First collisions at 13 TeV as the Large Hadron Colllider restarts


On May 21, 2015 proton beams were collided together in the Large Hadron Collider at the record energy of 13 TeV, as the LHC restarts after extensive upgrades over the past two years.  This is the total energy in the center-of-mass frame, so each beam contains protons of energy 6.5 TeV.  That’s about 6,500 times the rest energy of a proton (roughly 1 GeV), hence the relativistic gamma factor for these protons is about 6,500.

Read the CERN article on this important milestone here.

Higgs boson paper has 5,154 authors

CMS and Atlas, the two big experimental collaborations at the Large Hadron Collider, have joined forces to produce the most accurate determination of the Higgs boson mass to date.  By combining their data sets they obtained

$$ M_H=125.09\pm0.24~GeV$$

for a relative error of about 0.2%.  The paper in Physical Review Letters describing these results has the longest author list ever: 5,154 names.  In the published version, there are 9 pages describing the research and 24 pages of authors and their affiliations.

Read the associated APS Physics Viewpoint article here.

OSAPS Meeting this weekend

This weekend, March 27&28, 2015, will see the Spring Meeting of the Ohio-Region Section of the American Physical Society (OSAPS) at Kent State University.  The focus will be on “The Physics of the QCD Phase Diagram”. All information is online at:

The  conference is a Friday afternoon/Saturday morning event, and free for students. Although there is a set of plenary talks on the main theme of the meetings, many short talks with topics from all areas of physics are scheduled in the parallel sessions.

The OSAPS conferences (one in spring plus one in fall every year) are a great opportunity for undergrads to go a first professional conference.