This white paper is submitted as part of Snowmass2013 (subgroup CF2). The extraordinary sensitivity of torsion-balances can be used to search for the ultra-feeble forces suggested by attempts to unify gravity with the other fundamental interactions.
The motivation, the results and their implications as well as the future prospects of this work are summarized. The experiments include tests of the universality of free fall (weak equivalence principle), probes of the short-distance behavior of gravity (inverse-square law tests for extra dimensions and exchange forces from new meV scale bosons), and Planck-scale tests of Lorentz invariance (preferred-frame effects, non-commutative geometries).
We show that a previous polarized 3He experiment at Princeton, plus Eot-Wash equivalence-principle tests, constrain exotic, long-ranged (lambda > 0.15m) parity-violating interactions of neutrons at levels well below those inferred from a recent study
of the parity-violating spin-precession of neutrons transmitted through liquid 4He. For lambda > 1.0e8 meters the bounds on gAgV are improved by a 11 orders of magnitude.
In 1970, the Soviet Lunokhod 1 rover delivered a French-built laser reflector to the Moon. Although a few range measurements were made within three months of its landing, these measurements---and any that may have followed---are unpublished and unava
ilable. The Lunokhod 1 reflector was, therefore, effectively lost until March of 2010 when images from the Lunar Reconnaissance Orbiter (LRO) provided a positive identification of the rover and determined its coordinates with uncertainties of about 100 m. This allowed the Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) to quickly acquire a laser signal. The reflector appears to be in excellent condition, delivering a signal roughly four times stronger than its twin reflector on the Lunokhod 2 rover. The Lunokhod 1 reflector is especially valuable for science because it is closer to the Moons limb than any of the other reflectors and, unlike the Lunokhod 2 reflector, we find that it is usable during the lunar day. We report the selenographic position of the reflector to few-centimeter accuracy, comment on the health of the reflector, and illustrate the value of this reflector for achieving science goals.
We summarize and critically evaluate the available data on nuclear fusion cross sections important to energy generation in the Sun and other hydrogen-burning stars and to solar neutrino production. Recommended values and uncertainties are provided fo
r key cross sections, and a recommended spectrum is given for 8B solar neutrinos. We also discuss opportunities for further increasing the precision of key rates, including new facilities, new experimental techniques, and improvements in theory. This review, which summarizes the conclusions of a workshop held at the Institute for Nuclear Theory, Seattle, in January 2009, is intended as a 10-year update and supplement to Reviews of Modern Physics 70 (1998) 1265.
Forty years ago, Apollo astronauts placed the first of several retroreflector arrays on the lunar surface. Their continued usefulness for laser-ranging might suggest that the lunar environment does not damage optical devices. However, new laser rangi
ng data reveal that the efficiency of the three Apollo reflector arrays is now diminished by a factor of ten at all lunar phases and by an additional factor of ten when the lunar phase is near full moon. These deficits did not exist in the earliest years of lunar ranging, indicating that the lunar environment damages optical equipment on the timescale of decades. Dust or abrasion on the front faces of the corner-cube prisms may be responsible, reducing their reflectivity and degrading their thermal performance when exposed to face-on sunlight at full moon. These mechanisms can be tested using laboratory simulations and must be understood before designing equipment destined for the moon.
