1. Conventional Neutrino Beams Day 2
Deborah Harris
NuFact05 Summer Institute
Anacapri, Italy
June 12-13, 2005

2. Using Pions to make Neutrinos
Major Components:
Proton Beam
Pion Production Target
Focusing System
Decay Region
Absorber
Shielding…
Most nm’s from 2-body decays:
p+→m+nm
K+→m+nm
Most ne’s from 3-body decays:
m+→e+nenm
K+→p0e+ne
n energy is only
function of
np angle and
p energy
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

3. Questions From Yesterday
What happens to the nm event rate if you change the horn current? (0, 100kA, and 200kA shown)
At 735km
At 1km
Visible Energy (GeV)
Visible Energy (GeV)
Corrolary: What happens if you lower the horn current by 15kAmps and move the target back 10cm?
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

4. How can you measure the beam performance?
Pions+…
Neutrinos
protons
Muons+…
Primary Proton Beam Measurements
Remnant Proton Measurements
Tales from the front line: NuMI and the target leak
Muon Measurements
7o muon spectrometer (MiniBooNE)
“Range stack” Muon Monitor system (MINOS)
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

5. Neutrino Beamline Instrumentation
Proton Beam
Number of Protons on Target
Position and angle
Spot size of beam on target
Proton Losses before target
Target
Is it intact?
Temperature
Horns
Current
Absorber
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

6. Primary Beam Measurements
Knowing proton position is important: want to hit the center of the target
Knowing angle is important: if proton beam is at angle, the n beam comes out at an angle as well.
Two ways to measure proton position:
Non-interfering (use induction)
Interfering (secondary emission monitors)
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

7. Proton Position Measurements
Beam Position Monitors:
Beam pipe with two isolated plates (A and B)
When protons go through, charge is induced on both plates
Position=Gain*(A-B)/(A+B)
Benefits: does not interfere with proton beam
Deficits: can be noisy, can have worse resolution at low proton intensity, gives no shape information…
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

8. Secondary Emission Monitors
Secondary Emission: when charged particles go through metal foil, electrons can be kicked off
By applying a small electric field you can drift the electrons away from the foil (also need high vacuum for this!).
Now imagine a row of very thin foils oriented in horizontal and vertical direction
This gives not only a mean position, but also gives you the information of the shape
Benefits: shape and mean position
Deficits: putting matter in beam (but can be as low as 10-5 lint)
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

9. Tales from the front: NUMI, Dec. 4 2005
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

10. What about seeing the Protons at the end of the decay pipe?
Proton spot size at end of pipe is large: cannot just put in a new secondary position monitor
Proton rates are now very intense: can use ionization chambers, but they must be very resistant to radiation damage, and can be low gain
Question: what else makes it down to the end of the decay pipe?
Muons from pion decay
Undecayed pions
Secondary shower particles
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

11. Seeing protons at end of pipe
No target in the way
Target in the way
For most beamlines, this “hadron monitor” is really a proton monitor: it tells you about the protons and the target, but not about how well you are making neutrinos
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

12. Lesson Learned: be prepared for disasters…
Look at what is
between target and baffle by
shooting protons there!
Leaky Target at NuMI
the target has pipes around it that carry water to cool it
On March 23, discovered a leak: speculate the target surrounded by water…
Use Hadron Monitor to verify that water was there, and to check that it hasn’t reappeared since we solved the problem…
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

13. Monitors to Study n Beam (MINOS)nm p m+ m+ p+ m+ m+
Hadron Monitor: sees uninteracted protons after decay pipe
Muon Monitors: 3 different depths means three different muon
momentum spectra
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

14. Getting to Neutrino Spectrum from Muon Spectrum (MINOS)
As you get to higher muon energies, you are looking at higher pion energies…which in turn mean higher neutrino energies…
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

15. Muon Monitors in Different Energy Neutrino Beams
By looking at the rates in the three different muon detectors, can see how the energy distributions of the muons changes
Can study neutrino fluxes by moving the target and seeing how you make more high energy neutrinos the farther back you move the target
Can study fluxes by changing the horn current and see how you make more low energy neutrinos as you increaste the horn current.
Graphs courtesy S. Kopp
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

16. What else you can do with muons: Measure K/p ratio in Beam
ne’s from muon decay constrained by nm spectrum (since they are part of the same channel)
Kaons have no such constraint
Remember problem set: to get the ne /nm
Ratio you would also need to know the K/p production ratio (and focusing differences)
Any way this can be measured in the beam? Beam too hot to add Cerenkov counters to get track/track information
Decay
Maximum pt
p+→m+nm
30MeV
K+ → m+nm
236MeV
KL→ pmnm
216MeV
Think 2-body decay kinematics:
Center of Mass
Lab Frame
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

17. Example from MiniBooNE
Backgrounds from muons
that scatter in the dirt/collimator
By adding collimator and spectrometer at 7o, they will measure
p/K ratio from difference in peaks
K/KL ratio from m+ versus m-
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

18. Hadron Production Measurements
Measuring relative rates in muon monitors are a great handle on neutrino production but…
Delta-ray production means the absolute signal on the detector as a function of muon flux is very hard to predict….so these measurements can only provide relative flux information
Hadron Production Measurements: getting to an absolute flux prediction
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

19. Measuring Mesons as they leave Target
Particle Production Experiments:
HARP (at CERN) took data with
K2K, MiniBooNE targets
MIPP (at Fermilab) will take data
With MINOS target
Can take data with small samples,
But need to then model also the
Particle showering in the target…
MIPP Running now
Will take data with
NuMI/MINOS target
And also 1-2% targets
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

20. Uncertainties due to Hadron Production
MINOS example:
10-30% uncertainties in absolute rate
2-10% uncertainties in far/near comparison
Messier, Ely 2004
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

21. But haven’t people measured particle production before?
MINOS
Beam:
What is not the same:
Target Material
Proton Energy
Proton angular distribution
Target length
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

22. Measuring p angular distribution in real beamline
K2K Gas Cerenkov counter: measures angular distribution of Pions as function of momentum
Located right
after horns
Works for pions
above 2GeV
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

23. Measuring p angular distribution in real beamline
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines

24. Conventional Neutrino Beam Summary
Major Components:
Proton Beam
Production Target
Focusing System
Decay Region
Shielding
Monitoring
Ways to Understand n Flux:
Hadron Production
Proton Beam measurements
Pion Measurements
Muon Measurements
at angles vs momentum
at 0o versus shielding
12-13 June 2005
Deborah Harris, Conventional Neutrino Beamlines