maxwells_daemon

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.

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).



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!

Mitch Benn's Proud of the BBC is great (thanks to bibliogirl for the first recommendation). Go watch it now.

That's a fantastic song, but I'm not sure I can fully get behind the sentiment. Most of my BBC favourites are from some time ago. There are many excellent British programmes not on that list, mostly made by Channel 4. I am watching much more US TV nowadays, mainly because the BBC is producing much less good drama these days. (I don't even have an LJ icon from a BBC programme.) Maybe I can say I'm proud of what the BBC was and proud when it still, too rarely, produces something brilliant.

Qualifications aside, jinty alerted me to a meme that seems to be developing and I feel well-justified in spreading. ( Here are the programmes listed in the song that I have seen. )

I don't travel much, except to the usual places (and not much of even that of late), Geneva and San Francisco. But today I'm at DESY in Hamburg, so here are a few trivial observations.

Hamburg has lots of trees. This was obvious even from the plane.

DESY is like CERN on a weekend, but with German instead of French. And lots of trees. (Until recently, DESY had one of the major world accelerators, HERA. I imagine that when HERA was operational DESY was much busier.) The style of buildings, rooms, streets, etc is very like CERN. (One of my RAL colleagues told me that DESY was "like RAL, only more run-down", but I really don't see that.) I guess that won't mean much to anyone without a familiarity with particle physics labs, but maybe with some google-streetviewing, I could demonstrate - a project for later, perhaps.

In Germany, people rap on the table instead of clapping at the end of a talk. I vaguely remember this from a meeting I organised in Karslruhe, many years ago, but it came as a surprise. I think I like it.

I don't know exactly when his birthday is, but we were told that he was 13 weeks old when we got him, so he is about a year old now, and officially no longer a kitten but a grown up cat. He's certainly now a cat about town, a cat of the world, a cat who knows what's what. But even so, after a hard day's prowling the garden and environs, he still jumps on my lap and insists on being stroked. Or playing fetch with his toy mouse. Or peering between the banisters at me as I go down stairs and bumping noses (though this is rarer, as usually he'll follow me down). Or collapsing on my feet, rolling on his back, paws folded in, the unbearable cuteness of it making it impossible not to tickle his tummy.

So, I should post some photos as demonstration of what a beautiful grown up cat he is. He's not actually changed much for the last few months, though he is looking much more svelt with all the exercise he's getting. Unfortunately, my phone camera doesn't have a flash, making it difficult to capture a black cat in all his beauty in the house. This is the best I have, with freya_9 last month:

From Tim's Photos

Maybe someone who has caught Kzin on virtual film can post a photo in the comments?

Here's how we feel about all the beautiful collision data ATLAS has taken over the last few weeks.

(This is an "Armenteros Plot" of -p_T⁺ vs (p_L⁺ - p_L^-) / (p_L⁺ + p_L^-) (where p_T and p_L are the momenta (of the positive/negative daughter), respectively transverse and longitudinal to the decaying particle's direction), and shows the decays of K⁰_s (in the smile) and Λs (right eye) and anti-Λs (left eye). It was included in today's ATLAS Report on first collision data, though in a less cheerful form.)

I die! There is a great celebration in the land as news of my demise spreads. Workers up tools to dance in the streets, lighting bonfires to burn my effigy. Crops are not harvested, production lines grind to a halt, investments left to fail. As the cities burn and civilisation crumbles, starvation is not far behind. Cursing my name, all that I stood for, and all that I caused, all die! O the embarrassment!

(I've had plenty to apologise for of late, but this one isn't specific. See here for an explanation. Feel free to come up with your own.)

Looks interesting. Geoff Ryman, Gwyneth Jones, Ken MacLeod, Adam Roberts, et al.

http://www.manchester.ac.uk/aboutus/news/display/?id=5170
http://www.stfc.ac.uk/PMC/PRel/STFC/SciFacts.aspx

We were becoming quite worried. For two days, the only signs of Kzin were occasional rustle, occasionally eaten food, and used litter tray.

Then this evening, while we were watching Weeds, emily_shore noticed him sitting on his bed watching us. We kept still as he wandered around the room. He became very interested by both our slippers (not on feet) and then alternated between interest and trepidation as we proffered, then wiggled fingers and toes. After some time of this, I got a kitten toy (sparkly rattly ball with feather on a stick) and enticed him with jiggles, then rapid movements and all. We all had fun as he batted, pounced, and chased for much of the evening, slowly gaining confidence. We both took photos, though he's barely visible in mine (poor light - see how I need a gPhone!), so you'll have to wait for emily_shore's. Later, when Emily had gone, he even consented to being stroked a few times, while purring continuously (even for a minute after he'd moved out of stroking range).

There's still some way to go (sitting in lap, other people, especially jackfirecat, and other parts of the house), but it's surprising how rapidly he gained confidence after hiding for so long. I hope he doesn't forget tomorrow.

After jackfirecat heroically agreed to attempt to acclimatise to cat allergens, after helpful advice from many people, and after positive vetting by Cats Protection (by phone and then by a home visit, which will be followed up by a further check-up later), we now have a kitten! emily_shore and I went with Arshad, our cat advisor, to see the kitten we were offered, called Willow. He was living with a foster carer, Avril, and her 10 other foster and own cats. Of course as soon as I saw him, I was sold - I hope Jack and Emily feel similarly. Arshad asked all the sensible questions, so I think we made we made a reasonable choice as well. Avril was certainly a font of all knowledge cat-related and we spent an hour learning about vaccinations (all done), neutering (required when he's old enough), favourite food, etc as well as filling in adoption papers. We each got a brief cuddle and he seemed quite amenable to being held.

When we got him home, Jack joined us as we let him out of his basket. He emerged slowly, and then went straight under the chair and disappeared into the pile of boxes under the stairs. Since then, we've heard the occasional rustle, but the only evidence was once when Emily saw him visit the litter tray (what a well-trained kitten!) and a corner nibbled from his food. Avril had warned us that he was likely to hide for the first few days, but I hope he emerges soon.

"Willow" is a good name, but my old laptop is called Willow, so it would only be confusing. In any case, I'd like to call him "Kzin". I hope he'll live up to his proud name, except for the bit about killing or enslaving all humans and other non-Kzinti.

Since we haven't yet been able to catch him on camera ourselves, I made an icon from a photo of him last week in his previous domain.