Gravitational Waves (Working group 6) resonant mass detectors: Visco current generation terrestrial interferometers: Frolov, Brady next generation terrestrial interferometers: Adhikari, Owen “science fiction” terrestrial interferometers: Mavalvala Bruce Allen, UWM

8/31/06WG6 summary, TEV II2 Gravitational waves: How are they different? 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”

8/31/06WG6 summary, TEV II3 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

8/31/06WG6 summary, TEV II4 Compact binary inspiral:“chirp” Supernovae / Mergers: “burst” Spinning NS:“continuous” Cosmic Background:“stochastic” GW Sources Hz

8/31/06WG6 summary, TEV II5 Present performance of resonant mass detectors Massimo Visco INAF –IFSI Roma INFN – Sez. Roma Tor Vergata

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%.

8/31/06WG6 summary, TEV II7 A DIRECTIONAL 4-ANTENNAE OBSERVATORY The four antennas are sensitive to the same region of the sky

8/31/06WG6 summary, TEV II8 SENSITIVITY OF PRESENT DETECTORS

8/31/06WG6 summary, TEV II9 TRIPLE COINCIDENCE DISTRIBUTION AU-EX-NA (PRELIMINARY) NO DETECTIONS

8/31/06WG6 summary, TEV II NETWORK - slide from INFN roadmap

8/31/06WG6 summary, TEV II11 Status of LIGO Valera Frolov LIGO Lab

8/31/06WG6 summary, TEV II12 LIGO Observatories Livingston, LA (L1 4km) Hanford, WA (H1 4km, H2 2km) - Interferometers are aligned to be as close to parallel to each other as possible - Observing signals in coincidence increases the detection confidence - Determine source location on the sky, propagation speed and polarization of the gravity wave

8/31/06WG6 summary, TEV II13 Time Line Now Inauguration First LockFull Lock all IFO First Science Data S1 S4 Science S2 Runs S3S K strain noiseat 150 Hz [Hz -1/2 ] HEPI at LLO

8/31/06WG6 summary, TEV II14 NS-NS Inspiral Range Improvement Time progression since the start of S5 Design Goal Commissioning breaks Stuck ITMY optic at LLO

8/31/06WG6 summary, TEV II15 Triple Coincidence Accumulation 100% ~ 45% ~ 61% Expect to collect one year of triple coincidence data by summer-fall 2007

8/31/06WG6 summary, TEV II16 LIGO Observational Results Patrick Brady U. Wisconsin - Milwaukee

8/31/06WG6 summary, TEV II17 Bursts Supernovae: Neutron star birth, tumbling and/or convection Cosmic strings, black hole mergers,..... Coincident EM observations Surprises!

8/31/06WG6 summary, TEV II18 Detection Efficiency Evaluate efficiency by adding simulated GW bursts to the data. –Example waveform Central Frequency Detection Efficiency S4 ● S5 sensitivity: minimum detectable in band energy in GW – E GW > 1 M 75 Mpc – E GW > 0.05 M 15 Mpc (Virgo cluster)

8/31/06WG6 summary, TEV II19 S2 S1 S4 projected Excluded 90% CL S5 projected Rate Limit (events/day) Upper Limits No GW bursts detected through S4 –set limit on rate vs signal strength. Lower amplitude limits from lower detector noise Lower rate limits from longer observation times

8/31/06WG6 summary, TEV II20 Stochastic Background Big bang & early universe Background of gravitational wave bursts Unresolved background of contemporary sources WMAP

8/31/06WG6 summary, TEV II Log(f [Hz]) Log (0)(0) Inflation Slow-roll Cosmic strings Pre-big bang model EW or SUSY Phase transition Cyclic model CMB Pulsar Timing BB Nucleo- synthesis Initial LIGO, 1 yr data Expected Sensitivity ~ 4x10 -6 Advanced LIGO, 1 yr data Expected Sensitivity ~ 1x10 -9 LIGO S1: Ω 0 < 44 PRD (2004) LIGO S3: Ω 0 < 8.4x10 -4 PRL (2005) Predictions and Limits H 0 = 72 km/s/Mpc

8/31/06WG6 summary, TEV II22 –Black holes & neutron stars –Inspiral and merger –Probe internal structure, populations, & spacetime geometry Compact Binaries

8/31/06WG6 summary, TEV II23 S5 Search Image: R. Powell binary black hole horizon distance 3 months of S5 analyzed Horizon distance versus mass for BBH Average over run 130Mpc 1 sigma variation binary neutron star horizon distance

8/31/06WG6 summary, TEV II24 Spinning neutron stars –Isolated neutron stars with mountains or wobbles –Low-mass x-ray binaries –Probe internal structure and populations Astrophysical sources of gravitational waves

8/31/06WG6 summary, TEV II25 Known pulsars S5 preliminary 32 known isolated, 44 in binaries, 30 in globular clusters Lowest ellipticity upper limit: PSR J (f gw = 405.6Hz, r = 0.25kpc) ellipticity = 4.0x10 -7 Frequency (Hz) Gravitational-wave amplitude ~2x10 -25

8/31/06WG6 summary, TEV II26 Public distributed computing project All-sky, all-frequency search is computationally limited To participate, sign up at ● S3 results: – No evidence of pulsars ● S4 search – Post-processing underway

8/31/06WG6 summary, TEV II27 Next Generation Interferometers Rana Adhikari Caltech

8/31/06WG6 summary, TEV II28 The next several years  Between now and AdvLIGO, there is some time to improve… 1)~Few years of hardware improvements + 1 ½ year of observations.  Factor of ~2.5 in noise, factor of ~10 in event rate. 1)3-6 interferometers running in coincidence ! S5 S6 4Q ‘05 4Q ‘06 4Q ‘07 4Q ‘08 4Q ‘10 4Q ‘09 Adv LIGO ~2 years

8/31/06WG6 summary, TEV II29 Increased Power + Enhanced Readout Lower Thermal Noise Estimate

8/31/06WG6 summary, TEV II W LASER, MODULATION SYSTEM 40 KG FUSED SILICA TEST MASSES PRM Power Recycling Mirror BS Beam Splitter ITM Input Test Mass ETM End Test Mass SRM Signal Recycling Mirror PD Photodiode Advanced LIGO Design Features ACTIVE SEISMIC ISOLATION FUSED SILICA, MULTIPLE PENDULUM SUSPENSION

8/31/06WG6 summary, TEV II31 Advanced LIGO

8/31/06WG6 summary, TEV II32 What can gravitational waves tell us about neutron stars? Ben Owen PSU

8/31/06WG6 summary, TEV II33 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? …)

8/31/06WG6 summary, TEV II34 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  If “?” is solid quark matter, whole star could be solid,  < few  If “?” is quark-baryon mixture or meson condensate, half of core could be solid,  < High ellipticity measurement means exotic state of matter Low ellipticity is inconclusive: strain, buried B-field…

8/31/06WG6 summary, TEV II35 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

8/31/06WG6 summary, TEV II36 Path to sub-quantum-noise limited gravitational wave interferometers Nergis Mavalvala MIT

8/31/06WG6 summary, TEV II37 Optical Noise Shot Noise –Uncertainty in number of photons detected  –Higher circulating power P bs  low optical losses –Frequency dependence  light (GW signal) storage time in the interferometer Radiation Pressure Noise –Photons impart momentum to cavity mirrors Fluctuations in number of photons  –Lower power, P bs –Frequency dependence  response of mass to forces  Optimal input power depends on frequency

8/31/06WG6 summary, TEV II38 A Quantum Limited Interferometer LIGO I Ad LIGO Seismic Suspension thermal Test mass thermal Quantum Input laser power > 100 W Circulating power > 0.5 MW Mirror mass 40 kg

8/31/06WG6 summary, TEV II39 Squeezed input vacuum state in Michelson Interferometer X+X+ XX X+X+ XX X+X+ XX X+X+ XX 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 Laser

8/31/06WG6 summary, TEV II40 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 (  (2) and  (3) non-linearites) crystal-based squeezing –Radiation pressure effects in interferometers ponderomotive squeezing

8/31/06WG6 summary, TEV II41 Squeezed Vacuum

8/31/06WG6 summary, TEV II42 Noise budget

8/31/06WG6 summary, TEV II43 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)