Periodic Reporting for period 1 - NEUTON (NEUTrino OscillatioN analysis at T2K and SuperKamiokande experiments: Can neutrinos explain the matter-antimatter asymmetry in the Universe?)
Berichtszeitraum: 2019-09-01 bis 2021-08-31
The NEUTON project is aimed at getting a better knowledge of the neutrino oscillation phenomena in long-baseline neutrino oscillation facilities. The success of these studies and experiments is of paramount relevance for the understanding of the evolution of the Universe among other open questions in Science.
'Why the Universe is primarily comprised of matter today, instead of equal parts of matter and antimatter', is one of the most intriguing questions in all of science. In spite of its tremendous success, the Standard Model (SM) of elementary particles does not fully answer several fundamental questions, which require to be investigated with various complementary approaches and using different “messenger” particles, such as the elusive neutrinos. In particular, the SM assumes charge-parity (CP) symmetry which involves that production and decay rates of particles and antiparticles should be almost equivalent; but such situation would have led to an empty cosmos shortly after the Big Bang. So, what CP-violating (CPV) process beyond the SM favoured the production of matter over antimatter? The answer could lie in the recent discovery of neutrino oscillations, which has glimpsed the possibility that neutrinos and antineutrinos behave differently, opening the door to new physics beyond the SM. This has motivated several experiments (FermiLab [USA]: NOvA, MINERvA, DUNE; Japan: T2K and SuperKamiokande (SK)) aimed at determining neutrino oscillation parameters and CPV as well as other open questions in Physics such as dark matter search through sterile neutrinos, proton decay or supernovae analysis.
Nevertheless, the success of current and forthcoming neutrino oscillation experiments largely depends on an accurate description of neutrino interactions. In particular, the determination of neutrino-nucleus cross sections is one of the leading experimental uncertainties. The current precision on the modelling of these cross-section at the level of 10% are by far too large for the precision expected by the next generation of experiments (< 5%). In this sense, the neutrino interaction models developed by the University of Seville group would help to improve this analysis as they have widely proven their capability to describe neutrino cross-section data in a broad energy range, being a promising candidate to be implemented in the T2K and SuperKamiokande neutrino event generators. This would improve the experimental systematics needed to answer the above mentioned open questions in Physics as well as to shorten the required running time and experimental costs of current and next-generation neutrino experiments (DUNE and HyperKamiokande).
'Why the Universe is primarily comprised of matter today, instead of equal parts of matter and antimatter', is one of the most intriguing questions in all of science. In spite of its tremendous success, the Standard Model (SM) of elementary particles does not fully answer several fundamental questions, which require to be investigated with various complementary approaches and using different “messenger” particles, such as the elusive neutrinos. In particular, the SM assumes charge-parity (CP) symmetry which involves that production and decay rates of particles and antiparticles should be almost equivalent; but such situation would have led to an empty cosmos shortly after the Big Bang. So, what CP-violating (CPV) process beyond the SM favoured the production of matter over antimatter? The answer could lie in the recent discovery of neutrino oscillations, which has glimpsed the possibility that neutrinos and antineutrinos behave differently, opening the door to new physics beyond the SM. This has motivated several experiments (FermiLab [USA]: NOvA, MINERvA, DUNE; Japan: T2K and SuperKamiokande (SK)) aimed at determining neutrino oscillation parameters and CPV as well as other open questions in Physics such as dark matter search through sterile neutrinos, proton decay or supernovae analysis.
Nevertheless, the success of current and forthcoming neutrino oscillation experiments largely depends on an accurate description of neutrino interactions. In particular, the determination of neutrino-nucleus cross sections is one of the leading experimental uncertainties. The current precision on the modelling of these cross-section at the level of 10% are by far too large for the precision expected by the next generation of experiments (< 5%). In this sense, the neutrino interaction models developed by the University of Seville group would help to improve this analysis as they have widely proven their capability to describe neutrino cross-section data in a broad energy range, being a promising candidate to be implemented in the T2K and SuperKamiokande neutrino event generators. This would improve the experimental systematics needed to answer the above mentioned open questions in Physics as well as to shorten the required running time and experimental costs of current and next-generation neutrino experiments (DUNE and HyperKamiokande).
Following the main research objectives mentioned in the previous section, the work performed during the first part of the project has addressed the following topics:
- Within the framework of relativistic mean field (RMF) and superscaling (SuSAv2) models, several calculations at kinematics of interest for the T2K and SuperKamiokande experiments have been performed with the aim of analyzing low-energy nuclear effects. Unlike other theoretical approaches, we have found important differences between carbon and oxygen at these kinematics which are in accordance with some recent and preliminary experimental measurements.
- The RMF and SuSAv2 codes has been adapted and optimized to implement them in the NEUT event generator. After the full implementation, the RMF and SuSAv2 models will be used directly for the oscillation analysis and the determination of oscillation parameters.
This part of the project has been carried out in collaboration with T2K and SuperKamiokande members: S. Dolan, R. Wendell, Y. Hayato, L. Pickering and others; and also with researchers from the University of Seville, Turin, Granada and Complutense of Madrid. Guillermo D. Megias has got involved in regular bi-weekly meetings with different T2K working groups: NIWG (Neutrino Interaction Working Group) and XSEC WG (Cross Section Working Group), where different details of the project have been regularly discussed.
Guillermo D. Megias has also taken shifts on the T2K and SuperKamiokande facilities. These shifts are focused on real-time diagnosis and basic trouble-shooting of the beam operation, data acquisition or detector activity. Guillermo D. Megias has also supervised and trained other new members of the collaboration.
A collaboration has been established with the NINJA group, a Japanese collaboration aimed to measure neutrino-water interactions containing low-momentum secondary particles using a nuclear emulsion detector. Some results using the SuSAv2 and RMF models have been provided to NINJA for their analyses. Another collaboration with MIT and FermiLab members (USA) has been started to implement our models in their generators and to analyze electron scattering data which provide essential information for neutrino oscillation experiments. This collaboration has led to a publication in Nature (in press, 2021).
This phase of the project has led to more than 10 publications (Nature, Physical Review D, The Astrophysical Journal, PTEP, etc.) and several contributions to international conferences and workshops (NEUTRINO2020, NuFact21, European Researcher’s Night 2020, etc.).
- Within the framework of relativistic mean field (RMF) and superscaling (SuSAv2) models, several calculations at kinematics of interest for the T2K and SuperKamiokande experiments have been performed with the aim of analyzing low-energy nuclear effects. Unlike other theoretical approaches, we have found important differences between carbon and oxygen at these kinematics which are in accordance with some recent and preliminary experimental measurements.
- The RMF and SuSAv2 codes has been adapted and optimized to implement them in the NEUT event generator. After the full implementation, the RMF and SuSAv2 models will be used directly for the oscillation analysis and the determination of oscillation parameters.
This part of the project has been carried out in collaboration with T2K and SuperKamiokande members: S. Dolan, R. Wendell, Y. Hayato, L. Pickering and others; and also with researchers from the University of Seville, Turin, Granada and Complutense of Madrid. Guillermo D. Megias has got involved in regular bi-weekly meetings with different T2K working groups: NIWG (Neutrino Interaction Working Group) and XSEC WG (Cross Section Working Group), where different details of the project have been regularly discussed.
Guillermo D. Megias has also taken shifts on the T2K and SuperKamiokande facilities. These shifts are focused on real-time diagnosis and basic trouble-shooting of the beam operation, data acquisition or detector activity. Guillermo D. Megias has also supervised and trained other new members of the collaboration.
A collaboration has been established with the NINJA group, a Japanese collaboration aimed to measure neutrino-water interactions containing low-momentum secondary particles using a nuclear emulsion detector. Some results using the SuSAv2 and RMF models have been provided to NINJA for their analyses. Another collaboration with MIT and FermiLab members (USA) has been started to implement our models in their generators and to analyze electron scattering data which provide essential information for neutrino oscillation experiments. This collaboration has led to a publication in Nature (in press, 2021).
This phase of the project has led to more than 10 publications (Nature, Physical Review D, The Astrophysical Journal, PTEP, etc.) and several contributions to international conferences and workshops (NEUTRINO2020, NuFact21, European Researcher’s Night 2020, etc.).
As previously mentioned, the success of this project in connection with the developments of current and forthcoming neutrino oscillation experiments largely depends on an accurate description of neutrino-nucleus interactions. In 2021-2022, an important part of this project will be addressed. The full implementation of our models in the experimental event generators is expected to improve this analysis due to their accuracy on describing neutrino data. An innovative semi-inclusive reaction model will be developed to reduce nuclear-medium uncertainties by improving hadron detection efficiency. The combined impact of all these are expected to increase largely event-selection efficiency in T2K and SK while reducing interaction systematics by 2%. The research carried out in this project will be also relevant for the next-generation of neutrino oscillation experiments, DUNE (USA) and HyperKamiokande (Japan), where a complete determination of the CP symmetry violation and the neutrino-antineutrino oscillation differences is expected. This could lead to explain the matter-antimatter imbalance in the universe.
The success of this project will also foster novel model-implementation techniques in neutrino generators with unprecedented reduction in computational time and straightforward extension to several nuclear targets.
At the same time, the collaboration with some researchers from MIT and FermiLab (e4nu and CLAS collaborations) will continue in the following years for the analysis of electron-nucleus reactions of interest for current and future oscillation experiments. This collaboration has led to a publication in Nature (2021) and an interview in the Spanish national newspaper El País.
The development of sophisticated neutrino interaction models within this project is expected to improve the above-mentioned experimental uncertainties as well as to shorten the required running time and experimental costs of current and next-generation neutrino oscillation experiments (DUNE and HyperKamiokande). The potential impact of all these outcomes in the society in general are mostly related to the general scientific knowledge about the origin of the universe and the Big Bang.
The success of this project will also foster novel model-implementation techniques in neutrino generators with unprecedented reduction in computational time and straightforward extension to several nuclear targets.
At the same time, the collaboration with some researchers from MIT and FermiLab (e4nu and CLAS collaborations) will continue in the following years for the analysis of electron-nucleus reactions of interest for current and future oscillation experiments. This collaboration has led to a publication in Nature (2021) and an interview in the Spanish national newspaper El País.
The development of sophisticated neutrino interaction models within this project is expected to improve the above-mentioned experimental uncertainties as well as to shorten the required running time and experimental costs of current and next-generation neutrino oscillation experiments (DUNE and HyperKamiokande). The potential impact of all these outcomes in the society in general are mostly related to the general scientific knowledge about the origin of the universe and the Big Bang.