CNGS beam monitoring with OPERA detector

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CNGS beam monitoring with OPERA detector
Stefano Dusini INFN-Padova On behalf of OPERA
Collaboration
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OPERA detector
OPERA is designed for the observation of
???????oscillations through ? appearance in the
CNGS beam

• Target
• Lead/emulsions bricks alternated to scintillator
  strips
• 206336 bricks 1.8 kton

• Muon Spectrometer
• Vertical drift tubes for ? P measurement from
  deflection through 24 magnetized iron slabs.
• Magnet instrumented with 22 RPC plane for

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OPERA installation in pictures
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Status of OPERA installation
The commissioning of the full detector is in
progress
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Target Tracker
Plastic scintillator strips (6.7m x 2.6cm x
1cm) readout by WLS fibres Hamamatsu M64
PMTs Installation ended in May. Commissioning is
in progress
TTplanes
n
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Target Tracker commissioning
60ltNp.e.lt120 30ltNp.e.lt60 9 ltNp.e.lt30 3 ltNp.e.lt9 1
ltNp.e.lt3
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Target Tracker Commissioning
Single muon
Muon boudle
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Spectrometer

• Dipolar magnet (B1.55 T)
• 24 iron slabs, 5 cm thick 2 cm gap
• Gaps instrumented with RPCs with horizontal and
  vertical strips with digital readout
• 6 vertical Drift Tubes station with 0.3mm
  resolution

• Installation end in May 05
• Commissioning of the detector and DAQ in progress

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RPC Commissioning
The installation and commissioning of the
electronics/DAQ in progress 4 RPC plane tested in
May 05 Preliminary using premixed gas bottles 60
hour of data taking 1300 muon recorded (24
di-µ, 3 tetra-µ, 1 hexa-µ)
Clean muon events only
North
South
Clean events (1 hit per plane with ?2 lt 2) Obs.
973 ev/62h17 15.6 0.5 mu/h Expected from MC
15.2 0.3 mu/h
East
West
Absolute MC normalization
Detector performances well under control
East
West
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RPC Commissioning
Vertical view
Horizontal view
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DAQ
DAQ structure based on a Gigabit Ethernet network
(1200 nodes)

• A node of the network is
• Target Tracker, FEB (64 PMT)
• Drift Tubes, TDC Board (96 ch)
• RPC, Controller Board (9 FEB 1 RPC plane)

The nodes can auto trigger and time stamp the
data A clock is distributed to each node to
synchronize the time stamp with GPS clock
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DAQ data sorting in time
Trigger conditions Sensor 1 p.e. /pixel , zero
suppress 0.5 p.e. ? data rate 28
kbytes/sec Wall validation 1 p.e. in X and Y
within 200 nsec (time stamp)
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Cosmics in TT
Hits time distribution along the particle path
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Summary of OPERA installation

• OPERA electronic detector are in time for the
  start-up of the CNGS beam
• SM1 fully instrumented (TargetTracker
  DriftTubes XPC/RPC)
• SM2 spectrometer without DriftTubes, moun
  momentum and charge will be measured using
  XPC/RPC only
• No ECC Brick will be present for Run1
• In Run1 neutrino interactions inside OPERA will
  occur only in the magnets

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Beam characteristics

• CNGS characteristics in Run 1
• ltEgt17 GeV
• 1 CNGS cycle per SPS cycle (12s FT 6s CNGS
  4.8s MD)
• Intensity 1.8 x 1017 pot/day (nominal 2.29 x
  1017 pot/day)
• Total pot Run1 0.3?1019 pot

CC rate on isoscalar target per kton normalized
1019 pot

• How to monitor the beam
• Muon rate from ??CC interactions in the detector
  and surrounding materials
• Measure muon energy spectrum and reconstruct ??
  energy spectrum
• Stability in time of the muon rate

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Rock muons

• Muons are MIP up to 500 GeV (dE/dx 2 MeV cm2/g)
• Muons from ??CC interactions in the rock (?rock
  2.71 gr/cm3) surrounding the experiment can
  travel few hundred meters

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Optimal volume of the simulation
Muons/day
m
R
m
m
LLHall

• Simulation ??CC on Ca and C
• the Plateau is reached for a cylinder of rock
  with R25 m and LLHall 175 m.
• the rock-muons hitting OPERA are about 60 per
  day.
• there are no appreciable differences between
  simulated Ca and C vertices.

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Muon reconstruction

• The muon candidate is chosen as the longest track
• Energy is reconstructed by range Erec(range) and
  with spectrometers in case it crosses them

Tracks with vertex in Borexino
Charge measured

• Background
• ? contamination (mis-id as muon)
• mis-id topology (Through-going / stopped)
• Can be remuved with Erec gt 1.2 GeV

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Moun momentum and charge reconstruction
Momentum and charge of mouns are measured using a
Kalman filtering algorithm on the muon candidate
track
Simulated ??CC event
Top view
TT
Side view
TT
Spectro
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Moun momentum and charge reconstruction
Top view
Momentum and charge of mouns are measured using
Kalman filtering algorithm on the muon candidate
track

• The initialization of the KF use
• Drift Tubes RPC for through going or stopping
  in the magnet
• Constant value for stopping or exiting the Target
  

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Moun momentum and charge reconstruction
Charge mis-id
Preliminary
Preliminary
Preliminary
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Muon reconstruction with XPC/RPC only
XPC/RPC alone can provide a good estimation of
the momentum of the muon
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Rock through-going muons
The overall resolution is better than 20 because
roughly 50 of tracks cross two spectrometers
(two independent measurements)
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Neutrino energy reconstruction
Correlation between neutrino energy at vertex and
entrance muons energy.
NCC year-1
Neutrino CC spectrum with primary muons hitting
OPERA
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Neutrino energy reconstruction
After only 27 days (22 with nominal beam) 1300
events collected.
NCC
NCC

• - simulated neutrino spectrum
• reconstructed neutrino spectrum

• Spectrum of entrance energy for
• reconstructed muons
• simulated muons
• from lateral rock
• from up rock
• from Borexino

ltE?gt 40.47(21.36) GeV ltE?gt 38.60(21.86) GeV
ltEµgt 15.12 GeV ltEµgt 15.47 GeV
In parenthesis the mean is computed considering
only E? 40.0 GeV
The mean neutrino energy is resolved with 5 of
precision
The resolution in energy is sensible to the high
energy part of the beam.
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Summary table of rock muons
Identified Muons 48.8 / day Reconstructed Muons
47.8 / day Muons with possible qId 41.1 / day
The cut Erecgt1.2GeV reduce pion contamination
the sample purity is of 99.4
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Summary table of rock muons
Proportion of about 2 2 1 between Lateral
Up Borexino zones.
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Neutrino CC interaction in the Magnets
Weight of Magnets 2 x (675 ton slabs 315 ton
coils) 2kton

• Beam intensity 1.8 x 1017 pot/day
• E lt 100 GeV 7.(slabs) 3.3 (coils) CC
  events/magnet/day
• E lt 400 GeV 7.3(slabs) 3.4 (coils) CC
  events/magnet/day
• For 0.3 x 1019 pot
• E lt 100 GeV 117 (slabs) 54.8 (coils) CC
  events/magnet
• E lt 400 GeV 122 (slabs) 57 (coils) CC
  events/magnet

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Muon reconstruction
Simple muon identification criteria requiring Eµ
gt 1.2 GeV and the muon track to pass at least 10
RPC plane
4 stops in the one of the two spect.
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Summary table
Muon ID 12 events/day p/q rec. 4.3 events/day
(crossing full spec with XPC)
The evaluation of the purity of the muon sample
and the contamination from NC events and rock
muons is under study
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Summary and future steps

• In Run1 OPERA will collect 1000 muon from ??CC
  (813 rock 163 spectro)
• The statistics is enough to evaluate a 3 of beam
  intensity attenuation, equivalent to 0.1 mrad
  misalignment
• It can be possible evaluate the mean neutrino
  energy with 5 of precision after 27 days