Livingston plot

Dear editors:

Could someone please explain to me the vertical scale on the Livingston plot on page 30 of the October 2009 issue? I can't make any sense out of it at all. Where was the 2-TeV storage ring in 1970? Or the 300-TeV machine in the years before 1990? Don't we wish there were a 100,000-TeV machine scheduled to come on line by 2010.
Matt Moulson, INFN/Laboratori Nazionali di Frascati

Dear editors:

You might want to re-check the vertical scale on the Livingston plot on page 30 of the October 2009 issue.
Jim Brau, University of Oregon

The editors respond:

We adapted the Livingston plot from the 2001 Snowmass Accelerator R&D report. Although we kept the scale the same, we unfortunately omitted the text from the Snowmass report that explains the units: “Energy of colliders is plotted in terms of the laboratory energy of particles colliding with a proton at rest to reach the same center of mass energy.” Using these units, the energy of collisions at the Large Hadron Collider is nearly 100,000 TeV.