Closer but still working on answer:
http://www.sciencedaily.com/releases/2012/07/120702141716.htm
D.
Tevatron Scientists Announce Their Final Results On the Higgs Particle
ScienceDaily (July 2, 2012) --- After more than 10 years of gathering
and analyzing data produced by the U.S. Department of Energy's Tevatron
collider, scientists from the CDF and DZero collaborations have found
their strongest indication to date for the long-sought Higgs particle.
Squeezing the last bit of information out of 500 trillion collisions
produced by the Tevatron for each experiment since March 2001, the final
analysis of the data does not settle the question of whether the Higgs
particle exists, but gets closer to an answer.
The Tevatron scientists unveiled their latest results on July 2, two
days before the highly anticipated announcement of the latest
Higgs-search results from the Large Hadron Collider in Europe.
"The Tevatron experiments accomplished the goals that we had set with
this data sample," said Fermilab's Rob Roser, cospokesperson for the CDF
experiment at DOE's Fermi National Accelerator Laboratory. "Our data
strongly point toward the existence of the Higgs boson, but it will take
results from the experiments at the Large Hadron Collider in Europe to
establish a discovery."
Scientists of the CDF and DZero collider experiments at the Tevatron
received a round of rousing applause from hundreds of colleagues when
they presented their results at a scientific seminar at Fermilab. The
Large Hadron Collider results will be announced at a scientific seminar
at 2 a.m. CDT on July 4 at the CERN particle physics laboratory in
Geneva, Switzerland.
"It is a real cliffhanger," said DZero co-spokesperson Gregorio
Bernardi, physicist at the Laboratory of Nuclear and High Energy
Physics, or LPNHE, at the University of Paris VI & VII. "We know exactly
what signal we are looking for in our data, and we see strong
indications of the production and decay of Higgs bosons in a crucial
decay mode with a pair of bottom quarks, which is difficult to observe
at the LHC. We are very excited about it."
The Higgs particle is named after Scottish physicist Peter Higgs, who
among other physicists in the 1960s helped develop the theoretical model
that explains why some particles have mass and others don't, a major
step toward understanding the origin of mass. The model predicts the
existence of a new particle, which has eluded experimental detection
ever since. Only high-energy particle colliders such as the Tevatron,
which was shut down in September 2011, and the Large Hadron Collider,
which produced its first collisions in November 2009, have the chance to
produce the Higgs particle. About 1,700 scientists from U.S.
institutions, including Fermilab, are working on the LHC experiments.
The Tevatron results indicate that the Higgs particle, if it exists, has
a mass between 115 and 135 GeV/c2, or about 130 times the mass of the
proton.
"During its life, the Tevatron must have produced thousands of Higgs
particles, if they actually exist, and it's up to us to try to find them
in the data we have collected," said Luciano Ristori, co-spokesperson of
the CDF experiment and physicist at Fermilab and the Italian Istituto
Nazionale di Fisica Nucleare (INFN) . "We have developed sophisticated
simulation and analysis programs to identify Higgs-like patterns. Still,
it is easier to look for a friend's face in a sports stadium filled with
100,000 people than to search for a Higgs-like event among trillions of
collisions."
The final Tevatron results corroborate the Higgs search results that
scientists from the Tevatron and the LHC presented at physics
conferences in March 2012.
The search for the Higgs particle at the Tevatron focuses on a different
decay mode than the search at the LHC. According to the theoretical
framework known as the Standard Model of Particles, Higgs bosons can
decay in many different ways. Just as a vending machine might return the
same amount of change using different combinations of coins, the Higgs
can decay into different combinations of particles. At the LHC, the
experiments can most easily observe the existence of a Higgs particle by
searching for its decay into two energetic photons. At the Tevatron,
experiments most easily see the decay of a Higgs particle into a pair of
bottom quarks.
Tevatron scientists found that the observed Higgs signal in the combined
CDF and DZero data in the bottom-quark decay mode has a statistical
significance of 2.9 sigma. This means there is only a 1-in-550 chance
that the signal is due to a statistical fluctuation.
"We achieved a critical step in the search for the Higgs boson," said
Dmitri Denisov, DZero cospokesperson and physicist at Fermilab. "While
5-sigma significance is required for a discovery, it seems unlikely that
the Tevatron collisions mimicked a Higgs signal. Nobody expected the
Tevatron to get this far when it was built in the 1980s."
The Tevatron is one of eight particle accelerators and storage rings on
the Fermilab site. The largest, operational accelerator at Fermilab now
is the 2-mile-circumference Main Injector, which provides particles for
the laboratory's neutrino and muon research programs.
The CDF and DZero collaborations submitted their joint Higgs search
results to the electronic preprint archive arXiv.org <http://arXiv.org>.
The paper also is available at:
http://tevnphwg.fnal.gov/results/SM_Higgs_Summer_12/
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