A measurement of the solar and sidereal cosmic-ray anisotropy at E(0)similar to 10(14)eV

The results of the measurement of the cosmic-ray solar and sidereal anisotropies at primary energy E(0) approximate to 10(14) eV performed by the EAS-TOP Extensive Air Shower array (Campo Imperatore, National Gran Sasso Laboratories, 2005 m above sea level, latitude 42 degrees.5 N are presented. The measurement includes 4 years of data taking (1990, 1992, 1993, 1994) for a total of 1.3 x 10(9) events and is performed at two different mean primary energies: (E) over bar(0)(v) approximate to 1.5 x 10(14) eV and (E) over bar(0)(i) approximate to 2.5 x 10(14) eV. The two results are compatible (within 2 sigma) and can therefore be combined. The obtained amplitude and phase of the first harmonic in sidereal time are (in the equatorial plane) A(sid,delta=0c)((E) over bar(0) approximate to 2 x 10(14) eV) = (3.73 +/- 0.57) x 10(-4) and phi(sid) = 1.82 +/- 0.49 hr local sidereal time, with significance 6.5 sigma. The amplitude of the anisotropy exhibits the expected cos delta dependence. A first harmonic in solar time compatible with the expected Compton-Getting effect due to the motion of revolution of the Earth around the Sun is observed with significance 7.3 sigma. The corresponding measured amplitude and phase (also in the equatorial plane) are A(sol,delta=0o)=(4.06 +/- 0.55) x 10(-4) and phi(sol) = 4.92 +/- 0.53 hr, the expected values being 4.7 x 10(-4) and 6.0 hr. Different checks of stability of the detectors and consistency of the data are presented.