# Constraints on possible fifth fundamental force

1. Jun 4, 2013

2. Jun 4, 2013

### marcus

I had not seen the article. Sounds as if it might be interesting, in the area of technique. Not that they unearthed anything new, but that they found a way to narrow the possibilities of there being something new.
For the convenience of anyone who's curious, here is the arxiv link:
http://arxiv.org/abs/1304.6560
Bounds on fifth forces from precision measurements on molecules
E. J. Salumbides, J. C. J. Koelemeij, J. Komasa, K. Pachucki, K. S. E. Eikema, W. Ubachs
(Submitted on 24 Apr 2013)
Highly accurate results from frequency measurements on neutral hydrogen molecules H2, HD and D2 as well as the HD+ ion can be interpreted in terms of constraints on possible fifth-force interactions. Where the hydrogen atom is a probe for yet unknown lepton-hadron interactions, and the helium atom is sensitive for lepton-lepton interactions, molecules open the domain to search for additional long-range hadron-hadron forces. First principles calculations in the framework of quantum electrodynamics have now advanced to the level that hydrogen molecules and hydrogen molecular ions have become calculable systems, making them a search-ground for fifth forces. Following a phenomenological treatment of unknown hadron-hadron interactions written in terms of a Yukawa potential of the form $V_5(r)=\beta exp(-r/\lambda)/r$ current precision measurements on hydrogenic molecules yield a constraint $\beta < 1 \times 10^{-7} eV Å$ for long-range hadron-hadron interactions at typical force ranges commensurate with separations of a chemical bond, i.e. $\lambda ~1 Å$ and beyond.
Comments: 7 pages, 3 figures, 1 table

3. Jun 4, 2013

### ohwilleke

Interesting, but the most plausible places to look for new forces are either at the galactic scale and larger (explaining some or all dark matter/dark energy/inflation phenomena), or at sub-hadronic scales (binding preons into quarks and/or leptons and/or seemingly fundamental bosons at distances not much greater than Planck length and hence undetectable even by the LHC which excludes preons unless they are very, very small indeed), or in high energy circumstances approaching the GUT scale where the so called "force" might like the weak nuclear force not present in a manner very akin to our common sense understanding of a "force."

I can see the motive for these studies in the muonic hydrogen v. ordinary hydrogen proton size anomaly, but I would be totally stunned if a fifth force were discovered at the atomic or molecular scales.

4. Jun 5, 2013

### tom.stoer

At the atomic length scale you should be able to detect effects of a fifth force mediated by ultra-light or massless particles.