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