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SUMMARY:Matter effects in long-baseline neutrino experiments
DTSTART;VALUE=DATE-TIME:20261027T162500Z
DTEND;VALUE=DATE-TIME:20261027T163000Z
DTSTAMP;VALUE=DATE-TIME:20261021T040552Z
UID:indico-contribution-6446@cern.ch
DESCRIPTION:Speakers: Elena Semenova (nstitute for Nuclear Research of the
  Russian Academy of Sciences\, MEPHI)\nThe search for CP violation in the 
 lepton sector is one of the central goals of modern neutrino physics\, mot
 ivated by the need to explain the matter–antimatter asymmetry of the Uni
 verse. In long-baseline accelerator experiments\, the interpretation of ne
 utrino and antineutrino appearance signals is complicated by matter effect
 s: coherent forward scattering in the Earth can mimic or modify genuine CP
  violation. We study these effects in the T2K and NOvA experiments within 
 the standard three-flavour oscillation picture\, comparing the vacuum case
  with realistic matter potentials.\nUsing CP-odd ellipses as a visualisati
 on tool\, we scan the unknown CP phase over its full range and plot the co
 rresponding neutrino and antineutrino probabilities. The ellipses are cons
 tructed for different values of the atmospheric mixing angle\, including m
 aximal mixing and both octants\, and for several matter densities.\nThe pa
 rametric degeneracy between the CP phase and the octant of the atmospheric
  mixing angle remains a fundamental challenge. T2K provides a cleaner meas
 urement of CP violation because its matter effect is small\, whereas NOvA 
 is more sensitive to the mass hierarchy because its matter effect is large
 . This complementarity makes a joint analysis essential for separating int
 rinsic CP violation from matter-induced asymmetries.\nThe next generation 
 of long-baseline experiments\, especially DUNE\, will address these challe
 nges directly. With a 1300-kilometre baseline\, higher neutrino energies a
 nd a large liquid-argon detector\, DUNE will experience strong matter effe
 cts and will be able to determine the mass hierarchy and search for CP vio
 lation with high sensitivity. Extending the CP-odd ellipse approach to DUN
 E will help optimise the separation of genuine CP violation from matter ef
 fects and clarify the role of the octant degeneracy. Together with Hyper-K
 amiokande\, DUNE is expected to provide a decisive test of CP violation in
  the lepton sector.\n\nhttps://indico.particle.mephi.ru/event/626/contribu
 tions/6446/
LOCATION:Sevastopol hotel Conference Hall 1
URL:https://indico.particle.mephi.ru/event/626/contributions/6446/
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