Michele Punturo. INFN Perugia and EGO On behalf of the Einstein Telescope Design Study Team

Transcription

1 Michele Punturo INFN Perugia and EGO On behalf of the Einstein Telescope Design Study Team SIF - Bologna

2 3 rd generation: Why? Evolution of the GW detectors (Virgo example): Precision Astronomy Cosmology Proof of the working principle Upper Limit physics Infrastructu re realization and detector assembling 2003 Same Same Same Same Infrastructure infrastructure infrastructure infrastructure ( 20 years old for Virgo, even more for LIGO & GEO600) 2008 enhanced detectors First detection Initial astronomy Detection distance (a.u.) year 2 SIF - Bologna 2010

3 Beyond Advanced Detectors GW detection is expected to occur in the advanced detectors. The 3 rd generation should focus on observational aspects: Astrophysics: Measure in great detail the physical parameters of the stellar bodies composing the binary systems NS-NS, NS-BH, BH-BH Constrain the Equation of State of NS through the measurement of the merging phase of BNS of the NS stellar modes of the gravitational continuous wave emitted by a pulsar NS Contribute to solve the GRB enigma Relativity Compare the numerical relativity model describing the coalescence of intermediate mass black holes Test General Relativity against other gravitation theories Cosmology Measure few cosmological parameters using the GW signal from BNS emitting also an e.m. signal (like GRB) Probe the first instant of the universe and its evolution through the measurement of the GW stochastic background Astro-particle: Contribute to the measure the neutrino mass SIF - Bologna 2010 Constrain the graviton mass measurement 3

4 Target Sensitivity Target sensitivity of a new, 3 rd generation observatory (the Einstein Telescope, ET) is the result of the trade off between several requirements 1. Science Infrastructure targets & site costs 2. Available technologies (detector realization) 3. Infrastructure Science targets & site costs As starting point of our studies we defined two rough requirements: Improvement by a factor 10 the advanced sensitivities Access, as much as possible, to the 1-10Hz frequency range Let see the new possibilities open by such as observatory SIF - Bologna

5 Binary System of massive stars The new possibilities (for BS) of a 3 rd generation GW observatory emerge from these two plots: Cosmological detection distance Frequent high SNR events SIF - Bologna

6 Cosmological detection distance BNS are considered standard sirens (Schutz 1986) because, the amplitude depends only on the Chirp Mass and Luminosity distance D L The masses can be determined by matching the signal with a bank of templates, the position using a network of detectors Hence, through the detection of the BNS gravitational signal, by a network of detectors, it is possible to reconstruct the luminosity distance D L be solved by only using GW detectors But the ambiguity due to the red-shift (red-shifting of the GW frequency affects the reconstructed chirp mass and then the reconstructed D L ) cannot be solved by only using GW detectors D L D L (1+z) ω ω/(1+z) M c M c (1+z) SIF - Bologna

7 Gamma Ray Bursts The red-shift ambiguity requires an E.M. counterpart (GRB) to identify the hosting galaxy and then the red-shift z. Knowing D L and z it is possible to probe the adopted cosmological model: Ω M : total mass density Ω Λ : Dark energy density H 0 : Hubble parameter w: Dark energy equation of state parameter SIF - Bologna

8 Cosmology with ET Cosmology measurements have been proposed combining the Plank CMB measurement with the SNAP* Universe expansion SNe are standard candles, but they need for calibration (Cosmic Distance Ladder) *SNAP: SuperNova Acceleration Probe (JDEM) SIF - Bologna

9 Cosmology with ET Cosmology measurements have been proposed combining the Plank CMB measurement with the SNAP* Universe expansion SNe are standard candles, but they need for calibration (Cosmic Distance Ladder) Thanks to the huge detection range of a 3 rd generation GW observatory and the consequent high event rate (~10 6 evt/year) it has been evaluated for ET (Sathyaprakash 2009) a capability to constrains the cosmological parameters using CMB+GW similar to what is feasible with CMB+SNe, but without any need of Cosmic Distance Ladder *SNAP: SuperNova Acceleration Probe (JDEM) SIF - Bologna

10 High SNR signals Access to all the three phases of the coalescence with high SNR: Early inspiral phase Restricted Post-Newtonian (PN) modeling Plunge phase Full PN (higher harmonics!) approximation Numerical Relativity (NR) templates Equation Of State (EOS) modeling Merger or Ring-down phase Numerical Relativity modeling Quasi-Normal modes simulation & EOS constrains Modeling quality is crucial: Higher harmonics: Improved BNS parameters determination Improved (or simplified sky location of the BNS source) Enrichment of the higher frequency content of the BS emission: Intermediate mass black holes within the detection band of terrestrial detectors ET Full ET ET Restr. Full Restric ted Van Den Broeck and Sengupta (2007) SIF - Bologna

11 ET: Numerical Relativity test bench PN approximations fails close to the plunge/merging phase (large v/c): Hybrid templates Ajith et al. CQG 2007 Ajith et al. PRD 2008 PN PN/NR overlap Santamaria et NR al., PRD2010 But the PN component of the hybrid template it is still source of error, marginally detectable in the advanced detectors (small SNR) but probably dominant in ET Need for better PN approx or longer NR simulation SIF - Bologna

12 Neutron Stars (NS) The EOS of the NS matter is still unknown Why it pulses? It is a neutron or a strange matter star? What is the role of the Magnetic field in a NS? GW could investigate the NS EOS detecting the signal produced in different processes: Coalescence of binaries Full NR simulation of the plunge and merger phase Asteroseismology Detecting the internal modes of the NS Continuous Wave (CW) emission of isolated NS SIF - Bologna

13 Binary NS coalescence The Binary System coalescence has been already described in the previous slides, here the importance of the NR for BNS is stressed BH+BH BH + GWs NS+NS HMNS + GWs +? BH + GWs EOS understanding is crucial Role of the magnetic field? Relativistic magnetized hydrodynamics simulation (L.Rezzolla 2010) Only ET promises to reveal the effects of B SIF - Bologna

14 Continuous Wave The ET improved sensitivity could boost the GW detection from a pulsar SIF - Bologna

15 Continuous Waves in ET Minimal detectable ellipticity ε could approach levels interesting to distinguish the core characteristics Solid cores could sustain ε up to 10-3 ; Crust could sustain ε up to ; 10-2 Minimum detectable ellipticity for known pulsars 10-4 ε SIF - Bologna

16 Supernova Explosions Mechanism of the core-collapse SNe still unclear Shock Revival mechanism(s) after the core bounce TBC GWs generated by a SNe should bring information from the inner massive part of the process and could constrains on the core-collapse mechanisms SIF - Bologna

17 SNe rates with ET Expected rate for SNe is about 1 evt / 20 years in the detection range of initial to advanced detectors Our galaxy & local group To have a decent (0.5 evt/year) event rate about 5 Mpc must be reached ET nominal sensitivity can promise this target Distance [Mpc] [C.D. Ott CQG 2009] SIF - Bologna Distance [Mpc]

18 Neutrinos from SNe SNe detection with a GW detector could bring additional info: The 99% of the erg emitted in the SNe are transported by neutrinos If a simultaneous detection of neutrinos and GW occurs the mass of the neutrino could be constrained at 1eV level (Arnaud 2002) But looking at the detection range of existing neutrino detectors (<Local group limited) is discouraging Some promising evaluation has been made (Ando 2005) for the next generation of Megaton-scale detectors Ando 2005 SIF - Bologna

19 The Einstein Telescope The Einstein Telescope project is currently in its conceptual design study phase, supported by the European Community FP7 from May 2008 to July Participants per NON-Beneficiary Participants per Beneficiary MPG; 33 ASPERA-SAC, Apr2010 UNIGLASG OW; 33 UNIBHAM; 9 INFN; 57 VU; 7 CNRS; 17 CU; 4 EGO; 13 Washington State University University of Southampton University of Minnesota Universiteit Van Amsterdam EGO Universitat Autonoma de Barcelona Università degli Studi di Trento Tuebingen University INFN The Royal Observatory Raman research institute Nicolaus Copernicus MPG Astronomical Center Moscow CNRS State University MIT LIGO KFKI Research Institute for Particle and Hungarian Academy of science Friedrich-Schiller-Universität Jena Deutsches Elektronen-Synchrotron Dearborn observatory (NorthWestern Nikhef Cork University CERN CALTECH British Astromomical Association Participant University of Birmingham University of Glasgow Cardiff University Country Italy France Italy Germany France UK UK NL UK

20 Targets of the Design Study Evaluate the science reaches of ET Define the sensitivity and performance requirements Site requirements Infrastructures requirements Fundamental and (main) technical noise requirements Multiplicity requirements Draft the observatory specs Site candidates Main infrastructures characteristics Geometries Size, L-Shaped or triangular Topologies Michelson, Sagnac, Technologies Evaluate the (rough) cost of the infrastructure and of the observatory ASPERA-SAC, Apr

21 How ET goes beyond the 2 nd generation? Seismic h(f) [1/sqrt(Hz)] Hz Frequency [Hz] 10 khz SIF - Bologna

22 Very Low Frequency Appealing for massive objects (IMBH) and CW from NS Two related obstacles: Seismic noise Gravity gradient noise (induced by seismic noise) Virgo already implements the status of the art in seismic filtering difficult to do largely better We need to reduce the seismic noise 1. Go in the space 2. Go on the Moon 3. Go underground!!! SIF - Bologna

23 Underground Seismic noise Measurement SIF - Bologna

24 Seismic filtering Test on the Virgo Super-Attenuator Pre-filtering (IP) neglected SIF - Bologna

25 Gravity Gradient Noise reduction An underground site permits also to suppress the GGN influence Additional noise subtraction G. Cella 2009 schemes under study Surface -10 m The current level of -50 m understanding of the seismic -100 m noise related limitation indicates -150 m that the selection of a quiet site, at about 100m deepness, adopting a filtering system à la Virgo about 17 m tall, is compliant with the most stringent ET requirements (ET- ET-C C) starting from about 3Hz New (~10km arm length) ET-B infrastructure!!! SIF - Bologna

26 Cryogenics Thermal noise reduction (middle range frequency) requires a big jump Optimization of the dissipations (Fluctuation-dissipation theorem) progresses are probably saturated Best substrates selected for advanced detectors Coating progresses expected to be limited Difficulties in further increasing the beam radius (LG modes) Monolithic fused silica suspensions close to the best achievable Need to profit of the equi-partition theorem: Cryogenics Direct reduction of the thermal noise New materials needed (Si, Al 2 O 3, ) New optoelectronics needed New infrastructures needed SIF - Bologna

27 High frequency High frequency noise reduction requires the suppression of the quantum noise Shot noise reduction Brute force approach: High power in the FP cavities High power laser High reflectivity Thermal lensing issues Parametric instabilities Difficult cross-compatibility with cryogenics QND techniques: squeezing Promising (10dB in lab), tests starting now Frequency dependent implementation New infrastructures SIF - Bologna

28 ET sensitivity (sensitivities) Implementing all the technologies under study for ET a target sensitivity (ET-B) can be draft Doubts on the cross-compatibility of the technologies Need to simplify the problem Xylophone strategy SIF - Bologna

29 New infrastructure A 3 rd generation GW observatory is a must for the GW community to consolidate a new era for the GW astronomy We need to develop new technologies for our interferometers to go beyond the advanced detectors But, as first priority, we need new infrastructures to host the GW observatories for decades The first lesson we learned is that the new infrastructure must be hosted in an underground site We are compiling the list of candidate sites But, what about the geometry of the new infrastructure? SIF - Bologna

30 Geometry optimization L Fully resolve polarizations L 45 5 end caverns 4 L long tunnels 45 stream generated by virtual interferometry Null stream Redundancy 7 end caverns 6 L long tunnels 60 L =L/sin(60 )=1.15 L Fully resolve polarizations by virtual interferometry Null stream Redundancy ~3-9 end caverns Equivalent to 3.45 L long tunnels L (Freise 2009) SIF - Bologna

31 Schematic view Full infrastructure realized Initial detector(s) implementation 1 detector (2 ITF) Physics already possible in coincidence with the improved advanced detectors Progressive implementation 2 detector (4 ITF) Redundancy and crosscorrelation Full implementation 3 detector (6 ITF) Virtual interferometry 2 polarizations reconstruction The infrastructure ASPERA-SAC, Apr

32 The ET project The target of the ET project is to realize in Europe a fundamental Research Infrastructure that could host the Gravitational Wave observatories for decades, opening the GW precision astronomy and implementing the technical evolutions in the detectors composing the observatory The implementation of the full observatory is diluted in the years and triggered by the first detection Similar efforts are currently starting in US SIF - Bologna