Teacher interns learn lab work

At the Waubonsee Community College campus in Sugar Grove, Illinois, a group of 22 high school and middle school teachers gathered in pairs to pore over data from CERN’s CMS experiment. Over the course of two hours, they classified more than 100 particle physics events, graphed their data and measured the mass of fundamental particles. As schools are gearing back up for the academic year, these teachers will be able to think about how to bring these real-world science experiences into the classroom.

“I want my students to understand the current questions scientists are working on answering and how they are trying to answer them,” teacher Amanda Whaley said.

Whaley is one of seven high school and middle school teachers who attended the Teacher Research Associates, or TRAC, program located at and funded by Fermilab. TRAC has existed since 1983, but in recent years it has taken on an emphasis on turning those lab experiences into lessons or exercises for students. The two-day workshop in Sugar Grove, organized by TRAC in July and funded by U.S. CMS, brought in not just the program’s participants but also 16 teachers from the local area, educating them about models of different physics lessons and information about the frontier of particle physics research.

The TRAC program itself is a roughly eight-week internship program that paired teachers with mentors at Fermilab to gain experience working in a real physics lab setting. The teachers, who could come from any area of science, math, computer science or technology, each contributed individually to projects around the lab.

Harry Cheung, the head of the program since 2010, said the purpose of TRAC as one of Fermilab’s outreach programs is to educate teachers about what happens at physics labs so students can learn about the real-life applications of the subject matter.

“They get concrete examples of how something is useful,” he said. “They get to talk about the things they’ve done here.”

The teachers were able to jump into major projects at the lab. Whaley worked on research and development for a proposed upgrade to the CMS forward hadron calorimeter, which measures the energy of some particles and detects the presence of others. Another teacher worked on a hand-scanned particle event display study for Fermilab’s NOvA neutrino experiment. Another worked on data acquisition for detectors.

Some of the teachers said their experience in the labs reminded them of skills students will need if they choose fields in science. Whaley said she wants to be sure her students can defend their conclusions when pressed. Another teacher, Elizabeth Wenk, was surprised by the amount of time scientists spent in meetings or writing. She plans to emphasize lab reports and communication more in her class.

And several teachers said they gained fresh perspectives on what it’s like to be a student in physics.

“I’ve been teaching the same material for such a long time,” Wenk said. “I have a newfound appreciation and understanding of students who struggle.”

Particle physics can be difficult to incorporate into a standard curriculum, particularly for middle school teachers. But some can use the material in independent study courses or in more advanced physics classes. Chemistry teachers can go from teaching about molecular scales to even smaller ones when teaching students about atoms. And others have thought of less conventional outlets, such as extracurricular programs.

“I’m really excited about trying out the new things I learned,” Wenk said. “It’s really going to change how I think, and it’s going to have a big impact on the students.”

New result indicates that the flavor and mass correlation may be more complex than previously thought.

Scientists from the NOvA collaboration have announced an exciting new result that could improve our understanding of the behavior of neutrinos.

Neutrinos have previously been detected in three types, called flavors – muon, tau and electron. They also exist in three mass states, but those states don’t necessarily correspond directly to the three flavors. They relate to each other through a complex (and only partially understood) process called mixing, and the more we understand about how the flavors and mass states connect, the more we will know about these mysterious particles.

As the collaboration will present today at the International Conference on High Energy Physics in Chicago, NOvA scientists have seen evidence that one of the three neutrino mass states might not include equal parts of muon and tau flavor, as previously thought. Scientists refer to this as “nonmaximal mixing,” and NOvA’s preliminary result is the first hint that this may be the case for the third mass state.

“Neutrinos are always surprising us. This result is a fresh look into one of the major unknowns in neutrino physics,” said Mark Messier of Indiana University, co-spokesperson of the NOvA experiment.

The NOvA experiment, headquartered at the U.S. Department of Energy’s Fermi National Accelerator Laboratory, has been collecting data on neutrinos since February 2014. NOvA uses the world’s most powerful beam of muon neutrinos, generated at Fermilab, which travels through the Earth 500 miles to a building-size detector in northern Minnesota. NOvA was designed to study neutrino oscillations, the phenomenon by which these particles “flip” flavors while in transit.

NOvA has been using the oscillations of neutrinos to learn more about their basic properties for two years. The NOvA detector is sensitive to both muon and electron neutrinos and can analyze the number of muon neutrinos that remain after traveling through the Earth and the number of electron neutrinos that appear during the journey.

The data also show that the third mass state might have more muon flavor than tau flavor, or vice versa. The NOvA experiment hasn’t yet collected enough data to claim a discovery of nonmaximal mixing, but if this effect persists, scientists expect to have enough data to definitively explore this mystery in the coming years.

“NOvA is just getting started,” said Gregory Pawloski of the University of Minnesota, one of the NOvA scientists who worked on this result. “The data sample reported today is just one-sixth of the total planned, and it will be exciting to see if this intriguing hint develops into a discovery.”

NOvA will take data with neutrinos and antineutrinos over the next several years. With both detectors running smoothly and Fermilab’s neutrino beam at full strength, the NOvA experiment is well positioned to illuminate many of the remaining neutrino mysteries.

The NOvA experiment is funded by the U.S. Department of Energy Office of Science, the National Science Foundation and other institutions worldwide.

For more information on NOvA, visit their website. To read a public presentation on this result, please visit this link.

Fermilab is America’s premier national laboratory for particle physics research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance LLC. Visit Fermilab’s website at http://www.fnal.gov and follow us on Twitter @Fermilab. 

The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit http://science.energy.gov. 

Media contact:

• Andre Salles, Fermilab Office of Communication, media@fnal.gov, 630-840-3351

Science contacts:

• Mark Messier, Indiana University, NOvA co-spokesperson, messier@indiana.edu, 812-855-0236
• Peter Shanahan, Fermilab, NOvA co-spokesperson, shanahan@fnal.gov, 630-840-8378

Jim Olsen of Princeton University, physics co-coordinator for CMS, was addressing a packed CERN auditorium — the same auditorium where the observation of the Higgs boson was announced just slightly less than four years earlier. His status report on the data analysis activities of the CMS Collaboration included a review of the schedule in preparation for the International Conference on High Energy Physics (ICHEP), which was due to start in Chicago on August 4.

I was sitting in the audience, reading the schedule from the projected slides:

• Approvals by July 22 (leaving time for top-ups)
• ARC Greenlight by July 15
• Pre-approval July 1 (10 days from today)
• Freezing by June 24 (this week!)

June 24? A full six weeks before the conference? And today was already June 20. (At least, I thought it was. I had just arrived from the U.S. a few hours earlier, and I was a little confused about the date.) It was going to be a short six weeks. The race to ICHEP was on.

But it wasn’t just a race — we also had what computer scientists call a “race condition.” This occurs when a system depends on the sequencing of events that occur at uncontrollable times. If the events occur in the wrong sequence, you can get the wrong result. In a computer program, it’s a bug that you want to fix. But in real life, race conditions are sometimes unavoidable.

In our case, one event was the approval of results that would be made public. Jim’s bullet points worked backwards from the conference date; my description will describe the approval process in the forward direction.

 

The runup to a result

Any new result from CMS is carefully evaluated before it is made public. There is a prescribed procedure and schedule for this, as described on Jim’s slide, to ensure that there is enough time for proper vetting. All measurements must be thoroughly documented, both in a document to be made available to the public (known in CMS as a “Physics Analysis Summary” or PAS) and another, longer document with more technical details for internal use (an “analysis note”). A data analysis usually evolves as the scientists understand their work better, but at some point it has to be finalized. In CMS, an analysis and its documentation must be “frozen” for an entire week before it can be reviewed.  That gives collaborators enough time to read the documentation and ask questions about it.

After the freeze week, the proponents of a given measurement make a presentation of the work to the relevant “analysis group” within CMS, the population of CMS scientists who are interested in a given set of physics measurements (such as those in top quark physics or Higgs physics or supersymmetry searches). This is a chance for people to ask questions about the analysis in an open forum and identify any possible issues. If the measurement is judged to be in good enough shape, it is “preapproved,” which puts it on track for public release.

 

Analysis of an approval

Once the science analysis is preapproved, a separate committee of CMS scientists is appointed to perform an independent review of the analysis. This Analysis Review Committee (ARC) functions much like peer reviewers for a journal article. They are independent of the scientists who are performing the measurement but have some expertise in the topic such that they can evaluate the work (but aren’t expected to reproduce it themselves). The ARC is given a minimum of two weeks to evaluate the documentation, pose questions to the proponents and iterate with them to resolve any questions they may have. This is also an important phase for shaping message of the documentation that will be released to the public, which is needed to demonstrate to the world that the work is correct.

If the ARC review is successful, the committee “greenlights” the analysis for final approval by the collaboration. The approval presentation is similar to that of the preapproval (including the required one-week freeze of the documentation), but it also emphasizes any changes that were made during the ARC review and sometimes is made in a broader venue than that of the analysis group. If the approval is successful, then the result (and documentation) can be released to the public. Note that at any stage, the analysis can be delayed for further study; Jim’s slide gave the most optimistic schedule for approval. And some physics groups do not even allow the analysts to look at the data until late stages in the approval process to avoid any biases; what is being approved are the analysis procedures.

 

Analysis of an analysis

Jim’s schedule envisioned having all of the approvals complete more than a week before ICHEP, to allow for “top-ups” afterwards. And that was necessary because of the other element of our race condition: Starting in June, the LHC performed extremely well! So well that most of the data to be analyzed would be recorded during the approval process. Here is a graph showing how much data was accumulated by CMS this year, up to July 15, the cutoff date for data to be used for ICHEP:

On June 24, the freeze date for preapprovals, CMS had recorded about 6 inverse femtobarns (fb^-1) of integrated luminosity (which is a measure of the total number of proton collisions). By July 15, CMS would record more than double that data set.

Data cannot be analyzed immediately after it is recorded. There is an extensive validation process to make sure that no detector malfunctions could be mistaken as physics signals. Then the simulations that are so critical for making measurements must be evaluated against the new data. All of the algorithms used to identify particles must perform similarly in the data and the simulation. To achieve this, the simulation must be adjusted, or scaling factors need to be determined to match the two. All of this work must be completed before any physics measurements can be made.

As a result, at the initial freeze point, only about 4 fb^-1 of data were ready for analysis. The data sample to be shown at ICHEP would be triple that size. At the greenlight time, only about 7 fb^-1 could be used. This meant that all of the reviews could proceed under only partial information. All along the way, it was possible that something could go wrong as more data was integrated and that any number of analyses could be thrown off track. It would have been nicer if all of the data had been accumulated well in advance, which would have eliminated the race condition, but that was not what we had on our hands.

This meant that all of CMS was racing around too! Within my own research group at Nebraska, we had people participating in all of these activities — helping to record data, validating the simulation algorithms and reconstruction, performing data analyses, and taking part in analysis reviews. But in the days before the conference, everything came together. On August 4, the first day of the ICHEP conference, I awoke to a fuller email inbox than usual. To my delight, I found that there was one email for each result that CMS was releasing for ICHEP. More would come in during the day, and even through the first few days of the conference. In total, CMS presented about 40 new results that used the complete data set, all fully reviewed and published with the full faith of the collaboration.

If the LHC continues to operate well, we could have as much as three times more data by the end of 2016. Fortunately, we will have a bit more breathing room between then and the next round of major conferences. Then we’ll only be in a race with Nature … and our friends on ATLAS.