Detection and reconstruction of π0 mesons in the ICARUS detector.

neutrino.fuw.edu.pl

Detection and reconstruction of π0 mesons in the ICARUS detector.

Detection and reconstruction

of π 0 mesons in the ICARUS

detector.

Tomasz Palczewski.


Outline










Motivation.

Neutrino oscillations.

ICARUS T600 detector.

π 0 measurement method.

Energy Resolution.

Data selection (Data from Pavia test run).

π 0 Invariant mass measurement.

MC Simulations.

– Simulation of π 0 production in ν interactions.

Conclusions.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Motivations:

Energy Calibration - The decay of a particle

with known mass gives a good test.

Distinction between ν e charge current interaction (CC)

from the ν µ neutral current interaction (NC)

– Good detector capability to separate electrons from pions is

required.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Neutrino oscillations

Solar and atmospheric neutrino experiments have shown that

neutrino oscillations are due to a mismatch between the flavor

and mass eigenstates of neutrinos.

The relationship between these eigenstates is given by:



⎢ν α 〉 is a neutrino with definite flavor. α = e (electron), µ

(muon)) or τ (tau).

⎢ν i 〉 is a neutrino with definite mass. i = 1, 2, 3.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


SNO

The Sudbury Neutrino Observatory (SNO)

was located 6800 feet (about 2 km)

underground in CVRD Inco's

Creighton Mine in

Sudbury, Ontario, Canada.

The detector was designed to detect solar

neutrinos through their interactions with

deuterium nuclei and atomic electrons.

The detector turned on in May of 1999, , and

was turned off on November 28, 2006.

It is planned to re-use the existing

experimental structures for the SNO+

experiment.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Super-Kamiokande

Kamiokande.

Super-Kamiokande

Kamiokande, , or Super-K for short, is a neutrino

observatory in Japan. . The observatory was designed to search for

proton decay, , study solar and atmospheric neutrinos, , and keep

watch for supernovas in the Milky Way Galaxy.

Super-K K is located 1,000 m underground in the Mozumi Mine

(Kamioka

Mining and Smelting Co.) ) in Hida city (formerly Kamioka

town), Gifu, Japan.

The detector consists of a cylindrical stainless steel tank 41.4 m tall

and 39.3 m in diameter enclosing 50,000 tons of ultra-purified

water.

The tank volume is divided by a stainless steel superstructure into i

an inner detector (ID) region that is 33.8 m in diameter and 36.2 2 m

in height and outer detector (OD) which consists of the remaining

tank volume.

Mounted on the superstructure are 11,146 photomultiplier tubes

(PMT) 20 inches in diameter that face the ID and 1885 8-inch 8

PMTs

that face the OD. There is a barrier that optically separates the e ID

and OD.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Neutrino oscillations


Maki-Nakagawa-Sakata matrix (also called the "MNS matrix", "neutrino

mixing matrix„ )




where s12 = sinθ12, c12 = cosθ12, …

The phase factors α1 and α2 are non-zero only if neutrinos are Majorana

particles.

The phase factor δ is non-zero only if neutrino oscillation violates CP

symmetry.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


ν µ -> ν e apperance

θ13

In the experiments looking for θ 13 an important role is the

efficiency of distinction between photons induced shower

from pi0 decay and the electron showers from electron

neutrino interactions.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


ICARUS T600

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


ICARUS T600




The ICARUS detector is composed by two semi-independent,

independent,

symmetric, filled with liquid argon modules of approximately 3.6 x 3.9 x 19.9

cubic meters.

The charge particles passing inside the volume, where a uniform electric

field is applied, produces ion-electron pairs. A fraction of them, depending

on the field intensity and on the density of ion pairs, will not recombine and

will immediately start to drift parallel to the field in opposite e directions. Only

the motion of the much faster electrons induces a current on a number n

of

parallel wire planes located at the end of the sensitive volume.

The choice of the liquid argon was driven by the following considerations:

– it must be an excellent insulator and available at an extremely high purity level,

so that free electrons produced by ionization can drift in the liquid l

over long

distances

– it must have a high electron-ion pair yield with respect to the energy deposited

in the liquid

– it must be easily available in large quantities, , which is the case for argon, a

natural component of the Earth's atmosphere (1%)

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


ICARUS T600





The read-out chambers (two TPC for each half-

vessel) are mounted on the internal walls with the

cathode at the centre, to maximize the LAr sensitive

volume (corresponding to about 480 ton in mass).

The read-out chamber scheme consists of three

parallel planes of wires (horizontal, +60 and -60

degrees). Information is read both by electric

charge induction on the first two readout planes

encountered by drifting electrons and by electric

charge collection on the last readout plane.

The signals from the three wire planes, together

with measurement of the drift time, , provide a

(redundant) full 3-D 3 D image reconstruction of the

event.

The main features of this type of chamber is that

there is no charge amplification inside to allow the

drifting electrons to induce signals on different wire

planes. This requires a high quality electronics to

maintain a good signal over noise ratio. The total

number of electronic read-out channels is about

55000.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


ICARUS T600

• 2 modules - 3.6x3.9x19.9 m^3.

• Inside of modules there is a

cathode.

• Data acquisition system: 3 planes

of wires.

Hall B, Gran Sasso (Italy).

detektor ICARUS T600

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


π 0

Mass m = 134.9766 ± 0.0006 MeV

Mean life time ( 8.4 ± 0.6 ) * 10 -17

17 s

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Some kinematical limits

in π 0 →γγ

decays

The two body decay.

Angle beetwen two photons.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Some kinematical limits

in π 0 →γγ

decays

p γ 1

θ

p γ 2

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


MC PI0 – 200 MeV.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).

Energy of photons [MeV]


MC PI0 – 500 MeV.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).

Energy of photons [MeV]


Some kinematical limits

in π 0 →γγ

decays

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


t (cm)

Measurement method

A dedicated HIGZ-based

Graphical User Interface

visualization tool allows to

select directly the region with

the hits belonging to a shower,

by building a

indicates a reconstructed hit

in Collection view.

polygonal line around the

shower directly on the Collection

view.

Anatra program.

u (cm)

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).

More details about Anatra program [Study of the low and intermediate energy electron samples with the ICARUS

T600 detector (Doctoral Thesis, 12/01/2006 Alessandro Menegolli) ]


Energy resolution.

• Monte Carlo (FLUKA) – generated

electromagnetic showers:

• photons and electrons

• different angles θ , φ

• We would like to check is there any

dependence on the angle of the shower with

respect to the wires because Anatra energy

measurement technique is based only on the

information from one plane of wires.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Electromagnetic Shower.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Electromagnetic showers

• A good agreement between reconstructed energy

and generated energy was obtained after the introduction of

a common multiplicative factor 1/ε, where ε can be

interpreted as the efficiency of the hit reconstruction

in the shower area.

• ε = 0.85 ± 0.02

• In the range 50 – 5000 MeV no dependance of ε

from the energy has been found.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


The energy of MC simulated electrons and photons inside the

ICARUS T600 detector was reconstructed with the same

reconstruction tools as we used later for the π 0 events.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Data selection

Scanning was done in several laboratories.

Warsaw, Cracow, Katowice, Pavia.

Sometimes same event measured in the different

laboratories produces different values in vertex

coordinate and shower energy determination due to

the presence of crowded environment ( noisy

background )

212 hadronic interactions with at least one meson

candidate were collected for further analysis.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Hadronic interaction in a crovded

environment

Run 600 Event 17

Noisy background

m.i.p tracks

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Scanning rules adopted for the pre-selection of

hadronic interactions with π 0 production:

At least two, well separated electromagnetic

cascades originated by photons pointing to the

interaction vertex were demanded.

Interactions with neutral meson candidates

were rejected when ionization due to other

tracks and interactions in their neighborhood

was so high that it seriously affected the

cascade energy determination.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


REJECTED

Example of the accepted (left)

and rejected event (right)

Overlapping of tracks

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Measurement of (γ,γ)(

) systems

For the evaluation of the invariant mass M γγ of (γ,γ) systems are needed:

1. The two shower energies, E and E 1 2

2. The angle θ 12 between the two showers

γγ

Measurements done

in different laboratories

C = calibration factor converting from

ADC to MeV (after MC simulations)

are in agreement

C = ( 152 ± 2 ) * 10-4 fc/(

/(ADC* ADC*µs)

Shower energy is given by:

W = the average energy needed for creation

of an electron-ion pair.

0.5

W = .6

23 + −0.3

R = the electron-ion

recombination factor.

R = 0.640 ± 0.013

e (t i-t /τe) 0 = correction for drift electron

finite life time τ e

Qi = the hit area.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Invariant mass and energy ( data from Test Run in Pavia ).

Final sample.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Pulls

In the case of reliable errors the

distribution of Pull shoud be

normal with RMS equal to unity.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


MC simulation of π 0 production

from hadronic interactions

Three samples of π 0 were generated:

The evident increase in RMS is mainly due to the event

1. decays at rest.

crowded environment, which augments

2. Σ + → π 0 + p with subsequent π 0 the difficulty of the

decays.

event interpretation because of the higher energy

3. π 0 decays observed in interactions of π - mesons with

and Argon the consequent nuclei at presence 2 GeV incident of otherenergy.

reaction products.

RMS of the invariant mass distribution are equal to:

1. ( 7.4 ± 1.3 ) MeV

2. ( 10.7 ± 2.8 ) MeV

3. ( 25.8 ± 4.7 ) MeV

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Simulation of π 0 production in ν

interactions

In our work we have shown that the results of the analysis of real and

simulated events with π 0 production are consistent.

Therefore, the same methode of generation, measurement and

reconstruction was applied to simulated neutrino-induced

induced pion production to

check the potentiality of the liquid argon technique in this respect.

Neutrino interactions at energies: 1, 1.5, 2, 2.5, 5, 17 GeV.

The fraction of pions from secondary vertexes grows with the energy of the

incident neutrino and already at the energy of 5 GeV is compatible to that of

primary pions.

In the ICARUS T600 LAr TPC good spatial resolution allows to distinguish

the primary vertex from the secondary one, which is not always the case in

the water detector or in the sandwich-like detector configuration.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Neutral curent ν µ events with π 0 production as a

background to ν e interaction.


When can we misidentify π 0

with electron

– one photon from the decay is

lost when it is emitted with too

small energy and the other

photon either produces the

Compton photon close to the

primary vertex, or the conversion

pair is produced close to the

primary vertex.

the two photon showers overlap

and the Compton scattering

occurs close to the primary

vertex.

As you can see those fractions are not large.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


M from γγ neutrino interactions (MC)

η→2γ

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Conclusions

A sample of about 200 events with at least of two

photons pointing to the interaction vertex has been

selected from the data collected during the test run of

the ICARUS detector.

Those data was used as a test of the energy

resolution as a function of photon shower energy.

The invariant mass of the photon pairs from a final

sample was reconstructed.

– m = 127 ± 3.0 (stat) ± 4.0 (sys) MeV/c 2

confirm that the π 0 s are the main source of photon pairs.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Conclusions

The width of the distributions of invariant mass for

simulated events was similar within errors, confirming

the validity of the shower energy and shower direction

reconstruction methods.

It was found that in the photon energy range from 50

to 5000 MeV the electromagnetic showers energy

resolution ∆E/E can be approximated by a formula

∆E/E = P1/√E + P2 with the parameters P1 = (0.33

±0.03) √MeV and P2 = 0.012 ± 0.002.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).


Thank you.

Detection and reconstruction of π 0

mesons in the ICARUS detector.

Tomasz Palczewski. I.P.J (SINS).

More magazines by this user
Similar magazines