Tag Archives: Jim Baggott

What Next for the Higgs Boson? – Jim Baggott

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by the author of Higgs

On 4 July 2012, scientists at CERN announced the discovery of a new elementary particle that they judged to be consistent with the long-sought Higgs boson. The next step is therefore reasonably obvious. Physicists involved in the ATLAS and CMS detector collaborations at CERN’s Large Hadron Collider (LHC) facility will be keen to push ahead and fully characterize the new particle. They will want to know if this is indeed the Higgs boson, the one ingredient missing from the so-called standard model of particle physics.

How will they tell?

Physicists at Fermilab’s Tevatron collider and CERN’s LHC have been searching for the Higgs boson by looking for the tell-tale products of its different predicted decay pathways. The current standard model is used to predict both the rates of production of the Higgs boson in high-energy particle collisions and the rates of its various decay modes. After subtracting the ‘background’ that arises from all the other ways in which the same decay products can be produced, the physicists are left with an excess of events that can be ascribed to Higgs boson decays.

Now that we know the new particle has a mass of between 125-126 billion electron-volts (equivalent to the mass of about 134 protons), both the calculations and the experiments can be focused tightly on this specific mass value.

So far, excess events have been observed for three important decay pathways. These involve the decay of the Higgs boson to two photons (written H → γγ), decay to two Z bosons (H → ZZ → l+l-l+l-, where l signifies leptons, such as electrons and muons and their anti-particles) and decay two W particles (H → W+W- → l+ν l-ν, where ν signifies neutrinos). All these decay pathways involve the production of bosons. This should come as no real surprise, as the Higgs field was originally invented to break the symmetry between the weak and electromagnetic forces, thereby giving mass to the W and Z particles and leaving the photon massless. There is therefore an intimate connection between the Higgs, photons and W and Z particles.

The decay rates to these three pathways are broadly as predicted by the standard model. There is an observed enhancement in the rate of decay to two photons compared to predictions, but this may be the result of statistical fluctuations. Further data on this pathway will determine whether or not there’s a problem (or maybe a clue to some new physics) in this channel.

But the Higgs field is also involved in giving mass to fermions – matter particles, such as electrons and quarks. The Higgs boson is therefore also predicted to decay into fermions, specifically very large massive fermions such as bottom and anti-bottom quarks and tau and anti-tau leptons. Bottom quarks and tau leptons (heavy versions of the electron) are third-generation matter particles with masses respectively of about 4.2 billion electron volts (about four and a half proton masses) and 1.8 billion electron volts (about 1.9 proton masses).

But these decay pathways are a little more problematic. The backgrounds from other processes are more significant and so considerably more data are required to discriminate the background from genuine Higgs decay events. The decay to bottom and anti-bottom quarks was studied at the Tevatron before it was shut down earlier this year. But the collider had insufficient collision energy and luminosity (a measure of the number of collisions that the particle beams can produce) to enable independent discovery of the Higgs boson.

ATLAS physicist Jon Butterworth, who writes a blog for the British newspaper The Guardian, recently gave this assessment:

If and when we see the Higgs decaying in these two [fermion] channels at roughly the predicted rates, I will probably start calling this new boson the Higgs rather than a Higgs. It won’t prove it is exactly the Standard Model Higgs boson of course, and looking for subtle differences will be very interesting. But it will be close enough to justify [calling it] the definite article.

When will this happen? This is hard to judge, but perhaps we will have an answer by the end of this year.

Higgs – Jim Baggott *****

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Whenever someone famous dies or there’s a major royal event you will see a book arrive in the shops with undue haste. It’s hard to imagine it wasn’t thrown together with minimum effort – and with equally minimal quality. So when I saw that Jim Baggott had produced a book on the Higgs boson all of five weeks after the likely detection was announced following several years work by the Large Hadron Collider at CERN, it seemed likely that this too was a botched rush job. But the reality is very different.

In one sense it has to be a rushed job – the announcement was made on 4 July 2012 and the book was out by mid-August, featuring said announcement. So that bit of the book could hardly have had much time for careful editing, bearing in mind publishers usually take at least a couple of months from final versions of the text to having a physical book. (Much of the rest of the book was written well in advance.) But the remarkable trick that Baggott and OUP have pulled off is that the rush doesn’t show. This is an excellent book throughout.

The first, but probably not most important way it’s great is that it provides by far the best explanation of what the Higgs field is and how it is thought to work (and what the Higgs boson has to do with anything) I’ve seen – and that by a long margin. However, for me it’s not so much that, as the way it provides a superb introduction to the development of the standard model of particle physics, our current best guess of what everything’s made of. Again, this is the best I’ve ever read and yet it’s here just as a setting for the Higgs business. It is really well done, and the book deserves a wide readership for that alone, not to mention the way it puts the Higgs into context.

Is it perfect? Well, no. Like every other book I’ve read on the subject it falls down on making the linkage between the mathematics of symmetry and the particle physics comprehensible. That is immensely difficult to do, but ought to be possible. However, as long as you take some of the symmetry stuff on trust, the rest works superbly well.

Congratulations, then, to author and publisher alike. Both in its timing and its content this is a tour de force. Recommended.

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Review by Brian Clegg

Jim Baggott – Four Way Interview

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Jim Baggott is a freelance science writer. He trained as a scientist, completing a doctorate in physical chemistry at Oxford in the early 80s, before embarking on post-doctoral research studies at Oxford and at Stanford University in California. He gave up a tenured lectureship at the University of Reading after five years in order to gain experience in the commercial world. He worked for Shell International Petroleum for 11 years before leaving to establish his own business consultancy and training practice. He writes about science, science history and philosophy in what spare time he can find. His books include Beyond Measure: Modern Physics, Philosophy and the Meaning of Quantum Theory (2003), A Beginners Guide to Reality (2005), Atomic: The First War of Physics and the Secret History of the Atom Bomb (2009), The Quantum Story: A History in 40 Moments (2011) and, most recently, Higgs: The Invention and Discovery of the ‘God Particle’ (2012).

Why science?
I guess I’ve always had an innate, child-like curiosity about the nature of physical reality – matter, force, space, time and the universe. I was influenced in the direction of science by some truly great schoolteachers, and I became a chemist, for the simple reason that my competence in maths wasn’t strong enough for me to contemplate a career as a physicist. That said, my desire to seek explanations for things led me to physical chemistry (or even ‘chemical physics’) and it was with a great sense of pride and pleasure that I did manage to publish some entirely theoretical research papers, full of mathematical equations!

I left academia carrying a very strong desire to maintain my interests in science and, with the conspicuous help of a one-time features editor at New Scientist magazine, I learned a bit about writing popular science. I write principally to learn about a subject that interests me, a process that has been made considerably easier in the last 15 years by the emergence and development of resources on the web.

Why this book?
The idea for this book came to me in the summer of 2010 as I was putting the finishing touches to the manuscript of The Quantum Story. That book sets out a history of quantum physics, told through 40 crucial ‘moments’ or turning-points both in theory and experiment. In March 2010, the Large Hadron Collider at CERN achieved record proton-proton collision energies of seven trillion electron-volts and I figured that if the Higgs boson really did exist (and there were going to be all kinds of trouble if it didn’t), then there was a very good chance that it would be discovered soon. I approached Oxford University Press with a proposal to write a book tracing the history of the so-called standard model of particle physics, placing the ‘invention’ of the Higgs field and the Higgs boson in its proper context, right up to the most recent developments at CERN. The idea was to have the book typeset and ready to go. I continued to update the final chapter through 2011 and early 2012, leaving 1500 words or so to describe the discovery itself. I followed the 4 July announcement live via a CERN webcast, and drafted the final words describing the discovery of ‘something that looks very much like the Higgs boson’ the following day. This was how we were able to publish Higgs so soon after the discovery announcement.

What’s next?
I’ve already submitted the manuscript of my next book, called Farewell to Reality: How Fairy-tale Physics Betrays the Search for Scientific Truth. This will be published in the UK early next year by Constable & Robinson. The book was born out of a growing sense of frustration with the way that a lot of unproven (and arguably unprovable) contemporary theoretical physics is paraded as accepted science in the popular science literature. Farewell to Reality attempts to set the record straight. It provides a hopefully accessible summary of what I call the ‘authorised’ version of reality – quantum theory, the standard model of particle physics, the special and general theories of relativity and the standard model of big bang cosmology – and explains why this version can’t be right or, at least, why it can’t be the whole story. Attempts to fix the problems with this version of reality have given us supersymmetry, superstring/M-theory, various flavours of multiverse theory and the anthropic cosmological principle.

I give reasons why I think that much of this theory should be regarded as metaphysics rather than science. As Einstein once said: ‘Time and again the passion for understanding has led to the illusion that man is able to comprehend the objective world rationally by pure thought without any empirical foundations – in short, by metaphysics.’ The book will be controversial, and I’m really looking forward to its reception.

What’s exciting you at the moment?
We’re still far from the end of the story about the Higgs boson. The evidence gathered by the two detector collaborations at the LHC – ATLAS and CMS – point very clearly to the existence of a new particle with many of the characteristics expected of ‘the’ Higgs boson as demanded by the current standard model. But further data are needed to be sure, and surprises are not impossible. I’m continuing to follow developments as best I can.

In the meantime, I’m mulling over potential topics for my next writing project. I’m intrigued by the possibility of going back to a short period in cold war history leading up to the decision to build the hydrogen bomb. In the United States, cold war nuclear strategy was framed by aspects of game theory. I’m thinking it might be interesting to personalize the different strategies in a prisoner’s dilemma type game using Einstein, Oppenheimer and von Neumann, all of whom were together at the Institute for Advanced Study in Princeton in this period. I’d like to explore these strategies through a sequence of imagined conversations between these three extraordinary intellects. What excites me is the challenge to get this right and make it compelling reading.

Atomic: the first war of physics – Jim Baggott *****

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The best popular science book of the year to date by far (April 2009), this is an epic journey through the development of atomic power and the atom bomb during the second world war.

It’s a seriously chunky tome at nearly 500 pages, but for once this length is justified. It isn’t padded out by repetition and rhetoric, this really is such a big story that it needs this kind of length.

It might seem there really isn’t much of a story left to tell. What with Richard Feynman’s superb reminiscences of the Manhattan Project and many, many books on that first real example of big science, you might be inclined to say ‘what’s new?’ – but Jim Baggott more than pulls it off by covering not one, but four stories of the development of the terrifying power of the atom – in Germany, the US, the UK and the USSR.

He takes us back to the first concept that fission could produce a chain reaction and leads us through the gradually realization in the UK and then the US, that Germany could be building atomic weapons and this posed a huge threat. There’s the dramatic raids on the heavy water plant in Norway, and lying underneath all the developments the growing network of spies, feeding information from the West to Russia. It’s surprising how slow the US was to realize what was going on, and fascinating to see the political machinations across the Atlantic.

That’s not all. We see the two pictures of what was going on in Germany, never totally rationalized. Were Werner Heisenberg and his fellow scientists just not up to the job, but trying hard to give the fatherland a super weapon, or (as they later rationalized), were they intentionally going slow on the development of a bomb? What’s also amazing is how early the idea of deterrence came along – the great Danish physicist Niels Bohr suggesting the idea of the concept of atomic weapons being enough for deterrence well before they were built. Most remarkable of all, the way we nearly had a world organization giving everyone access to atomic power and with no one having nuclear weapons, an idea that came out of the US administration, but was scuppered by the more hawkish wing of the same group of people.

If the book has a weakness, it’s the sheer volume of people involved. I lost track of some of the names and couldn’t really care about many of them. As Baggott switches from location to location, I was sometimes a bit confused about where I was. One chapter, for instance, begins ‘The work of the MAUD committee had proceeded apace through the last few months of 1940.’ I was desperately trying to remember whose committee this was, in which country, and didn’t discover until a couple of paragraphs later. There just is a huge amount of detail, and sometimes you need to let this flow over you and not worry too much about total comprehension.

This is an unparalleled book that should be on the shelf of anyone with an interest in the development of nuclear power, or how the Second World War was won. It really brings home how much this was the war of science. Here we see the nuclear weapons, but there was also the code cracking, particularly the Bletchley Park work, radar and the development of operational research all coming from science and playing their part. I’m not an enthusiast for books on the Second World War, but this one had me enthralled. Highly recommended.

 

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Review by Brian Clegg