In this two-parts article I wish to describe in some detail, but still at an elementary level, the characteristics of one of the most important probes of the physics of subnuclear collisions at today's particle physics experiments: jets of hadrons originated from energetic bottom quarks, or more familiarly, b-jets. By posting a dedicated article on b-jets, I hope I will be able to describe in more detail elsewhere other physics topics, such as Higgs boson decays or top quark signatures, without being hampered by having to introduce the phenomenology and detection of b-jets from scratch every time.
As silly as it may look, I am going to start this post by publishing for the third time in a row the same figure. That is because I want to keep the promise I made earlier that I would explain in terms as simple as possible (although not simpler) the details hidden behind the coloured curves and functions pictured there. I will also take this chance to come down a little from the level of technicality of the recent posts: after all, this blog is supposedly for everybody, and not just for Ph.D. students and recipients.
Stars don't die without being noticed and sometimes the results are pretty spectacular. At the end of its life cycle, a star begins to collapse and throws new material into space, which eventually becomes incorporated into new planets and life.
Yesterday I posted a short article whose main purpose was to show a figure I had received from Sven Heinemeyer, a phenomenologist who specializes in the study of Minimal Supersymmetric extensions of the Standard Model (MSSM).
Besides predicting a mirror copy of Standard Model (SM) particles, MSSM models are characterized by containing not just one, but five distinct Higgs bosons; over much of the space of possible parameters of these theories, one of the five Higgs bosons is quite similar to the one and only SM Higgs, so that one can discuss the SM Higgs and the lightest neutral scalar of the MSSM together without generating confusion.
...waiting for a piece I will post tomorrow, to stimulate your curiosity -and allow me to travel from Venice to Patras by ship, with no internet connection.
The subject is not only the Higgs mass, but the top quark mass. Which top mass ? The "pole" mass -the real part of the pole in the perturbative top-quark propagator. Have I lost you ? Ok, do not worry -definitions are for theorists. Let us just say that the top quark, being a complicated coloured object which thus cannot live free of the influence of strong interactions,
is measurable at a hadron collider like the Tevatron only within uncertainties of the order of a constant called "Lambda QCD", which is of the order of 200 MeV.
I posted a very short rough paper here a while back. "Dark Matter and Energy as Particles and Fields of Unobserved Scalar and Vector Fields (PDF) (rev2).
." Since then certain comments and supposed extremely elementary errors have been pointed out. The following is a referee report from a well respected journal. These are (mostly) valid critiques stated in a polite and professional manner. None of the things which were pointed out by bloggers are here, which were for the most part so elementary that if true there would not even have been a peer review.
A new public document
has been made available on the CMS public web page yesterday morning. It reports on a study of the reach of the CMS detector, with data collectable in 2010, for a signal of large extra dimensions, using the very distinctive signature of a high-energy jet recoiling against -well, recoiling against nothing; or better, something which left our world and entered into another dimension of space.
From August 30th to September 2nd I will attend the 29th edition of "Physics in Collision" in Kobe, Japan, to hear a few interesting talks and to present a poster on behalf of CMS, about the search for the Standard Model Higgs boson.
Posters are what they sound like -big, illustrated sheets of paper. Many conferences have a "poster session" in which authors of the posters stand in front of their creation and discuss the details with colleagues and answer questions about the contents. Before the poster session, each poster is usually presented by the author with a short oral memo -five minutes each at PIC.
is an online repository of scientific papers in physics, astronomy, maths, cosmology, computer science, and a few other topics, where papers due to be published on scientific journals are submitted by the authors, and become quickly accessible for free to anybody before the peer-review process ran by the journals is over and they get printed there.
Patrick Draper is a graduate student in physics at the University of Chicago and Argonne National Lab. He is a native of Illinois and lives in Hyde Park, Chicago with his wife Karen and parrot Felix, to whom he is grateful for their love, patience, and correcting his sign errors. He is a supporter of the international effort to put a muon collider on Mars, and is waiting for NASA to return his phone calls.
I asked Patrick to write here about his studies on the discovery reach for a MSSM Higgs boson after I saw his paper on the arxiv a month ago, and am now glad I did. Enjoy!