UsingMT2to distinguish dark matter stabilization symmetries

Abstract

We examine the potential of using colliders to distinguish models with parity (Z 2 ) stabilized dark matter (DM) from models in which the DM is stabilized by other symmetries, taking the latter to be a Z 3 symmetry for illustration. The key observation is that a heavier mother particle charged under a Z 3 stabilization symmetry can decay into one or two DM particles along with Standard Model (SM) particles. This can be contrasted with the decay of a mother particle charged under a parity symmetry; typically, only one DM particle appears in the decay chain. The arXiv:1003.0899 studied the distributions of visible invariant mass from the decay of a single such mother particle in order to highlight the resulting distinctive signatures of Z 3 symmetry versus parity symmetry stabilized dark matter candidates. We now describe a complementary study which focuses on decay chains of the two mother particles which are necessarily present in these events.We also include in our analyss the missing energy/momentum in the event. For the Z 3 symmetry stabilized mothers, the resulting inclusive final state can have two, three or four DM particles. In contrast, models with Z 2 symmetry can have only two. We show that the shapes and edges of the distribution of M T 2 -type variables, along with ratio of the visible momentum/energy on the two sides of the event, are powerful in distinguishing these different scenarios. Finally we conclude by outlining future work which focus on reducing combinatoric ambiguities from reconstructing multi-jet events. Increasing the reconstruction efficiency can allow better reconstruction of events with two or three dark matter candidates in the final state.

Strategies for probing nonminimal dark sectors at colliders: The interplay between cuts and kinematic distributions

“…For example, it has been shown that DDM ensembles can give rise to statistically significant deviations from the kinematic distributions associated with traditional, single-particle dark-matter candidates at colliders [6], at direct-detection experiments [7], and at cosmicray detectors [8]. Similar analyses have also been performed for other non-minimal dark-matter scenarios in the context of direct detection [4], indirect detection [9], and collider searches [10][11][12]. However, in general, it is also important to investigate the effects of correlations between kinematic variables and their impact on distribution shapes.…”

“…For example, the shapes of the M T 2 distributions associated with DDM ensembles with larger values of γ peak at lower values of M T 2 while still retaining a significant tail which extends out to the kinematic endpoint at M max T 2 = m φ . For large ∆m, the individual contributions to the distributions from events with different values of m a and m b can be independently resolved, as shown in the right panel of the figure, and a "kink" behavior arises similar to that which arises in the case in which multiple invisible particles are produced from a single decay chain [11]. By contrast, for small ∆m, these contributions cannot be resolved, and the tail of the resulting distribution appears smooth.…”

Distinguishing dynamical dark matter at the LHC

“…Of course, in cases in which only a small number of the χ n are kinematically accessible in ψ decays, these invariant-mass distributions are distinguished by the presence of multiple kinematic edges. Note that similar features arise in other contexts as well, most notably that in which a parent particle can decay into final states involving different multiplicities of the same stable dark-matter particle [5,6]. By contrast, in cases in which the number of kinematically-accessible χ n is large and the decay phenomenology of the ψ particles depends more sensitively on the full structure of the DDM ensemble, qualitatively different features emerge.…”

Constrained S ^ min $$ \sqrt{{\widehat{S}}_{\min }} $$ and reconstructing with semi-invisible production at hadron colliders

“…Shape of the visible invariant mass can effectively carry informations on topology along with the mass spectrum [9] of the decay chain. Underlying DM stabilising symmetry can also be probed [10][11][12] using kinematic edge and cusp in the invariant mass distributions and from the shapes of transverse mass variable M T 2 . Even the assumption of one particular underlying symmetry allows some fixed number of different topologies from which the correct one can be identified comparing suitable kinematic variables [13].…”