Plans for the New Year

Just in time for Christmas, I received approval for posting a job ad (also on inspirehep jobs). I look forward to starting my own research at PNNL in earnest. So, to set the context, here's a bit of a rundown of what we're trying to do in the near future:
The ILC detectors are preparing to start TDR in the next year or two. For this we need to answer a couple of difficult questions convincingly. We'll have to justify the choices for all of the detector parameters. We haven't really changed them since the LOI in 2009. That was before the discovery of the Higgs boson. We'll need to take a good look at them again and study if they are still optimal and how much small changes affect the physics reach of the experiment. For this, we need to build new tools to better understand the connection between the detector parameters and the measurement precision. In a PFA detector, the reconstruction is a big part of the detector concept. I'm interested in studying the performance of the reconstruction under both physical and computational aspects.
In no particular order, here are a few things we already know that need work.

• Vertex reconstruction and flavor tagging:
• How does it perform with more background?
• Is the innermost layer at the right distance from the IP?
• What changes are needed to implement gaseous cooling?
• Silicon tracking
• What are the current limitations of the tracking, and can we overcome it with a pixel tracker?
• What can be gained from a different aspect ratio?
• Calorimetry
• How big of an advantage does digital calorimetry have over analog?
• What's the right size for the readout?

I'm sure there will be other questions that come up during the year. I look forward to working on these and other items with a motivated and capable scientist who will join us at PNNL. Let's roll up our sleeves.

US-Japan connections

Finally our household arrived at our new place a couple of weeks ago. My wife is putting in a lot of effort to get everything out of the boxes to build a new home for us.

When I moved from Japan to the US, I did not only take my wife and my household with me, I was fortunate enough to convince my new employer to also let me bring my research.
International collaboration is of course one of the enabling factors of the ILC, and fortunately, frameworks exist already to enable collaboration in all kinds of scientific experiments. Together with my colleagues in Japan, we put forward a small proposal under such an umbrella, the U.S.-Japan collaboration. Last week, we hosted a delegation of Japanese and U.S. scientists as well as representatives from DOE at PNNL, where the different proposals under this umbrella were reviewed. Our proposal to establish distributed computing between the two regions with the goal of accelerating the detector optimization studies and  improving the distribution of collaborators from the two regions across the two detector concepts, was approved for funding.

Now I'm at the ILC Tokyo symposium, where we heard from a Diet member why the Japanese population is declining, and what the government intends to do about it. The talk was very interesting and a lot more technical than I would have expected from a politician. It was humbling to see how our vain little experiments can have a much bigger impact.
The spirit of the meeting was very positive, and things seem to be moving in the right direction. I look forward to the next few months. They will be very busy, but they also hold a lot of promise.

FPCCD Neutron Damage test at Tohoku CYRIC

From afar the ILC detectors are going to have a very similar look to the LHC detectors ATLAS and CMS. They are cylindrical objects, with different sub-detectors for measuring different properties of the high-energy particles that will be produced by the collisions of bunches of electrons and positrons. Closest to the interaction point in the center of the detector will be the vertex detector for the precise measurement of the decay point of long-lived particles. Next, a tracking detector measures the momenta of charged particles from their trajectories in a magnetic field. The calorimeters outside of the tracking detectors measure the energy of the particles.
Yet, at second glance, because of much cleaner environment of the ILC detectors, particularly the inner detectors look very different from their LHC counterparts. While for the LHC detectors the requirement of radiation hardness puts a serious constraint on the achievable precision, ILC vertex detectors hope to achieve about an order of magnitude better precision on momentum and impact parameter measurements. Nevertheless, radiation damage is also a concern for ILC detectors. The beams after the collision cannot be re-used for collisions. (But we can hopefully recover at least some of their energy.) The current plan is to safely dispose of them in a beam dump. Some of the neutrons produced there can travel back up the beam pipe and enter the detector. Their energy has been studied and roughly looks like this.

 

Expected Neutron energies from the ILC beam dump.
The first layer of a vertex detector at the ILC has to deal with
up to 10¹⁰ neutrons / cm² / year

Not a big problem compared to the factor of about 1,000 that the LHC detectors have to cope with, but nevertheless something we need to study. We have a facility at Tohoku University where we can get a neutron beam. The energy is close enough to what we would expect at the ILC.

Distribution of Neutron energies in the
Tohoku CYRIC facility. We still have to
evaluate our own measurements of
 neutron flux and energy.

After some intense preparation and frantic manufacture of beam profile monitor from scintillator bars, we now have pixel detectors with the equivalent of about 2.5 years equivalent of ILC neutron dose. Analysis of the data is underway, so I can't show anything yet. We are still not even done with the complete analysis of last year's data. Here are two plots to give you just a rough idea of what we are studying. I will try to go into more detail in some future blog posts.

Active area of the FPCCD chip. The red dot is a "hot pixel".
Similarly to a dead pixel in your LCD screen, this is bad.
In this case, we define a "hot pixel" as one that has a signal
significantly above the (blue) background.

We are measuring the number of pixels that was affected
by the neutron radiation. As you can see, measurements
at low temperatures are significantly less affected by the
damage, but the difference before and after irradiation is
obvious.

The ILC and time zones

A surprisingly big problem in a global collaboration is to find a meeting time that suits people in Asia, America and Europe equally badly well.
Usually this means getting up early at the west coast of the US, and being up late in Japan. The Europeans sacrifice their tea time or run into conflict with supper.

The fact that Europe and the US cannot agree on a common start and end of daylight savings time, adds an additional dimension of complication, because - when do you change the time of the meeting: When daylight savings time ends in Europe, or in the US, or do you change it at all? Japan, after all, does not change the clocks.
This whole conundrum leads to much confusion and conflicts. Even more confusing is the fact that some of my venerable colleagues do not seem to understand the abbreviations of time zones. Here is something that helps:
http://www.timeanddate.com/time/zones

So here's a suggestion: Since the ILC will be built in Japan, the canonical time should be JST.
For all of you that don't know what time zone they are in (and there's a few of you, don't deny it), this may help:
http://www.timeanddate.com/time/map/

Finally, our default online agenda - indico - has support for displaying the meeting time in your favorite time zone.
So please, let's all specify the time zone when we announce a meeting. And let's not miss any more meetings because of time zone confusion.

LCWS14 Recap

Every year the Linear Collider community comes together for two large meetings. One is a regional meeting, usually held in spring. Every year this rotates between the three regions Asia, Europe and the Americas. The other meeting is the Linear Collider Workshop (LCWS), usually held in Fall. This is also hosted by one of the three regions in alternating fashion, and it's not the same region that holds the Spring meeting of the same year.
This year's event was in Belgrade.

View from the Fortress

The city still has not entirely recovered from the effects of the war over 15 years ago. As we were shuttled downtown for the summary sessions on the last day, we saw some derelict buildings with heavily damaged roofs at the outskirts of the city. Downtown, however, was very nice. There are plenty of options for dining, people were very friendly, and it was extremely easy to communicate in English.

The conference itself was held in two upscale hotels. Attendance was unfortunately not as good as previous workshops, but that did not stop the Serbian President from stopping by our little gathering. The sessions were a mix of plenaries and parallel group meetings. A notable item on the agenda was a session on how to make the ILC physics case. We were reminded on the first day that we should try to strengthen our presentation of the potential for discovery of new phenomena beyond the Standard Model. My colleagues and I believe we have a very strong case, so I guess we need to package it better. If you would like to contribute, post your video to the ILC communicators and let us know if you have suggestions how to present the ILC physics case.

In addition to politics we also did some real work. The reality of having a candidate site was very noticeable at the workshop. Both detectors have to agree on a common interface with the collider, which will lead to some changes in their design. And the design of the campus, including a computing center, is progressing as well. The work on estimating the computing requirements, both, for the proposed campus and off-site, unfortunately distracted me somewhat from carrying out my duties as a session convener. Thanks to my co-conveners, in particular Sophie Redford and Jerome Baudot, for picking up the slack.
The details of the computing will be the subject of a post once we have understood the details a bit better.

Goals for Detector Optimization: Mass resolution

We have several goals to optimize the ILC detectors to make the best use of the events that the machine will deliver. The physics case depends strongly on being able to deliver high precision and to cover as many new physics scenarios as possible that are still left after the LHC program. For this, we need to make sure the detectors meet our high performance standards. I have prepared an IPython Notebook that investigates the effect of the detector resolution on the reconstructed mass of gauge bosons. You can see that a seemingly small degradation in performance can have a big effect on the physics. We need to understand all of these subtleties when optimizing our detectors.

The ILC site visits

In my role as the deputy LCC Detector R&D liaison, I have visited the recent workshops of the SiD detector and ILD detector collaborations in Tokyo and Oshu City, respectively. The purpose was to give an overview of where we are in the process of documenting and advertising technologies developed for the Linear Colliders.

While I generally enjoy my work, there was an even more fun aspect to these workshops. Both were coupled with a visit to the ILC candidate site in the Iwate prefecture. One started from Ichinoseki, the other one started from Oshu City. Both of these cities are candidates to host the ILC campus. From my home in Sendai, it's 34 minutes by Shinkansen to Ichinoseki, and another ~30 min by local train to Oshu City. That's pretty much commuting distance.

The local support for the ILC is very visible. There are ILC banners at the lamp posts in Ichinoseki, which you can see in Google Street View, for example, or, of course by just wandering down the streets physically rather than virtually.

Around the planned site there are several signs of support, like the two pictures to the left.

The area around the planned site is very rural. During the visits, several references were made to the nature and to the peaceful and quiet environment. The construction of the ILC will certainly change that, but hopefully, the operations phase after construction won't be too intrusive. The exact location of the campus and the sizes of the site campus and the science city are still under discussion. While some people might enjoy living close to the site in rural Iwate, others will prefer the proximity to shops and businesses of the science city. Or, like me, to live in Sendai.   

The first month in review

The first month in Sendai has certainly been rather eventful. The excitement of the new environment hasn't worn off, yet, but fortunately I'm starting to become more productive. I still don't have my household, yet; apparently that will take another month. On the other hand, I do have:

• registered myself at the ward office (if you live east of Sendai Station, your ward office is surprisingly far away from the station).
• opened a bank account. This took about two hours, but it was rather straightforward (given the fact that my wife speaks Japanese). Unfortunately, I don't have a Japanese credit card, yet.
• met (most of) the graduate students. Seems to be a great bunch. I look forward to working with them.
• introduced myself a number of times to different groups. I find myself sharing different bits of information each time, just to prevent myself from getting bored.
• bought a six-months bus pass. I'm not an avid driver.
• signed up for a new cell phone plan with a data flat rate. This helped me survive several weeks without a laptop. See also my previous post.
• registered with a new certification authority (KEK) for a grid certificate. Apparently, moving between different certification authorities is not foreseen on the grid. I can currently not delete my old files.
• started to get involved with some of the different research projects that we work on at Tohoku University. I plan to post a bit about each in turn in the coming episodes.
• accepted the job of deputy Linear Collider Detector R&D liaison. This task will most certainly provide material for future blog posts as well. My responsibility is mostly to facilitate communication. To ensure the best achievable performance and cost-effectiveness of the detectors it's important to encourage the widest possible participation in building them. The Detector Baseline Documents for ILD and SiD have been written, but the detector collaborations are still in the process of being formed. Now is the time to get involved with the detector concepts and help shape the face of these collaborations. If you work on particle physics detectors and care about Linear Colliders, please make yourself known.
• not really studied as much Japanese as I had planned. Back to work.

Thoughts about Nigel Lockyer's editorial in Nature

Deciding on the future of particle physics is a complicated process, due to the size of the projects that are being proposed. Nigel Lockyer, director of Fermilab has written an editorial that was recently published in Nature. He outlines some of the questions that our field is facing. As director of the larges particle physics laboratory in the US he should be familiar with large projects.

Unfortunately, this editorial contains a rather indifferent enumeration of  projects that have been proposed at one point in time and ought to be classified rather differently in terms of time scale and scientific merit.
An important consideration that Nigel forgets to mention completely is that each large project comes with its own window of opportunity that depends on a number of factors other than physics. This puts the argument of waiting for results of the upgraded LHC to make a decision on the ILC in a completely different light. There is no ideal point in time to take a decision on the ILC if the LHC finds nothing. Particle physicists will gradually move on to other projects, politicians' focus will shift away from particle physics after years of waiting for news.

This is not a situation we need to get ourselves into. Physicists have worked hard over the past decade and more to put all the pieces in place to take a decision on the ILC in the next couple years. It's quite hard to come up with a scenario in which an LHC discovery in the next five years would invalidate the case for the ILC.
Particle physicists will continue to come up with projects that can be considered at the next step. We will not be short on ideas for future experiments. They will require a foundation that can be laid by the ILC now.