Tuesday, May 22, 2012

Charm in Honolulu

 "The wise man is happy even in the mud," said Visa, "as the yogi Bandachandra said"
"I remember, I was also at his seminar in Honolulu" said Pat

[from Elianto by S. Benni]

As Paolo already announced the last week I was at the CHARM 2012  conference in .... yes... Honolulu!
The real titling should be "The 5th international workshop on charm physics", and as you might have guessed charm refers to the quark not (only) to the location!

The conference saw a very intensive 4 days of talks from all around the world both on the experimental and theoretical status on the charm.

In short the importance of the charm quark is that many effects such as mixing and rare decays are suppressed by the Glashow-Iliopoulos-Maiani mechanism more than in the more studied b quark.
For years theoreticians used to say that any evidence of oscillation (mixing) of a D0, a charmed meson, with its anti-particle, would have been a clear sign of new physics...
Then mixing was discovered and theoreticians said "well... there are long distance contributions so probably is only Standard Model, but if you see CP violation in charm, that's New Physics for sure!"
This year LHCb gave the first evidence of CP violation in charm and CDF confirmed it... (maybe I will talk about this in another post) but theorists still are arguing whether the Standard Model calculations are correct...
The point here is that charm is not heavy enough to be treated perturbatively nor light enough to be treated with techniques used for the light quarks and therefore calculations are difficult and with large uncertainties. 
As a personal opinion, the only way to disentangle between Standard Model and some alternative scenario will probably be having in hands many different precise measurements, rather than expecting a huge deviation in a single one... and this is especially true for charm physics.

This is a short appetizer of what was discussed.
While I think of the subject of a more detailed post I leave you with a scheme of my deep thoughts during this conference:

p.s. there were only two puns about charm, charming, charmed something... I would have expected more!
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