LHCb experiments cave at LHC. Credit: CERN
Imperial physicists are part of a team that has announced ‘intriguing’ results that may not be explained by our current laws of nature.
The LHCb collaboration at CERN found that particles do not behave as they should according to the leading theory of particle physics – the standard model.
The standard model of particle physics predicts that particles called beauty quarks, measured in the LHCb experiment, should equally decay into moons or electrons. However, the new result suggests that this may not be the case, which may indicate the existence of new particles or interactions not explained by the standard model.
“It’s too early to say if this is really a departure from the standard model, but the potential implications are that these results are the most exciting thing I’ve done in the field in 20 years.” – Dr Mitesh Patel
Physicists from Imperial College London and the Universities of Bristol and Cambridge led the analysis of the data to yield this result, with funding from the Science and Technology Policy Council. The result was announced today at the Moriond Electroweak Physics Conference and published as a preview.
Outside the standard model
The standard model is the current best theory of particle physics, which describes all the known fundamental particles that make up our universe, and the forces with which it interacts.
However, the standard model cannot explain some of the deepest mysteries in modern physics, including what dark matter consists of and the imbalance between matter and antimatter in the universe.
Researchers therefore looked for particles that behave in different ways than would be expected in the standard model to help explain some of these puzzles.
Dr Mitesh Patel, from the Department of Physics at Imperial and one of the leading physicists behind the measurement, said: ‘We were actually shaking when we first looked at the results, we were so excited. Our hearts did beat a little faster though.
‘It’s too early to say if this is really a departure from the standard model, but the potential implications are that the results are the most exciting thing I’ve done in the field in 20 years. It was a long journey to get here. ‘
Building blocks of nature
Today’s results were produced by the LHCb experiment, one of the four large particle detectors at CERN’s Large Hadron Collider (LHC).
The LHC is the world’s largest and most powerful particle impeller – it accelerates subatomic particles to almost the speed of light before colliding. These collisions produce an eruption of new particles which physicists then pick up and study to better understand the basic building blocks of nature.
The updated measurement questions the laws of nature that treat electrons and their heavier cousins, muons, identically, except for small differences due to their different masses.
According to the standard model, muons and electrons work in the same way with all forces, so beautification quarks created at LHCb must decay into muons just as often as for electrons.
But these new measurements suggest that decay can occur at different speeds, which may suggest that particles never seen before repel the scales of muons.
Very rare decay of a beauty meson with an electron and positron observed at LHCb. Credit: CERN
Imperial PhD student Daniel Moise, who made the first announcement of the results at the Moriond Electroweak Physics Conference, said: ‘The result provides an intriguing hint of a new fundamental particle or force that in a way interact with the particles currently known by science. not.
“If confirmed by further measurements, it will have a profound impact on our understanding of nature at the most fundamental level.”
Not a foregone conclusion
In particle physics, the gold standard for discovery is five standard deviations – meaning that the chance is 1 in 3.5 million that the result is a stroke of luck. The result is three deviations, which means that there is still a 1 in 1000 chance that the measurement is a statistical coincidence. It is therefore too early to draw any firm conclusions.
“We know that there must be new particles to discover because our current understanding of the universe falls short in so many ways.” – Dr Michael McCann
Dr Michael McCann, who also played a leading role in the Imperial team, said: ‘We know there must be new particles to discover because our current understanding of the universe falls short in so many ways – we do not know which 95% of the universe consists of, or why there is such a great imbalance between matter and anti-matter, nor do we understand the patterns in the properties of the particles of which we know.
“While we have to wait for the confirmation of these results, I hope that one day we can look at this as a turning point, where we have begun to answer some of these fundamental questions.”
It is now up to the LHCb collaboration to further verify their results by collecting and analyzing more data, to see if the evidence for new phenomena remains. The LHCb experiment is expected to begin collecting new data next year following an upgrade of the detector.
Reference: “Test of lepton universalality in beauty-quark decays” by LHCb collaboration: R. Aaij, C. Abellán Beteta, T. Ackernley, B. Adeva, M. Adinolfi, H. Afsharnia, CA Aidala, S. Aiola, Z Ajaltouni, S. Akar, J. Albrecht, F. Alessio, M. Alexander, A. Alfonso Albero, Z. Aliouche, G. Alkhazov, P. Alvarez Cartelle, S. Amato, Y. Amhis, L. An, L Anderlini, A. Andreianov, M. Andreotti, F. Archilli, A. Artamonov, M. Artuso, K. Arzymatov, E. Aslanides, M. Atzeni, B. Audurier, S. Bachmann, M. Bachmayer, JJ Back, P Baladron Rodriguez, V. Balagura, W. Baldini, J. Baptista Leite, RJ Barlow, S. Barsuk, W. Barter, M. Bartolini, F. Baryshnikov, JM Basels, G. Bassi, B. Batsukh, A. Battig , A. Bay, M. Becker, F. Bedeschi, I. Bediaga, A. Beiter, V. Belavin, S. Belin, V. Bellee, K. Belous, I. Belov, I. Belyaev, G. Bencivenni, E Ben-Haim, A. Berezhnoy, R. Bernet, D. Berninghoff, HC Bernstein, C. Bertella, A. Bertolin, C. Betancourt, F. Betti, Ia. Bezshyiko, S. Bhasin, J. Bhom, L. Bian, MS Bieker, S. Bifani, P. Billoir, M. Birch, FCR Bishop, A. Bitadze, A. Bizzeti, M. Bjørn, MP Blago, T. Blake , F. Blanc, S. Blusk, D. Bobulska, JA Boelhauve, O. Boente Garcia, T. Boettcher, A. Boldyrev, A. Bondar, N. Bondar, S. Borghi, M. Borisyak, M. Borsato, JT Borsuk, SA Bouchiba, TJV Bowcock, A. Boyer, C. Bozzi and MJ Bradley et al., March 22, 2021, High Energy Physics – Experiment.
arXiv: 2103.11769