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Fermi and multi-messenger observations

Multi-messenger astronomy turned into a reality in the past five years, with the first detection of Gravitational Waves in 2015, the first gravitational and electromagnetic observations of the coalescence of neutron stars in 2017, the first evidence of a common source of neutrinos and energetic photons from a distant galaxy in 2017. The Fermi telescope, operating as an all-sky monitor for high energy gamma-ray transients, is central to such observational efforts which include a large community of different observatories. In this seminar I will review the scientific context, the current observational scenario and the future prospects for Fermi and other players of this global endeavor.

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Fourth Rome Physics Encounter @LNF

The encounter is postponed until further notice following the restrictions from INFN regarding organised meetings.   This informal meeting is the fourth of the Rome physics encounter series. It aims at bringing together young speakers working or collaborating with the research groups in the Rome area. In the spirit of workshops and conferences at LNF, talks will be presented in a pedagogical way and plenty of time is scheduled to allow discussions among participants. The encounters will be synchronised with a selected LNF General Seminar, held in the afternoon at 2.30pm. The lunch is offered to all registered participant at the LNF canteen.

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Universal Rainbow Channeling Potential

The problem of an accurate ion-solid interaction potential is one of the basic problems in description of the ion-solid interaction [1]. It has been shown how one can construct the universal rainbow channeling proton-crystal interaction potential [2]. It has been done by modifying the Moliere’s interaction potential applying the crystal rainbow theory [3, 4]. This potential merges the ZBL potential, for the small impact parameters, and the Molière’s potential, with the Thomas-Fermi radius, for the large impact parameters. The accuracy of the obtain interaction potential should be investigated in a series of high resolution transmission channeling experiments for different proton-crystal combinations. Further, application of the presented rainbow morphological method for 5 keV protons transmitted through a graphene [5] and generally through 2D materials has been disused. [1] M. Nastasi, J. W. Mayer and J. K. Hirvonen, Ion-Solid Interaction: Fundamentals and applications (Cambridge University Press, Cambridge, 1996). [2] S. Petrović, N. Starčević and M. Ćosić, Universal axial (001) rainbow channeling interaction potential, Nuclear Instruments and Methods in Physics Research B, 447, pp. 79-83 (2019). [3] S. Petrović, L. Miletić, and N. Nešković, Theory of rainbows in thin crystals: the explanation of ion channeling applied to Ne10+ ions transmitted through a <100> Si thin crystal, Phys. Rev. B 61, 184 (2000). [4] N. Nešković, S. Petrović, and M. Ćosić, Rainbows in Channeling of Charged Particles in Crystals and Nanotubes (Springer Nature, Cham, 2017). [5] M. Ćosić, M. Hadžijojić, M, Rymzhanov, S. Petrović and S. Bellucci, Investigation of the graphene thermal motion by ...

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Machine learning an unknown physical law: the structure of the proton

Machine learning techniques are increasingly used for recognizing pattern and devising optimal strategies: situations in which the machine is taught (or teaches itself) to learn a known correct answer, or the best use of known rules. In particle physics, machine learning has been used now for several years  in order to determine an underlying physical law which is known to exist, but which is unknown. Furthermore, because elementary particles are quantum objects, this law is stochastic in nature: the machine has to learn a probability distribution, rather than a unique answer. I will discuss some classic results, used among others in the discovery of the Higgs boson, as well as recent developments, which raise the fundamental question of how to decide whether an answer is correct.

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Third Rome Physics Encounters @LNF

This informal meeting is the third of the Rome physics encounter series. It aims at bringing together young speakers working or collaborating with the research groups in the Rome area. In the spirit of workshops and conferences at LNF, talks will be presented in a pedagogical way and plenty of time is scheduled to allow discussions among participants. The encounters will be synchronised with a selected LNF General Seminar, held in the afternoon at 2.30pm. The lunch is offered to all registered participant at the LNF canteen.

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SHERPA: “Slow High-efficiency Extraction from Ring Positron Accelerator”

The SHERPA project aim is to develop an efficient technique to extract a positron beam from one of the Frascati DAΦNE collider rings, setting up a new beam line able to deliver positron spills of O(ms) length. An excellent beam energy spread and emittance, with a strong reduction of the background and the pile-up for the user experiments, will be achieved. The most common approach to extract from a ring is to use a resonant technique, creating an unstable region in the phase space and then driving the tune towards the separatrix, in order to gradually eject particles from the circulating beam. SHERPA proposes instead to use coherent processes in bent crystals to kick out positrons from the ring, a cheaper and less complex alternative. This non-resonant technique, already successfully used and still developed mainly in hadron accelerators, will provide a continuous multi-turn extraction with high-efficiency. Realizing this for < GeV leptons is challenging, however will provide the first primary positron beam obtained with crystal extraction. At the DAΦNE Beam Test Facility, < GeV positrons have already been deflected using crystals, proving the technique feasibility.  An immediate application of this new extracted beam line would be the PADME experiment, already running at the BTF, but currently strongly limited by the duty cycle. Using the proposed extraction, PADME could increase the statistics by a factor 104 and its sensitivity by a factor 102, extending the discovery potential at the forefront level. SHERPA could provide a unique new beam test facility, very competitive ...

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Collider searches of charged scalars in context of Type-II Seesaw Model

The discovery of the Higgs boson at the Large Hadron Collider (LHC) has experimen-tally proven that charged fermions and gauge bosons get masses after spontaneous breaking of electroweak symmetry. However, one of the key questions that still remains unexplained is the origin of light neutrino masses and mixings. A number of neutrino oscillation experiments have observed non-zero solar and atmospheric neutrino mass splittings. Which implies that neutrinos have tinny but non-zero mass. Seesaw mechanism is one the profound theory to explain the smallness of neutrino mass. In this talk I will discuss about different types of seesaw model. Mainly I will focus on Type-II seesaw model and collider searches of charged scalars in this model.

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The universe acceleration in modified gravity: an overview

General introduction to cosmology of modified gravity is given. It is shown that different forms of modified gravity are possible, many of them being consistent with Solar system tests and cosmological bounds. Special attention is paid to the so-called F(R) modified gravity. It is shown that such a theory may naturally describe the early-time inflation with late-time acceleration (dark energy epoch). Realistic versions of F(R) gravity are proposed and the inflationary indices are shown to be consistent with Planck experiment. New ghost-free versions of modified gravity are introduced and their cosmological evolution is studied. It is shown that it may naturally give the unification of inflation with dark energy, while the scalar field which appears there plays the role of dark matter. 

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