Scientists of the Collider Detector at Fermilab (CDF) in Batavia, IL at the Department of Energy’s Fermi National Accelerator Laboratory announced yesterday the world’s most precise measurement by a single experiment of the mass of the W boson, the carrier of the weak nuclear force and a key parameter of the Standard Model of particles and forces. The new W-mass value leads to an estimate for the mass of the yet-undiscovered Higgs boson that is lighter than previously predicted, in principle making observation of this elusive particle more likely by experiments at the Tevatron particle collider at Fermilab.

The CDF is an international experiment of 700 physicists from 61 institutions and 13 countries. A group from Wayne State University joined the CDF experiment in 2001 and has played a leading role in the operation of the CDF experiment and analysis of the data.

Professors Paul Karchin and Robert Harr of the Wayne State University Department of Physics and Astronomy, along with Mark Mattson, research scientist in Physics, Alfredo Gutierrez, research engineer in Physics and graduate students Nagesh Kulkarni, Shalhout Shalhout and Larry Tarini, are members of the CDF experiment.

The WSU group maintains the precise calibration of the calorimeter electronics, a crucial component of the measurement. A good simulation is also vital for the measurement, and Dr. Harr leads the development of the simulation.

According to Dr. Harr, “This result is an important signpost for future discoveries. It tells us that the odds favor a light Higgs boson, and supersymmetry is a good bet. The first measurement of a light Higgs or supersymmetric particle could come from the experiments at Fermilab or almost certainly from the experiments at the large hadron collider.”

“If the Higgs particle exists we’ve almost cornered it,” said Dr. Karchin. “And if it doesn’t exist, that would be very exciting as well.”

Scientists working at the Collider Detector at Fermilab measured the mass of the W boson to be 80,413 +/- 48 MeV/c^2, determining the particle’s mass with a precision of 0.06 percent. Calculations based on the Standard Model intricately link the masses of the W boson and the top quark, a particle discovered at Fermilab in 1995, to the mass of the Higgs boson. By measuring the W-boson and top-quark masses with ever greater precision, physicists can restrict the allowable mass range of the Higgs boson, the missing keystone of the Standard Model.

The CDF result is now the most precise single measurement to date of the W boson mass. Combining the CDF result with other measurements worldwide leads to an average value of the W-boson mass of 80,398 +/- 25 MeV/c^2.

The Wayne State group plans to follow-up with participation in experiments at the large hadron collider (LHC) at the European particle physics laboratory CERN, and the international linear collider (ILC). The LHC will begin operating later this year. The ILC is in the planning phase and is envisioned as a machine for making precise measurements of the new discoveries.

For further information, please see the full press release from Fermilab at http://www.fnal.gov/pub/presspass/press_releases/LighterHiggs.html.

For photos, please visit http://www.fnal.gov/pub/presspass/images/LighterHiggs-images.html.