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 X_b 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.

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.)

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.

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 PhysOrg.com.

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.

God in the Telegraph

There's a short piece by me in today's Daily Telegraph, on the Higgs Boson, God, science, and religion. Quite a lot to squeeze into 500 words. It's accompanied by a longer piece by George, Cardinal Pell, which I thought rather good: forthright, thorough, and reasonable (albeit uncompromising).

These mini-essays appear as part of a series on religious matters that the Telegraph is running for four days this week.

(For the record, for those who have read my bio in the print version: “top physicist” is a bit strong; and yes I work at the Large Hadron Collider, specifically on the experiment called ATLAS, but I have not played a key role there. The experiment where I've arguably played a key role is called Belle, at the KEK laboratory in Japan.)

UPDATE: The two other pieces (not three, as originally stated) were also double-headers:

Rabbi Raymond Apple and Sheik Hersi Hilole

Prof. Brian Schmidt and Archbishop Peter Jensen

I thought them all reasonable presentations of their respective positions, and reasonable in other ways. I also felt that there was some disparity of standing between these gentlemen and myself.

Redheads, bugs, the LHC, and all that

In praise of the spleen
On the pain of being a redhead
Olivia Judson on your microbial fellow-travellers
xkcd on intercepting asteroids heading towards Earth

Newspapers have gone pleasingly quiet on the Large Hadron Collider, since the run plan was announced earlier this month. It beat the pessimistic, “if at all” tone of reporting just three days earlier. Given previous loud public statements about scheduling, one could argue that we only have ourselves to blame — but it's pretty hard to take some of the free commentary, such as this piece of farfetching on the connection between the LHC and an abandoned Mayan temple. Really. “And like Xunantunich, the collider these days is silent, if not abandoned,” we are told. Stephen Weinberg's response as quoted in the article, “I don’t see it in quite those apocalyptic terms,” is a marvel of understatement.

Meanwhile, yet another tendentious proposal for peace between science and religion has been launched. It is not noted for its theological insight. “Most scientists and most religious believers refuse to be drafted into the fight,” the writer says. Speaking as a scientist and a Christian, I also refuse to be drafted into this sort of attempt at peacekeeping. One problem with peacekeeping forces is that they can have their own agendas; and they are prone to being tone-deaf.

Finally, a chef writes on making “organic” and other small farms more robust against disease:

Healthy, natural systems abhor uniformity — just as a healthy society does. We need, then, to look to a system of food and agriculture that values and mimics natural diversity. The five-acre monoculture of tomato plants next door might be local, but it’s really no different from the 200-acre one across the country: both have sacrificed the ecological insurance that comes with biodiversity.

What does the resilient farm of the future look like? I saw it the other day. The farmer was growing 30 or so different crops, with several varieties of the same vegetable. Some were heirloom varieties, many weren’t. He showed me where he had pulled out his late blight-infected tomato plants and replaced them with beans and an extra crop of Brussels sprouts for the fall. He won’t make the same profit as he would have from the tomato harvest, but he wasn’t complaining, either...

Updike on neutrinos

In memory of John Updike, who died yesterday (see the obituary and an appraisal in the New York Times) here is his famous, and for the most part accurate, poem on that most fascinating of fundamental particles:

Neutrinos, they are very small.
They have no charge and have no mass
And do not interact at all.
The earth is just a silly ball
To them, through which they simply pass,
Like dustmaids through a drafty hall
Or photons through a sheet of glass.
They snub the most exquisite gas,
Ignore the most substantial wall,
Cold-shoulder steel and sounding brass,
Insult the stallion in his stall,
And scorning barriers of class,
Infiltrate you and me! Like tall
And painless guillotines, they fall
Down through our heads into the grass.
At night, they enter at Nepal
And pierce the lover and his lass
From underneath the bed---you call
It wonderful; I call it crass.

“Cosmic Gall”, from Telephone Poles and Other Poems, John Updike, Knopf, 1960.

For me, it's the comparison to “photons through a sheet of glass” that really sells the poem. (This may be more of a physicist's than a literary critic's remark, but bear with me.) Neutrinos' behaviour --- almost never interacting --- seems unaccountably strange, but suddenly the reference to light jolts you as you think, hang on, I already know that light goes straight through glass, which is also solid, and come to think of it that is peculiar too. It's a remarkable effect: neutrinos suddenly become more accountable, and an everyday phenomenon becomes more noteworthy and distinct.

OK, so in terms of his achievement as a writer, it's not up there with the four “Rabbit” novels. But when it comes to making particle physics accessible, I'll take all the help I can get.

The Green Baize Table Conspiracy

The insanely overdue writeup of my review talk, Quantum entanglement at the psi(3770) and Upsilon(4S), is now on the arXiv public preprint server, and will be included in the proceedings of the Flavor Physics and CP Violation conference. I was asked to give the review because of my involvement in a test of quantum mechanics by the Belle experiment: I wrote about this last year in the post Tangled up in (quantum) blue.

When I have spoken on these results, the most popular part of the talk has always been my explanation (included in the writeup) of an important counter-example, in the form of a conspiracy theory involving the Cigarette-Smoking Man. It seems that more physicists watch the X-Files than would generally admit to it.

The burden of the counter-example is that, if one is willing to countenance bizarre and conspiratorial alternative theories, the sort of study we did at Belle doesn't establish the quantum mechanical result it's trying to test. So we just do the best we can. However there are optical experiments that are immune to (at least this type of) conspiracy-theory explanation. This is the really remarkable thing, and why Bell inequality tests are considered such a big deal in physics. Based on such experiments, we conclude that the weirdness of quantum mechanics is a real feature of the world --- independent of whether quantum mechanics itself is ultimately correct. We might one day learn more, and go beyond the understanding we have from QM, but even so we'd be stuck with the fact that two objects "separated" in space, even many kilometres apart, can be (in a sense) inseparable, forming a single object, a single system. A whole, rather than two parts.

Keep your eyes on the Prize

I guess you-all have noticed that the 2008 Nobel Prize for Physics has been announced, and once again it's gone to a bunch of guys for work in particle physics: Yoichiro Nambu, Makoto Kobayashi, and Toshihide Maskawa. No complaints from me.

The results of my own experiment, Belle, have been instrumental in vindicating this work, particularly that of Kobayashi and Maskawa. We mention them daily, and not just because the experiment is based in Japan; the situation is the same on the other side of the Pacific, at the friendly-rival experiment BaBar at Stanford.

These gentlemen's work concerns spontaneously broken symmetries: the universally used example is balancing a pencil on its point. This situation is symmetric, but unstable. The stable configuration --- the configuration with lowest energy --- has the pencil dropping flat onto the table, picking out one direction at random over all the other possible directions it could equally well have chosen. The phenomenon is quite common in physics: the achievement of Nambu was to apply this to particle physics, in particular the strong interaction that binds the quarks, the atomic nucleus, and so on; the achievement of Kobayashi and Maskawa was to further explain the breaking of the "CP" symmetry, and in the process predict the existence of six types of quark. At the time they wrote their paper, three types were known, and the other three were found, one after the other, over the next twenty-two years. We set great store by this sort of bold predictive power. The final, spectacular confirmation of Kobayashi and Maskawa's work was the observation of CP violation in the B-meson system by Belle and BaBar in 2000-2002, with precisely the value expected on their model. At which point the entire field cried "Respect!", looked at their watches, and started counting down to the inevitable award of the Nobel. The real award, of course, had already been given in full.

[The Italian physicist Nicola Cabibbo has been left out of the party by the Swedish Academy. It was Cabibbo who first established the idea of "mixing" between types of quarks (in his case, "down" and "strange") that was then extended by Kobayashi and Maskawa. Including him would have spoiled the symmetry-breaking focus, but still: his friends have grounds to be disappointed on his behalf.]

There are various discussions, aimed at both the public and the press, at the Nobel Prize site; there's also a longer and rather Nobel-Prize-obsessed technical account by the Academy [warning! physics background required!] on the physics involved. As usual, there is also an accessible report in the New York Times science pages.

Why should you care? Well, CP violation is one of Sakharov's three necessary elements to explain how the universe can have lots more matter than antimatter: why the place is full of stuff, rather than the stuff (the matter and antimatter) having all just annihilated away to leave radiation alone. Why, in other words, it's possible for you to be here.

First beam at the LHC

This afternoon, CERN will attempt to circulate a proton beam in the Large Hadron Collider for the first time, and it's turning into quite a big public event. For further information see

• the news item on the website of the Sydney Uni particle physics group, where I work;
  
• a roundup of comments from Australian physicists at the Australian Science Media Centre; and
  
• the earlier announcement by CERN.
  

The event will be covered live in a webcast. The public lecture at Sydney Uni tonight, by my colleague Kevin Varvell and the science communicator Karl Kruszelnicki, has unfortunately (or fortunately!) already sold out.

UPDATE: We got beam all the way (27 km) around the ring. It went quite smoothly, and everyone is pretty stoked. Concerning the potential of the machine, as usual, the report in the New York Times puts it well: speaking about the new physics we hope to see, they write

those discoveries are in the future. If the new collider is a car, then what physicists did today was turn on an engine, that will now sit and warm up for a couple of months before anybody drives it anywhere. The first meaningful collisions, at an energy of 5 trillion electron volts, will not happen until late fall,

meaning of course the Southern Hemisphere's spring. Serious physics running will then follow in 2009.

As for the public lecture in Sydney, I thought Kevin and Karl did a very good job. One drawback, although nothing to do with the physics: it was standing room only at the Footbridge Theatre, and they were turning people away, including folk who'd RSVP'd as they were asked to do. Not good. We can only apologise for it: events have overtaken us and we've been overwhelmed by the interest people have shown. Sorry to those who missed out.

Hidden charm in South Carolina

This last week I've been enjoying the hospitality of the University of South Carolina, where the The Eighth International Conference on Hyperons, Charm and Beauty Hadrons, a.k.a. "BEACH 2008", has just concluded. I presented an invited review of the new "hidden charm" states, focussing on results from my experiment, Belle: we have taken the lead in finding, and trying to characterise, a number of these new mesons, so called because they have both a charm quark and charm antiquark in their makeup, and thus have no charm (!) overall. Some of these particles just don't fit. Known mesons are built from a quark and an antiquark, and this structure gives rise to certain expected properties, different from those of the new states. So, we believe, these particles are put together in some other way.

The slides from my talk can be found here. The key result comes at the end: we see evidence for two more hidden-charm states that carry electric charge, something it's impossible for a conventional charm-anticharm meson (a "charmonium" state) to do. We found evidence for the first such state last year: this article from CERN Courier gives a brief description. Our paper on the latest results, which we'll submit to the Physical Review soon, can be found at arXiv:0806.4098 [hep-ex].

The early slides of my talk cover a quite different topic: charm mixing, previously mentioned on this blog. There's an historical and personal reason for this. I was supposed to present a review of mixing at the seventh BEACH meeting in Lancaster two years ago, but got very unpleasantly sick after a visit to Beijing, and ended up stuck in a hospital bed "back home" in Japan. (The glamour of international work and travel can be over-stated.) So it felt only right to include a brief update, in lieu of the review I couldn't give in '06. And it was nice to actually make it this time.

Mongolia via Taiwan, with assistance from Iran and Poland

I've recently been in Taipei for the Flavor Physics and CP Violation conference, the highlight of which was the ominously named "cultural activity" ... a trip to a local auditorium to hear the Mongolian singer Urna perform together with the Chemirani Trio on zarb drums (and other percussion), and the wonderful Jerzy Bawol. (I will never say a bad word about the accordian again, I swear it.)

This was splendidly accessible, serious, light-hearted, joyful music, without a trace of irony. Terrific stuff. There are samples on the Urna website I linked, but sadly none from the particular collaboration that I saw on the 6th.

It's somehow appropriate that one could find so impeccably international a collaboration in a place that does not even belong to the United Nations ...

[The slides of my presentation at FPCP, a review of "Quantum entanglement at the ψ(3770) and Υ(4S)", can be downloaded from the conference site. Regular readers of this blog may recognise the principal result, which was previously remarked under "Tangled up in (quantum) blue". Particle physicists (and some other physicists) should have no trouble with the slides, but I guess they'll be somewhat heavy going for anyone else. The writeup for the conference proceedings will, I hope, be a bit more accessible. I will link it here when it's done.]

UPDATE (13th Oct 2008): The writeup of my talk is now available on the arXiv server. I discuss it in a new post on this blog.

The NYT deep-sixes Ice Nine

In recent days my friends --- including several physicists --- have been tormenting me with the news about the court case in Hawaii attempting to stop the turn-on of the Large Hadron Collider at CERN. I would like to think that I have a sense of humour about my work, but I do not have a sense of humour about relentless focus on the spectacular (as opposed to the central, or the important); nor do I have much time for the current conviction that crackpots and obsessives, for some mysterious reason, deserve to be given cultural space.

Ahem.

I was pleased to see an editorial in the New York Times today, dismissing the concern while having fun with it at the same time. I may not have a sense of humour in this matter, but at least I can appreciate it in other people.

[I have previously posted on the LHC, and on the ATLAS experiment, which I am joining this year.]

If the facts do not conform to the theory ...

... what do you do?

Over the last five years or so there has been a test case for this in particle physics, where experimental results and the expectation from theory were completely at odds: qualitatively different, and (where they could be compared numerically) out by a factor of ten or more.

My review of the experimental situation, Double ccbar production in e+e- annihilations at high energy, is now available on the web as arXiv:0712.3138 [hep-ex]. If you want the short version: theory fought experiment, and experiment won. In principle this always happens, but the trick is to get it to work out in practice. And the short version is of course prejudicial: it was always possible that something had been neglected in the analysis (there were some ingenious suggestions), or that some mistake had been made. The rhetoric about a theory being thrown out the moment you see a piece of contrary data sounds unlikely --- or just plain wrong --- and indeed it is. If you want to get a feel for how this sort of thing really plays out, at least in my field, read on. I can't claim that it'll be accessible unless you have some particle physics, however.

(This paper is the long-overdue writeup of a review I presented at the International Workshop on Charm Physics, a meeting I helped organise at Cornell in August. I posted earlier concerning the future of charm physics, the panel discussion that closed the workshop.)

The future of charm physics

It was my privilege, back in August, to chair the panel discussion that closed the International Workshop on Charm Physics at Cornell University.

My writeup for the conference proceedings, The future of charm physics: a discussion, is available on the web as arXiv:0711.1636 [hep-ex].

Tangled up in (quantum) blue

An object goes "bang" in the middle of a room and two pieces go flying off, one to the left and one to the right. Each one follows the laws of physics just by itself, and is influenced only by things that touch it (and gravity etc.^[1]). To know what the left piece will do, you needn't bother about the right piece in any special way: no more than you'd bother about the influence of your shoes, the ceiling, or the planet Jupiter.

Sorry: not true, so far as we understand.

If you believe quantum mechanics, those two pieces are in a certain sense still a single object ... even if the two pieces are on opposite sides of the room, or in separate towns many kilometres apart. It's called entanglement, a.k.a. "spooky action at a distance", a.k.a. "weird quantum s***".

I mention this because our paper on quantum entanglement at the Belle experiment has been published in Physical Review Letters.^[2] The theory does just fine at predicting our data --- that's not unexpected, since it's done just fine on all the data it's been confronted with. The real interest in this kind of measurement is to see if one can go beyond testing quantum predictions, and test entanglement itself: to show that entanglement is just-a-fact-about-how-the-world-is-put-together which we'll always be stuck with, even if we eventually improve on quantum mechanics in some way.^[3]

The gold standard for proving entanglement is a theorem by the late John Bell (no relation): our experiment couldn't meet this standard, even if our equipment were perfect (for rather technical reasons). What we can do is put other specific models --- other ways of explaining the data that don't involve entanglement --- to the test. The ones we have been able to try, fail; quantum mechanics succeeds. So entanglement wins this round, yet again, but some alternatives still live to fight another day ...

Here ends the lesson. It's not usually my aim to post such pedagogical material on this site, but there is no end to the flaky silliness on these topics doing the rounds in popular culture, so I feel some kind of duty to fly the flag when I've been a part of the work. What the bleep do we know? Um, well, quite a bit actually.

^[1]Gravitational and electromagnetic forces act "at a distance" but their influence is not instantaneous: it's bound by the speed of light. For everyday purposes that's so fast that the influence might as well be instantaneous, but a lot hangs on the distinction. You can think of it this way: it's the gravitational and electromagnetic fields right where you are ("touching" you) that affect you, and they take time to catch up on what's going on elsewhere, the same as you do. These forces are still local in this sense.
The "spooky" part about quantum entanglement is that the connection between the parts of an entangled system works without any regard to distance whatsoever --- with no speed limit --- yet it turns out that you still can't use the thing to send a signal faster than the speed of light. Put like that, it seems somewhat contrived, and this is one of the things behind the intuition that it's our assumption of separability that's the problem, not the assumption of locality: it's not that relativity doesn't describe spacetime, it's that things really can't be divided up into "parts" the way we tend to think they can.

^[2] It's also publicly available on the arXiv preprint server as quant-ph/0702267.

^[3] Like many people (physicists included) I have my doubts about quantum mechanics: I suspect that there's something more going on. However, I also suspect that the "something more" will still leave us stuck with entanglement: that the weirdness is real.

Australian Research Fellowship

On Wednesday the Australian Research Council announced the "outcomes" for the 2008 round of Discovery Project applications.

I've received an Australian Research Fellowship for the next five years, and some additional funding: not as much as I asked for, but hey. I'll still be based at the University of Sydney, but with a proper job --- who knows, maybe even a proper office --- and will once again be doing work at CERN, the Jerusalem of particle physics. [Sigh.] I have been away for too long.

Some colleagues from Melbourne were also successful in this round: Prof. Geoff Taylor (overboss of particle physics in Australia) has received a Professorial Fellowship, freeing him from other duties over the next five years, as ATLAS starts taking data; and A/Prof. Martin Sevior and Dr Glenn Moloney received a grant to use the (computing) Grid to support particle physics work. Congratulations, guys.

Oh, and an old schoolfriend who is working on the theory of freedom of expression, in the law faculty at U.Melbourne, also received a grant. The DP process funds all sorts of things, medical research excepted ...

ATLAS under construction

There are time-lapse movies of the ATLAS detector under construction on YouTube here, in one minute and two minute versions. They give a better idea of the sheer scale and complexity of the thing, than mere description does.

ATLAS, and the Large Hadron Collider project more generally, was discussed in an earlier post

Charm mixing in Physical Review Letters

My experimental collaboration, Belle, has a paper presenting evidence for the mixing of charm mesons (D⁰ and anti-D⁰) in the current issue of Physical Review Letters.

This is an example of matter turning into antimatter, and vice versa. There are four known mesons for which this can occur without "breaking the rules", and the D⁰ system is the last of the four in which the effect has been observed. A related phenomenon may, or may not, occur among the neutrinos. (Mixing is known to occur between different neutrino types [called "flavours"], a process usually known as neutrino oscillation due to its characteristic signature. It's still unresolved whether neutrinos and anti-neutrinos mix.) It's a pretty big deal in any case, especially for those of us who've devoted time to studying the charm sector. Mixing is one of the principal concerns of the research group I founded at Belle (and ran for many years), and so finding it is a milestone for us. And personally, when a paper has taken a large fraction of your life for a year or more, it's very satisfying for it to be completed.

A semi-technical summary of the work is available in the news section of the CERN Courier. Our paper is PRL 98, 211803, also available as a preprint at arXiv:hep-ex/0703036. The competing experiment, BaBar, presents a different kind of evidence for the same phenomenon in a paper published back-to-back with ours. These results were the talk of the conference at the electroweak session of this year's Rencontres de Moriond in March, when they were first announced, and have provoked a lot of theoretical discussion since.