Synopsis: W Marks the Spot

Two experimental collaborations at Fermilab report a new measurement of the W boson mass that leads to a better prediction of the mass of the Higgs boson.
Synopsis figure

Long before experimentalists at the Large Hadron Collider reported hints of the Higgs boson in particle collisions (see 13 March 2012 Viewpoint), physicists knew roughly what the Higgs mass had to be from measurements of the W boson. That’s because according to the standard model, the W boson, one of the particles that mediates the weak interaction, can emit a virtual Higgs boson and reabsorb it, which alters the W boson’s mass. The mass of the W boson also shifts due to a virtual process containing a top and bottom quark. So with a precise measurement of the W mass, and a good measurement of the top quark mass, it is possible to predict the mass of the Higgs boson.

Now the CDF and D0 Collaborations at Fermilab are each reporting in Physical Review Letters their new measurements of the W mass using datasets containing a total of about 2 million W decays to an electron or muon and a neutrino. By analyzing the kinematics from this large sample, the two experiments achieve a combined precision of about 0.02%.

These new values narrow the allowed range in top-W mass space. The band of top-W masses corresponding to the 115–127 GeV range of Higgs masses, allowed by direct searches, goes right through the allowed region determined by CDF and D0. If the LHC does find the Higgs boson in the 115–127 GeV mass window, it will be yet another success for the predictions of the standard model. – Robert Garisto


Announcements

More Announcements »

Subject Areas

Particles and Fields

Previous Synopsis

Chemical Physics

Only on Paper

Read More »

Next Synopsis

Semiconductor Physics

Nanowire Lasing Explained

Read More »

Related Articles

Viewpoint: Connecting the Bright and Dark Sides of Galaxies
Cosmology

Viewpoint: Connecting the Bright and Dark Sides of Galaxies

A universal law shows that the rotation of a disk galaxy is determined entirely by the visible matter it contains, even if the disk is mostly filled with dark matter. Read More »

Viewpoint: Cosmic-Ray Showers Reveal Muon Mystery
Particles and Fields

Viewpoint: Cosmic-Ray Showers Reveal Muon Mystery

The Pierre Auger Observatory has detected more muons from cosmic-ray showers than predicted by the most up-to-date particle-physics models. Read More »

Synopsis: Making Monopoles with Waves
Particles and Fields

Synopsis: Making Monopoles with Waves

Magnetic monopoles—theorized particles with only one magnetic pole—might possibly be created by wave-wave collisions. Read More »

More Articles