Seminars

  • Tuesday 28 January 2020 at 10.15 in A315: Sampsa Vihonen (Guangzhou)
    China and the quest for the lepton flavour
    Abstract:
    In recent years, China has invested heavily in its particle physics programs. Whereas the last decade belonged to the reactor neutrino experiments and the precision measurement of the mixing angle theta_{13}, the near future will entail efforts to search for CP violation in the leptonic sector and look for signatures of new physics in form of lepton flavour violation. In the future, we will hopefully see the last pieces fall in place in the lepton flavour puzzle. In this talk, I will briefly review the Chinese efforts in these questions and discuss their position in the global picture.
  • Tuesday 11 February 2020 at 10.15 in A315: Chris Rosen (Imperial College, London)
    Supersymmetric deformations and spatially modulated masses
    Abstract:
    Deforming fixed point theories by couplings to operators which explicitly break Poincare invariance can provide an interesting perspective on the scale dependent properties of interacting gauge theories. These properties are encoded in the action of the Renormalisation Group, and many of them can be realised geometrically via applications of gauge/gravity duality. We appeal to this holographic perspective to construct infinite classes of spatially modulated deformations of the ABJM theory which break Poincare invariance but nonetheless preserve some supersymmetry. The resulting flows offer explicit field theory examples of novel RG trajectories, such as RG “boomerang flows”, whose phenomenology we also discuss.
  • Thursday 13 February 2020 at 10.15 in A315: Carlo Heissenberg (Nordita)
    On electromagnetic and color memory in even dimensions
    Abstract:
    Asymptotic symmetries at null infinity do not seem to play a fundamental role in higher dimensions: in D>4 one can describe radiative solutions to Maxwell’s and Einstein’s equations and memory effects without the need to enhance the standard global symmetry group. However, this fact seems at odds with the connection asymptotic symmetries and memory effects share with soft theorems, whose validity extends beyond D=4.
    We investigate this issue studying Maxwell and Yang–Mills memory effects near null infinity in arbitrary even D. Together with classical memories, linear and non-linear, given by kicks in the velocity of probe particles, we also discuss quantum memory effects in the form of phase rotations in the configuration of several probes.
    Adopting the Lorenz gauge, we interpret such memory effects as the action of suitable residual symmetries acting near null infinity and propose a strategy for defining infinite–dimensional asymptotic symmetries of Maxwell’s theory in any D.
  • Tuesday 18 February 2020 at 10.15 in A315: Diana Rojas-Ciofalo (Southampton)
    Dark CP-Violation in the Three Higgs Doublet Model
    Abstract:
    We study an extension of the Standard Model (SM) in which two copies of the SM Higgs doublet are added to the scalar sector. These extra doublets do not develop a vacuum expectation value, hence, they are inert. This essentially leads to a 3-Higgs Doublet Model (3HDM) with 2 inert and 1 active scalar doublets, which we denote as I(2+1)HDM. We allow for CP-violation in the inert sector, where the lightest inert state is protected from decaying to SM particles through the conservation of a Z2 symmetry so that it is a Dark Matter (DM) candidate. Such a source of CP-violation from the inert sector do not contribute to the Electric Dipole Moments and are therefore unconstrained. In this talk, it will be discussed which new phenomenology arises in a model that includes such a CP-violating phase. We will explore how this CPV source relaxes some region of parameter space that are excluded in the CPC case due to the relic density measure or direct and indirect experiments. We will also show collider phenomenology that is related to the presence of this CPV phase.
  • Tuesday 25 February 2020 at 10.15 in A315: Alexander Krikun (Nordita)
    TBA
    Abstract: TBA
  • Tuesday 25 February 2020 at 14.15 in D114: Arnaud Ferrari (Uppsala) Note time and place!
    Higgs boson pair production at the LHC: experimental overview
    Abstract: Searches for the simultaneous production of two Higgs bosons (HH) in proton-proton collisions are an important part of the LHC experimental program, as they allow to probe the shape of the Higgs potential in (and beyond) the Standard Model. HH pairs can also be produced in the decay of new resonances. This seminar will give an overview of the searches for HH pairs in ATLAS and CMS with 13 TeV, as well as their statistical combinations, with a focus on the non-resonant production mode. Prospects at the future LHC runs will also be discussed.
  • Thursday 27 February 2020 at 10.15 in A315: LISA day
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    Abstract: TBA
  • Tuesday 3 March 2020 at 10.15 in A315: Carlos Hoyos (Oviedo)
    TBA
    Abstract: TBA
  • Tuesday 10 March 2020 at 10.15 in A315: Maurizio Piai (Swansea)
    TBA
    Abstract: TBA
  • Tuesday 28 April 2020 at 10.15 in A315: Chris Herzog (Kings College, London)
    TBA
    Abstract: TBA
  • Tuesday 5 May 2020 at 10.15 in A315: Rebeca Gonzalez Suarez (Uppsala)
    TBA
    Abstract: TBA
  • Tuesday 26 May 2020 at 10.15 in A315: Murray Moinester (Tel Aviv)
    Pion Polarizabilities
    Abstract: The electric απ and magnetic βπ charged pion polarizabilities characterize the induced dipole moments of the pion during γπ Compton scattering. Pion polarizabilities affect the shape of the γπ Compton scattering angular distribution. By crossing symmetry, the γπ→γπ amplitudes are related to the γγ→ππ amplitudes. Dispersion relations (DR) describe how charged pion polarizabilities contribute to both γγ → π+π- and γγ → π0π0 reactions. A stringent test of chiral perturbation theory (ChPT) is possible by comparing the experimental polarizabilities with ChPT predictions. The combination (απ-βπ) has been measured by: (1) radiative pion Primakoff scattering πZ → πZγ at CERN COMPASS, (2) two-photon pion pair production γγ→ππ at SLAC PEP Mark-II, (3) radiative pion photoproduction γp→ γπn at Mainz MAMI. COMPASS and Mark-II (but not Mainz) polarizabilities are in good agreement with ChPT predictions; and by DRs, with DESY Crystal Ball γγ → π0π0 data. A pion polarizability status report is presented, following the review by S. Scherer and M. Moinester for IJMPA.
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      Hopefully the up to 50 min + 10 min discussion long seminar/colloquium will be understandable to a wide audience.
      Contacts: Keijo Kajantie (keijo kajantie at helsinki fi) [ HIP seminar],
      Sofie Koksbang (sofie koksbang at helsinki fi) [cosmo seminar]

      For older seminars, click Seminar Archive on top of page

      Other related seminars

      Friday 10-12 seminar series in A315:Astrophysics seminar.
      Mathematical Physics Seminar and Workshop series Wed 14-16 in Exactum C123.