Theory Seminars WS 21/22

Thu 14.10.2021, 16.30 h

Rebecca Diesing (U Chicago)

A Revised Theory of Cosmic Ray Acceleration: Solving the Problem of Steep Spectra

Abstract:
Galactic cosmic rays (CRs) are accelerated at the forward shocks of supernova remnants (SNRs) via diffusive shock acceleration (DSA), an efficient acceleration mechanism that predicts power-law energy distributions of CRs. However, observations of nonthermal SNR emission imply CR energy distributions that are generally steeper than E−2, the standard DSA prediction. Recent results from kinetic hybrid simulations suggest that such steep spectra may arise from the drift of magnetic structures with respect to the thermal plasma behind the shock. I will discuss how, using a semi-analytic model of non-linear DSA, we can apply this new theory to a wide range of SNRs and other astrophysical shocks. I will further show how, by accounting for the motion of magnetic structures behind the shock, we produce CR energy distributions that are substantially steeper than E−2 and consistent with observations.

Host: P. Mertsch

 

Thu 21.10.2021, 16.30 h

Andrea Shindler (Michigan)

Unravelling matter-antimatter asymmetry in the universe

Abstract:
The observed baryon asymmetry in the universe cannot be reconciled with the current form of the Standard Model (SM) of particle physics. The amount of CP-violation stemming from the Cabibbo-Kobayashi-Maskawa matrix is not sufficient to explain the observed matter-antimatter asymmetry. Historically, one of the first systems to be studied in the search for CP-violation is the electric dipole moment (EDM) of the neutron. The contribution to the neutron EDM coming from the SM is several order of magnitudes smaller than the current experimental bound, thus providing a unique background-free window for potential discovery of physics Beyond the Standard Model (BSM). Beside all the CP-violating effective operators describing the contributions from BSM, the neutron EDM can potentially be induced by the strong CP-violating theta term.
After a brief introduction on baryon asymmetry and a summary of the current status for experimental searches of a neutron EDM, I describe the different CP-violating sources and the challenges that present a calculation of the corresponding hadronic matrix elements. I then proceed detailing recent results obtained, with my collaborators, on the neutron EDM with a specific focus on the the main theoretical and numerical tool used: the gradient flow. I conclude with near-term goals, challenges and an optimistic view into the future.

Host: R. Harlander

 

Thu 28.10.2021, 16.30 h

Andrea Caputo (Weizmann)

TBA

Host: F. Kahlhoefer

 

Thu 11.11.2021, 16.30 h

Cora Uhlemann (Newcastle U)

TBA

Host: J. Lesgourgues

 

Thu 18.11.2021, 16.30 h

Valentin V. Khoze  (Durham U.)

Searching for QCD Instantons at Hadron Colliders

Host: M. Worek

 

Thu 25.11.2021, 16.30 h

Oleg Lebedev (U Helsinki)

TBA

Host: F. Kahlhoefer

 

Thu 02.12.2021, 9.00 Uhr !!!

Tom Melia (Tokyo U, IPMU)

TBA

Host: R. Harlander

 

Thu 09.12.2021, 16.30 h

Lavinia Heisenberg (ETH Zürich)

TBA

Host: J. Lesgourgues

 

Thu 13.01.2022, 16.30 h

Juan Garcia-Bellido (Universidad Autónoma de Madrid)

TBA

Host: J. Lesgourgues

 

Thu 20.01.2022, 16.30 h

Javier Mazzitelli (MPI Munich)

Next-to-next-to-leading order event generation for top-quark pair production

Host: M. Worek

 

Thu 27.01.2022, 16.30 h

Alexandre Marcowith (U Montpellier)

TBA

Host: P. Mertsch

 

Thu 03.02.2022, 16.30 h

Maximilian Stahlhofen (U. Freiburg)

TBA

Host: M. Czakon