Quantum Diaries

With shock and unease I’ve been watching the news from the devastating earthquake and subsequent tsunami in Japan all weekend. My deepest sympathy goes out to those directly affected, and to the families who have lost loved ones. I sincerely hope that this hard blow by nature is not followed by a man-made catastrophe in the nuclear power stations which are experiencing severe problems right now, with worrisome news that keep me glued to the news tickers.

Amidst all this, there is a silver lining: I am very relieved that fellow blogger Susanne is fine. From my Belle colleagues, reports are also coming in, despite unreliable connections and power cuts. So far all were good news about people safe at the lab and in their homes.

Munich main station, early morning: My train to Frankfurt (continuing to Dortmund) is getting ready for boarding.

A post from a slightly unusual location: I’m sitting on the train from Munich to Frankfurt Airport. Instead of flying, I went for the train because in terms of travel time, it makes almost no difference, considering that you have to be at the airport quite a bit in advance to go through security. And then, Frankfurt is only about 400 km away. Without all the hills in southern Germany that get in the way, and the many stops (even this super express train stops at almost every medium-sized town on the way), it could beat the plane by a very comfortable margin. And then, there is winter, where air travel is always a bit more prone to delays. But this winter, the Germain Rail lost most of its advantage, with (if I remember correctly) less than 30% of the trains more or less on time over Christmas, when we had quite a bit of snow.

I’m going to Frankfurt today for a meeting where the plans for a continuation of the Alliance “Physics at the Terascale”, which unites all German high energy particle physics groups in common projects and with shared infrastructure, will be discussed. The next few months will be well filled with events like this: Also the Excellence Cluster “Universe”, which funds my research group, is discussing plans for the next funding round beginning in fall 2012.

Frankfurt airport is a perfect (although quite pricey) location for the meeting today: Easy to reach from all over Germany, it means this is just a day trip for everybody. But it still means getting up early, certainly for me. I’m just not a morning person, getting up a bit after 5:30 is not something I do if I can help it. I know people who do this voluntarily all the time, but I don’t get that… Well, I guess everybody is a bit different in that respect… But now that I am awake, I can at least use the time, to write a short post, and to prepare my lecture on Supersymmetry on Monday…

In particle physics, we often use toy models, both to describe complicated things in (hopefully) easier to understand ways, but also to quickly study the effects of some changes to a detector or to some analysis. Now, students of the University of Tokyo gave us a whole new toy to look at: A full model of the Belle-II detector… constructed in LEGO. Complete with illuminated particle tracks, it gives us all something to look at while we are working to construct the real thing.

It is the middle of January, and the new year is definitely keeping me busy. Lectures are still on at the Technical University of Munich, and a good week ago, I kicked of the year for my students with a journey back in time for me: Heavy Ion Physics, and the search for / study of the Quark Gluon Plasma, or what is now called a strongly coupled QGP aka The Perfect Liquid. For my PhD thesis finished six years ago, I worked at the STAR experiment at Brookhaven’s Relativistic Heavy Ion Collider RHIC, a facility we’ll be hearing of here quite a bit in the future in BNL’s blog, I’m sure. Back in my time as a student at RHIC, the results that led to the discovery of the sQGP, such as the observation of collective flow of the matter produced in the collisions, evidence for the absorption of jets in the hot and dense medium (“Jet Quenching”), …  were just coming together, truely an exciting time. Today, things are equally exiting in this field: We are now seeing first results from Lead-Lead collisions at the LHC, which show a fantastic strength of the jet quenching, spectacularly illustrated by event displays from the experiments, and a continuation of the almost ideal hydrodynamic behavior of the matter it this new, much higher energy. The very first impressions were nicely summarized in a Physics Viewpoint.

I’ve been giving my lecture on high energy hadron collider physics for the third Winter in a row, but this time is really special: All topics that I cover now have new LHC results to go along… Detector physics, Top Quarks, seaches for exotic phenomena like micro black holes, heavy ion physics… and SUSY will be coming up next on my list. I hope I can convey some of this excitement to my students!

Then, two days ago I took a quick detour to Dark Matter physics, since I had Laura Baudis from Zurich as a guest in the Munich physics colloquium. Another area with a lot of excitement currently: Direct detection experiments could see really convincing signals from dark matter particles any time now, and there is already quite some controversy about exiting results. Definitely something to watch out for in the near future!

And, after a couple of weeks in Munich, I’m back to my life on the road: Two days in Hamburg, already completely filled with discussions about publication plans and analysis results from the CALICE calorimeters… And the trip gives me the opportunity to blog from where I usually do: At the airport, waiting to board…

So, this is it. In a few hours, 2010 will be history (in quite a part of the world, about 1/3, to be precise, it already is). After a very long silence, high time for a few thoughts… I think it has been a very good year, and a fantastic one for particle physics.

First and foremost, there was the LHC, with fantastic performance. But not only that, the future is also looking good. Jonathan posted this a few days ago, and I guess many of you have heard about it, via CERN mailings or the Interactions.org news: Italy is putting substantial funding up for the development of SuperB, a super flavor factory to be based in Italy. And for SuperKEKB, the Japanese super flavor factory , already well on track, excellent news concerning the funding by the Japanese government has been circulating these past days on the mailing lists.  So, everything is pointing towards a start of SuperKEKB physics in 2014, less than four years down the road: Busy times ahead for us to get ready in time!

Of course flavor factories alone are not enough to keep particle physics vital in the long run, we thrive on international experiments at energy frontier, at the very edge of technology. Also in that respect, 2010 has been a good year: A very successful workshop in Geneva in October united the two communities working on this next big project: A linear electron-positron collider. Both for the ILC and for CLIC, an active research and development phase is currently ongoing (and has seen big steps forward in 2010), with the goal to work out proposals in time for first discoveries at the LHC.

So, what remains? In terms of New Physics, we have entered a dark room that might hold many surprises, but we are still in the process of getting the flashlight going. The fact that we have not hit our toes on something big in the dark already tells us something, though… Two examples: There are no striking resonances (such as excited quarks) at masses below about 1.2 TeV (ATLAS, http://arxiv.org/abs/1008.2461). There are no simple microscopic black holes (probably an unlikely, but too me at least one of the most exciting possibilities: Adding gravity to the particle physics menu, hard to beat that!) below about 4 TeV (CMS, http://arxiv.org/abs/arXiv:1012.3375).

For 2011 I have high hopes – the best that could happen, also for future projects and in view of funding cuts threatening the fields, is to move from limits and exclusions to evidences and discoveries. Who knows, fantastic surprises might be just around the corner!

With that, time to celebrate 2010 and to welcome 2011, a happy and successful New Year to all of you!

This weekend, CALICE has opened a new chapter of calorimeter testing: Our first full physics prototype of a digital hadron calorimeter saw its first pions at Fermilab! So, what is this about?

One of the first 32 GeV pions seen in the CALICE Digital Hadron Calorimeter at the Fermilab Meson Test Beam Facility: Amazingly detailed pictures of the shower structure!

As you know from many previous posts here, the CALICE collaboration develops calorimeter technologies for future experiments based on particle flow event reconstruction. On the hadron calorimeter side, so far we’ve been looking at a highly granular analog hadron calorimeter: Many small plastic scintillator tiles, each read out with a tiny silicon-based photon sensor, and all that sandwiched between layers of steel absorbers, 38 of them. The “analog” in the name means that each of these cells gives out a signal that is (approximately) proportional to the energy deposited in it by throughgoing particles. By summing up the energy of all cells that saw something, we get the energy of the particle that hit the calorimeter. Of course there are very sophisticated techniques how the “summing up” is done precisely, which results in better measurements. In total, this device has close to 8000 electronics channels, all packed into one cubic meter.

Now, a digital calorimeter does things a bit differently: Instead of an energy measurement for each cell, you only get a “0” or a “1”, depending on if the cell was hit by at least one particle or not. The total energy you now get by just counting the number of “1” in your detector, again with the possibility for more sophisticated techniques. At first glance this might look like a bad deal, since you loose information. However, with the digital readout you can use simpler detectors and electronics, and thus get many more readout channels. The current 1 cubic meter prototype, that uses exactly the same steel as our analog calorimeter, has 350 000 readout channels, quite a bit more than the analog detector. And it uses so-called Resistive Plate Chambers (RPCs), simple gas-based detectors.  So you get a more precise spatial image of the particle showers, for the price of sacrificing the cell-by-cell energy measurement.

What will work better? That is exactly what we are trying to find out. The first CALICE Digital HCAL, constructed in the US under the leadership of Argonne National Lab, has now started to take data at Fermilabs Meson Test Beam Facility. With those data, compared to the ones we already have for the analog calorimeter, we can hopefully make a significant step in the direction of answering that question. The first event images show amazing detail, quite a bit beyond what we had previously (for a shower picture from the analog HCAL take a look here).

I, for one, am very excited to see what the results from this new detector will look like!

Early morning start on the parking lot outside of CERN: Sunrise, and a fantastic alpine panorama.

Finally some down-time – in seat 3F on the late evening flight from Geneva to Munich. All week has been exceptionally busy: I attended the International Workshop on Linear Colliders (IWLC) in Geneva. This workshop, for the first time, truly combined the CLIC in ILC communities, both on the accelerator side and on the physics and detector side in one single meeting. Not surprisingly, it was a very big meeting, beyond what could be hosted at CERN. That is why we spent most of the week in a conference center of Geneva. A very nice facility, but with one down-side: To keep my travel budget from a complete disaster this year, I was staying in the CERN hostel, which meant leaving for the conference center with a bus at 7:45 each morning… That translates to getting up at 6:30, not exactly my favorite time. Especially since conferences always mean very late nights, due to drinks with colleagues and work on talks.

The CERN DG, consulting a "crystal ball" during the conference dinner.

This time, things were even more tough than usual: I gave the summary talk of the Top/QCD, Electroweak and Alternative Physics session. Such a task means that the last night of the conference is completely spent preparing the talk for the next (final) morning… And often, that is the evening of the conference dinner. Not so this time, the (admittedly fantastic) dinner was on Wednesday, much more summary-speaker friendly.

Stress, lack of sleep and all, the meeting was absolutely worth it. A lot of interesting talks, good discussions, and a highlight: Rolf Heuer, General Director of CERN, looking into his Crystal Ball. Apparently he saw 2025 as the physics start date for a Linear Collider – but he did not want to assign a confidence level to this, I guess the crystal ball still needs some calibration…

Email addicts in Big Meadows Lodge in Shenandoah National Park.

We’ve seen it before here on Quantum Diaries: One of the more important aspects of life as a particle physicist is being connected. Many things in our line of work are happening over email, since we have collaborators spread over the planet, many things require informing a large group of people and so on. While email is terribly convenient, it also tends to pile up. I always notice this in particular during vacations: Life does not stop, even if you are not paying attention. On a typical day I get between 50 and 100 emails, many of which luckily don’t require a reply, but are still important to keep up to speed on all sorts of things. This is just a consequence of being a member in several experimental collaborations, plus a committee here and there. So, I hardly ever go anywhere without my laptop, and I’m happy if I have wireless internet to keep the flood at bay – I really hate it to come home after a week or two to more than 1000 emails in the Inbox.

Of course there are compromises to make: If you spend time out in the wild, in a National Park, you don’t really expect to be able to go on line. So, imagine my surprise when I found out that the main building in the Big Meadows Lodge in Shenandoah National Park has free internet! It does not get much better than this: Adventures during the day, including a face to face meeting with a black bear, and still some connection to the outside world. And, not surprisingly, I’m by far not the only addict: After 9 pm, there were quite a few glowing laptop screens to be seen in front of the crackling fire place in the main lodge…

Connected at night, adventure during the day: Face to face meetings with a black bear included. He turned out to be a shy and friendly guy, luckily...

Fall is in the air in western Massachusetts in the early morning.

Finally almost two weeks of vacation. Not the ideal time, since life after summer has started everywhere already, so I am missing a couple of meetings and other events, but still, it is worth it. This time we are overseas, at the moment in Washington, D.C., where a friend of ours got married on Saturday. A welcome occasion for a visit to the US capital, and later a visit of friends in New England.

When we arrived in Boston on Wednesday night, temperature wise it felt like summer, with temperatures beyond 30 degrees, which we have not seen in Germany for a while. But still, fall is here, the leaves are changing color, fog on the fields in the morning, and foliage season is just around the corner.

We also took the chance to visit D.C., stroll along the National Mall, and eat a damn good burger at the Presidents favorite burger joint (allegedly).  At the evening drive through the city to see the beautifully illuminated monuments, our car, prompted by one pothole too many, decided however to throw one of its hubcaps in the direction of said Presidents house, right at the corner of Pennsylvania and 17th. I went once around the block, and much to the entertainment of the police and U.S. Secret Service, my wife jumped out to recover our hubcap. Loss damage waver for the rental car is nice, but of course it is preferable to bring everything back in one piece…

Fantastic weather in DC...

Empty lake north of Munich: At a weekend at the end of August, no grass should be visible for all the people lying in the sun... But it feels like fall, not like summer with temperatures just a bit over 10 deg. C.

It already feels like fall. Munich has been quite cold and rainy lately, and even on days with sunshine, the thermometer never made it above 20 degrees C. Last weekend I had to get out my long cycling pants when I took my bike for a spin. Passing by a local lake that is usually packed with people lying in the sun or swimming on a weekend in late August in the Bavarian school holidays, it really felt like that Don Henley song… “Empty streets, empty lake…”.

Another sure sign that fall is coming: Travel has started again. After two months at home, right now I’m sitting on a flight to Geneva, enjoying the fantastic alpine panorama that passes by. That immediately reminds me of earlier this year, on what very well might have been the hottest day of the whole summer in south-eastern Germany, the day of the final of the soccer world cup. What a crazy idea to go hiking just on that day! But we did it, a strenuous climb in brutal heat. The reward was however, once we were 1000 meters above the Inn valley, the air was fresh and a lot less stifling. Plus, a fun rock scramble over something like 50 vertical meters up to the “Wasserwand” (literal translation water wall, but there was no water anywhere near). Quite exciting, with hands slippery from sweat gripping steel cables. The tough thing about these types of climbs is always that going up is easier than going down, since you can see where to put your hands when you go up, but not necessarily where to put your feet when you go down.

Going back down on the steep south face of the Wasserwand: A good thing that there is a massive steel cable to grab just in case outside the picture to my left.

The summits outside the window however are much more intimidating, and way beyond my mountaineering abilities… Mont Blanc is now coming into view, with the Aiguille de Midi sticking up left of the summit, all covered by snow glistening in the evening light above the clouds… That means I’m getting close, time to shut down the computer, and to get into test beam mood, which we’ll start tomorrow morning at the CERN Proton Synchrotron.