Physics

I reported two days ago on the new measurements by the CMS Collaboration of the decay of B hadrons into muon pairs, revealed at the opening of the EPS 2013 conference in Stockholm and in a preprint. Funnily, I wrote the piece oblivious of the LHCb result, which is basically equivalent (in importance, precision, and sensitivity) to the CMS one; when I found out that LHCb had also a comparable result, I made up for that by pointing out the LHCb result in a "UPDATE" at the end of the post - I did not want to rewrite half of the piece! Today, however, I would like to do here for you what most…

Today I am quite happy to report of a new groundbreaking result from the CMS collaboration at the CERN LHC - the experiment to which I devote 100% of my research time. We published overnight a report on the Cornell arxiv, and will present this week at the EPS conference in Stockholm, of the observation of B_s meson decays to muon pairs, an exceedingly rare process which is of extreme importance for the searches of new physics beyond the standard model. And in so doing, CMS now leads this race, with better results than LHCb and ATLAS. (UPDATE: but see below, at the bottom of the article). The…

When we want to combine several estimates of a physical quantity, to obtain a more precise one that accounts for all inputs in the correct way, we routinely rely to the weighted average: we take each of the N independent, Gaussian-distributed measurements x_i +- σ_i (i=1,...,N) and compute with them the quantity to which we associate the error shown on the right above. The recipe above is simply the result of applying the method of least squares, or -equivalently- of a likelihood maximization. It turns out that in many cases we are confronted with estimates of the same physical quantity that…

When we want to combine several estimates of a physical quantity into a more precise one that accounts for all in the correct way, we routinely rely to the weighted average: we take each of the N independent, Gaussian-distributed measurements x_i +- σ_i (i=1,...,N) and compute with them the quantity to which we associate the error computed as The recipe above is simply the result of applying the method of least squares, or -equivalently- of a likelihood maximization. It turns out that in many cases we are confronted with estimates of the same physical quantity that appear to be incompatible…

When we want to combine several estimates of a physical quantity into a more precise one that accounts for all in the correct way, we routinely rely to the weighted average: we take each of the N independent, Gaussian-distributed measurements x_i +- σ_i (i=1,...,N) and compute with them the quantity to which we associate the error computed as The recipe above is simply the result of applying the method of least squares, or -equivalently- of a likelihood maximization. It turns out that in many cases we are confronted with estimates of the same physical quantity that appear to be incompatible…

Neutrinos are the second most abundant particles in the Universe, after photons, but when it comes to being elusive they can compete with anything. That's due to their having extremely weak interactions with all other particles, which leads to them being called  'ghost particles’. Neutrinos are invisible but could carry as much mass as all other known forms of matter, traveling almost at the speed of light over fantastic distances. Their tiny masses have  important consequences for the structures in the Universe and they are the driving element in the explosion of Supernovae. But…

NASA's Solar Dynamics Observatory and the Reuven Ramaty High Energy Solar Spectroscopic Imager have provided the most comprehensive movie ever of a mysterious process at the heart of all explosions on the sun: magnetic reconnection. Magnetic reconnection happens when magnetic field lines come together, break apart and then exchange partners, snapping into new positions and releasing a jolt of magnetic energy. This process lies at the heart of giant explosions on the sun, such as solar flares and coronal mass ejections, which can fling radiation and particles across the solar system.…

The querelle on the device patented by Andrea Rossi, the E-CAT, which allegedly produces heat from nuclear fusion processes inside a small cylindrical reactor fueled with Hydrogen and Nickel powder, continues to draw the attention of the gullible as well as that of the knowledgeable. It is just entertaining to both! Recently I mentioned here the results of an "independent" test (by G. Levi et al.) of two of the "energy catalyzers" invented by Rossi, pointing out the relevance of the claim that the authors were making. For those who can read between the lines, that does not mean of course that…

This morning I had a funny dream, and as I woke up at the end of it and watched the clock with the only eye I had managed to open, I realized it was not yet really time to wake up. On the other hand, I really liked the dream I had had: it was quite vivid and detailed, plus it lent an occasion for a blog post! Hence I crawled out of the bed and reached for the nearest laptop in order to download the contents of my mind before it made room for something else and the dream got lost forever. In the dream I am at a physics laboratory I cannot at first identify. I am being asked by a physics…

Like gems hidden in mountains of sand, I have sifted through vast amounts of data which have been gathered by surveys covering wide areas of the sky at particular wavelengths, and found likely star forming cores, hints of circumstellar disk and outflows in regions of massive star formation. The procedural lesson from my masters thesis is that there are discoveries waiting to be made by comparing data sets gathered at different frequencies, and by conducting coordinated multi-spectral surveys of massive star forming regions.  The work reported on here was done as my Masters Thesis "…