It just works... or does it? The dark side of Macs in HEP

If you attend a particle physics meeting these days (and most of us do, several times a day... this is not a good thing) it looks rather different to how it did 10+ years ago. Not that everyone paid attention then, but the type of laptop everyone's focusing on rather than the speaker has shifted, from the olden times array of various clunky black boxes to the situation now where 2/3 of the room seem to be wielding shiny silver Macbooks.

It seems like a no-brainer: Windows is pretty much 100% dysfunctional for computing-heavy science (unless you are either in a fully management role and never touch data, or for some reason love doing all your work though a virtual machine), but Linux is unfamiliar territory for most starting PhD students. Sure, it's a lot more user friendly than it used to be, with more helpful GUI ways to manage the system and the wifi even works out of the box most of the time. But Macs are perfect: beautifully designed, friendly, but with Unix underneath ... and they only cost an extra 50%! Ideal for HEP users who need Unix computing but want it to just work out of the box... and who doesn't? As the Apple advertising used to say "It just works". But does it?

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On unfolding

A while ago I was included in a discussion between an ATLAS experimentalist who had been told that some "unfolding" was needed in their analysis, and a theorist who had previously been a strong advocate of avoiding dangerous "unfoldings" of data. So it seemed that there was a conflict between the experimentalist position of what would be a good data processing and the view from the theory/MC generator community (or at least the portion of it who care about getting the details correct). In fact the real issue was just one of nomenclature: the u-word having been used to represent both a good and a bad thing. So here are my two cents on this issue, since they seemed to help in that case. First what the experimentalist was referring to as "unfolding" was almost certainly the "ok" kind: unfolding to hadrons, photons and leptons with lifetimes of at least ctau0 = 10 mm.

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Top mass measurements and MC definitions -- an inexpert precis

I was just recently notified that the world top mass combination uses "my" MCnet review paper on MC generators to justify stating that the definition of the top quark mass used in all (!) event generators is equivalent to the "pole" mass.

I've heard that statement very often, but not backed up by anything more concrete, so I was interested to read this section of the paper (Appendix C, starting on p184 of the PDF), which turns out to be rather good, interesting, and elegantly presented. Not to mention slightly embarrassing that I hadn't read it before, given that it has my name on the front! (In my defence, I did write some of this paper, just not that bit. I suspect most of the authors haven't read everything in it.)

Anyway, it definitely does not say that MC mass equals pole mass, so I thought it might be interesting to post my explanation of what it does say, at least as far as a dumb fence-sitting experimentalist/MC guy like myself can understand...

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Science TV is too nice

Well well well, another blog post, eh? So soon: it's only been... erm, two years. Oh. Well I never promised to be prolific. This one's come about because I grumbled briefly on Twitter about the nature of (British) pop-science TV and immediately hit the restrictions of that medium. Twitter is a wonderful way to share neat things that you find online, and to make pithy soundbites & jokes (and for describing what you're eating, the form of public transport that you happen to be on, listing film names with comic vegetable name substitutions...), but for exploring a non-trivial issue 140 characters is, to put it mildly, a limitation. I have difficulty fitting one of my normal sentences into 140 characters. So of course I came across as a whining idiot, prompting the reply "Yeah, we really should do more about how shit it all is. You don't see that tone ANYWHERE" from Dara O'Briain. Well, not remotely what I meant, but who can blame him? So here's an attempt at a more coherent and nuanced version that hopefully doesn't make me come across as an anti- science, axe-grinding git. But perhaps as a slightly grumpy science nerd, which is fair enough. There's been a welcome rise in the amount and profile of science programming on TV in recent years, a good whack of which is due to the influence of Brian Cox's three "Wonders" series', the LHC start-up & Higgs boson excitement, ... and who knows, maybe it's also due to The Big Bang Theory. Discounting the mostly-gawp-fest wildlife docs, there's been Dara's own Science Club, Astonomy Live, Bang Goes The Theory, at least a couple of series fronted by my old supervision partner Helen Czerski... and the long-running Horizon, of course. And that's just the stuff that I've noticed.

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Academic journals aren't helping us to do science anymore

Having recently concluded a long-ongoing saga to get the first ATLAS underlying event study both through the experiment's internal review procedures and then into the perverse format demanded by the academic journal, Physics Review D, to which we submitted it, it seems an apt time to offer a few comments on the state of the sacred academic publishing and peer review process. Over the years I've been in academic research, the tradition -- because it is largely tradition these days -- of academic journals has come to seem more and more perverse with each passing year. It is certainly an odd business: scientists spend months or years doing research, which we eventually write up and (modulo reviews, iteration and approval from colleagues whose names will appear on the author list) send to a journal. This final step is considered to be somehow magical, both individually by other scientists in their treatment of publication lists when hiring staff, and collectively by research councils and other funding bodies when reviewing grants (again, the review panels consisting of scientists, although not necessarily from the same field). The emphasis on publication lists seems to indicate a certain blind faith and lack of imagination in groups of usually contrary people when it comes to such revered procedures as peer review, for these days there is often little value added to publications by the arcane procedures and hoop-jumping required to obtain the mysterious approval that comes of putting an oddly-formatted journal reference in your CV.

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It's a bug, not a feature, Rene

I've had my attention drawn to this reply to a ROOT bug report, which I think highlights a serious problem with how the ROOT project interacts with the LHC experiments. In short, someone contacted the ROOTtalk mailing list to inform them that ROOT's calculation of weighted means is incorrect if there are negative weights involved. There is a well-defined procedure for calculating weighted means, and in fact it's dead simple. There's no reason to not get it right. This is a bug report, about a significant numerical error in just about the simplest statistical quantity that anyone might want to calculate: any statistical analysis tool worth bothering with would provide a bug fix as fast as possible. So how did ROOT respond?

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Back to life

I've never been the most active blogger, but 2 years between posts seems a little excessive, even to me! I wish I could explain the cornucopia of reasons for this, but I'll just point a couple of accusatory fingers at the extraordinary busyness of life (in the intervening time I moved to Edinburgh, the LHC restarted, and my working life has generally been batshit insane) and general frustration at my server setup. You may also be frustrated with the slowness of this server: turns out that running a mail server and a Rails application on a 256 MB virtual server puts me deep into the swap memory zone and site performance accordingly drops into the region marked "painful". I'd have loved to fix this 2 years ago, but a) I've written enough web apps in the past to not want to make another half-assed one, and b) did I mention work being batshit insane? Anyhoo, someone asked me at a recent meeting when I was going to start blogging again, and after the initial shock of discovering that I have some sort of niche audience I decided that I should start venting my spleen in more substantial ways than the 140 chars offered by Twitter.

A bit of recent server upgrading means that this site is not quite as slow as it has been -- I'm enormously impressed by the service from Slicehost, by the way -- and I'm going to try and replace Radiant with something a little more fun, speedy, and memory-efficient in this little pre-2011 gap. Suggestions of CMSes/blog engines with user comments, picture galleries, code highlighting support, etc. and support for static content (such as this site's Cambridge night climbing content) would be much appreciated. Oh, and because I'm a picky person and have not found Ruby/Rails to be a terribly pleasant development experience, being based on Python would also be a big bonus!

A week in the land of contradictions

It's the end of another busy week. Work life has been busy to the point of insanity recently, burrowing its way into every available bit of spare time... if you consider every weekend since mid October to be spare time rather than "essential time", that is. I'm actually inclined to the latter view: while happy to declare that my work is captivating and inspiring, some downtime is definitely needed. In the last month I've been to two week-long conferences in Italy, snatched a week back in Durham and then spent the last week in Chicago. After one more week in Durham, in which to pay some attention to demonstrating and marking Frank's excellent new computational physics course, I'm off on my travels again, this time to CERN for a week. And then it's Christmas and skiing; January is looking a bit crazy, and I'm trying not to think about that. Fortunately Jo has been a star and given me some (unearned) slack, but this schedule isn't really fair on either of us: I think I'll be imposing a more restricted travel schedule in the New Year and hopefully sending some collaborators out to do the salesman thing instead ;-)

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Burying the hatchet

"Ah, the famous Andy Buckley. Or perhaps infamous, no?". When a dapper French gent at a statistics conference addresses you this way, I guess it's normal to feel a bit perturbed, particularly when you've devoted a serious chunk of time in the last few years to publicly demonizing their work. Really, I suppose it's maybe a minor miracle that Rene Brun and I haven't crossed paths before now --- although I guess this is largely to do with me being keen to avoid a fight. Rene is, as particle physicists will know, the author of many infrastructural and statistical packages in high energy physics. In particular, he's head honcho of the ROOT system, a piece of software which I've long considered (not in isolation, I should add) to be fundamentally misconcieved in myriad ways. Despite being naturally non-confrontational, I managed once to become a sort of focus for community displeasure with ROOT, and hence a persona non grata among the ROOTisti.

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