PBEAM Studies

Comparisons between PBEAM and GNUMI
August 27:
nominal pbeam/gnumi for various combinations of horn material, chase material, secondaries, and no secondaries.
Comparison of pbeam/gnumi for horn 1 moved 3mm
Comparison of pbeam/gnumi for horn 2 moved 4mm
Comparison of pbeam/gnumi for horn currents of 150 and 100 kamps.
PBEAM: Effect on near and far neutrino fluxes by raising horn currents to 205 kamps
GNUMI: Effect on far neutrino flux by raising horn currents to 205 kamps
How Changes in Beamline Affect Near Flux, and Far/Near Ratio
(Plots shown at Neutrino Beam Simulation Workshop, August 24)

Plots showing near and double ratio sensitivity (smeared and unsmeared) to various "off" scenarios in beamline: here
Physics Sensitivities to 180 kamp horn
Muons from Faux Medium Energy Beam
Very Preliminary! Output from Pbeam: muons for "faux" medium energy beam where the target is only moved back by 1m, horns stay in same position.
See here for plots
Muons from Faux Medium Energy Beam Fed through GEANT
Still pretty preliminary...muons from pbeam fed into gnumi. Comparisons between nominal and 1m back location, for a 3mm shift in horn 1.
See here for plots
September 14 Meeting:
Newest pbeam/gnumi comparison for moving horn 2 by 4mm:
with air in the chase and material in the upstream decay pipe window here
target shifts (0,1,2m!) for muon monitors here
comparison between "tertiary" muons in gnumi (black crosses, big errors) with pbeam-generated muons (red crosses) here
September 24 Meeting:
Update from last meeting: target shifts for muon monitors here (tg01comp.ps): now with the correct amount of shielding between all the different alcoves. Punch line: with the target moved 1m back from nominal you get 5-10% asymmetries in alcove 0, and 5% asymmetries in alcove 2 for a 3mm shift in horn 1. For the target moved back 2m, you see as much as 15% asymmetries in both alcoves 0 and 1.
What happens to the neutrino fluxes when you move the target back from the nominal position by 0, 1, or 2 m? Now what happens to the ratio of ratios and the near detector spectrum when you move horn 1 by 3mm or horn 2 by 4mm? It's all here (nus_tgt012_h2.ps) in this file.
Comparisons of different horn and target positions can be found here (hornzpos.ps) : The punch line is that for the "medium" energy beam, moving the target back by 1.3m gives you about 4/5 the events you got by originally moving the target back by 1m and moving the horns by 13m. If you only move the target back by 1m and don't change the horns, you get about 2/3 the flux, with a lower peak energy.
For the high energy beam, you could get about 85% of the events just by moving the target back 4m and the horns to the medium energy position. Or, you could get about 70% of the events by just moving the target back 4m and keeping the horns in the low energy configuration.
October 3 Meeting:
PBEAM muons and horn shifts: imagine that muons can travel through everything (like neutrinos can): what information is really at the downstream end of the decay pipe? here (centering.ps): This shows the muon fluxes for bands in x and y, for different target positions, and also for a 0 horn current run. (This does not include any muons from uninteracted protons going through the beampipe, which contribute something like 5% of the muons in the low energy configuration).
here (centering_short.ps): shows the same muon distributions but for a 300m decay tunnel, not a 675m decay tunnel, just for the heck of it.
PBEAM neutrinos and horn shifts: This link (horns_chi2.ps) Shows the ratio of near spectra and associated statistical error for 80 ton-days (assuming 3.7e20 per year, 365 days per year), for moving the horn by 1,2, and 3mm, for the nominal beam as well as the one made from the target being 1 or 2m upstream of nominal. The difference in chi2 for the three configurations (as a function of horn displacement) is shown for each case, with the fit to the fucntion chi2=Ax^2, where x is in mm. The three constants for the three target locations are: 9,62,126. Considering gross alignment problems:
1: What if the proton beam is not aligned properly with the beamline defined by the 2 horns and the decay tunnel? (For this plot the proton angle is off by 1mrad, but it still hits the center of the target, which is properly aligned with the rest of the horn system.) See here (proton_angle_x.ps)
2: What if the horns are aligned to eachother, but are at an angle with respect to the proton beam? (and are also at an angle with respect to rest of the beamline) again, assume a 1mrad offset, but the narrowest part of the horn is not offset. See here (angles.ps)
3: The Chase is surveyed from the most downstream point: See here (angle2.ps)
Beam Pointing with Neutrinos:
This plot
shows the x (as in horizontal) distributions of neutrinos at the near detector for various beam configurations: nominal, target back 1,2,3,3.6m from the nominal. The x distributions are shown for the "peak events" and the "high energy tail events (up to 50GeV)" separately. The division between peak and high energy occurs at 5,10,12.5,17.5, and 20GeV for the 5 target positions listed above. The statistics on the plots assume 4 weeks of running with 5e12 protons on target per spill (or 1 week of running at "realistic" intensity), with the standard density of the near detector.

The first page has x distributions as well as a fit to a constant plus a parabola. The function is P1*(1-p2*(x-p3)**2). The second page shows P2 (the depletion at 1m compared to the peak) as a function of target position. Note that for the target 2m away from the nominal position the p2 parameter is barely 2 or 2.5 sigma away from 0. (with no P2 information you get no knowlege of the mean of the distribution). With the target 3 and 3.6m away you get a very good measurement of the mean of the neutrino x distribution (5cm) but also you get a measurement of the width of the distribution (to about 10-20% of itself) which can be used to constrain the monte carlo description of the beam.
What happens if the target is shorter?
If the first 10cm fall off
If the last 10cm fall off
Either way, this shows up in both the muon and the hadron monitors: the muon monitors see changes consistent with the neutrino flux changes shown in the plots, and the hadron monitors would see a larger flux of protons in the middle, since less of them are getting absorbed by the target now.
Plots from Previous Meetings:
Slides shown at may 1 meeting (Before hose bug found)
Slides shown at may 7 meeting (Before lots of bugs found, but with no hose)
Deborah Harris
Last modified: Fri Dec 14 15:31:14 CST 2001