the systematics (which currently state around 30%). This effort is pursued by the Atmospheric Monitoring and Cali- bration (ATAC) working group, of which I am member. For this purpose, at Barcelona, a novel–design Raman LIDAR (LIght Detection and Ranging) is currenly under con- struction by refurbishing a dismissed CLUE telescope. The hardware development is done in collaboration with the Institut de Fisica des Altes Energies (IFAE) also in Barcelona. The use of a LIDAR together with a deeper monitoring of the atmosphere will allow to increase the performance of CTA and its duty cycle. I am currently the convener of the Atmospheric Calibration working package in CTA whose role is to set up the activities towards a full centralized calibration of CTA with the information from several devices to measure the atmospheric transparency.

References
1 M. Doro, “Reaching the lowest energy threshold of ground-based Cherenkov telescopes with MAGIC-stereo: a goal achieved”,
2 M. Doro, “CTA—A Project for a New Generation of Cherenkov Telescopes”, NIM A 630 2011.
3M. Doro “The Commissiong and Characterization of the Calibration System of the MAGIC Telescope” Bachelor Thesis
4 M. Doro et al.. "The reflective surface of the MAGIC telescope", NIM A, 595-1, 200-203.
5 F. Zandanel, ‘Dark Matter Search with the MAGIC Telescope: Analysis of the Unidentified EGRET Source 3EG J1835+5918”, Univ. Padova 2007.
6 M. Doro for MAGIC Coll., "Upper Limits on the VHE Gamma-Ray Emission from the Willman 1 Satellite Galaxy with the Magic Telescope", Astroph. J., 697-2, 1299-1304 (2009)
7 MAGIC Coll., "Searches for Dark Matter Annihilation Signature in the Segue 1 satellite galaxy with the MAGIC-I telescope”, JCAP 016 (035) 2011 8 M. Doro, "Mirror Facet Technologies for the Telescopes of the CTA Observatory", 31st ICRC 2009, Lodz, Poland,