Minutes from February 21-22 Meetings

February 21 Targeting Discussion Lead by Kirk McDonald

First, a list of links with the plots that were shown:
The general repository for documents on targetry for neutrino factories and muon colliders is www.hep.princeton.edu/~mcdonald/mumu/target/

The NLC positron source page is www-project.slac.stanford.edu/lc/local/systems/Injector/PositronSource.htm

Kirk's talk was loosely based on 2 recent presentations:

Additional info on results from beam tests is in pubweb.bnl.gov/users/kirk/www/e951/iit_feb_02/beam_studies.pdf

and afabich.home.cern.ch/afabich/docs/NFWGJan2002.pdf

More info on the FEA simulations is in www.hep.princeton.edu/~mcdonald/mumu/target/Samulyak_Chicago_09_02.pdf

Futuristic targets for neutron spallation sources are discussed at www.hep.princeton.edu/~mcdonald/mumu/target/pb-bi/
Brief Synopsis of Talk:
The important thing to remember about targeting issues is that you will worry much more about radiation effects and infrastructure than you will worry about the target itself. The amount of cement needed in these targeting facilities Kirk describes is staggering.
General Structure of Talk:
800kw beam from Los Alamos:
on a 1 interaction length Tungsten Target --cooling water is flowing on that target. Another idea (used by g-2 experiment) is a rorating target.
Results from the SNS at Oak Ridge:
the baseline design was flowing Hg in a stainless steel jacket, but a single pulse puts a pit in the entrance window which is stainless steel. This was 1-2MW 1 microsecond pulse, 50Hz, 1GeV protons. conclusion: putting liquid target in pipe requires extreme care.
3.5MW Deuterium source at Hanford Reactor:
35MeV Deuterium was to be put on a flowing Li target, with a free surface facing the beam to not have this pitting problem mentioned above. This project was cancelled though.
Targets for Making Neutrino Beams: What target you want depends on what neutrino energy you want. Optimization is different if you want high versus if you want low energies. For 8GeV protons, pion production is constant vs. A of the target material. But for 30GeV protong the production is not constant--you win by going to higher A material. Studies of Sublimation of targets have been done: if target is in vacuum this is the limiting factor and it happens very quickly (1 day). If target is at 1atm of He gas, then longer-term radiation damage is the worry.
There is a carbon carbon composite with 0 thermal expansion.

With liquid targets in high magnetic fields, magnetohydrodynamics becomes an issue. With solid targets there is good agreement between measured strain and the calculations. Single pulse accidents are NOT an issue at the considered intensity.
February 22 Theory Overview Talk by Andre de Gouvea On Feb. 22 Andre de Gouvea gave a thorough overview of the current status of neutrino oscillation measurements and where things are going.

One topic which inspired lots of discussion was showing the effect of the CHOOZ limit on the atmospheric allowed regions...for certain values of sin2 2theta_13. For example, if sin2 2theta_13 is large, then this effectively means that delta m^2 (23) is "low", since the chooz limit is very quikly changing as a function of delta in the interesting region. Also different parts of the solar allowed regions change when you dial in different sin2 2theta_13 values in conjunction with the CHOOZ bound.

One interesting way to look at this that Andre mentioned is that theta_13 may actually be bigger than the cabibbo angle--we don't know that it's not right now!

There was much discussion about KAMLAND, and the sensitivity they may actually have for delta m2 measurements--he showed some energy spectra that would be expected for different delta m2 values. Without the solar measurements KAMLAND can't determine if the mixing angle is on the "dark" side or the "light" side.

Andre also showed how one must keep all these different terms in the oscillation probabilities when one is trying to determine what the reach of off-axis (or other future) experiments are: it's not enough just to keep the largest term and the CP violating, there's the cosine delta term, and of course the higher mass splitting term. The question "how well can a minos off-axis experiment do in CP" can be answered in a few ways: recall that you can do disappearance with the on-axis detector, as well as appearance and disappearance with the off-axis detectors. The variables we have to play with are as follows: would we be better off running in antineutrino and neutrino, or having two detectors at the same energy but different baselines, or two detectors at different angles which would give you slightly different energies as well?
Deborah Harris
Last modified: Tue Feb 26 13:51:47 CST 2002