Search for hypothetical corrections of Newtonian gravity at l~ 100nm

1. Search for hypothetical corrections of Newtonian gravity at l~100nm Ricardo S. Decca Department of Physics, IUPUI

2. Collaborators Daniel López Argonne National Labs Ephraim Fischbasch Purdue University Dennis E. Krausse Wabash College and Purdue University Valdimir M. Mostepanenko Noncommercial Partnership “Scientific Instruments”, Russia Galina L. Klimchitskaya North-West Technical University, Russia Ho Bun Chan University of Florida Jing Ding IUPUI Hua Xing IUPUI NSF, DOE, LANL Funding

3. The strength of gravity for various numbers of large extra dimensions n, compared to the strength of electromagnetism (dotted) Without extra dimensions, gravity is weak relative to the electromagnetic force for all separation distances. With extra dimensions, the gravitational force rises steeply for small separations and may become comparable to electromagnetism at short distances. Jonathan L. Feng, Science 301, 795 (’03) What is the background?

4. Attractive force! • Dominant electronic force at small (~ 1 nm) separations • Non-retarded: van der Waals • Retarded: Casimir 2a No mode restriction on the outside

5. Yukawa-like potential • Arises from very different pictures: • Compact extra-dimensions • Exchange of single light (but massive, • m =1/l) boson • Moduli; Graviphotons; Dilatons; • Hyperphotons; Axions  f1 f2 1 2 PRL 98, 021101 (2007)

6. Arises from very different pictures: • Compact extra-dimensions • Exchange of light (but massive, m =1/l) boson • -Moduli • -Graviphotons • -Dilatons • -Hyperphotons • -Axions Yukawa-like potential How do we establish limits? Measure background and subtract it Get rid of the background altogether

7. Experimental setup

8. Dynamic measurements

9. zg Separation measurement zg = (2389.6 ± 0.1) nm, interferometer zi= ~(10000.0 ± 0.2) absolute interferometer zo = (6960.1 ± 0.5) nm, electrostatic calibration b = (210 ± 3) mm, optical microscope Q = ~(1.000 ± 0.001) mrad zmeas is determined using a known interaction zi, Q are measured for each position

10. Comparison with theory AFM image of the Au plane vi: Fraction of the sample at separation zi

11. Comparison with theory

12. Al2O3 Al2O3 Al2O3 “Casimir-less” experiments Au Au Ge Si MTO

13. “Casimir-less” experiments Signal optimization: Work at wo!!! Heterodyne Oscillate plate at f1, sphere at f2 such that f1 + f2 = fo

14. z = 500 nm 1 sec 10 sec 100 sec 1000 sec

15. “Casimir-less” experiments Signal optimization: Work at wo!!! Oscillate plate at f1, sphere at f2 such that f1 + f2 = fo 95% confidence level Net force! F

16. Sanity check: more samples! “Casimir-less” experiments

17. F

18. Background Motion not parallel to the axis (too small) Step (0.1 nm needed) Difference in electrostatic force (0.1 mV needed) Difference in Au coating (unlikely) Au coating not thick enough (unlikely) Al2O3 Au Au Au Ge Si MTO

19. -Improve signal -Reduce background What next?

21. About five orders of magnitude improvement Two orders of magnitude improvement

22. Conclusions • Most sensitive measurements of the Casimir Force • and Casimir Pressure • Unprecedented agreement with theory • First realization of a “Casimir-less” experiment • Improvement of about three orders of magnitude in Yukawa-like • hypothetical forces • New experiment under way. Results expected by the end of the year.