̽��ֱ�� of Cambridge - CERN

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 – our best theory of particles and forces – suggesting the possible existence of new fundamental particles and forces.

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

̽��ֱ��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’t exist in large numbers in the world around as they are incredibly short-lived – 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’s giant particle accelerator, the Large Hadron Collider, which are recorded by a purpose-built detector called LHCb.

̽��ֱ��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.

̽��ֱ��difference between the LHCb result and the Standard Model was about three units of experimental error, or ‘3 sigma’ 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 ‘5 sigma’ 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.

“ ̽��ֱ��fact that we’ve 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,” said Dr Harry Cliff from the Cavendish Laboratory. “It’s great to shed a little more light on the puzzle.”

Today’s result examined two new beauty quark decays from the same family of decays as used in the March result. ̽��ֱ��team found the same effect – 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 ‘2 sigma’, meaning there is just over a 2% chance of it being due to a statistical quirk of the data. While the result isn’t 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.

“ ̽��ֱ��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,” 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.

̽��ֱ��fact that we’ve 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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Yes

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 – 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. ̽��ֱ��result - which has not yet been peer-reviewed - was announced today at the Moriond Electroweak Physics conference and 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.

̽��ֱ��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: “We were actually shaking when we first looked at the results, we were that excited. Our hearts did beat a bit faster.

“It’s 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’ve done in 20 years in the field. It has been a long journey to get here.”

Building blocks of nature

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

̽��ֱ��LHC is the world’s largest and most powerful particle collider – 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.

̽��ֱ��LHCb experiment is designed to study particles called ‘beauty quarks’, 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

̽��ֱ��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.

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’s Cavendish Laboratory, was one of the leaders of the team that found the result, said: “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.

“ ̽��ֱ��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 – and could all point towards a common explanation.

“ ̽��ֱ��results have not changed, but their uncertainties have shrunk, increasing our ability to see possible differences with the Standard Model.”

Not a foregone conclusion

In particle physics, the gold standard for discovery is five standard deviations – which means there is a 1 in 3.5 million chance of the result being a fluke. This result is three deviations – 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.

̽��ֱ��LHCb scientists say there has been a breadcrumb trail of clues leading up to this result – 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 – and hope it is – there may be a whole new area of physics to be explored.

Dr Konstantinos Petridis of the ̽��ֱ�� of Bristol, who also played a lead role in the measurement, said: “ ̽��ֱ��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 – 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.

“ ̽��ֱ��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.”

Dr Harry Cliff, LHCb Outreach Co-Convener, from Cambridge’s Cavendish Laboratory, said: “This result is sure to set physicists’ hearts beating a little faster today. We’re in for a terrifically exciting few years as we try to figure out whether we’ve finally caught a glimpse of something altogether new.”

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 – about the result

̽��ֱ��results compare the decay rates of Beauty mesons into final states with electrons with those into muons.

̽��ֱ��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. ̽��ֱ��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.

̽��ֱ��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.

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. ̽��ֱ��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 ‘intriguing’ 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

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

Women in STEM: Holly Pacey

sc604 — Thu, 11 Jul 2019 06:28:49 +0000

My ambition to have a career in physics research began when I was at school. I grew up in Nottingham, where my Dad was the main homemaker and worked from home; and my Mum worked in a hospital pharmacy. I attended my local comprehensive and sixth form before moving to Cambridge to study Natural Sciences at King’s College.

I spent two summers working in the Cambridge Institute of Astronomy, and this sparked a desire to work in particle physics. After graduating with my MSc, I began working towards a PhD in high energy physics with the ATLAS experiment. What strikes me most about the environment in Cambridge, compared to other institutions, is the atmosphere of collaboration. Improving your understanding of your subject and exploring new and creative research ideas with everyone in the group is always prioritised above rank – there is no such thing as a stupid question here.

Having the opportunity to work with CERN is incredible. ̽��ֱ��diversity of people, with a huge range of ideas, all working towards a common goal is very inspiring. ̽��ֱ��calibre of research at both institutions motivates you to become the best researcher you can, but with enough support that you aren’t overwhelmed.

On a grand scale, my field is trying to understand what the universe is made of at a fundamental level. We are looking at how the constituent parts – called particles - can interact and combine to take us from the high energy Big Bang to the universe we see today. My research aims to find evidence for new particles in the data taken with the ATLAS detector at the Large Hadron Collider, which would allow our current Standard Model of particle physics to be extended. For example, I have focused on searches for new particles predicted by a model called Supersymmetry, currently the most popular extension to the standard model that could explain phenomena such as dark matter.

A key moment for me was attending my first ATLAS conference focusing on the collaboration of the different new-physics groups. ̽��ֱ��many innovative analysis techniques being presented were very interesting and I learned a lot in the plentiful discussions, both about the work I had contributed to the conference and that of others. In the long term, I hope my research will contribute to our understanding of the universe, and lead to an exciting career in academia.

Part of my research involves reconstructing ‘missing’ particles that ATLAS isn’t designed to detect. These are either neutrinos or new physics particles and measuring them well involves carefully balancing all aspects of the detector. Generally, I spend my days doing data analysis. This can involve using computer simulations of background and signal events, using statistics and techniques like machine learning techniques to optimise where to look in the data to find new physics.

My most interesting project so far is a new project looking for signs of new physics or behaviour in a data-data comparison of oppositely charged electron-muon events. This idea is very exciting, as a deviation from the Standard Model expectation could be explained by many different new models. It also doesn’t rely on simulated data, which is getting more important now that ATLAS has taken such vast amounts of data that simulation is struggling to keep up computationally.

If you are passionate about a subject and have the drive to work hard on it then that should speak for itself. There will be challenges in your career whatever you choose to do, but the more women that follow their ambitions into STEM now, the easier it will be for the next generation of aspiring scientists.

Holly Pacey is a PhD candidate in the High Energy Physics Group based at the Cavendish Laboratory, and works on the ATLAS experiment. She spent the 2017-18 academic year working at CERN in Geneva, which operates the largest particle physics laboratory in the world.

Yes

Antimatter matters at the Royal Society Summer Exhibition

Anonymous — Mon, 04 Jul 2016 14:07:01 +0000

Why we live in a universe made of matter, rather than a universe with no matter at all, is one of science’s biggest questions. ̽��ֱ��behaviour of antimatter, a rare oppositely charged counterpart to normal matter, is thought to be key to understanding why. However, the nature of antimatter is a mystery. Scientists use data from the LHCb and ALPHA experiments at CERN to study antiparticles and antiatoms in order to learn more about it. Some of these scientists, from the ̽��ֱ�� of Cambridge and other UK institutions, will present their work at the Royal Society’s annual Summer Science Exhibition which opens to the public tomorrow (5 July 2016).

At CERN’s Large Hadron Collider particle accelerator, matter and antimatter versions of fundamental particles are produced when the accelerator beams smash into each other. ̽��ֱ��LHCb experiment records the traces these particles leave behind as they fly outwards from the beam collisions with exquisite precision, enabling scientists to identify the particles and deduce whether they are matter or antimatter. At larger scales, antimatter is studied in CERN’s antiproton decelerator complex, when antiprotons are joined with antielectrons to form anti-hydrogen atoms. ̽��ֱ��ALPHA experiment holds these antiatoms in suspension so that their structure and behavior can be studied. Both experiments are currently recording data that will enable scientists to carefully build up an understanding of why antimatter appears to behave the way it does.

̽��ֱ�� ̽��ֱ�� of Cambridge is a founder institute of the LHCb experiment and plays a major part in the construction and operation of the detectors that determine the identity of particles. ̽��ֱ��detectors use the Ring-Imaging Cherenkov radiation technique via which particles emit radiation as they travel faster than the speed of light in the material of the detectors. ̽��ֱ��principles behind this technique and the data produced will be on view in the Royal Society Summer Science Exhibition for visitors to examine.

Professor Val Gibson of the ̽��ֱ�� of Cambridge and former UK Spokesperson for the experiment said: “Antimatter might sound like science fiction, but it is one of the biggest mysteries in science today. We’re going to show everyone just why it matters so much – from what it can tell us about the earliest universe, to how we study it at the frontiers of research, to how it has everyday uses in medical imaging.“

Visitors to the Exhibition will also be able to see how fundamental particles and antiparticles are identified with the LHCb experiment, talk to researchers to discover what this science is like, try the experimental techniques used to hold and study anti-atoms with the ALPHA experiment, and move, image and locate antimatter within a PET scanner system.

̽��ֱ��Royal Society’s Summer Science Exhibition is weeklong festival of cutting edge science from across the UK, featuring 22 exhibits which give a glimpse into the future of science and tech. Visitors can meet the scientists who are on hand at their exhibits, take part in activities and live demonstrations and attend talks. Entrance is free.

Scientists from the ̽��ֱ�� of Cambridge are presenting their research into the nature of antimatter at this year’s Royal Society Summer Exhibition.

Antimatter might sound like science fiction, but it is one of the biggest mysteries in science today.

Val Gibson

Summer Science Exhibition 2016: Antimatter Matters

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Yes

Large Hadron Collider restarts after two years

sc604 — Tue, 07 Apr 2015 14:26:52 +0000

Early on Easter Sunday, the Large Hadron Collider’s second run got underway, when proton beams began rotating in the 27-kilometre ring for the first time in two years. Over the coming weeks, the beams will be accelerated to speeds close to the speed of light, running at the unprecedented energy of 13 Terra-electron-volts (TeV), well above the 8 TeV level of the last run, which discovered the long-sought Higgs boson in 2012.

̽��ֱ��new run will subject the Standard Model of particle physics to its toughest tests yet, and may help identify some of the fundamental forces of nature that the Standard Model does not include. With 13 TeV proton-proton collisions expected before summer, the LHC experiments will soon be exploring uncharted territory in particle physics.

Cambridge researchers at CERN are playing a major part in preparing the ATLAS detector – the largest of LHC’s seven particle detectors – for action with new upgraded systems ready to go to work as soon as the beam start to collide. All the preparations are in place to being to analyse the data and early results could be expected before the end of the year if all goes well.

“ ̽��ֱ��current Standard Model explains the known particles and forces, and the discovery of the Higgs completed that picture,” said Professor Andy Parker, Head of the Cavendish Laboratory at the ̽��ֱ�� of Cambridge, and one of the founders of ATLAS. “But the Standard Model does not explain dark matter, which is believed to make up most of the Universe, nor Dark Energy, a mysterious force driving the galaxies ever further apart.”

̽��ֱ��answers to these problems in cosmology might lie in the realm of sub-atomic physics studied at CERN. For example, the LHC might be able to produce dark matter particles, which would be glimpsed in the debris of collisions detected by the ATLAS and CMS experiments.

“Even more exciting is the possibility that the Universe could have more than three space dimensions, and that other spaces are hidden all around us,” said Parker. “This could also be revealed at CERN by the production and decay of microscopic quantum black holes, a particular interest of the Cambridge researchers at CERN. Detailed studies of the Higgs boson are also going to test our understanding of the Standard Model, with any unexpected effects leading us towards new physics. ̽��ֱ��upgrade of the LHC will allow scientists to search for new discoveries which have so far been out of reach.”

̽��ֱ��upgrade was a Herculean task. Some 10,000 electrical interconnections between the LHC’s superconducting dipole magnets were consolidated. Magnet protection systems were added, while cryogenic, vacuum and electronics were improved and strengthened. Additionally, the beams will be set up in such a way that they will produce more collisions by bunching protons closer together; with the time separating bunches being reduced from 50 nanoseconds to 25 nanoseconds.

After the discovery of the Higgs boson in 2012 by the ATLAS and CMS experiments, physicists will be putting the Standard Model of particle physics to its most stringent test yet, searching for new physics beyond this well-established theory describing particles and their interactions.

With superconducting magnets cooled to the extreme temperature of -271°C, the LHC is capable of simultaneously circulating particles in opposite directions, in tubes under ultrahigh vacuum, at a speed close to that of light. Gigantic particle detectors, located at four interaction points along the ring, record collisions generated when the beams collide.

In routine operation, protons cover some 11,245 laps of the LHC per second, producing up to 1 billion collisions per second. ̽��ֱ��CERN computing centre stores over 30 petabytes of data from the LHC experiments every year, the equivalent of 1.2 million Blu-ray discs.

After two years of intense maintenance and consolidation, and several months of preparation for restart, the Large Hadron Collider, the most powerful particle accelerator in the world, is back in operation after a major upgrade.

̽��ֱ��upgrade of the LHC will allow scientists to search for new discoveries which have so far been out of reach

Andy Parker

CERN

3D dipole integration panoramic poster

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

Yes

Firing up the proton smasher

fpjl2 — Mon, 16 Feb 2015 12:33:08 +0000

While it slept, we were allowed into the tunnels.

̽��ֱ��Large Hadron Collider (LHC) had shut down for two years to upgrade following the discovery of the Higgs boson. In the main ring, 175 m underground, chunks had been cut out of the snaking tubes for essential maintenance. These tubes fire protons in opposite directions, whipping them ever faster until they almost reach the speed of light. Along the 27 km run are four ‘experiments’: vast machines envelop the points at which tubes intersect and particles collide to capture the results. ̽��ֱ��largest of these, ATLAS, is the size of a six-storey building.

Each collision, known as an ‘event’, produces a splurge of elementary particles such as quarks, gluons and – as we now know – Higgs bosons. On average, events occur 40 million times a second in the LHC.

̽��ֱ��precision required for these events is exquisite. Our guide tells us to imagine two people standing six miles apart and each simultaneously firing a gun so that the bullets meet exactly head-on. Except instead of bullets, imagine needles. Inside the tunnels, engineers zip past on bicycles – the best way to get around underground unless you’re a proton. Next to every lift shaft is a bike rack.

In the next few months, the LHC will be switched back on. ̽��ֱ��2012 triumph of demonstrating the Higgs boson affirmed the Standard Model: the elegant solution to the building blocks of the Universe. Now, with an anticipated almost doubling of energy for the LHC’s second run, physicists are aiming to “go beyond” the Standard Model.

One of the central goals is to prove or disprove the theory of supersymmetry: the “prime candidate” theory for unlocking the mystery of the dark matter in our Universe.

“Observable matter only makes up 5% of the Universe; the rest is what we call dark matter. We know it’s there because we can see galaxies rotating at velocities which require surrounding matter for such gravitational pull – but, unlike the part of the galaxies that we can see, we cannot detect it optically,” said Professor Val Gibson, Head of the Cambridge High Energy Physics (HEP) group.

Supersymmetry theory essentially predicts that every particle in the Standard Model has a matching particle waiting to be found. These partner particles (or ‘sparticles’) could be candidates for dark matter, but we haven’t yet seen them – perhaps because they are heavier and take more energy to generate, a problem LHC Run II could overcome.

“Supersymmetry theory predicts there is a sister particle of the electron called a ‘selectron’, which would have integer ‘spin’: its intrinsic angular momentum. For the quark, there would be a supersymmetric ‘squark’, and so on for every elementary particle we know,” said Gibson. If supersymmetry is correct, there would also be a further four Higgs bosons for us to discover.

“Proton collisions in the LHC might produce a heavy supersymmetric particle which decays into its lightest form, a light neutral particle, but different from those we know about in the Standard Model,” said Gibson.

“We have been looking for supersymmetry particles throughout the first run of the LHC, and the increase in power for Run II means we can look at higher energies, higher mass, and gradually blot out more areas of the map in which supersymmetrical particles could be hiding.”

Will supersymmetry be proved by the end of next year, or will the data show it’s a red herring? For HEP research associate Dr Jordi Garra Ticó, what is really fundamental is experimental evidence. “I just want to see what nature has prepared for us, whether that’s consistent with some current theory or whether it’s something else that no one has ever thought about yet, outside of current knowledge.”

̽��ֱ��two experiments that Cambridge researchers work on are the mighty ATLAS and the more subtle LHCb – known as LHC ‘Beauty’ – which is Gibson and Garra Ticó’s focus. Beauty complements the power of ATLAS, allowing scientists to ‘creep up’ on new physics by capturing rare particle decays that happen every 100 million events.

Garra Ticó spent six months in Cambridge before taking up residence at CERN, where he works on LHCb. LHCb’s 10 million events a second create 35 kbyte of data each, a figure that is expected to go up to 60 kbyte during Run II – too much to ever imagine storing. “There is no guidebook,” he explained. “These machines are prototypes of themselves.”

ATLAS, the biggest experiment, feels like the lair of a colossal hibernating robot. Engineers perch in the crevices of the giant machine, tinkering away like tiny cleaner birds removing parasites. And sealed in the heart of this monster is layer upon layer of the most intricate electronics ever devised.

Dr Dave Robinson arrived in CERN as a PhD student in 1985, and joined the Cambridge HEP group in 1993. He went back to CERN in 2004 – expecting a stint of “one to two years” – and has remained. He is now Project Leader for the most critical detector system within ATLAS, the Inner Detector, which includes the ‘semi-conductor tracker’ (SCT), partially built
in Cambridge.

Each collision event inside ATLAS leaves an impression on the layers of silicon that make up the SCT like an onion skin – enabling scientists to reconstruct the trajectory of particles in the events. “ ̽��ֱ��sensitivity of the tracker is vital for making precise measurements of the thousands of particles generated by the head-on collisions between protons, including decay products from particles like b-quarks which only exist for picoseconds after the collision,” said Robinson.

He is currently working with Gibson and colleagues at the Cavendish Laboratory on the next generation of radiation-proof silicon technology in preparation for the LHC shutdown of 2020, the next time they will be able to get at the SCT, which is otherwise permanently locked in the core of ATLAS. ̽��ֱ��technology will have an impact on areas like satellite telecommunications, where cheaper, radiation-hardened electronics could have a huge effect.

This, for Gibson, is the way science works: solving technical problems to reveal nature’s hidden secrets, and then seeing the wider applications. She recalls being in CERN when she was a postdoc in the 1980s at the same time as Tim Berners-Lee, who was working on computer-sharing software to solve the anticipated data deluge from LHC-precursor UA1. He ended up calling it the World Wide Web.

Inset image – top: representation of the Higgs Boson particle; Credit: CERN.

Inset image – bottom: Professor Val Gibson.

̽��ֱ��Large Hadron Collider is being brought back to life, ready for Run II of the “world’s greatest physics experiment”. Cambridge physicists are among the army who keep it alive.

I just want to see what nature has prepared for us, whether that’s consistent with some current theory or whether it’s something else that no one has ever thought about yet, outside of current knowledge

Jordi Garra Ticó

CERN

Large Hadron Collider

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Yes

Large Hadron ‘insider’

fpjl2 — Fri, 14 Jun 2013 10:33:57 +0000

In October 2000, I arrived in Geneva from Stansted airport ready to start a two year research job at the European centre for particle physics (CERN) with my heart in my throat. This was before all of the recent excitement about the Large Hadron Collider, but for a particle physicist, CERN is the ultimate temple of physics and for me, it was my lifetime ambition to work there. I had recently daringly, and many said stupidly, turned down a life-time lectureship at another university so that I might have a chance of working at CERN (the offer came with an inflexible initial start date).

CERN really is an amazing place. There are some 10,000 physicists and engineers working on the site, which straddles the Franco-Swiss border, just outside Geneva, underneath the Jura Mountains. Everyone is working for ̽��ֱ��Cause - our common goal is to find out what the stuff that makes up our universe is like, and how it behaves.

When I arrived, the Large Hadron Collider had not been built and the previous one was toward the end of its operation. While I was there, there was a potential hint of a higgs signal in the data. All of a sudden, CERN was completely abuzz. Everyone was trying to find out the latest rumours. There were four independent experiments back then, all competing with each other. ̽��ֱ��idea behind this was that they can check each other's results, and keep each other unbiased. But because of this competition, the experiments were rushing to make a big discovery before the others, but they also wanted to keep their data secret so as not to give the others a clue.

I am a theoretical physicist: I do the mathematics and interpret experimental data, rather than actually run the experiments. My theoretical colleagues had spies on the experiments, which they were trying to push for information to find out the latest on the Higgs boson. Then they would tell their friends, and all sorts of wild rumours would start to fly about. Mostly this wasn't done for any personal advantage, it was just that we were fascinated, and really wanted to know what was going on at the cutting edge as early as possible. Once every month or two, the experiments would hold seminars and do official releases of data. Sometimes we already knew what they were going to say but sometimes it was a surprise.

In the end, it turned out that the hint of a signal that we were all getting so excited about was just a random fluctuation of the data. We couldn't really know this for sure though until we had seen the LHC data, and that didn't arrive for another eight years or so.

At the time though, since there was the hint of a higgs boson signal in the data, and since the collider only had a year or so left before shutdown to make way for the LHC, the accelerator engineers started to ramp up the energy as much as possible. This was a risky strategy, because parts started to break down, being under a lot of strain (I imagine the accelerator engineers, like Scottie from Star Trek, shouting "she cannae take any more captain!") My friend worked on one of the experiments, and many times he was paged from the pub and had to taxi up to the experiment to try and get it working once it had all broken down.

Since the beam was still on, the experiment was losing valuable data that all of the other experiments were taking, and could lose out on a discovery as a result. One time, his boss had to be called in at 1am from a birthday party to coordinate everyone. ̽��ֱ��first thing to do was pour coffee down him to try to sober him up.

People often think that the biggest man made experiment on earth will be ultra high-tech and efficiently squeaky clean. In some ways this is true, but there was also a sort of Heath-Robinson aspect too. For instance, the accelerator is a complicated beast with thousands of different magnets and sub-pieces, all with complex and nervy feedback across them. As a result, driving it is something of a black art: apparently you get the "feel" of how it is behaving that day and some of the operators were particularly good at this knack. During 1998, the best operators by far were the French accelerator engineers: they just had the most experience, and an uncanny sense of how it would behave in the following five minutes. That year, the football world cup was in France, and we were praying that France would be knocked out early because the rate of good beam was really low: all the good French operators were taking days off to watch their team's matches.

It was hard getting research jobs in the subject back then: the competition was ultra-tough, and I was far from sure I would be able to get the next job. Whenever I thought about leaving the subject, I think how sad I would be to read about a big discovery (like the recent Higgs boson discovery) and to know that I could have been involved, at least in some small way. I really feel that I am super lucky to be still researching in the field. I work from the ̽��ֱ�� of Cambridge, but visit CERN several times a year for research. If you ever go to Geneva, I thoroughly recommend you to get on the CERN website several weeks beforehand, and book yourself in to a guided tour. I guarantee it will be an incredible scientific journey.

Inset image: Ben Allanach working it out during his time at CERN

In a recent talk for TEDx, theoretical physicist Professor Ben Allanach explored the research he undertook during the two years he spent working on the Large Hadron Collider at CERN in Switzerland. Here, he takes us back to his time as one of the scientists working on the biggest scientific experiment in human history.

We were praying that France would be knocked out of the World Cup because the rate of good beam was really low

Ben Allanach

̽��ֱ��micro frontier: Benjamin Allanach at TEDxDanubia 2013

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̽��ֱ��Large Hadron Collider projected onto the Old Schools, the ̽��ֱ��'s administrative centre, during the 800th Anniversary celebration year

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