Long-Baseline news, SPECIAL EDITION Early June 1998

*** Super-Kamiokande reports neutrino mass is non-zero

In an announcement at Neutrino '98, Super-Kamiokande described its very strong evidence that neutrino oscillations are needed to explain their atmospheric neutrino data. See www.phys.washington.edu/~superk/sk_release.html. Data from their contained events, partially contained events, Multi-Gev events, upward muons and upward stopping muons all differ from expectation but can be explained with large mixing and delta msquared of a few times 10**-3. Watch for two New York Times articles starting with the front page of the Friday June 5 issue.

*** Super-Kamiokande; contained events, zenith, neutral current

With 535 days of data, Super-Kamiokande has 3032 1-ring events, 1018 2-ring, 426 >2-ring, and 301 partially contained events(PCE). Expected were 3223, 1076, 465 and 372. The Sub-GeV R is 0.627 +- .026 +- .05 and the Multi-Gev value is .647 +- .049 +- .078. The zenith angle distribution fits nicely to 5 10**-3 eV^2 with sin^2 theta=1 for the sub-GeV, Multi-GeV and PCE data. If there was a problem with the neutrino flux, it might show up in the (neutral current) pi0 events. But [pi0/e)(data)]/[pi0/e(MC)] is 0.94 +- .08(stat) +- 0.03(MC-stat) +- 0.19(syst)

*** more Super-Kamiokande results; azimuthal angle, upware mus

Neutrino Oscillations can cause zenith angle changes, but not azimuth angle changes for contained events. Noticable azimuth effects are expected from geomagnetic effects for certain energies. Effects are seen as expected, giving confidence that the measured zenith angle anomalies are real. Upward muons and upward stopping muon angular distributions provide two more independent data sets to study for oscillation effects. Analysis of both data sets gives a poor chi-squared without oscillations and a good chi-squared when large mixing and 5 10**-3 eV^2 numu to nutau oscillations are put in.

*** Japanese budget cuts threaten Super-Kamiokande operations.

Due to the financial difficulty of the Japanese government, operating funds for Super-Kamiokande have been reduced by 15% for 1998. This may require them to cease operation for 2 months. An additional 15% cut is expected next year. Under these circumstances, they will have to stop the operation of the experiment,probably for 4 months. These cuts are being applied equally, across-the-board, to all institutions, without consideration of the relative scientific importance of the projects or the devastating impact that such cuts may have.

*** K2K schedule

K2K will turn on at 0001 on Jan 1, 1999 (Japanese time), using a fast spill. They will run 3-5 months, being off during the summer and slow spill at KEK. Super-Kamiokande plans to empty during the summer of 1999 to replace some tubes. The K2K run is expected to take 3 years with 6 months of running per year.

*** Soudan 2 flavor ratio still low

Soudan 2 now has double the fiducial exposure of the Frejus experiment. From 3.56 fiducial kiloton years, the neutrino flavor ratio is 0.58 +/- 0.11 +/- 0.06. Soudan 2 has isolated a sample of nu-mu flavor events for which the resolution in L/Enu for incident neutrinos is excellent, as the result of imaging of the recoiling hadronic system. In this sample of events, with Enu between 0.5 to 2.0 GeV, the nu-mu flux appears depleted in both down-going as well as up-going neutrinos.

*** Diablo Avocado still skeptical (but mellowing?) about nu-osc

While he cannot find anything wrong with the Super-Kamiokande analysis, Diablo Avocado is still skeptical about neutrino oscillations. Why are the parameters so conveniently those that show up in atmospheric neutrinos where we have no control over the beam? Why maximal mixing? He will be watching the long-baseline results with great interest, although it now appears that they will not be able to completely rule out Super-K if they come out negative.

*** MINOS tubes held hostage by NASA

MINOS has a choice between an existing Hamamatsu phototube, and a newer 61-ch tube being prototyped by DEP, which was ordered for testing many moons ago. The package finally came, but inside was a Power Supply. Customs people said that by mistake NASA has MINOS' DEP tubes and MINOS has their Power Supply. The Power Supply is sent back. Does NASA do the same? Nooooo-ooh. (Try that a la Bill Murray) NASA told the customs people that they will not even begin to send the tubes back to be sent to MINOS until they get their Power Supply ... due to "government regulations".

*** CERN research board hears about neutrino momentum

At their April 1998 meeting, it was reported the SPSC felt that TOP, a proposal for a TOSCA prototype was now premature. It was also reported that the INFN had included a sizeable fraction of the cost of the Gran Sasso neutrino beam in its next 5-year plan which is to be be discussed in the coming months. This new beam was thus gathering momentum.

*** Notable new references

Maury Goodman,
mail to- maury.goodman@anl.gov
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