探花直播 of Cambridge - Harry Cliff

Cambridge physicists announce results that boost evidence for new fundamental physics

Anonymous — Tue, 19 Oct 2021 12:44:47 +0000

In March 2020, the same experiment released evidence of particles breaking one of the core principles of the Standard Model 鈥� our best theory of particles and forces 鈥� suggesting the possible existence of new fundamental particles and forces.

Now, further measurements by physicists at Cambridge鈥檚 Cavendish Laboratory have found similar effects, boosting the case for new physics.

探花直播Standard Model describes all the known particles that make up the universe and the forces that they interact through. It has passed every experimental test to date, and yet physicists know it must be incomplete. It does not include the force of gravity, nor can it account for how matter was produced during the Big Bang, and contains no particle that could explain the mysterious dark matter that astronomy tells us is five times more abundant than the stuff that makes up the visible world around us.

As a result, physicists have long been hunting for signs of physics beyond the Standard Model that might help us to address some of these mysteries.

One of the best ways to search for new particles and forces is to study particles known as beauty quarks. These are exotic cousins of the up and down quarks that make up the nucleus of every atom.

Beauty quarks don鈥檛 exist in large numbers in the world around as they are incredibly short-lived 鈥� surviving on average for just a trillionth of a second before transforming or decaying into other particles. However, billions of beauty quarks are produced every year by CERN鈥檚 giant particle accelerator, the Large Hadron Collider, which are recorded by a purpose-built detector called LHCb.

探花直播way beauty quarks decay can be influenced by the existence of undiscovered forces or particles. In March, a team of physicists at LHCb released results showing evidence that beauty quarks were decaying into particles called muons less often than to their lighter cousins, electrons. This is impossible to explain in the Standard Model, which treats electrons and muons identically, apart from the fact that electrons are around 200 times lighter than muons. As a result, beauty quarks ought to decay into muons and electrons at equal rates. Instead, the physicists at LHCb found that the muon decay was only happening around 85% as often as the electron decay.

探花直播difference between the LHCb result and the Standard Model was about three units of experimental error, or 鈥�3 sigma鈥� as it is known in particle physics. This means there is only around a one in a thousand chance of the result being caused by a statistical fluke.

Assuming the result is correct, the most likely explanation is that a new force that pulls on electrons and muons with different strengths is interfering with how these beauty quarks decay. However, to be sure if the effect is real more data is needed to reduce the experimental error. Only when a result reaches the 鈥�5 sigma鈥� threshold, when there is less than a one in a million chance of it being due to random chance, will particle physicists start to consider it a genuine discovery.

鈥� 探花直播fact that we鈥檝e seen the same effect as our colleagues did in March certainly boosts the chances that we might genuinely be on the brink of discovering something new,鈥� said Dr Harry Cliff from the Cavendish Laboratory. 鈥淚t鈥檚 great to shed a little more light on the puzzle.鈥�

Today鈥檚 result聽examined two new beauty quark decays from the same family of decays as used in the March result. 探花直播team found the same effect 鈥� the muon decays were only happening around 70% as often as the electron decays. This time the error is larger, meaning that the deviation is around 鈥�2 sigma鈥�, meaning there is just over a 2% chance of it being due to a statistical quirk of the data. While the result isn鈥檛 conclusive on its own, it does add further support to a growing pile of evidence that there are new fundamental forces waiting to be discovered.

鈥� 探花直播excitement at the Large Hadron Collider is growing just as the upgraded LHCb detector is about to be switched on and further data collected that will provide the necessary statistics to either claim or refute a major discovery,鈥� said Professor Val Gibson, also from the Cavendish Laboratory.

Results announced by the LHCb experiment at CERN have revealed further hints for phenomena that cannot be explained by our current theory of fundamental physics.

探花直播fact that we鈥檝e seen the same effect as our colleagues did in March certainly boosts the chances that we might genuinely be on the brink of discovering something new

Harry Cliff

CERN

View of the LHCb detector

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New result from LHCb experiment challenges leading theory in physics

sc604 — Tue, 23 Mar 2021 09:42:57 +0000

Results from the LHCb Collaboration at CERN suggests particles are not behaving the way they should according to the guiding theory of particle physics 鈥� suggesting gaps in our understanding of the Universe.

Physicists from the Universities of Cambridge, Bristol, and Imperial College London led the analysis of the data to produce this result, with funding from the Science and Technology Facilities Council.聽探花直播result - which has not yet been peer-reviewed -聽was announced today at the聽Moriond Electroweak Physics conference聽and聽published as a preprint.

Beyond the Standard Model

Scientists across the world will be paying close attention to this announcement as it hints at the existence of new particles not explained by the Standard Model.

探花直播Standard Model is the current best theory of particle physics, describing all the known fundamental particles that make up our Universe and the forces that they interact with. However, the Standard Model cannot explain some of the deepest mysteries in modern physics, including what dark matter is made of and the imbalance of matter and antimatter in the Universe.

Dr Mitesh Patel of Imperial College London, and one of the leading physicists behind the measurement, said: 鈥淲e were actually shaking when we first looked at the results, we were that excited. Our hearts did beat a bit faster.

鈥淚t鈥檚 too early to say if this genuinely is a deviation from the Standard Model but the potential implications are such that these results are the most exciting thing I鈥檝e done in 20 years in the field. It has been a long journey to get here.鈥�

Building blocks of nature

Today鈥檚 results were produced by the LHCb experiment, one of four huge particle detectors at CERN鈥檚 Large Hadron Collider (LHC).

探花直播LHC is the world鈥檚 largest and most powerful particle collider 鈥� it accelerates subatomic particles to almost the speed of light, before smashing them into each other.

These collisions produces a burst of new particles, which physicists then record and study in order to better understand the basic building blocks of nature.

探花直播LHCb experiment is designed to study particles called 鈥榖eauty quarks鈥�, an exotic type of fundamental particle not usually found in nature but produced in huge numbers at the LHC.

Once the beauty quarks are produced in the collision, they should then decay in a certain way, but the LHCb team now has evidence to suggest these quarks decay in a way not explained by the Standard Model.

Questioning the laws of physics

探花直播updated measurement could question the laws of nature that treat electrons and their heavier cousins, muons, identically, except for small differences due to their different masses.聽

According to the Standard Model, muons and electrons interact with all forces in the same way, so beauty quarks created at LHCb should decay into muons just as often as they do to electrons.

But these new measurements suggest this is not happening.

One way these decays could be happening at different rates is if never-before-seen particles were involved in the decay and tipped the scales in favour of electrons.

Dr Paula Alvarez Cartelle from Cambridge鈥檚 Cavendish Laboratory, was one of the leaders of the team that found the result, said: 鈥淭his new result offers tantalising hints of the presence of a new fundamental particle or force that interacts differently with these different types of particles.

鈥� 探花直播more data we have, the stronger this result has become. This measurement is the most significant in a series of LHCb results from the past decade that all seem to line up 鈥� and could all point towards a common explanation.

鈥� 探花直播results have not changed, but their uncertainties have shrunk, increasing our ability to see possible differences with the Standard Model.鈥�

Not a foregone conclusion

In particle physics, the gold standard for discovery is five standard deviations 鈥� which means there is a 1 in 3.5 million chance of the result being a fluke. This result is three deviations 鈥� meaning there is still a 1 in 1000 chance that the measurement is a statistical coincidence.

It is therefore too soon to make any firm conclusions. However, while they are still cautious, the team members are nevertheless excited by this apparent deviation and its potentially far-reaching implications.

探花直播LHCb scientists say there has been a breadcrumb trail of clues leading up to this result 鈥� with a number of other, less significant results over the past seven years also challenging the Standard Model in a similar way, though with less certainty.

If this result is what scientists think it is 鈥� and hope it is 鈥� there may be a whole new area of physics to be explored.

Dr Konstantinos Petridis of the 探花直播 of Bristol, who also played a lead role in the measurement, said: 鈥� 探花直播discovery of a new force in nature is the holy grail of particle physics. Our current understanding of the constituents of the Universe falls remarkably short 鈥� we do not know what 95% of the Universe is made of or why there is such a large imbalance between matter and anti-matter.

鈥� 探花直播discovery of a new fundamental force or particle, as hinted at by the evidence of differences in these measurements could provide the breakthrough required to start to answer these fundamental questions.鈥�

Dr Harry Cliff, LHCb Outreach Co-Convener, from Cambridge鈥檚 Cavendish Laboratory, said: 鈥淭his result is sure to set physicists鈥� hearts beating a little faster today. We鈥檙e in for a terrifically exciting few years as we try to figure out whether we鈥檝e finally caught a glimpse of something altogether new.鈥�

It is now for the LHCb collaboration to further verify their results by collating and analysing more data, to see if the evidence for some new phenomena remains.

Additional information 鈥� about the result

探花直播results聽compare the decay rates of Beauty mesons into final states with electrons with those into muons.

探花直播LHCb experiment is one of the four large experiments at the Large Hadron Collider (LHC) at CERN in Geneva, and is designed to study decays of particles containing a beauty quark

This is the quark with the highest mass forming bound states. 探花直播resulting precision measurements of matter-antimatter differences and rare decays of particles containing a beauty quark allow sensitive tests of the Standard Model of particle physics.

Rather than flying out in all directions, beauty quarks that are created in the collisions of the proton beams at LHC stay close to the beam pipe.

探花直播UK team studied a large number of beauty or b quarks decaying into a strange-quark and two oppositely charged leptons. By measuring how often the b-quark decays into a final state containing a pair of muons or a pair of electrons, they found evidence that the laws of physics might be different, depending on whether the final state contains electrons or muons.聽

Since the b-quark is heavy compared to the masses of the electron and muon it is expected that the b-quark decays with the same probability into a final state with electrons and muons. 探花直播ratio between the two decay probabilities is hence predicted to be one.

However analysis of the UK team found evidence that the decay probability is less than one.

UK particle physicists have today announced 鈥榠ntriguing鈥� results that potentially cannot be explained by the current laws of nature.

This new result offers tantalising hints of the presence of a new fundamental particle or force that interacts differently with these different types of particles.

Paula Alvarez Cartelle

CERN

LHCb experiment

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Opinion: Large Hadron Collider sees tantalising hints of a new particle that could revolutionise physics

Anonymous — Thu, 17 Dec 2015 11:38:32 +0000

At the start of December a rumour swirled around the internet and physics lab coffee rooms that researchers at the Large Hadron Collider had spotted a new particle. After a three-year drought that followed the discovery of the Higgs boson, could this be the first sign of new physics that particle physicists have all been desperately hoping for?

Researchers working on the LHC experiments remained tight-lipped until December 14 when physicists packed out CERN鈥檚 main auditorium to hear presentations from the scientists working on CMS and ATLAS experiments, the two gargantuan particle detectors that discovered the Higgs boson in 2012. Even watching the online webcast, the excitement was palpable.

Everybody was wondering if we would witness the beginning of a new age of discovery. 探花直播answer is 鈥� maybe.

Baffling bump

探花直播CMS results were revealed first. At first the story was familiar, an impressive range of measurements that again and again showed no signs of new particles. But in the last few minutes of the presentation a subtle but intriguing bump on a graph was revealed that hinted at a new heavy particle decaying into two photons (particles of light). 探花直播bump appeared at a mass of around 760GeV (the unit of mass and energy used in particle physics 鈥� the Higgs boson has a mass of about 125 GeV) but was far too weak a signal to be conclusive on its own. 探花直播question was, would ATLAS see a similar bump in the same place?

探花直播ATLAS presentation mirrored the one from CMS, another list of non-discoveries. But, saving the best for last, a bump was unveiled towards the end, close to where CMS saw theirs at 750GeV 鈥� but bigger. It was still too weak to reach the statistical threshold to be considered solid evidence, but the fact that both experiments saw evidence in the same place is exciting.

探花直播discovery of the Higgs back in 2012 completed the Standard Model, our current best theory of particle physics, but left many unsolved mysteries. These include the nature of 鈥�dark matter鈥�, an invisible substance that makes up around 85% of the matter in the universe, the weakness of gravity and the way that the laws of physics appear fine-tuned to allow life to exist, to name but a few.

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Could supersymmetry one day crack the mystery of all the dark matter lurking in galaxy clusters? NASA/wikimedia

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A number of theories have been proposed to solve these problems. 探花直播most popular is an idea called supersymmetry, which proposes that there is a heavier super-partner for every particle in the Standard Model. This theory provides an explanation for the fine-tuning of the laws of physics and one of the super-partners could also account for dark matter.

Supersymmetry predicts the existence of new particles that should be in reach of the LHC. But despite high hopes the first run of the machine from 2009-2013 revealed a barren subatomic wilderness, populated only by a solitary Higgs boson. Many of the theoretical physicists working on supersymmetry have found the recent results from the LHC rather depressing. Some had begun to worry that answers to the outstanding questions in physics might lie forever beyond our reach.

This summer the 27km LHC restarted operation after a two-year upgrade that almost doubled its collision energy. Physicists are eagerly waiting to see what these collisions reveal, as higher energy makes it possible to create heavy particles that were out of reach during the first run. So this hint of a new particle is very welcome indeed.

A cousin of Higgs?

Andy Parker, head of Cambridge鈥檚 Cavendish Laboratory and senior member of the ATLAS experiment, told me: 鈥淚f the bump is real, and it decays into two photons as seen, then it must be a boson, most likely another Higgs boson. Extra Higgs are predicted by many models, including supersymmetry鈥�.

Perhaps even more exciting, it could be a type of graviton, a hypothesised particle associated with the force of gravity. Crucially, gravitons exist in theories with additional dimensions of space to the three (height, width and depth) we experience.

For now, physicists will remain sceptical 鈥� more data is needed to rule this intriguing hint in or out. Parker described the results as 鈥減reliminary and inconclusive鈥� but added, 鈥渟hould it turn out to be the first sign of physics beyond the standard model, with hindsight, this will be seen as historic science.鈥�

Whether this new particle turns out to be real or not, one thing that everyone agrees on is that 2016 is going to be an exciting year for particle physics.

Harry Cliff, Particle physicist and Science Museum fellow, 探花直播 of Cambridge

This article was originally published on 探花直播Conversation. Read the original article.

探花直播opinions expressed in this article are those of the individual author(s) and do not represent the views of the 探花直播 of Cambridge.

Harry Cliff (Cavendish Laboratory) discusses the potential discovery of a new particle at the Large Hadron Collider and its implications for particle physics.

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探花直播Large Hadron Collider/ATLAS at CERN

探花直播text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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