n Flux Uncertainties for the NuMI Beam

1
n Flux Uncertainties for the NuMI Beam
Žarko Pavlovic,2 Patricia Vahle,1 Sacha Kopp,2 1
University College, London 2 University of Texas
at Austin
2
How Good is our Beam MC?

• Beam flux starting with Fluka2005 model of
  particle yield off target.
• NuMI has run several beam energy configurations
  (more on this later)
• Error bars are from the beam systematic errors
  (dominated by hadron production uncertainty, but
  all effects are included).

High Energy Beam Setting
Medium Energy Beam Setting
Low Energy Beam Setting
MINOS Data
Calculated n flux
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Why Hadron Production Is Important to NuMI

• Two-detector experiment for nm disappearance
  measurement.
• Agreement OK in ND, within model spread.
• But what should we use as error in predicted beam
  spectrum? (model correlation?)

4
Non-hadron production systematic

• Non-hadron production systematics affect the
  falling edge of the peak the most
• Far/near uncertainty lt 2

Focusing Peak
Focusing Peak
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Compare Hadron Production Models
Model ?pT? (GeV/c)
GFLUKA 0.37
Sanf.-Wang 0.42
CKP 0.44
Malensek 0.50
MARS v.14 0.38
MARS v.15 0.39
Fluka 2001 0.43
Fluka 2005 0.36
Fluka2001
Fluka2005
MARSv.14
MARSv.15
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Data Upon Which Models are Based
Atherton 400 GeV/c p-Be Barton 100 GeV/c
p-C SPY 450 GeV/c p-Be
LE10/185kA Beam

• Available input data is sparse for high energy
  protons
• Now there is extensive data available from NA49
  (not true at time of NuMI/MINOS analysis),
  eventually also FNAL/E907.

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Thick-Target Effects

• Hadron production data largely from thin
  targets.
• Particles are created from reinteractions in NuMI
  target.
• Approx 30 of yield at NuMI p0120 GeV/c

J-PARC
MiniBooNE
CNGS
Fluka 2005
NuMI
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NuMI Variable energy beam
p with pT300 MeV/c and
p5 GeV/c p10 GeV/c p20 GeV/c
Low Energy
High Energy
target
target
proton
Horn 1
Horn 1
Horn 2
Horn 2
NuMI Beam MC
NuMI Beam MC
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NuMI Beam Configurations
LE010/185kA
LE010/170kA
LE010/0kA
LE100/200kA
LE250/200kA
LE010/200kA

• We can vary
• Horn current (pT kick supplied to pions)
• Target Position (xF of focused particles)

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Parameterizing Hadron Production

• Used empirical form similar to BMPT to
  parameterize Fluka2005

• Fit was to a MC of our thick-target yield
  estimated by Fluka2005.
• Tune parameters of the fit to match ND data.

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ND Spectra After Reweighting (I)
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ND Spectra After Reweighting (II)
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ND Spectra After Reweighting (III)
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ND Spectra After Reweighting (IV)
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ND Spectra After Reweighting (V)
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ND Spectra After Reweighting (VI)
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(xF,pT) weights
p weights

• Result of the fit is set of weights in (xF,pT)
  plane that should be applied to p/K yields
• Data prefers more low pT pis

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Are fitted xF and pT reasonable?
Model ?pT? (GeV/c)
GFLUKA 0.37
Sanf.-Wang 0.42
CKP 0.44
Malensek 0.50
MARS v.14 0.38
MARS v.15 0.39
Fluka 2001 0.43
Fluka 2005 0.36
Our Fluka2005 (reweighted) 0.36

• We also tried doing a fit without ?pT?
  constraint.
• Fitted c2 to ND was same with/without, so this
  just shows that different parameterizations give
  equivalent fits.

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Final Result

• F/N ratio unchanged by this procedure in
  focusing peak (expected).
• Changes in high energy tail 10, but stable to 2

(Fluka2005)
Focusing Peak
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Kaons in NuMI
HE
ME
LE10
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Results (Including gt30 GeV)
LE10/185kA
Events/bin
(other beams fit simultaneously)
(ovflw)
Data/MC
40
60
80
20
0
Reconstructed Energy (GeV)
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Conclusions

• Dead-reckoned flux using Fluka2005 particle
  yields off our target gave reasonably good
  agreement with data in MINOS Near Detector
• ? (10-30 discrepencies, depending on
  En)
• We had concerns about correlations between hadron
  production models, our inability to determine a
  flux uncertainty other than to quote model
  spread.
• Flexible beam configurations of NuMI permitted
  tuning hadron production yields to match the ND
  data ? reduce dependence on input models.
• Flux uncertainty at far detector reduced (2-10)
  ? (1-4)
• NuMI ns at MiniBooNE can give us insight into
  p/K yields.

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Backup slides
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Hadron Production
LE010/185kA
LE100/200kA
LE250/200kA
1
1
1
2
2
2

• Each (xF,pT) bin contributes with different
  weight in each beam configuration

1
2
25
Some slices in xF-pT plane
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nm Results
Fluka2005 Tuned Had. Prod.
Events/GeV
LE010/185kA
(ovflw)
Data/MC
40
60
20
0
Reconstructed Energy (GeV)
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Calibration of NuMI Flux Using MiniBooNE
MiniBooNE
q
p, K
p beam
Decay Pipe

• NuMI ns sprayed in all directions.
• K?mn and p?mn decays at off-axis angle

110mrad to MiniBooNE

• Opportunity to check the p/K ratio of yields off
  the target.