Natural anomaly mediation from the landscape with implications for LHC SUSY searches

Supersymmetric models with the anomaly-mediated supersymmetry (SUSY) breaking (AMSB) form for soft SUSY breaking terms arise in two different settings: (1) extra-dimensional models where SUSY breaking occurs in a sequestered sector, and (2) <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mn>4</a:mn><a:mo>−</a:mo><a:mi>d</a:mi></a:math> models with dynamical SUSY breaking in a hidden sector where scalars gain masses of order the gravitino mass <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:msub><c:mi>m</c:mi><c:mrow><c:mn>3</c:mn><c:mo>/</c:mo><c:mn>2</c:mn></c:mrow></c:msub></c:math>, but gaugino masses and trilinear soft terms are assumed to be of the AMSB form. Both models run into serious conflicts with (1) LHC sparticle and Higgs mass constraints, (2) constraints from winolike weakly interacting massive particle dark matter searches, and (3) bounds from naturalness. These conflicts may be avoided by introducing minor changes to the underlying phenomenological models consisting of nonuniversal bulk scalar Higgs masses and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>A</e:mi></e:math> terms, providing a setting for natural anomaly mediation (nAMSB). In nAMSB, the wino is still expected to be the lightest of the gauginos, but the Higgsinos are expected to be the lightest electroweakinos (EWinos) in accord with naturalness. We examine what sorts of spectra are expected to emerge when nAMSB arises from a string landscape setting: While model 2 can only be natural for a Higgs mass <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msub><g:mi>m</g:mi><g:mi>h</g:mi></g:msub><g:mo>≲</g:mo><g:mn>123</g:mn><g:mtext> </g:mtext><g:mtext> </g:mtext><g:mi>GeV</g:mi></g:math>, model 1 can accommodate naturalness along with <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:msub><i:mi>m</i:mi><i:mi>h</i:mi></i:msub><i:mo>∼</i:mo><i:mn>125</i:mn><i:mtext> </i:mtext><i:mtext> </i:mtext><i:mi>GeV</i:mi></i:math> while still respecting LHC bounds on sparticle masses. We explore the LHC phenomenology of nAMSB models where we find that for Higgsino pair production, typically larger dilepton mass gaps arise from the soft dilepton-plus-jets signature than in models with gaugino mass unification. For wino-pair production, the higher <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msub><k:mi>m</k:mi><k:mrow><k:mn>3</k:mn><k:mo>/</k:mo><k:mn>2</k:mn></k:mrow></k:msub></k:math> portion of nAMSB parameter space is excluded by recent LHC bounds from gaugino pair production searches. We characterize the dominant LHC signatures arising from the remaining lower <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:msub><m:mi>m</m:mi><m:mrow><m:mn>3</m:mn><m:mo>/</m:mo><m:mn>2</m:mn></m:mrow></m:msub><m:mo>∼</m:mo><m:mn>90</m:mn><m:mi>–</m:mi><m:mn>200</m:mn><m:mtext> </m:mtext><m:mtext> </m:mtext><m:mi>TeV</m:mi></m:math> range of parameter space, which should be fully testable at high-luminosity LHC via EWino pair production searches. Published by the American Physical Society 2024