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
0.6
0.8
1
P(GeV/c)
acce
ptan
ce
0.2
0.4
0.6
0.8
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