New tests of the universality of free fall

Details New tests of the universality of free fall New tests of the universality of free fall

Sep 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phrvd..50.3614s&link_type=abstract

Physical Review D (Particles, Fields, Gravitation, and Cosmology), Volume 50, Issue 6, 15 September 1994, pp.3614-3636

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172

Experimental Studies Of Gravity, Other Particles, Dark Matter

Scientific paper

We use a continuously rotating torsion balance to make new tests of the universality of free fall (UFF). We study differential accelerations of Be-Cu and Be-Al test-body pairs in the fields of Earth, the Sun, our Galaxy, and in the direction of the cosmic microwave dipole. We also compare the acceleration towards the Sun and our galactic center of Cu and single-crystal Si in an Al shell (this pair of bodies approximates the elemental compositions of Earth's core and the Moon or Earth's crust, respectively). In terms of the classic UFF parameter η, our Earth-source results are η(Be,Cu)=(-1.9+/-2.5)×10-12 and η(Be,Al)=(-0.2+/-2.8)×10-12 where all errors are 1σ. Thus our limit on UFF violation for Be and a composite Al/Cu body is η=(-1.1+/-1.9)×10-12. Our solar-source results are Δa(Be,Cu) =(-3.0+/-3.6)×10-12 cm/s2, Δa(Be,Al)=(+2.4+/-5.8)×10-12 cm/s2, and Δa(Si/Al,Cu)=(+3.0 +/-4.0)×10-12 cm/s2. This latter result, when added to the lunar laser-ranging result that senses both composition-dependent forces and gravitational binding-energy anomalies, yields a nearly model-independent test of the UFF for gravitational binding energy at the 1% level. A fivefold tighter limit follows if composition-dependent interactions are restricted to vector forces. Our galactic-source results test the UFF for ordinary matter attracted toward dark matter, yielding ηDM(Be,Cu)=(-1.3+/-0.9)×10-3, ηDM(Be,Al)=(+1.8+/-1.4)×10-3, and ηDM(Si/Al,Cu)=(+0.7 +/-1.0)×10-3. This provides laboratory confirmation of the usual assumption that gravity is the dominant long-range interaction between dark and luminous matter. We also test Weber's claim that solar neutrinos scatter coherently from single crystals with cross sections ~1023 times larger than the generally accepted value and rule out the existence of such cross sections.

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