Jason St. John
Graduate Student
Email:
Website: http://buphy.bu.edu/~stjohn
Availability (office hours): PRB 4th floor in the CMS lab
or
PRB 268 in my office-icle
Research Interests:
Experimental quantum chromodynamics at CMS. That means jets physics, where jets are the sprays of particles which result from quarks and gluons smacking each other free of the protons which went into the collision. Just measuring the spectrum of jet momenta transverse to the beam pipe will be nontrivial, since the energy deposited in the calorimeter cannot all be collected, and software must be made to decide which energy deposits should be considered as parts of which jets. Once that’s under control, there are number of simple measurements to make using the collected events and their assigned jets. These are as simple as the ratio between the numbers of events with two big jets and those with three. Likewise we can examine the distributions and correlations of angles between jets; reconstructed di- and tri-jet (and so on) masses; the transverse momentum distributions of events with specific jet topologies (cases when certain types of gluon and quark interactions probably happened); and the distribution of energy with jets. All such measurements can be predicted by and compared to QCD calculations using Monte Carlo methods.
If there’s ever time, maybe something a little more fun:
Measurement of anomalous trilinear gauge couplings (the non-Abelian structure of the electroweak vector gauge bosons). These could be measured in diboson LHC events where one W boson decays leptonically (easier to sift out), and the other decays to two jets (higher cross section). It will be important to beat down QCD jets faking the hadron W boson decay (so that’s exciting to learn about for me). The quartic couplings are also on my mind, but trickier to measure. What about
Z > ZW+W
or
W -> WZZ
which will require an understanding of jet multiplicity in QCD, and being able to pay the price of smaller coupling constants, nastier phase space, and possibly some helicity price as well. Maybe helicity will help, actually.
If there is an energy frontier resonance (read: “a new subatomic particle”) which is responsible for electroweak symmetry breaking, this analysis will be very sensitive to it (I’m looking at you, Higgs).
Education:
BA, Physics, Harvard 2001
Jets all the way
