Colóquios

  • A sterile neutrino solution to B-physics anomalies

    Enviado por malcanta em qui, 17/10/2019 - 17:41
    Data: 
    22/11/2019 - 11:00
    Palestrante: 
    Daniele Barducci - University Roma - La Sapienza and INFN
    Resumo: 

    I discuss a combined explanation of charged- and neutral-current
    B-physics anomalies which assume the presence of a light sterile neutrino
    state. Two simplified scenario are considered: a scalar and a vector
    leptoquark model. While at present both models are compatible with direct
    LHC searches and low-energy flavor measurements, already with 300/fb of
    data the LHC will be able to completely test parameter space.
    I will then discuss the cosmological constraints on the sterile neutrino
    state and the conditions under which it can be a Dark Matter candidate.

    Local: Sala Jayme Tiomno

  • B-physics anomalies: a road to new physics?

    Enviado por malcanta em seg, 19/08/2019 - 13:30
    Data: 
    23/08/2019 - 12:00
    Palestrante: 
    Dr. Olcyr Sumensari (INFN Padova)
    Resumo: 

    Even though the LHC searches so far did not unveil the new physics particles, observations made at the LHC and at the B-factories point towards lepton flavor universality violation in both tree-level and loop-induced B-meson semileptonic decays. If confirmed with future data, these would be an unambiguous manifestation of new physics at colliders. After a brief review of the current status of these anomalies, I will discuss general implications that can be derived by using (i) an effective field theory approach and (ii) specific leptoquark models.

    Local: Sala Jayme Tiomno

  • Procura por decaimento duplo beta sem neutrino com o detector EXO-200

    Enviado por cblanco em ter, 06/08/2019 - 12:43
    Data: 
    16/08/2019 - 12:00
    Palestrante: 
    Prof. Caio Licciardi (Laurentian University; nEXO and EXO-200 Collaborations)
    Resumo: 

    O programa EXO (Enriched Xenon Observatory) investiga a natureza dos neutrinos através do decaimento duplo beta sem neutrinos (0vBB) usando uma câmara de projeção temporal com Xenônio líquido enriquecido. O detector EXO-200 terminou com sucesso duas fases de tomada de dados em dezembro de 2018 na mina de sal e lixos nucleares Waste Isolated Pilot Plant, em Carlsbad NM, nos Estados Unidos. Na primeira fase, o detector foi o primeiro a observar o decaimento beta duplo com neutrinos (2vBB) em 136Xe, e hoje ainda possui a medida mais precisa de sua meia vida: 2.165 ± 0.016 ± 0.059 x 10^21 anos. Além de vários outros resultados, a colaboração possui os melhores limites do mundo nos processos de 2vBB e 0vBB em 134Xe. Usando a exposição total do detector, a procura por 0vBB em 136Xe foi atualizada em 2019 na qual a resolução de energia foi melhorada e a discriminação entre sinal e ruído aprimorado com métodos de inteligência artificial. Desta forma, essa procura alcançou uma sensibilidade de 5.0 x 10^25 anos para a meia-vida do processo com nível de confiança de 90%, comparável à procura mais sensível do mundo. Esta apresentação cobrirá brevemente o detector EXO-200 e seus principais resultados, além de ressaltar os trabalhos do grupo da Laurentian University envolvido nesse projeto que inclui: a coordenação das análises de dados deste detector e o potencial de sua próxima geração, o detector nEXO que será aproximadamente 25 vezes maior; pesquisa e desenvolvimento para detectação de cargas do nEXO; e investigação de enriquecimento de 136Xe através de destilação criogênica.

    Local: Sala Jayme Tiomno

  • Cosmic Photons from Mass Splitting in the Dark Sector

    Enviado por malcanta em qui, 22/11/2018 - 10:40
    Data: 
    27/11/2018 - 11:00
    Palestrante: 
    Francesco D'Eramo (University of Padova)
    Resumo: 

    In this talk, I will present two dark matter frameworks where a mass splitting in the dark sector dramatically alters the expectations for indirect detection rates. In the first case, the presence of a quasi-degenerate metastable state, where the dark matter number is stored, allows for sub-GeV relics with large s-wave annihilation cross section and not excluded by CMB bounds. In the second case, dark matter particles inelastically up-scatter in the interstellar plasma to a quasi-degenerate heavier partner, whose subsequent decays generate X-ray lines with unique spectrum and morphology.

  • From the Largest Spectroscopic Galaxy Survey to the Lightest Neutrino Mass

    Enviado por malcanta em ter, 06/11/2018 - 13:17
    Data: 
    21/11/2018 - 11:00
    Palestrante: 
    Arthur Loureiro
    Resumo: 

    Since the late 90's we have known that neutrinos oscillate between their three leptonian flavours, which lead to the 2015 Nobel Prize conclusion that these particles are massive. However, particle physics experiments can only tell us about the mass difference between some neutrino species and, consequently, their minimum mass. The neutrino mass hierarchy and the maximum value for the sum of their masses are still unknown. Cosmology, on the other hand, is sensitive to different aspects of neutrino physics since the number of massive neutrino species and the total sum of neutrino masses influence the evolution and formation of structure in the Universe. In this talk, I will present how a spherical harmonic analysis of the Baryon Oscillation Spectroscopic Survey (BOSS) large-scale structure galaxy sample can help set constraints on the sum of neutrino masses, their mass hierarchy and the mass of the lightest neutrino family. When combining the BOSS sample with Cosmic Microwave Background data from the Planck Satellite, Big Bang Nucleosynthesis constraints, and the latest SNe Type Ia data from the Pantheon compilation, we are able to obtain reliable neutrino mass constraints using physically motivated prior models.

     

  • Spontaneous Momentum Dissipation and Coexistence of Phases in Holographic Horndeski Theory

    Enviado por malcanta em seg, 01/10/2018 - 13:33
    Data: 
    10/10/2018 - 11:00
    Palestrante: 
    Prof. Dr. Eleftherios Papantonopoulos
    Resumo: 

    We discuss the possible phases dual to the AdS hairy black holes in Horndeski theory. In the probe limit breaking the translational invariance, we study the conductivity and we find a non-trivial structure indicating a collective excitation of the charge carriers. Going beyond the probe limit, we investigate the spontaneous breaking of translational invariance near the critical temperature and discuss the stability of the theory. We consider the backreaction of the charged scalar field to the metric and we construct numerically the hairy black hole solution. To determine the dual phases of a hairy black hole, we compute the conductivity. When the wave number of the scalar field is zero, the DC conductivity is divergent due to the conservation of translational invariance. For nonzero wave parameter with finite DC conductivity, we find two phases in the dual theory. For low temperatures and for positive couplings, as the temperature is lower, the DC conductivity increases therefore the dual theory is in metal phase, while if the coupling is negative we have the opposite behavior and it is dual to an insulating phase. We argue that this behavior of the coupling of the scalar field to Einstein tensor can be attributed to its role as an impurity parameter in the dual theory.

    *Local: Sala Jayme Tiomno*

  • Harmonic high-order statistics in cosmology

    Enviado por cblanco em qua, 12/09/2018 - 10:59
    Data: 
    21/09/2018 - 11:00
    Palestrante: 
    Dr. Antonino Troja (ICTP-SAIFR)
    Resumo: 
    With the developing of precision cosmology, high-order statistics started to play a key role in the analysis of incoming data. Especially in the case of spherical distributed data, where harmonic statistics help to get tighter constraints on cosmological parameters. My work is focused on bispectrum and trispectrum, showing how it is possible to lift degeneracies and improve the cosmological results.
     
    Local: Sala Jayme Tiomno

  • Primordial Regular Black Holes and Dark Matter

    Enviado por cblanco em sex, 31/08/2018 - 10:58
    Data: 
    05/09/2018 - 11:00
    Palestrante: 
    Prof. Jose A. de Freitas Pacheco (Observatoire de la Côte d'Azur)
    Resumo: 

    Dark matter is an indispensable component to explain the large scale structure of the universe. However, some theoretical expectations are still in contradiction with observations as, for instance, the large number of predicted satellites, the central mass distribution of galaxies, the presence of massive galaxies and clusters at redshift z > 2. Moreover, LHC data do not indicate detection of supersymmetric particles, posing problems to the nature of dark matter. I will discuss an alternative scenario in which dark matter particles are primordial extreme regular black holes formed at the end of inflation, during the reheating era.

    Local: Sala Jayme Tyomno

     

  • Flavourful roads to New Physics

    Enviado por cblanco em seg, 06/08/2018 - 10:53
    Data: 
    27/08/2018 - 11:00
    Palestrante: 
    Dr. Rafael Silva Coutinho (University of Zurich)
    Resumo: 

    The family of decays mediated by b -> sl+l- transitions provide a rich laboratory to search for effects of physics beyond the Standard Model. In recent years LHCb has found hints of deviations from theoretical predictions both in the rates and angular distributions of such processes. In addition, hints of lepton flavour non-universality have been seen when comparing B+ -> K+ mu+mu- and B+ -> K+ e+e- decay rates, with the so-called RK ratio. Similar observables in different decays, such as RK* = BR(B0 -> K*0mu+mu-)/BR(B0->K*0e+e-), have recently become available and indicate the same anomalous pattern. In this talk, an overview of the latest results in this sector and further avenues to test the effectiveness of lepton flavour universality will be presented.

    Local: Sala Jayme Tiomno

  • Matrix Models for Zeta Functions

    Enviado por cblanco em ter, 17/07/2018 - 14:03
    Data: 
    30/07/2018 - 11:00
    Palestrante: 
    Prof. Debashis Ghoshal (School of Physical Sciences, Jawaharlal Nehru University, New Delhi, India)
    Resumo: 

    Riemann hypothesized that the zeta function ζ(s) has (non-trivial) zeroes only on the line Re(s) = 1/2 in the complex s-plane. Hilbert and Polya suggested that the position of these zeroes might be related to the spectrum of a `Hamiltonian'. It has been known for some time that the statistical properties of the eigenvalue distribution of an ensemble of random matrices resemble those of the zeroes of the zeta function. We construct a unitary matrix models (UMM) for the zeta function, however, our approach to the problem is `piecemeal'. That is, we consider each factor in the Euler product representation of the zeta function to get a UMM for each prime. This suggests a Hamiltonian (of the type proposed by Berry and Keating) from its phase space description. We attempt to combine this to get a matrix model for the full zeta function.

    Local: Sala Jayme Tiomno

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