South Park Tim

So what now? Whither Brexit?

Along with many of you, I’ve been pondering how we can get out of the mess that David Cameron dumped us in three weeks ago. I think I’ve found a way, which crucially might actually be agreeable to everyone who has a say in the matter. It gives us two possible outcomes: leaving the EU without too much pain, or remaining without too much strife.

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South Park Tim

Democratic EU

(Sorry for the long post. Summary: the EU is no less democratic than the UK.)

One undecided lady invited me in for a longer discussion. She seemed to be swinging towards Remain, and maybe I helped nudge her a bit further.

Her main worry was the oft-stated democratic deficit in the EU. This seemed to be the most common concern of the day (in East Oxford, even those flirting with Leave have better reasons!). My argument (far from original) was that the referendum isn't on whether the EU is well run, but whether we would be better off (in all senses) in or out. If we are in, we can push for improvements - as we have (occasionally) chosen to do in the past (with some success). If we are out, we still have to live next to/trade with/negotiate with our neighbours, but with much less influence on them.

But, thinking about it subsequently, I'm not sure that the EU is much less democratic than the UK. Compare the institutions:

The executive (EU Council; UK Prime Minister) are both chosen indirectly by Parliament. In the UK, we usually know which Prime Minister we are voting for (but maybe not if Boris takes over), and he is our chief representative on the EU Council. He chooses his UK Cabinet, who have specific responsibilities in the UK and on the EU Council.

Civil Service leadership (EU Commissioners; UK Cabinet Ministers): both appointed by the EU/UK executive. In the EU (but not the UK), the parliament can reject Commissioners. Other civil servants are apolitical. (By the way, the total number of EU civil servants is ~1/10th the number of UK civil servants.)

Parliaments: The EU parliament is directly elected by proportional representation. The House of Commons is directly elected, though not proportional to the total vote. The House of Lords is (mostly) indirectly elected (appointed for life by the elected government/opposition). In the UK, most laws are proposed by the Government, but in practice this is the Civil Service (under direction of the PM and Cabinet Ministers). Similarly, in the EU, all "laws" are proposed by the Commission. In both cases, the law must be approved by the parliament. The UK parliament can also initiate legislation, but "private members' bills" rarely pass.

There are some differences between EU and UK in the balance of power between the different branches. On the other hand, I think a Council of (qualified) equals is more democratic than a single prime minister, and a proportionally elected parliament is better than the (distinctly less democratic) mess we have.

Of course in the EU, it's not just the UK that has a say, but that's just a function of its larger size. If you object to that, then maybe I can ask for an independent Peoples' Republic of Oxford East.

The last argument (also made by my canvasee) is that fewer people vote in EU elections, and often they reflect national issues. The same could be said for UK local elections, but in any case, this is an argument for better voting in EU elections, not voting to leave the EU. It's hardly democratic to vote (once) to remove voting forever.
South Park Tim


I posted yesterday to Facebook, but I think it probably better belongs here...

On Sunday afternoon, I helped out canvassing (knocking on doors) for Britain Stronger in Europe. This is the first time I ever did anything like that, and I must admit I quite enjoyed it. It was a bit scary to have to talk to all those people, though most weren't home so just got some leaflets through the door.
With one group I did St Mary's Road (nearly all Remain), and with another Donnington Bridge Road (mostly undecided or uninterested).

Unfortunately, when I tried again yesterday, I didn't find anyone from the Campaign (turns out they'd finished Iffley Village the day before but didn't cancel the meet).

Today I went with Labour In For Britain (the time was convenient), canvassing on the Iffley Road. This was a large group of ~15 people with one organiser, who sent us off to knock on each door. I think I'm getting a taste of canvassing. Tomorrow evening (getting people out to vote) is my last chance for a long time!
South Park Tim

Exciting non-discovery from the LHC

In my occasional efforts to keep you abreast of the latest results from the LHC, you might find this paper on heffalon production of interest - even if a day late. I thought the experimental methodology exceptionally robust, though there is an acknowledged fine-tuning problem with their theoretical model. C. Robin, W. T. Pooh, and Piglet will have to wait for the LHC energy upgrade in 2015 for their next chance at the Nobel (though I think it was Piglet alone who first proposed the heffalon hypothesis).

PCC Elections

I enjoy elections and think it is important to vote. So much so, I vote in two different countries where I am eligible to vote.

But I don't agree with today's PCC (Police and Crime Commissioner) elections. I think criminal justice is the one of the worst things to make directly elected (just look at elected prosecutors and judges in the US). So, I've been wondering what to do. Many people have suggested not voting or (better) deliberately spoiling their ballot as a protest. On the other hand one of the candidates does seem better qualified than the rest, so it would be a pity not to register my opinion. [*]

In the end, I went and marked "scrap PCC" (ie. spoilt) as my first choice and my preferred candidate (Tim Starkey, Labour) as second choice. I don't know whether that will be counted the way I want, but it's the best I can do. (They could discard the whole ballot as spoilt, or count my second choice as a first choice.)

The polling station was empty (apart from the tellers, one of whom was off making tea) when I went in at 5pm, so I guess most people are not voting. I told the teller that I was sorry that they had to be there, but he said he enjoyed elections. Even more than me, it seems!

* Also, The Economist argues "If turnout in next week’s elections is really low, England and Wales (Scotland is sensibly sticking with police authorities) could end up with mighty figures who feel untrammelled by public scrutiny."
South Park Tim

Discovery, but is it a Higgs?

After months of equivocation ("hints"), we can finally say that we have discovered something.

It was all very exciting. I'm not used to hearing applause in the middle of a physics presentation. And the second time (ATLAS), they were applauding the number ("5.0σ") that I helped determine.

ATLAS see a 5.0σ excess, and CMS see 4.9σ. Each alone would probably be enough to claim a discovery. (According to particle physics convention, one needs >5σ. It is arguable whether one needs to include the "look-elsewhere effect", which reduces the significance to 4.2σ-ish, but one can either combine ATLAS+CMS (as some blogs are already doing), or use CMS to limit the ATLAS search range (or vice versa) so each doesn't need to look elsewhere.)

There certainly was an observation of a Higgs, but that was Peter Higgs, who attended the presentation. But we can't say that what ATLAS and CMS have discovered is a Standard Model Higgs boson. The observations are compatible with a Higgs (though both ATLAS and CMS see a few more decays to two photons than might be expected, which is what pushed us over the 5σ line), but now we need to measure its properties to see whether it's a SM Higgs, some other sort of Higgs, or something entirely new and different.
South Park Tim

Higgs excitement

Today was an exciting day. Finally we can see our our new Higgs search results public, and we can see what CMS have seen and compare. As everyone keeps emphasising, we haven't discovered the Higgs. ATLAS has seen a fairly large "excess" and CMS have a couple of moderate excesses, one of which matches ours at a mass of 126 GeV.

You might want to stop reading here, as it's all science (too much science for LJ?) from here on in...

The two most telling plots are these:

which give the significance (actually (im)probability that there is no Higgs at each mass) of the ATLAS and CMS results, separated into different channels (ways the Higgs can decay) and combined (in black) within each experiment. Those plots are the ones to look at to answer the question "did we see anything?", so probably most interesting at this stage (nothing to do with the fact that I worked most on this one for ATLAS, though I was a small cog in an enormous machine).

If this is a hint of the Higgs, then ATLAS was rather lucky to get such a large signal (though it is still not so large to be suspicious). If this is a statistical fluctuation, then ATLAS was really unlucky (as our spokesperson put it "if it's background, it will be really difficult to kill"). CMS's smaller signal was neither lucky or unlucky.

These numbers have to be corrected for the "look-elsewhere effect" (the fact that we are looking for the Higgs at many different masses and if we look often enough we are bound to see a statistical fluctuation) - unfortunately this was not included in all the internet rumours that prefigured the announcements, so today may have been a bit of a let-down for some people. There is actually a philosophical problem with that correction: should we count everywhere we looked, or just the area that we are still looking (and haven't excluded). ATLAS and CMS actually took different options in their conclusions (probably because it doesn't make much difference for ATLAS, so they can be conservative, while CMS have nothing very exciting to say if they follow us).

So ATLAS/CMS see a significance of 2.5/1.9 sigma (0.6%/3% probability that this is just chance, not a Higgs) or 2.3/0.6 sigma (1%/27%) for a Higgs at around 124/126 GeV, depending on how you calculate the look-elsewhere effect. It is quite incorrect to try to combine these numbers without detailed study (several of the uncertainties are correlated between ATLAS and CMS - it took months for ATLAS and CMS to combine their previous Higgs results), but that hasn't stopped the blogosphere. If you were to naively combine the larger set of numbers you reach 3.1 sigma (0.1%), which in our field is sufficient to claim "evidence" (still well short of 5 sigma required for an "observation"). But I couldn't possibly comment.

For me, the fact that we see an excess at the same place in so many channels (3 channels in ATLAS, 1-3 in CMS, not to mention various sub-channels), makes me quite hopeful that this is something real. Each channel looks for different things (and the two experiments have different detectors and analysis techniques), so it is unlikely to be a mistake. That means it can probably only be a fluke if this isn't really a Higgs. Next year we hope to have lots more data (and at a higher energy), so we should be able to pin it down soon.
South Park Tim

The Asimov data set

I've been a fan of Isaac Asimov since I was a teenager. I read all his short stories and novels I could get my hands on, and it was probably his essays on science that did the most to get me interested in physics. So I have found it immensely cool that his name is being bandied about in so many discussions in the ATLAS combined Higgs search group.

It is all down to a paper by some of my colleagues (two of whom I am working with now, and another who helped introduce me to another piece of statistics I am working on). They dubbed a representative data set, used to calculate expected sensitivities, the "Asimov data set" and cite Asimov's short story, Franchise (I should probably add something to Wikipedia). I remember the story well: it's about someone chosen by Multivac (a global supercomputer) as the sole voter, because his views are representative of the whole population.

Since it has come up in so many discussions over the last year, I've followed the evolution of the term: "Asimov dataset", "Asimov likelihood", "Asimov method", "Asimov distribution", or just "the Asimov". I get a little thrill each time I hear a new one (I know, I'm a real fanboy).

Despite this, what I've been doing in the Higgs group is to cross-check the asymptotic results, which use the Asimov method, using more traditional methods (known as "ensemble pseudo-experiments", or more informally as "toy Monte Carlo"). They don't rely on assumptions like large statistics (as did Multivac, or Hari Seldon, for that matter), but do require a large amount of computer time to generate many random pseudo-experiments. I developed a way to run these on the Grid. With hundreds of thousands of machines round the world, I have used 8 years of CPU time to generate 8 million toys in a few days.

This sort of thing went into the results that generated some excitement in the summer (eg. p14-16 of the EPS conference presentation). I'm not allowed to say what we will show on Tuesday, but it should be worth watching.
South Park Tim

ATLAS shifts

I'm on shift controlling LHC's ATLAS detector! There are about 15 of us, but I'm in charge of the Run Control system that is in overall control, so I say I'm the most important.

I must say that, compared to DELPHI and BaBar, the ATLAS control room looks like a control room should with everyone in serried ranks facing the giant screen wall at the front. Like Mission Control, only with events and trace plots instead of trajectories and delta-Vs. Here's me on the web-cam (first row, second set of desks).

ATLAS Control Room web-cam

Since people have asked: I've done well at not creating a black hole and gobbling up the world. But in fact, my job would be to detect the black hole when the LHC produces one, so I guess I failed at that.

I did start a couple of runs, the last of which lasted for 23 hours (and included some Van der Meer scans - named for the Nobel laureate, who recently died - where we could see the beams being moved back and forth on the beam position monitors).

Unfortunately these are 2.76 TeV collision-energy runs, which we are doing primarily for comparison with December's heavy-ion data, and not of such interest to what I'm doing. Maybe when I'm on shift next week, we'll take some 7 TeV data.

LHC just declared stable beams, and we're off again! Woot!
Home Computer 2004


There's good news and bad news.

The good news is much-anticipated: the first new TiVo model in the UK for a decade, and it arrived today! (According to the engineer, I'm the first customer to get one in Oxford.) It is very whizzy with dual-tuner HD recording direct from the cable and integration with the on-demand services, YouTube, etc. It has some annoying features (especially having to enter a PIN every time one wants to watch a recorded 15-rated programme before the watershed) and lacks some things my old TiVos could do (notably copying recordings to PC and no hacking), but is mostly a big improvement.

The bad news has been long-dreaded: the day mine arrived, TiVo announced that they'll soon stop sending schedule information to old TiVos, rendering them near-useless. This is very sad, especially for people who can't get a new TiVo (it is expensive, since you have to get Virgin's top TV package, and only available in cabled areas). Hopefully an alternative way of providing the schedules can be worked out by all the TiVo hackers who want to keep their TiVos going (this has been done elsewhere, so it's probably feasible). I'm almost tempted to help, since I'll miss hacking the new TiVo. (I did a lot of work on my old Palm phone after I moved to Android, but that was just to transfer stuff over - transferring from old to new TiVo is more limited.)

[ETA: a search just revealed that I previously posted about TiVo in 2004, excited by the (until-now unrealised) possibility for a new TiVo model. So I've been anticipating this for at least 7 years!]