First things first

Examining events in which only two jets are formed is a powerful way to study the uniformity of how the CMS detector responds to energy deposited within it.

Editor's note: This is the first installment of the monthly CMS Result of the Month.

The recent announcement of the startup schedule of the LHC prompts scientists to check one more time the sorts of things a particle detector needs to measure accurately. Scientists need to understand the detector well so that they can exploit the information it records to draw clear conclusions.

The LHC will collide counter-rotating beams of protons. Protons are tiny particles found in the center of atoms. A proton is as small compared to a germ as a germ is to the entire Earth. Within protons are even smaller particles called quarks and gluons (collectively called partons). The strong nuclear force affects partons. As its name suggests, this force is much stronger than any of the other subatomic forces. Consequently, what we expect to find at the center of a detector, where the beams collide, are enormous numbers of partons being knocked out of the collisions between two protons. In fact, ordinary parton collisions occur thousands to millions of times more frequently than more exciting physics. Thus, a deep understanding of parton scattering is crucial in making sure that we don't mistake an ordinary collision for something more interesting. In addition, scientists frequently observe additional partons in collisions in which more exotic things occur.

However, scientists never observe bare partons. These particles are converted to jets as they exit a collision. A jet is a collection of particles all traveling more-or-less in the same direction. By simulating events in which only two jets are formed, the CMS experiment has carefully studied its ability to accurately measure the energy of jets. In this situation, the two jets are expected to exactly balance. By comparing the energy of the two jets recorded in the detector, scientists can determine how uniformly the detector responds to the jets. Using the simulation, CMS scientists estimate that they will need to correct for as much as a ±20 percent variation in response across the entire CMS detector. While this estimate will require beam data to confirm, scientists also were able to work out how much data they will need to remove these non-uniformities. Even at the low beam intensities expected for early running, CMS scientists estimate they can take the necessary data in about a week.

-- Don Lincoln

Two Fermilab scientists have recently carefully studied the uniformity of the CMS detector.

The Fermilab LHC Physics Center (LPC) provides a physical location at which U.S. CMS physicists can collaborate. At a recent "JTERM" training session, 51 lecturers trained 142 young physicists in many topics necessary to understand the deluge of data expected provided to CMS soon. Without the experience and time commitment of the lecturers, trainings like this would be impossible.

Chuck Schmidt retires today

Chuck Schmidt stands in front of the Cockcroft Walton, the pre-accelerator, which produces H- ions. Schmidt was instrumental in implementing the H- design.

When Chuck Schmidt was 2-years-old, he stuck his mother's keys in an electrical outlet.

"My cry alerted the whole neighborhood," Schmidt said.

The shock might have deterred most children from tinkering with electronics, but Schmidt attributes his love for science to that experience. After 40 years of working to get and keep Fermilab's Linac and accelerators running smoothly and efficiently, Schmidt will retire today.

Schmidt's career at Fermilab began in 1969 when he joined the Main Ring Group. He remembers working with a team to steer the magnets in order to get the first beam around the main accelerator. He also worked as operations chief, close to the equivalent of today's run coordinators.

But Schmdt, ID number 432, is best known for the H- source, the machine that isolates and ionizes hydrogen atoms.

"He is pretty much single-handedly responsible for the H- sources at the laboratory," said Larry Allen, an engineering physicist in the Accelerator Division who has worked with Schmidt for the past 37 years.

Schmidt calls the conversion from proton beam to H- in the Linac a highlight of his career.

"I saw that the Booster wasn't working well with protons and I looked at results from Argonne National Laboratory, which had developed the first H- source," Schmidt said.

Schmidt also worked on the ion source for the Loma Linda project and most recently worked on electron cooling. He also headed the Linear Accelerator Department from 1989 to 1994, and then served as the deputy head of the same department when it was renamed the Proton Source Department, until 2001.

But what colleagues reflect on is Schmidt's personality. "Chuck has always been the most conscientious guy I've ever met," Allen said. "He was very protective of his employees."

Schmidt plans to travel with his wife, Judy, and work around their Naperville home during his retirement. He also has a guest scientist appointment, and hopes to come back to the laboratory frequently to work on the High Intensity Neutrino Source, among other things.

"I do feel like I've accomplished a lot in the 40 years I've been here," Schmidt said. "It has been a tremendous enjoyment."