SUSY at the ILC and solving the LHC inverse problem
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ELEMENTARY PARTICLES AND FIELDS Theory
SUSY at the ILC and Solving the LHC Inverse Problem* J. S. Gainer** SLAC National Accelerator Laboratory, Stanford, USA Received September 18, 2008; in final form, Febryary 10, 2009
Abstract—Recently a large-scale study of points in the MSSM parameter space which are problematic at the Large Hadron Collider (LHC) has been performed. This work was carried out in part to determine whether the proposed International Linear Collider (ILC) could be used to solve the LHC inverse problem. The results suggest that while the ILC will be a valuable tool, an energy upgrade may be crucial to its success, and that, in general, precision studies of the MSSM are more difficult at the ILC than has generally been believed. PACS numbers: 11.30.Pb, 13.66.Hk DOI: 10.1134/S1063778809090208
1. INTRODUCTION: THE LHC INVERSE PROBLEM As we all know, the LHC is scheduled to turn on this year. This means that we are entering (hopefully) an exciting era of discovery in fundamental physics. Obviously the biggest question is “Will the LHC discover new physics?” Let us assume the answer to this question is “yes” (if the answer is “no”, there will not be much for Beyond the Standard Model phenomenologists to talk about). It would, of course, not be sufficient to know that there is new physics; we would want to learn as much about the new physics as possible. In fact, this would not sate our curiosity. Any model of new physics contains some set of parameters and, hence, has some “parameter space”. We would like to know the values of these model parameters, i.e., we would like to determine which point in the model’s parameter space is realized in nature. It is our goal to determine how difficult this is to do. Of course one cannot do this for every possible model of new physics; there are far too many. We will therefore specialize to the case of the Minimal Supersymmetric Standard Model (MSSM), as Super symmetry (SUSY) is a very popular possibility for new physics, and the MSSM is the simplest supersymmetric extension of the Standard Model. Often when considering the MSSM one uses additional relations between parameters derived from a particular model of SUSY breaking. As we do not know which (if any) of these models is correct, we ∗ **
The text was submitted by the author in English. E-mail: [email protected]
would like to consider the MSSM in essentially full generality. However, the full MSSM has well over one hundred parameters. This gives us a parameter space with too many dimensions to sample randomly with any thoroughness. Fortunately, for many collider applications we only need to consider a smaller set of MSSM Lagrangian parameters: weak scale gaugino masses, weak scale sfermion masses, µ term tan β, trilinear couplings (At,b,τ ). This is still a large number of parameters (around 15–20, depending upon what assumptions one makes). Following the work of Arkani-Hamed, Kane, Thaler, and Wang (AKTW) [1] in studying the “LHC Inverse Problem” (described below), we think of an experiment, or rather the i
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