Transcript Status report on the performances of a magnetized ECC

Status Report on the
performances of a magnetized
ECC (“MECC”) detector
Pasquale Migliozzi
INFN – Napoli
L.S.Esposito,A.Longhin,M.Komatsu,
A.Marotta G.De Lellis, P.M.,
M.Nakamura, P.Strolin
Outline
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The OPERA experience
Why a magnetized ECC detector?
Detector overview and performances
Preliminary evaluation of the impact on
→, e→, e→, →e channels and the
corresponding CP ones
Outlook
The OPERA experience
The detector is being constructed at the Gran Sasso
Laboratory. Meanwhile several tests with charged particles
and neutrinos at FNAL are under way
An ECC brick is a self-consistent object. The whole detector
is just an ensemble of bricks.
Summary of the event
reconstruction with OPERA
(see Nakamura and De Lellis talks at the previous ISS meetings)
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High precision tracking (dx<1mm dq<1mrad)
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Energy measurement
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Kink decay topology
Electron and g/p0 identification
Multiple Coulomb Scattering
Track counting (calorimetric measurement)
Ionization (dE/dx measurement)
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p/ separation
e/p0 separation
Topological and kinematical analysis event by event
A bit of nomenclature
An emulsion plate
Base track
Layer 1
Plastic base
Layer 2
microtrack
brick simulation step by step
STEP 1
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Event generated with
OpRoot/Geant3;
STEP 2
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Angular and position smearing;
Eff. parametrization;
Pulse Height parametrization;
STEP 3
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Linking up-down;
Conversion to x.x.cp.root files
Electrons 6 GeV
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The events were generated with OpRoot
The smearing parameters are:
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Sx=0.4 micron,
Sy=0.25 micron,
Sz=2.5 micron.
(these value were obtained with a tuning on the data)
Eff. measured in the empty brick by using
cosmic muons
 Pulse Height parametrized by using the data in
the empty brick;
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Slopes resolution
(Tmicro-Tbase)
Tx-Tx1
s=0.014
Tx-Tx1
s=0.013
Tx-Tx2
s=0.014
MC
data
Ty-Ty2
s=0.008
Ty-Ty1
s=0.008
Tx-Tx2
s=0.014
Ty-Ty2
s=0.007
Ty-Ty2
s=0.008
eCHI2P vs PH
This is the results of the micro track slopes resolution simulation
(eCHI2P) and of the micro track pulse height parametrization (bt PH)
MC
Data
bg rejected
MC vs data comparison
Selected tracks characteristics:
st
 The track starts in the 1
plate;
 Number of segments [3,15] ;
 The track is in a box with a
surface of 1.8x1.8cm2;
 The first segment of the track
is in a cone around the beam
direction with open angle
defined by the beam width;
Yes
NO
Base Track angle resolution
Bin(i-1)=T(i)-T(1), i>1
MC
Data
Base Pulse and eCHI2P
MC eCHI2P
MC PH
Mean=26.4
RMS=3.0
Mean=1.2
RMS=0.9
data eCHI2P
data PH
Mean=26.3
RMS=3.0
Mean=1.1
RMS=1.0
about efficiencies…
Brick not exposed
to the e beam
Eff no lead MC pions
Reference brick eff.
Eff lead MC pions
Number of segments followed without propagation
(strongly related to micro track efficiencies)
Data
MC without
Efficiencies micro track
rejection
Eff. As measured in
Empty brick
(only cosmics exposition)
MC+eff.
Pulse height vs plate number
and
energy loss
Data
MC
MC: no correlation
between Micro tracks
momentum and pulse
height by construction
Pions 4 GeV
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The events were generated with
OpRoot
The smearing parameters are:
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Sx=0.25 micron,
Sy=0.25 micron,
Sz=2.5 micron.
these value are the same used for all
the “official” productions
NO parameters optimization was made
for this set of data.
TRIGGER
MC Tx
data Tx
MC Ty
data Tx
s=0.0055
s=0.0029
s=0.0053
s=0.0022
Slopes resolution
(Tmicro-Tbase)
Tx-Tx1
s=0.009
Tx-Tx1
s=0.01
MC
Tx-Tx2
s=0.01
data
Ty-Ty2
s=0.009
Ty-Ty1
s=0.01
Ty-Ty2
s=0.01
Tx-Tx2
s=0.01
Ty-Ty2
s=0.009
eCHI2P vs PH
This is the results of the micro slopes resolution simulation (eCHI2P) and of the
micro pulse height parametrization (bt PH)
MC
bg rejected
Data
Base Track angle resolution
Bin(i-1)=T(i)-T(1), i>1
MC
Tx
Mean=11.5
RMS=5.3
Data
Tx
Mean=11.7
RMS=5.3
Tx
Mean=11.2
RMS=5.3
Ty
Mean=11.4
RMS=5.2
Base Pulse and eCHI2P
MC eCHI2P
MC PH
Mean=26.6
RMS=2.9
Mean=0.7
RMS=0.5
data eCHI2P
data PH
Mean=26.6
RMS=3.0
Mean=0.8
RMS=0.8
Number of segments followed without propagation
(strongly related to micro track efficiencies)
Data
MC+eff.
Assuming eff.=84.%
(84.% at theta<0.1mrad
measured data)
An ideal detector exploiting a
Neutrino Factory should:
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Identify and measure the charge of the
muon (“golden channel”) with high accuracy
Identify and measure the charge of the
electron with high accuracy (“time reversal
of the golden channel”)
Identify the  decays (“silver channel”)
Measure the complete kinematics of an
event in order to increase the signal/back
ratio
“MECC” structure
DONUT/OPERA type target
+ Emulsion spectrometer +
TT + Electron/pi discriminator
B
Stainless steel or Lead
Film
Rohacell
3 cm
Electronic detectors/ECC
Assumption: accuracy of film by film alignment = 10 micron (conservative)
13 lead plates (~2.5 X0) + 4 spacers (2 cm gap) (NB in the future we plan to study
stainless steel as well. May be it will be the baseline solution: lighter target)
The geometry of the MECC is being optimized
Electron/pion discriminator à la NOMAD
(“our dream”)
Having an electronic e/p
discriminator would also allow for
the golden channel search!
A detailed study is needed in order
to optimize the discriminator
How many evts per brick?
Emulsions do not have time resolution
 How to disentangle events occurred at
different time?
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Key points
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The MECC needs a time stamp: TT mandatory
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The event density depends on the TT resolution
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CC/NC classification needs MECC-TT match
The OPERA-like approach (thick target, 10 X0, and TT
attached to the ECC) does not work
With the present set-up it works given the lightness of
the target-spectrometer region
The scanning is not driven by the electronic
detectors: the matching is done after event
location
Method for time stamp
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TT is placed downstream from the target region
(see previous slide)
TT segmentation varied between 1 and 5 cm
1 TT plane per projection
Only digital information is used: 2 tracks crossing
one TT strip give 1 hit
Optimization performed by using 10000 events NC
and CC for neutrinos with energy 15 and 40 GeV
#evts per brick as a function of
TT segmentation
Results
We assume for the time being 100 events per brick.
Possible improvements: a higher granularity TT
Momentum measurement
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Momentum and charge for mips
Momentum and charge for electrons
Methods
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Different methods have been tried
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Slope measurement (used in the past talk)
Sagitta measurement
Parabolic fit (also used for Kalman initialization)
Kalman reconstruction
All methods have been implemented in a single
program in order to ease the comparison
NB for all methods, but the Kalman, the
momentum is compared at the exit of the target
region (beginning of the spectrometer)
Momentum resolution
(1/p)(true –rec)/true
Charge misidentification
A better alignment
Electron studies (very preliminary)
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Single electron with energies 1-5-10 GeV have
been generated uniformly in the target region
reconstruction done on hits coming from the
primary electron (preselection at true level)
Method: parabolic fit (Kalman for electrons
requires some more work)
Given the non negligible energy loss in the target
the electron energy at the exit is considered
True momentum at the target exit
Estimate of showering electrons
Momentum resolution vs zvertex
q-mis vs zvertex
Given the true-hit based reconstruction, the quoted charge misidentification can
be seen as an lower limit. Anyhow it is a good starting point!
The silver channel
The old detector setup
• We considered a detector with 4 kton mass (lead)
• Only the muonic channel was considered (20% of the total decays)
• We considered only one event per brick
• Non-muonic decays discarded given the impossibility to measure the charge of the decay
products
The detected number of silver events
Below 3° the silver channel contributes very little in disentangling the intrinsic
degeneracy
What happens with the new setup based on the MECC technique?
How many silver events with MECC?
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Let us assume a constant target mass: 4 kton
We can collect about 100 events in a brick: x100 gain
We can search for non muonic decays: x5 gain
NB the background for non-muonic events has to be
carefully evaluated; rejection power due to the
improved kinematical reconstruction wrt OPERA could
be extremely useful
Overall gain: the silver statistics increases by a factor
500  significant contribution to the clone solution
well below 3° (studies are in progress)
i.e. for L=3000km at 1° we expect more than 500 (100)
silver events at δCP=90° (0°) rather than 1 or even less !
What about →e?
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NB there are not yet detailed studies
available
Just to give an idea (L=3000 km, θ13=5°,
δCP=90°):
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anti-e with the wrong electron charge: ~104
e from oscillation: ~102
We have to search for a few% effect, but
the S/B ratio may be improved by
kinematical cuts
Outlook
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Study the performance of a stainless steel target
Detailed study of the way how to magnetize the detector
Define a realistic baseline for the e/p discriminator: its
choice depends on the total target mass, the TT width (i.e.
how many evts per brick), the costs, …
Finalize the electron analysis: the e/p separation and the
charge reconstruction
Check the sensitivity to the “golden” (the muon threshold
is at 3 GeV!)
A full simulation of neutrino events is mandatory in order
to evaluate the oscillation sensitivity and provide the input
for GLOBES
We plan to perform a first exposure of a MECC on a
charged beam at CERN this year
The simulation program
Emulsion digitization is handled by this program
ROOT
OpGen
(NEVGEN)
OpROOT
GEANT3
ORFEO
FEDRA
Off-line reconstruction program
for emulsion data
A realistic emulsion simulation (1/2)
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The events are generated with Geant3/OpRoot with a
1 brick detector.
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The output of this step is a root Ttree filled with generator level microtracks
called TreeM (no smearing effects); - [ if a beamfile is used in the output file
can be added a Ttree called TreeH with the beamfile informations]
The object microtrack is defined in the class Micro_Track (look at
http://web.na.infn.it/index.php?id=527);
2.
The emulsion digitalization
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accept as input a root Ttree file filled with microtracks as defined in the
class Micro_Tracks;
this step is decoupled from the event generation so, in principle, the events
could be produced also with the OpSim package or with other generators
(Geant4, FLUKA) ;
At this step is performed the digitalization of the emulsions;
The output of this step is a root Ttree filled with digitalized microtracks
called TreeMS (same structure of the TreeM);
A realistic emulsion simulation (2/2)
3. Analysis tools:
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A tool to perform the link up-down to take into account the linking
efficiency, this tool accept as input the TreeMS and produce as output a
root Ttree (TreeMSE) filled with the digitalized microtracks that survive
to the linking up-down;
A tool to convert the micro tracks Ttree (TreeM/TreeMS/TreeMSE) in
x.x.cp.root files;
TAKE CARE: since at generator level there is no cut on the minimum energy
of the microtrack , to make a realistic analysis it is fundamental to apply the
link up-down algorithm that has low efficiency for very low energy base
track (<5MeV)
4. Some tools to add background are included in the package
(it is possible to merge real bg data or simulated bg with simulated
events at cp-files level). Of course for people not using cp files it is
also possible to merge simulated bg with simulated events by using
standard root commands.
2 points simulation of a micro-track
dx= dx1 +dx2 - dy= dy1 +dy2 - dz= dz1 +dz2
dSx 
dz1
dx1
dy1
dy2
dz2
dz
 cos( )  tan( )  dSx0   z  cos( )  tan( )
dz  z dz  z
dy
dz
dSy 
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 cos( )  tan( )  dSx0   z  cos( )  tan( )
dz  z dz  z

By taking into account that dx and dy are statistical
errors gaussian distributed and dz is a maximal error
with a flat distribution, these assumptions
automatically give the expected dependences on q:
z
dx2
dx
sS L 0 2  (sSx  cos ) 2  (sSy  sin  ) 2
sST 0 2  (sSx  sin  ) 2  (sSy  cos ) 2

sS L  sS L 0 (1  z  tan )
sS L 0
sST  sS L 0
“Since the base-tracks are
constructed by using the 2 points at
base, the same results are obtained
for free for base-tracks too”
10. GeV muons
Transversal and
longitudinal resolution
for simulated
10.GeV pions at q=0.7 mrad
SlopLong1
s=0.037
SlopLong2
s=0.037
SlopTr1
s=0.008
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Smearing parameters are:
Sx=0.25 micron,
Sy=0.25 micron,
Sz=2.5 micron.
SlopTr1
s=0.008
Pulse height vs plate number
and
energy loss
Data
MC
MC: no correlation between
Micro tracks momentum
and pulse height
by construction