The quest for gravitational waves

2 The Universe has been studied essentially through EM radiation. GWs have a different origin. The Scientific Motivation

According to General Relativity, gravitational fields distort space-time. GW’s alternately squeeze and stretch space in two perpendicular directions displacement of free masses deformation of elastic bodies To detect GW’s: monitor distances among free masses detect ringing of mechanical resonators The Physical Effect

The VIRGO Collaboration:  First studies: – Brillet (Nice): optics – Giazotto (Pisa): seismic isolation  Collaboration Italy - France established in 1992 CNRS and INFN approved the VIRGO project Construction starts near Pisa The history of the project

 Foundation of EGO in /2005 Commissioning 2006 Physics Netherlands: Nikhef joined EGO in 2006  EGO Council approved Advanced VIRGO in 2009 Poland (POLGRAW) & Hungary (RMKI) joined EGO in 2010

EGO/VIRGO A large infrastructure : 3 km long arms: Δ L / L = ha of land; ~ m 3 of buildings The largest high vacuum system in Europe : 7000 m 3 P ≅ mbar High tech optics Several class 10 clean rooms m 3 thermo stabilized to °C 600 kW electrical power 24h/24h data taking; 1 TB/day collected

 LAPP – Annecy  NIKHEF – Amsterdam  Radboud Univ. - Nijmegen  RMKI - Budapest  INFN – Firenze-Urbino  INFN – Genova  LMA – Lyon  INFN – Napoli  OCA – Nice  LAL – Orsay  APC – Paris  LKB - Paris  INFN – Padova-Trento  INFN – Perugia  INFN - Pisa  INFN – Roma 1  INFN – Roma 2  POLGRAV - Warsaw

The Consortium shall have as its purpose the promotion of research in the field of gravitation in Europe. EGO pursues the following objectives: ensures the construction of the antenna VIRGO, its operation, maintenance and the upgrade of the antenna as well as its exploitation. Aims according to Statute

Master laser, 1W Slave laser, 22W Main Beam Path F.I. E.O. F.I. Laser

Ferrara – September 30th, 2010 A.Viceré – Università di Urbino & INFN Firenze 10/60 Super mirrors Fused silica mirrors 35 cm diam, 10 cm thick, 21 kg Scattering losses:a few ppm Substrate losses: 1 ppm Coating losses: <5 ppm Surface deformation: /100

The Beam Splitter mirror inside the vacuum tower

The Virgo vacuum system 7000 m 3 below mbar: the largest Ultra-High-Vacuum system in Europe West tube 3 km North tube 3 km

Inside Central Building

VIBRATION ISOLATION Thermal noise Superattenuator: filters off the seismic vibrations.

 ~100 yrs from Einstein’s “prediction”, only indirect evidence  “Complexity”  Precision never reached before in any physics experiment  high tech needed and developed “ad hoc” research infrastructures  Ambiguity of source (local noise vs outer signal)  coincidences  Identification of the sources  triangulation, vision by multiple eyes The same nature of the physical problem determines the strategy of research. Hence, Cooperation more than Competition Why a global strategy ELiTES October 2012

GW interferometric initial detectors A network of detectors has been active in the World until few years ago ASPERA 2012: GW detectors 19 TAMA, Tokyo, 300 m (now CLIO) GEO, Hannover, 600 m LIGO Livingston, 4 km Virgo, Cascina, 3 km LIGO Hanford, 4 km: 2 ITF on the same site! GEO, Hannover, 600 m

GW interferometric initial detectors A network of detectors has been active in the World until few years ago TAMA, Tokyo, 300 m (now CLIO) GEO, Hannover, 600 m LIGO Livingston, 4 km VIRGO, Cascina, 3 km LIGO Hanford, 4 km: 2 ITF on the same site! GEO, Hannover, 600 m

The search for GW signal emitted by a binary system (NS-NS) requires a network of (distant) detectors ASPERA 2012: GW detectors 21 Event reconstruction Source location in the sky Reconstruction of polarization components Reconstruction of amplitude at source and determination of source distance (BNS) Detection probability increase Detection confidence increase Larger uptime Better sky coverage

New players ! 22 KAGRA A 2.5 generation detector, under construction in Japan, implementing new technologies in a 3km long site in Kamioka (2018)

(Further) New players ! LIGO-India The move of aLIGO-H2 to India to improve pointing capabilities of the GW detector network ( ) is almost decided AIGO Attempt to build a GW interferometer in Australia

Summary An efficient, responsive and light structure to support Virgo and promote European collaboration under supervision by national institutions EGO existence relies on Virgo/AdV success The future of GW in Europe depends upon a stronger collaboration between EU countries. EGO may prefigure the required infrastructure. Advanced VIRGO