R-symmetric Supersymmetric Model Research Articles

Long-lived bi\u03bdo at the LHC

We examine the detection prospects for a long-lived biνo, a pseudo-Dirac bino which is responsible for neutrino masses, at the LHC and at dedicated long-lived particle detectors. The biνo arises in U(1)R-symmetric supersymmetric models where the neutrino masses are generated through higher dimensional operators in an inverse seesaw mechanism. At the LHC the biνo is produced through squark decays and it subsequently decays to quarks, charged leptons and missing energy via its mixing with the Standard Model neutrinos. We consider long-lived biνos which escape the ATLAS or CMS detectors as missing energy and decay to charged leptons inside the proposed long-lived particle detectors FASER, CODEX-b, and MATHUSLA. We find the currently allowed region in the squark-biνo mass parameter space by recasting most recent LHC searches for jets+ . We also determine the reach of MATHUSLA, CODEX-b and FASER. We find that a large region of parameter space involving squark masses, biνo mass and the messenger scale can be probed with MATHUSLA, ranging from biνo masses of 10 GeV-2 TeV and messenger scales 102−11 TeV for a range of squark masses.

Searching for sgluons in multitop events at a center-of-mass energy of 8 TeV

AbstractLarge classes of new physics theories predict the existence of new scalar states, commonly dubbed sgluons, lying in the adjoint representation of the QCD gauge group. Since these new fields are expected to decay into colored Standard Model particles, and in particular into one or two top quarks, these theories predict a possible enhancement of the hadroproduction rate associated with multitop final states. We therefore investigate multitop events produced at the Large Hadron Collider, running at a center-of-mass energy of 8 TeV, and employ those events to probe the possible existence of color adjoint scalar particles. We first construct a simplified effective field theory motivated byR-symmetric supersymmetric models where sgluon fields decay dominantly into top quarks. We then use this model to analyze the sensitivity of the Large Hadron Collider in both a multilepton plus jets and a single lepton plus jets channel. After having based our event selection strategy on the possible presence of two, three and four top quarks in the final state, we find that sgluon-induced new physics contributions to multitop cross sections as low as 10-100 fb can be excluded at the 95% confidence level, assuming an integrated luminosity of 20 fb−1. Equivalently, sgluon masses of about 500–700 GeV can be reached for several classes of benchmark scenarios.

Electroweak baryogenesis inR-symmetric supersymmetry

We demonstrate that electroweak baryogenesis can occur in a supersymmetric model with an exact R-symmetry. The minimal R-symmetric supersymmetric model contains chiral superfields in the adjoint representation, giving Dirac gaugino masses, and an additional set of "R-partner" Higgs superfields, giving R-symmetric \mu-terms. New superpotential couplings between the adjoints and the Higgs fields can simultaneously increase the strength of the electroweak phase transition and provide additional tree-level contributions to the lightest Higgs mass. Notably, no light stop is present in this framework, and in fact, we require both stops to be above a few TeV to provide sufficient radiative corrections to the lightest Higgs mass to bring it up to 125 GeV. Large CP-violating phases in the gaugino/higgsino sector allow us to match the baryon asymmetry of the Universe with no constraints from electric dipole moments due to R-symmetry. We briefly discuss some of the more interesting phenomenology, particularly of the of the lightest CP-odd scalar.

μtoeinR-symmetric supersymmetry

We demonstrate that mu/e slepton mixing is significantly more restricted than previously thought within the already remarkably flavor-safe R-symmetric supersymmetric standard model. We calculate bounds from mu to e gamma, mu to 3e and, most importantly, mu to e conversion. The process mu to e conversion is significantly more restrictive in R-symmetric models since this process can occur through operators that do not require a chirality-flip. We delineate the allowed parameter space, demonstrating that maximal mixing is rarely possible with weak scale superpartners, while O(0.1) mixing is permitted within most of the space. The best approach to find or rule out mu/e mixing in R-symmetric supersymmetric models is a multi-pronged attack looking at both mu to e conversion as well as mu to e gamma. The redundancy eliminates much of the parameter space where one process, but not both processes, contain amplitudes that accidentally destructively interfere. We briefly discuss implications for searches of slepton flavor violation at the LHC.

Flavor in supersymmetry with an extendedRsymmetry

We propose a new solution to the supersymmetric flavor problem without flavor-blind mediation. Our proposal is to enforce a continuous or a suitably large discrete R-symmetry on weak scale supersymmetry, so that Majorana gaugino masses, trilinear A terms, and the μ term are forbidden. We find that replacing the minimal supersymmetric standard model with an R-symmetric supersymmetric model allows order one flavor-violating soft masses, even for squarks of order a few hundred GeV. The minimal R-symmetric supersymmetric model contains Dirac gaugino masses and R-symmetric Higgsino masses with no left-right mixing in the squark or slepton sector. Dirac gaugino masses of order a few TeV with vanishing A terms solve most flavor problems, while the R-symmetric Higgs sector becomes important at large tanβ. ∈ K can be accommodated if CP is preserved in the SUSY breaking sector, or if there is a moderate flavor degeneracy, which can arise naturally. ∈'/∈, as well as neutron and electron electric dipole moments, are easily within experimental bounds. The most striking phenomenological distinction of this model is the order one flavor violation in the squark and slepton sector, while the Dirac gaugino masses tend to be significantly heavier than the corresponding squark and slepton masses.

QCD corrections toK−K̄ mixing in R-symmetric supersymmetric models

The leading-log QCD corrections to K? mixing in R-symmetric supersymmetric models are computed using effective field theory techniques. The spectrum topology where the gluino is significantly heavier than the squarks is motivated and focused on. It is found that, like in the MSSM, QCD corrections can tighten the kaon mass difference bound by roughly a factor of three. CP violation is also briefly considered, where QCD corrections can constrain phases to be as much as a factor of ten smaller than the uncorrected value.