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Confronting Gravity with LIGO: Status & Prospects

Explore the advancements and challenges of LIGO in detecting gravitational waves, featuring seismic isolation, optical layouts, sensitivity limits, and astrophysical source searches.

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Confronting Gravity with LIGO: Status & Prospects

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  1. Status and Prospects forLIGOBarry C. BarishCaltech17-March-06 Crab Pulsar St Thomas, Virgin Islands

  2. 4 km LIGO Livingston, Louisiana Confronting Gravity - St Thomas

  3. 4 km 2 km LIGO Hanford Washington Confronting Gravity - St Thomas

  4. laser Interferometer optical layout vacuum suspended, seismically isolated test masses mode cleaner 4 km various optics 4-5 W 150-200 W 9-12 kW 10 W 6-7 W 200 mW photodetector GW channel Confronting Gravity - St Thomas

  5. LIGO Beam Tube • Minimal enclosure • Reinforced concrete • No services • 1.2 m diameter - 3mm stainless 50 km of weld • 65 ft spiral welded sections • Girth welded in portable clean room in the field Confronting Gravity - St Thomas

  6. LIGOvacuum equipment Confronting Gravity - St Thomas

  7. Core Opticsinstallation and alignment Confronting Gravity - St Thomas

  8. Surface uniformity < 1 nm rms Scatter < 50 ppm Absorption < 2 ppm ROC matched < 3% Internal mode Q’s > 2 x 106 LIGO Opticsfused silica Caltech data CSIRO data Confronting Gravity - St Thomas

  9. Seismic Noise Quantum Noise Radiation pressure Residual gas scattering "Shot" noise Wavelength & amplitude fluctuations Thermal (Brownian) Noise Interferometer Noise Limits test mass (mirror) LASER Beam splitter photodiode Confronting Gravity - St Thomas

  10. What Limits LIGO Sensitivity? • Seismic noise limits low frequencies • Thermal Noise limits middle frequencies • Quantum nature of light (Shot Noise) limits high frequencies • Technical issues - alignment, electronics, acoustics, etc limit us before we reach these design goals Confronting Gravity - St Thomas

  11. 2 2 2 2 4 4 4 4 1 1 1 1 3 3 3 3 E3 E7 E5 E9 E10 E8 Runs S1 S2 S3 S4 S5 Science First Science Data Commissioning /Running Time Line 2000 2001 2002 2003 2004 2005 2006 1999 2 4 2 4 4 1 3 1 3 2 4 3 1 3 Inauguration First Lock Full Lock all IFO Now 4K strain noise at 150 Hz [Hz-1/2] 10-21 10-22 4x10-23 10-17 10-18 10-20 E2 E11 Engineering Confronting Gravity - St Thomas

  12. Evolution of LIGO Sensitivity • S1: 23 Aug – 9 Sep ‘02 • S2: 14 Feb – 14 Apr ‘03 • S3: 31 Oct ‘03 – 9 Jan ‘04 • S4: 22 Feb – 23 Mar ‘05 • S5: 4 Nov ‘05 - Confronting Gravity - St Thomas

  13. Initial LIGO - Design Sensitivity Confronting Gravity - St Thomas

  14. Rms strain in 100 Hz BW: 0.4x10-21 Sensitivity Entering S5 … Confronting Gravity - St Thomas

  15. S5 Run Plan and Outlook Interferometer duty cycles • Goal is to“collect at least a year’s data of coincident operation at the science goal sensitivity” • Expect S5 to last about 1.5 yrs • S5 is not completely ‘hands-off’ Confronting Gravity - St Thomas

  16. Sensitivity Entering S5 … Hydraulic External Pre-Isolator Confronting Gravity - St Thomas

  17. Locking Problem is Solved Confronting Gravity - St Thomas

  18. What’s after S5? Confronting Gravity - St Thomas

  19. “Modest” Improvements Now – 14 Mpc Then – 30 Mpc Confronting Gravity - St Thomas

  20. Astrophysical Sources • 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 Signal “stochastic background” Confronting Gravity - St Thomas

  21. Our Searches Mass • Several inspiral searches are performed currently: • Primordial black holes binaries (PBHB) • Binary Neutron Stars (BNS) • Binary Black Holes (BBH) • Other searches in progress • Spinning Black Holes • Coincidences with GRB • Black Hole Ringdown • Inspiral-Burst BBH 10 Inspiral-Burst S4 3 Spin is important BNS 1 “High mass ratio” Coming soon PBH 0.1 0.1 1 10 3 Mass Confronting Gravity - St Thomas

  22. Template Bank 2110 templatesSecond-orderpost-Newtonian • Covers desiredregion of massparam space • Calculatedbased on L1noise curve • Templatesplaced formax mismatchof  = 0.03 Confronting Gravity - St Thomas

  23. Binary Neutron Star Search Results (S2) Physical Review D Rate < 47 per year per Milky-Way-like galaxy cumulative number of events signal-to-noise ratio squared Confronting Gravity - St Thomas

  24. Binary Black Hole Search Confronting Gravity - St Thomas

  25. From Limit Setting to Detections Confronting Gravity - St Thomas

  26. Improving Sensitivities Effective distance of L1 improved – S3S4 8 Mpc to 40 Mpc Confronting Gravity - St Thomas

  27. Binary Inspiral Search: LIGO Ranges binary neutron star range binary black hole range Image: R. Powell Confronting Gravity - St Thomas

  28. Astrophysical Sources • 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 Signal “stochastic background” Confronting Gravity - St Thomas

  29. Time-Frequency Plane Search Pure Time-Domain Search ‘TFCLUSTERS’ ‘SLOPE’ frequency time ‘Unmodeled’ Bursts search for waveforms from sources for which we cannot currently make an accurate prediction of the waveform shape. GOAL METHODS ‘Raw Data’ Time-domain high pass filter 8Hz 0.125s Confronting Gravity - St Thomas

  30. Burst Search Results • Blind procedure gives one event candidate • Event immediately found to be correlated with airplane over-flight Confronting Gravity - St Thomas

  31. Burst Source - Upper Limit Confronting Gravity - St Thomas

  32. 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 Signal “stochastic background” Confronting Gravity - St Thomas

  33. Detection of Periodic Sources • Pulsars in our galaxy: “periodic” • search for observed neutron stars • all sky search (computing challenge) • r-modes • Frequency modulation of signal due to Earth’s motion relative to the Solar System Barycenter, intrinsic frequency changes. • Amplitude modulation due to the detector’s antenna pattern. Confronting Gravity - St Thomas

  34. Directed Pulsar Search 28 Radio Sources Confronting Gravity - St Thomas

  35. ALL SKY SEARCH enormous computing challenge Einstein@Home LIGO Pulsar Search using home pc’s BRUCE ALLEN Project Leader Univ of Wisconsin Milwaukee LIGO, UWM, AEI, APS http://einstein.phys.uwm.edu Confronting Gravity - St Thomas

  36. All Sky Search – Final S3 Data NO Events Observed Confronting Gravity - St Thomas

  37. Astrophysical Sources • 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 Signal “stochastic background” Confronting Gravity - St Thomas

  38. Signals from the Early Universe • 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: Overlap Reduction Function Confronting Gravity - St Thomas

  39. Stochastic Background Search (S3) Fraction of Universe’s energy in gravitational waves: (LIGO band) Confronting Gravity - St Thomas

  40. Results – Stochastic Backgrounds Confronting Gravity - St Thomas

  41. Conclusions • LIGO works! • Data Analysis also works for broad range of science goals. Now making transition from limit setting to detection based analysis • Data taking run (S5) to exploit Initial LIGO is well underway and will be complete within ~ 1.5 years • Incremental improvements to follow S5 are being developed. (improve sensitivity ~ x2) • Advanced LIGO fully approved by NSF and NSB and funding planned to commence in 2008. (design will improve sensitivity ~ x20) • R&D on third generation detectors is underway Confronting Gravity - St Thomas

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