̽��ֱ�� of Cambridge - particle physics

A peek inside the box that could help solve a quantum mystery

sc604 — Tue, 19 Nov 2024 15:22:24 +0000

Appearing as ‘bumps’ in the data from high-energy experiments, these signals came to be known as short-lived ‘XYZ states.’ They defy the standard picture of particle behaviour and are a problem in contemporary physics, sparking several attempts to understand their mysterious nature.

But theorists at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility in Virginia, with colleagues from the ̽��ֱ�� of Cambridge, suggest the experimental data could be explained with fewer XYZ states, also called resonances, than currently claimed.

̽��ֱ��team used a branch of quantum physics to compute the energy levels, or mass, of particles containing a specific ‘flavour’ of the subatomic building blocks known as quarks. Quarks, along with gluons, a force-carrying particle, make up the Strong Force, one of the four fundamental forces of nature.

̽��ֱ��researchers found that multiple particle states sharing the same degree of spin – or angular momentum – are coupled, meaning only a single resonance exists at each spin channel. This new interpretation is contrary to several other theoretical and experimental studies.

̽��ֱ��researchers have presented their results in a pair of companion papers published for the international Hadron Spectrum Collaboration (HadSpec) in Physical Review Letters and Physical Review D. ̽��ֱ��work could also provide clues about an enigmatic particle: X(3872).

̽��ֱ��charm quark, one of six quark ‘flavours’, was first observed experimentally in 1974. It was discovered alongside its antimatter counterpart, the anticharm, and particles paired this way are part of an energy region called ‘charmonium.’

In 2003, Japanese researchers discovered a new charmonium candidate dubbed X(3872): a short-lived particle state that appears to defy the present quark model.

“X(3872) is now more than 20 years old, and we still haven’t obtained a clear, simple explanation that everyone can get behind,” said lead author Dr David Wilson from Cambridge’s Department of Applied Mathematics and Theoretical Physics (DAMTP).

Thanks to the power of modern particle accelerators, scientists have detected a hodgepodge of exotic charmonium candidate states over the past two decades.

“High-energy experiments started seeing bumps, interpreted as new particles, almost everywhere they looked,” said co-author Professor Jozef Dudek from William & Mary. “And very few of these states agreed with the model that came before.”

But now, by creating a tiny virtual ‘box’ to simulate quark behaviour, the researchers discovered that several supposed XYZ particles might actually be just one particle seen in different ways. This could help simplify the confusing jumble of data scientists have collected over the years.

Despite the tiny volumes they were working with, the team required enormous computing power to simulate all the possible behaviours and masses of quarks.

̽��ֱ��researchers used supercomputers at Cambridge and the Jefferson Lab to infer all the possible ways in which mesons – made of a quark and its antimatter counterpart – could decay. To do this, they had to relate the results from their tiny virtual box to what would happen in a nearly infinite volume – that is, the size of the universe.

“In our calculations, unlike experiment, you can't just fire in two particles and measure two particles coming out,” said Wilson. “You have to simultaneously calculate all possible final states, because quantum mechanics will find those for you.”

̽��ֱ��results can be understood in terms of just a single short-lived particle whose appearance could differ depending upon which possible decay state it is observed in.

“We're trying to simplify the picture as much as possible, using fundamental theory with the best methods available,” said Wilson. “Our goal is to disentangle what has been seen in experiments.”

Now that the team has proved this type of calculation is feasible, they are ready to apply it to the mysterious particle X(3872).

“ ̽��ֱ��origin of X(3872) is an open question,” said Wilson. “It appears very close to a threshold, which could be accidental or a key part of the story. This is one thing we will look at very soon."

Professor Christopher Thomas, also from DAMTP, is a member of the Hadron Spectrum Collaboration, and is a co-author on the current studies. Wilson’s contribution was made possible in part by an eight-year fellowship with the Royal Society. ̽��ֱ��research was also supported in part by the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI). Many of the calculations for this study were carried out with the support of the Cambridge Centre for Data Driven Discovery (CSD3) and DiRAC high-performance computing facilities in Cambridge, managed by Cambridge’s Research Computing Services division.

Reference:
David J. Wilson et al. ‘Scalar and Tensor Charmonium Resonances in Coupled-Channel Scattering from Lattice QCD.’ Physical Review Letters (2024). DOI: 10.1103/PhysRevLett.132.241901

David J. Wilson et al. ‘Charmonium xc0 and xc2 resonances in coupled-channel scattering from lattice QCD.’ Physical Review D (2024). DOI: 10.1103/PhysRevD.109.114503

Adapted from a Jefferson Lab story.

An elusive particle that first formed in the hot, dense early universe has puzzled physicists for decades. Following its discovery in 2003, scientists began observing a slew of other strange objects tied to the millionths of a second after the Big Bang.

gremlin via Getty Images

Abstract colourful lines

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 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 – 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

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

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

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

Quantum projects launched to solve universe’s mysteries

sc604 — Wed, 13 Jan 2021 09:00:00 +0000

UK Research and Innovation (UKRI) is supporting seven projects with a £31 million investment to demonstrate how quantum technologies could solve some of the greatest mysteries in fundamental physics. Researchers from the ̽��ֱ�� of Cambridge have been awarded funding on four of the seven projects.

Just as quantum computing promises to revolutionise traditional computing, technologies such as quantum sensors have the potential to radically change our approach to understanding our universe.

̽��ֱ��projects are supported through the Quantum Technologies for Fundamental Physics programme, delivered by the Science and Technology Facilities Council (STFC) and the Engineering and Physical Sciences Research Council (EPSRC) as part of UKRI’s Strategic Priorities Fund. ̽��ֱ��programme is part of the National Quantum Technologies Programme.

AION: A UK Atom Interferometer Observatory and Network has been awarded £7.2 million in funding and will be led by Imperial College London. ̽��ֱ��project will develop and use technology based on quantum interference between atoms to detect ultra-light dark matter and sources of gravitational waves, such as collisions between massive black holes far away in the universe and violent processes in the very early universe. ̽��ֱ��team will design a 10m atom interferometer, preparing the construction of the instrument in Oxford and paving the way for larger-scale future experiments to be located in the UK. Members of the AION consortium will also contribute to MAGIS, a partner experiment in the US.

̽��ֱ��Cambridge team on AION is led by Professor Valerie Gibson and Dr Ulrich Schneider from the Cavendish Laboratory, alongside researchers from the Kavli Institute for Cosmology, the Institute of Astronomy and the Department of Applied Mathematics and Theoretical Physics. Dr Tiffany Harte will co-lead the development of the cold atom transport and final cooling sequences for AION, and Dr Jeremy Mitchell will co-lead the data readout and network capabilities for AION and MAGIS, and undertake data analysis and theoretical interpretation.

“This announcement from STFC to fund the AION project, which alongside some seed funding from the Kavli Foundation, will allow us to target key open questions in fundamental physics and bring new interdisciplinary research to the ̽��ֱ�� for the foreseeable future,” said Gibson.

“Every physical effect, known or unknown, leaves its fingerprint on the phase evolution of a coherent quantum system such as cold atoms; it only requires sufficiently sensitive detectors,” said Schneider. “We are excited to contribute our cold-atom technology to this interdisciplinary endeavour and to develop atom interferometry into a powerful detector for fundamental physics.”

̽��ֱ��Quantum Sensors for the Hidden Sector (QSHS) project, led by the ̽��ֱ�� of Sheffield, has been awarded £4.8 million in funding. ̽��ֱ��project aims to contribute to the search for axions, low-mass ‘hidden’ particles that are candidates to solve the mystery of dark matter. They will develop new quantum measurement technology for inclusion in the US ADMX experiment, which can then be used to search for axions in parts of our galaxy’s dark matter halo that have never been explored before.

“ ̽��ֱ��team will develop new electronic technology to a high level of sophistication and deploy it to search for the lowest-mass particles detected to date,” said Professor Stafford Withington from the Cavendish Laboratory, Co-Investigator and Senior Project Scientist on QSHS. “These particles are predicted to exist theoretically, but have not yet been discovered experimentally. Our ability to probe the particulate nature of the physical world with sensitivities that push at the limits imposed by quantum uncertainty will open up a new frontier in physics.

“This new window will allow physicists to explore the nature of physical reality at the most fundamental level, and it is extremely exciting that the UK will be playing a major international role in this new generation of science.”

Professor Withington is also involved in the Determination of Absolute Neutrino Mass using Quantum Technologies, which will be led by UCL. ̽��ֱ��project aims to harness recent breakthroughs in quantum technologies to solve one of the most important outstanding challenges in particle physics – determining the absolute mass of neutrinos. One of the universe’s most abundant particles neutrinos are a by-product of nuclear fusion within stars, therefore being key to our understanding of the processes within stars and the makeup of the universe. Moreover, knowing the value of the neutrino mass is critical to our understanding of the origin of matter and evolution of the universe. They are poorly understood however, and the researchers aim to develop pioneering new spectroscopy technology capable to precisely measure the mass of this elusive but important particle.

Professor Zoran Hadzibabic has received funding as part of the Quantum Simulators for Fundamental Physics project, led by the ̽��ֱ�� of Nottingham. ̽��ֱ��project aims to develop quantum simulators capable of providing insights into the physics of the very early universe and black holes. ̽��ֱ��goals include simulating aspects of quantum black holes and testing theories of the quantum vacuum that underpin ideas on the origin of the universe.

Researchers will use cutting-edge quantum technologies to transform our understanding of the universe and answer key questions such as the nature of dark matter and black holes.

NASA Goddard Space Flight Center

New Simulation Sheds Light on Spiraling Supermassive Black Holes

Yes

Licence type:

Attribution

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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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’s 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. ̽��ֱ��answer is … maybe.

Baffling bump

̽��ֱ��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). ̽��ֱ��bump appeared at a mass of around 760GeV (the unit of mass and energy used in particle physics – the Higgs boson has a mass of about 125 GeV) but was far too weak a signal to be conclusive on its own. ̽��ֱ��question was, would ATLAS see a similar bump in the same place?

̽��ֱ��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 – 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.

̽��ֱ��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 “dark matter”, 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.

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

A number of theories have been proposed to solve these problems. ̽��ֱ��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’s Cavendish Laboratory and senior member of the ATLAS experiment, told me: “If 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”.

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 – more data is needed to rule this intriguing hint in or out. Parker described the results as “preliminary and inconclusive” but added, “should it turn out to be the first sign of physics beyond the standard model, with hindsight, this will be seen as historic science.”

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, ̽��ֱ�� of Cambridge

This article was originally published on ̽��ֱ��Conversation. Read the original article.

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

Image Editor

̽��ֱ��Large Hadron Collider/ATLAS at CERN

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