DEPARTMENT OF PHYSICS / HIP JOINT COLLOQUIA / SEMINARS 2026

    • Tuesday 24 March 2026 at 10:15 in A315 and using Zoom: Lotta Jokiniemi (Darmstadt)
      Ab initio studies on muon capture and rare decays
      Abstract:       Neutrinoless double-beta (0νββ) decay is a hypothetical nuclear decay in which two nucleons inside the nucleus beta-decay simultaneously emitting only two beta-particles without the associated (anti-)neutrinos. The process violates lepton-number conservation and requires that neutrinos are their own antiparticles (or Majorana particles), and observation of the decay would hence have implications in the understanding of the matter-antimatter asymmetry of the Universe. Furthermore, 0νββ decay is an excellent probe of the absolute neutrino mass scale, as the decay rate can be related to the effective neutrino mass. While experiments hunting for this decay are approaching ton scales, the required nuclear-theory input remains a major obstacle to planning and interpreting the experiments.
      I will start by discussing recent advances in the ab initio theory predictions for neutrinoless double-beta decay. These systematically improvable calculations are based on nuclear interactions and currents derived from chiral effective field theory, allowing for uncertainty quantification. I will show how the new theory predictions affect the interpretation of current and future experiments. Then, I will talk about /ab initio/ studies on muon capture in light nuclei. Thanks to the high momentum transfer involved in the process, it can be used to probe the weak currents at the momentum regime relevant for the 0νββ decay. The computed rates are found to be in good agreement with available experimental counterparts, motivating future experimental and theoretical explorations.
    • Thursday 26 March 2026 at 10:15 in A315 and using Zoom: Greg Jackson (Nantes)
      Stochastic collisional energy loss of a heavy quark crossing a finite-size QGP
      Abstract:       An energetic parton crossing a hot or dense quark-gluon plasma (QGP) can lose energy through elastic collisions with the medium, a process contributing to jet and hadron suppression observed in heavy-ion, and recently also in light-ion collisions. Going beyond existing approaches, which mostly focus on the average energy loss per unit distance for large systems, we derive the full energy loss probability distribution (or quenching weight) from first principles using Landau’s kinetic equation to resum the energy losses suffered in multiple successive elastic scatterings. The distribution captures large event-by-event fluctuations, arising from the long tail of the single scattering spectrum, and includes the possibility of energy gain from the medium, both effects being especially relevant for small systems. Our results fill a conceptual gap in the modelling of jet/hadron and heavy flavour suppression, where usually only those fluctuations of the radiative energy loss are taken into account, and may help interpreting high-multiplicity pp and pA data.
    • Thursday 2 April 2026 at 9:30 in A315 and using Zoom: Stephan Rosswog (Hamburg)   Note unusual time!
      TBA
      Abstract:       TBA
    • Tuesday 21 April 2026 at 10:15 in A315 and using Zoom:  Antonino Salvino Midiri (University of Geneva) Onsite Cosmo Seminar
      TBA
      Abstract:       TBA
    • Thursday 21 May 2026 at 10:15 in A315 and using Zoom: Michal Heller (Ghent)
      TBA
      Abstract:       TBA
    • Tuesday 11 August 2026 at 10:15 in A315 and using Zoom: Christophe Royon (CMS)
      TBA
      Abstract:       TBA

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],
Tushar Gupta  (tushar.gupta at helsinki fi) [cosmo seminar]

Other related seminars

Friday 10-12 seminar series in D114:Astrophysics seminar
Mathematical Physics Seminar and Workshop series Wed 14-16 in Exactum C123.
InstituteQ Events and Seminars