New data analysis for AURIGA

Lucio Baggio

Italy, INFN and University of Trento

AURIGAAURIGA

The (new) AURIGA data analysis

Since 2001 the AURIGA data analysis for burst search have been rewritten from scratch (G. Vedovato), in parallel with major upgrades taking place on the detector

The main goals and specifications to achieve were:

• Be flexible and modular, with easy adaptation to new algorithms

• Adopt the VIRGO/LIGO frame format for data storage and exchange

new data acquisition system

open source project, C++

widespread use of supported and well known libraries:

ROOT (http://root.cern.ch)VEGA (http://wwwlapp.in2p3.fr/virgo/vega)

FrameLibs (http://wwwlapp.in2p3.fr/virgo/FrameL) FFTW (http://www.fftw.org) LAL (http://www.lsc-group.phys.uwm.edu/lal)

MKFilter (http://www-users.cs.york.ac.uk/~fisher/mkfilter)

• And, develop new algorithms, indeed! (highlight: Karhunen-Loeve decomposition)

• Recycle software (and be recyclable)

Overview (see poster)

The data analysis of raw or simulated data for burst search divides in a series of tasks

DQ

MTC

EVTFW

DAQS

DAQ FME

1. Estimate parameters of the analytic part of the noise model (Full Model Estimate, FME)

2. Remove noise correlation (Full Whitening, FW)

3. Perform a matched template filtering and event search (EVT)

4. Define epoch vetoes based on Gaussianity monitors (Data Quality, DQ)

5. Compute distribution of errors in event parameters estimators (Monte Carlo, MTC)

Event search (1)

Within this task the whitened data are optimally filtered in the frequency domain for a specified template signal.

Then, the time series is passed to the event search algorithm

event searchoptimal filter& coarse interpolation

EVT

max-hold

fine interpolation

raw data

noise model

template bank

see poster

Event search (2)

•The time series is downsampled to a convenient sampling rate

•The absolute value of the downsampled time series is searched for the local maxima (max-hold algorithm with a given dead time), and when it is above a proper threshold a candidate event trigger is issued

•For each event trigger, the exact time of arrival and amplitude are computed after fine interpolation of the samples, along with sum of squared residuals (for 2-test), Karhunen-Loeve components, etc

time

Event statistics from Monte Carlo (MTC)

MTC

coarse interpolation

Phase 1

Phase 2

template bank

event search

template injection

whitened data

The goal of this task is to estimate numerically the distributions of time of arrival and amplitude errors, for a bank of filter templates, possibly not exactly matched with the input signal.

Software signal injection takes place in the time domain, by adding a chosen template (properly rescaled in amplitude and time-shifted) to the actually measured white noise of the system. Template injection and search is automatically cycled for specified time and amplitude increments, and can be repeated for indipendently specified signal and filter templates.

see poster

average power f·f = k k

-4 hk2 + …

Karhunen-Loeve Decomposition (1)

signal h +noise (Sh)

optimally filtered amplitudeWiener filter with template

-filteredtemplateless KLD suboptimal energy estimate

-filter: F() = Sh()-1 R-1 (inverse autocorrelation matrix) (f-2 = 1)

Karhunen-Loeve eigenfunctions {k}k=1,…,N Rk = k2 k (kk

-2 = 1)

Define: AKL2 = f·Rf = k k

-2 hk2 + k k

-2nk2 + 2 k k

-2 hknk

without signal: AKL ~ Chi(N)

with signal: AKL= (kk-2hk

2)1/2 + k k-2hknk (ij

-2hj2)-1/2 + O2(n/AKL)

2)(

)(|| 2 d

S

HSNRh= Gauss(0,1)

input: khkk + knkk nk ~Gauss(0,k)signal noise

f = R-1 h = k k-2 hkk + kk

-2nk k

http://www.ligo.caltech.edu/docs/P/P010019-01.pdf

Karhunen-Loeve Decomposition (2)

SNR

prob

abili

ty d

ensi

ty

amplitudeSNRh

linear filter with mismatched template Karhunen-Loeve decomposition

• Pros: The signal-to-noise ratio through KLD equals the maximum one achievable with template knowledge

• Cons: increased tail of fake events

definition of event baricenter?

Summary

• Brand new code, rewritten from scratch in C++, running on standalone PCs

• Integrated ARMA noise simulator, generating stationary or time varying correlated gaussian noise, possibly polluted with power line harmonics, periodic signals and bursts.

• Adaptive parametric noise model estimate

• Support for non-parametric frequency-dependent calibration function

• Support for template bank search.

• Embedded Monte Carlo and tools for measuring efficency.

To do:

• Re-implementation of data conditioning, study for optimization of the (still) empirical vetoing rules. Tuning on forthcoming sensitivity and stability of the detector.

• Make the analysis more robust with respect to heavy data corruption by spectral lines and transient disturbances.

• Training on templateless search, tuning of time interval size for K-L decomposition comparison with time-frequency methods

• Intensify collaboration with other research groups, in order to share algorithms

see also poster

Pararametric noise model estimator

raw data

SDFT

FMEPhase 1 Phase 2

Periodograms quality check

Iterative fit and data conditioning

FFT1

FFT2

FFT3

FFTn

Time series smoothing

Outlier removal

Phase 1

Periodograms quality check

Iterative fit and data conditioning

FFT1

FFT2

FFT3

FFTn