Archive for Particle Physics

Ahead of a Four-Day Week…

Posted in Artificial Intelligence, Biographical, Education, mathematics, Maynooth with tags , , , , , , on March 29, 2026 by telescoper

It’s Sunday 29th March – Palm Sunday in fact – and Friday 3rd April is Good Friday, which is followed by a break of a week for Easter, so I’ve been looking at what I have to do in the four days between Monday and Thursday.

On Tuesday afternoon part of my 3rd Year Computational Physics class will be doing a supervised test in the computer lab. I (foolishly) promised to ensure they would get their grades before Easter, so I’m going to have to mark them straight away. This is a larger group than usual because some students who would normally be in the lab on Thursdays swtiched to Tuesday so they could go on a trip to Armagh. Anyway, this is the third lab test and at least I have graded the first two tests for all groups in time for the arrival of the new ones.

There will be one more of these lab tests after the Easter break but after that the students will be working full-time for 3 weeks or so on mini-projects. That is the part they usually enjoy most and I’m very happy to see that some have already started work.

Then, on Wednesday I have the second class test for my 4th year Particle Physics module. This is the second such test, and it will be held during a tutorial session. This is a pen-and-paper test rather than a coding test to be done in the lab. For such tests I allow students to bring whatever they like on paper but phones, laptops and tablets are banned. This is the easiest way I could think of to avoid students using AI to solve the problems. In previous years I gave take-home assignments for this module, and I still hand out exercise sheets to be gone over in tutorials, but these are for formative purposes only. The summative assessments are the class tests. There will be three of those, which means they will have to endure one more after Easter. In a normal week I would have a Particle lecture on Friday, but that won’t happen because it’s Good Friday and my lectures apparently aren’t good enough to happen on that day.

As well as the Computational Physics lab test and the Particle Physics class test, next I have two lectures, both at 9am – one on Tuesday and one on Thursday – and another lab session on Thursday which is not a test, but a practical session about solving ODEs.

Then it will be the Easter Break. After that, according to my calculations, there will be four more teaching weeks before the examination period. The last day of teaching is May 8th. Between that and the examinations there is a gap of a week during which I will have to mark all the completed Computational Physics project reports, as well as giving some revision classes if there is demand for them.

Open Letter about Cuts to UK Theoretical Physics Funding

Posted in Science Politics with tags , , , , , , , , on March 7, 2026 by telescoper

I am remiss in having forgotten until now to circulate an open letter that has been set up to express support for the high energy physics theory and particle theory communities in the United Kingdom. I signed the letter a few days ago but neglected to circulate it for further signature.

The letter reads:

We the undersigned wish to raise serious concerns about the current cuts to UK high energy particle physics theory grants by signing up to the letter below. The open letter and list of signatories are printed on this page. Individuals who wish to support this initiative may add their name as a signatory by completing the form below. This letter will be sent to Lord Patrick Vallance (Minister of State for Science, Innovation, Research and Nuclear), Liz Kendall (Secretary of State for Science, Innovation and Technology), Chi Onwurah MP (Chair of the UK House of Commons Science, Innovation and Technology Select Committee), and Prof. Sir Ian Chapman (CEO of UKRI).

We are signing this letter to raise serious concerns about the proposed cuts to high energy physics theory and particle theory in the United Kingdom. The UK is a world leader in this area: its historical activity led to the development of the Standard Model of particle physics and the ongoing development of string theory. UK theoretical physicists provide essential input to major international experiments, including the Large Hadron Collider at CERN and next-generation programmes in neutrino physics, gravitational waves, and cosmology, enabling rigorous interpretation of data and the extraction of fundamental insight. The strength of the UK community lies in its intellectual breadth and integration: researchers operate across phenomenology, formal theory, and their interface, and sustained dialogue between these areas underpins the UK’s leading role in global collaborations and internationally recognised research groups. In parallel, UK theorists advance the theoretical foundations of fundamental physics.

These groups and scientists can only operate thanks to critical funding by UK research council funding.

The current apparent scale of the cuts to the Particle Physics, Astronomy and Nuclear Physics area (30% to the overall budget) will result, when rising costs are taken into account, in a much greater than 50% cut in the number of postdoctoral researchers active in these areas in the UK. This will have a devastating effect on the ability of the UK to maintain its leading role in the subject.

Such funding decisions will affect the famously excellent reputation of the UK university sector. It will risk the health of UK physics departments and will therefore damage economic growth in the UK. Many scientists trained in this sector subsequently move into senior positions in technical industries such as machine learning and finance. Theorists at universities play a crucial role in the training and development of the inventors and disruptors of the future.

We urge UK politicians and leaders in the UK funding organisations to carefully consider the implications of the current direction of funding decisions before it is too late and irreparable damage is done to the UK theory community.

You can sign the letter and see a list of existing signatories here.

A Quarter Term

Posted in Biographical, Education, mathematics, The Universe and Stuff with tags , , on February 20, 2026 by telescoper
I searched for a free stock image using “quarks” as a search term and found this photo by Anh Nguyen on Pexels.com.

On most Friday afternoons there is a seminar in the Physics Department at Maynooth University, and I got it into my mind that there was one this afternoon and set aside an hour to attend it. It turns out that there isn’t a seminar so I have time to write a quick blog post before I head to Dublin for a concert.

We’ve (almost) reached the end of Week 3 of the Semester which means we’re about a quarter of the way through the term. Yesterday we did the first Lab Test of four in Computational Physics, which went off without any major problems. The first class test in Particle Physics will be next week and I hope that goes equally well.

Today’s the day students officially received their provisional first semester results. When I arrived at my particle physics lecture this morning the students were discussing their exam marks. Most seemed relatively happy, which is good because this is the final year for most of these students so their grades matter more now than in previous years.

This morning’s lecture was quite amusing. I was discussing electrostatic interactions between quarks in nucleons and in the course of that I asked the class to calculate (2/3)×(-1/3) +(-1/3)×(-1/3)+(-1/3)×(2/3). It took a surprisingly long time to arrive at the right answer! To make matters worse, when I announced the correct answer I got the sign wrong*.

It’s been a long week.

Anyway, next week I’ll be starting on the Dirac Equation, and on the basis of today’s events I wonder about the wisdom of having a lecturer who can’t do minus signs teach relativistic quantum mechanics to students who struggle to do simple arithmetic with fractions!

*ANS=-1/3

The Trouble with Teaching Particle Physics…

Posted in Education, The Universe and Stuff with tags , on February 16, 2026 by telescoper

The trouble with teaching particle physics is that students start out thinking that the standard model looks like this

when it’s really more like this

I hope this clarifies the situation.

Can you make a neutral pion from two photons?

Posted in The Universe and Stuff with tags , , , on November 10, 2025 by telescoper

A neutral pion can decay into two photons. It is therefore not unreasonable to ask the question whether the reverse process – the creation of a neutral pion by colliding two photons – is physically possible and, if not, why not? It is perhaps less reasonable to ask an AI bot these questions. One of my colleagues did just that and found it said “no”, giving  the following three answers to the “why not?” question:

I particularly like the second one.

Would anyone like to offer a correct answer through the comments box?

Ireland in CERN!

Posted in Science Politics, The Universe and Stuff with tags , , , , , , , , on October 22, 2025 by telescoper
Photo by Pietro Battistoni on Pexels.com

I saw the news today that the Republic of Ireland is now officially an associate member state of the Conseil Européen pour la Recherche Nucléaire, better known as CERN. This has been in the pipeline for a while: I blogged about it here, for example. But today’s the day that Ireland formally joined.

I think this is a very good move for Irish physics, and indeed for Ireland generally. I will, however, repeat a worry that I have expressed previously. There is an important point about CERN membership, however, which I hope is not sidelined. The case for joining CERN made at political levels was largely about the return in terms of the potential in contracts to technology companies based in Ireland from instrumentation and other infrastructure investments. This was also the case for Ireland’s membership of the European Southern Observatory (ESO), which Ireland joined 7 years ago. The same thing is true for involvement in the European Space Agency, which Ireland joined in 1975. These benefits are of course real and valuable and it is entirely right that arguments should involve them.

Looking at CERN membership from a purely scientific point of view, however, the return to Ireland will be negligible unless there is a funding to support scientific exploitation of the facility. That would include funding for academic staff time, and for postgraduate and postdoctoral researchers to build up an active community as well as, e.g., computing facilities. This need not be expensive even relative to the modest cost of associate membership (approximately  €1.9M). I would estimate a figure of around half that would be needed to support CERN-based science. I am given to understand that some funds have been made available as part of the joining arrangements, but I don’t know the details.

As I have mentioned before, Ireland’s membership of ESO provides a cautionary tale. The Irish astronomical community was very happy about the decision to join ESO, but that decision was not accompanied by significant funding to exploit the telescopes. Few astronomers have therefore been able to benefit from ESO membership. While there are other benefits of course, the return to science has been extremely limited. The phrase “to spoil a ship for a ha’porth of tar” springs to mind.

Although Ireland joined ESA almost fifty years ago, the same issue applies there. ESA member countries pay into a mandatory science programme which includes, for example, Euclid. However, the Irish Government did not put any resources on the table to allow full participation in the Euclid Consortium. There is Irish involvement in other ESA projects (such as JWST) but this is somewhat piecemeal. There is no funding programme in Ireland dedicated to the scientific exploitation of ESA projects.

Under current arrangements the best bet in Ireland for funding for ESA, ESO or CERN exploitation is via the European Research Council, but to get a grant from that one has to compete with much better developed communities in those areas.

The recent merger of Science Foundation Ireland and the Irish Research Council to form a single entity called Research Ireland could provide an opportunity to correct this shortfall in funding for science exploitation. The reorganization won’t do anything on its own, however: the overall level of public sector research funding will have to increase dramatically from its current level, well below the OECD average. The recent Budget in Ireland for 2026 does include an allocation of €426 million for research under the National Development Plan, but how much of this will find its way into basic research generally and CERN science in particular?

The magnetic moment of the muon revisited

Posted in The Universe and Stuff with tags , , , , on June 10, 2025 by telescoper

A couple of years ago I posted an item about a measurement of the anomalous magnetic moment of the muon, a quantity usually known as (g-2). At the time this appeared to be in conflict with the predictions of the standard model (SM)of particle physics but the general opinion among experts was that the problem was likely to lie with the calculations rather than the experiment.

Well, catching up on things I missed during examination marking season, I refer you to a substantial paper (188 pages long) that appeared on arXiv on 27th May 2025, with the abstract:

If this is too small to read I direct yourself to the salient point, namely that “there is no tension between the SM and experiment at the current level of precision”.

It seems the Standard Model survives to fight another day…

Last Remarks

Posted in Biographical, Education, Euclid, Maynooth, The Universe and Stuff, Uncategorized with tags , , on May 11, 2025 by telescoper

On Friday (9th May), the last day of undergraduate teaching at Maynooth, I gave the last lecture in my module on Particle Physics. I actually finished the syllabus on Tuesday (6th) so the final one was more a revision class than a lecture. I used it to go through some past examination questions and (try to) answer some general points raised by the class.

What surprised me about this lecture was that, as has usually been the case, there was more-or-less a full attendance. Examinations in Maynooth start on Friday (May 16th), but the Particle Physics examination is not until May 27th, near the end of the examination period. I therefore expected that many students would be concentrating on their revision for their other modules, which have exams earlier in the season or finishing their projects (which are due in before the exams start). There were one or two absences, but most came anyway. In fact there was even an extra student, one of our MSc students. When I saw him at the back of the lecture hall I asked, jokingly, why he had come. He replied “I haven’t got anything better to do”. I wasn’t sure how to interpret that!

That lecture was at 11am. Later that day, at 3pm, I gave a Departmental colloquium (which had quite a big audience). The title was Euclid: The Story So Far and the abstract was

The European Space Agency’s Euclid satellite was launched on 1st July 2023 and, after instrument calibration and performance verification, the main cosmological survey is now well under way. In this talk I will explain the main science goals of Euclid, give a brief summary of progress so far, showcase some of the science results already obtained, and set out the time line for future developments, including the main data releases and cosmological analysis.

The audience for these talks is very mixed: experimental and theoretical physics staff, postgraduates and even some undergraduate students (including some who were in my lecture earlier) so it was quite a general talk rather than one I might give to an specialist astrophysics audience. If you’re interested you can find the slides here.

Having a quick cup of tea after the end of the talk and before I headed off to catch the train, I talked briefly with a student who is taking his final examinations at Maynooth this year. He told me that I had actually given the first lecture he attended when he had just started his first year and the colloquium was the last talk he would attend at Maynooth. That would be the case for quite a few students in the audience, I suppose, but it won’t be true for any in future: I am no longer teaching any modules taken by first year students, and I’ll be retired when the current first year students graduate…

Beautiful Equations

Posted in Biographical, mathematics, The Universe and Stuff with tags , , , , on February 25, 2025 by telescoper

I did a lecture today about the Dirac Equation (which is almost 100 years old, having been first presented in 1928). You might think this is a difficult topic to lecture on, but it’s really a piece of cake:

This reminds me that a a while ago I posted about an interesting article on the BBC website that discussed the way mathematicians’ brains appear to perceive “beauty”. A (slightly) more technical version of the story can be found here. According to functional magnetic resonance imaging studies, it seems that beautiful equations excite the same sort of brain activity as beautiful music or art.

The question of why we think equations are beautiful is one that has come up a number of times on this blog. I suspect the answer is a slightly different one for theoretical physicists compared with pure mathematicians. Anyway, I thought it might be fun to invite people offer suggestions through the comments box as to the most beautiful equation along with a brief description of why.

I should set the ball rolling myself, and I will do so with the Dirac Equation:

dirac_equation

This equation is certainly the most beautiful thing I’ve ever come across in theoretical physics, though I don’t find it easy to articulate precisely why. I think it’s partly because it is such a wonderfully compact fusion of two historic achievements in physics – special relativity and quantum mechanics – but also partly because of the great leaps of the imagination that were needed along the journey to derive it and my consequent admiration for the intellectual struggle involved. I feel it is therefore as much an emotional response to the achievement of another human being – such as one feels when hearing great music or looking at great art – as it is a rational response to the mathematical structure involved. But it’s not just that, of course. The Dirac Equation paved the way to many further developments in particle physics. It seems to encapsulate so much about the behaviour of elementary particles in so few symbols. Some of its beauty derives from its compactness- it uses up less chalk in a mathematical physics lecture.

Anyway, feel free to suggest formulae or equations, preferably with a brief explanation of why you think they’re so beautiful.

P.S. Paul Dirac was my (academic) great-grandfather.

Particle Physics Masterclass at Maynooth

Posted in Education, Maynooth, The Universe and Stuff with tags , , on February 23, 2025 by telescoper

Last week’s announcement about Ireland joining CERN reminded me that I should have advertised the annual Particle Physics Masterclass at Maynooth University long before now, not least because I’m actually teaching particle physics this year. My only excuse is that I’m old and forgetful. Anyway, better late than never; there’s still almost a week until the registration closes.

Since 2012 the Department of Theoretical Physics hosted the International Particle Physics Masterclasses for secondary school students each spring (except for 2020 when it was cancelled due to Covid-19 restrictions).  Now the Department of Theoretical Physics is no more, having been incorporated last year into the Department of Physics, but the Particle Physics Masterclasses continue; the next event will be on Tuesday 18 March 2025.

These Masterclasses give secondary school students the opportunity to discover the world of quarks and leptons for themselves, by performing measurements on real data from CERN, meeting active particle physics researchers and linking up with like-minded students from other countries.  We will join thousands of other secondary school students at more than 100 universities and laboratories around Europe and worldwide in a programme stretching over four weeks.

Physics at the most fundamental level – the smallest and most basic building blocks of matter – is an exotic world.  But a few introductory talks and working with data from CERN will give the students insight into the fundamental particles of matter and the forces between them, as well as what went on during the Big Bang.

In the morning the students are introduced to particle physics, experiments and detectors in lectures given by active particle physics researchers.  After an early lunch, they work on their own with data from the ALICE detector at CERN. Afterwards they participate in a video conference with students from other countries and moderators at CERN, where they discuss and compare their results.  For more information on the masterclasses, see the International Masterclasses web site.

You can find more information about the event here and you can register here. Hurry up though as the deadline for registration is the end of this month, i.e. this Friday, February 28th!