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Dark matter bound states: where do we stand?

In a variety of theories, Dark Matter (DM) interacts with gauge bosons or scalars that induce long-range interactions because of repeated soft exchanges. Remarkably, the inclusion of bound-state effects for DM annihilation has been recently shown to have a large impact on the relic density and, therefore, on the parameters of a given model to be compatible with observations. At the same time, it is manifestly subtle and complicated to include bound-state dynamics in a thermal medium due to the intricate interplay between non-relativistic and thermal energy scales. Starting from a thermal field theoretical formulation of the problem, we use an effective field theory approach to describe bound-state formation and dissociation, Sommerfeld effect, DM thermal masses and interaction rates. We show the phenomenological impact of such framework for wimp-like models with mediators to the visible sector. Moreover, we discuss some shortcomings in the current rate equations that limit the validity of existing results in the literature for even simpler dark matter models.

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8th Low Emittance Rings Workshop

The 8th Low Emittance Rings Workshop will be held in Frascati, INFN-LNF on 11-13 March 2020, supported by the ARIES project. The goal of the workshop is to bring together experts from the scientific communities working on low emittance lepton rings. The workshop is sponsored by the RULE network under the ARIES European project and includes light source storage rings, linear collider damping rings and future e+/e- circular colliders. The theme will be beam dynamics and technology challenges for producing and controlling ultra‐low emittance beams and the participants will benefit from the experience of colleagues who have designed, commissioned and operated such rings. Workshop sessions will include: ‐ Low Emittance optics design and tuning (LERD) – Collective Effects and beam instabilities (IICE) – Low Emittance Ring Technology (LERT) Students are encouraged to participate. A Student Poster Session is forseen starting on the first Workshop day. A prize will be awarded to the best student presentation to allow the participation in a major conference presenting works related to Low Emittance Rings. The programme will be organised by the Scientific Programme Committe: Maher Attal, SESAME Ryutaro Nagaoka, SOLEIL Riccardo Bartolini, JAI & Diamond Light Source Yannis Papaphilippou, CERN – Chair Gabriele Benedetti, ALBA Qing Qin, IHEP Mike Borland, ANL Victor Smalyuk, BNL Susanna Guiducci, INFN-LNF Andreas Streun, PSI Robert Hettel, SLAC Rainer Wanzenberg, DESY Emanuel Karantzoulis, ELETTRA Simon White, ESRF Simon Leeman, LBNL Frank Zimmermann, CERN Akira Mochihashi, KIT                                                                                                                       ************************** Proposals for contributions to the workshop could be addressed ...

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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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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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Graphene Wormholes: From General Relativity to Nano-technologies

We propose a model describing the evolution of free electron current density in graphene giving rise to bidimensional wormhole solutions. Based on analogue concepts of General Relativity, we perform the analysis using the difference between curvatures of parallel and antiparallel spins. In such a framework, effective “gravitons” emerges in the form of gauge fields exchanged between electrons. In a plain grapheme system, the curvatures produced by both kinds of spins neutralize each other giving rise to no conduction. However, in the presence of geometrical defects of the graphene sheets, the inequality between curvatures leads to the emergence of current densities and conductivity in a wormhole solution. Depending on the type of defects, the resulting current density can be negative or positive. Possible applications are discussed.

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Photothermal Lens Spectroscopy: A Highly Sensitive Technique for Characterization of Low Absorbing materials

In order to characterize low absorbing materials, where UV-vis spectrophotometry does not provide enough sensitivity, other more sensitive methods are needed. Photothermal lens technique is a very sensitive method to detect and photothermal characterize of materials. The thermal lens technique measures the amount of heat generated followed by the absorption of light in a sample. The heat produces a temperature gradient in the medium which generates a spatial refractive index gradient called a thermal lens. The performance of this method and applications such as photocatalytical degradation of dyes as well as the photothermal characterization of plasmonic nanostructures, quantum dots and graphene are presented.

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