Closing in on Higgs Boson Certainty, But “Standard Model Higgs” Remains Distant

A Higgs Boson? – Likely

Higgs boson trails

Higgs boson trails

“The preliminary results with the full 2012 data set are magnificent and to me it is clear that we are dealing with a Higgs boson though we still have a long way to go to know what kind of Higgs boson it is,” said CERN’s CMS Experiment Leader and spokesman Joe Incandela (a professor at the University of California, Santa Barbara) at a Particle Conference in Italia.

This is a bold step forward as, in the midst of last year’s Public Relations circus and media firestorm, Prof Incandela was brave enough to say “We don’t know if its a Higgs boson.”

However, some CERN physicists remain concerned that it is still too early to call the particle detection a “Higgs” until the evidence is totally irrefutable. This is in part due to a slight but persistent excess of gamma-gamma decays. They are not alone.

University of Adelaide’s Professor Anthony Thomas, director of the Adelaide node of the ARC Centre of Excellence in Particle Physics at the Terascale, said “This work adds some confidence concerning one feature of the Higgs, namely its couplings to bosons.

However, the essential missing element is the coupling to fermions and there we still need more information and this may not come until after the shutdown of the Large Hadron Collider — not until 2015.”

CERN itself was rather cautious, notably not claiming a Higgs discovery which would allow Nobel prizes for scientists involved with “the new particle discovered at CERN last year is looking more and more like a Higgs boson. However, more analysis is still required before a definitive statement can be made.”

Higgs Theorists Winning 2010 Sakurai Prize: Kibble, Guralnik, Hagen, Englert, and Brout (Peter Higgs absent)

Higgs Theorists Winning 2010 Sakurai Prize: Kibble, Guralnik, Hagen, Englert, and Brout (Peter Higgs absent)

Instead CERN suggested this might be a “super-Higgs” opening doors to new worlds of physics.

A “Standard Model” Higgs Boson? – Not Yet.

A “Standard Model” Higgs has no Electric Charge, no Spin and no Color Charge (Strong force). Tentative evidence suggests the suspect particle has no Spin. The remaining properties await further testing. (Notably researchers have to comb through about a trillion other impacts of two protons to find each Higgs detection.)

The Higgs boson is supposed to have no spin at all; it is the knuckleball of the subatomic world.” – Dennis Overbye, New York Times reporter.

CERN noted that both CMS and ATLAS detector teams have —

compared a number of options for the spin-parity of this particle, and these all prefer no spin and positive parity. This, coupled with the measured interactions of the new particle with other particles, strongly indicates that it is a Higgs boson.”

It remains an open question whether this is the Higgs boson of the Standard Model … or possibly the lightest of several bosons predicted in some theories that go beyond the Standard Model.”

Spin Tests Tentative

Matt Strassler explained that’s because “…with the data currently available, the measurements are not precise enough to rule out deviations from a Standard Model Higgs as large as 10%, 20%, or even as much as 50% in certain of the particle’s properties.”

Electric Charge and Color Charge Tests

Finding out what kind of Higgs it is will require more data to further tie down the particle’s interactions with other particles, and that will take several years to resolve.” – CERN Press Release

Higgs Background History:

“Dr. Higgs was one of six physicists, working in three independent groups, who in 1964 invented the notion of the cosmic molasses, or Higgs field. The others were Tom Kibble of Imperial College, London; Carl Hagen of the University of Rochester; Dr. Guralnik of Brown University; and Francois Englert and Robert Brout, both of Université Libre de Bruxelles.” – NY Times

References:
Researchers’ Science Paper – “Higgs At Last,” Adam Falkowski, Francesco Riva, Alfredo Urbano

“New results indicate that particle discovered at CERN is a Higgs boson”, CERN Press Office, 14 Mar 2013

New results indicate that new particle is a Higgs boson CERN

CERN Physicists See Higgs Boson in New Particle, NY Times

Matt Strassler: From “Higgs-like Particle” to “Standard Model-like Higgs”

Strong signs Higgs boson has been found: CERN, Reuters

Physicists Find Elusive Particle Seen as Key to Universe, NYT, July 4, 2012, NY Times

Definitely, maybe: evidence grows for positive ID of Higgs boson, The Conversation, Australia

Notes:
An amusing rationale discussed in the new CERN paper is “Invisible Width.”

“In the last of our studies we are going beyond our effective Lagrangian and also allow Higgs decays to invisible particles.”

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