HARP measurements of pion yieldHARP measurements of pion yieldfor neutrino experimentsfor neutrino experiments

Issei Kato (Kyoto University)for the HARP collaboration

Contents:1. HARP experiment

• Physics motivations• Detector status

2. First physics analysis for K2K target3. Summary

NuFact 04 @ Osaka

Introduction Introduction - motivations -- motivations -

Physics goal of HARPPhysics goal of HARPSystematic study of

hadron production– Beam momentum:

1.5 – 15 GeV/c– Target materials:

from hydrogen to lead

• Inputs for the prediction of neutrino fluxes for K2K and MiniBooNE experiments

• Inputs for the precise calculation of atmospheric neutrino flux

• Pion/Kaon yield for the design of proton driver and target system for neutrino factories and SPL-based super-beams

• Inputs for Monte Carlo generators (GEANT4, e.g. for LHC or space applications)

Analysis for K2K: motivationAnalysis for K2K: motivation

10 2 43 5E (GeV)

4

8

12x1010

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 1 2 3 4 5Neutrino Energy (GeV)

(xL

)/(

xL)

SKSK

FDFD

22

12GeV proton12GeV proton

++

pp

pion monitorpion monitor

Spectrum @ KEKSpectrum @ KEK

Far/Near spectrum ratio Far/Near spectrum ratio ≠ 1≠ 1

10 2 43 5E (GeV)

2

4

6

8x104

measured by NDmeasured by ND

w/o oscillationw/o oscillation

w/ oscillationw/ oscillation

TargetTarget

Spectrum @ SKSpectrum @ SK

>1GeV>1GeVConfirmed by PIMONConfirmed by PIMON

momentum/angular distribution neutrino enerugy spectrum (specially below 1 GeV)

++

~0.6GeV~0.6GeV

Horn MagnetHorn Magnet

Decay pipeDecay pipe Near detectorNear detector Far detectorFar detector250km250km

Region of Interest in K2KRegion of Interest in K2K

In K2K case: In K2K case: EE : 0 ~ 5 GeV : 0 ~ 5 GeV• P < 10 GeV/c• < 300 mrad

Most important regionMost important region(oscillation maximum:(oscillation maximum:

EE ~ 0.6 GeV) ~ 0.6 GeV)• 1GeV/c < P1GeV/c < P < 2 GeV/c < 2 GeV/c• < 250 mrad< 250 mrad

E P

P vs

Analysis forAnalysis for Forward RegionForward Region

Oscillation maxOscillation max

HARP ExperimentHARP Experiment

HARP CollaborationHARP Collaboration

124 physicists 24 institutes

HARP DetectorsHARP Detectors

Beam DetectorsBeam DetectorsBeam Cherenkov:

p//K separationBeam TOF:

p//K separationMWPC:

Beam direction

T9 beamLarge angle tracksLarge angle tracks(inside solenoid)TPC: Tracking & PIDRPC: PID

Forward trackingForward trackingNOMAD drift chambers:

Dipole magnet:Tracking &

Momentum analysis

Forward Particle IDForward Particle IDTOF wall:PID for 0–4.5 GeV/cCherenkov:PID for 3–15 GeV/cEM calorimeter:e/ separation

Used for Forward AnalysisForward Analysis

Detector PerformancesDetector Performances

Beam DetectorsBeam Detectors

TOF-A

CKOV-A CKOV-B

TOF-B

21.4 m

T9 beam

MWPCs

• Beam tracking with MWPCs :Beam tracking with MWPCs :– 96% tracking efficiency using 3 planes out of 4– Resolution <100m

MiniBooNE target

Beam Particle IdentificationsBeam Particle IdentificationsBeam TOF:Beam TOF:separate /K/p at low energy

over 21m flight distance– time resolution 170 ps after

TDC and ADC equalization– proton selection purity >98.7%

Beam Cherenkov:Beam Cherenkov:Identify electrons at low energy,

at high energy, K above 12 GeV– ~100% eff. in e- tagging

12.9 GeV/c (K2K) Beam

Cherenkov ADC

K

p/d

K

p

d

3.0 GeV/c beam

Forward Tracking: NDCForward Tracking: NDC

• Reused NOMAD Drift Chambers– 12 planes per chamber (in total 60 planes)– wires at 0°,±5° w.r.t. vertical

• Hit efficiency ~80% (limited by non-flammable gas mixture)

– correctly reproduced in the simulation• Alignment with

cosmics and beam muons drift distance resolution ~340 m

Plane efficiencies Side modules

Plane number

0.2

0.4

0.6

0.8

0mod1 mod2 mod3 mod4 mod5

Resolution= 340 m

TPC

NDC1 NDC2 NDC5

NDC4

NDC3

Dipole Cherenkov

TOF-wall

EM calorimeter

beam

reused from NOMAD

MCMC

datadata

No vertex constraint includedNo vertex constraint included

momentum resolutionmomentum resolution angular resolutionangular resolution

Forward tracking: resolutionForward tracking: resolution

MCMC

Forward PID: TOF WallForward PID: TOF Wall

TOF time resolution ~160 ps3 separation: /p up to 4.5 GeV/c

K/ up to 2.4 GeV/c 7 separation of /p at 3 GeV/c

3 GeV beam particles3 GeV beam particles

datadata

p

Separate Separate /p (K//p (K/) at low momenta (0–4.5 GeV/c) ) at low momenta (0–4.5 GeV/c) • 42 slabs of fast scintillator read at both ends by PMTs

1

2022

Lttpm wall

PMT

Scintillator

Forward PID: CherenkovForward PID: Cherenkov

Separate Separate /p at high momentum/p at high momentum• filled with C4F10 (n=1.0014)• Light collection: mirrors+Winston cones 38 PMTs in 2 rows

e+

+

p

p

+

Nphel

datadata

Nphel

3 GeV beam particles3 GeV beam particles 5 GeV beam particles5 GeV beam particles

datadata

Forward PID: CalorimeterForward PID: Calorimeter

Hadron/electron separationHadron/electron separation(Reused from CHORUS)• Pb/fibre: 4/1 (Spaghetti type)

– EM1: 62 modules, 4 cm thick– EM2: 80 modules, 8 cm thick

• Total 16 X0

• Energy resolution

electronselectrons

pionspions

3 GeV3 GeV

datadata

)(%23GeVEE

E EM Energy (a.u.)

Ene

rgy

EM

1/E

M2

Forward AnalysisForward Analysis- for K2K target -- for K2K target -

Forward TrackingForward Tracking

dipole magnetNDC1 NDC2

B

x

zNDC5

beam

target

Top view

11

22NDC3

NDC4

Plane segment (2D)

33

• Categorize into 3 track types depending on the nature of the matching object upstream the dipole1. Track(3D)-Track(3D)2. Track(3D)-Plane segment(2D)3. Track(3D)-Target/vertex constraint

To recover as much efficiency as possible To avoid dependencies on track density in 1st NDC module

(hadron model dependent)

Track (3D)

3

1

)()()(

)( 111

t

tj

tjt

j

tijtrack

iacci

i NM

pion efficiency(Data)

3

1

)(

t

trackti

tracki

)(

)()()(

kj

kbkgj

kjk

j N

NN

pion purity(Data)

pion yield(raw data)

tracking efficiency(Data+MC)

migration matrix(not computed yet)Acceptance (MC)

i = bin of true (p,)j = bin of recosntructed (p,)

Forward Analysis - cross section -Forward Analysis - cross section -

K2Kinterest

Forward acceptanceForward acceptance

dipoleNDC1 NDC2

B

xz

If a particle reaches the NDC module 2,the particle is accepted.

2 4 6 80

0.2

0.4

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1

P(GeV/c)

acce

ptan

ce

0.2

0.4

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1

acce

ptan

ce

-200 0 200 (mrad)

K2K interest

MCMC

MCMC

downupdowndown

recp

acc

downtrack

NN

NN

.

Downstream trackingefficiency ~98%

Up-downstream matching efficiency ~75%

Tracking efficiencyTracking efficiency

track is known at the level of 5%

Green: type 1Blue: type 2 Red: type 3

Black: sum of normalized

efficiency for each type

Total Tracking Efficiency

0 2 4 6 8 10

0.2

0.4

0.6

0.8

1.0

0.2

0.4

0.6

0.8

1.0

-200 -100 0 200100P (GeV/c) x (mrad)

Tota

l tra

ckin

g ef

ficie

ncy

Tota

l tra

ckin

g ef

ficie

ncy

Total tracking efficiency as a function of p(left) and x (right)computed using MC with 2 hadron generators properly Both hadron models compatible (except for |x| < 25 mrad)

Need more study for this region.

Dependence of tracking efficiencyDependence of tracking efficiencyon hadron production modelson hadron production models

0 2 4 6 8 10P (GeV/c)

0.2

0.4

0.6

0.8

1.0

0.2

0.4

0.6

0.8

1.0

-200 -100 0 100 200x (mrad)

exclude |x| < 25 mrad, this time

Tota

l tra

ckin

g ef

ficie

ncy

Tota

l tra

ckin

g ef

ficie

ncy

Particle identificationParticle identification

e++

p

number of photoelectrons

inefficiency

e+

h+

0 1 2 3 4 5 6 7 8 9 10

p

P (GeV)P (GeV)

e

k

TOF CERENKOV CALORIMETER

3 GeV/c beam particles3 GeV/c beam particles

TOFCERENKOV

TOF ?CERENKOV

CERENKOVCALORIMETER

TOF

CERENKOV

CAL

+

p

datadata

ekpphe

phephe pPEEpPNpPpP

pPEEpPNpPpPEENpP

,,,21

2121 )|()|,,()|,()|,(

)|()|,,()|,()|,( ),,,,|(

tof cerenkov calorimetermomentumdistributionUsing the Bayes theorem:Using the Bayes theorem:

1.5 GeV 3 GeV 5 GeV

datadata

Forward PID: Forward PID: efficiency and purity efficiency and purity

1.5 GeV 3 GeV 5 GeV

Type

1Ty

pe2

Type

3

Type

1Ty

pe2

Type

3

Type

1Ty

pe2

Type

3

Type

1Ty

pe2

Type

3

Type

1Ty

pe2

Type

3

Type

1Ty

pe2

Type

3

0

0.6

0.4

0.2

0.8

1

pion

effi

cien

cy

0

0.6

0.4

0.2

0.8

1

pion

pur

ity

Iteration: dependence on the prior removed after few

iterations

truej

obstruej

tj NN /)( obs

jobstrue

jt

j NN /)(

we use the beam detectors to establishthe “true” nature of the particle

Use K2K thin target (5%Use K2K thin target (5%))• To study primary p-Al interaction• To avoid absorption / secondary interactions

5%5% Al target (20mm) Al target (20mm)

Raw dataRaw data

p > 0.2 GeV/c|y | < 50 mrad25 < |x| < 200 mrad

Pion yield: K2K thin targetPion yield: K2K thin target

K2K replica (650mm)K2K replica (650mm)

0 42 6P(GeV/c)

8 10 0 100 200-100-200x(mrad)

p-e/ misidentification background

Pion yieldPion yieldAfter After

all correctionall correction

5% Al target p > 0.2 GeV/c|y | < 50 mrad25 < |x| < 200 mrad

Systematics are still to be evaluated:• tracking efficiency known at 5% level• expect small effect from PID

0 42 6P(GeV/c)

8 10 0 100 200-100-200x(mrad)

SummarySummary

• HARP experiment has collected data for hadron production– With wide range of beam momentum and targets

• Analysis for Forward region– Improvement in tracking efficiency ~75%

• Downstream the dipole magnet: tracking efficiency ~98%• Matching through the magnet: ~75%

(MC behaves well, only scale factor by data)• Little dependence on hadron production models

– PID performance is also robust

• HARP first results for K2K thin target are available

Outlook & To doOutlook & To do

• K2K thin target for primary interaction– Compute deconvolution and migration matrix– Evaluate systematic uncertainties– Investigate super-forward region (|x|<25 mrad)– Empty target study for background subtraction– Normalization for absolute cross section

(using minimum biased trigger)

• Analysis of K2K replica target for far/near ratio calculation

• Similar analysis for MiniBooNE target

• These are just two out of a number of measurements relevant for neutrino physics, those will be provided by HARP in the near future