Discovering Baryon-Number Violating Neutralino Decays at the LHC

Abstract

Recently there has been much interest in the use of single-jet mass and jet substructure to identify boosted particles decaying hadronically at the LHC. We develop these ideas to address the challenging case of a neutralino decaying to three quarks in models with baryonic violation of R-parity. These decays have previously been found to be swamped by QCD backgrounds. We demonstrate for the first time that such a decay might be observed directly at the LHC with high significance, by exploiting characteristics of the scales at which its composite jet breaks up into subjets.The LHC's scope for the discovery of supersymmetry broken at the TeV scale [1][2][3][4][5] has generated much interest. Certainly, the potential prize is great: TeV-scale supersymmetry could solve several puzzling problems and answer a number of open questions in modern particle physics, such as the fine-tuning of the Higgs mass, the unification of forces at high energies and the nature of dark matter. Effort has mainly been concentrated on investigations into the discovery reach and possibility of parameter measurements in the Minimal Supersymmetric Standard Model (MSSM) and various more constrained versions featuring a weakly-interacting and stable Lightest Supersymmetric Particle (LSP), which gives a missing-energy signature. Candidates for the LSP include the lightest neutralino,χ 0 1 , and the gravitino. However, the gauge symmetries of the Standard Model (SM) also allow for dimension-four terms in the superpotential of the formswhich violate the R-parity that is imposed in the MSSM. Non-zero values for the couplings λ could imply drastically different phenomenologies for supersymmetry at the LHC, allowing for the decay of the LSP, or any heavier sparticle, directly to SM particles. Broadly speaking, we can classify the RPV models in terms of the dominant coupling λ and the identity of the Next-to-Lightest Supersymmetric Particle (NLSP), assuming that a gravitino is the LSP. The lepton-numberviolating (LV) couplings λ and λ ′ generally give MSSMlike signatures with missing energy from neutrinos and/or extra leptons in the decays of the NLSP. The exception is a slepton/sneutrino NLSP that decays into two quarks via a dominant λ ′ coupling. Scenarios such as these should be easy to extract from the SM backgrounds, as shown for a neutralino NLSP in [6].However, dominant baryon-number-violating (BV) couplings λ ′′ are more difficult to deal with, due to the large hadronic activity expected at the LHC, which threatens to drown decays such asχ 0 1 → qqq. The QCD background for jets with p T

Recombination algorithms and jet substructure: Pruning as a tool for heavy particle searches

“…(25), there is a enhancement at the lower cutoff in ∆R 12 due to the square root singularity arising from the change of variables, just as there was in the QCD result in Eq. (14). Thus the distribution in ∆R 12 is highly localized at the cutoff, which is a function of γ.…”

Stop reconstruction with tagged tops

“…Tagging W bosons in their decays to geometrically large jets [35][36][37][38] has been around in the LHC literature for quite a while, including its applications in searches for supersymmetry [39][40][41][42][43]. Higgs tags can be implemented in a similar manner, and as it turns out they show the best performance [16,17,19,[39][40][41][42][43][44][45] when based on the purely geometric C/A jet algorithm [46][47][48][49].…”

“…Tagging W bosons in their decays to geometrically large jets [35][36][37][38] has been around in the LHC literature for quite a while, including its applications in searches for supersymmetry [39][40][41][42][43]. Higgs tags can be implemented in a similar manner, and as it turns out they show the best performance [16,17,19,[39][40][41][42][43][44][45] when based on the purely geometric C/A jet algorithm [46][47][48][49]. Inspired by searches for very heavy resonances decaying to top pairs [52][53][54] several top taggers have been developed, again in the same spirit, but based on different jet algorithms as well as on jet shapes [18,19,[55][56][57][58][59][60][61][62][63].…”

Neutron electric dipole moment in CP violating BLMSSM

“…We can look for lepton number violation at the LHC, from the decays of right handed neutrinos [3,7]. The baryon number violation in the decays of squarks and gauginos [8] can also be detected at the LHC. For example, the baryon number violating decays of gluinos may give rise to channels with multi-tops and multi-bottoms [3].…”