Anselmo Cervera Villanueva University of Gen eva (Switzerland)
description
Transcript of Anselmo Cervera Villanueva University of Gen eva (Switzerland)
Anselmo Cervera VillanuevaAnselmo Cervera VillanuevaUniversity of GenUniversity of Genevaeva
(Switzerland)(Switzerland)
Rencontres de Moriond Rencontres de Moriond 25 March 200425 March 2004
HARPHARP
On behalf of the HARP CollaborationOn behalf of the HARP Collaboration
FirstFirst
physics resultsphysics results
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OverviewOverview
The experiment and its objectivesThe experiment and its objectivesDetector performanceDetector performance
TrackingParticle identification
Closing the first analysis cycleClosing the first analysis cycleUsing our K2K thin target dataEfficienciesMomentum and angular distributions
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The HARP experimentThe HARP experiment
124 people 24 institutes
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Physics goalsPhysics goalsSystematic study of Systematic study of HAHAddRRonon PProduction:roduction:
Beam energy: 2-15 GeV2-15 GeVTarget: from hydrogen to leadfrom hydrogen to lead
Motivation:Motivation:Pion/kaon yield for the design of the proton driver of neutrino factories neutrino factories and SPL-based super-beams super-beamsInput for precise calculation of atmospheric neutrino fluxatmospheric neutrino fluxInput for prediction of neutrino fluxes for the MiniBooNEMiniBooNE and K2KK2K experimentsInput for Monte CarloMonte Carlo generators (GEANT4, e.g. for LHC, space applications)
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Motivation of this analysisMotivation of this analysis
pions producing neutrinos pions producing neutrinos in the oscillation peakin the oscillation peak
GeVE 75.05.0
mrad
GeVP
250
1
K2KK2K
interestinterest
K2K
far
/nea
r ra
tio
K2K
far
/nea
r ra
tio
Beam MC Beam MCconfirmed byPion 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 K2K systematic One of the largest K2K systematic
errors errors
comes from comes from
the uncertainty of the far/near ratio the uncertainty of the far/near ratio
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P > 1 GeV
mradsx
]200 ,200[
Geometrical acceptanceGeometrical acceptance
dipoleNDC1 NDC2
B
x
z
K2Kinterest
K2Kinterest
MCMC
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TrackingTracking
MCMC
datadata
dipole magnetNDC1 NDC2
B
x
z NDC5
beam
target
Top view
momentum resolutionmomentum resolution
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22
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momentum biasmomentum biascase
NDC3
NDC4
No vertex No vertex constraint constraint includedincluded
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22
datadatacase
case
beam particles
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//pp byby Time of FlightTime of Flight
3 GeV beam particles3 GeV beam particles 12.9 GeV K2K thin target12.9 GeV K2K thin target
t0
tw
L
12
022
L
ttpm w
0-4.5 GeV
target
Tof Wall
Beam time detectors
datadata
pp
+light particles
mom < 4.5GeV
ta tb tc
Tof wall resolution is Tof wall resolution is ~160 ps ~160 ps
77 /p at 3 GeV/p at 3 GeVbeam time resolution is beam time resolution is ~180 ps ~180 ps
tof walltarget
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//pp by by Threshold CerenkovThreshold Cerenkov
/ p above 3 GeV/ p above 3 GeV/ k from 3 to 9 GeV/ k from 3 to 9 GeV
2
20 /11
1 pmn
NN phel
P (GeV)
Nph
el
2.6 GeV
3-15 GeV
+
e+
9.2 GeVthreshold for pions threshold
for kaons
e++
3 GeV beam particles3 GeV beam particles
number of photoelectrons
p p
+
5 GeV beam particles5 GeV beam particles
number of photoelectrons
datadata
inefficiency
inefficiency
cerenkov
num
ber
of p
hoto
elec
tron
s
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electron / hadronelectron / hadron
Above 3GeV the electron and pion
distributions have a serious overlap
12.9 GeV K2K thin target12.9 GeV K2K thin target3 GeV beam particles3 GeV beam particles
cere
nko
vce
ren
kov
calo
rim
eter
calo
rim
eter
0-3 GeV
datadata
e++
e+
h+
3 GeV beam particles3 GeV beam particles
p
small electronsmall electroncontaminationcontamination
hadronshadrons
datadata
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EfficienciesEfficienciesPion efficiency in the (p,) bin ij
trackij
ijaccij
trackij
trueij
accij
trueij
ijij
N
N
N
N
N
N
N
N
geometrical acceptance
tracking efficiency
pionefficiency
depends on correlation between particles
may depend on hadron generator
correlationindependent
computed with single particle MCverified with data
correlation independent
estimated with MCverified with databut can be compuded
using the data
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Tracking efficiencyTracking efficiencydipole
NDC1 NDC2
B
x
z
NDC5
beam
target
3 MC hadron 3 MC hadron generatorsgenerators
Sources of inefficiencySources of inefficiency
hit efficiency (80%) high hit density in NDC1
PR confusion
Improvements to came:Improvements to came:
Use case
Vertex constraint
single track eff single track eff
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22
22
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Raw pion yieldRaw pion yieldall particlesall particles
identified pionsidentified pions
12.9 GeV K2K thin target12.9 GeV K2K thin target datadata
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… … corrected by efficiencycorrected by efficiency
These plots reflect the lack of MC statisticsThese plots reflect the lack of MC statistics
Integrated over Integrated over and p and p
No systematic errors includedNo systematic errors included
arbi
trar
y un
its
arbi
trar
y un
its
identified pions identified pions
integrated over integrated over P
proton background for Tof3 MC hadron generators
IMPORTANTIMPORTANTThis background This background can be computedcan be computed
with the data with the data
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Systematic sourcesSystematic sources Initial estimation
methodRelevance Reduction
Acceptance Data small
Tracking efficiency
Several hadron generators
+
User defined final state medium Measure with data
Momentum
& angular biases
Several hadron generators
+
beam data particlessmall Vertex constraint
(p,) bin migration(track purity)
(p and biases)
(p and finite resolution)
Several hadron generators small1.Optimize (p,) binning
2.Reduce biases
3.Improve resolution (vertex)
Proton
backgroundSeveral hadron generators small
Can be fully measured in the data
Electron background Several hadron generators negligibleCan be fully measured in
the data
Kaon background Several hadron generators smallMeasured with data above
3GeV
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ConclusionsConclusionsHARP was proposed in 1999HARP was proposed in 1999And recorded 420M events in 2 yearsAnd recorded 420M events in 2 yearsToday we present our first physics results Today we present our first physics results We have used 1/6 of our K2K thin target data …We have used 1/6 of our K2K thin target data …… … and very limited MC statistics …and very limited MC statistics …… … because we have used this analysis to set-up our MC because we have used this analysis to set-up our MC production mechanism (today 1M events/day) production mechanism (today 1M events/day) Pid detectors are well understoodPid detectors are well understoodThe vertexing algorithm already working (improve )The vertexing algorithm already working (improve )Several ideas for recovering efficiency to be implementedSeveral ideas for recovering efficiency to be implementedData statistics is not a problem (5.6 M events Data statistics is not a problem (5.6 M events after data qualityafter data quality))Small systematic error expectedSmall systematic error expected
pp /
420 million events
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Next steps Next steps
Analysis for K2K and MiniBooNE replica targetsAnalysis for K2K and MiniBooNE replica targets
Full data statisticsFull data statistics
Large MC statisticsLarge MC statistics2D distribution (p, 2D distribution (p,
Detailed study of systematic errors …Detailed study of systematic errors …
… … and migration effects (expected to be small)and migration effects (expected to be small)
This program will be completed in 3 months and presented at NEUTRINO 2004NEUTRINO 2004