Search for natural and split supersymmetry in proton-proton collisions at $$ \sqrt{s}=13 $$ TeV in final states with jets and missing transverse momentum

Abstract

A search for supersymmetry (SUSY) is performed in final states comprising one or more jets and missing transverse momentum using data from proton-proton collisions at a centre-of-mass energy of 13 TeV. The data were recorded with the CMS detector at the CERN LHC in 2016 and correspond to an integrated luminosity of 35.9 fb −1 . The number of signal events is found to agree with the expected background yields from standard model processes. The results are interpreted in the context of simplified models of SUSY that assume the production of gluino or squark pairs and their prompt decay to quarks and the lightest neutralino. The masses of bottom, top, and mass-degenerate light-flavour squarks are probed up to 1050, 1000, and 1325 GeV, respectively. The gluino mass is probed up to 1900, 1650, and 1650 GeV when the gluino decays via virtual states of the aforementioned squarks. The strongest mass bounds on the neutralinos from gluino and squark decays are 1150 and 575 GeV, respectively. The search also provides sensitivity to simplified models inspired by split SUSY that involve the production and decay of long-lived gluinos. Values of the proper decay length cτ 0 from 10 −3 to 10 5 mm are considered, as well as a metastable gluino scenario. Gluino masses up to 1750 and 900 GeV are probed for cτ 0 = 1 mm and for the metastable state, respectively. The sensitivity is moderately dependent on model assumptions for cτ 0 1 m. The search provides coverage of the cτ 0 parameter space for models involving long-lived gluinos that is complementary to existing techniques at the LHC. The CMS collaboration 33 IntroductionSupersymmetry (SUSY) [1][2][3][4] is an extension of the standard model (SM) of particle physics that introduces at least one bosonic (fermionic) superpartner for each fermionic (bosonic) SM particle, where the superpartner differs in its spin from its SM counterpart by one half unit. Supersymmetry offers a potential solution to the hierarchy problem [5,6], predicts unification of the gauge couplings at high energy [7][8][9], and provides a candidate for dark matter (DM). Under the assumption of R-parity [10] conservation, SUSY particles are expected to be produced in pairs at the CERN LHC and to decay to the stable, lightest SUSY particle (LSP). The LSP is assumed to be the neutralino χ 0 1 , a weakly interacting massive particle and a viable DM candidate [11,12]. So-called natural SUSY models, which invoke only a minimal fine tuning of the bare Higgs boson mass parameter, require only the gluino, third-generation squarks, and a higgsino-like χ 0 1 to have masses at or -1 - JHEP05(2018)025near the electroweak (EW) scale [13]. The interest in natural models is motivated by the discovery of a low-mass Higgs boson [14][15][16][17][18][19]. The characteristic signature of natural SUSY production at the LHC is a final state containing an abundance of jets originating from the hadronization of heavy-flavour quarks and significant missing transverse momentum p miss T . Split supersymmetry [20,21] does not add...

Direct detection and complementary constraints for sub-GeV dark matter

“…under the assumption that the scattering on the nucleons does not induce an additional momentum dependence. For an interaction mediated by a scalar S it is straightforward to calculate the nonrelativistic scattering cross section as [61] σ SI χN (Q 2 = 0) = 4) where g N denotes the coupling between S and the nucleus, i.e. g N = Ag p if isospin is conserved.…”

“…Here, ρ local χ and Φ LIS CR are the local interstellar DM density and the cosmic-ray flux, respectively, and T min CR is the minimal kinetic cosmic-ray energy needed to accelerate DM to kinetic energy T χ ; we take into account elastic scattering of cosmic-ray nuclei N = {p, 4 He} with DM, including in each case the same dipole form factor suppression as in ref. [28].…”

“…[28]. 4 D eff ∼ 8 kpc, finally, is an effective distance out to which we assume that the source density of CRDM is roughly the same as it is locally (which, for a standard DM distribution, corresponds to a sphere of about 10 kpc diameter). The scattering rate of relativistic CRDM particles in underground detectors is then determined as…”

“…Below the dashed black line, the Higgs portal by itself is insufficient to ever thermalise the dark sector with the SM. In addition to the overall limit (solid black line), we also separately show the regions of parameter space which are excluded due to D underproduction (grey), D overproduction (purple) and/or 4 He underproduction (blue), 4 He overproduction (pink). For m S 0.1m χ the thermal evolution is not fully captured by our calculation and thus the limits are only approximate, as indicated by the hatch pattern.…”

“…So far no unambiguous signal for new physics at the electroweak scale has been identified at the Large Hadron Collider (LHC) [3,4], despite seemingly intriguing theoretical arguments that have been brought forward why the appearance of new physics should be expected at these energies (with low-scale supersymmetry being the most popular example, see e.g. [5]).…”