Pair-produced heavy particle topologies:MSSM neutralino properties at the LHC from gluino/squark cascade decays

Abstract

Processes of the form $pp\to anything\to X_i{X}_j\to x\bar{x}+y\bar{y}(+\text{slashchar}E)$ are studied via a technique that may be viewed as an adaptation of time-honoured Dalitz plot analyses. $X_i$ and $X_j$ are new heavy states (with $i,j=\mathrm{1...}n$), which may be identical or distinct; and $x\bar{x}$ and $y\bar{y}$ are necessarily distinct Standard Model (SM) fermion pairs whose invariant masses can be measured. A Dalitz-like plot of said invariant masses, $M(x\bar{x})$ {\it vs.$} M(y\bar{y})$,exhibitsatopologyconnectedtothemassesandspecificdecaychainsof$X_i$and$X_j$.Asidefromrelativelyminordetails,observedpatternsconsistofacollectionofboxandwedgeshapes.Thiscollectionismodel-dependent:comparisonoftheobservedpatterntothepossibilitiesforaspecificmodelyieldsinformationonwhichnewparticlepaircombinationsareactuallybeingproduced,informationbeyondthatextractablefromconventionalone-dimensionalinvariantmassdistributions.ThetechniqueisillustratedviaapplicationtotheMinimalSupersymmetricStandardModel(MSSM)process$pp \to \tilde{g}\tilde{g},\tilde{g}\tilde{q},\tilde{q}\tilde{q} \to \widetilde{\chi}_i^0 \widetilde{\chi}_j^0 \to e^+ e^- + \mu^+ \mu^- (+ \slashchar{E})$.Heretheheavystatesareneutralinos$\widetilde{\chi}_i^0$($i=2,3,4$)--note$\widetilde{\chi}_1^0$isexcluded--whichareproducedingluino/squark($\tilde{g}$/$\tilde{q}$)cascadedecaychains.EvenwithfairlymodestexpectationsfortheLHCperformanceduringthefirstfewyears,thismethodstillprovidessubstantialinsightintotheneutralinomassspectrumandcouplingsifgluino/squarkmassesarerelativelylow($\simeq 400 \hbox{GeV}$).

Comments: 28 pages, LaTeX, 7 figures