ƁOYAYYEN MAGANAƊISUN NEUTRON, A ƘARSHE AN GAN SHI

Neutron shi kaɗai ba ya daɗewa. Yana ruɓewa zuwa proton, electron da antineutrino: wannan shi ne ruɓewar beta (beta decay), mafi sauƙin sigar wani tsari da ake samu a ko’ina a kimiyyar lissafin tsakiyar atom (nuclear physics). Tun da neutron mai ’yanci ba shi da tsakiyar atom a kewayensa, ruɓewarsa ba ta da gyare-gyare masu rikitarwa da ke dagula awon tsakiyar atom.

Hasashe daga shekarun 1950

A cikin ka’idar ƙarfi mai rauni (weak force), wata ƙa’ida da ake kira conserved vector current tana haɗa wani ɓangare na hulɗa mai rauni da electromagnetism. Ɗaya daga cikin manyan hasashenta, wanda Gell-Mann ya gabatar, shi ne weak magnetism: ƙarfi mai rauni yana ɗauke da wani abu mai kama da maganaɗisu, kamar yadda wutar lantarki ta electromagnetism ke yi. Ƙarfinsa, wanda ake rubutawa g_M, ana tantance shi ta hanyar ƙarfin maganaɗisu (magnetic moments) na proton da neutron. Ƙimar da aka hasashe ita ce 4.71.

An ga weak magnetism a wasu ruɓewar tsakiyar atom, farawa da wani gwaji na gargajiya na Lee, Mo da Wu. Amma a ruɓewar neutron mai ’yanci, mafi tsabtar yanayi a cikinsu duka, ba a taɓa auna shi kai tsaye ba.

Abubuwa biyu da ba a sani ba, awo ɗaya

Matsalar ba daidaito ba ce. Abin da ya fi ji shi ne beta asymmetry: electrons ba sa fita daidai a kowace alkibla idan aka kwatanta da juyawar (spin) neutron. Weak magnetism yana canza wannan rashin daidaito da kusan kashi 1.4%, ninki takwas na daidaiton mafi kyawun gwaji, PERKEO III.

Amma rashin daidaiton kuma ya dogara ga wata lamba ta biyu, λ, rabon manyan haɗaka (couplings) biyu na ruɓewar. Awo ɗaya ba zai iya bambance su biyun ba. Don haka masu gwaji suka tsayar da weak magnetism a ƙimar da aka hasashe kuma suka yi amfani da rashin daidaiton don auna λ.

Karya kangin

Miriam Camarasa-Domene, Martín González-Alonso (IFIC, Valencia) da Martín Novoa-Brunet (IFIC da IFAE, Barcelona) sun ɗauki λ daga wani wuri daban. Abubuwa biyu da aka auna da kyau suna tantance shi da kansu:

• tsawon rayuwar neutron, daƙiƙa 878.36 a zaɓin Particle Data Group;
• “ƙimar Ft” ta wasu ruɓewar tsakiyar atom na musamman da ke gudana ta ɓangaren vector na ƙarfi mai rauni kawai, daƙiƙa 3,070.01.

Suna haɗe da dangantakar r_n τ_n (1 + 3λ²) = 2 Ft, wadda ke ba da λ = −1.27598. Da zarar an tantance λ, awon rashin daidaito suna da ’yancin bayyana weak magnetism.

Sigma 5.1

Sakamakon: g_M = 4.47 ± 0.87, ya yi daidai da hasashen 4.71. An kawar da duniya marar weak magnetism (g_M = 0) a sigma 5.1, sama da ma’aunin sigma 5. Marubutan sun kira shi gani na farko na weak magnetism a ruɓewar neutron mai ’yanci.

Iyakoki da aka haɗa: zangon ja ya fito daga tsawon rayuwa da Ft, zangon shuɗi daga rashin daidaito; mahaɗarsu tana tantance g_M, nesa da sifili (layin ɗigo-ɗigo) kuma kusa da hasashen (layin yanke-yanke). — Figure 1, Camarasa-Domene, González-Alonso & Novoa-Brunet (2026), arXiv:2610.26792, CC BY 4.0.

An san bayanan neutron da saɓani a tsakaninsu, tsakanin tsofaffi da sabbin awon rashin daidaito da kuma tsakanin hanyoyi biyu na auna tsawon rayuwa. Don haka ƙungiyar ta maimaita nazarin da zaɓuɓɓukan bayanai daban-daban. Muhimmancin yana zama tsakanin sigma 5.0 da 6.1, kuma yana hawa zuwa 6.1 idan aka yi amfani da sabbin awon rashin daidaito kawai masu daidaituwa da juna. Wani daidaitawa na duniya baki ɗaya da ya gabata, wanda ɗaya daga cikin marubutan ya sa hannu a kai, ya sami alamar sigma 3.

Sun kuma duba ko dogaron rashin daidaiton ga kuzari zai iya taimakawa. A daidaiton yanzu, zai inganta awon da ’yan kashi kaɗan kawai.

Maɓallai uku don mataki na gaba

Abubuwa uku da aka shigar, rashin daidaito, tsawon rayuwa da ƙimomin Ft na tsakiyar atom, suna ba da gudummawa kusan daidai ga sauran rashin tabbas. Sabbin awo a kan kowane ɗaya daga cikin ukun, ko ingantattun lissafin gyare-gyaren tsakiyar atom, za su mayar da wannan gani na farko zuwa gwaji mai daidaito na Standard Model. Ana riga ana aiki a kan dukkan fagage uku.