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Is the Higgs
Boson
the God Particle or the Goddamn Particle?
January
11, 2012 -- Part 2
In Part 1 of this newsletter we discussed why theorists proposed the
Higgs boson and what function they expect it to fulfill.
Now, how goes the experimental search?
Finding the Higgs boson was the primary justification for building
CERN’s $10 billion particle accelerator, the LHC (Large Hadron
Collider), near Geneva, Switzerland. The Higgs was so intensely
promoted that the media and public now await the “God Particle’s”
discovery almost as a Second Coming. Since the last major U.S. particle
accelerator was shut down in September, the LHC is the only chance to
find the Higgs. Over 5000 physicists from about 200 institutions and 40
countries are working on two detectors, ATLAS and CMS, at the LHC. They
have so far combed through 400 trillion particle collisions, looking
for something new. Below is a computer reconstruction of the debris
from one such collision, an “event”, showing two high-energy photons
(red lines) plus a myriad of other particles.
Unfortunately,
Higgs bosons do not have a unique signature — they are thought to decay
in many different ways, all of which can occur through numerous
Higgs-less processes. The only hope is to look for a larger than
expected number of certain types of events, and see if these seem to
come from a new type of particle, one with a mass never seen before.
All this is made far more difficult by the complexity of events at this
high energy, as seen above. In December, ATLAS and CMS jointly
published some tantalizing data, shown below.
The mass of a
potentially new particle is plotted on the horizontal axis, and the
number of events is plotted on the vertical axis. The dark jagged line
shows the number of observed events, while the dotted line shows the
number of events expected without Higgs.
The data aren’t
definitive. The data do seem to have more events than expected at
masses between 110 and 180, which could be evidence for Higgs. But,
there are also excess unexplained events between 190 and 300, and more
above 490. And there are far fewer than expected events between 300 and
420; it’s very difficult to explain finding fewer events than expected.
I’ve seen innumerable graphs of high-energy physics data — the most
convincing graphs showed data that nicely matched expectations from
known processes with an additional prominent spike in a definite
position. These data aren’t that convincing – at least not yet.
ATLAS and CMS will
continue taking data. With increased statistical precision, we hope the
Higgs question will be settled before the end of 2012.
If ATLAS and CMS
don’t find the Higgs, some Higgs enthusiasts will no doubt fall back on
theorists’ favorite refrain: “It’s really there, but just too heavy for
current accelerators to produce.” And, even if scientists prove the
Higgs does not exist, have no fear — particle masses will not
disappear. Nor will theorists be at a loss for other explanations.
Numerous Higgs-less theories abound, including: “technicolor”; extra
dimensions with five-component gauge fields; Abbot-Farhi composite
vector bosons; top quark scalar condensates; and a “braid model”
compatible with loop quantum gravity. Don’t ask.
If ATLAS and CMS
do find the Higgs, a whole new field of research will open: unraveling
all its properties, including why it interacts so differently with each
of the currently known particles. This could develop into a great
discovery, and perhaps even live up to its hype.
* * * * * * * * *
* * * * * * * * * * * * * * * * * * * * * * * * * * *
* * * * * * * * * * * * * * * *
Dr Robert
Piccioni,
Author of "Everyone's
Guide to Atoms, Einstein, and the Universe",
Can Life Be
Merely An Accident?"
and "A
World Without Einstein"
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