New results deal a blow to the theoretical sterile neutrino

sc604 — Fri, 29 Oct 2021 08:58:21 +0000

̽��ֱ��results were gathered by an international team at the MicroBooNE experiment in the United States, with leadership from a UK team including researchers from the ̽��ֱ�� of Cambridge.

̽��ֱ��two most likely explanations for anomalies that were seen in two previous physics experiments: one which suggests a sterile neutrino, and one which points at limitations in those experiments, have been ruled out by MicroBooNE.

̽��ֱ��fourth neutrino

For more than two decades, this proposed fourth neutrino has remained a promising explanation for anomalies seen in earlier physics experiments. In these previous experiments, neutrinos were observed acting in a way not explained by the Standard Model of Physics – the leading theory to explain the building blocks of the universe and everything in it.

Neutrinos are the most abundant particle with mass in our universe, but they rarely interact with other matter, making them hard to study. But these elusive particles seem to hold answers to some of the biggest questions in physics – such as why the universe is made up of more matter than antimatter.

A 170-ton neutrino detector the size of a bus was created to study these particles – and became known as MicroBooNE. ̽��ֱ��international experiment has close to 200 collaborators from 36 institutions in five countries, and is supported by the Science and Technology Facilities Council (STFC) in the UK.

Standard Model holds up

̽��ֱ��team used cutting-edge technology to record precise 3D images of neutrino events and examine particle interactions in detail. Four complementary analyses released by the international MicroBooNE collaboration, at the Fermi National Accelerator Laboratory (Fermilab), deal a blow to the fourth neutrino hypothesis.

All four analyses show no sign of the sterile neutrino, and instead the results align with the Standard Model. ̽��ֱ��data is consistent with what the Standard Model predicts: three kinds of neutrinos only. But the anomalies are real and still need to be explained. Crucially, MicroBooNE has also ruled out the most likely explanation to explain these anomalies without requiring new physics.

These results mark a turning point in neutrino research. With the evidence for sterile neutrinos becoming weaker, scientists are investigating other possibilities for anomalies in perceived neutrino behaviour.

“This result is incredibly exciting as it suggests something far more interesting than we expected is happening – it’s now our goal to find out what this could be,” said Dr Melissa Uchida, who leads the Neutrino Group at Cambridge’s Cavendish Laboratory.

“This heralds the start of a new era of precision for neutrino physics, in which we will deepen our understanding of how the neutrino interacts, how it impacted the evolution of the universe, and what it can reveal to us about physics beyond our current Standard Model of how the universe behaves at the most fundamental level,” said Professor Justin Evans from the ̽��ֱ�� of Manchester, co-spokesperson of the experiment.

“Cambridge has played an integral part in this experiment both through the software — the reconstruction algorithms that allow us to distinguish particles and their interactions in MicroBooNE and through the analysis itself,” said Uchida. “With half the data still to analyse and more exotic avenues to pursue, there is an exciting journey ahead.”

̽��ֱ��UK at MicroBooNE

̽��ֱ��UK has taken a leading role in MicroBooNE, leading the development of state-of-the-art pattern recognition algorithms, making world-leading contributions to the understanding of neutrino interactions in the argon, and bringing a broad range of expertise to these searches for the elusive sterile neutrinos.

UK universities involved in MicroBooNE are Manchester, Edinburgh, Cambridge, Lancaster, Warwick and Oxford.

Mission to understand neutrinos

With our understanding of neutrinos still incomplete, the UK through STFC has invested in a science programme to address these key science questions, as well as invest in new technologies.

̽��ֱ��UK government has already invested £79 million in the Deep Underground Neutrino Experiment, Long-Baseline Neutrino Facility (LBNF), and the new PIP-II accelerator, all hosted by Fermilab.

This investment has given UK scientists and engineers the chance to take leading roles in the management and development of the DUNE far detector, the LBNF neutrino beam targetry and PIP-II accelerator.

Professor Mark Thomson, Executive Chair of STFC and one of the first UK physicists to join MicroBooNE, said: “This much-awaited result is a significant step our understanding of neutrinos. This extremely challenging measurement is also important in that the MicroBooNE experiment used a new technology to record detailed images of individual neutrino interactions.

“ ̽��ֱ��successful use the liquid argon imaging technology is a major stepping stone towards DUNE.

“Once complete by the end of this decade, DUNE will use several detectors each of the size of an extra-deep Olympic swimming pool, but with liquid argon replacing the water, to measure the movements and behaviours of neutrinos.”

Adapted from an STFC press release.

Results from a global science experiment have cast doubt on the existence of a theoretical particle beyond the Standard Model.

Cindy Arnold, Fermilab

Teams prepare to move the MicroBooNE cryostat from DZero to the Liquid Argon Test Facility (LArTF), USA.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

UK researchers awarded £30m for global science project to better understand matter and antimatter

sc604 — Tue, 10 Dec 2019 06:33:43 +0000

̽��ֱ�� ̽��ֱ�� of Cambridge will provide essential contributions to the DUNE experiment, a global science project that brings the scientific community together to work on trying to answer some of the biggest questions in physics.

DUNE (the Deep Underground Neutrino Experiment) is hosted by the United States Department of Energy’s Fermilab, and will be designed and operated by a collaboration of over 1,000 physicists from 32 countries.

̽��ֱ��project aims to advance our understanding of the origin and structure of the universe. It will study the behaviour of particles called neutrinos and their antimatter counterparts, antineutrinos. This could provide insight as to why we live in a matter-dominated universe while anti-matter has largely disappeared.

“DUNE has the unique potential to answer fundamental questions that overlap particle physics, astrophysics, and cosmology,” said Professor Stefan Söldner-Rembold of the ̽��ֱ�� of Manchester, who leads the international DUNE collaboration as one of its spokespeople.

̽��ֱ��investment, from UK Research and Innovation’s Science and Technology Facilities Council (STFC), is a four-year construction grant to 13 educational institutions, and to STFC’s Rutherford Appleton and Daresbury Laboratories. This grant, of £30m, represents the first of two stages to support the DUNE construction project in the UK which will run until 2026 and represent a total investment of £45m.

Various elements of the experiment are under construction across the world, with the UK taking a major role in contributing essential expertise and components to the experiment and facility. UK scientists and engineers will design and produce the principle detector components at the core of the DUNE detector, which will comprise four large tanks each containing 17,000 kg of liquid argon.

̽��ֱ��UK groups are also developing a high-speed data acquisition system to record the signals from the detector, together with the sophisticated software needed to interpret the data and provide the answers to the scientific questions.

“DUNE could help to change the way we understand the universe,” said Dr Melissa Uchida, who leads the neutrino group at Cambridge’s Cavendish Laboratory. “This announcement has allowed the UK to take a leading role in many aspects of the experiment, making the UK the biggest DUNE contributor outside the USA. Our group will deliver hardware and software, as well as calibration and analysis effort for DUNE and we are ready and excited to meet the challenges ahead.”

DUNE will also watch for supernova neutrinos produced when a star explodes, which will allow the scientists to observe the formation of neutron stars and black holes and will investigate whether protons live forever or eventually decay, bringing us closer to fulfilling Einstein’s dream of a grand unified theory.

̽��ֱ��other UK universities involved in the project are Birmingham, Bristol, Edinburgh, Imperial College London, Lancaster, Liverpool, Manchester, Oxford, Sheffield, Sussex, UCL and Warwick.

Cambridge researchers will receive funding as part of a £30m investment in the DUNE experiment, which has the potential to lead to profound changes in our understanding of the universe.

CERN

Inside ProtoDUNE at CERN

Yes

̽��ֱ�� of Cambridge - Melissa Uchida

New results deal a blow to the theoretical sterile neutrino

UK researchers awarded £30m for global science project to better understand matter and antimatter