Con un nivel de certeza de 5 sigmas (aproximadamente 1 de cada 3 millones), los científicos del CERN acaban de anunciar el descubrimiento de una nueva partícula en consonancia con el bosón de Higgs. (En este enlace puedes checar los videos) La evidencia de la existencia de la partícula en el rango de masas 125GeV fue obtenida a partir del experimento CMS en el Gran Colisionador de Hadrones.
¿Es o no el bosón de Higgs? Según cuentan los investigadores, la
partícula que ha sido objeto de caza durante 45 años para explicar cómo
la materia alcanza su masa, podría haber alcanzado un punto en el que
denominar el experimento como “descubrimiento”, es decir, que el experimento CMS del Gran Colisionador de Hadrones alcanzó un nivel de seguridad nunca antes visto. Mientras, faltaría por saber los resultados del segundo experimento, Atlas.
Según el equipo:
Hemos visto un “bulto” en los datos correspondientes a una partícula con un peso de 125,3 GeV, alrededor de 133 veces más pesado que el protón en el corazón de cada átomo. Mediante la combinación de dos de nuestros conjuntos de datos, alcanzamos un nivel de certeza de 5 sigmas.
Es un resultado preliminar pero pensamos que es muy contundente y sólido. Podemos confirmar que ha sido descubierta una partícula que es consistente con la teoría del bosón de Higgs.
Aunque las indicaciones son las más cercanas posibles hasta ahora, queda por ver y confirmar si la partícula de la que se informa es el bosón de Higgs, una respuesta que los propios científicos han comunicado que no tendrá respuesta en el día de hoy.
Higgs boson-like particle discovery claimed at LHC
The moment when Cern director Rolf Heuer confirmed the Higgs results
Cern
scientists reporting from the Large Hadron Collider (LHC) have claimed
the discovery of a new particle consistent with the Higgs boson.
The particle has been the subject of a 45-year hunt to explain how matter attains its mass.
Both of the Higgs boson-hunting experiments at the LHC see a level of certainty in their data worthy of a "discovery".
More work will be needed to be certain that what they see is a Higgs, however.
Prof Stephen Hawking tells the BBC's Pallab Ghosh the discovery has cost him $100
The results announced at Cern (European Organization for Nuclear Research), home of the LHC in Geneva, were met with loud applause and cheering.
Prof Peter Higgs, after whom the particle is named, wiped a
tear from his eye as the teams finished their presentations in the Cern
auditorium.
"I would like to add my congratulations to everyone involved in this achievement," he added later.
"It's really an incredible thing that it's happened in my lifetime."
Prof Stephen Hawking joined in with an opinion on a topic often discussed in hushed tones.
"This is an important result and should earn Peter Higgs the Nobel Prize," he told BBC News.
"But it is a pity in a way because the great advances in physics have come from experiments that gave results we didn't expect."
'Dramatic'
The CMS team claimed they had seen a "bump" in their data
corresponding to a particle weighing in at 125.3 gigaelectronvolts (GeV)
- about 133 times heavier than the protons that lie at the heart of
every atom.
The BBC's George Alagiah explains the Higgs boson
They claimed that by combining two data sets, they had attained
a confidence level just at the "five-sigma" point - about a one-in-3.5
million chance that the signal they see would appear if there were no
Higgs particle.
However, a full combination of the CMS data brings that number just back to 4.9 sigma - a one-in-two million chance.
Prof Joe Incandela, spokesman for the CMS, was unequivocal:
"The results are preliminary but the five-sigma signal at around 125 GeV
we're seeing is dramatic. This is indeed a new particle," he told the
Geneva meeting.
Atlas results were even more promising, at a slightly higher
mass: "We observe in our data clear signs of a new particle, at the
level of five sigma, in the mass region around 126 GeV," said Dr Fabiola
Gianotti, spokeswoman for the Atlas experiment at the LHC.
Peter Higgs joined three of the six theoreticians who first predicted the Higgs at the conference
Prof Rolf Heuer, director-general of Cern, commented: "As a layman I would now say I think we have it."
"We have a discovery - we have observed a new particle consistent with a Higgs boson. But which one? That remains open.
"It is a historic milestone but it is only the beginning."
Commenting on the emotions of the scientists involved in the
discovery, Prof Incandela said: "It didn't really hit me emotionally
until today because we have to be so focussed… but I'm super-proud."
Dr Gianotti echoed Prof Incandela's thoughts, adding: "The
last few days have been extremely intense, full of work, lots of
emotions."
A confirmation that this is the Higgs boson would be one of
the biggest scientific discoveries of the century; the hunt for the
Higgs has been compared by some physicists to the Apollo programme that
reached the Moon in the 1960s.
Continue reading the main story
Statistics of a 'discovery'
- Particle physics has an accepted definition for a discovery: a "five-sigma" (or five standard-deviation) level of certainty
- The number of sigmas measures how unlikely it is to get a certain experimental result as a matter of chance rather than due to a real effect
- Similarly, tossing a coin and getting a number of heads in a row may just be chance, rather than a sign of a "loaded" coin
- A "three-sigma" level represents about the same likelihood as tossing eight heads in a row
- Five sigma, on the other hand, would correspond to tossing more than 20 in a row
- Independent confirmation by other experiments turns five-sigma findings into accepted discoveries
Scientists would then have to
assess whether the particle they see behaves like the version of the
Higgs particle predicted by the Standard Model, the current best theory
to explain how the Universe works. However, it might also be something
more exotic.
All the matter we can see appears to comprise just 4% of the
Universe, the rest being made up by mysterious dark matter and dark
energy.
A more exotic version of the Higgs could be a bridge to understanding the 96% of the Universe that remains obscure.
Scientists will have to look at how the Higgs decays - or
transforms - into other, more stable particles after being produced in
collisions at the LHC.
Dr Pippa Wells, a member of the Atlas experiment, said that
several of the decay paths already showed deviations from what one would
expect of the Standard Model Higgs.
For example, a decay path where the Higgs transforms into two photon particles was "a bit on the high side", she explained.
These could get back into line as more statistics are added, but on the other hand, they may not.
"We're reaching into the fabric of the Universe at a level we've never done before," said Prof Incandela.
"We're on the frontier now, on the edge of a new exploration.
This could be the only part of the story that's left, or we could open a
whole new realm of discovery."
Continue reading the main story The Standard Model and the Higgs boson
• The Standard Model is the simplest set of
ingredients - elementary particles - needed to make up the world we see
in the heavens and in the laboratory
• Quarks combine together to make, for
example, the proton and neutron - which make up the nuclei of atoms
today - though more exotic combinations were around in the Universe's
early days
• Leptons come in charged and uncharged
versions; electrons - the most familiar charged lepton - together with
quarks make up all the matter we can see; the uncharged leptons are
neutrinos, which rarely interact with matter
• The "force carriers" are particles whose
movements are observed as familiar forces such as those behind
electricity and light (electromagnetism) and radioactive decay (the weak
nuclear force)
• The Higgs boson came about because
although the Standard Model holds together neatly, nothing requires the
particles to have mass; for a fuller theory, the Higgs - or something
else - must fill in that gap
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