Reconstruction of neutrino interactions in PEANUT
G.D.L., Andrea Russo, Luca Scotto LavinaNaples University
Plan of the presentation•Introduction•Monte Carlo simulation of PEANUT
•Event generator•DIS,QE and RES merging•Event reconstruction•Optimization of the selection
•Data analysis•Results•Conclusions
PEANUT detector
BL033
Neutrino beam and Cosmic ray exposure
Beam Position Start End Duration (day)
NEUTRINO 141 2005/10/20 16:25 2005/11/07 09:20 17.75
COSMIC RAYS 2005/11/07 09:40 2005/11/07 11:40 0.08 (2h)
Monte Carlo simulation of PEANUT5000 neutrino interaction simulated per each kind of scattering: DIS, QE and RES
DIS
W2 distribution Q2 distribution
RES
QE
W2 distribution Q2 distribution
Charged-particle multiplicity in interactions
DIS
RES QE
“True” charged multiplicity(at least one micro-track)
Monte Carlo simulationEstimate of the expected fractions of
DIS, RES and QE scattering events in PEANUT
GeVInteracting neutrino energy
The fractions of DIS, RES and QE events were estimated by folding the previous distributions with the NuMI energy spectrum
No explicit information on the NuMI energy spectrum, so we used RES and QE interactions, since QE and RES cross sections slightly depend on
the interacting neutrino energy
RES QE
Results:
(64.4 ± 0.5(stat) ± 1.2(syst))% DIS
(13.1 ± 0.3(stat) ± 0.3(syst))% RES
(22.5 ± 0.4(stat) ± 0.6(syst))% QE
Systematic error from the QE and RES comparison
MonteCarlo details
• Orfeo single brick simulation
• Grain distribution from data
• Micro-track position and angular smearing simulated
• Tracking efficiency as in data
• SFT simulation not included yet: as a first attempt we assume a constant track matching efficiency of 80%
A procedure to identify neutrino events optimized with the MC simulation
• At least two tracks reconstructed • Topological cuts on reconstructed vertices: Impact Parameter, IP < 50 µm and track-vertex longitudinal distance, z < 3000 µm
• All tracks downstream of the vertex
• At least one track confirmed by SFT detector
• z-versus-IP bi-dimensional cut
IP90
m
)
Multiple track events
• Efficiency on signal = (84 ± 2)% of vertices• Background rejection = (61 ± 3)%
Estimated using backward two-track vertices
IP90 defined as 90% upper bound on Impact Parameter
Cut defined by the blue line provides:
• Track made of at least 5 base-tracks
• The track with UP > 3 and DOWN < 4
• The track confirmed by SFT detectors
Single track events
For example: this track (black line) has UP=4 and DOWN = 2
Efficiency of neutrino event reconstruction
Total reconstruction efficiency (multiple & single track events)
(54.3 ± 0.8)% DIS
(50.4 ± 0.7)% QE
(54.1 ± 1.7)% RES
Accounting for the differentfractions
(64.4 ± 1.2(syst) ± 0.5(stat))% DIS
(13.1 ± 0.3(syst) ± 0.3(stat))% RES
(22.5 ± 0.6(syst) ± 0.4(stat))% QE
Total reconstruction efficiency = (54.1 ± 0.7)%
Charged-particle multiplicity afterevent reconstruction
Data analysis
Scanning areasAll 57 plateshave been
general scanned:
5.55 x 4.30 cm^2 = 23.9cm^2
General scanning mode
Measured density of aligned base-tracks: 4 base-track / mm2 (transportation order)
0.7 base-track / mm2 (assembly order)
30 plateshave been
general scanned:
11.1 x 4.30 cm^2 = 47.8 cm^2
PEANUT emulsionsTransportation order Beam exposure
~ 8 m
Track reconstruction
=13 mrad
Micro-track angular resolution
Position and angular resolution in the plate to plate alignmentConsecutive base-track accuracy
~ 5 mrad
= 0.7m = 3mrad
Base-track resolution: spatial and angular differencebetween a base-track and the corresponding volume track
Density of aligned base-tracks ~ 4/ mm2
Track reconstruction in transportation order
Characterization of the tracks in transportation order
Due to low momentum protons (~100MeV)
High ionizing power (at least 10 segments in the following plots)
High tracking efficiency
Beam tracksat least 4 segments in the following plots
NuMI beam peak(x, y-( ~ )50,0 )mrad
MIP particles:<Grain number> ~ 24
Tracking efficiency
Density of aligned base-tracks ~ 0.7 / mm2
Emulsion-SFT matching
yx
tx ty
• x = 1190 m
• y = 1240 m• tx = 5 mrad• ty = 8 mrad
Impact parameterand z distribution
track to vertex longitudinal distance
IP z
~ 60% up to 10 µm
Neutrino event identification
64797 volume tracks reconstructed
• 4074 vertices reconstructed
•1045 with all forward tracks
•25 confirmed by SFT
•7 pass the “z versus IP” cut
•22293 made of more than 4 base-tracks
•144 confirmed by SFT
•13 with UP > 3
Identification of 20 neutrino interactions in the fiducial volume
Single track events Multiple track events
MC Multiplicity
“High” multiplicity events not matching the SFTdz (m) ip (m)
697 1.2
697 0.4
1988 8.2
dz (m) ip (m)
912 2.4
2203 0.8
912 2.3
dz (m) ip (m)
941 3.4
2226 10.0
941 3.9
tx (mrad) ty (mrad)
-26 244
156 -126
-99 379
tx (mrad) ty (mrad)
394 -231
-642 -2
355 -402
tx (mrad) ty (mrad)
-381 -380
116 -131
-43 -716
“High” multiplicity events not matching the SFTdz (m) ip (m)
2041 18.1
2041 20.1
2041 22.1
dz (m) ip (m)
1318 2.9
1318 4.2
1318 4.9
tx (mrad) ty (mrad)
67 231
66 -116
-134 51
tx (mrad) ty (mrad)
-39 88
-101 129
-44 93
Expected number of events in the brick
Beam Begin End Duration (days)
NEUTRINO 2005/10/20 16:25 2005/11/07 09:20 17.75
COSMIC 2005/11/07 09:40 2005/11/07 11:40 0.08
Neutrino interaction ratein an iron target exposed to NuMI
in the near hall(2 * 105) / (year * ton)
37 ± 6 neutrino interactions expected in the analyzed volume
Nmes/total = 37 ± 8 neutrino interactions estimated from the 20 observed events after efficiency correction
This value (increased by 8%) accounts for the lead target
Conclusions• A volume of 337 cm3 (half brick volume) was general scanned in one
PEANUT brick• Detailed single brick Monte Carlo simulation of PEANUT used to
define a procedure to identify neutrino interactions• The reconstruction efficiency of neutrino events for this procedure has
been evaluated with Monte Carlo• 20 neutrino interactions have been identified in the volume• After the efficiency correction, we estimate (37 ± 8) neutrino
interactions happening in the volume• Good agreement with the number of expected events (37 ± 6)
computed from the fluxOutlook
• Enlarge the statistics
• Include SFT simulation in Monte Carlo