Gravitational Waves: Resonant Mass Detectors and Next Generation Interferometers

1. Gravitational Waves (Working group 6)resonant mass detectors:Visco current generation terrestrial interferometers: Frolov, Bradynext generation terrestrial interferometers:Adhikari, Owen“science fiction” terrestrial interferometers: MavalvalaBruce Allen, UWM

2. Gravitational waves Couple to mass 4-current Produced by coherent motions of high density or curvature Wavelengths > source size, like sound waves (no pictures) Propagate through everything, so you see dense centers Electromagnetic waves Couple to electric 4-current Incoherent superposition of many microscopic emitters Wavelengths  source size, can make pictures Stopped by matter, so “beauty is skin deep” Gravitational waves:How are they different? WG6 summary, TEV II

3. Science Goals • Direct verification of two dramatic predictions of Einstein’s general relativity: gravitational waves & black holes • Physics & Astronomy • Detailed tests of properties of gravitational waves including speed, polarization, graviton mass, ..... • Probe strong field gravity near black holes & in early universe • Probe the neutron star equation of state • Performing routine astronomical observations • A new window on the Universe WG6 summary, TEV II

4. GW Sources 50-1000 Hz • Compact binary inspiral: “chirp” • Supernovae / Mergers: “burst” • Spinning NS: “continuous” • Cosmic Background: “stochastic” WG6 summary, TEV II

5. Present performance of resonant mass detectors Massimo Visco INAF –IFSI Roma INFN – Sez. Roma Tor Vergata WG6 summary, TEV II

6. International Gravitational Events Collaboration ALLEGRO– AURIGA – ROG (EXPLORER-NAUTILUS) • The “oldest” resonant detector EXPLORER started operations about 16 years ago. • This kind of detector has reached a high level of realibilty. • The duty factor is greater than 90% .

7. A DIRECTIONAL 4-ANTENNAE OBSERVATORY • The four antennas are sensitive to the same region of the sky WG6 summary, TEV II

8. SENSITIVITY OF PRESENT DETECTORS WG6 summary, TEV II

9. TRIPLE COINCIDENCE DISTRIBUTION AU-EX-NA (PRELIMINARY) NO DETECTIONS WG6 summary, TEV II

10. 2012 - 2018 NETWORK - slide from INFN roadmap WG6 summary, TEV II

11. Status of LIGO Valera Frolov LIGO Lab WG6 summary, TEV II

12. Hanford, WA (H1 4km, H2 2km) Livingston, LA (L1 4km) LIGO Observatories • Interferometers are aligned to be as close to parallel to each other as possible • Observing signals in coincidenceincreases the detection confidence • Determine source location on the sky, propagation speed and polarization of the gravity wave WG6 summary, TEV II

13. 2 2 2 2 4 4 4 4 1 1 1 1 3 3 3 3 10-21 10-22 Runs S1 S2 S3 S4 S5 Science First Science Data 2006 Time Line 1999 2000 2001 2002 2003 2004 2005 2006 2 4 2 4 4 1 3 1 3 2 4 3 1 3 Inauguration HEPI at LLO First Lock Full Lock all IFO Now 4K strain noise at 150 Hz [Hz-1/2] 10-17 10-18 10-20 WG6 summary, TEV II

14. NS-NS Inspiral Range Improvement Time progression since the start of S5 Design Goal Commissioning breaks Stuck ITMY optic at LLO WG6 summary, TEV II

15. ~ 61% Triple Coincidence Accumulation 100% ~ 45% Expect to collect one year of triple coincidence data by summer-fall 2007 WG6 summary, TEV II

16. LIGO Observational Results Patrick Brady U. Wisconsin - Milwaukee WG6 summary, TEV II

17. Bursts • Supernovae: Neutron star birth, tumbling and/or convection • Cosmic strings, black hole mergers, ..... • Coincident EM observations • Surprises! WG6 summary, TEV II

18. Detection Efficiency Central Frequency • Evaluate efficiency by adding simulated GW bursts to the data. • Example waveform S4 Detection Efficiency • S5 sensitivity: minimum detectable in band energy in GW • EGW > 1 M⊙ @ 75 Mpc • EGW > 0.05 M⊙ @ 15 Mpc (Virgo cluster) WG6 summary, TEV II

19. Upper Limits • No GW bursts detected through S4 • set limit on rate vs signal strength. S1 Excluded 90% CL Lower rate limits from longer observation times S2 Rate Limit (events/day) S4 projected S5 projected Lower amplitude limits from lower detector noise WG6 summary, TEV II

20. Stochastic Background • Big bang & early universe • Background of gravitational wave bursts • Unresolved background of contemporary sources WMAP WG6 summary, TEV II

21. H0 = 72 km/s/Mpc CMB Predictions and Limits LIGO S1: Ω0< 44 PRD 69 122004 (2004) 0 LIGO S3: Ω0< 8.4x10-4 PRL 95 221101 (2005) -2 BB Nucleo- synthesis Pulsar Timing -4 Cosmic strings (0) -6 Initial LIGO, 1 yr data Expected Sensitivity ~4x10-6 -8 Log Pre-big bang model -10 Advanced LIGO, 1 yr data Expected Sensitivity ~ 1x10-9 EW or SUSY Phase transition -12 Inflation -14 Cyclic model Slow-roll -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 -18 10 WG6 summary, TEV II Log (f [Hz])

22. Compact Binaries • Black holes & neutron stars • Inspiral and merger • Probe internal structure, populations, & spacetime geometry WG6 summary, TEV II

23. S5 Search binary neutron star horizon distance • 3 months of S5 analyzed • Horizon distance versus mass for BBH Average over run 130Mpc 1 sigma variation binary black hole horizon distance WG6 summary, TEV II Image: R. Powell

24. Astrophysical sources of gravitational waves • Spinning neutron stars • Isolated neutron stars with mountains or wobbles • Low-mass x-ray binaries • Probe internal structure and populations WG6 summary, TEV II

25. Known pulsarsS5 preliminary • 32 known isolated, 44 in binaries, 30 in globular clusters Lowest ellipticity upper limit: PSR J2124-3358 (fgw = 405.6Hz, r = 0.25kpc) ellipticity = 4.0x10-7 Gravitational-wave amplitude ~2x10-25 Frequency (Hz) WG6 summary, TEV II

26. To participate, sign up at http://www.physics2005.org Einstein@Home • Public distributed computing project • All-sky, all-frequency search is computationally limited • S3 results: • No evidence of pulsars • S4 search • Post-processing underway WG6 summary, TEV II

27. Next Generation Interferometers Rana Adhikari Caltech WG6 summary, TEV II

28. The next several years 4Q ‘06 4Q ‘07 4Q ‘08 4Q ‘09 4Q ‘10 4Q ‘05 Adv LIGO S5 ~2 years S6 • Between now and AdvLIGO, there is some time to improve… • ~Few years of hardware improvements + 1 ½ year of observations. • Factor of ~2.5 in noise, factor of ~10 in event rate. • 3-6 interferometers running in coincidence ! WG6 summary, TEV II

29. Increased Power + Enhanced Readout Lower Thermal Noise Estimate WG6 summary, TEV II

30. Advanced LIGO Design Features ACTIVE SEISMIC ISOLATION FUSED SILICA, MULTIPLE PENDULUM SUSPENSION 40 KG FUSED SILICA TEST MASSES 180 W LASER,MODULATION SYSTEM PRM Power Recycling Mirror BS Beam Splitter ITM Input Test Mass ETM End Test Mass SRM Signal Recycling Mirror PD Photodiode WG6 summary, TEV II

31. Advanced LIGO WG6 summary, TEV II

32. What can gravitational waves tell us about neutron stars? Ben Owen PSU WG6 summary, TEV II

33. Periodic signals:Pulsar emission mechanism • Pulse profiles in different EM bands illuminate mechanism • Profiles show (phase) timing noise, mostly in young pulsars • GW won’t show interesting pulse profiles (only lowest harmonic detectable) • Will be able to test if GW signal has timing noise or not • Tells us how magnetosphere is coupled to dense interior (Does B-field structure go all the way in? Just crust? …) WG6 summary, TEV II

34. Periodic signals:How solid is a neutron star? • NS definitely have (thin) solid crust (known from pulsar glitches) • Normal nuclear crusts can only produce ellipticity  < few  10-7 • If “?” is solid quark matter, whole star could be solid,  < few  10-4 • If “?” is quark-baryon mixture or meson condensate, half of core could be solid,  < 10-5 • High ellipticity measurement means exotic state of matter • Low ellipticity is inconclusive: strain, buried B-field… WG6 summary, TEV II

35. Burst signals:Supernova core collapse • Burst from collapse and bounce • Poorly modeled: different groups predict different waveforms, agree that there is no supernova explosion…. • Long GRBs: knowing time & location helps GW searches • GRB/GW/neutrino relative delays could shed light on explosion mechanism • If GW &  signals are both short, result is a black hole WG6 summary, TEV II

36. Path to sub-quantum-noise limited gravitational wave interferometers Nergis Mavalvala MIT WG6 summary, TEV II

37. Optical Noise • Shot Noise • Uncertainty in number of photons detected a • Higher circulating power Pbsa low optical losses • Frequency dependence a light (GW signal) storage time in the interferometer • Radiation Pressure Noise • Photons impart momentum to cavity mirrorsFluctuations in number of photons a • Lower power, Pbs • Frequency dependence a response of mass to forces • Optimal input power depends on frequency WG6 summary, TEV II

38. Quantum LIGO I Ad LIGO Test mass thermal Suspension thermal Seismic A Quantum Limited Interferometer Input laser power > 100 W Circulating power > 0.5 MW Mirror mass 40 kg WG6 summary, TEV II

39. Consider GW signal in the phase quadrature Not true for all interferometer configurations Detuned signal recycled interferometer  GW signal in both quadratures Orient squeezed state to reduce noise in phase quadrature X- X- X- X+ X- X+ X+ X+ Squeezed input vacuum state in Michelson Interferometer Laser WG6 summary, TEV II

40. Squeezed vacuum states for GW detectors • Requirements • Squeezing at low frequencies (within GW band) • Frequency-dependent squeeze angle • Increased levels of squeezing • Long-term stable operation • Generation methods • Non-linear optical media (c(2) and c(3) non-linearites) crystal-based squeezing • Radiation pressure effects in interferometers ponderomotive squeezing WG6 summary, TEV II

41. Squeezed Vacuum WG6 summary, TEV II

42. Noise budget WG6 summary, TEV II

43. Conclusions • Resonant bar detectors are operating in a stable mode but at low sensitivity compared with… • LIGO is currently carrying out a science run at design sensitivity. • Searches for all major categories of sources are underway and will at least set upper limits. • Detections are possible! • Enhancements in ~ 3 years will increase the reach by a factor of 3 • An upgrade (Advanced LIGO) is planned early next decade • Detections are ‘guaranteed’ • Quantum non-demolition techniques needed to beat quantum limits (squeezed light) WG6 summary, TEV II