Guido PizzellaUniversita’ di Roma Tor VergataINFN- Frascati

Coincidences between the g.w. detectors EXPLORER and NAUTILUS

LISA

CERN RE 5

LNF INFN

LNGS

ROG CollaborationLNF, Roma1, Roma2

Calibration:a) gravity induced by

a rotorb) cosmic ray showers

(in addition to small applied forces)

Vmeasured=19.1±0.7mV

Vexpected=21.1±0.6mV

Astone et al., Z.Phys.C50:21-29,1991Eur. Phys. J. C 5, 651-664 (1998)

Cosmic Rays

a) Large signalsb) Small signals

threshold

time

energy

ExplorerLarge signalsExplorer 2003

Large signalsNautilus 2004

Small signals

Measurements with an electron beam at DANE

Buonomo et al., Astropart.Phys.24:65-74,2005

aluminum

niobium

Search for coincidences

Cross-section depending on orientation

= osin4()

Sidereal hour 3.5

Sidereal hour 12.2

Sidereal hour

Efficiency of detection

3.5 hour

Polarized sources in the Galactic CentreAstron.Astrophys.421:811-813,2004

3.5±1.5

Sidereal hour

Sources uniform over the galactic disk

Measurements during the years1998, 2001,

2003, 2004

threshold

time

energy

1998

...we find an excess of coincidences

at zero time delay in the direction of the galactic

centre.

Class.Quant.Grav.18:243-252,2001

In the conclusions of the 1998 paper presented to the IGEC collaboration

in 1999 and 2000 and written together with the LSU group:

2001Class.Quant.Grav.19:5449-5463,2002

2003Class.Quant.Grav.23:S169-S178,2006

2004

all sidereal hours3.5±1.5

sidereal hours

Combining the probabilities

The coincidences excesses are

concentrated at certain times

1998

2001

2003

2004

Day of year

Searching if any special astrophysical phenomena occurred in

the period 7-17 September 1998

Last figure

1.1 10-4

7-17 September 1998

ConclusionWe have shown a

coincidence excess with very small

probability to be accidental (1% in total, 0.02% at

selected sidereal hours).Gravitational waves ?

end

6432 ore 2004nc=27<n>=1.8Offset=6.7 ms=5.9 ms