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VERSION:2.0
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PRODID:UW-Madison-Physics-Events
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SEQUENCE:1
UID:UW-Physics-Event-9849
DTSTART:20261005T163000Z
DTEND:20261005T180000Z
DTSTAMP:20261008T012201Z
LAST-MODIFIED:20261001T164327Z
LOCATION:Chamberlin 5280
SUMMARY:Probing Cosmic Neutrinos & Free-Streaming Radiation with the C
 osmic Microwave Background\, Theory Seminar (High Energy/Cosmology)\, 
 Gab Montefalcone\, University of Wisconsin-Madison
DESCRIPTION:The cosmic microwave background (CMB) provides a unique wi
 ndow onto fundamental physics\, allowing us to study particles and int
 eractions that are otherwise extremely difficult to probe in laborator
 y experiments. One important example is the cosmic neutrino background
 \, which influences the evolution of the early Universe\, primarily th
 rough gravity despite interacting only very weakly with ordinary matte
 r.
\nIn this talk\, I will discuss how the free-streaming nature of ne
 utrinos is expected to leave a subtle but distinctive imprint on the C
 MB by inducing a phase-shift in the acoustic oscillations of the photo
 n–baryon plasma prior to recombination\, providing a clean and robus
 t probe of neutrino physics. I will present a framework to extract thi
 s effect directly from CMB observations\, and show that current data f
 rom Planck\, ACT\, and SPT detect it with high significance\, consiste
 nt with the Standard Model prediction of three free-streaming neutrino
  species.
\nI will then discuss how the same measurement can be used t
 o test beyond standard model scenarios in which neutrinos interact mor
 e strongly\, delaying their decoupling from the primordial plasma. By 
 directly relating the observed phase shift to neutrino interactions\, 
 cosmological data can place competitive constraints on new neutrino ph
 ysics using this single\, well-understood observable and without the n
 eed for dedicated model-dependent analyses.
URL:https://www.physics.wisc.edu/events/?id=9849
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