Wednesday, October 30, 2013

Signal At 140 GeV Was Flawed Analysis and Random Chance

In March 2011, the CDF experiment published data tending to show at high statistical significance a signal of a particle of about 140 GeV other than the Higgs boson in W boson-W boson (i.e. diboson) decays at their collider.

This seemed to provide possible high energy physics corroboration of the 135 GeV "Fermi line" seen in the Fermi telescope experiment in 2010 (also somewhat doubtful at 2.2 sigma as of November 2012, before a rigorous look elsewhere effect, but touted by some as a signal of dark matter annihilation).

Now, a new study of ZZ decays, more data, and the discovery of two separate analysis flaws in the previous study that combined with each other in an unexpected way, have shown that there is no new particle with a mass of 140 GeV in the CDF data after all.

Once again, the boring old Standard Model prevails.


In similar news, the maximum size of the electron dipole moment, which is expected to be tiny or zero in the Standard Model, but much higher in many preon models of the electron where it is composite, has been further constrained by experiment:

A group of atomic physicists, called the ACME collaboration, has performed the best search so far for the electric dipole moment (EDM) of the electron. Unfortunately they didn’t find the EDM, but the limit

|de| < 8.7 10-29 e cm is 12 times stronger than the previous one. While this is still a billion times larger than what is expected in the Standard Model of particle physics . . . there are various types of as-yet unknown particles and forces that could easily produce a much larger electron EDM, through new violations of T symmetry (or, almost equivalently, CP symmetry). These effects could have been large enough to have been discovered by this experiment, so those types of possible phenomena are now more constrained than before. Fortunately, there’s more to look forward to; the method these folks are using can eventually be improved by another factor of 10 or so, meaning that a discovery using this technique is still possible.


andrew said...

Comment from Jester on the EDM here and from earlier this year here.

andrew said...

Jester, with numerous caveats, explains that "the simplest explanation of the current data is that there are no superpartners up to at least ~10 TeV."