Something is wrong with dark matter

Photos: Secrets of the 'God particle'
Studying the 'God particle' – British
physicist Peter Higgs, right, speaks with Belgian physicist Francois
Englert at a press conference at Geneva's CERN facility in 2012. Higgs
and Englert shared the 2013 Nobel Prize in Physics for describing an
explanation for why particles have mass. They independently published
papers on this topic in 1964.
Hide Caption
5 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – CERN's
Globe of Science and Innovation exhibition center and surface
buildings, which provide access to the Large Hadron Collider, can be
seen near Geneva, Switzerland. CERN Director General Rolf Heuer said,
"There is much benefit in combining the results of large experiments to
reach the high precision needed for the next breakthrough in our field.
By doing so, we achieve what for a single experiment would have meant
running for at least 2 more years."
Hide Caption
6 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – Teams
from ATLAS and CMS Collaborations combined their research to obtain
their results. "Combining results from two large experiments was a real
challenge as such analysis involves over 4,200 parameters that represent
systematic uncertainties," said CMS Spokesperson Tiziano Camporesi.
"With such a result and the flow of new data at the new energy level at
the LHC, we are in a good position to look at the Higgs boson from every
possible angle."
Hide Caption
7 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – The
particle accelerator magnets of the LHC are shown at the underground
test facility at CERN near Geneva. Many scientists dislike the term "God
particle," even though it's become popular in the media. The nickname
came from the title of a book by Leon Lederman, who reportedly wanted to
call it the "Goddamn Particle" since it was so hard to find.
Hide Caption
8 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – In
the preface to a 2014 book, astrophysicist Stephen Hawking wrote he was
worried that Higgs boson might turn unstable and lead to the end of
everything. The "universe could undergo catastrophic vacuum decay, with a
bubble of the true vacuum expanding at the speed of light," Hawking
wrote. "This could happen at any time and we wouldn't see it coming."
Not to worry too much. Hawking added that such a scenario would require a
"particle accelerator that ... would be larger than Earth, and is
unlikely to be funded in the present economic climate."
Hide Caption
9 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – Three
years ago, scientists in Geneva, Switzerland, announced they had proved
the existence of the so-called "God particle" known as Higgs boson -- a
never-before-seen subatomic particle long thought to be a fundamental
building block of the universe. This year, researchers from two
different teams combined their measurements of the particle, providing
an unprecedented picture of Higgs boson's production, decay and
interaction with other particles. Click through the gallery for more.
Hide Caption
1 of 9

Photos: Secrets of the 'God particle'
This
graphic shows traces of the collision of particles from an experiment
at the Compact Muon Solenoid (CMS) -- a large particle detector in
Geneva. The Standard Model of particle physics lays out the basics of
how elementary particles and forces interact in the universe. But the
theory crucially fails to explain how particles actually get their mass.
Particles, or bits of matter, range in size and can be larger or
smaller than atoms. Electrons, protons and neutrons, for instance, are
the subatomic particles that make up an atom. Scientists believe that
the Higgs boson is the particle that gives all matter its mass.
Hide Caption
2 of 9
![An image of the Compact Muon Solenoid (CMS) experiment. "The Higgs boson is the last missing piece of our current understanding of the most fundamental nature of the universe," Martin Archer, a physicist at Imperial College in London, told CNN. "Only now with the LHC [Large Hadron Collider] are we able to really tick that box off and say 'This is how the universe works, or at least we think it does'."](http://i2.cdn.turner.com/cnnnext/dam/assets/131205161618-02-cern-hp-video.jpg)
Photos: Secrets of the 'God particle'
An
image of the Compact Muon Solenoid (CMS) experiment. "The Higgs boson
is the last missing piece of our current understanding of the most
fundamental nature of the universe," Martin Archer, a physicist at
Imperial College in London, told CNN. "Only now with the LHC [Large
Hadron Collider] are we able to really tick that box off and say 'This
is how the universe works, or at least we think it does'."
Hide Caption
3 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – Higgs
boson research takes place at the Large Hadron Collider -- a circular
tunnel located 100 meters (328 feet) underground. It uses a particle
accelerator to collide protons at extreme speeds. By combining their
data, researchers found that there are different ways to produce a Higgs
boson, and different ways for a Higgs boson to decay to other
particles.
Hide Caption
4 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – British
physicist Peter Higgs, right, speaks with Belgian physicist Francois
Englert at a press conference at Geneva's CERN facility in 2012. Higgs
and Englert shared the 2013 Nobel Prize in Physics for describing an
explanation for why particles have mass. They independently published
papers on this topic in 1964.
Hide Caption
5 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – CERN's
Globe of Science and Innovation exhibition center and surface
buildings, which provide access to the Large Hadron Collider, can be
seen near Geneva, Switzerland. CERN Director General Rolf Heuer said,
"There is much benefit in combining the results of large experiments to
reach the high precision needed for the next breakthrough in our field.
By doing so, we achieve what for a single experiment would have meant
running for at least 2 more years."
Hide Caption
6 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – Teams
from ATLAS and CMS Collaborations combined their research to obtain
their results. "Combining results from two large experiments was a real
challenge as such analysis involves over 4,200 parameters that represent
systematic uncertainties," said CMS Spokesperson Tiziano Camporesi.
"With such a result and the flow of new data at the new energy level at
the LHC, we are in a good position to look at the Higgs boson from every
possible angle."
Hide Caption
7 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – The
particle accelerator magnets of the LHC are shown at the underground
test facility at CERN near Geneva. Many scientists dislike the term "God
particle," even though it's become popular in the media. The nickname
came from the title of a book by Leon Lederman, who reportedly wanted to
call it the "Goddamn Particle" since it was so hard to find.
Hide Caption
8 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – In
the preface to a 2014 book, astrophysicist Stephen Hawking wrote he was
worried that Higgs boson might turn unstable and lead to the end of
everything. The "universe could undergo catastrophic vacuum decay, with a
bubble of the true vacuum expanding at the speed of light," Hawking
wrote. "This could happen at any time and we wouldn't see it coming."
Not to worry too much. Hawking added that such a scenario would require a
"particle accelerator that ... would be larger than Earth, and is
unlikely to be funded in the present economic climate."
Hide Caption
9 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – Three
years ago, scientists in Geneva, Switzerland, announced they had proved
the existence of the so-called "God particle" known as Higgs boson -- a
never-before-seen subatomic particle long thought to be a fundamental
building block of the universe. This year, researchers from two
different teams combined their measurements of the particle, providing
an unprecedented picture of Higgs boson's production, decay and
interaction with other particles. Click through the gallery for more.
Hide Caption
1 of 9

Photos: Secrets of the 'God particle'
This
graphic shows traces of the collision of particles from an experiment
at the Compact Muon Solenoid (CMS) -- a large particle detector in
Geneva. The Standard Model of particle physics lays out the basics of
how elementary particles and forces interact in the universe. But the
theory crucially fails to explain how particles actually get their mass.
Particles, or bits of matter, range in size and can be larger or
smaller than atoms. Electrons, protons and neutrons, for instance, are
the subatomic particles that make up an atom. Scientists believe that
the Higgs boson is the particle that gives all matter its mass.
Hide Caption
2 of 9
![An image of the Compact Muon Solenoid (CMS) experiment. "The Higgs boson is the last missing piece of our current understanding of the most fundamental nature of the universe," Martin Archer, a physicist at Imperial College in London, told CNN. "Only now with the LHC [Large Hadron Collider] are we able to really tick that box off and say 'This is how the universe works, or at least we think it does'."](http://i2.cdn.turner.com/cnnnext/dam/assets/131205161618-02-cern-hp-video.jpg)
Photos: Secrets of the 'God particle'
An
image of the Compact Muon Solenoid (CMS) experiment. "The Higgs boson
is the last missing piece of our current understanding of the most
fundamental nature of the universe," Martin Archer, a physicist at
Imperial College in London, told CNN. "Only now with the LHC [Large
Hadron Collider] are we able to really tick that box off and say 'This
is how the universe works, or at least we think it does'."
Hide Caption
3 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – Higgs
boson research takes place at the Large Hadron Collider -- a circular
tunnel located 100 meters (328 feet) underground. It uses a particle
accelerator to collide protons at extreme speeds. By combining their
data, researchers found that there are different ways to produce a Higgs
boson, and different ways for a Higgs boson to decay to other
particles.
Hide Caption
4 of 9

Photos: Secrets of the 'God particle'
Studying the 'God particle' – British
physicist Peter Higgs, right, speaks with Belgian physicist Francois
Englert at a press conference at Geneva's CERN facility in 2012. Higgs
and Englert shared the 2013 Nobel Prize in Physics for describing an
explanation for why particles have mass. They independently published
papers on this topic in 1964.
Hide Caption
5 of 9









Story highlights
- Don Lincoln: There is no question that there is a mystery in the cosmos
- Galaxies don't act as we expect, Lincoln says
Dr. Don Lincoln is a senior physicist at Fermilab and does research using the Large Hadron Collider. He has written numerous books and produces a series of science education videos. He is the author of "The Large Hadron Collider: The Extraordinary Story of the Higgs Boson and Other Things That Will Blow Your Mind." Follow him on Facebook. The opinions expressed in this commentary are solely those of the author.
(CNN)Nearly
a mile under the Black Hills of South Dakota sits a canister of the
atomic element xenon, chilled cold enough to turn it to liquid. The
canister is the Large Underground Xenon, or LUX, detector -- the most
sensitive dark matter detector in the world. But the results of a new
analysis by the LUX Collaboration has left scientists perplexed about a
substance that has guided the formation of the stars and galaxies since
the cosmos began: dark matter.
Since
the 1930s, scientists have known that there was something unexplained
about the heavens. Swiss astronomer Fritz Zwicky studied the Coma
Cluster, a group of about a thousand galaxies, held together by their
mutual gravitational interactions. There was only one problem: The
galaxies were moving so fast that gravity shouldn't have been able to
hold them together. The cluster should have been ripped apart. In the
1970s, astronomers Vera Rubin and her collaborator Kenneth Ford studied
the rotation rates of individual galaxies and came to the same
conclusion. There appeared to be no way the observed matter contained in
galaxies would generate enough gravity to keep the stars locked in
their stately orbits.
These
observations, combined with many other independent lines of evidence,
led scientists to consider several possible explanations. These
explanations included the possibility that Newton's familiar laws of
motion might be wrong, or that our understanding of gravity needed to be
modified. Both these proposals, though, have been largely ruled out.
Another
idea was that there was somehow invisible matter that was generating
more gravity. Initial ideas centered on the possibility of black holes,
brown dwarf stars or rogue planets roaming the cosmos, but those
explanations have also been dismissed. Using a ruthless process of
elimination worthy of Sherlock Holmes, astronomers have come to believe
the explanation for all of the gravitational anomalies is that there
must be some sort of new and undiscovered type of matter in the
universe, which Zwicky in 1933 named "dunkle materie," or dark matter.
For
decades, scientists have tried to work out the properties of dark
matter and, while we don't know everything, we know a lot. From
astronomical observations, we know there is five times more dark matter
in the universe than all the "billions and billions" of stars and
galaxies mentioned in Carl Sagan's oft-quoted phrase. We also know that
dark matter cannot have electrical charge, otherwise it would interact
with light and we would have seen it. In fact, by a process of
elimination, we know that dark matter is not any known form of matter.
It is something new. Of this, scientists are sure.
However, scientists are less sure about the details.
For
decades now, the most popular theoretical idea was that dark matter was
a WIMP, short for weakly interacting massive particle. A WIMP would
have a mass in the range of 10 to perhaps 100 times heavier than the
familiar proton. It was a particle like a heavy neutron (but definitely
not a neutron), massive, electrically neutral, and stable on time
scales long compared to the lifetime of the universe.
The WIMP was popular for two main reasons.
First,
when cosmologists modeled the Big Bang and included WIMPs in the
calculation, the WIMPs actively participated in the earliest phases of
the birth of the universe but, as the universe expanded and cooled, the
space between them grew large enough that they stopped interacting with
one another. When scientists calculated how much mass should be tied up
in the relic WIMPs, they found it was five times as much mass as
ordinary matter, exactly the amount of dark matter seen by astronomers.
The
second reason for the popularity of the WIMP idea is that it explained a
mystery in particle physics. The recently discovered Higgs boson has a
mass of about 130 times that of the proton. Theoretical considerations
predicted a much larger mass, but if a WIMP exists, it is easy to
reconcile the prediction and measurement. These two reasons account for
the popularity of the WIMP idea and are called "the WIMP miracle."
The
LUX measurement is simply the most recent and most powerful of a long
line of searches for dark matter. They found no evidence for the
existence of dark matter and were able to rule out a significant range
of possible WIMP properties and masses.
Now
this doesn't mean the WIMP idea is dead or that dark matter has been
disproven. There remain WIMP masses that haven't been ruled out, and
there exist other possible dark matter candidates, including objects
called sterile neutrinos, which are possible cousins of the well-known
neutrinos generated in nuclear reactors and in the sun. Another
recurring proposed dark matter particle is the axion, suggested in the
1970s to explain mysteries in the asymmetry of subatomic processes.
(Although neither sterile neutrinos, nor axions, have been observed).
Nobody
knows what the final answer will be. That's why we do research. But
there is no question that there is a mystery in the cosmos. Galaxies
don't act as we expect. The LUX measurement is a powerful new bit of
information for astronomers to consider and has added to the general
confusion, forcing scientists to take another look at ideas other than
WIMPs.
All this reminds me of the old Buffalo Springfield song: "There's something happening here. What it is ain't exactly clear ..."



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