Download - MiniBooNE

MiniBooNEMiniBooNE

• MiniBooNE Motivation• LSND Signal

• Interpreting the LSND Signal

• MiniBooNE Overview• Experimental Setup

• Neutrino Events in the Detector

• The Oscillation Search

• Studying MiniBooNE Hadron Production at HARP• The HARP Data Set

• HARP Analysis

Outline

Vth Rencontres du Vietnam 2004David Schmitz

Columbia University

Vth Rencontres du Vietnam – 07 August, 2004 David Schmitz – Columbia University 2

MiniBooNE Motivation : The LSND Result• The Liquid Scintillator Neutrino Detector was the first accelerator based neutrino oscillation experiment to see a signal.

• LSND saw a 3.8 excess (above expected background) of e in a beam.

)%045.0067.0264.0()(Prob e

• The KARMEN experiment was a similar experiment that saw no signal neutrinos. KARMEN had less statistics and a slightly different experimental L/E.

•A combined analysis of LSND and KARMEN leaves a substantial allowed region.

combined analysis allowed region


MiniBooNE Motivation : Interpreting the LSND Signal

m13

m12

m23

m13

m12

m23

• What to make of 3 independent m2 values?• solar exp. (Super-K, K, SNO, KamLAND, …)

m2 ~ 10-5 eV2

• atmospheric exp. (Super-K, K, …) m2 ~ 10-3 eV2

• accelerator exp. (LSND) m2 ~ 1 eV2




m2 ~ 10-5 eV2



m13

m12

m23

• One of the experimental results is incorrect. Must verify each m2.

• atmospheric and solar results are well confirmed.

• accelerator and reactor based exp. in the atmo. and solar ranges (K2K, MINOS, KamLAND)

• LSND requires confirmation.

m13

m12

m23



m13

m12

m23

m13

m12

m23


m2 ~ 10-5 eV2



• Addition of 1 or more “Sterile” neutrinos to the 3 neutrino standard model.

• LSND could be explained by oscillations to sterile neutrinos.








m2 ~ 10-5 eV2



• Other possibilities• CPT violation

• CP violation + sterile neutrinos

• others…

?










m2 ~ 10-5 eV2



• Other possibilities• CPT violation

• CP violation + sterile neutrinos

• others…







The LSND signal must be confirmed or ruled out to know how to proceed in the neutrino sector.


MiniBooNE Overview : Experimental Setup

• MiniBooNE receives 8.9 GeV/c protons from the Fermilab Booster.

• Protons are focused onto a 1.7 interaction length beryllium target producing various secondaries (p’s, ’s, K’s).

• Secondaries are focused via a magnetic focusing horn surrounding the target. The horn receives 170 kA pulses at up to 10 Hz.

Decay region

25 m50 m 450 m



• Secondary mesons (’s, K’s) decay in the 50m decay region to produce the MiniBooNE neutrino beam.

• A removable 25m absorber can be inserted. A great advantage for studying backgrounds.

• The horn is capable of running with the polarity reversed…anti-neutrino mode.

Decay region

25 m50 m 450 m

e

0

0

0

0

K

eK

eK

K

K

e

e

e

( )

( )



• Neutrinos are detected ~500 m away in a 12 m diameter Čerenkov detector.

• 950,000 liters of mineral oil

• 1280 photomultiplier tubes

• 240 optically isolated veto tubes

Decay region

25 m50 m 450 m


MiniBooNE Overview : Neutrinos in the Detector

• We look for remnants of CC events in the detector producing a ring of prompt Čerenkov light and a small amount of delayed scintillation light.

epne

0

l

pZ 0

• NC 0 events are characterized by the double rings produced by 0 . These events can look like electron events when the photons overlap or the decay is asymmetric.

pn


MiniBooNE Overview : More About CCQE Events

• Reconstruct the lepton angle with respect to the beam direction.

• Measure visible energy from Čerenkov light and small amount of scintillation light.

• ~10% E resolution at 1GeV with no background


MiniBooNE Overview : More About CCQE Events

ell

llQE

PEMmMEE

cos2

21 2

CCQE Event Reconstruction

• Reconstruct the lepton angle with respect to the beam direction.

• Measure visible energy from Čerenkov light and small amount of scintillation light.

• ~10% E resolution at 1GeV with no background

PRELIMINARY PRELIMINARY PRELIMINARY


MiniBooNE Overview : eOscillation Sensitivity

• Recall that the MiniBooNE e appearance analysis is a blind analysis.

• eCCQE events suffer from larger backgrounds than events.

• Use measurements both internal and external to constrain background rates.






• With 1x1021 protons on target

• Average ~5% uncertainty on background rates.


m2 = 0.4 eV2

m2 = 1 eV2

MiniBooNE Overview : eOscillation Signal

SignalMis IDIntrinsic e


MiniBooNE Beam : Hadron Production at HARP

• The first goal is to measure + production cross sections for Be at pproton = 8.9 GeV/c.

• Additional measurements include:• - production (important for running)

• K production (important for intrinsic e backgrounds)

MiniBooNE has cooperated with the HARP experiment (PS-214) at CERN to measure hadron production from the MiniBooNE beryllium target.

No target 1.1 M events Normalization

5% Be 7.3 M events p+Be x-section

50% MB replica 5.4 M events Effects specific to MB target

reinteraction absorptionscattering100% MB replica 6.4 M events


MiniBooNE Beam : Beryllium Target• The MB target is ~71 cm long and 1 cm in diameter

• Cooling fins (also Be)

• Comprised of seven ~10 cm slugs


HARP : Cross Section Measurement

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i NM 111

truep ),( recp ),( pion purity

pion yieldtracking efficiency

migration matrixacceptance

pion efficiency



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pion efficiency

• Acceptance is determined using the MC (compare to MB requirements)



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jijtrack

iacci

i NM 111




pion efficiency


• Tracking Efficiency and Migration (no time to discuss today).



jj

jijtrack

iacci

i NM 111




pion efficiency


• Tracking Efficiency and Migration (no time to discuss today).

• Raw Particle Yields and Efficiency and Purity of the selection.


MiniBooNE Beam : Relevant Phase SpaceMomentum distribution peaks at ~1.5 GeV/c and trails off at 6 GeV/c.

Angular distribution of pions is mostly below 200 mrad.

Momentum and Angular distribution of pions decaying to a neutrino that passes through the MB detector.

Acceptance of HARP forward detector

Acceptance in P for |y|<50 mrad & |x|<200 mrad

Acceptance in x for |y|<50 mrad & P > 1 GeV


HARP Detector : Overlapping PID Detectors0 1 2 3 4 5 6 7 8 9 10

pP (GeV)

ek

TOFCERENKOV

TOF ?CERENKOV

CERENKOVCALORIMETER

TOF

CERENKOV

CAL



pP (GeV)

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Bayes Theorem


HARP Detector : Overlapping PID Detectors

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0 1 2 3 4 5 6 7 8 9 10

pP (GeV)

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TOFCERENKOV

TOF ?CERENKOV

CERENKOVCALORIMETER

TOF

CERENKOV

CAL


Pion ID : Beam Particles• Use no target runs to determine correction factor for PID. Beam detector ID is considered “true” ID.

• PID Input (for 1st iteration) is found from crude cuts on detector data. But method is quite insensitive to starting input.

• Need MC to determine efficiency and purity for continuous p,

PRELIMINARY PRELIMINARY PRELIMINARY

jj

j 1


Pion ID : Beryllium 5% Target

• Run iterative PID algorithm on Be 5% target data to extract raw pion yields.

• PID efficiency and purity determined using no target data (MC).

• Tracking efficiency determined using both data and MC.

• Acceptance determined from the MC.

PRELIMINARY PRELIMINARY


Next Steps• Continue to improve particle probability functions for the three detectors using data and MC.

• Implement tracking, PID, and acceptance corrections to raw particle yields.

• Move towards normalized pion cross section measurement.

Next Next Steps• Study pion absorption and reinteraction effects in the thick target by

using data from three different target lengths.

• How well can we do /K separation?

• Finally, generate neutrino fluxes for MiniBooNE using measurements from HARP.