Recent Results from the Search for New Phenomena at D0

TL;DR

This paper reports on multiple searches for new physics phenomena beyond the Standard Model at D0, including leptoquarks and supersymmetry, setting new mass limits and cross section constraints without observing any new particles.

Contribution

It presents the first comprehensive search for all three decay channels of first generation leptoquarks and the first search for third generation leptoquarks, along with supersymmetry searches with new limits.

Findings

No evidence for first generation leptoquarks below 175 GeV/c^2.

No evidence for third generation leptoquarks below 80 GeV/c^2.

Set upper limits on supersymmetry particle production cross sections.

Abstract

We present results from several new searches for physics beyond the Standard Model. We describe a search based on the scalar sum of the transverse energy of the event, a global quantity nearly independent of the event topology. We summarize our searches for first generation leptoquarks into all three decay channels, eq eq, eq nu q, and nu q nu q, and note that this is the first time that the triumvirate of decay channels has been searched. We do not find any evidence for production of first generation leptoquarks and set a lower limit on the mass of the leptoquark of 175 GeV/c^2, assuming the decay is exclusively into eq eq. We also present results from the first search for a third generation leptoquark with charge = +/- 1/3. Again, we find no evidence for its existence for a mass less than 80 GeV/c^2. Finally, we discuss one of our searches for supersymmetry, specifically the pair-production of selectrons, sneutrinos, and chi_2^0 where the decay yields final states with two photons plus missing transverse energy. We set limits on the production cross section ranging from 1 pb to 400 fb, depending on the mass. This analysis also sets a model-independent upper limit on the cross section times branching ratio to two photons + missing transverse energy + X of 185 fb at the 95% CL for transverse energy of the photons > 12 GeV with eta < 1.1 and missing transverse energy > 25 GeV.