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 target

3. 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

12

x1010

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

)

SK

SK

FD

FD

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 Identifications

Beam 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 withcosmics 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 mod4mod5

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

2

022

L

ttpm 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

z

NDC5

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

jN

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

x

z

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

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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 1

Blue: 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)

Tot

al tr

acki

ng e

ffici

ency

Tot

al tr

acki

ng e

ffici

ency

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

Tot

al tr

acki

ng e

ffici

ency

Tot

al tr

acki

ng e

ffici

ency

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

CERENKOV

CALORIMETER

TOF

CERENKOV

CAL

+

p

datadata

ekpphe

phephe

pPEEpPNpPpP

pPEEpPNpPpPEENpP

,,,21

2121

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

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

tof cerenkov calorimeter

momentumdistributionUsing 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

Typ

e1

Typ

e2T

ype3

Typ

e1

Typ

e2T

ype3

Typ

e1

Typ

e2T

ype3

Typ

e1

Typ

e2T

ype3

Typ

e1

Typ

e2T

ype3

Typ

e1

Typ

e2T

ype3

0

0.6

0.4

0.2

0.8

1

pion

eff

icie

ncy

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 mrad

25 < |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 yield

After After all correctionall correction

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

25 < |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