摘要 :
The requirement of electroweak naturalness in simple supersymmetric models implies the existence of a cluster of four light Higgsinos with a mass ～ 100 – 300 ? ? GeV , the lighter the better. While such light compressed spectra ...
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The requirement of electroweak naturalness in simple supersymmetric models implies the existence of a cluster of four light Higgsinos with a mass ～ 100 – 300 ? ? GeV , the lighter the better. While such light compressed spectra may be challenging to observe at the LHC, the International Linear e + e ? Collider (ILC) with s > 2 m Higgsino would serve as both a SUSY discovery machine and a precision microscope. We study Higgsino pair production signatures at the ILC based on a full, geant4-based simulation of the ILD detector concept. We examine several benchmark scenarios that may be challenging for discovery at the HL-LHC due to mass differences between the Higgsino states between 20 and 4?GeV. Assuming s = 500 ? ? GeV and 1000 ? ? fb ? 1 of integrated luminosity, the individual Higgsino masses can be measured to 1%–2% precision in the case of the larger mass differences, and at the level of 5% for the smallest mass difference case. The Higgsino mass splittings are sensitive to the electroweak gaugino masses and allow extraction of gaugino masses to ～ 3 % – 20 % (depending on the model). Extrapolation of gaugino masses via renormalization group running can test the hypothesis of gaugino mass unification. We also examine a case with natural generalized mirage mediation, where the unification of gaugino masses at an intermediate scale apparently gives rise to a natural SUSY spectrum somewhat beyond the reach of HL-LHC.
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摘要 :
In supersymmetric extensions of the Standard Model, higgsino-like charginos and neutralinos are preferred to have masses of the order of the electroweak scale by naturalness arguments. Such light χ_1~0, χ_2~0 and χ_1~± states ...
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In supersymmetric extensions of the Standard Model, higgsino-like charginos and neutralinos are preferred to have masses of the order of the electroweak scale by naturalness arguments. Such light χ_1~0, χ_2~0 and χ_1~± states can be almost mass degenerate, and their decays are then difficult to observe at colliders. In addition to the generic naturalness argument, light higgsinos are well motivated from a top-down perspective. For instance, they arise naturally in certain models of hybrid gauge-gravity mediation. In the present analysis, we study two benchmark points which have been derived in the framework of such a model, which exhibit mass differences of O(GeV) in the higgsino sector. For chargino-pair and neutralino associated production with initial-state photon radiation, we simulate the detector response and determine how accurately the small mass differences, the absolute masses and the cross sections can be measured at the International Linear Collider. Assuming that 500 fb~(?1) has been collected at each of two beampolarisations P(e~+, e~?) = (±30 %,?80 %), we find that the mass differences can be measured to 40–300 MeV, the cross sections to 2–5 %, and the absolute masses to 1.5–3.3 GeV, where the range of values correspond to the different scenarios and channels. Based on these observables we perform a parameter fit in the MSSM, from which we infer that the higgsino mass parameter μ can be measured to a precision of about ?_μ = 2–7 GeV. For the electroweak gaugino mass parameters M_1, M_2, which are chosen in the multi-TeV range, a narrow region is compatible with the measurements. For both parameters independently, we can determine a lower bound.
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In this study, the sensitivity of future lepton colliders to weakly interacting massive particles (WIMP) dark matter is evaluated assuming WIMP pair production accompanied by a photon from initial state radiation, through which th...
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In this study, the sensitivity of future lepton colliders to weakly interacting massive particles (WIMP) dark matter is evaluated assuming WIMP pair production accompanied by a photon from initial state radiation, through which the process can be identified. A full detector simulation for the International Large Detector (ILD) concept at the International Linear Collider (ILC) is performed for a center-of-mass energy of 500?GeV. Energy scales of up to 3?TeV can be tested for different effective operators for WIMP masses almost up to half the center-of-mass energy. The sensitivity benefits from the polarized beams, which can reduce the main SM background from neutrino pair production substantially. In addition, systematic uncertainties are shown to be significantly reduced by combining data with several different polarization configurations. In comparison to a previous study, the reconstruction of the forward detectors has been improved, and the systematic uncertainties are fully treated. The results are also extrapolated to other center-of-mass energies, luminosities, and beam polarizations. This allows us to provide results for the full ILC program, i.e., from 250?GeV to 1?TeV, as well as to give approximate results for other planned lepton colliders.
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摘要 :
We investigate the prospects for detecting and measuring the parameters of WIMP dark matter in a modelindependent way at the International Linear Collider. The signal under study is direct WIMP pair production with associated init...
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We investigate the prospects for detecting and measuring the parameters of WIMP dark matter in a modelindependent way at the International Linear Collider. The signal under study is direct WIMP pair production with associated initial state radiation e~+e~? →χχγ. The analysis accounts for the beam energy spectrum of the ILC and the dominant machine induced backgrounds. The influence of the detector parameters are incorporated by full simulation and event reconstruction within the framework of the ILD detector concept. We show that by using polarised beams, the detection potential is significantly increased by reduction of the dominant SM background of radiative neutrino production e~+e~? →ν νγ. The dominant sources of systematic uncertainty are the precision of the polarisation measurement and the shape of the beam energy spectrum. With an integrated luminosity of L = 500 fb~(?1) the helicity structure of the interaction involved can be inferred, and the masses and cross sections can be measured with a relative accuracy of the order of 1 %.
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