Grad Talk Spring 2016

Date: 2016-03-06
Distribution of the razor variable M_R
Distribution of the razor variable \(M_R\)

I gave a grad talk to the physics department on Friday, March 4, on my new project, searching for dark matter at a future 100 TeV proton-proton collider using razor variables.

Razor variables were introduced in 2010,1 as a means of dealing with QCD backgrounds in squark and gluino searches. The basic principle is this: if we have events with substantial amounts of missing energy (such as events with dark matter production - the dark matter escapes the detector entirely), then we cannot completely reconstruct what happened in the collision, that is, we cannot get to the center-of-mass frame - we just do not have enough information. But for a particular kind of process, we can reasonably approximate it. Suppose we have pair production of two nearly mass-degenerate particles \(S_1\) and \(S_2\), which decay respectively into \(Q_1\chi_1\) and \(Q_2\chi_2\), with \(\chi_{1,2}\) being invisible. If we further assume that \(S_{1,2}\) are produced at threshold, that is, all the energy from the incoming particles has been used to produce \(S_{1,2}\), with no leftover energy to give them kinetic energy. Under these condidtions, we can perform a boost to a razor frame, which approximates the center-of-mass frame reasonably well.

The process that I am studying is the pair production of 1 TeV higgsinos, that decay to 100 GeV binos via intermediate Z- and higgs bosons. The higgsinos are nearly mass degenerate, so the razor variables do help in cutting away at the background.

There has also been a recent paper proposing super-razor variables, which improves upon the original razor variables for searches with hard initial state radiation, such as monojet searches.2 This paper gives a nice explanation of razor variables as well.

You can download my presentation here: PDF version.

  1. Kinematical variables towards new dynamics at the LHC

  2. Super-Razor and Searches for Sleptons and Charginos at the LHC