- T2K
T2K (Tokai to Kamioka) is a
particle physics experiment that is currently being constructed in Japan. T2K is a second generation long baselineneutrino oscillation experiment. TheJ-PARC facility will produce an intense beam of off-axis muonneutrinos . The beam is directed towards theSuper-Kamiokande detector, which is 295 km away. The main goal of T2K is to measure the oscillation of νμ to νe and to measure the value of θ13, one of the parameters of theMaki-Nakagawa-Sakata matrix .Physics goals
The goal of the T2K experiment is to gain a more complete understanding of neutrino oscillation parameters. Previous neutrino experiments have observed the disappearance of muon neutrinos in a beam as they oscillate to tau neutrinos. but oscillation from νμ to νe has not been observed. The reason for this is believed to be that the mixing angle θ13, which controls the probability for this oscillation, is very small. T2K hopes to be the first experiment to measure the appearance of electron neutrinos in a muon neutrino beam. Precise measurements of the other neutrino mixing parameter Δm232 and θ23 are another aim of the experiment. Future upgrades to T2K could yield measurement of the CP violation phase δ by comparing oscillations of neutrinos to those of antineutrinos.
Neutrino production
JPARC
The JPARC facility is a more powerful accelerator than the KEK facility used in the K2K experiment. The main synchrotron will eventually be able to accelerate protons to 50GeV. Protons colliding with the target material will produce pions which will decay into muons which will in turn decay into muon neutrinos. The beam power is expected to be 0.75 MW delivering 110 times more neutrino events than K2K.
Off axis
The neutrino beam at JPARC is designed so that it is directed 2 to 3 degrees away from the Super-K detector. This lowers the flux of neutrinos reaching the detector but provides a more desirable neutrino energy spectrum. Off axis the peak energy is low with higher energies being suppressed. At the distance between Tokai and Kamioka maximal neutrino oscillation is expected to occur at energies lower than 1GeV.
Near detector
The near detector complex (ND280) is a segmented detector composed of neutrino targets inside a tracking system surrounded by the a magnet taken from the UA1 experiment. ND280 will be able to measure the neutrino beam’s energy spectrum, flux, flavor contents, and interaction cross-sections before the neutrino oscillation. The detector is located 280m from the target in the off axis direction.
Time projection chambers
Three
time projection chamber s will be able to measure the momenta of muon produced by charged current reactions in the detector, this information will yield the neutrino energy spectrum. Also the TPC can be used for particle identification.Fine grain detectors
Two Fine Grained Detectors (FGD) are placed after the first and second TPC’s. The first FGD is composed of several layers of segmented scintillating bars, while the second FGD is half-composed of segmented scintillating bars and half composed of water modules. The FGD’s provide the target mass for the neutrino interactions and are able to measure the short tracks of proton recoil. The second FGD is partially composed of water because the detector at Super Kamiokande is water-based thus it is important to characterize the beam's interaction with water.
Pi zero detector
The Pi zero detector is composed of layers and scintillating material and lead used to measure neutral pions produced in neutral current interactions.
The tracker and Pi zero detector are surrounded by an electromagnetic calorimeter and side range muon detector.
uper Kamiokande
The Super-Kamiokande detector is massive, even by particle physics standards. It consists of 50,000 tons of pure water surrounded by about 11,200 photomultiplier tubes. The detector was again designed as a cylindrical structure, this time 41.4 m tall and 39.3 m across. The detector was surrounded with a considerably more sophisticated outer detector which could not only act as a veto for cosmic muons but actually help in their reconstruction.
Super-Kamiokande started data taking in 1996 and has made several important measurements. These include precision measurement of the solar neutrino flux using the elastic scattering interaction, the first very strong evidence for
neutrino oscillation , and a considerably more stringent limit on proton decay.References
*cite journal | author=Y. Oyama|title = Results from K2K and status of T2K| year=2006 arxiv|archive=hep-ex|id=0512041
ee also
*
Kamioka Observatory
*Neutrino oscillation External links
* [http://jnusrv01.kek.jp/public/t2k/ Official T2K site]
* [http://phys01.comp.uvic.ca:8080/t2k T2K Canada (restricted)]
* [http://www.phys.washington.edu/~superk/ Super-Kamiokande]
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