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Events on Friday, October 28th, 2022

NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Powerful Indirect Constraints on the Origins of Ultra High Energy Cosmic Rays
Time: 2:00 pm
Place: CH 4274
Speaker: Glennys Farrar, NYU
Abstract: As is now painfully evident, finding the sources of UHECRs is very challenging due to the combination of most UHECRs having intermediate masses, the poor precision in individual UHECR charge assignments, and generally large deflections in the imperfectly-known Galactic magnetic field. These effects not only smear the images of individual UHECR sources but also lead to a non-trivial and poorly-constrained mapping between a source's direction and the arrival direction distribution of its UHECRs. In the face of this challenge, indirect information on the sources which is imprinted on the spectrum and composition of UHECRs as they emerge from the source surroundings and on the neutrinos they produce, provides valuable additional information on the nature of the sources. This talk will discuss the resulting constraints on the physical properties of the environment surrounding the source, and a possible picture that emerges when also considering evidence on the number density and diversity of source types.
Host: Lu Lu
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Physics Department Colloquium
The seemingly-anomalous magnetic moment of the muon - a novel reconciliation with the Standard Model and connection with Dark Matter
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Glennys Farrar, NYU
Abstract: Precision measurement of the magnetic moment of the muon yields a result 4.2 sigma above the prediction of the Standard Model. At the same time, the lattice QCD calculation of the “hadronic vacuum polarization” — essentially, a weighted integral of the cross section for e+e- -> hadrons — disagrees with the direct experimental measurement at a similar level. I will propose that both discrepancies can be explained, quite naturally, by production of unseen final states in e+e- -> hadrons. Such so-far-undiscovered hadrons have to be neutral and long-lived to have escaped detection, and in fact could be the Dark Matter particle. I will discuss tests of this proposal.
Host: Lu Lu
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