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PPT – Probing the Universe for Gravitational Waves: A First Glimpse with LIGO Barry C. Barish Caltech Penn State 10-April-03 PowerPoint presentation | free to download - id: 15cbf7-ZDc1Z

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Probing the Universe for Gravitational Waves A

First Glimpse with LIGOBarry C.

BarishCaltechPenn State10-April-03

"Colliding Black Holes"CreditNational Center

for Supercomputing Applications (NCSA)

LIGO-G030020-00-M

A Conceptual Problem is solved !

Newtons Theory instantaneous action at a

distance

Gmn 8pTmn

Einsteins Theory information carried by

gravitational radiation at the speed of light

Einsteins Theory of Gravitation

- a necessary consequence of Special Relativity

with its finite speed for information transfer - gravitational waves come from the acceleration

of masses and propagate away from their sources

as a space-time warpage at the speed of light

gravitational radiation binary inspiral of

compact objects

Einsteins Theory of Gravitation gravitational

waves

- Using Minkowski metric, the information about

space-time curvature is contained in the metric

as an added term, hmn. In the weak field limit,

the equation can be described with linear

equations. If the choice of gauge is the

transverse traceless gauge the formulation

becomes a familiar wave equation

- The strain hmn takes the form of a plane wave

propagating at the speed of light (c).

- Since gravity is spin 2, the waves have two

components, but rotated by 450 instead of 900

from each other.

Detecting Gravitational Waves Laboratory

Experiment

a la Hertz

Experimental Generation and Detection of

Gravitational Waves

gedanken experiment

The evidence for gravitational waves

- Neutron binary system
- separation 106 miles
- m1 1.4m?
- m2 1.36m?
- e 0.617

- Hulse Taylor

17 / sec

- Prediction
- from
- general relativity
- spiral in by 3 mm/orbit
- rate of change orbital
- period

period 8 hr

- PSR 1913 16
- Timing of pulsars

Indirectdetection of gravitational waves

PSR 191316

Direct Detection

Gravitational Wave Astrophysical Source

Terrestrial detectors LIGO, TAMA, Virgo,AIGO

Detectors in space LISA

Detection in space

The Laser Interferometer Space Antenna LISA

- Center of the triangle formation is in the

ecliptic plane - 1 AU from the Sun and 20 degrees behind the

Earth.

Detection on Earth

simultaneously detect signal

LIGO

Virgo

GEO

TAMA

AIGO

decompose the polarization of gravitational waves

detection confidence

locate the sources

Frequency range of astrophysics sources

Audio band

- Gravitational Waves over 8 orders of magnitude
- Terrestrial detectors and space detectors

Space

Terrestrial

Frequency range of astronomy

- EM waves studied over 16 orders of magnitude
- Ultra Low Frequency radio waves to high energy

gamma rays

A New Window on the Universe

Gravitational Waves will provide a new way to

view the dynamics of the Universe

Astrophysical Sourcessignatures

- Compact binary inspiral chirps
- NS-NS waveforms are well described
- BH-BH need better waveforms
- search technique matched templates
- Supernovae / GRBs bursts
- burst signals in coincidence with signals in

electromagnetic radiation - prompt alarm ( one hour) with neutrino detectors
- Pulsars in our galaxy periodic
- search for observed neutron stars (frequency,

doppler shift) - all sky search (computing challenge)
- r-modes
- Cosmological Signals stochastic background

The effect

Leonardo da Vincis Vitruvian man

- Stretch and squash in perpendicular directions

at the frequency of the gravitational waves

Detecting a passing wave .

Free masses

Detecting a passing wave .

Interferometer

The challenge .

I have greatly exaggerated the effect!! If the

Vitruvian man was 4.5 light years high, he would

grow by only a hairs width

LIGO Interferometer Concept

Interferometer Concept

- Laser used to measure relative lengths of two

orthogonal arms

- Arms in LIGO are 4km
- Measure difference in length to one part in 1021

or 10-18 meters

causing the interference pattern to change at

the photodiode

How Small is 10-18 Meter?

LIGO Organization

The Laboratory Sites

Laser Interferometer Gravitational-wave

Observatory (LIGO)

Hanford Observatory

Livingston Observatory

LIGO Livingston Observatory

LIGO Hanford Observatory

LIGObeam tube

- LIGO beam tube under construction in January 1998
- 65 ft spiral welded sections
- girth welded in portable clean room in the field

1.2 m diameter - 3mm stainless 50 km of weld

NO LEAKS !!

LIGOvacuum equipment

LIGO Optic

- Substrates SiO2
- 25 cm Diameter, 10 cm thick
- Homogeneity lt 5 x 10-7
- Internal mode Qs gt 2 x 106
- Polishing
- Surface uniformity lt 1 nm rms
- Radii of curvature matched lt 3
- Coating
- Scatter lt 50 ppm
- Absorption lt 2 ppm
- Uniformity lt10-3

Core Optics installation and alignment

Laserstabilization

- Deliver pre-stabilized laser light to the 15-m

mode cleaner - Frequency fluctuations
- In-band power fluctuations
- Power fluctuations at 25 MHz

- Provide actuator inputs for further stabilization
- Wideband
- Tidal

10-1 Hz/Hz1/2

10-4 Hz/ Hz1/2

10-7 Hz/ Hz1/2

Prestabalized Laser performance

- gt 20,000 hours continuous operation
- Frequency and lock very robust
- TEM00 power gt 8 watts
- Non-TEM00 power lt 10
- Simplification of beam path outside vacuum

reduces peaks - Broadband spectrum better than specification from

40-200 Hz

LIGO first lock

Y Arm

Laser

X Arm

signal

Watching the Interferometer Lock

X arm

Y arm

Y Arm

Anti-symmetricport

Reflected light

Laser

X Arm

signal

Lock Acquisition

What Limits Sensitivityof Interferometers?

- Seismic noise vibration limit at low

frequencies - Atomic vibrations (Thermal Noise) inside

components limit at mid frequencies - Quantum nature of light (Shot Noise) limits at

high frequencies - Myriad details of the lasers, electronics, etc.,

can make problems above these levels

LIGO Sensitivity Livingston 4km Interferometer

May 01

Jan 03

Detecting Earthquakes

From electronic logbook 2-Jan-02

An earthquake occurred, starting at UTC 1738.

Detecting the Earth Tides Sun and Moon

LIGO Sensitivity Livingston 4km Interferometer

May 01

First Science Run 17 days - Sept 02

Jan 03

Second Science Run 59 days - April 03

In-Lock Data Summary from S1

H1 235 hrs

H2 298 hrs

L1 170 hrs

3X 95.7 hrs

Red lines integrated up time Green

bands (w/ black borders) epochs of lock

- August 23 September 9, 2002 408 hrs (17 days).
- H1 (4km) duty cycle 57.6 Total Locked time

235 hrs - H2 (2km) duty cycle 73.1 Total Locked time

298 hrs - L1 (4km) duty cycle 41.7 Total Locked time

170 hrs - Double coincidences
- L1 H1 duty cycle 28.4 Total coincident

time 116 hrs - L1 H2 duty cycle 32.1 Total coincident

time 131 hrs - H1 H2 duty cycle 46.1 Total coincident

time 188 hrs

Triple Coincidence L1, H1, and H2 duty cycle

23.4 total 95.7 hours

Compact binary collisions chirps

- Neutron Star Neutron Star
- waveforms are well described
- Black Hole Black Hole
- need better waveforms
- Search matched templates

Neutron Star Merger

Simulation and Visualization by Maximilian

Ruffert Hans-Thomas Janka

Searching Technique binary inspiral events

- Use template based matched filtering algorithm
- Template waveforms for non-spinning binaries
- 2.0 post-Newtonian approx.
- D effective distance a phase
- Discrete set of templates labeled by I(m1, m2)
- 1.0 Msun lt m1, m2 lt 3.0 Msun
- 2110 templates
- At most 3 loss in SNR

s(t) (1Mpc/D) x sin(a) hIs (t-t0) cos(a)

hIc (t-t0)

Sensitivityneutron binary inspirals

- Star Population in our Galaxy
- Population includes Milky Way, LMC and SMC
- Neutron star masses in range 1-3 Msun
- LMC and SMC contribute 12 of Milky Way

- Reach for S1 Data
- Inspiral sensitivity
- Livingston ltDgt 176 kpc
- Hanford ltDgt 36 kpc
- Sensitive to inspirals in
- Milky Way, LMC SMC

Loudest Surviving Candidate

- Not NS/NS inspiral event
- 1 Sep 2002, 003833 UTC
- S/N 15.9, c2/dof 2.2
- (m1,m2) (1.3, 1.1) Msun

- What caused this?
- Appears to be saturation of a photodiode

Results of Inspiral Search

- Upper limit
- binary neutron star
- coalescence rate

LIGO S1 Data R lt 160 / yr / MWEG

- Previous observational limits
- Japanese TAMA ? R lt 30,000 / yr / MWEG
- Caltech 40m ? R lt 4,000 / yr /

MWEG - Theoretical prediction R lt 2 x 10-5 / yr

/ MWEG

Gravitational Wave Bursts

- Known phenomena like Supernovae GRBs
- Coincidence with observed electromagnetic

observations. - No close supernovae occured during the first

science run - Second science run We are analyzing the recent

very bright and close GRB030329 NO RESULT YET - Unknown phenomena emission of short transients of

gravitational radiation of unknown waveform (e.g.

black hole mergers). - Search methods
- Time domain algorithm (SLOPE) identifies rapid

increase in amplitude of a filtered time series

(threshold on slope). - Time-Frequency domain algorithm (TFCLUSTERS)

identifies regions in the time-frequency plane

with excess power

Unmodelled Bursts

search for waveforms from sources for which we

cannot currently make an accurate prediction of

the waveform shape.

GOAL

METHODS

Time-domain high pass filter

Raw Data

8Hz

0.125s

Determination of Efficiency

Efficiency measured for tfclusters algorithm

To measure our efficiency, we must pick a

waveform.

1ms Gaussian burst

Upper Limit 1ms gaussian bursts

Result is derived using TFCLUSTERS algorithm

- Upper limit in strain compared to earlier

(cryogenic bar) results - IGEC 2001 combined bar upper limit lt 2 events

per day having h1x10-20 per Hz of burst

bandwidth. For a 1kHz bandwidth, limit is lt 2

events/day at h1x10-17 - Astone et al. (2002), report a one sigma

excess of one event per day at strain level of h

2x10-18

90 confidence

Spinning Neutron Stars periodic

Maximum gravitational wave luminosity of known

pulsars

- An afterlife of stars

Directed searches

NO DETECTION EXPECTED at present sensitivities

Two Search Methods

- Frequency domain
- Best suited for large parameter space searches
- Maximum likelihood detection method frequentist

approach

- Time domain
- Best suited to target

known objects, even if phase evolution is

complicated - Bayesian approach

First science run --- use both pipelines for the

same search for cross-checking and validation

The Data time behavior

days

days

days

days

The Data frequency behavior

Hz

Hz

Hz

Hz

PSR J19392134

- Frequency domain
- Fourier Transforms of time series
- Detection statistic F , maximum likelihood

ratio wrt unknown parameters - use signal injections to measure Fs pdf
- use frequentists approach to derive upper limit

Injected signal in LLO h 2.83 x 10-22

Measured F statistic

PSR J19392134

Data

Injected signals in GEO h1.5, 2.0, 2.5, 3.0 x

10-21

- Time domain
- time series is heterodyned
- noise is estimated
- Bayesian approach in parameter estimation

express result in terms of posterior pdf for

parameters of interest

95

h 2.1 x 10-21

Results Periodic Sources J19392134

- No evidence of continuous wave emission from PSR

J19392134. - Summary of 95 upper limits on h

IFO Frequentist FDS Bayesian TDS GEO

(1.94?0.12)x10-21 (2.1 ?0.1)x10-21 LLO

(2.83?0.31)x10-22 (1.4 ?0.1)x10-22

LHO-2K (4.71?0.50)x10-22 (2.2

?0.2)x10-22 LHO-4K (6.42?0.72)x10-22

(2.7 ?0.3)x10-22 Joint -

(1.0 ?0.1)x10-22

- holt1.0x10-22 constrains ellipticity lt 7.5x10-5

(M1.4Msun, r10km, R3.6kpc) - Previous results for PSR J19392134 ho lt 10-20

(Glasgow, Hough et al., 1983), ho lt

3.1(1.5)x10-17 (Caltech, Hereld, 1983).

Early Universe correlated noise

Murmurs from the Big Bang

Cosmic Microwave background

WMAP 2003

Stochastic Backgroundno observed correlations

- Strength specified by ratio of energy density in

GWs to total energy density needed to close the

universe - Detect by cross-correlating output of two GW

detectors

First LIGO Science Data

Hanford - Livingston

Hanford - Hanford

Stochastic Background sensitivities and theory

E7

results

projected

S1

S2

LIGO

Adv LIGO

Advanced LIGOimproved subsystems

Multiple Suspensions

- Active Seismic

Sapphire Optics

Higher Power Laser

Advanced LIGO2007

- Enhanced Systems
- laser
- suspension
- seismic isolation
- test mass

Improvement factor in rate 104

narrow band optical configuration

Probing the Universe with LIGO a first glimpse

- LIGO commissioning is well underway
- Good progress toward design sensitivity
- Science Running is beginning
- Initial results from our first LIGO data run
- Our Plan
- Improved data run is underway
- Our goal is to obtain one year of integrated data

at design sensitivity before the end of 2006 - Advanced interferometer with dramatically

improved sensitivity 2007 - LIGO should be detecting gravitational waves

within the next decade !

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