harp
DESCRIPTION
HARP. K2K. Anselmo Cervera Villanueva. University of Geneva (Switzerland). Neutrino CH Meeting Neuch â tel, June 21-22, 2004. Overview. HARP K2K HARP contribution to K2K Geometrical acceptance Tracking efficiency Particle identification Pion yields. HARP. - PowerPoint PPT PresentationTRANSCRIPT
HARPHARP
Anselmo Cervera Villanueva
University of Geneva(Switzerland)
K2KK2K
Neutrino CH MeetingNeuchâtel, June 21-22, 2004
OverviewOverview
HARPHARP K2KK2K HARP contribution to K2KHARP contribution to K2K Geometrical acceptanceGeometrical acceptance Tracking efficiencyTracking efficiency Particle identificationParticle identification Pion yieldsPion yields
HARPHARP
The HARP experiment (CERN)The HARP experiment (CERN)
124 people 24 institutes
Physics goalsPhysics goals
Systematic study of Systematic study of HAHAddRRonon PProduction:roduction: Beam momenta: 1.5-15 GeV/c1.5-15 GeV/c
Target: from hydrogen to leadfrom hydrogen to lead
Motivation:Motivation: Pion/kaon yield for the design of the proton driver of neutrino neutrino
factories factories and SPL-based super-beams super-beams
Input for precise calculation of atmospheric neutrino fluxatmospheric neutrino flux
Input for prediction of neutrino fluxes for the MiniBooNEMiniBooNE and K2KK2K experiments
Input for Monte CarloMonte Carlo generators (GEANT4, e.g. for LHC, space applications)
K2kK2k
K2K Experiment (Japan)K2K Experiment (Japan)
First long base line neutrino experiment (250 km)First long base line neutrino experiment (250 km) To confirm with beam neutrinos the Super-K To confirm with beam neutrinos the Super-K
resultsresults
250 km
250 km
<E<E> = 1.3 GeV> = 1.3 GeV almost pure almost pure : ~98%: ~98%
-like event at Super-K-like event at Super-K
Overview of K2KOverview of K2K
12.9 GeV 12.9 GeV proton proton beambeam
++
++
pp
Target + HornTarget + Horn
pion monitorpion monitor(cerenkov)
decay pipe
muon monitor near detectorsnear detectors Super-KSuper-K
200m 100m 250km
no oscillationno oscillation
oscillationoscillation
predicted
10 2 43 5E (GeV)
4
8
12
x1010
measured
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
Far/Near spectrum ratio ≠ 1Far/Near spectrum ratio ≠ 1
confirmed bypimon
Beam MC
1Kt
HARP HARP contribution contribution
to to K2KK2K
Motivation of this analysisMotivation of this analysis
GeVE 75.05.0
mrad
GeVP
250
1
K2KK2K
interestinterest
K2
K f
ar/
ne
ar
rati
oK
2K
fa
r/n
ea
r ra
tio
Beam MC Beam MC,confirmed by Pion Monitor
To be measured To be measured by HARPby HARP
0.5 1.0 1.5 2.0 2.50 E(GeV)
oscillationoscillationpeakpeak
One of the largest One of the largest systematic errorssystematic errors
on the neutrinoon the neutrino oscillation parametersoscillation parameters
measured by the measured by the K2K experimentK2K experiment
comes fromcomes from
the uncertainty on thethe uncertainty on the far/near ratiofar/near ratio
pions producing neutrinos pions producing neutrinos in the oscillation peakin the oscillation peak
Forward AcceptanceForward Acceptance
MCMC
dipoleNDC1 NDC2
B
x
z
xz
y
top view
The ingredientsThe ingredients
trackingtracking p and measurement (at the interaction vertex) connect tracks with particle identification (PID) measurements
PIDPID Identify pions Reject protons, kaons and electrons
(p,)absolute
normalization
bin migration matrix
total efficiency pion yield
pion purity(background)
To measure all this one needs:
datadata We have reproduced in HARP the exact K2K conditions:
12.9 GeV/c proton beam An exact replica of the K2K target (2 aluminium)
jjj
ijtracki
acci
normi NMF 111
acceptance
pion id efficiency
Forward TrackingForward Tracking
dipole magnetNDC1 NDC2
B
x
z
NDC5
beam
target
Top view
11
22 NDC3
NDC4
2D segment
33
We distinguish 3 track types depending on We distinguish 3 track types depending on the nature of the matching object upstream the nature of the matching object upstream the dipolethe dipole1.1. 3D-3D3D-3D2.2. 3D-2D3D-2D3.3. 3D-Target/vertex 3D-Target/vertex (independent of NDC1)(independent of NDC1)
The idea is to recover as much efficiency as The idea is to recover as much efficiency as possible to avoid hadron model possible to avoid hadron model dependencies.dependencies.
Saturation of NDC1 in the beam Saturation of NDC1 in the beam spot regionspot region
High density of hits in NDC1 High density of hits in NDC1 provokes correlation between provokes correlation between particles particles
hadron model dependencieshadron model dependencies
problemsproblems solutionssolutions
systematic errorsystematic error
Momentum and angular resolutionsMomentum and angular resolutions
The momentum and angular resolutions are well inside the K2K requirements
MCMC
datadata
11type
No vertex No vertex constraint constraint includedincluded
MCMC
momentum resolutionmomentum resolution angular resolutionangular resolution
Tracking efficiencyTracking efficiency
It can be computed with the DATA as a function of x2 and x2
We use the MC to perform the conversion:
once demonstrated that DATA and MC agree in their x2 and x2 distributions
downi
recpi
acci
downi
acci
recpitrack
iN
N
N
N
N
N
downupi
downi
dipole magnetNDC1 NDC2
B
x
z
NDC5
beamtarget
Top view
11
2D segment
22
33
,, 22 px x
extrapolation to this plane
Module efficiencyModule efficiency
The efficiency of NDC2 and NDC5 is flat within ~5%. The efficiency of the lateral modules (3 and 4) is flat
within 10% The combined efficiency is not sensible to these
variations.
NDC2 NDC5
NDC3
NDC4
NDC 2 NDC 5NDC 4NDC 3
datadata
dipole
Downstream efficiencyDownstream efficiency
5
2
5
2
5
2
5
2
5
2
5
2
nmpp
NDCi
mmn
n
NDCi
NDCi
mmn
n
NDCi
NDCi
m
NDCi
downi
pnm
nm
m
NDC2 NDC5
NDC3
NDC4
)%298(
MCMC
dipole
Up-down matching efficiencyUp-down matching efficiency
Is the probability of matching a downstream track with the other side of the dipole
downi
recpidownup
iN
N
dipole magnetNDC1 NDC2
B
x
z
NDC5
beamtarget
Top view
11
NDC3
NDC4
2D segment
22
33
MC and data agree MC and data agree within ~3% in their within ~3% in their
shapesshapes
We tune to the DATA We tune to the DATA the absolute scale of each track type the absolute scale of each track type
MCMC datadata+
Total tracking efficiencyTotal tracking efficiency The MC reproduces the up-down
matching efficiency in terms of x2 and x2 within ~3%
The downstream efficiency is flat
We can use the MC to We can use the MC to compute the total efficiency compute the total efficiency
as a function of p and as a function of p and downup
idowni
tracki
)%298(
MCMC datadata+
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 CERENKOVCALORIMETER
3 GeV/c beam particles3 GeV/c beam particles
TOFCERENKOV
TOF ?CERENKOV
CERENKOV
CALORIMETER
TOF
CERENKOV
CAL
+
p
datadata
Pion ID efficiency and purityPion ID efficiency and purity
ekpphe
phephe
pPEEpPNpPpP
pPEEpPNpPpPEENpP
,,,21
2121
)|()|,,()|,()|,(
)|()|,,()|,()|,( ),,,,|(
toftof cerenkovcerenkov calorimetercalorimetermomentummomentumdistributiondistribution
Using the Bayes theorem:Using the Bayes theorem:
1.5 GeV 3 GeV 5 GeV 1.5 GeV 3 GeV 5 GeV
datadata
we use the beam detectors to establish we use the beam detectors to establish the “true” nature of the particlethe “true” nature of the particle
Pion yieldPion yield
To be decoupled from absorption and reinteraction effects we have used a thin target
datadatap-e/p-e/ misidentification misidentification background background
K2K replica targetK2K replica target
5% 5% Al target Al target
200% Al target
jjj
ijtracki
acci
i NM 111
datadata
ConclusionsConclusions The The tracking efficiencytracking efficiency is known at the level of is known at the level of ~5%~5% The pion ID correction factor is fully computed with The pion ID correction factor is fully computed with
data (except kaon contamination below 3GeV)data (except kaon contamination below 3GeV)
Small systematic errorSmall systematic error However, a detailed study of the PID systematic error However, a detailed study of the PID systematic error
is still missing is still missing
NextNext Increase tracking efficiency Increase tracking efficiency reduce systematic (<5%)reduce systematic (<5%) Use the MC to compute the systematic error on the pion Use the MC to compute the systematic error on the pion
ID correction factorID correction factor Larger MC and data statistics Larger MC and data statistics (p,(p,) 2D distribution) 2D distribution Detailed study of migration effectsDetailed study of migration effects Replica target Replica target z dependencez dependence