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.

ND Spectra After Reweighting (I)

ND Spectra After Reweighting (II)

ND Spectra After Reweighting (III)

ND Spectra After Reweighting (IV)

ND Spectra After Reweighting (V)

ND Spectra After Reweighting (VI)

(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

Kaons in NuMI

LE10

ME

HE

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.

Backup slides

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

Some slices in xF-pT plane

Results

LE010/185kA

Reconstructed Energy (GeV)

Dat

a/M

CE

vent

s/G

eV

20 40 600

Fluka2005Tuned Had. Prod.

(ovflw)

Calibration of NuMI Flux Using MiniBooNE

• NuMI ’s sprayed in all directions.

• K and decays at off-axis angle:

p beam , K

22

,

2

2,

2

1

1

K

K

EM

m

E

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

~110mrad to MiniBooNE