Monday, 19 January 2015

Good luck, Cameron

Since late 2010 I've had the privilege of working with a very good research student, Cameron Cuthbert, on “hidden-beauty” states at the Large Hadron Collider. A journal paper based on our work, “Search for the Xb and other hidden-beauty states in the π+ π Υ(1S) channel at ATLAS”, was published late last year.

After six years with the ATLAS experiment, in a variety of roles — most recently as a research assistant here at the University of Sydney — Dr Cuthbert has decided to call it a day. This morning, he begins his new career as a quant.

Good luck, Cameron. You'll be missed.

Friday, 21 November 2014

On PM: New baryons at LHCb

The LHCb experiment at CERN has observed two new baryons — particles like the protons and neutrons that form the nuclei of normal matter — in data from the 2011-2012 run of the Large Hadron Collider. These particular baryons are called “cascade b”: they are dominated by the heavy b or “beauty” quark, and so are about 6 times heavier than a proton; they also contain a strange quark, and a down quark. The lightest cascade-b has been known for some time, but two related particles at slightly higher masses were expected based on very general quark-model arguments. It's these related particles that have just been seen.

I was interviewed briefly on ABC's PM program yeterday, to cover this discovery, and LHC-related news more generally. A technical account of the work can be found in the paper LHCb submitted to Phys. Rev. Lett., which is available on the arXiv.

(What I've written simplifies things considerably: for example, these cascade-b's are negatively charged; there's also a matching set of neutral cascade-b's, each with an up quark in place of the down. And why are there three related states close in mass? As well as being an empirical observation, such patterns can be understood by considering the possible ways to combine quarks with various flavours and spins, taking into account the symmetry of the resulting wavefunction in each case. Readers with a considerable amount of university physics should be able to follow the PDG's discussion of the charmed baryons: baryons carrying one unit of “beauty” are an analogous case.)

Wednesday, 19 November 2014

This may come as a surprise

Cosmic evolution may teach us how the good and the evil tendencies of man may have come about; but, in itself, it is incompetent to furnish any better reason why what we call good is preferable to what we call evil than we had before.
As a claim about the limits of natural history, this is conventional enough. But the author may come as a surprise: Thomas Henry Huxley, in the second Romanes lecture, in Oxford, 1893. H/T Gertrude Himmelfarb, “Evolution and Ethics, Revisited,” The New Atlantis, Number 42, Spring 2014, pp. 81–87.

Tuesday, 14 January 2014

Douthat on New Atheists and Noble Lies

The Times' junior resident conservative, Ross Douthat, can be infuriatingly uneven — sometimes clear-eyed, sometimes self-serving, and sometimes both in the space of a single sentence. But at his best he is a blast of very fresh air: forthright, rigorous, and reasonably open to differences on fundamentals. His current blog post reminds me of why I persevere with him.

Friday, 19 April 2013

Monday, 6 August 2012

Three Cheers for Curiosity

NASA's Mars Science Laboratory rover, “Curiosity”, has safely landed on the surface of the Red Planet after what sounded like a trouble-free descent.

Given what was required to get from the top to the bottom of the atmosphere in one piece, it's a great relief.

Congratulations guys. Now we can all get back to work!

Sunday, 3 June 2012

Physics, faith, and a cartoon

I was interviewed on physics and faith six weeks ago as part of the Melbourne City Bible Forum's Reason for Faith Festival — a kind of pendant to the Global Atheist Convention that was held in the same town the week before.

The mp3 of the interview is now available on the Melbourne CBF website.

The event was called “The Faith of a Physicist”, but we talked more about physics as such, in particular my own field (particle physics), and what it's like to be a physicist ... only then drawing the connections with my being a Christian, and having a degree in theology. So the talk is not itself a confession of faith. (There was some of that later in the day, but that's another story.) We covered a lot of good, scientific ground partly because the interviewer was my old friend Tim Patrick: a priest in the Anglican Diocese of Melbourne, but by training a geologist, with research experience in the field and the lab. After talking about physics itself we talked about its limits:

People ask ... what the limits of physics are. I don't know what the limits of physics are. I can tell you what the limits of my current experiments are, within a limited time horizon, but not really beyond that ... The questions that you can answer with physics are surprising if you don't have the scientific knowledge yourself, if that makes sense: you need to understand the field to have a sense for what the reach of the field is, and someone outside the field — you can't legislate it. Not just because it's an open enquiry, but because it's non-trivial: there's more things in heaven and earth than are dreamt of in my or your philosophy, and certainly in the philosophy of someone like you or me a hundred years ago. So you just have to run with it.
We also covered the difficulty of interdisciplinary work, what the sciences and theology tell us about each other, a bit of 19th-century scientific history, the difference between scientific and cultural questions, ...

There were questions from the floor at the end of the interview, which for some reason have not made it onto the mp3 ... although my answers have. So that the answers might make more sense, I've done what I can to reconstruct the questions:

  • at 28:22, the question was about divine action: what God's providence in natural (biological) history looks like physically, e.g. do I think God fiddles with DNA, or ...?
  • at 29:58, a question about cosmology: what was happening before the Big Bang?
  • at 31:06, a time-honoured question about the Second Law of Thermodynamics, and how it relates to the development of complexity in biology;
  • at 33:21, are physicists mostly unbelievers?
  • at 33:36, are metaphysical or religious motivations important in cosmology? in physics more generally? for me?
  • at 35:31, are ideas about a “multiverse” well-grounded?
At one point, I drew an analogy with chemistry's Periodic Table: how the LHC experiments are looking for missing bits of the “periodic table” of particle physics. A few weeks later, Jorge Chan's PhD Comics posted an eight-minute movie The Higgs Boson Explained, which has an excellent discussion of particle physics in these terms, with a mix of live action, and cartoons being drawn on the fly. Thoroughly recommended.

Monday, 22 August 2011

Praise, patriotism, partisanship, and pop

The NYT this weekend includes a glowing memoir on the Franciscan Sisters of Mary, on the occasion of Sister Mary Jean Ryan's retirement as chief executive of one of of one of America’s largest networks of Catholic hospitals. The discussion includes their clear-eyed planning for the day (soon to arrive) when the order no longer exists. A friend and I were discussing this sort of thing recently: the difference in organisation and sensibility that allows Catholic groups to be distinctively themselves, while allowing for other ways of being faithfully Christian — something that contemporary Evangelical groups struggle with. There is still a lively tradition of openness in the pews, even in these identity-mongering times, but within the leadership?

A fan of the US military writes in criticism of “support our troops” pieties:
The irony is that our soldiers are the last people who are likely to call themselves heroes and are apparently very uncomfortable with this kind of talk. The military understands itself as a group endeavor. As the West Point professor Elizabeth D. Samet recently noted, service members feel uneasy when strangers approach them to — as the well-meaning but oddly impersonal ritual goes — thank them for their service, thereby turning them into paradoxically anonymous celebrities. It was wrong to demonize our service members in Vietnam; to canonize them now is wrong as well. Both distortions make us forget that what they are are human beings...
The change of tone in the coverage and discussion of Anzac Day, noticeable to anyone over a certain age, springs to mind as an Australian analogue, although the causes may be somewhat different.

An American radio host and author compares contemporary political debate to an auto-immune disease.

And my current nostalgia trip: Glycerine, the greatest hit of the band Bush. I have recently returned to an apartment complex where I was staying in late 1995, through 1996, and this song has been on my mind. Like many pop songs, it would not withstand too close an enquiry into the literal meaning of its lyrics, but as the distillation of a particular mood — masculine yearning, chastened by regret — it is superb. And in contrast to the posturing, braggarty tone of the songs in a male voice that followed it, it is unashamedly pretty. A female cover brings that out, although I do miss the surface roughness of the original:
I could have been easier on you,
I couldn't change though I wanted to.

Thursday, 18 August 2011

Getting past the giggle factor

$500,000 as seed-funding for interstellar travel — not for a starship, but for a long-term programme “to begin studying what it would take — organizationally, technically, sociologically and ethically”. DARPA and NASA are behind this, but the work itself, and the carriage of the issue (and the financing) is meant to be done by others for the time being, which is to say, for a very long time.

I'm quite impressed by this:

(1) This is the sort of long-distance thinking and investment that public institutions should sponsor, but the sponsorship that's foreseen here is modest and one-off: this money, together with some meetings to organise and incubate discussion among those interested, and amongst contenders for the funds. It seems as though they have got the level of public involvement right.

(2) They understand that one of the issues is to get past `“the giggle factor” associated with the subject'.

(3) The organisation, sociology, and ethics of the task is explicitly part of the agenda of study.

(4) They understand that we do not yet understand what the question is:
Then again, nobody is smart enough now to know what could come of the starship effort, Mr. Neyland pointed out. It would be naïve to think we even know the right questions to ask.

“If you had asked Einstein and Marconi in 1910 to define a worldwide communication system for the common man,” Mr. Neyland asked, “would he have come up with the iPhone?”

Tuesday, 20 July 2010

xkcd and Mister Rogers

Much as I enjoy xkcd like any other nerd, I sometimes find Randall Munroe's sense of humour grating: self-satisfied, snarky, and (especially in sexual matters) boastful and oversharing. (This latest part may well be pure wish-fulfilment on his part: I'm ignorant of his real-world life.)

But just to keep me on my toes, here is his tribute to Fred Rogers, a mainstay of American children's television, of whom I was previously ignorant. It is hard to imagine someone with a more different sensibility.

The NYT's 2003 obituary for Fred Rogers offers more information.

Wednesday, 30 June 2010

On StarStuff today: Matter and antimatter

You can hear me in the current issue of ABC's online StarStuff program, talking about recent results from the MiniBooNE and MINOS experiments at the Fermi National Accelerator Laboratory ("Fermilab") outside Chicago. Our segment starts about ten minutes into the program. [A ?permanent? link to the MP3 can be found here: starstuff20100630.mp3; the file is 15MB.]

Both experiments have presented preliminary results that hint at differences between matter and antimatter — specifically, kinds of differences that should not occur on our current understanding. And so there has been a certain amount of fuss.

Unlike the work mentioned in the previous post, which concerned mesons, the new results are from experiments on those most fascinating and frustrating of elementary particles, neutrinos. Complicating the interpretation is that there are anomalies in earlier MiniBooNE data which are still not understood.

If you're after a written version of the story, there is an article at

Thursday, 17 June 2010

Coming up for air

I guess it's kind of obvious that I've been preoccupied in the last six months. One of my preoccupations has now reached its conclusion: our most recent major paper on CP violation has just been published in Physical Review D. (A publicly accessible version can be found on the physics preprint server:
arXiv:1003.3360 [hep-ex].) The short version is that CP violation is important in answering the question "how is it possible for you to be here?". (Note that I didn't say that the question was "why are you here?". A lot hangs on that distinction.)

I discussed some of the issues briefly in a previous post on the 2008 Nobel Prize in Physics.

More on other things soon.