http___www.index.hr_black_clanak_hrvatski-zanstvenici-o-cernovoj-objavi-trebat-ce-nam-jos-puno-godina-da-bismo-utvrdili-radi-li-se-o-higgsovom-bozonu_623999.aspx_1.xml
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It’s been dubbed “the God particle” and “the Goddamn particle”. Now the Higgs boson has won the 2013 Nobel Prize in Physics for two of the researchers who independently proposed its existence in 1964: 80-year-old Belgian physicist François Englert and British physicist Peter Higgs, aged 84. Higgs proposed it first and the particle was given his name. Englert’s colleague, Robert Brout, died in 2011 and the prize is not awarded posthumously. The prize was awarded in October after results from the Large Hadron Collider (LHC) at CERN, the European Organization for Nuclear Research in Switzerland, confirmed in March that a particle they had detected was, in all likelihood, the Higgs boson. While physicists worldwide celebrated, Higgs, who is almost as elusive as the particle, only discovered he’d won the prize when a woman congratulated him on the street in London. There is a reason this long-sought particle has been revered and cussed. It is the missing keystone of the Standard Model, a theory describing the fundamental building blocks and forces of the universe. To test how well the model reflects reality, physicists look for the particles that it predicts in the wreckage created by particle colliders. The model has catalogued a table of elementary particles such as quarks, electrons and neutrinos. It explains how they interact with each other through particles known as bosons. Bosons are the force carriers. Photons, for instance, are bosons that carry the electromagnetic field. The Standard Model has a superb track record. In the 1960s it predicted W and Z bosons that would transmit the so-called “weak” force (responsible for radioactive decay and fusion). In the 1980s, those bosons were found at CERN, now the home of the LHC. The Higgs boson was also predicted in the 1960s. This profound boson was to be responsible for imparting mass. Without it our universe would be a blur of massless particles whizzing around at light speed. But for decades the Higgs boson remained stubbornly elusive. There were fears a black hole would swallow Geneva The US$10 billion LHC, dubbed the “genesis machine” was built to find it. It accelerates protons to 99% light speed on a 27 km collision course beneath the Swiss-French border. The forces released by such collisions have not been seen since the big bang. After 15 years of construction, it fired up in September 2008 amidst fears that it could create a mini black hole that would swallow Geneva. A needless concern: the machine blew a fuse and took until March 2010 to get running again. After several false sightings, in December 2011 a particle that lay in the expected mass range for a Higgs boson was registered by two independent detectors and their fiercely competitive teams at the LHC. According to the Atlas team, the new particle had a mass of 126 billion electron volts; according to the CMS team, it was 124 billion. But the shower of gamma rays that signalled the disintegration of a Higgs boson, could also be a chance artefact. To be certain, the physicists had to produce more data to give it odds of greater than one in a million of occurring by chance. On 4 July 2012 in CERN, and simulcast at the 36th International Conference on High Energy Physics in Melbourne, the announcement was made that the discovery of the Higgs was nigh. “This is a milestone for the physics community, and for human understanding of the fundamental laws that govern the universe,” effused Geoff Taylor, the director of Australia’s ARC Centre of Excellence for Particle Physics at the Terascale. Confirmation came in March 2013. The press release from CERN was still cautious: “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.” Nevertheless the March finding confirms the existence of the Higgs field which, like cosmic molasses, interacts with particles to give them mass. Scientists will now examine the LHC data to determine whether the properties of the Higgs can explain the mystery of gravity and more exotic phenomena such as dark matter or why there is more matter than antimatter in the universe. As Caltech physicist Sean Carroll put it, “The Higgs discovery is the end of one era and the beginning of another.”
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Foto: AFP/CERN DANAS je potvrđeno iz CERN-a (Europski centar za nuklearna istraživanja) da je uočena nova subatomska čestica koja ima obilježja Higgsovog bozona ili popularno nazvane "Božje čestice". Znanstvenici koji rade na projektima CMS i ATLAS predstavili su rezultate istraživanja, kojima je potvrđeno da se nova čestica raspada na dva fotona što govori da se radi o bozonu, čija je masa 125-126 GeV i čini ga najmasovnijim bozonom. Nova čestica je konzistentna s očekivanjem za Higgsov bozon, ali znanstvenici ne mogu još sa sto postotnom sigurnošću potvrditi da se doista radi o dugo očekivanoj "Božjoj čestici". Važno je naglasiti da rezultati oba ova istraživanja imaju vrijednost 5 sigma, na ljestvici koju fizičari koriste da bi naznačili koliko je neko otkriće točno, odnosno kolika je vjerojatnost da je opažanje plod slučajne fluktuacije poznatih procesa, a ne znak nove čestice, a ta je vjerojatnost manja od jednog dijela u tri milijuna. Razgovarali smo s dr. Ivicom Puljkom i dr. Damirom Lelasom koji pripadaju skupini od dvadeset hrvatskih fizičara koji sudjeluju u potrazi za Higgsovim bozonom, a oni su nam objasnili koja je važnost današnje objave i što ovo otkriće uopće znači. Sljedeći korak u razumijevanju prirode "Mi imamo jednu teoriju o prirodi koji nazivamo 'Standardni model elementarnih čestica' i ona jako lijepo opisuje stanje u prirodi, ali u toj teoriji nedostaje jedna karika, to jest, nedostaje objašnjenje zašto čestice imaju masu. Štoviše, taj koncept mase nikako ne možemo ugraditi u taj model prirode. Dugi smo niz bili u dilemi i razmišljali o tome da napustimo tu teoriju, ali zahvaljujući grupi znanstvenika, među kojima je i Peter Higgs, krenuli smo u potragu za mehanizmom koji bi objasnio kako čestice dobivaju svoju masu i na neki način zaokružiti teoriju Standardnog Modela te učiniti sljedeći korak u fundamentalnom razumijevanju prirode", rekao nam je dr. Ivica Puljak. "Važnost današnje objave otkrića novog bozona na Velikom Sudaraču Hadrona (LHC) na CERN-u je vrlo značajna iz nekoliko razloga. Na neki način to je nagrada za ogroman posao koji je trajao više od 20 godina, a obuhvaćao je pripremu, gradnju i puštanje u pogon LHC-a i pripadajućih detektora. Izvanredno uspješan rad akceleratora i detektora u zadnje tri godine je omogućio danas objavljene rezultate, kao i izuzetno složena analiza podataka koja je izvršena u rekordno kratkom roku", rekao je dr. Damir Lelas. Novi akcelerator "Posao koji još predstoji, u idućih nekoliko godina, je potvrda je li ovaj bozon stvarno Higgs bozon predviđen Standardnim modelom elementarnih čestica, dakle današnjom teorijom. Ako to bude tako, to će biti velika potvrda da je sadašnja slika valjana. Postojanje Higgsovog bozona, čestice odgovorne za masu drugih čestica, u okviru Standardnog modela je predviđanje staro već nekoliko desetljeća. U slučaju da se danas objavljeno otkriće ne bude moglo objasniti Standardnim modelom čestica, potrebno će biti potražiti dodatna objašnjenja i odgovore. To je, na neki način, još interesantniji scenarij. Bilo kako bilo, ovo otkriće ima i imat će dalekosežne posljedice za razumijevanje fizike najsitnijih dijelova tvari, kao i na spoznaju o strukturi Svemira", rekao je za Index Damir Lelas s Fakulteta elektrotehnike, strojarstva i brodogradnje. "Sva svojstva koja smo izmjerili slažu se sa svojstvima koja bi imao i Higgsov bozon i zato kažemo da otkrivena čestica liči na Higgsov bozon. A da bismo utvrdili radi li se o Higgsovom bozonu, mi moramo izmjeriti jako puno njegovih svojstava, a za to će nam trebati puno godina. Možda ćemo trebati napraviti i novi akcelerator", dodao je dr. Puljak. "Važno je spomenuti da su u ovim eksperimentima sudjelovali ljudi iz Hrvatske. I naša su sveučilišta potpuno ravnopravna bilo kojem drugom sveučilištu u svijetu koje je sudjelovalo u eksperimentu. To je jedan dio znanosti u kojem smo mi, zahvaljujući podršci ministarstva i sveučilišta, došli do stupnja da iz Zagreba, iz Splita, iz Hrvatske, možemo raditi potpuno ravnopravno za znanost. To je jedna dobra poruka da se i kod nas mogu neke stvari raditi kvalitetno", za kraj je rekao dr. Puljak.