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Guest Post: Ben Allanach, On Open Access

Ben Allanach, guest blogger, is a Professor of Theoretical Physics at the University of Cambridge...

New Limits On VY Production From CDF: Good, But Also Disappointing

Alas, for once I must say I am not completely happy of one new result by the CDF collaboration...

The Plot Of The Week: Higgs Decays To WW In ATLAS

The latest paper by the ATLAS Collaboration is a very detailed report of the search for Higgs boson...

Travel Blog

While I do intend to update this blog today or tomorrow with a report on a nice new measurement...

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Tommaso DorigoRSS Feed of this column.

I am an experimental particle physicist working with the CMS experiment at CERN. In my spare time I play chess, abuse the piano, and aim my dobson telescope at faint galaxies.... Read More »

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"If you have seen the movie Particle Fever about the discovery of the Higgs boson, you have heard the theorists saying that the only choices today are between Super-symmetry and the Landscape. Don’t believe them. Super-symmetry says that every fermion has a boson partner and vice versa. That potentially introduces a huge number of new arbitrary constants which does not seem like much progress to me. However, in its simpler variants the number of new constants is small and a problem at high energy is solved. But, experiments at the LHC already seem to have ruled out the simplest variants.
Among the viable extensions of the standard model, an intriguing class of models involve the concept of a "hidden sector" of new particles only weakly coupled to the standard model one. These particles could be produced in the decay of heavy standard model particles, be invisible, but unstable, and thus soon decay back into standard model bodies, giving funny experimental signatures that our detectors could spot -if we looked for them carefully enough.
Until the second half of the nineties, when the LEP collider started to be upgraded to investigate higher centre-of-mass energies of electron-positron collisions than those until then produced at the Z mass, the Higgs boson was not the main focus of experiments exploring the high-energy frontier. The reason is that the expected cross section of that particle was prohibitively small for the comparatively low luminosities provided by the facilities available at the time. Of course, one could still look for anomalously high-rate production of final states possessing the characteristics of a Higgs boson decay; but those searches had a limited appeal.
Interaction with matter changes the neutrino mixing and effective mass splitting in a way that depends on the mass hierarchy. Consequently, results of oscillations and flavor conversion are different for the two hierarchies.
Sensitivity to the mass hierarchy appears whenever the matter effect on the 1-3 mixing and mass splitting becomes substantial. This happens in supernovae in large energy range, and in the matter of the Earth.
The Earth density profile is a multi-layer medium where the resonance enhancement of oscillations as well as the parametric enhancement of oscillations occur. The enhancement is realized in neutrino (antineutrino) channels for normal (inverted) mass hierarchy.
Preparing the documents needed for an exam for a career advancement, to a scientist like me, is something like putting order in a messy garage. Leave alone my desk, which is indeed in a horrific messy state - papers stratified and thrown around with absolutely no ordering criterion, mixed with books I forgot I own and important documents I'd rather have reissued rather than searching for them myself. No, I am rather talking about my own scientific production - pubished articles that need to be put in ordered lists, conference talks that I forgot I have given and need to be cited in the curriculum vitae, refereeing work I also long forgot I'd done, internal documents of the collaborations I worked in, students I tutored, courses I gave.
Although now widely accepted as the most natural explanation of the observed features of the universe around us, dark matter remains a highly mysterious entity to this day. There are literally dozens of possible candidates to explain its nature, wide-ranging in size from subnuclear particles all the way to primordial black holes and beyond. To particle physicists, it is of course natural to assume that dark matter IS a particle, which we have not detected yet. We have a hammer, and that looks like a nail.