Particle physicist Fabiola Gianotti has become the first woman to head CERN, the organization based in Switzerland that is home to the Large Hadron Collider. She succeeds outgoing director-general Rolf Heuer, who oversaw the laboratory’s operations for the last seven years.
Previously, Gianotti headed the ATLAS collaboration, one of two teams responsible for the discovery of the elusive Higgs boson on July 4, 2012. She quickly became a favorite figure in the media coverage surrounding that achievement — partly because of her gender (only 20% of the ATLAS team were women), and for her elegantly understated style, but also for her good humor.
For instance: Her use of the much-derided Comic-Sans typeface on her Powerpoint slides during that historic announcement was the source of much Internet amusement. Gianotti took the ribbing in stride. She even made an April Fool’s Day decree to make Comic Sans the official document typeface for all of CERN. She was a runner-up for Time magazine’s Person of the Year in 2012.
Gianotti’s father is a retired geologist, while her mother had a passion for music and art. Their daughter, born in 1962, effortlessly straddles both cultural realms, excelling not just in physics, but also music, cooking, and even dance (she trained as a ballerina as a child). “Musical harmony is based on physical principles while in cooking, ingredients must be weighed out with precision,” she told the Guardian in 2014, when her selection as the next director-general of CERN was announced. “At the same time, you have to able to invent, because if one follows the same recipe all the time, you never create anything new.”
Geneva, 14 July 2015. Today, the LHCb experiment at CERN’s Large Hadron Collider has reported the discovery of a class of particles known as pentaquarks. The collaboration has submitted a paper reporting these findings to the journal Physical Review Letters.
“The pentaquark is not just any new particle,” said LHCb spokesperson Guy Wilkinson. “It represents a way to aggregate quarks, namely the fundamental constituents of ordinary protons and neutrons, in a pattern that has never been observed before in over fifty years of experimental searches. Studying its properties may allow us to understand better how ordinary matter, the protons and neutrons from which we’re all made, is constituted.”
Our understanding of the structure of matter was revolutionized in 1964 when American physicist, Murray Gell-Mann, proposed that a category of particles known as baryons, which includes protons and neutrons, are comprised of three fractionally charged objects called quarks, and that another category, mesons, are formed of quark-antiquark pairs. Gell-Mann was awarded the Nobel Prize in physics for this work in 1969. This quark model also allows the existence of other quark composite states, such as pentaquarks composed of four quarks and an antiquark. Until now, however, no conclusive evidence for pentaquarks had been seen.
LHCb researchers looked for pentaquark states by examining the decay of a baryon known as Λb (Lambda b) into three other particles,
a J/ψ- (J-psi),
a proton and
a charged kaon.
Studying the spectrum of masses of the J/ψ and the proton revealed that intermediate states were sometimes involved in their production. These have been named Pc(4450)+ and Pc(4380)+, the former being clearly visible as a peak in the data, with the latter being required to describe the data fully.
“Benefitting from the large data set provided by the LHC, and the excellent precision of our detector, we have examined all possibilities for these signals, and conclude that they can only be explained by pentaquark states”, says LHCb physicist Tomasz Skwarnicki of Syracuse University.
"More precisely the states must be formed of
two up quarks,
one down quark,
one charm quark and
one anti-charm quark.”
Earlier experiments that have searched for pentaquarks have proved inconclusive. Where the LHCb experiment differs is that it has been able to look for pentaquarks from many perspectives, with all pointing to the same conclusion. It’s as if the previous searches were looking for silhouettes in the dark, whereas LHCb conducted the search with the lights on, and from all angles. The next step in the analysis will be to study how the quarks are bound together within the pentaquarks.
“The quarks could be tightly bound,” said LHCb physicist Liming Zhang of Tsinghua University, “or they could be loosely bound in a sort of meson-baryon molecule, in which the meson and baryon feel a residual strong force similar to the one binding protons and neutrons to form nuclei.”
More studies will be needed to distinguish between these possibilities, and to see what else pentaquarks can teach us. The new data that LHCb will collect in LHC run 2 will allow progress to be made on these questions.
1. CERN, the European Organization for Nuclear Research, is the world's leading laboratory for particle physics. It has its headquarters in Geneva. At present, its member states are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a Candidate for Accession. Serbia is an Associate Member in the pre-stage to Membership. Turkey is an Associate Member. India, Japan, the Russian Federation, the United States of America, the European Union, JINR and UNESCO have observer status.
In this Sept. 10, 2008 file photo, European Center for Nuclear Research (CERN) scientists control computer screens showing traces on Atlas experiment of the first protons injected in the Large Hadron Collider (LHC) during its switch on operation in CERN's control room, near Geneva, Switzerland.
The recent identification of a long-theorized particle provides strong evidence of a new form of matter.
Scientists working on the Large Hadron Collider, the most powerful particle collider in the world, verified the existence of a particle called Z(4430) last week, according to New Scientist. Previously, physicists had reasoned that the particle could exist but had yet to observe it.
Discovery of any new particle is an important step for scientists, but Z(4430) is viewed with particular importance — it is evidence of a new type of matter called a tetraquark.
Quarks are among the most basic building blocks of matter. Combinations of different types of quarks produce protons and neutrons. Although quarks typically bind together in groups of two or three, scientists had theorized that four quarks could be combined to form a different type of matter: the tetraquark.
"With the existence of tetraquarks, it is possible for neutrons within the core to interact strongly enough to create tetraquarks. This could even lead to the production of pentaquarks and hexaquarks, or even that quarks could interact individually without being bound into color neutral particles. This would produce a hypothetical object known as a quark star."
Tomorrow, 8 March, is International Women's Day, an occasion that has been observed since the early 1900s to inspire change for the equal rights and treatment of women in society.
A statement on the International Women's Day website puts it thus:
Women's equality has made positive gains but the world is still unequal. International Women's Day celebrates the social, political and economic achievements of women while focusing world attention on areas requiring further action.
One aim of the day is to draw attention to the struggle for equal rights and representation for women in the workforce. A part of this year's theme – Inspiring change – is to "inspire change for more women in science, engineering and technology". So to mark International Women's Day, we asked voices from the CERN community to express their opinions on gender, diversity and collaboration at CERN.
In addition, the Diversity Programme have organized a networking event to celebrate this year’s International Women’s Day, including round-table discussions on "Women in Science, Technology and Engineering”.
For more about diversity at CERN, check out the Diversity programme website, or take a look at the video below from CERN's Human Resources Department.
CERN voices speak about diversity at the laboratory (Video: CERN Human Resources Deparment)
GOOGLE NOW OFFERS YOU A PEEP INTO THE MACHINE THAT'S PROBING THE SECRETS OF THE BIG BANG AND HOW THE UNIVERSE WORKS. IT'S COLORFUL!
You may think Google's engineers are smart, but they're rather outclassed by the small town's worth of physicists, engineers, and mathematicians who populate CERN, Europe's amazing research facility that's home to the Large Hadron Collider. Now CERN has graciously opened its doors to Google's Street View. This means that you, too can take a walk around the rooms and structures where scientists are trying to unravel the secrets of everything.
CERN is enormous, so it took the Street View team about two weeks to image the whole thing back in 2011. The image archives are extensive as a result, letting you walk around the curving tunnels that contain the particle accelerator at the heart of the LHC and even to peep at the various experiments inserted in its beam, including the ones used to find the Higgs boson.
CERN - Large Hadron Collider tunnel. Photo: Google
It's the sort of facility that you will find fascinating--your writer has long dreamed of visiting, having been lucky enough to spend hundreds of hours strolling around a mere 100-meter synchrotron, a small toy compared to the LHC. Once you've enjoyed peeping at CERN, why don't you do a little reading about what goes on there?
Maria Ferrante's extraordinary voice was discovered when she sang in a voice class at University. She began studying with some of the greatest singers Franco and continued her studies as far as Beijing to discover aspects of bel canto master, Jiang Jou.
Here Maria sings "Caffeine" from an "Ig Nobel" prize ceremonie opera, with accompanist Alice Martelli, at TEDxCERN.
Candidate events in the CMS SM Higgs Search. CMS, 13 May 2012, 21.08. A typical candidate event including two high-energy photons.
HIG-13-002 Event 1: Event recorded with the CMS detector in 2012 at a proton-proton centre-of-mass energy of 8TeV. The event shows characteristics expected from the decay of the SM Higgs boson to a pair of Z bosons, one of which subsequently decays to a pair of electrons (green lines and green towers) and the other Z decays to a pair of muons (red lines). The event could also be due to known Standard Model background processes. Image 1 of 16. HIG-13-002 Event 1: Event recorded with the CMS detector in 2012 at a proton-proton centre-of-mass energy of 8 TeV. The event shows characteristics expected from the decay of the SM Higgs boson to a pair of Z bosons, one of which subsequently decays to a pair of electrons (green lines and green towers) and the other Z decays to a pair of muons (red lines). The event could also be due to known Standard Model background processes. Image: CERN, CMS
Geneva, 14 March 2013. At the Moriond Conference today, the ATLAS and CMS collaborations at CERN1’s Large Hadron Collider (LHC) presented preliminary new results that further elucidate the particle discovered last year. Having analysed two and a half times more data than was available for the discovery announcement in July, they find that the new particle is looking more and more like a Higgs boson, the particle linked to the mechanism that gives mass to elementary particles. It remains an open question, however, whether this is the Higgs boson of the Standard Model of particle physics, or possibly the lightest of several bosons predicted in some theories that go beyond the Standard Model. Finding the answer to this question will take time.
Whether or not it is a Higgs boson is demonstrated by how it interacts with other particles, and its quantum properties. For example, a Higgs boson is postulated to have no spin, and in the Standard Model its parity – a measure of how its mirror image behaves – should be positive. CMS and ATLAS 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.
“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 CMS spokesperson Joe Incandela.
"The beautiful new results represent a huge effort by many dedicated people. They point to the new particle having the spin-parity of a Higgs boson as in the Standard Model. We are now well started on the measurement programme in the Higgs sector," said ATLAS spokesperson Dave Charlton.
Image 4 of 16. HIG-13-004 Event 1: Event recorded with the CMS detector in 2012 at a proton-proton centre-of-mass energy of 8 TeV. The event shows characteristics expected from the decay of the SM Higgs boson to a pair of τ leptons. Such an event is characterised by the production of two forward-going jets, seen here in opposite endcaps. One of the τs decays to a muon (red lines on the right) and neutrinos, while the other τ decays into a charged hadron and a neutrino
To determine if this is the Standard Model Higgs boson, the collaborations have, for example, to measure precisely the rate at which the boson decays into other particles and compare the results to the predictions. The detection of the boson is a very rare event - it takes around 1 trillion (1012) proton-proton collisions for each observed event. To characterize all of the decay modes will require much more data from the LHC.
Footnote(s):
1. CERN, the European Organization for Nuclear Research, is the world's leading laboratory for particle physics. It has its headquarters in Geneva. At present, its member states are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a candidate for accession. Cyprus, Israel and Serbia are associate members in the pre-stage to membership. India, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and UNESCO have observer status.
El científico británico fue recompensado en la primera categoría por su trayectoria; los otros ocho científicos, por su contribución para encontrar el Bosón de Higgs.
Foto: Maximilien Brice/Cern/Archivo
EL HALLAZGO DE LOS HOYOS NEGROS, UNO DE LOS MOTIVOS PARA PREMIARLO.
Londres • El recién creado Premio Especial de Física Fundamental, que es el galardón científico con mayor dotación económica del mundo, ha sido otorgado al científico británico Stephen Hawking y a un equipo de ocho investigadores del gran acelerador de partículas del Centro Europeo de Investigación Nuclear (CERN), que participaron en el descubrimiento del Bosón de Higgs.
La primera edición de dicho reconocimiento, que es financiado por una organización que instituyó el multimillonario ruso Yuri Milner, otorgará, tanto a Hawking como al equipo de ocho científicos del CERN, tres millones de dólares (aproximadamente 38.5 millones de pesos), lo que representa más del doble de la aportacón económica que brindan los Nobel.
Para su nieto
En un correo electrónico remitido al periódico británico The Guardian, el físico británico, autor del libro Una breve historia del tiempo, anunció que se gastará el dinero del premio en ayudar a su nieto autista y en una casa para vacacionar.
Hawking, catedrático de la Universidad de Cambridge de 70 años, que desde los 21 sufre una enfermedad neurodegenerativa (esclerosis lateral amiotrófica), fue galardonado por los logros de toda su trayectoria como investigador, incluido su descubrimiento de los agujeros negros, informó la fundación de Milner en un comunicado difundido ayer.
“Nadie investiga en física con la intención de obtener un galardón, sino por la alegría de descubrir algo que nadie sabía hasta el momento. Pese a ello, premios como éste desempeñan un papel importante a la hora de obtener el reconocimiento del público.
Aumentan el prestigio de la física y el interés por ella”, afirmó el científico.
Hawking, que es catedrático de la Universidad de Cambridge (sur de Inglaterra), “es un auténtico gigante de la física moderna”, dijo Nima Arkani-Hamed, especialista estadunidense en esa materia que formó parte del jurado encargado de elegir a los ganadores.
Partícula evasiva
Además, la Fundación del Premio de Física Fundamental reconoció la labor de ocho científicos del CERN por su contribución a la detección del bosón de Higgs —la evasíva partícula que teóricamente permitió la formación del Universo y de todo lo que existe—, en julio de este año.
Este grupo está encabezado por Lyn Evans, actual director del acelerador de partículas, y por los directores actuales y pasados de los experimentos ATLAS y CMS, entre los que figuran Peter Jenni, Fabiola Gianotti, Michel Della Negra, Tejinder Singh Virdee, Guido Tonelli y Joe Incandela.
“Recibí una llamada de teléfono anunciándome que había ganado un premio millonario. Me quedé patidifuso. Lo primero que hice fue sentarme. Esto es genial para nosotros, ya que suple algunas deficiencias del premio Nobel, que no puede recaer en más de tres personas”, dijo Evans a The Guardian.
Yuri Milner, doctor en física teórica y promotor de este premio, espera atraer la atención masiva del público sobre la labor de los físicos.
“Espero que estos premios aporten más reconocimiento a algunas de las mentes más brillantes del mundo y a los grandes logros que han conseguido”, afirmó Milner, que construyó una fortuna valorada en mil millones de dólares invirtiendo en compañías de internet como Twitter, Facebook y Groupon.
La fundación también anunció a tres ganadores del premio Fronteras de la Física, que otorga a cada uno 300 mil dólares, y a los que recibieron el galardón Nuevas Fronteras de la Física, que recibirán 100 mil dólares.
El jurado estuvo compuesto por físicos internacionales entre los que se encontraban los estadunidenses Ed Witten, especialista en la teoría de las cuerdas, y Alan Guth, autor de la primera teoría sobre la expansión del universo.
A proton collides with a lead nucleus, sending a shower of particles through the CMS detector.
CREDIT: CERN
Collisions between particles inside the Large Hadron Collider atom smasher have created what looks like a new form of matter.
The new kind of matter is called color-glass condensate, and is a liquidlike wave of gluons, which are elementary particles related to the strong force that sticks quarks together inside protons and neutrons (hence they are like "glue").
Scientists didn't expect this kind of matter would result from the type of particle collisions going on at the Large Hadron Collider at the time. However, it may explain some odd behavior seen inside the machine, which is a giant loop where particles race around underneath Switzerland and France.
When scientists sped up protons (one of the building blocks of atoms) and lead ions (lead atoms, which contain 82 protons each, stripped of their electrons), and crashed them into each other, the resulting explosions liquefied those particles and gave rise to new particles in their wake. Most of these new particles, as expected, fly off in all directions at close to the speed of light. [Photos: The World's Largest Atom Smasher (LHC)]
But recently scientists noticed that some pairs of particles were flying off from the collision point in correlated directions.
"Somehow they fly at the same direction even though it's not clear how they can communicate their direction with one another. That has surprised many people, including us," MIT physicist Gunther Roland, whose group led the analysis of the collision data along with Wei Li of Rice University, said in a statement.
A similar flight pattern is seen when two heavy particles, such as lead and lead, crash into each other. In this case, the collisions create what's called quark-gluon plasma — a superhot soup of particles similar to the state of the universe just after the Big Bang. This soup can sweep particles in the same direction, explaining why their flight directions would be correlated.
But quark-gluon plasma isn't possible with lead-proton collisions, like the ones in the new study. Now researchers think a different state of matter, the color-glass condensate, may act in a similar way. The color-glass condensate's dense swarm of gluons may also sweep particles off in the same direction, suggested Brookhaven National Laboratory physicist Raju Venugopalan, who first predicted the substance, which may also be seen after proton-proton collisions.
The mechanism may depend on a weird quirk of particles called quantum entanglement. Two particles can be entangled so that they retain a connection even after they are separated, and an action on one reverberates on the other.
Entangled gluons in the color-glass condensate could explain how particles flying away from the collision point might share information about their flight direction with each other, Venugopalan said.
The intriguing phenomenon was not expected to result from the LHC's run of proton-lead collisions, which was meant to serve as a reference point for comparison to other types of collisions.
"You don't expect quark-gluon plasma effects" with lead-proton collisions, Rolandsaid. "It was supposed to be sort of a reference run — a run in which you can study background effects and then subtract them from the effects that you see in lead-lead collisions.
The findings will be detailed in an upcoming issue of the journal Physical Review B.
For a report on ABC's Catalyst program (http://www.abc.net.au/catalyst/), I visited the Large Hadron Collider in Switzerland to find out what is being done now that the Higgs Boson has been discovered.
Although its mass has been measured around 125-126 GeV most of the other properties of the particle remain unknown. Its spin appears to be 0 or 2 but more results are required to nail this down. If it is the standard model Higgs, the spin should be 0, resulting in a fairly symmetric distribution of decay products in the detectors.
We may know this year if it's not the standard model Higgs - this would be the case if it doesn't decay into specific particles with the expected frequency. However if it is the standard model Higgs, it may take many more years to be certain. The large hadron collider will be shut down in 2013 for upgrades so that higher energies up to 14 TeV can be tested. Right now the LHC is operating at 8 TeV. The next announcement is expected in December.
Representatives from the science-funding agencies and library communities of 29 countries are meeting at CERN today to launch the Sponsoring Consortium for Open Access Publishing in Particle Physics (SCOAP3) initiative.
At a meeting last week the CERN Finance Committee officially approved the award of contracts for the provision of peer-review, open access and other publication services for the benefit of SCOAP3. The consortium aims to provide unrestricted access to high-energy-physics (HEP) research literature in its final, peer-reviewed form, by sharing the cost of the peer-review service between funding agencies, research institutions, libraries and library consortia, while publishers make electronic versions of their journals open access.
"The Finance Committee's approval is a watershed, with a large exclamation mark!" says CERN librarian Jens Vigen. "After years of design and consensus building, we can now move on to the implementation phase of the project. This is the first time ever that an entire field is concretely moving towards open-access publishing."
The goal of open access is to grant anyone free access to the results of scientific research. But the current model of scientific publishing – where journal access is restricted to paying customers and reuse of material is hindered by copyright restrictions – is at odds with this idea. Traditionally libraries have paid, on behalf of their readers, for access to content. However, the service needed by the community is the peer-review and quality-assurance service, as in the field of high-energy physics community preprints of articles are generally made available online long before they appear in journals. SCOAP3 is putting this service at the centre, remunerating the publishing industry for it, while content will be open access.
"The issue is that people in our field don't tend to read the journals, they read the arXiv," says Vigen. "This said, peer-reviewed journals add an indispensable quality stamp. The new system enshrines the role of the journals in providing the peer-review service rather than repositories of content."
In the SCOAP3 model, HEP funding agencies, research institutions, libraries and library consortia, which today buy journal subscriptions to implicitly support the peer-review service, instead pool their resources explicitly to cover the cost of this service, while publishers make the electronic versions of their journals open access. SCOAP3 partners recover their contributions by redirecting the funds they currently use for journal subscriptions.
With a projected SCOAP3 budget of 36 million Swiss francs over three years, 12 journals from 7 publishers are now on the list for a possible contract for the provision of peer-review, open access and other publication services. Over 6600 articles relevant to the field were published in these journals in 2011; this represents the vast majority of the literature.
"It has taken an amazing team effort to get here, with volunteers from the library community, research institutions and funding agencies working hard together to steer the initiative, alongside constructive discussions with the publishers of the field," says Salvatore Mele, head of Open Access at CERN, who convened the SCOAP3 Steering Committee over a year and a half. "This bodes well for the next crucial steps as SCOAP3 moves forward."
"I think neighbouring fields like nuclear physics and astrophysics might be inspired by this model in some way," says Vigen. "When we initiated the process six years ago, open access publishing was in its infancy – today it has become mainstream. We have entered into an era that will accelerate science."
The ATLAS and CMS experiments at CERN today presented their latest results in the search for the long-sought Higgs boson. Both experiments see strong indications for the presence of a new particle, which could be the Higgs boson, in the mass region around 126 gigaelectronvolts (GeV).
The experiments found hints of the new particle by analysing trillions of proton-proton collisions from the Large Hadron Collider (LHC) in 2011 and 2012. The Standard Model of particle physics predicts that a Higgs boson would decay into different particles – which the LHC experiments then detect.
Both ATLAS and CMS gave the level of significance of the result as 5 sigma on the scale that particle physicists use to describe the certainty of a discovery. One sigma means the results could be random fluctuations in the data, 3 sigma counts as an observation and a 5-sigma result is a discovery. The results presented today are preliminary, as the data from 2012 is still under analysis. The complete analysis is expected to be published around the end of July.
PR17.12
04.07.2012
CERN experiments observe particle consistent with long-sought Higgs boson
Geneva, 4 July 2012. At a seminar held at CERN1 today as a curtain raiser to the year’s major particle physics conference, ICHEP2012 in Melbourne, the ATLAS and CMS experiments presented their latest preliminary results in the search for the long sought Higgs particle. Both experiments observe a new particle in the mass region around 125-126 GeV.
“We observe in our data clear signs of a new particle, at the level of 5 sigma, in the mass region around 126 GeV. The outstanding performance of the LHC and ATLAS and the huge efforts of many people have brought us to this exciting stage,” said ATLAS experiment spokesperson Fabiola Gianotti, “but a little more time is needed to prepare these results for publication.”
"The results are preliminary but the 5 sigma signal at around 125 GeV we’re seeing is dramatic. This is indeed a new particle. We know it must be a boson and it’s the heaviest boson ever found,” said CMS experiment spokesperson Joe Incandela. “The implications are very significant and it is precisely for this reason that we must be extremely diligent in all of our studies and cross-checks."
“It’s hard not to get excited by these results,” said CERN Research Director Sergio Bertolucci. “ We stated last year that in 2012 we would either find a new Higgs-like particle or exclude the existence of the Standard Model Higgs. With all the necessary caution, it looks to me that we are at a branching point: the observation of this new particle indicates the path for the future towards a more detailed understanding of what we’re seeing in the data.”
The results presented today are labelled preliminary. They are based on data collected in 2011 and 2012, with the 2012 data still under analysis. Publication of the analyses shown today is expected around the end of July. A more complete picture of today’s observations will emerge later this year after the LHC provides the experiments with more data.
The next step will be to determine the precise nature of the particle and its significance for our understanding of the universe. Are its properties as expected for the long-sought Higgs boson, the final missing ingredient in the Standard Model of particle physics? Or is it something more exotic? The Standard Model describes the fundamental particles from which we, and every visible thing in the universe, are made, and the forces acting between them. All the matter that we can see, however, appears to be no more than about 4% of the total. A more exotic version of the Higgs particle could be a bridge to understanding the 96% of the universe that remains obscure.
“We have reached a milestone in our understanding of nature,” said CERN Director General Rolf Heuer. “The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will pin down the new particle’s properties, and is likely to shed light on other mysteries of our universe.”
Positive identification of the new particle’s characteristics will take considerable time and data. But whatever form the Higgs particle takes, our knowledge of the fundamental structure of matter is about to take a major step forward.
1. CERN, the European Organization for Nuclear Research, is the world's leading laboratory for particle physics. It has its headquarters in Geneva. At present, its Member States are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a candidate for accession. Israel and Serbia are Associate Members in the pre-stage to Membership. India, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and UNESCO have Observer status.
LHC data confirm discovery, but not identity, of Higgs-like entity.
The ATLAS detector (above) and its rival CMS have both seen a clear signal of a new, Higgs-like particle. CLAUDIA MARCELLONI/CERN
Physicists in Europe will present evidence of an entirely new particle on Wednesday,Nature has learned. But more data will be needed to officially confirm whether it is indeed the long-awaited Higgs boson — the particle thought to be behind the mass of all the others.
Even as rumours fly in the popular media, physicists have begun quietly cheering at CERN, the European particle-physics lab near Geneva in Switzerland. “Without a doubt, we have a discovery,” says one member of the team working on the ATLAS experiment, who wished to remain anonymous. “It is pure elation!”
For nearly half a century, physicists have predicted the existence of a particle that helps to endow others with mass. Named after theoretical physicist Peter Higgs, the boson is the upshot of a mathematical trick that unites the electromagnetic and weak nuclear forces into a single ‘electroweak’ interaction. It is considered the final, crucial piece of the standard model of particle physics.
Physicists working on ATLAS saw hints of a Higgs particle last year (see: 'Detectors home in on Higgs boson' ), but the first solid results from the full 2012 data set arrived last week. The signal was seen in the decay of a Higgs-like particle into two high-energy photons — one of the cleanest ways to glimpse a Higgs among the hundreds of trillions proton–proton collisions recorded in the Large Hadron Collider (LHC). The data contained “a significant excess" of collision events at a mass of around 125 gigaelectronvolts, the ATLAS researcher told Nature, which is the same value suggested by last year's data. The same signal is present in other Higgs decay channels, too, such as those in which the new Higgs-like particle decays into four leptons.
ATLAS's chief rival, the CMS experiment, also sees significant Higgs evidence in its 2012 data, according to a physicist there, who asked not to be named because both ATLAS and CMS have strict embargoes in place. “In practice you would have to be monstrously sceptical not to be convinced by what we have now,” the source says. "But the final decisions on what to say on Wednesday are still being made."
Weighing in
Physicists have maintained that they will not announce the discovery of the Higgs until the signal surpasses 5 sigma, meaning that it has just a 0.00006% chance of being wrong. The ATLAS and CMS experiments are each seeing signals between 4.5 and 5 sigma, just a whisker away from a solid discovery claim. The results are also consistent with an analysis from the mothballed Tevatron collider, which was presented today at Fermilab in Batavia, Illinois.
CERN's head of communications, James Gillies, confirmed that four of the theorists who dreamt up the Higgs mechanism in the 1960s — François Englert, Carl Hagen, Peter Higgs and Gerald Guralnik — will be present at Wednesday's seminar, but he declined to be drawn on what will be announced. "Things are still evolving here," he says. "Until the spokespersons of the ATLAS and CMS collaborations stand up in front of the audience, it's premature to speculate."
Physicists will now turn their attention to understanding the new particle. Crucially, they will want to know whether it behaves like a mass-giving Higgs, and more specifically whether it behaves like the Higgs predicted in the standard model. One important task will be to carefully measure the different ways that the particle is produced and decays inside the LHC detectors. The rates could be altered by the existence of exotic new particles not predicted by the standard model that would interfere with the underlying quantum mechanical behaviour.
“Fine, there is something there — a resonance," says Martinus Veltman, emeritus professor at the University of Michigan in Ann Arbor, who shared the 1999 Nobel Prize in Physics for his work on the standard model. “Now we have to find out if it has all the properties that the Higgs is supposed to have.”Nature doi:10.1038/nature.2012.10932
El Centro Europeo de Física de Partículas (CERN) ha reunido en sólo tres meses más del doble de datos experimentales que todo el pasado año, lo que le acerca a un resultado definitivo sobre la existencia o no del Bosón de Higgs, la última partícula a descubrir en el modelo estándar de física.
Así lo reveló el CERN al anunciar que la próxima semana celebrará un seminario científico para aportar "la última actualización en la búsqueda del Bosón de Higgs".
El director de Aceleradores y Tecnología del CERN, Steve Myers, indicó que terminó la toma de datos para presentar los resultados preliminares en la mayor conferencia internacional de física de partículas del año, la ICHEP, que se celebra julio en Melburne (Australia).
El calendario de funcionamiento del acelerador LHC se diseñó especialmente para obtener "la mayor cantidad posible de datos de los experimentos" antes de ese gran evento científico, de forma que entre abril y junio de 2012 se consiguieron más informaciones que en todo 2011.
En ese periodo se incrementó la energía a la que circulaban los haces de protones hasta llegar a una intensidad jamás alcanzada por otra máquina y se mejoraron las técnicas de análisis para seleccionar datos que podrían probar la existencia del Bosón.
La información reunida "debería ser suficiente para ver si las tendencias que observamos en 2011 todavía están allí o si por el contrario han desaparecido", sostuvo el director de investigación e informática del CERN, Sergio Bertolucci.
A finales del pasado año, científicos del CERN aseguraron que el análisis de los primeros resultados arrojaba indicios "intrigantes" de la eventual existencia del Bosón de Higgs, pero explicaron que con el nivel de datos reunidos hasta entonces no era posible dar una confirmación científica de la partícula más buscada de la física moderna.
In this Sept. 10, 2008 file photo, European Center for Nuclear Research (CERN) scientists control computer screens showing traces on Atlas experiment of the first protons injected in the Large Hadron Collider (LHC) during its switch on operation in CERN's control room, near Geneva, Switzerland.
