ALAMA MARA ƘARFI TA NEUTRINO DA DUKKAN SUPERNOVA NA DA SUKA BARI

Sau ’yan kaɗan a kowace daƙiƙa, a wani wuri a sararin duniya da ake iya gani (observable universe), cibiyar wani tauraro tana rushewa. Ana tsammanin kowace rushewa za ta saki makamashi mai yawan gaske, kusan erg 10⁵³ (joule 10⁴⁶), kuma kusan 99% ɗinsa neutrino ne ke ɗauke da shi, ƙwayoyi kusan marasa nauyi da ke ratsa kusan dukkan abubuwa. Amma tarin neutrino daga supernova na kusa suna zuwa ne sau ’yan kaɗan kawai a kowane ƙarni. Tun bayan neutrino 24 da aka kama daga supernova SN 1987A, sake kama neutrino na supernova ya kasance babban buri na ilimin falakin neutrino (neutrino astronomy).

Jimillar kowace rushewa tun lokacin da taurari suka fara samuwa

Akwai wata hanyar shiga. Ka haɗa neutrino na dukkan rushewar cibiyoyin taurari tun lokacin da samuwar taurari ta fara, sai ka sami bangon neutrino na supernova mai yaɗuwa (diffuse supernova neutrino background, DSNB): kwarara (flux) mai dorewa da ke zuwa daidai wa daida daga kowace hanya. Bakansa (spectrum) — yawan neutrino a kowane matakin makamashi — zai faɗi wani abu game da yadda taurari ke rushewa, wane kaso na rushewar ke samar da baƙaƙen ramuka (black holes), da yadda sinadaran damin taurari (galaxies) suka sauya a tsawon lokaci.

Akwai hasashe da yawa. An yi bincike a cikin na’urorin ganowa (detectors) na ruwa da na ruwa mai walƙiya (liquid scintillator), amma har zuwa yanzu babu wanda ya sami wani ƙari mai muhimmanci, kuma wannan ma, kamar yadda aka nuna a ƙasa, har yanzu alama ce kawai.

Walƙiya, sannan neutron

Rushewa tana fitar da kowane nau’in neutrino. Mafi yawan bincike, har da wannan, suna nufin ɗaya daga cikinsu, antineutrino na electron (ν̄e), ta hanyar wata mu’amala (reaction) da proton:

ν̄e + p → e⁺ + n

Proton ɗin yana zama positron (e⁺, electron mai cajin tabbatacce) da neutron. A kewayon makamashi da ke da muhimmanci a nan, kusan MeV 10 zuwa 30 (miliyoyin electronvolt), wannan mu’amala ta fi yiwuwa da kusan ninki ɗari fiye da neutrino ya bugi electron ya yi tsalle.

Super-Kamiokande (SK) wani katon tanki ne na ruwa da na’urorin jin haske ke sa ido a kansa, a cikin mahakar Kamioka, a Gifu, Japan; binciken yana amfani da kilotan 22.5 na ruwansa. Ƙwaya mai caji mai sauri da ke ratsa ruwan tana fitar da ɗan haske mara ƙarfi mai siffar mazugi (cone), da ake kira hasken Cherenkov: na positron ɗin bututun photomultiplier (photomultiplier tubes, wato na’urorin jin hasken) ne ke rubuta shi. Bayan ɗan lokaci kaɗan, wata cibiyar zarra (atomic nucleus) tana kama neutron ɗin, sai ta saki wani tarin haske na biyu mafi rauni: bayan kusan microsecond 200 a cikin ruwa tsantsa, kusan 60 da zarar an narkar da gadolinium a ciki, wani ƙarfe da ke kama neutron cikin sauƙi fiye da haka nesa, a kaso 0.033%. Ganin walƙiyar sannan kamawar — “yi wa neutron alama” (neutron tagging) — yana da muhimmanci, domin siginar da ake tsammani abubuwa ’yan kaɗan ne kawai a shekara.

Kwanaki 5,003 a matakai shida

Bayanan sun fara daga Oktoba 2008 zuwa Maris 2026: kwanaki 5,003.0 na rikodi, a matakai shida. Biyun farko sun yi amfani da ruwa tsantsa. Sannan aka narkar da gadolinium sulfate a ciki: ton 13, sannan ƙarin ton 26.1, wanda ya ɗaga kason neutron da gadolinium ke kamawa daga 50% zuwa 75%. Kason neutron da aka yi wa alama ya ƙaru tare da shi: 10–30% a ruwa tsantsa, 60–70% a mafi girman yawan narkewa (concentration). A Oktoba 2023, lalacewar na’urorin waya (coils) da ke soke maganaɗisun Duniya (magnetic field) a kewayen na’urar ganowar ta rage ƙarfin wasu na’urorin jin haske na tsawon kwanaki 191.8, har aka gyara.

Abubuwan da ake zato (candidate events) suna taruwa a cikin matakai shida: jimilla (shuɗi), masu daidai neutron ɗaya da aka yi wa alama (ja) ko marasa shi (kore); layin ja yana ƙara tsaurin hawa bayan sanya gadolinium. — Figure 4, Abe et al. (2026), arXiv:2610.35619.

Masu kwaikwayo da suka fi yawa da ninki miliyan

Muon na hasken sararin samaniya (’yan uwan electron masu nauyi, waɗanda ke samuwa idan hasken sararin samaniya ya bugi saman sararin iska) suna farfasa cibiyoyin oxygen a cikin ruwan su zama isotope masu fitar da hasken nukiliya (radioactive isotopes), waɗanda rubewarsu (decays) ta fi siginar da ake tsammani yawa har zuwa miliyan ɗaya da ɗaya ƙasa da kusan MeV 20. Mafi yawansu ba sa fitar da neutron, don haka buƙatar neutron tana kawar da su. Lithium-9 ita ce banda: tana rubewa ta zama electron da neutron, cikakken kwafin siginar (rabin rai, half-life: daƙiƙa 0.178).

Neutrino na sararin iska (atmospheric neutrinos) su ne ɗayan tarkon. Wasu suna fitar da neutron daga cibiyar zarra kuma su saki hasken gamma (gamma rays), suna kwaikwayon ma’auratan walƙiya da neutron. Wasu kuma suna samar da muon, wanda ke rubewa cikin ’yan microsecond ya zama electron; tare da neutron, wannan ma’aurata ma tana kwaikwayon siginar. Sabon binciken ya ƙara:

• matatar koyon na’ura (machine learning) ga waɗannan masu kwaikwayo na hasken gamma, wadda ke riƙe 89% na ainihin siginar maimakon 79%, kuma ta rage sauran masu kwaikwayon da rabi, daga 10% zuwa 5%;
• hanyar bambance electron na rubewar muon da kamawar gadolinium, maimakon yanke abubuwan da a da ke jawo asarar kusan 10% na siginar;
• rashin tabbas mafi ƙanƙanta: 45% maimakon 70% a kan yawan waɗannan abubuwa na sararin iska, 30% maimakon 50% a kan lithium-9 da ya rage.

Zaɓi ɗaya ya bi akasin hanya. A shekarun ruwa tsantsa, a cikin abubuwan da ba su da daidai neutron ɗaya da aka yi wa alama, daidaitawar (fit) ta sami wata ƙarin gudummawa a makamashin da aka auna tsakanin MeV 15.5 da 21.5, kusan girman siginar supernova da ake tsammani a wurin — mai yiwuwa, in ji marubutan, ragowar tarkacen hasken sararin samaniya da samfurinsu ya kasa kamawa. Sun ɗaga iyakar farawa (threshold) ga waɗannan abubuwa zuwa MeV 21.5 a kowane mataki, kuma sun saukar da ita daga MeV 15.5 zuwa 11.5 ga abubuwan da ke da daidai neutron ɗaya da aka yi wa alama. Tare, sauye-sauyen biyu sun jawo asarar 13.9% na siginar da ake tsammani.

Abin da sigma 2.6 ke faɗi, da abin da ba ya faɗi

Daidaitawar ƙarshe tana haɗa dukkan matakai, yankunan bayanai shida da abubuwan haɗi bakwai: siginar tare da nau’o’in hayaniyar baya (backgrounds) shida. Da samfurin tunani (reference model) don siffar siginar (Horiuchi da abokan aikinsa, 2009):

• kwarara mafi dacewa: antineutrino 3.6 (+1.6/−1.5) a kowane santimita murabba’i a kowace daƙiƙa sama da MeV 13.3, ko abubuwa 4.8 (+2.2/−2.0) a shekara a SK;
• muhimmanci (significance): sigma 2.6;
• matakan gadolinium kaɗai (kwanaki 1,653.7): sigma 2.2; matakan ruwa tsantsa kaɗai (kwanaki 3,349.3): sigma 1.4 — yadda gadolinium ya fi kyau nesa ba kusa ba wajen yi wa neutron alama ya rinjayi gajeren lokacin aikinsa;
• wasu siffofin sigina biyu suna ba da sigma 2.7 da 2.6;
• kwararar tana kusa da saman kewayon 2.1 zuwa 3.9 da samfurin tunani ke hasashe.

Me sigma 2.6 ke nufi? Idan SK yana rikodin hayaniyar baya kaɗai, ba tare da neutrino na supernova ko kaɗan ba, bayanai irin waɗannan ba za su cika yiwuwa ba: marubutan sun nuna rashin dacewar wannan hasashe na “babu komai sai hayaniyar baya” a matakin tabbaci na 99.5%. Shi ya sa suke kiransa alama (indication) — a kalmominsu, ta farko ga wannan sigina — maimakon abin da aka lura (observation).

Yadda kowace kwarara ke rashin dacewa da bayanan (baƙi: dukkan matakai; layin ɗigo-ɗigo: kowane mataki shi kaɗai): layin yana kaiwa ƙasa kusa da 3.6, kuma a kwarara sifili yana hawa tsakanin layukan sigma 2 da sigma 3. — Figure 5, Abe et al. (2026), arXiv:2610.35619.

Ƙirga mafi sauƙi, saɓani mafi rauni

Wani bincike na tabbatarwa (cross-check) da bai ɗauki wata siffa ga siginar ba — kawai ƙirga waɗanda ake zato masu neutron ɗaya da aka yi wa alama tsakanin MeV 13.3 da 31.3 idan aka kwatanta da hayaniyar baya da ake tsammani — yana ba da saɓani (tension) na sigma 1.8 kawai. Kuma sama da MeV 17.3, sabuwar kwararar, 1.8 (+0.8/−0.7) a kowane santimita murabba’i a kowace daƙiƙa, ta yi daidai, cikin iyakokin rashin tabbas ɗinta, da 1.4 (+1.5/−1.2) da binciken baya na ƙungiyar haɗin gwiwar (collaboration) ya samu a kan bayanan gadolinium kaɗai.