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Robin Erbacher | USLHC | USA

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Expecting the end, but still producing!

Friday, September 30th, 2011

Sitting in the CDF collaboration meeting, discussing new and exciting results, while awaiting the end of the Tevatron in only a few hours...

Hello from Fermilab!

Today is a bittersweet day. As you have read in several posts here on the US LHC blog in Quantum Diaries, most recently from Kathy Copic, Michael Schmitt, and Ken Bloom, the Fermilab Tevatron, which for decades held the title of the “Highest Energy Accelerator in the World” (until the LHC began operations in 2009 of course), is ending its historic 28 year run.

This news has also made it into the popular press, such as the BBC, the Chicago Tribune (which discusses the future of Fermilab in brief as well) and the Washington Post, amongst many other publications and blogs.

Milestones?  Yes, there were many!  And while many of us are now working on the CMS and Atlas experiments in particular at the LHC, those of us who also remain on the Tevatron experiments (CDF and D0) are still working and producing results, and we are excited about the measurements we will publish with the final Tevatron datasets.

Robert Craig Group outlines plans for CDF's "final word" on the global search for the Higgs Boson.

Both D0 and CDF are holding collaboration meetings this week ahead of today’s shutdown.  Many current and former collaborators at our two experiments have traveled here from all over the world, even from CERN, to honor the end of an era of tremendous physics productivity and groundbreaking science here in the Chicago suburbs.

I am sitting here in the CDF collaboration meeting, discussing current and future physics results from CDF with my colleagues, while also discussing such topics as future data preservation (so we can access the data to study in the future as needed), and future tours of CDF and its detector as part of Fermilab’s proud legacy.  It is a pretty surreal feeling, to be pushing for exciting results in the next year while discussing the laying-to-rest of a beloved experiment.

Meanwhile, some of our former CDF colleagues, many of whom are now stationed part-time or full-time at CERN, are feeling wistful as well.  They have gathered together as many of our former ranks as they could find in a short period, and sent a send-off photo from all of them at CERN.

Former CDF colleagues gather at CERN for a farewell photo, sending best wishes as the Tevatron prepare to end operations today. (Photo courtesy of Michael Hoch)

One of my colleagues at CMS, Petra Merkel, who I used to work closely with here at CDF, sent the following thoughts along with the above photo:

“I must say that for most of us CDF has always played a special role, even if we have moved on to other experiments. But still now we frequently dwell upon the font memories we all have of our time at Fermilab, and of the very special atmosphere, which was present in CDF! Good luck to all of you, enjoy the party, and hope to see you soon, maybe at CERN.”

We will begin the shutdown ceremony today at 1:45, Chicago daylight time.  If you want to tune in to live video, the link is here. The schedule of events is exciting, but ceremonial compared to the feelings we all have on this day.

At CDF we will gather for a photo, then watch together the shutdown of the Tevatron in the CDF control room by video.  This will be followed by a champagne toast, and some testimonials from those who were around “in the beginning”.  Then CDF, D0, the Accelerator Division, and the whole lab plan to gather in the Fermilab Wilson Hall atrium to celebrate the end of the Tevatron era.  Both CDF and D0 plan further collaboration festivities into the evening, including an appearance by the CDF band.

To the end of an era and the beginning of a new one:  Here’s to continued exciting results from the Tevatron, and the wonderful results to come in the new LHC era…. Cheers!


Where in the World Have I Been?

Friday, July 8th, 2011


View of Mont Blanc from our hotel outside of CERN.

Hello from the airplane back from CERN!

I am just returning from a very productive “CMS week”, which is a collaboration meeting that is typically held three times per year. It was a busy week, and leaving my three-year-old back in California with his grandparents allowed me to stay late at CERN for the usual evening meetings. (As I mentioned previously, U.S. collaborators at the LHC have a hard time attending meetings due to the time shift, so we in the U.S. are fortunate that many meetings are scheduled in the evening, CERN-time.)

The trip to CERN allowed me to catch up with colleagues on CMS, with the latest status reports of the detector performance and detector upgrade plans, and with the latest physics results from CMS, of which there are many! But more importantly for me, it allowed me to attend meetings in person, where the give-and-take is easier (as opposed to video/audio meetings), and to meet personally with many collaborators on my own analyses, some of whom I had never even met in person. [In a large experiment such as CMS, we often find ourselves collaborating with people who have common interests in physics topics, and prior relationships are not necessarily required.]

One of the reasons for my recent silence on this page is that I’m in the midst of the approval process for two different analyses on CMS, which we hope to make public on time for the big European Physical Society (EPS) meeting, which begins on July 21st. (I’d tell you about them but then I’d have to kill you. Grin. Top Secret, no blog leaks allowed! … Okay, okay, I promise I will tell you as soon as they are approved for public.) Time is very short and we are all scrambling to get the proper documentation together, the analyses completed, and to answer all of the questions from our physics group leaders (conveners) and internal reviewers—each analysis has reviewers assigned specifically to ask hard questions, to read all documentation, and to ensure the quality of all the results that are made public from CMS. Having two different analyses, presented in the same meeting in many cases, has been challenging, but it helps that I am working with very strong students, postdocs, and faculty/researchers, so that we can all pull together to help as needed and as schedules allow.

This is a truly exciting time, since everybody is pushing for the all-important summer conferences. Those of us who do not have their analyses ready for the first big meeting have several others in August to aim for: Lepton-Photon 2011 (Mumbai, India) and Supersymmetry 2011 (Fermilab, IL)  are two of the large ones.

The other reason for my silence: Before I traveled to CERN, I had somehow made three trips to Fermilab for research purposes during May and June (not to mention a quick vacation to Mexico with my parents, shhh!), and a trip to Notre Dame for the US CMS Collaboration Meeting. (Ken, of course, beat me to the blog on that one!)

Where’s Waldo? Ken Bloom hand-waving during his presentation at the US CMS Collaboration Meeting in Notre Dame.

Postdoc Jason Slaunwhite (Notre Dame) and Prof. Tulika Bose (Boston University) in discussions over coffee at the US CMS Collaboration Meeting.

During one of my Fermilab trips, we had our collaboration meeting for the CDF experiment at Fermilab’s Tevatron. It is an exciting time there, too.  We have extremely large datasets that we are exploiting with very mature, sophisticated analysis tools that have been developed over the period of CDF Run 2 (2001-2011). My CDF student, David Cox, was in the process of approving his thesis result on our latest search for “tprime”, a hypothetical, massive fourth-generation (or other) top-like quark. We hope to submit our final paper on this subject from CDF in a couple of weeks, so that has also happily occupied my time.

Its an interesting position to be in: straddling the Tevatron at its peak, and the LHC at its start, because at the Tevatron we are competing with the new results from the LHC that will come out soon, which will potentially outdo many of our Tevatron searches for new massive particles, simply because of the large increase in collision energy at the LHC over the Tevatron. In one case I’m working on the same analysis on both experiments, rushing the CDF paper to beat the CMS result that I’m also spending so much time on.

My most recent trip to Fermilab coincided with my husband, John Conway’s, week-long shift duty on CDF. We went together and brought our son. During the week I was able to help four of our UC Davis graduate students on CMS arrive and get settled for their partial summer stay at the LHC Physics Center (LPC). We at UC Davis have found the LPC at Fermilab to be an excellent place to get our students and sometimes our postdocs started in familiarizing themselves with CMS, with group meetings, analysis tools, and so forth. There are plenty of experts stationed at Fermilab (some Fermilab staff, some from other universities) that it is easy for them to get technical questions about the software or detector answered. The LPC has sponsored software tutorials at least once a year that the students can work with at the start. There are also a few hardware projects based at Fermilab that some in our group have been involved in, and we are continuing to collaborate with future efforts that will be based at the lab.

Four of our new CMS students settling in to the UC Davis cubicle at the LPC at Fermilab. Left-to-right: Francesca Ricci-Tam, Rachel Houtz, Matt Caulfield, Britney Rutherford.

With the excitement from both the finale of the Tevatron era, and the beginning of the LHC, there are too many places to be at once, but I’m happy to spend time on it all!

And next… I go camping in California, for some needed r&r before the end of the summer conference push.   See you back here soon!


This just in! Congratulations!

Saturday, May 7th, 2011



Congratulations goes out to fellow US LHC Blogger Prof. Sarah Demers for just being awarded the Department of Energy’s Early Career Award.  The announcement is naturally featured prominently on the website of her home institution, Yale University Physics Department.  This award has recently replaced the long-standing DOE Outstanding Junior Investigator Award (OJI), which has awarded grants to promising junior faculty members from 1978-2008, an impressive run!  The new Early Career award and has brought the previous National Science Foundation’s Early Career Award and DOE OJI awards together to a more similar format and award level.

These awards can mean a tremendous amount to a new faculty member in particle physics. I was fortunate enough to receive an OJI from the DOE, and fellow blogger Prof. Ken Bloom was fortunate to receive a Career Award from NSF, when we were both new junior professors.  This allowed us both to support perhaps a graduate student and part of a postdoc’s salary as well as our own summer salaries while we established our research programs as new faculty members.  Now Sarah has earned a peer-reviewed grant, which is a major milestone for a new professor, and which enables her to proceed with her successful research program without relying on university start-up funds (which eventually dry up).  Here’s to Sarah’s future success!

Photo by Waldo Jaquith


The April Meeting

Tuesday, May 3rd, 2011

2011 American Physical Society April Meeting, Anaheim, CA












Hello from Anaheim, California!

Yes it is that time of year: the April APS (American Physical Society) meeting.   It has become tradition that each year in April, the membership of the APS in the Division of Particles and Fields meets together with the membership of somewhat related divisions: Astrophysics, Nuclear Physics, Computational Physics, Physics of Beams, and Plasma Physics.  I find these meetings particularly broadening, as I can sometimes hear about topics that I do not necessarily get exposure to all of the time in my day-to-day work in hadron collider physics.  In fact, some of the more entertaining session titles I have seen here include “Black Holes: Nature’s Ultimate Spinmeisters, “Much Ado about Nothing: The Quantum Vacuum, and “So Many Dynamos: Flow-Generated Magnetic Fields in Nature, in the Computer, and in the Lab.  (I believe the latter also wins for longest session title, barely beating out the more straightforward and understandable– for me at least– “Precision Measurements, Fundamental Symmetries, and Tests of the Standard Model“.)

Other interesting topics at this meeting, such as “Nuclear Weapons at 65“, “The Status of Arms Control“, and “Best Practices in K12 Physics Teacher Education Programs”  are a result of the inclusion of the Forum on Society, the Forum on Education, and other such broad-interest topics in this meeting.  Yet in my opinion one of the most important roles that these APS (and the Divisional) meetings play is to provide a forum for students to give 10-15 minute parallel session talks on their own analysis.  At other conferences it is rare to have single-result talks rather than summaries, and summaries are generally given to more senior people.  This is often the first (and sometimes only) chance a graduate student has to prepare a talk for a non-expert (non-working group) audience. With these talks they learn to prepare a summary of their work with an appropriate level of detail, omitting jargon, timing it properly, and most importantly, stating the big picture (the context) of their work, as well as the bottom line.  When I was a graduate student I found the APS meetings to be valuable training in public presentations.  For this reason I sent my student, David Cox, from Fermilab to Anaheim to present his own recent work on our searches for a massive top-like, perhaps 4th generation, quark (“tprime“) at the Tevatron.  He has actually had practice giving talks at other meetings, but this is still good experience for him.  He is also attending useful career sessions for graduate students as well.

My own main purpose for attending this meeting has been to present results in an invited plenary talk on Top Quark Physics, which I delivered on Saturday morning during one of several plenary sessions. My talk focused on results from the Tevatron‘s CDF and D0 experiments, not from the LHC.  This was in fact a tall order for a 30 minute talk, since the large datasets from Run 2 of the Tevatron, together with the years of experience with these detectors and analysis tools, have meant a plethora of interesting and innovative results from CDF and D0 constantly being released to the public.  Measurements of the top quark mass for example, the all-important electroweak parameter, have reached sensitivities to less than a percent relative, much better than the Run 2 goal of 3 GeV.  Yet some relatively new measurements, such as the studies of the difference between the mass of the top quark and the mass of the anti-top quark (expected to be zero if CPT is conserved), still have very little statistical sensitivity due to the difficulty of the measurement.

The measurements of the forward-backward asymmetry AFB in top pair production have received attention earlier this year not only because both CDF and D0 continue to see a 2-sigma (or more) discrepancy with the theoretical predictions, but also because there appears to be a dependence on the invariant mass of the top pair system, which could imply the existence of new high-mass particles decaying to top quarks.  (The original AFB measurement at the Tevatron was actually performed by my postdoc, Tom Schwarz — CDF Top Group Convener, when he was a thesis student at U. Michigan, and we’ve continued to study this anomaly with our collaborators from Michigan since then.)  This measurement has generated quite a bit of theoretical interest so I was happy to take some time for these measurements,  along with many other interesting topics, such as whether the top quark really has an exotic -4/3 charge instead of the +2/3 charge of the Standard Model.

While the Tevatron is producing spectacular results in the area of top quark physics (and many other areas), the reality is that even at half of the design energy, the LHC will soon outshine the Tevatron for most measurements.  The production cross section (production rate) for top pairs at the 7 TeV LHC is much greater than at the ~2 TeV Tevatron due to the higher energies available.  Measurements of things like the top-antitop mass difference, or the top quark charge, will soon have better sensitivity at the LHC.  It may take a little longer for the LHC experiments to catch up in the area of the precision top mass measurement, mainly due to the complicated systematic uncertainties that need to be taken into account, but eventually the Tevatron will be bested there as well.  The AFB measurement will be difficult to challenge or improve upon at the LHC, however, since the asymmetry is thought to result from quark-antiquark annihilation, which is much more dominant at the Tevatron’s proton anti-proton collider than the proton-proton collider of the LHC.  For that we will still have more to say from the Tevatron’s final datasets.

Giving this talk has been a nice way for me to pay tribute to the amazing results from dedicated analysts at the Tevatron over the ~16 years since the top quark was discovered there. Although the Tevatron is scheduled to close down later this year , I cannot help be excited about the new projects I and many others are working on at the LHC.  Some are topics that we could barely touch at the Tevatron such as boosted top quarks, which I am currently working on at CMS.  (See Flip Tanedo’s recent post on this subject from Atlas.)  Some, like our tprime searches, have shown hints of excess events on the tails of the distribution, so we are excited to see whether this excess grows at the LHC.  Regardless of the particular topic, we are all approaching the LHC with the knowledge we have gained from the Tevatron, and are excited to continue to explore the particle frontier with the greater rates and energies of the LHC.  And we are definitely on the look-out for discoveries!



Good evening, good night, and good morning!

Wednesday, April 20th, 2011

Night and Day, Robert Weigand


My first note’s byline is UC Davis:

Good evening from California!

Well, it’s evening here (10:30 pm), but it’s already tomorrow on the east coast of the U.S., and in fact already time to wake up at CERN.  Here is where I usually face my conundrum: Do I stay awake and watch for the first email reports on the activities at the LHC?  Should I wait for our postdocs and students who live at CERN to respond to my emails?  If I go to sleep, what will I miss?

Unfortunately, I have an 8:00 am video meeting tomorrow, in which our postdocs on the CDF experiment at Fermilab are presenting an introduction to our new analysis, searching for signs of light dark matter in the CDF data.  (CDF has been in the news recently for an interesting result that has previously been discussed by Flip Tanedo and Michael Schmitt.)

The CDF meeting is followed by a 9:30 am video meeting with fellow CMS colleagues who are working on searches for fourth generation quarks, and it looks like one of our CMS postdocs may have something short to present there.  But this isn’t so bad: on Fridays my first meeting is at 6:30 am, which is 3:30 pm in Geneva, and many meetings are earlier than that, so I usually have to miss them. I am grateful that at least for tomorrow’s CMS meeting at 9:30, those at CERN are willing to have it at 6:30 pm, their time, which for me means I can at least get the kid to daycare and get to work formally before it begins.

Of course, even after these early meetings, the California workday still lies ahead for me, and it sometimes turns in to a very long day.  But the time is worth it— as you have gathered in these blogs, there are lots of exciting things going on in the world of particle physics these days, and I wouldn’t want to miss it!

With that, I’d better say “good night” (*yawn*) and get some sleep… the sun is fast approaching.


Day and Night, Google Earth