Contur Toolchain

The software tool chain used in the Contur `white paper’. Other generators and interfaces may also be substitued for e.g. Feynrules or Herwig7.

Contur exploits three important developments to survey existing measurements and set limits on new physics.

  1. SM predictions for differential and exclusive, or semi-exclusive, final states are made using sophisticated calculational software, often embedded in Monte Carlo generators capable of simulating full, realistic final states [25]. These generators now incorporate matrix-elements for higher-order processes matched to logarithmic parton showers, and successful models of soft physics such as hadronisation and the underlying event. They are also capable of importing new physics models into this framework, thus allowing the rapid prediction of their impact on a wide variety of final states simultaneously. In this paper we make extensive use of these capabilities within Herwig 7 [23][21].
  2. As the search for many of the favoured BSM scenarios has been unsuccessful, there has been a move toward “simplified models” of new physics [19][17], which aim to be as generic as possible and which provide a framework for interpreting BSM signatures with a minimal amount of new particles, interactions and model assumptions. The philosophy is similar to an “effective lagrangian” approach in which effective anomalous couplings are introduced to describe new physics, but is more powerful, as such simplified models also include new particles, and thus can remain useful up to and beyond the scale of new physics — a region potentially probed by LHC measurements.
  3. The precision measurements from the LHC have mostly been made in a manner which minimises their model-dependence. That is, they are defined in terms of final-state signatures in fiducial regions well-matched to the acceptance of the detector. Many such measurements are readily available for analysis and comparison in the library [24].

These three developments together make it possible to efficiently bring the power of a very wide range of data to bear on the search for new physics. While such a generic approach is unlikely to compete in terms of speed and sensitivity with a search optimised for a specific theory, the breadth of potential signatures and models which can be covered makes it a powerful complementary approach. [1] On the one hand, any theory seeking to explain a new signature or anomaly in the data may predict a BSM signal in other final states, which should be checked against data this way. On the other hand, if no BSM physics emerges, a model-independent and systematic approach becomes mandatory to exclude new physics models or narrow down the corresponding model parameter space.

[1]Limits from existing searches can sometimes be applied to new models, for example by accessing archived versions of the original analysis code and detector simulation via the RECAST [37] project, or by independent implementations of experimental searches, see, for example, Refs. [35][39][53][55][22].