predictions from Lattice QCD
He is right! The post- and pre-dictions of real experimentally accessible quantities are confirmed now at the couple percent level – something which is not generally appreciated in the HEP community.
For example, in hep-lat/0304004 show that computations with staggered quarks correctly reproduce the known values for nine diverse and independent non-perturbative quantities, after the quarks masses and lattice spacing (equivalent to the strong coupling constant) have been tuned. As pointed out in the paper, this result is important not only for the impressive level of agreement for those nine quantities, but also for the way LQCD physics is inextricably linked to B-physics. To put it bluntly, we have a confirmed theory here, not just a clevel phenomenological model. (Not that clever phenomenology is bad – it does help us to think about the physics, at least at an early stage of the game.)
Even more impressive are the successes discussed briefly in hep-lat/0509169. These are true predictions – LQCD was used to obtain precise values for three quantities which were first published and then subsequently confirmed by actual measurements in real experiments. These quantities are, specifically:
- the q2-dependence of the form-factor in semileptonic D-decays
- the decay constants for D+ and Ds mesons
- the mass of the Bc-meson
I consider Fig.1 in Kronfeld et al. (hep-lat/0509169) to be especially striking.This is a big deal for particle physics. There are many places in which fundamental quantities such as elements of the CKM matrix cannot be extracted reliably from measurements due to poorly known “phenomenological” constants. For example, we would like to extract precise values for third-generation CKM matrix elements from the recent measurements of Bs-mixing (D0: hep-ex/0603029 and CDF: FERMILAB-CONF/06-076-e) and lattice will play a key role. It’s time to start paying closer attention to LQCD, at least for me!
Thanks, Georg, for the info!!
Entry filed under: Particle Physics.