Jonathan Link Columbia University Fermilab Wine & Cheese November 18 th 2005

Jonathan LinkJonathan Link

Columbia UniversityColumbia University

Fermilab Wine & CheeseFermilab Wine & CheeseNovember 18November 18thth 2005 2005

Meson Production Results from Meson Production Results from E910 and Their Relevance to E910 and Their Relevance to

MiniBooNEMiniBooNE

E910E910

MiniBooNEMiniBooNE

Talk OutlineTalk Outline

1.1. Motivation:Motivation:

• What MiniBooNE needsWhat MiniBooNE needs

• What’s been done in the pastWhat’s been done in the past

2.2. Brookhaven E910 Brookhaven E910

• About the experimentAbout the experiment

• Pion production analysisPion production analysis

• KK00 production analysis production analysis

3.3. Pulling things together for MiniBooNEPulling things together for MiniBooNE

• Now add HARPNow add HARP

What MiniBooNE NeedsWhat MiniBooNE Needs

MiniBooNE’s primary objective is to observe a small MiniBooNE’s primary objective is to observe a small excess of excess of ννee interactions in a beam composed mostly of interactions in a beam composed mostly of ννμμ..

What do I mean by “composed mostly of What do I mean by “composed mostly of ννμμ??

e?

The MiniBooNE Neutrino BeamThe MiniBooNE Neutrino Beam

Start with an intense 8 GeV proton beam from the Booster Start with an intense 8 GeV proton beam from the Booster incident on a beryllium target.incident on a beryllium target.

In the Be target mostly pions are produced, but also some kaons.In the Be target mostly pions are produced, but also some kaons.

Charged pions decay almost exclusively as Charged pions decay almost exclusively as ++++..

KK++ee++ee, , KKLL±±eee e and and ++ee++eeννμμ contribute contribute ee’s. ’s.

This directly related to the This directly related to the observed observed ννμμ’s’s

These must be understood using a These must be understood using a combination of external production combination of external production data and evidence in our own data.data and evidence in our own data.


At a minimum we need to understand the relative At a minimum we need to understand the relative ννee to to ννμμ

flux, as a function of energy, at the detector, prior to any flux, as a function of energy, at the detector, prior to any oscillations. This requires accurate oscillations. This requires accurate

• Primary production models for Primary production models for ππ±±, K, K++ and K and KLL by protons by protons

in the target Be at 8.9 GeV/c.in the target Be at 8.9 GeV/c.


Experiment Pbeam (GeV/c) Year

Allaby 19.1 1970Cho 12.4 1971Marmer 12.3 1969Vorontsov 10.1 1983


Abbott 14.6 1992Aleshin 9.5 1977Allaby 19.1 1970Dekkers 18.8, 23.1 1964Eichten 24.0 1972Lundy 13.4 1965Marmer 12.3 1968Piroue 2.74 1966Vorontsov 10.1 1983

Pre-existing Production DataPre-existing Production Data

ππ Production Production KK++ Production Production


Abe 12 1987

KK00 Production Production

E910 and HARP

HARP only

Initially E910 only New Preliminary New Preliminary

Results in this talkResults in this talk


At a minimum we need to understand the relative At a minimum we need to understand the relative ννee to to ννμμ

flux, as a function of energy, at the detector, prior to any flux, as a function of energy, at the detector, prior to any oscillations. This requires accurate oscillations. This requires accurate

• Primary production models for Primary production models for ππ±±, K, K++ and K and KLL by protons by protons

in the target Be at 8.9 GeV/c.in the target Be at 8.9 GeV/c.

• Secondary interaction models (absorption, secondary Secondary interaction models (absorption, secondary production, etc.) in the target and surrounding materials.production, etc.) in the target and surrounding materials.

• Descriptions of the beam line, target, horn field, and Descriptions of the beam line, target, horn field, and decay volume.decay volume.


Initial Look at Monte Carlo ToolsInitial Look at Monte Carlo Tools

Let’s take a look at some neutrino flux determinations from the past…

Running with a sample of Running with a sample of common monte carlo tools common monte carlo tools results in a wide range of results in a wide range of neutrino fluxes.neutrino fluxes.

Both normalization and Both normalization and energy distribution vary.energy distribution vary.

Maybe they did better at Maybe they did better at predicting predicting νν flux flux back when back when 8 GeV was closer to the high 8 GeV was closer to the high energy frontier?energy frontier?

Only the primary production (p+Be→X) is different!

Study by Dave Schmitz

They didn’t even try to determine their ν flux from pion production and beam dynamics.

In subsequent cross section analyses the theoretical (“known”) quas-ielastic cross section and observed quasi-elastic events were used to determine the flux.

Brookhaven

AGS

7ft D2 B

ubble Cham

ber

Fermila

b

15ft D2 B

ubble Cham

ber

Again, they use QE events and theoretical cross section to calculate the ν.

When they try to get the flux from meson (π and K) production and decay kinematics they fail miserably for Eν<30 GeV.

The Procedure

•Pion production cross sections in some low momentum bins are scaled up by 18 to 79%.

• The K+ to π+ ratio is increased by 25%.

• Overall neutrino (anti-neutrino) flux is increased by 10% (30%).

All driven by the neutrino events observed in the detector!

Brookhaven

AGS

Liquid Scintill

ator

Argonne ZGS

12ft D2 B

ubble Cham

ber

Flux derived from pion production data. Were able to test assumptions about the form of the cross section using absolute rate and shape information.

• Pion production measured in ZGS beams were used in this analysis

• A very careful job was done to normalize the beam.

• Yet they have a 25% inconsistency between the axial mass they measure considering only rate information verses considering only spectral information.

Interpretation: Their normalization is wrong.

So What Have We Learned…So What Have We Learned…

1.1. Predicting a neutrino flux from meson production data Predicting a neutrino flux from meson production data and decay kinematics is difficult. Most groups didn’t and decay kinematics is difficult. Most groups didn’t even try, and those that did often failed.even try, and those that did often failed.

2.2. If all of the low energy neutrino cross sections are If all of the low energy neutrino cross sections are measured with respect to the quasi-elastic cross section, measured with respect to the quasi-elastic cross section, how is the quasi-elastic cross section measured? how is the quasi-elastic cross section measured?

So What Have We Learned…So What Have We Learned…

1.1. Predicting a neutrino flux from meson production data Predicting a neutrino flux from meson production data and decay kinematics is difficult. Most groups didn’t and decay kinematics is difficult. Most groups didn’t even try, and those that did often failed.even try, and those that did often failed.

2.2. If all of the low energy neutrino cross sections are If all of the low energy neutrino cross sections are measured with respect to the quasi-elastic cross section, measured with respect to the quasi-elastic cross section, how is the quasi-elastic cross section measured? how is the quasi-elastic cross section measured?

MiniBooNE has access to two modern production data MiniBooNE has access to two modern production data sets. One of these data sets (HARP) includes thick target sets. One of these data sets (HARP) includes thick target data which will help us construct the secondary interaction data which will help us construct the secondary interaction model. model.

The other data set comes from the E910 Experiment…The other data set comes from the E910 Experiment…

Brookhaven Experiment 910Brookhaven Experiment 910E910 used a spectrometer with good acceptance and particle ID over the momentum and angular range of interest to MiniBooNE.

Particle ID from dE/dx in the TPC, threshold Čerenkov, and Time of Flight.

The E910 CollaborationThe E910 Collaboration

Used a tagged proton beam which was operated at momenta of Used a tagged proton beam which was operated at momenta of 17.5, 12.3 and 6.4 GeV/c on targets of Au, Cu, Pb, U and Be17.5, 12.3 and 6.4 GeV/c on targets of Au, Cu, Pb, U and Be..

Their main objective was to study nuclear processes relevant to Their main objective was to study nuclear processes relevant to the relativistic heavy ion collisions.the relativistic heavy ion collisions.

At the end of their run they took a short set of runs with a low At the end of their run they took a short set of runs with a low bias trigger that is well suited for cross section measurements.bias trigger that is well suited for cross section measurements.

Brookhaven Experiment 910Brookhaven Experiment 910

Antiproton production in p+A collisions at 12.3 and 17.5 GeV/c (Phys.Rev.C64:064908)

Semi-inclusive Λ0 and KS production in p-Au collisions at 17.5 GeV/c

(Phys.Rev.Lett.85:4868)

Measuring centrality with slow protons in proton-nucleus collisions at 18 GeV/c (Phys. Rev. C 60, 024902)

Strange particle production and an H-dibaryon search in p+A collisions at the AGS (Nucl.Phys.A639:407-416)

Pion Production in E910Pion Production in E910

This paper focused on pions with momentum less that 1.2 GeV/c.

The preliminary analysis in this talk extends the pion momentum range beyond 1.2 GeV/c and includes a small data set with beam momentum at 6.4 GeV/c.

cosθ

Inclusive soft pion production from 12.3 and 17.5 GeV/c protons on Be, Cu, and Au (Phys.Rev.C65:024904)

Expression for a Cross SectionExpression for a Cross Section

a

w

protonsN

N

dpd

d

)(

)(

N

A

A

2The The ππ++ cross section is given by: cross section is given by:

Where Where AA is the mass (9.01 GeV/c is the mass (9.01 GeV/c22 for Be) for Be)

NNAA is Avagadro’s number is Avagadro’s number

ρρ is the target area density (3.4 g/cm is the target area density (3.4 g/cm22))

a a is the acceptance and cut efficiencyis the acceptance and cut efficiency

εε is the trigger efficiency andis the trigger efficiency and

ww is the reciprocal of the bin area in GeV/c and is the reciprocal of the bin area in GeV/c and steradianssteradians

Acceptance and Cut EfficiencyAcceptance and Cut EfficiencyMMonte Carlo events are used to calculate the acceptance of the onte Carlo events are used to calculate the acceptance of the spectrometer and the efficiency of the analysis cuts.spectrometer and the efficiency of the analysis cuts.

The efficiency or acceptance The efficiency or acceptance is given by:is given by:

The Error on The Error on aa is binomial: is binomial:

1)(N

)(1σ

gen

aa

a

gen

pass

N

Na

TPC

TOFpp

θθ

Eff

icie

ncy

Eff

icie

ncy

E910 ran for a brief period of time with a low bias trigger. E910 ran for a brief period of time with a low bias trigger. This trigger required that there be a beam particle upstream of This trigger required that there be a beam particle upstream of the target, but not downstream.the target, but not downstream.

The TriggerThe Trigger

Dataset Beam Protons Trigger Efficiency (ε)

6.4 GeV/c 93,632 1.000±0.01

12.3 GeV/c 745,216 0.968±0.006

17.6 GeV/c 2,576,352 0.896±0.006

This trigger should fire on all interacting protons and will have This trigger should fire on all interacting protons and will have a small inefficiency that grows with the secondary multiplicity.a small inefficiency that grows with the secondary multiplicity.

Trigger efficiency (Trigger efficiency (εε)) is measured on a totally unbiased, highly is measured on a totally unbiased, highly pre-scaled, beam proton trigger.pre-scaled, beam proton trigger.

Bullseye Trigger (Low Bias)Bullseye Trigger (Low Bias)

Non-interacting beam Non-interacting beam particles will pass particles will pass through the bullseye veto through the bullseye veto region, but most other region, but most other tracks will not.tracks will not.

E910 ran for a brief period of time with a low bias trigger. E910 ran for a brief period of time with a low bias trigger. This trigger required that there be a beam particle upstream of This trigger required that there be a beam particle upstream of the target, but not downstream.the target, but not downstream.

The TriggerThe Trigger

Dataset Beam Protons Trigger Efficiency (ε)

6.4 GeV/c 93,632 1.000±0.01

12.3 GeV/c 745,216 0.968±0.006

17.6 GeV/c 2,576,352 0.896±0.006

This trigger should fire on all interacting protons and will have This trigger should fire on all interacting protons and will have a small inefficiency that grows with the secondary multiplicity.a small inefficiency that grows with the secondary multiplicity.

Trigger efficiency (Trigger efficiency (εε)) is measured on a totally unbiased, highly is measured on a totally unbiased, highly pre-scaled, beam proton trigger.pre-scaled, beam proton trigger.

ππ++ Track Selection Track Selection

• Tracks must be in the geometrical Tracks must be in the geometrical acceptance of the relevant particle ID acceptance of the relevant particle ID system (TPC for system (TPC for pp<1.2 and TOF for <1.2 and TOF for pp>1.2)>1.2)

• Tracks must point back to the Tracks must point back to the interaction vertex.interaction vertex.

• The vertex must be consistent with The vertex must be consistent with originating from the target.originating from the target.

• Tracks above Tracks above ππ Čerenkov threshold Čerenkov threshold (~2.8 GeV/c) must have a consistent (~2.8 GeV/c) must have a consistent pion hypothesis.pion hypothesis.

1.83 1.83 cmcm

Track BinningTrack Binning

θθ is divided into 6 bins from 0º is divided into 6 bins from 0º to 20.6º (or 0 to 360 mr)to 20.6º (or 0 to 360 mr)

And And pp is divided into 13 bins is divided into 13 bins from 0.4 to 5.6 GeV/cfrom 0.4 to 5.6 GeV/c

Each bin is weighted by the Each bin is weighted by the inverse of the bin area in inverse of the bin area in GeV/c and steradiansGeV/c and steradians

Selected tracks are binned in zenith angle (Selected tracks are binned in zenith angle (θθ) and total ) and total momentum (momentum (pp))

pw

θcosπ2

1

Particle IdentificationParticle Identification

Used below Used below 1.2 GeV/c1.2 GeV/c

ppKK

ππ

pp

KK

ππ

Log dE/dx vs. Momentum

Good below Good below 5.4 GeV/c 5.4 GeV/c

1/β vs. Momentum

TPC dE/dxTPC dE/dx Time of Flight Time of Flight

ππ Čerenkov Čerenkov thresholdthreshold

Particle Identification and Yield Particle Identification and Yield

Residuals are formed in each PID system between each Residuals are formed in each PID system between each different particle hypothesis and the observed system response.different particle hypothesis and the observed system response.

The residuals are constructed such that the correct hypothesis The residuals are constructed such that the correct hypothesis forms a unit Gaussian distribution centered on zero.forms a unit Gaussian distribution centered on zero.

The pion hypothesis residual in the dE/dx (p < 1.2 GeV/c) or The pion hypothesis residual in the dE/dx (p < 1.2 GeV/c) or TOF (p > 1.2 GeV/c) is plotted for each candidate trackTOF (p > 1.2 GeV/c) is plotted for each candidate track..

The pion yield in each bin is determined by fitting the residual The pion yield in each bin is determined by fitting the residual distribution, or by counting the entries between ±2distribution, or by counting the entries between ±2σσ..

Sample Residual DistributionsSample Residual Distributions

Last dE/dx

bin

First TOF bin

Just before Čerenkov

Just after Čerenkov

Last momentum

bin

2nd to last momentum

bin

Error StudiesError Studies

Several possible sources of systematic error were studied Several possible sources of systematic error were studied including:including:

• Bin to bin event migrationBin to bin event migration

• Bin specific trigger inefficiencyBin specific trigger inefficiency

• Particle ID systematics (by lifting PID cuts on Particle ID systematics (by lifting PID cuts on ππ--))

• Comparison of yield extraction methods.Comparison of yield extraction methods.

There is an overall normalization uncertainty from the target There is an overall normalization uncertainty from the target thickness (2%) and from the trigger efficiency error.thickness (2%) and from the trigger efficiency error.

The preliminary differential cross sections results with full The preliminary differential cross sections results with full errors follow…errors follow…

ππ++ ππ--

6.4 GeV/c Beam Momentum6.4 GeV/c Beam Momentum

The Pion Production Cross Section The Pion Production Cross Section PreliminaryPreliminary

ππ++ ππ--



ππ++ ππ--



Translating Pion Production to Translating Pion Production to MinBooNE EnergiesMinBooNE Energies

8

5

4

2 cosexp1

1),,( 763

1C

BCB

C

B

CB pCpC

p

pC

p

ppCppS

The parameterization of Sanford and Wang describes meson The parameterization of Sanford and Wang describes meson production as a function of beam momentum (production as a function of beam momentum (ppBB), secondary ), secondary

momentum (momentum (pp), angle (), angle (θθ), and 8 parameters (), and 8 parameters (CC11…C…C88) )

B

hi

lo

hi

lo

p p meas

p

p

BB dpdppSp

ppdpdd

2

22

2

),,(1

),,(

This function is fit to all the data by minimizing the following This function is fit to all the data by minimizing the following χχ22

The Sanford-Wang fit to E910 data was performed by Jocelyn Monroe.

The KThe K00 Analysis Analysis

The KThe KSS analysis follows the same basic prescription as the analysis follows the same basic prescription as the

pion analysis: pion analysis:

The main difference is that the KThe main difference is that the KSS yield, N(K yield, N(KSS), is extracted ), is extracted

from the reconstructed mass distribution.from the reconstructed mass distribution.

We are concerned about KWe are concerned about KLL for backgrounds, but the K for backgrounds, but the KLL

cross section can’t be easily be directly measured.cross section can’t be easily be directly measured.

Neutral kaon are actually produced as KNeutral kaon are actually produced as K0 0 and Kand K00, but they , but they decay as Kdecay as KS S and Kand KLL..

Therefore, measuring the KTherefore, measuring the KSS cross section is equivalent to cross section is equivalent to

measuring the Kmeasuring the KLL cross section. cross section.

a

w

protonsN

KN

dpd

d s )(

)(

N

A

A

2

The KThe Kss Analysis Analysis

Begin with a vertex between a positive and negative track.Begin with a vertex between a positive and negative track.

Both tracks are required to be consistent with the pion Both tracks are required to be consistent with the pion hypothesis in all relevant PID systems.hypothesis in all relevant PID systems.

Candidates where one of the Candidates where one of the tracks is also consistent with tracks is also consistent with the proton hypothesis and the the proton hypothesis and the ppππ mass is in the mass is in the ΛΛ00 mass mass peak are rejected.peak are rejected.

The KThe KSS → → ππ++ππ-- branching branching

fraction (68.6%) is accounted fraction (68.6%) is accounted for in the acceptance.for in the acceptance.

The KThe Kss Sample Sample

12.3 GeV/c12.3 GeV/c17.6 GeV/c17.6 GeV/c

The 6.4 GeV/c data set has no visible KThe 6.4 GeV/c data set has no visible Kss mass peak. mass peak.

Yield Determined by Side Band Subtraction Yield Determined by Side Band Subtraction

Subtract the appropriately weighted number of events in the blue regions from the red region.

What’s left in the red region is the Ks yield.

This assumes that the background is linear across the signal and side band regions.

The KThe Kss Production Cross Section Data Production Cross Section Data PreliminaryPreliminary

Here again the data are fit with the Sanford-Wang function.Here again the data are fit with the Sanford-Wang function.

Pulling Things Together for MiniBooNEPulling Things Together for MiniBooNE

While, the E910 data are at 6.4, 12.3 and 17.6 GeV/c, While, the E910 data are at 6.4, 12.3 and 17.6 GeV/c, MiniBooNE’s beam is at 8.9 GeV/c. MiniBooNE’s beam is at 8.9 GeV/c.

Momentum scaling from the Sanford-Wang fit gives us the Momentum scaling from the Sanford-Wang fit gives us the production cross sections at MiniBooNE energies.production cross sections at MiniBooNE energies.

Beyond E910, HARP has a large dedicated production data set Beyond E910, HARP has a large dedicated production data set at 8.9 GeV/c.at 8.9 GeV/c.

The HARP will provide cross sections for The HARP will provide cross sections for ππ±± and K and K++..

HARP also took data on thick beryllium targets including HARP also took data on thick beryllium targets including replica MiniBooNE target slugs.replica MiniBooNE target slugs.

We need to make a production model that reproduces what We need to make a production model that reproduces what comes out of the HARP replica target, comes out of the HARP replica target,

but HARP needs independent verification…but HARP needs independent verification…

Comparison of HARP Pion Production to E910Comparison of HARP Pion Production to E910

ππ++ ππ--

Use the Sanford-Wang Parameters from E910 to compare to HARP.Use the Sanford-Wang Parameters from E910 to compare to HARP.

PreliminaryPreliminary

If You’re Not Impressed by That Comparison…If You’re Not Impressed by That Comparison…Let’s take another look at that study comparing Monte Let’s take another look at that study comparing Monte Carlos.

The differences are dramatic in the The differences are dramatic in the ππ spectra as well! spectra as well!

But the E910 and HARP cross sections determine the correct But the E910 and HARP cross sections determine the correct model, which is very close to MARS. model, which is very close to MARS.

D. Schmitz

ConclusionsConclusions• Determining the neutrino flux is an essential component of Determining the neutrino flux is an essential component of the MiniBooNE oscillation analysis, and this starts with the MiniBooNE oscillation analysis, and this starts with obtaining reliable meson production cross sections.obtaining reliable meson production cross sections.

• The data set of E910 has been used to measure some of these The data set of E910 has been used to measure some of these cross sections.cross sections.

• I’ve shown you a new differential cross section measurement I’ve shown you a new differential cross section measurement for for ππ++ and and ππ-- production in p Be interactions at 6.4, 12.3 and production in p Be interactions at 6.4, 12.3 and 17.6 GeV/c beam momentum.17.6 GeV/c beam momentum.

• I’ve also shown you preliminary cross section measurement I’ve also shown you preliminary cross section measurement for Kfor KSS production at 12.3 and 17.6 GeV/c. production at 12.3 and 17.6 GeV/c.

• These data are fit to the Sanford-Wang parameterization and These data are fit to the Sanford-Wang parameterization and scaled to the MiniBooNE beam momentum.scaled to the MiniBooNE beam momentum.

• These data will be combined with HARP data for the final These data will be combined with HARP data for the final flux calculations.flux calculations.

Jonathan Link Columbia University Fermilab Wine & Cheese November 18 th 2005

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