And so about cascade baryons… June 15, 2007Posted by dorigo in news, physics, science.
So it is D0, not CDF, that is credited for discovering cascade b-baryons first in the end. A Fermilab press release explains that the result has been submitted to Physical Review Letters on June 12th.
Congratulations to D0 for pulling this off! After the discovery of Sigma_b baryons by CDF, it seems only fair to have D0 get their own share of credit for the fantastic amount of information on the Standard Model that the Tevatron is producing.
The Xi_b particle (not Chi_b, with which I sometimes confuse myself – see comment by Lubos Motl below) is a baryon composed of a (bds) quark triplet. Three down-type quarks, each of electrical charge -1/3, but of very different properties: the d-quark weighs only a few MeV, the s-quark weighs thirty times more, and the b-quark weighs still a factor of thirty more than the s-quark. An odd, massive object (almost 6 times heavier than the lightest baryons, proton and neutron), whose decay is driven by the characteristics of the b-quark, which has a long lifetime. It is through that peculiarity (among others) that Xi_b baryons, although quite rare, can be identified.
My hands are itching, but I will abstain from saying what CDF has to say about these particles… I decided to play by the rules of our experiment, one of which asks bloggers to refrain from posting new results until the authors have had a chance to announce it first.
UPDATE: today at 1PM CST, D0 and CDF will give two back-to-back seminars on the discovery of the Xi_b baryon. You can follow the presentation via live stream video from this site (click on Services Offered: Streaming Video)
UPDATE 2: seems like the correct link is this one .
UPDATE 3: now that the CDF result has been presented by its authors, I break no rules if I release information about it here – I had a post out last Sunday, but decided to take it offline once I realized that the B group conveners in CDF had asked the result to be kept confidential until a formal release. In the meantime, D0 sent their own result out directly to Physical Review Letters, beating CDF in the race in a rather odd way (important results should be coordinated between the two experiments). Anyway, it does not matter much who made the announcement first – the important thing is that these particles are seen. I will discuss the details of the two analyses soon in another post.