Apa itu Neutrino ?

dauswq

Apa itu Neutrino ?                    by editor on Sep 24, 2011 • 8:58 am 3 Comments
               

Oleh : Nor Sofiah Ahmad
        (Pelajar Sarjana Fizik yang menjalankan kajian tentang neutrino di Universiti Malaya)
        

        Apa itu neutrino? Jika ditanyakan soalan ini kepada sesiapa yang bukan dari latar belakang sains yang mempelajari ilmu Fizik secara mendalam saya pasti hanya segelintir sahaja yang mampu menjelaskannya. Di sini saya akan menceritakan secara ringkas apa itu neutrino.

Neutrino adalah zarah kecil yang berinteraksi secara lemah dengan zarah-zarah lain. Neutrino mempunyai spin-1/2 dan mempunyai tiga perisa atau dikenali sebagai 'flavor' iaitu elektron neutrino, muon neutrino dan tau neutrino. Neutrino mula dijumpai secara teorinya oleh saintis fizik iaitu Wolfgang Pauli (1900 – 1958). Pada masa itu neutrino dianggap sebagai zarah neutral yang tidak mempunyai jisim sama seperti foton. Tetapi dengan kemajuan teknologi dan perkembangan bidang fizik eksperimen, Pusat Penyelidikan Neutrino yang dikenali sebagai Super Kamiokande atau Super-K singkatan daripada Super-Kamioka Nucleon Decay Experiments di Jepun telah berjaya mengesan kehadiran jisim neutrino.

        

Apa yang menariknya mengenai zarah kecil yang sangat lemah berinteraksi dengan zarah-zarah lain ini?

Neutrino dipercayai terhasil dalam kuantiti yang banyak semasa kejadian Dentuman Besar yang juga dikenali sebagai Big Bang. Umum mengetahui bahawa Gelombang Mikro Latarbelakang (CMB) yang terhasil akibat letupan besar merupakan bukti kukuh kepada Teori Dentuman Besar ini, tetapi hanya sebahagian kecil yang mengetahui bahawa wujudnya secara teori mengenai Neutrino Kosmik Latarbelakang (CnB).

Walaupun saya mengatakan bahawa CnB wujud secara teorinya, ramai saintis dan juga kosmologis percaya CnB ini wujud dan mampu dikesan sedikit masa lagi hasil dari perkembangan bidang terknologi pada hari ini. Jika kita mampu mengesan CnB seperti mana kemampuan mengesan CMB, maka saya percaya suatu hari nanti kita akan membuka sedikit ruang jawapan kepada misteri alam semesta. Misteri-misteri yang dimaksudkan termasuklah seperti mengapa hanya terdapat unsur-unsur ringan seperti H, He, dan Li sahaja yang wujud selepas berlakunya letupan besar, penyelesaian kepada kehilangan jisim alam semesta dan juga kehadiran jirim hitam.

Pengesan Neutrino Super Kamiokande di Jepun

Semasa saya melakukan penyelidikan mengenai neutrino ini dan kesannya kepada pembentukan unsur-unsur ringan seperti yang dinyatakan di atas (H, He dan Li), saya terbaca mengenai kewujudan jisim neutrino mampu menjelaskan mengenai misteri jirim hitam dan juga misteri kehilangan jisim alam ini. Saya akan menerangkan secara ringkas mengenai kepentingan neutrino pada pembentukan unsur-unsur ringan.

Seperti yang dinyatakan, neutrino mempunyai jisim, tetapi malangnya saintis masih tidak mampu mengesan jisim neutrino secara mutlak kerana kewujudan jisim neutrino ini adalah hasil gabungan dua perisa neutrino atau secara saintifik nya adalah superposisi dua keadaan eigen jisim electron neutrino dan muon neutrino.

Saya tidak akan menerangkan secara terperinci mengenai istilah fizik ini kepada pembaca awam yang mungkin sukar untuk difahami. Kehadiran jisim neutrino ini akan menyebabkan neutrino tadi berayun pada frekuansi tertentu dan ini seterusnya menyebabkan berlakunya resonans dan seterusnya menyebabkan wujud tenaga tambahan dan kehilangan tenaga kepada persekitaran ( tenaga dari alam semesta selpas bermulanya pengembangan alam sejurus letupan besar) dan juga kepada neutrino.

Pertambahan tenaga oleh neutrino hasil daripada ayunan neutrino tersebut menyebabkan berlakunya penghasilan proton secara besar-besaran dan seterusnya memyebabkan pembentukan unsur-unsur seperti H, D, He . Oleh kerana jumlah neutron yang semakin berkurangan akibat daripada pertukaran neutron kepada proton melalui proses reputan beta maka ini menyebabkan pembentukan unsur-unsur lain terhalang. Kita mengetahui bahawa, untuk membentuk unsur seperti Deuterium D, kita memerlukan neutron dan juga proton. Neutron akan bergabung dengan proton dan membentuk unsur-unsur yang lebih berat, tetapi jika jumlah neutron yang semakin berkurangan ini menyebabkan berlaku halangan pembentukan unsur-unsur lain tadi. Selain itu unsur-unsur berat yang lain tidak dapat wujud kerana berlakunya ketidakstabilan nuklear dan menyebabkan unsur-unsur berat yang terhasil hasil dari gabungan unsur-unsur ringan ini terpecah kembali kepada unsur-unsur asas seperti H dan juga He.

Jika kita mampu mengesan jisim neutrino secara mutlak saya percaya bahawa kita mampu menyelesaikan banyak lagi masalah di dalam Fizik. Saya akan cuba menerangkan dengan lebih lanjut mengenai kesan pengembangan alam semesta kepada kepada neutrino di masa akan datang. Semoga dengan kehadiran artikel ini dapat menarik minat ramai orang terhadap kajian Kosmologi.

SUMBER: http://www.majalahsains.com/2011/09/apa-itu-neutrino/

dauswq

Related thread: http://eforum4.cari.com.my/viewthread.php?tid=511102

"Teori Mekanik Kuantum"

dauswq

Mr.Timms

jadik neutrino bertebaran di segenap alam la yer?

Mr.Timms

sesuatu yg bergerak mesti ada tenaga kan?agak2 kalau teori ni dipahami possible ke kita boleh cipta UFO yg boleh bergerak bebas di alam semsta pada masa yan snigkat?

dauswq

Reply 4# Mr.Timms

yup, tp neutrino ni massless..in physical form kita tak leh nampak
but in theory, itulah cara penjelasan supaya tak bercanggah ngan konsep "partikel yg boleh bhave spt gelombang"...

dauswq

Reply 5# Mr.Timms

yup perlu ada tenaga..tiada tenaga even gelombang sekalipun kita takkan dpt transfer dr satu medium ke medium lain...

cepheid

Teringat pasal filem 2012. Pemahaman paling hampeh terhadap neutrino

fairluck

Reply  Mr.Timms

yup, tp neutrino ni massless..in physical form kita tak leh nampak
but in theor ...
dauswq Post at 13-2-2012 15:13

    hi kenyataan yg neutrino ni massless... means dia bukan matter..ia antimatter... is it true?

cepheid

Berita ni hangat tak lama dulu. Maybe orang kat forum ni kurang ambik tahu:

http://www.guardian.co.uk/scienc ... l-faster-than-light

Neutrinos still faster than light in latest version of experiment
The scientists who appeared to have found in September that certain subatomic particles can travel faster than light have ruled out one potential source of error in their measurements after completing a second, fine-tuned version of their experiment.

Their results, posted on the ArXiv preprint server on Friday morning and submitted for peer review in the Journal of High Energy Physics, confirmed earlier measurements that neutrinos, sent through the ground from Cern near Geneva to the Gran Sasso lab in Italy 450 miles (720km) away seemed to travel faster than light.

The finding that neutrinos might break one of the most fundamental laws of physics sent scientists into a frenzy when it was first reported in September. Not only because it appeared to go against Albert Einstein's theory of special relativity but, if correct, the finding opened up the troubling possibility of being able to send information back in time, blurring the line between past and present and wreaking havoc with the fundamental principle of cause and effect.

The physicist and TV presenter Professor Jim Al-Khalili of the University of Surrey expressed the incredulity of many in the field when he said that if the findings "prove to be correct and neutrinos have broken the speed of light, I will eat my boxer shorts on live TV".

In their original experiment scientists fired beams of neutrinos from Cern to the Gran Sasso lab and the neutrinos seemed to arrive sixty billionths of a second earlier than they should if travelling at the speed of light in a vacuum.

One potential source of error pointed out by other scientists was that the pulses of neutrinos sent by Cern were relatively long, around 10 microseconds each, so measuring the exact arrival time of the particles at Gran Sasso could have relatively large errors. To account for this potential problem in the latest version of the test, the beams sent by Cern were thousands of times shorter – around three nanoseconds – with large gaps of 524 nanoseconds between them. This allowed scientists to time the arrival of the neutrinos at Gran Sasso with greater accuracy.

Writing on his blog when the fine-tuned experiment started last month, Matt Strassler, a theoretical physicist at Rutgers University, said the shorter pulses of neutrinos being sent from Cern to Gran Sasso would remove the need to measure the shape and duration of the beam. "It's like sending a series of loud and isolated clicks instead of a long blast on a horn," he said. "In the latter case you have to figure out exactly when the horn starts and stops, but in the former you just hear each click and then it's already over. In other words, with the short pulses you don't need to know the pulse shape, just the pulse time."

"And you also don't need to measure thousands of neutrinos in order to reproduce the pulse shape, getting the leading and trailing edges just right; you just need a small number – maybe even as few as 10 or so – to check the timing of just those few pulses for which a neutrino makes a splash in Opera."

Around 20 neutrino events have been measured at the Gran Sasso lab in the fine-tuned version of the experiment in the past few weeks, each one precisely associated with a pulse leaving Cern. The scientists concluded from the new measurements that the neutrinos still appeared to be arriving earlier than they should.

"With the new type of beam produced by Cern's accelerators we've been able to to measure with accuracy the time of flight of neutrinos one by one," said Dario Autiero of the French National Centre for Scientific Research (CNRS). "The 20 neutrinos we recorded provide comparable accuracy to the 15,000 on which our original measurement was based. In addition their analysis is simpler and less dependent on the measurement of the time structure of the proton pulses and its relation to the neutrinos' production mechanism."

In a statement released on Friday, Fernando Ferroni, president of the Italian Institute for Nuclear Physics, said: "A measurement so delicate and carrying a profound implication on physics requires an extraordinary level of scrutiny. The experiment at Opera, thanks to a specially adapted Cern beam, has made an important test of consistency of its result. The positive outcome of the test makes us more confident in the result, although a final word can only be said by analogous measurements performed elsewhere in the world."

Since the Opera (Oscillation Project with Emulsion-tRacking Apparatus) team at Gran Sasso announced its results, physicists around the world have published scores of online papers trying to explain the strange finding as either the result of a trivial mistake or evidence for new physics.

Dr Carlo Contaldi of Imperial College London suggested that different gravitational effects at Cern and Gran Sasso could have affected the clocks used to measure the neutrinos. Others have come up with ideas about new physics that modify special relativity by taking the unexpected effects of higher dimensions into account.

Despite the latest result, said Autiero, the observed faster-than-light anomaly in the neutrinos' speed from Cern to Gran Sasso needed further scrutiny and independent tests before it could be refuted or confirmed definitively. The Opera experiment will continue to take data with a new muon detector well into next year, to improve the accuracy of the results.

The search for errors is not yet over, according to Jacques Martino, director of the National Institute of Nuclear and Particle Physics at CNRS. He said that more checks would be under way in future, including ensuring that the clocks at Cern and Gran Sasso were properly synchronised, perhaps by using an optical fibre as opposed to the GPS system used at the moment.

This would remove any potential errors that might occur due to the effects of Einstein's theory of general relativity, which says that clocks tick at different rates depending on the amount of gravitational force they experience – clocks closer to the surface of the Earth tick slower than those further away.

Even a tiny discrepancy between the clocks at Cern and Gran Sasso could be at the root of the faster-than-light results seen in September.

dauswq

Reply 9# fairluck

berkenaan hal ni, aku pernah belajar kejap..maklumlah belum amik master/phd so tak byk tau psl antimatter/matter ni...

yg aku tau neutrinos consist of matters and  antimatters depending on reaction and conditions....