Žarko pavlović, 2 patricia vahle, 1 sacha kopp, 2 1 university college, london 2 university of...
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Žarko Pavlović,2 Patricia Vahle,1 Sacha Kopp,2 1 University College, London
2 University of Texas at Austin
Flux Uncertainties for the NuMI Beam
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).
“Medium” EnergyBeam Setting
“High” EnergyBeam Setting
“Low” EnergyBeam Setting
MINOS Data
Calculated flux
Why Hadron Production Is Important to NuMI
• Two-detector experiment for disappearance measurement.
• Agreement ‘OK’ in ND, within model spread.
• But what should we use as error in predicted beam spectrum? (model correlation?)
Non-hadron production systematic
• Non-hadron production systematics affect the falling edge of the peak the most
• Far/near uncertainty < 2% Focusing Peak
Focusing Peak
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
MARS–v.14
MARS–v.15
LE10/185kA BeamLE10/185kA Beam
Data Upon Which Models are Based
Atherton400 GeV/c p-Be
Barton100 GeV/c p-C
SPY450 GeV/c p-Be
• 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.
Thick-Target Effects
• Hadron production data largely from ‘thin’ targets.
• Particles are created from reinteractions in NuMI target.
• Approx 30% of yield at NuMI p0=120 GeV/c
Min
iBoo
NE
NuMI
CNGS
J-PARC
Fluka 2005
NuMI Variable energy beam“Low”Energy
protonHorn 1
Horn 2
target
“High”Energy
target
Horn 1Horn 2
with pT=300 MeV/c
and
p=5 GeV/cp=10 GeV/cp=20 GeV/c
NuMI Beam MC
NuMI Beam MC
NuMI Beam Configurations
• We can vary– Horn current (pT kick supplied to pions)– Target Position (xF of focused particles)
LE010/185kALE010/0kA LE010/170kA
LE010/200kA LE100/200kA LE250/200kA
Parameterizing Hadron Production
• Used empirical form similar to BMPT to parameterize Fluka2005:
2/3)(2
)()( TF pxCTFF
TF
epxBxAdpdx
Nd
• Fit was to a MC of our thick-target yield estimated by Fluka2005.
• Tune parameters of the fit to match ND data.
(xF,pT) weights
• Result of the fit is set of weights in (xF,pT) plane that should be applied to /K yields
• Data prefers more low pT pi’s
05
2
2
/
/
FlukaTF
tunedTF
dpdxNd
dpdxNdweight
weights
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 2 to ND was same with/without, so this just shows that different parameterizations give equivalent fits.
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
LE10/185kA
Results (Including >30 GeV)
Reconstructed Energy (GeV)
Dat
a/M
CE
vent
s/bi
n
20 40 60 800
(other beams fit simultaneously)
(ovflw)
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 E)
• 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 ’s at MiniBooNE can give us insight into /K yields.
Hadron Production
• Each (xF,pT) bin contributes with different weight in each beam configuration
LE010/185kA
LE100/200kA
LE250/200kA
LE010/185kA
LE100/200kA
LE250/200kA
LE010/185kA LE100/200kA LE250/200kA
1 2
1
2
1
2
1
2
Results
LE010/185kA
Reconstructed Energy (GeV)
Dat
a/M
CE
vent
s/G
eV
20 40 600
Fluka2005Tuned Had. Prod.
(ovflw)