K2K experiment: Difference between revisions
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The '''K2K experiment''' ([[KEK]] to [[Kamioka Observatory|Kamioka]]) was a [[List of neutrino experiments|neutrino experiment]] that ran from June 1999 to November 2004. It used [[muon neutrino]]s from a well-controlled and well-understood [[ |
The '''K2K experiment''' ([[KEK]] to [[Kamioka Observatory|Kamioka]]) was a [[List of neutrino experiments|neutrino experiment]] that ran from June 1999 to November 2004. It used [[muon neutrino]]s from a well-controlled and well-understood [[Accelerator neutrino|beam]] to verify the [[neutrino oscillation|oscillations]] previously observed by [[Super-Kamiokande]] using [[Neutrino#Atmospheric neutrinos|atmospheric neutrinos]]. This was the first positive measurement of [[neutrino oscillations]] in which both the source and detector were fully under experimenters' control.<ref> |
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{{cite journal |
{{cite journal |
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|author= |
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|date=18 August 2000 |
|date=18 August 2000 |
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|title=Synthetic neutrinos appear to disappear |
|title=Synthetic neutrinos appear to disappear |
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{{cite journal |
{{cite journal |
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|author=N. Nosengo |
|author=N. Nosengo |
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|date=2006 |
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|title=Neutrinos make a splash in Italy |
|title=Neutrinos make a splash in Italy |
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|journal=[[Nature (journal)|Nature]] |
|journal=[[Nature (journal)|Nature]] |
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|volume=443 |issue=7108 |pages=126 |
|volume=443 |issue=7108 |pages=126 |
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|doi=10.1038/443126a |
|doi=10.1038/443126a |
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|bibcode = 2006Natur.443..126N |url=https://cds.cern.ch/record/988253 |
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|doi-access=free |
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==Experimental design== |
==Experimental design== |
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[[Image:Super-k.jpg|thumb |
<!-- Deleted image removed: [[Image:Super-k.jpg|thumb|The inside of the 50-kiloton [[Super-Kamiokande]] detector ("far detector").]] --> |
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K2K is a [[List of neutrino experiments|neutrino experiment]] which directed a beam of [[muon neutrino]]s ({{ |
K2K is a [[List of neutrino experiments|neutrino experiment]] which directed a [[Accelerator neutrino|beam]] of [[muon neutrino]]s ({{Subatomic particle|muon neutrino}}) from the {{val|12|ul=GeV}} [[proton]] [[synchrotron]] at the [[KEK]], located in [[Tsukuba, Ibaraki|Tsukuba]], [[Ibaraki Prefecture|Ibaraki]], to the [[Kamioka Observatory]], located in [[Kamioka]], [[Gifu Prefecture|Gifu]], about 250 km away.<ref name="K2K intro"> |
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{{cite web |
{{cite web |
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|date=13 June 2002 |
|date=13 June 2002 |
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|url=http://neutrino.kek.jp/intro/k2k.html |
|url=http://neutrino.kek.jp/intro/k2k.html |
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|publisher=[[KEK|High Energy Accelerator Research Organization]] |
|publisher=[[KEK|High Energy Accelerator Research Organization]] |
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|access-date=2010-09-03 |
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}}</ref> The muon neutrinos travelled through [[Earth]], which allowed them to [[neutrino oscillation|oscillate]] (change) into other [[flavour (particle physics)|flavours]] of [[neutrino]]s, namely into [[electron neutrino]]s ({{ |
}}</ref> The muon neutrinos travelled through [[Earth]], which allowed them to [[neutrino oscillation|oscillate]] (change) into other [[flavour (particle physics)|flavours]] of [[neutrino]]s, namely into [[electron neutrino]]s ({{Subatomic particle|electron neutrino}}) and [[tau neutrino]]s ({{Subatomic particle|tau neutrino}}). K2K however, focused only on {{nowrap|{{Subatomic particle|muon neutrino}} → {{Subatomic particle|tau neutrino}}}} oscillations.<ref name="K2K results"/> |
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The proton beam from the synchrotron was directed onto an [[aluminium]] target, and the resulting collisions produced a copious amount of [[pion]]s. These pions were then focused into a 200 m decay pipe, where they would [[particle decay|decay]] into [[muon]]s and [[muon neutrino]]s.<ref name="K2K intro"/> |
The proton beam from the synchrotron was directed onto an [[aluminium]] target, and the resulting collisions produced a copious amount of [[pion]]s. These pions were then focused into a 200 m decay pipe, where they would [[particle decay|decay]] into [[muon]]s and [[muon neutrino]]s.<ref name="K2K intro"/> The muons were stopped at the end of the pipe, leaving a beam of muon neutrinos. The exact composition of the beam contained over 97% muon neutrinos, with the other 3% being made of electron neutrinos ({{Subatomic particle|electron neutrino}}), electron antineutrinos ({{Subatomic particle|electron antineutrino}}) and muon antineutrinos ({{Subatomic particle|muon antineutrino}}).<ref name="K2K results"/> |
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After they exited the pipe, the neutrinos went through a 1-kiloton [[water]] [[Cherenkov detector|Cherenkov]] [[neutrino detector]] ("near detector") located at about 300 m from the aluminium target to determine the neutrino beam characteristics. This 1-kiloton "near detector" was a scaled-down version of the 50-kiloton [[Super-Kamiokande]] "far detector" located at the [[Kamioka Observatory]], which allowed scientists to eliminate certain systematic uncertainties that would be present if two different detector types were used.<ref name=NEAR> |
After they exited the pipe, the neutrinos went through a 1-kiloton [[water]] [[Cherenkov detector|Cherenkov]] [[neutrino detector]] ("near detector") located at about 300 m from the aluminium target to determine the [[Accelerator neutrino|neutrino beam]] characteristics. This 1-kiloton "near detector" was a scaled-down version of the 50-kiloton [[Super-Kamiokande]] "far detector" located at the [[Kamioka Observatory]], which allowed scientists to eliminate certain systematic uncertainties that would be present if two different detector types were used.<ref name=NEAR> |
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{{cite web |
{{cite web |
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|author= |
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|date=19 June 1999 |
|date=19 June 1999 |
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|title=K2K: Near Detector |
|title=K2K: Near Detector |
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|url=http://k2k.physics.sunysb.edu/k2k/near_detector.shtml |
|url=http://k2k.physics.sunysb.edu/k2k/near_detector.shtml |
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|publisher=[ |
|publisher=[Stony Brook Super-Kamiokande/K2K group] |
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|access-date=2010-09-03 |
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}}</ref> This dual-detector configuration allowed the comparison of the neutrino beam at the near detector with the neutrino beam at the far detector to determine if neutrinos had oscillated or not.<ref name="K2K intro-2"> |
}}</ref> This dual-detector configuration allowed the comparison of the neutrino beam at the near detector with the neutrino beam at the far detector to determine if neutrinos had oscillated or not.<ref name="K2K intro-2"> |
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{{cite web |
{{cite web |
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|author= |
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|date=20 June 1999 |
|date=20 June 1999 |
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|title=K2K: Introduction |
|title=K2K: Introduction |
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|url=http://k2k.physics.sunysb.edu/k2k/intro.shtml |
|url=http://k2k.physics.sunysb.edu/k2k/intro.shtml |
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|publisher=[ |
|publisher=[Stony Brook Super-Kamiokande/K2K group] |
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|access-date=2010-09-03 |
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}}</ref> |
}}</ref> |
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The K2K collaboration consisted of roughly 130 physicists from 27 universities and research institutes from all over the world, listed below.<ref> |
The K2K collaboration consisted of roughly 130 physicists from 27 universities and research institutes from all over the world, listed below.<ref> |
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{{cite web |
{{cite web |
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|author= |
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|date=20 January 2004 |
|date=20 January 2004 |
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|title=K2K Member Institutes |
|title=K2K Member Institutes |
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|url=http://neutrino.kek.jp/member.html |
|url=http://neutrino.kek.jp/member.html |
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|publisher=[[KEK|High Energy Accelerator Research Organization]] |
|publisher=[[KEK|High Energy Accelerator Research Organization]] |
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|access-date=2010-09-03 |
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}}</ref> The full list of scientists and their countries of origin is available on the [http://neutrino.kek.jp/member.html K2K website]. |
}}</ref> The full list of scientists and their countries of origin is available on the [http://neutrino.kek.jp/member.html K2K website]. |
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{{div col|colwidth=22em}} |
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{{columns-list|2| |
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*[[Boston University]] |
*[[Boston University]] |
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*[[Chonnam National University]] |
*[[Chonnam National University]] |
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*[[CEA |
*[[CEA Saclay]] (DSM-DAPNIA) |
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*[[Dongshin University]] |
*[[Dongshin University]] |
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*[[KEK|High Energy Accelerator Research Organization]] |
*[[KEK|High Energy Accelerator Research Organization]] |
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*[[Tokyo University of Science]] |
*[[Tokyo University of Science]] |
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*[[Tohoku University]] |
*[[Tohoku University]] |
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*[[University of Barcelona]] |
*[[Autonomous University of Barcelona]]/[[IFAE]] |
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*[[University of California, Irvine]] |
*[[University of California, Irvine]] |
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*[[University of Geneva]] |
*[[University of Geneva]] |
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*[[University of Hawaii]] |
*[[University of Hawaii]] |
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*[[University of Tokyo]] |
*[[University of Tokyo]] |
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*[[University of Valencia]] |
*[[University of Valencia]] |
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*[[University of Warsaw]] |
*[[University of Warsaw]] |
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⚫ | |||
}} |
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{{div col end}} |
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==Results== |
==Results== |
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The final K2K results found that at 99.9985% confidence (4.3 [[standard deviation| |
The final K2K results found that at 99.9985% confidence (4.3 [[standard deviation|σ]]) there had been a disappearance of muon neutrinos. Fitting the data under the oscillation hypothesis, the [[curve fitting|best fit]] for the square of the mass difference between muon neutrinos and tau neutrinos was Δ''m''<sup>2</sup> = {{val|2.8|e=-3|u=eV<sup>2</sup>}}.<ref name="K2K results"> |
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{{cite journal |
{{cite journal |
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|author = M. H. Ahn |
|author = M. H. Ahn |
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|collaboration=[[K2K experiment#Collaboration|K2K Collaboration]] |
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|year = 2006 |
|year = 2006 |
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|title = Measurement of Neutrino Oscillation by the K2K Experiment |
|title = Measurement of Neutrino Oscillation by the K2K Experiment |
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|volume = 74|pages = 072003 |
|volume = 74|pages = 072003 |
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|doi = 10.1103/PhysRevD.74.072003 |
|doi = 10.1103/PhysRevD.74.072003 |
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| |
|arxiv=hep-ex/0606032 |
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|bibcode = 2006PhRvD..74g2003A |
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|issue = 7 |s2cid=22053653 |
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}}</ref> This result is in good agreement with the previous [[Super-Kamiokande]] result,<ref> |
}}</ref> This result is in good agreement with the previous [[Super-Kamiokande]] result,<ref> |
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{{cite journal |
{{cite journal |
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|author=Y. Fukuda |
|author=Y. Fukuda |
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|collaboration=[[Super-Kamiokande|Super-K Collaboration]] |
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|date=1998 |
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|title=Measurements of the Solar Neutrino Flux from Super-Kamiokande's First 300 Days |
|title=Measurements of the Solar Neutrino Flux from Super-Kamiokande's First 300 Days |
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|journal=[[Physical Review Letters]] |
|journal=[[Physical Review Letters]] |
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|volume=81 |pages= |
|volume=81 |pages=1158–1162 |
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|doi=10.1103/PhysRevLett.81.1158 |
|doi=10.1103/PhysRevLett.81.1158 |
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|bibcode=1998PhRvL..81.1158F |
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|arxiv = hep-ex/9805021 |
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|issue=6 |s2cid=14217731 |
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⚫ | |||
|author=<!--No need for them--> |
|author=<!--No need for them--> |
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|date=1998 |
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|title=Erratum: Measurements of the Solar Neutrino Flux from Super-Kamiokande's First 300 Days |
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|title=<!--No need for it--> |
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|journal=[[Physical Review Letters]] |
|journal=[[Physical Review Letters]] |
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|volume=81 |pages=4279 |
|volume=81 |pages=4279 |
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|doi=10.1103/PhysRevLett.81.4279 |
|doi=10.1103/PhysRevLett.81.4279 |
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|bibcode=1998PhRvL..81.4279F |
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⚫ | |||
|issue=19 |
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|doi-access=free |
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{{cite journal |
{{cite journal |
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|author=D.G. Michael |
|author=D.G. Michael |
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|collaboration=[[MINOS|MINOS Collaboration]] |
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|year=2006 |
|year=2006 |
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|title=Observation of muon neutrino disappearance with the MINOS detectors in the NuMI neutrino beam |
|title=Observation of muon neutrino disappearance with the MINOS detectors in the NuMI neutrino beam |
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|volume=97 |pages=191801 |
|volume=97 |pages=191801 |
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|doi=10.1103/PhysRevLett.97.191801 |
|doi=10.1103/PhysRevLett.97.191801 |
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|pmid=17155614 |
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|arxiv=hep-ex/0607088 |
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⚫ | |||
|bibcode=2006PhRvL..97s1801M |
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|issue=19 |
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|s2cid=119458915 |
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==See also== |
==See also== |
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==References== |
==References== |
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{{ |
{{reflist}} |
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==External links== |
==External links== |
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*[http://neutrino.kek.jp/publications/ K2K publications] |
*[http://neutrino.kek.jp/publications/ K2K publications] |
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{{Breakthrough Prize laureates}} |
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{{neutrino detectors}} |
{{neutrino detectors}} |
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Latest revision as of 14:40, 12 February 2024
The K2K experiment (KEK to Kamioka) was a neutrino experiment that ran from June 1999 to November 2004. It used muon neutrinos from a well-controlled and well-understood beam to verify the oscillations previously observed by Super-Kamiokande using atmospheric neutrinos. This was the first positive measurement of neutrino oscillations in which both the source and detector were fully under experimenters' control.[1][2] Previous experiments relied on neutrinos from the Sun or from cosmic sources. The experiment found oscillation parameters which were consistent with those measured by Super-Kamiokande.
Experimental design
[edit]K2K is a neutrino experiment which directed a beam of muon neutrinos (
ν
μ) from the 12 GeV proton synchrotron at the KEK, located in Tsukuba, Ibaraki, to the Kamioka Observatory, located in Kamioka, Gifu, about 250 km away.[3] The muon neutrinos travelled through Earth, which allowed them to oscillate (change) into other flavours of neutrinos, namely into electron neutrinos (
ν
e) and tau neutrinos (
ν
τ). K2K however, focused only on
ν
μ →
ν
τ oscillations.[4]
The proton beam from the synchrotron was directed onto an aluminium target, and the resulting collisions produced a copious amount of pions. These pions were then focused into a 200 m decay pipe, where they would decay into muons and muon neutrinos.[3] The muons were stopped at the end of the pipe, leaving a beam of muon neutrinos. The exact composition of the beam contained over 97% muon neutrinos, with the other 3% being made of electron neutrinos (
ν
e), electron antineutrinos (
ν
e) and muon antineutrinos (
ν
μ).[4]
After they exited the pipe, the neutrinos went through a 1-kiloton water Cherenkov neutrino detector ("near detector") located at about 300 m from the aluminium target to determine the neutrino beam characteristics. This 1-kiloton "near detector" was a scaled-down version of the 50-kiloton Super-Kamiokande "far detector" located at the Kamioka Observatory, which allowed scientists to eliminate certain systematic uncertainties that would be present if two different detector types were used.[5] This dual-detector configuration allowed the comparison of the neutrino beam at the near detector with the neutrino beam at the far detector to determine if neutrinos had oscillated or not.[6]
Collaboration
[edit]The K2K collaboration consisted of roughly 130 physicists from 27 universities and research institutes from all over the world, listed below.[7] The full list of scientists and their countries of origin is available on the K2K website.
- Boston University
- Chonnam National University
- CEA Saclay (DSM-DAPNIA)
- Dongshin University
- High Energy Accelerator Research Organization
- Hiroshima University
- Institute for Cosmic Ray Research
- Institute for Nuclear Research
- Kobe University
- Korea University
- Kyoto University
- Massachusetts Institute of Technology
- Niigata University
- Okayama University
- Sapienza University of Rome
- Seoul National University
- State University of New York at Stony Brook
- Tokyo University of Science
- Tohoku University
- Autonomous University of Barcelona/IFAE
- University of California, Irvine
- University of Geneva
- University of Hawaii
- University of Tokyo
- University of Valencia
- University of Warsaw
- University of Washington
Results
[edit]The final K2K results found that at 99.9985% confidence (4.3 σ) there had been a disappearance of muon neutrinos. Fitting the data under the oscillation hypothesis, the best fit for the square of the mass difference between muon neutrinos and tau neutrinos was Δm2 = 2.8×10−3 eV2.[4] This result is in good agreement with the previous Super-Kamiokande result,[8] and the later MINOS result.[9]
See also
[edit]- T2K experiment – the successor of the K2K experiment
References
[edit]- ^ "Synthetic neutrinos appear to disappear". CERN Courier. 40 (7). 18 August 2000.
- ^ N. Nosengo (2006). "Neutrinos make a splash in Italy". Nature. 443 (7108): 126. Bibcode:2006Natur.443..126N. doi:10.1038/443126a. PMID 16971911.
- ^ a b "Long Baseline neutrino oscillation experiment, from KEK to Kamioka (K2K)". High Energy Accelerator Research Organization. 13 June 2002. Retrieved 3 September 2010.
- ^ a b c M. H. Ahn; et al. (K2K Collaboration) (2006). "Measurement of Neutrino Oscillation by the K2K Experiment". Physical Review D. 74 (7): 072003. arXiv:hep-ex/0606032. Bibcode:2006PhRvD..74g2003A. doi:10.1103/PhysRevD.74.072003. S2CID 22053653.
- ^ "K2K: Near Detector". [Stony Brook Super-Kamiokande/K2K group]. 19 June 1999. Retrieved 3 September 2010.
- ^ "K2K: Introduction". [Stony Brook Super-Kamiokande/K2K group]. 20 June 1999. Retrieved 3 September 2010.
- ^ "K2K Member Institutes". High Energy Accelerator Research Organization. 20 January 2004. Retrieved 3 September 2010.
- ^ Y. Fukuda; et al. (Super-K Collaboration) (1998). "Measurements of the Solar Neutrino Flux from Super-Kamiokande's First 300 Days". Physical Review Letters. 81 (6): 1158–1162. arXiv:hep-ex/9805021. Bibcode:1998PhRvL..81.1158F. doi:10.1103/PhysRevLett.81.1158. S2CID 14217731. and erratum "Erratum: Measurements of the Solar Neutrino Flux from Super-Kamiokande's First 300 Days". Physical Review Letters. 81 (19): 4279. 1998. Bibcode:1998PhRvL..81.4279F. doi:10.1103/PhysRevLett.81.4279.
- ^ D.G. Michael; et al. (MINOS Collaboration) (2006). "Observation of muon neutrino disappearance with the MINOS detectors in the NuMI neutrino beam". Physical Review Letters. 97 (19): 191801. arXiv:hep-ex/0607088. Bibcode:2006PhRvL..97s1801M. doi:10.1103/PhysRevLett.97.191801. PMID 17155614. S2CID 119458915.