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What is the Higgs boson and why is it important to science? - By Alan Henry on August 1, 2011 at 9:40 am - Comment Share This article If you’ve paid any attention to physics or physical science research in the past few years, you’ve heard about the Large Hadron Collider (LHC), the world’s largest and highest-energy particle accelerator. The LHC was built partially with the hopes of finding the elusive Higgs boson, a theorized but undiscovered particle which, if found, would sew up nicely our understanding of the relationship between mass and energy. The Higgs boson is the only particle left in our understanding of particle physics (called the Standard Model) that we haven’t discovered. We think it exists — there’s math that postulates it does — it simply has never been observed. This is why it’s called the “God Particle,” because it’s the particle that would explain the difference between objects with mass and objects that have only energy — objects with form and objects without. If we do find it, we’ll know that we have the right idea about how particles acquire mass — as in, how photons, riding on beams of light, have no mass at all, while the W and Z bosons (two particles that govern the “weak force,” one of the fundamental forces that keep atoms together) have the masses that they do, and why other subatomic particles have the weights that they have. Faced with the mystery, English physicist Peter Higgs set out to understand how exactly energy in the universe became mass — how particles, with their wave-like characteristics, acquired mass and interacted with other particles around them. He theorized of a field, one that made up the lattice of the entire universe, that’s responsible for the mass of objects, specifically particles. The Higgs boson would be a density of that field, or an observable indication that it exists. So why are physicists around the world eagerly searching for the Higgs? The field itself, aside from being the explanation for why everything in the universe has mass, is also one of the final pieces of the puzzle we call the Standard Model of physics. It neatly ties together elements of quantum mechanics and electromagnetism, and would be an integral part of the material world that we all live in. Plus, it may even interact with other particles we have yet to discover, like the ones that may make up dark matter. The trouble is we won’t know if the field exists unless we find the Higgs boson, or some indication that there’s a mechanism that allows particles to acquire mass. This is precisely what the latest generation of particle accelerators like the LHC and the Tevatron are trying to solve. The diagram here shows the current status of the search for the Higgs boson, as of March 2011. The green areas are spaces we’re sure it doesn’t exist, and can either observe or easily test for it. The orange areas are spaces where Tevatron has tested and found nothing with either a 95% or a 90% confidence level. The white spaces are areas we haven’t looked. The spaces below 157 gigaelectronvolts (GeV) (and to a lesser extent between 180 GeV and 185 GeV) are the prime targets for the LHC, which has the sensitivity to observe that range. By slamming particles together at even higher velocities and watching what happens to the subatomic particles and their energy levels after they’ve been smashed together, physicists can examine the mass and energy of the particles before they collided, and then the mass and energy of everything they saw after the collision, including all of the bits, waves, and subatomic particles afterward, and see what’s left over or how those bits interacted with one another. Currently, the LHC is the one collider in the world with the power to smash subatomic particles together at the energy needed to look for the Higgs, no offense to the Tevatron and the folks at Fermilab. Even today, the search is on. Every so often there are reports that someone’s found something at LHC or Tevatron, or that a discovery has been made, all of which are quickly tamped down by the researchers there, mostly because it doesn’t count until it’s been reviewed, analyzed, and documented properly. In modern physics, there are very few “eureka!” moments, and a lot of plodding through data and calculations for years. In fact, even as the search for the Higgs continues, there are other physicists working on theories that would explain the same phenomenon without the need for the Higgs boson or the Higgs field at all — if it doesn’t exist, science will just march on to the next set of likely theories. To that end, it may be years before physicists can confidently say there is a Higgs boson, a Higgs Field, or that we understand the mechanism by which the particles that make up everything around us in the universe actually have mass, as opposed to just being formless energy.
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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.