Low energy supersymmetry with a neutralino LSP and the CDFeeγγ+ETevent

Abstract

We present a refined and expanded analysis of the CDF eeγγ + / E T event as superpartner production, assuming the lightest neutralino is the lightest supersymmetric particle. A general low-energy Lagrangian is constrained by a minimum cross section times branching ratio into two electrons and two photons, kinematics consistent with the event, and LEP1-LEP130 data. We examine how the supersymmetric parameters depend on the kinematics, branching ratios and experimental predictions with a selectron interpretation of the event, and discuss to what extent these are modified by other interpretations. Predictions for imminent CERN LEP upgrades and the present and future Fermilab Tevatron are presented. Finally, we briefly discuss the possible connection to other phenomena including a light stop, the neutralino relic density, the shift in R b and the associated shift in α s , and implications for the form of the theory. * Supported mainly by a INFN postdoctoral fellowship, Italy.

How to interpret a tau excess at LEP2 within the MSSM

“…One compelling explanation was the production and decay of selectron pairs, with each selectron decaying in the cascadeẽ → e N 2 (→ γ N 1 ) [13]. However, upon further analysis, the electron candidate seems to be inconsistent with an electron produced at the production vertex.…”

Low-energy supersymmetry and its phenomenology

“…In a small range of parameter space, it is possible that several of the next-to-lightest supersymmetric particles are sufficiently degenerate in mass such that each one behaves as the NLSP. 8 In this case, these particles are called co-NLSP's [56]. Different choices for the identity of the NLSP and its decay rate lead to a variety of distinctive supersymmetric phenomenologies [57,58].…”

“…In the model of ref. [58], the χ In this picture, the pair production of supersymmetric particles often yields two photons plus associated missing energy.…”

Report of the Supersymmetry Theory Subgroup

“…Since the Goldstino couplings (18) are suppressed compared to electroweak and strong interactions, decay to the Goldstino is only relevant for the lightest standard-model superpartner (NLSP).…”

“…This has been interpreted in several ways [15], [16], [17], [18] and later with additional variations [19], [20], [21]. The main two paths are whether the LSP is the lightest neutralino [15], [22], or a nearly massless gravitino [16,17,18,19,20] or axino [21]. In the gravitino or axino case the LSP is not a candidate for cold dark matter, SUSY can have no effect on R b or α Z s or BR(b → sγ), and stops and gluinos are not being observed at FNAL.…”