Cosmic Particles, Neutrinos, Potentially Reveal Why the Universe Persisted Post-Big Bang
In the vast expanse of the Universe, a profound mystery persists: why is there more matter than antimatter? This question, known as the matter-antimatter asymmetry problem, has puzzled scientists for decades. One promising solution may lie in the realm of neutrino oscillations, a phenomenon that could help explain the imbalance between matter and antimatter in the early Universe.
The matter-antimatter asymmetry, or baryon asymmetry, requires physics beyond the Standard Model to generate an excess of matter over antimatter. One such mechanism involves leptogenesis, where an initial lepton asymmetry is created and then converted into baryon asymmetry through electroweak processes.
Neutrino oscillations, especially those involving sterile neutrinos and the interplay of different neutrino flavors, play a crucial role in this process. Oscillations between active neutrinos and sterile neutrinos in the early Universe can create flavor-dependent lepton asymmetries, even if the total lepton number is initially small or zero.
These flavor asymmetries can survive until temperatures around a few MeV, when neutrino oscillations become effective, mixing the neutrino flavors and possibly relaxing total lepton asymmetry. However, they allow sizable flavor asymmetries to remain, which influence the production of sterile neutrinos and the eventual baryon asymmetry through the right-handed neutrino portal and associated decay/thermal processes.
The conversion of the lepton asymmetry into baryon asymmetry occurs via sphaleron processes that violate baryon and lepton number conservation but preserve B-L (baryon minus lepton number). Neutrino oscillations are thus essential in modulating the lepton asymmetries available for these processes in the primordial plasma.
Models involving neutrino oscillation-induced leptogenesis can explain the observed baryon number asymmetry over a wide parameter range, linking the microscopic neutrino properties (mass, mixing angles, CP violation phases) to cosmological observations.
The Deep Underground Neutrino Experiment (DUNE), a future international flagship experiment at Fermilab, is dedicated to shedding light on this intriguing mystery. Dr. Elena Gramellini, a Lederman Fellow at Fermilab, is developing a Liquid Argon Time Projection Chamber (LArTPC) for DUNE. Real neutrino interactions will be recorded using medium-scale prototypes, and the new sensors of the LArTPC are being characterized for performance.
DUNE has the potential to see neutrinos from the Sun and supernovae, and it may efficiently recognize proton decay events, an observation long coveted but never observed. Dr. Gramellini can be followed on Twitter via the handle @SweatPantsScien for updates on her research and DUNE's progress.
Neutrinos, one of the elementary building blocks of our Universe, could help answer the matter-antimatter asymmetry problem by contributing to the violation of the symmetry between matter and antimatter. The LArTPC with a powerful light-collection system is expected to enhance understanding at low energies, providing valuable insights into this captivating cosmic conundrum.
- In the exploration of the matter-antimatter asymmetry problem, science and technology are instrumental in developing experiments like the Deep Underground Neutrino Experiment (DUNE), experimenting with neutrinos, especially their oscillations, to potentially uncover the origin of more matter than antimatter in the universe.
- The solution to the matter-antimatter asymmetry problem may be linked to the intriguing world of neutrino oscillations, as these phenomena, especially in the context of sterile neutrinos and leptogenesis, could create flavor-dependent lepton asymmetries that influence the production of baryon asymmetry in the early universe, thereby explaining the observed baryon number asymmetry over a wide parameter range.
