Today I wish to bring to your attention a figure recently obtained by the CDF collaboration, one which really tells a thousand words. Before I describe it to you, however, I would like to discuss at an elementary level a few basic concepts of particle theory which the figure well summarizes.
A Crash Course on Feynman Graphs
Let us start with a few elements on Feynman graphs -the diagrams that physicists use to draw on their blackboards to picture what really happens when particles react, and that actually enable the computation of the probability of those processes.
The slide below was shown yesterday at an invited talk that Antonio Masiero gave in the University of Bologna, during an open session of the CMS Physics week (see, I am careful to note I am not breaking any rules by showing material relevant to internal CMS business: the session was open!).
Can we bring life forms into pure quantum states
? Will we ever manage to elevate Schrodinger's cat
from thought experiment
to real-life experiment? A recent publication
suggests the answers to above questions are affirmative.
The CDF collaboration has recently released a study of the production of pairs of W bosons in a large bounty of proton-antiproton collisions produced by the Tevatron collider -3.6 inverse femtobarns of them, or roughly 300 trillions, give or take 6%.
The measurement of the production cross section of this clean and rare electroweak process (its absolute rate, that is) is the most precise ever obtained so far, and reaches down to a level of uncertainty which cannot be improved further significantly at the Tevatron, because it is now limited by the uncertainty in the overall integrated luminosity mentioned above.
Sometimes I come to think this blog is overextended: it happens when I realize it contains more things than I can remember, even ones I would really like to have at my fingertips. I was reminded yesterday of a very funny story which a reader left in the comments thread of a rather meaningless post, and decided I should make a separate post of it, since it made my day reading it and it might make yours too...
The story was told by Leon Lederman in an introduction to Carlo Rubbia in the proceedings of a conference held in 1984 in Santa Fe:
"... Now I have some interesting news, a story that is at the least
apocryphal. It concerns the heroic contestant in one of those ancient
trials by strength which are so natural for our "Carlo". This trial was
"It is better to treat p values as nothing more than useful exploratory tools or measures of surprise. In any search for new physics, a small p value should only be seen as a first step in the interpretation of the data, to be followed by a serious investigation of an alternative hypothesis. Only by showing that the latter provides a better explanation of the observations than the null hypothesis can one make a convincing case for a discovery."
Luc Demortier, "p values and nuisance parameters", CERN-08-001, p.24.
A few days ago I produced a summary of a poster I presented at Physics in Collisions this week, which dealt with the searches for the Standard Model Higgs boson that CMS will undertake, and the results it can obtain in a scenario when a certain amount of data is collected at the full design energy of the LHC.
Here, instead, I wish to summarize the other poster I presented at the same venue, which concerned the combination of the most sensitive search channels, the sensitivity of CMS with a given amount of data, and the derating of its significance reach or observation power entailed by the running of LHC at a smaller-than-design beam energy. But I will do this only as a way of introducing a more interesting discussion, as you will see below.
Was an almighty God required to boot up
the universe, or would a blindfolded monkey have sufficed?
What a silly question. Isn't it obvious that truly divine powers were needed to create our amazing universe capable of evolving systems of supreme complexity called 'life'? Maybe. Maybe not. It all boils down to the question: How special was the big boot
, the mother of all boot-ups commonly referred to as the big bang
The Physics in Collisions conference in Kobe is over, and I am packing up. Tomorrow morning I will leave from KIX to FRA, and later FRA to VCE, hopefully making it home for dinner.
I learned a few interesting things on physics at the conference, and I hope I will share some of the highlights with you in a post tomorrow. But I also learned quite a few things about Japanese culture, which probably was a more valuable experience for me.
For now, I will just offer you the picture below, which portrays a rather overaged student in front of his two posters. Regulars of this site will not fail to notice that despite the suit (jacket not shown), I am wearing a Scientific Blogging shirt (blue logo near the pocket).
This morning I attended the first session of the Physics in Collisions conference in Kobe, which dealt with Electroweak Physics. The four talks I could listen to were all of very good quality, and I am not ashamed to say that I did learn a thing or two, despite this is a field of investigations on which I have focused for over a decade. Also, I decided that conferences featuring few, long talks are definitely better than ones which try to cram dozens of small contributions in tight schedules: at least, the session conveners are not required to play the watchdog and struggle to keep people within their allotted time, and post-talk questions and comments are actually encouraged rather than suppressed.