Archive for June, 2006
I must tip my hat to Tommaso, who has made several excellent HEP-related posts in the past several days. In particular, he has tipped us off to some interesting physics from the Tevatron.
First, he described with wonderful clarity and simplicity the analysis of the angular decay distributions of the X(3872). This is a very nice result coming from CDF which helps identify the nature of this peculiar object. See his post for the discussion, to which I would add that this kind of physics is rich and interesting, if not the most popular in HEP. However, if you want really to know what’s going on, you need to pay attention – if new particles are found at the LHC then the same kinds of analyses will be needed to identify them. Also, I agree that it is slightly embarassing that CDF had a nice signal in the data but did not spot this until after Belle did. We are not being vigilant enough, perhaps…
Second, Tommaso predicts that evidence for single-top production will be found by CDF and D0 this year. He is probably right, and for the reasons why this is a difficult experimental task, see his posting. This topic has been on the main menu of the Tevatron program since the beginning of Run II, so it will be nice to check that one off, as we have already done for di-boson production. And as more data are accumulated, this provides another opportunity to probe for new physics, either in the properties of the signal events, or in related samples. Is there a reason why one might see a top-bottom resonance – certainly possible. Could anomalous events fall into this SM sample? Let’s hope so, and that someone looks.
Finally, Tommaso discussed the famous Mtop-MW plot which shows that the measurements are more comfortable with the MSSM than with the SM, though they do not rule out the SM (as Tommaso stresses). Here I see things a little differently than Tommaso does, so I will have to prepare my own comments on what this plot means and what the future may bring. On one thing I strong agree and would emphasize: the precise measurement of the top-quark mass must remain a high priority for the Tevatron program. Not only does it help give a hint of what is to come at the LHC, but for experimental reasons the Tevatron experiments really can measure this better than the LHC ones, at least for the next several years. I hope very much we will achieve 1.0 GeV, which can be compared to the projection of 1.5 GeV at the LHC…
One of my favorite quotes comes from Louis Pasteur:
"In the fields of observation, chance favors the prepared mind."
It seems to me that too much of our research is guided by our theoretical prejudices, and there is too little emphasis on pursuing the oddity that crops up in our data. It takes a different kind of skill and discipline to do so, but I believe that such pursuits are vitally important in experimental science. Of course the vast majority of oddities are just statistical fluctuations or systematic effects (in which case a proper investigation may save us from publishing a wrong result!) but if an anomaly turns out to be real, then science will get a huge boost forward.
Two recent posts speak to this topic. The first one comes from Jao Ortega-Ruiz at his blog physics musings. He gives a wonderful account of several crucial observations made in the last century – I strongly recommend reading it! (It is interesting to note that he is a theoretical physicist.)
The second comes from Tommaso Dorigo's prodigious blog A Quantum Diaries Survivor. He talks about fishing for new physics, and with a cute diagram shown by Jaco Konigsberg, makes the argument that we should be "fishing" in our data if we hope to find something "deep."
I think that every advanced graduate student and post-doc should be spending at least 20% of his or her time chasing something that looks wierd to him or her. You learn the most that way and your research becomes your own – not just part of some grand program to "do collider physics." It is so much more interesting to go to an internal physics meeting and hear about a problem that has cropped up in someone's analysis than to listen to answers to a dozen questions posed by experts trying to raise the level of a given analysis. In my opinion, the latter can be carried out offline, while the former, potentially, enriches all who are present and who participate in the discussion.
Please read a very eloquent piece by Lawrence Krauss called Discovery for the Sake of Discovery. It is published in SEED magazine as part of a series on the LHC. Krauss makes a most basic and fundamental justification for high-energy physics experiments – they are an important example of what is good about our civilization. For me, this is the real reason why we should do particle physics, both on the experimenal and the theoretical side.
But don't waste time reading my comment – read his article please!