Ja­panese, Cana­dian win No­bel for neu­tri­nos

The China Post - - FRONT PAGE - BY PIA OH­LIN

Takaaki Ka­jita, of Ja­pan, and Arthur McDon­ald, of Canada, were awarded the No­bel Physics Prize on Tues­day for de­ter­min­ing that neu­tri­nos have mass, a key piece of the puz­zle in un­der­stand­ing the cos­mos.

“The dis­cov­ery has changed our un­der­stand­ing of the in­ner­most work­ings of mat­ter and can prove cru­cial to our view of the Uni­verse,” the Royal Swedish Academy of Sciences said.

The find­ings are so far-reach­ing that they chal­lenge the so-called Stan­dard Model, the con­cep­tual model of fun­da­men­tal par­ti­cles and forces, it said.

Neu­tri­nos are light­weight neu­tral par­ti­cles that are cre­ated as the re­sult of nu­clear re­ac­tions, such as the process that makes the sun shine.

Next to par­ti­cles of light called pho­tons, they are the most abun­dant par­ti­cles in the Uni­verse.

Their ex­is­tence was ten­ta­tively pro­posed in 1930, but was only proved in the 1950s, when nu­clear re­ac­tors be­gan to pro­duce streams of the par­ti­cles.

The pre­vail­ing the­ory was that neu­tri­nos were mass­less, but ex­per­i­ments car­ried out sep­a­rately in un­der­ground labs by teams led by Ka­jita in Ja­pan and McDon­ald in Canada showed that this was not the case.

Neu­tri­nos Change Iden­tity

Many neu­tri­nos blasted out from the sun — a type called elec­tron neu­tri­nos — “os­cil­lated” en route to be­come cousin par­ti­cles called muon-neu­tri­nos and tau-neu­tri­nos, they found.

Since the 1960s, sci­en­tists had es­ti­mated the num­ber of neu­tri­nos cre­ated in the nu­clear re­ac­tions that make the sun shine.

But when this fig­ure was com­pared against ac­tual mea­sure­ments on Earth, an ano­maly emerged.

Up to two-thirds of the cal­cu­lated tally of neu­tri­nos com­ing from the sun was miss­ing, and no one knew where they were go­ing.

In 1998, work­ing at the Su­perKamiokande de­tec­tor — a 50,000-tonne tank of highly pu­ri­fied wa­ter built at the bot­tom of an old zinc mine in cen­tral Ja­pan — Ka­jita dis­cov­ered that neu­tri­nos seemed to change iden­ti­ties on their way from the sun to Earth.

Mean­while, in 1999, sci­en­tists led by McDon­ald at the Sud­bury Neu­trino Ob­ser­va­tory, built deep un­der the ground in an old nickel mine in On­tario, Canada, were also study­ing neu­tri­nos com­ing from the sun. In 2001, his group also proved that neu­tri­nos had a chameleon­like na­ture.

Un­der the quirky rules of quan­tum physics, the iden­tity shift the sci­en­tists ob­served can only hap­pen if neu­tri­nos have mass.

“You can chalk up yet another suc­cess for quan­tum me­chan­ics be­cause with­out it we would not be able to make sense of the ex­per­i­men­tal re­sults that have led to this prize,” said Robert Brown, head of the Amer­i­can In­sti­tute of Physics.

The No­bel com­mit­tee said the work threw down the gaunt­let to the­o­ret­i­cal physics.

Stan­dard Model Ques­tioned

“The ex­per­i­ments have ... re­vealed the first ap­par­ent crack in the Stan­dard Model,” the panel said.

“It has be­come ob­vi­ous that the Stan­dard Model can­not be the com­plete the­ory of how the fun­da­men­tal con­stituents of the Uni­verse func­tion.”

In­tense ac­tiv­ity is un­der­way to un­der­stand more about the elu­sive par­ti­cles.

“New dis­cov­er­ies about their deep­est se­crets are ex­pected to change our cur­rent un­der­stand­ing of the history, struc­ture and fu­ture fate of the Uni­verse,” the jury said.

Ka­jita and McDon­ald will share the prize sum of 8 mil­lion Swedish kro­nor (US$950,000).

McDon­ald, 72, told the No­bel Foun­da­tion that win­ning the prize was “a very daunt­ing ex­pe­ri­ence, need­less to say,” re­call­ing the “eureka mo­ment” when he made his dis­cov­ery.

“For­tu­nately I have many col­leagues as well who share this prize with me,” he added.

McDon­ald is a pro­fes­sor emer­i­tus at Queen’s Univer­sity in Canada.

Ka­jita, 56, mean­while said “it was a real sur­prise to me. It’s kind of un­be­liev­able.”

Asked whether he ever dreamed of win­ning the No­bel, he replied: “As re­ally a dream maybe yes, but not a se­ri­ous dream so far.”

He is the di­rec­tor of the In­sti­tute for Cos­mic Ray Re­search and a pro­fes­sor at the Univer­sity of Tokyo.

This year's physics prize fol­lows the 2002 award to Ray­mond Davis, of the U.S., and Masatoshi Koshiba, of Ja­pan, pioneers in the field of cos­mic neu­tri­nos.

No­bel week con­tin­ues on Wed­nes­day with the an­nounce­ment of the win­ners of the No­bel Chem­istry Prize.

AFP

(Top) Takaaki Ka­jita, of Ja­pan, di­rec­tor of the In­sti­tute for Cos­mic Ray Re­search and pro­fes­sor at the Univer­sity of Tokyo, speaks with Ja­panese Prime Min­is­ter Shinzo Abe on the phone, af­ter learn­ing he won the No­bel Prize in physics at the univer­sity in Tokyo, Tues­day, Oct. 6. (Above) This hand­out photo pro­vided Tues­day, by SNOLAB and Kelsey McFar­lane in Sud­bury, On­tario, shows Arthur McDon­ald.

AP

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