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PERFORMANCE OF THE MACRO LIMITED STREAMER TUBES IN DRIFT MODE FOR MEASUREMENTS OF MUON ENERGY PowerPoint PPT Presentation


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7 International Conference on. th. ADVANCED TECHNOLOGY AND PARTICLE PHYSICS. Villa Olmo, Como, 15-19/10/2001. PERFORMANCE OF THE MACRO LIMITED STREAMER TUBES IN DRIFT MODE FOR MEASUREMENTS OF MUON ENERGY. M. Giorgini for the MACRO Collaboration.

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PERFORMANCE OF THE MACRO LIMITED STREAMER TUBES IN DRIFT MODE FOR MEASUREMENTS OF MUON ENERGY

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Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

7 International Conference on

th

ADVANCED TECHNOLOGY AND PARTICLE PHYSICS

Villa Olmo, Como, 15-19/10/2001

PERFORMANCE OF THE MACRO LIMITED STREAMER TUBES IN DRIFT MODE FOR MEASUREMENTS OF MUON ENERGY

M. Giorgini for the MACRO Collaboration

Goal : energy estimate of upgoing muons with a

Multiple Coulomb Scattering (MCS) analysis

Experimental procedure

  • Use of the MACRO limited streamer tubes in drift mode

- Check of the electronics with 2 dedicated “test beam”

- Study of drift velocity in He/n-pentane mixture

  • Use of a neural network (NN) to estimate the muon energy

  • event by event

Conclusions


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

SECTION OF THE MACRO DETECTOR

m

nm

7 rock absorbers

3 liquid scintillators

14 horizontal planes of limited streamer tubes

filled with a mixture of He (73%) / n-pentane (27%)

The upthroughgoing muons are induced by neutrino

interaction in the rock below the detector

The oscillation probability is a function of En

P(nm nt) = sin22Q sin2(1.27 Dm2 L/En)

It is IMPORTANT to estimate the induced-muon energy


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

MACRO is not equipped with a magnet:

the ONLY way to estimate muon energy is by

the Multiple Coulomb Scattering (MCS) in the

absorbers

The r.m.s. of the lateral displacement of a muon

crossing a depth X of material is :

X X

sYa

pm

X0

pm = muon momentum

X0 = radiation length of the material

~

The saturation occurs when sY = space resolution

of the detector

For MACRO: sY = 10cm/Em(GeV)

The space resolution of the tracking system is ~ 1 cm

corresponding to Em ~ 10 GeV, not enough to study

neutrino oscillations with parameters

~

Dm2 ~ 10-3 eV2 and sin2 2Q = 1


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

THE MACRO LIMITED STREAMER TUBES

Cross section : 3X3 cm2

Length : 1200 cm

About 5600 chambers and ~ 50000 wires

Mixture : He(73%) / n-pentane(27%)

MACRO is non equipped with a TDC system

Time informations can be obtained from theQTP

(Charge and Time Processor) System

(designed for the search for slow magnetic monopoles)

ADC/TDC system with a 640 ms memory

Frequency of the clock : 6.6 MHz

TDC bin size : Dt =150 ns

Ultimate space resolution :s =Vdrift. Dt/ 12 ~2mm


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

THE MACRO CERN PS-T9 “TEST BEAM”

Main goals :

MAIN GOALS :

Study of the QTP-TDC linearity : comparison

of QTP-TDC (150 ns/div) and standard TDC

Lecroy 2228A (250 ps/div)

Study of drift velocity in He / n-pentane mixture

Test of the software used for muon tracking

Absolute calibration of energy reconstructed

by multiple scattering


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

3 liquid scintillators

7 rock absorbers

beam

4 streamer tubes

10 streamer tubes

(MACRO lower part)

(MACRO attico)

60 RUNS with 2 GeV < Em < 12 GeV

(~ 105 muons)

The analog output of each chamber is sent to a

QTP channel

The digital output is sent to a TDC Lecroy

Trigger : fast coincidence of S1,S2,S3 scintillators

HV : 4050 V


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

STUDY OF QTP-TDCLINEARITY

Comparison between the response of the MACRO

QTP system and standard TDC’s ( Lecroy )

The TDC-QTP response is linear within 10 %


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

m

r = 50 mm

wire

r

STUDY OF DRIFT VELOCITY IN He- n-PENTANE

50 mm < r < 1.5 cm

dN/dt = dN/dr * dr/dt

  • 3cm

vdrift

constant


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

COMPARISONGARFIELD MC – REAL DATA

Good agreement between MC and real data


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

SPACE RESOLUTION(RESIDUALS DISTRIBUTION)

1 dedicated run with rock absorbers away:

QTP-TDC(150ns/div)s~ 2 mm

Standard Lecroy TDC (250 ps/div) s~ 500 mm

2 mm is our best resolution !

In MACRO the space resolution is expected to be

spoiled by d rays produced in the rock absorbers

and by gas mixture variation.


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

RESULTS OF THE CERN PS-T9 “TEST BEAM”

The QTP electronics can be successfully used

to operate the streamer tubes in drift mode

The QTP-TDC response is linear within 10%

The drift velocity in He/n-pentane mixture is

in good agreement with GARFIELD MC

The software is adequate to perform a good

muon track fit

The space resolution of the MACRO streamer

tubes in drift mode is ~ 2 mm


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

STUDY OF THE MACRO SPACE RESOLUTION

Analysis of the downgoing muon (<Em> ~ 300

GeV) tracks with the standard tracking (no

QTP)

Selection of the hits with a single fired tube

For each hit, the corresponding TDC value is

multiplied by the Vdrift measured at the “test

beam”, obtaining the drift radius

The track is reconstructed as the best fit of the

drift circles


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

MACRO RESIDUALS DISTRIBUTION

Without QTP (streamers in digital mode) s~ 1 cm

With QTP s~ 3 mm

Improvement of the space resolution of a factor 3.5 !


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

VARIABLES SENSITIVE TO MS

Average abs(residual)

Maximum residual

of residuals distribution

s

Difference of residuals relative to the 3

more distant tubes

Slope and intercept of ‘progressive fit’ (see below)

Dx

100 GeV

Dx =

1

2

3

Np

4

1 GeV

Dx

Np

5

6

7

8

9

Np

10

Np = progressive number of s.t.

of MACRO lower part

Absorber


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

USE OF A NEURAL NETWORK (NN)TO

SEPARATE SAMPLES OF DIFFERENT ENERGIES

Training:

Fixed energy

Different zenith angle

Average residuals

Max residuals

s of residuals distribution

Slope of ‘progressive fit’

Neural Network

Intercept of ‘progressive fit’

Diff. of residuals for the 3

more distant tubes

0. < Output < 1.

This procedure allows to estimate event by event

the energy of upgoing muons


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

OUTPUT OF THE NEURAL NETWORK

The response is linear with event energy up to

Em ~ 40 GeV


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

The CERN PS-T9 “test beam” allows to calibrate

the NN output ONLY up to Em=12 GeV

A second “test beam” was performed at the

SPS-X7 with 15 GeV < Em < 100 GeV

The comparison data-MC shows a good

agreement in the Em range from 2 to 100 GeV


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

RECONSTRUCTION OF THE MUON ENERGY

INVERTING THE CURVE JUST SHOWN

FOR 4 DIFFERENT Em VALUES


Performance of the macro limited streamer tubes in drift mode for measurements of muon energy

CONCLUSIONS

The MACRO streamer tube system can be used

in drift mode for measurements of muon energy

The QTP system allows to improve the MACRO

space resolution of a factor 3.5

from s = 1cm to s = 3mm

~

~

The NN approach allows to estimate the muon

energy event by event

The output of the NN increases with the muon

energy up to Em ~ 40 GeV

The test beam data are in agreement with the MC

expectations with 1s error

This method can be applied to estimate the energy

of neutrino-induced upgoing muons in MACRO

to study the neutrino oscillations hypothesis


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