Dark-matter-spin effects at future e+e− colliders (original) (raw)
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Identifying the nature of dark matter at e−e+ colliders
Physical Review D, 2017
In this work, we consider the process e + + e − → bb + / E T , at the future electron-positron colliders such as the International Linear Collider and Compact Linear Collider, to look for the dark matter (DM) effect and identify its nature at two different centre-of-mass energies Ec.m. = 500 GeV and 1 TeV. For this purpose, we take two extensions of the standard model, in which the DM could be a real scalar or a heavy right-handed neutrino (RHN) similar to many models motivated by neutrino mass. In the latter extension, the charged leptons are coupled to the RHNs via a lepton flavor violating interaction that involves a charged singlet scalar. After discussing different constraints, we define a set of kinematical cuts that suppress the background, and generate different distributions that are useful in identifying the DM nature. The use of polarized beams (like the polarization P (e − , e +) = [+0.8, −0.3] at the International Linear Collider) makes the signal detection easier and the DM identification more clear, where the statistical significance gets enhanced by twice (five times) for scalar (RHN) DM.
LHC Dark Matter Working Group: Next-generation spin-0 dark matter models
Physics of the Dark Universe, 2019
Dark matter (DM) simplified models are by now commonly used by the ATLAS and CMS Collaborations to interpret searches for missing transverse energy (E miss T). The coherent use of these models sharpened the LHC DM search program, especially in the presentation of its results and their comparison to DM direct-detection (DD) and indirectdetection (ID) experiments. However, the community has been aware of the limitations of the DM simplified models, in particular the lack of theoretical consistency of some of them and their restricted phenomenology leading to the relevance of only a small subset of E miss T signatures. This document from the LHC Dark Matter Working Group identifies an example of a next-generation DM model, called 2HDM+a, that provides the simplest theoretically consistent extension of the DM pseudoscalar simplified model. A comprehensive study of the phenomenology of the 2HDM+a model is presented, including a discussion of the rich and intricate pattern of mono-X signatures and the relevance of other DM as well as non-DM experiments. Based on our discussions, a set of recommended scans are proposed to explore the parameter space of the 2HDM+a model through LHC searches. The exclusion limits obtained from the proposed scans can be consistently compared to the constraints on the 2HDM+a model that derive from DD, ID and the DM relic density. Sensitivity studies 8.1 Mono-Higgs study 8.2 Mono-Z study 8.3 Sensitivity of other mono-X channels 9 Constraints from other DM experiments 9.1 DD experiments 9.2 ID experiments 10 DM relic density 10.1 Calculation 10.2 Scan results 11 Proposed parameter scans 11.1 Scan in the M a , M H = M A = M H ± plane 11.2 Scan in the M a-tan β plane 11.3 Scans in sin θ 11.4 Scan in m χ A Recasting procedure B Distributions of the tt + E miss T signal in the 2HDM+s model C Details on the MC generation C.1 Four-top signature C.2 Mono-Higgs signature C.3 Mono-Z signature C.4 Heavy flavour signatures D Details on the mono-Higgs sensitivity study-1
Searching for dark matter at colliders
The European Physical Journal C, 2015
Dark Matter (DM) detection prospects at future e + e − colliders are reviewed under the assumption that DM particles are fermions of the Majorana or Dirac type. Although the discussion is quite general, one will keep in mind the recently proposed candidate based on an excess of energetic photons observed in the center of our Galaxy with the Fermi-LAT satellite. In the first part we will assume that DM interactions are mediated by vector bosons, Z or Z. In the case of Z-boson Direct Detection limits force only axial couplings with the DM. This solution can be naturally accommodated by Majorana DM but is disfavored by the GC excess. Viable scenarios can be instead found in the case of Z mediator. These scenarios can be tested at e + e − colliders through ISR events, e + e − → X X + γ. A sensitive background reduction can be achieved by using highly polarized beams. In the second part scalar particles, in particular Higgs particles, have been considered as mediators. The case of the SM Higgs mediator is excluded by limits on the invisible branching ratio of the Higgs. On the contrary particularly interesting is the case in which the DM interactions are mediated by the pseudoscalar state A in two Higgs-doublet model scenarios. In this last case the main collider signature is e + e − → H A, H → hh, A → X X.
Journal of Cosmology and Astroparticle Physics, 2016
In this work we show how the inclusion of dark matter (DM) direct detection upper bounds in a theoretically consistent manner can affect the allowed parameter space of a DM model. Traditionally, the limits from DM direct detection experiments on the elastic scattering cross section of DM particles as a function of their mass are extracted under simplifying assumptions. Relaxing the assumptions related to the DM particle nature, such as the neutron to proton ratio of the interactions, or the possibility of having similar contributions from the spin independent (SI) and spin dependent (SD) interactions can vary significantly the upper limits. Furthermore, it is known that astrophysical and nuclear uncertainties can also affect the upper bounds. To exemplify the impact of properly including all these factors, we have analysed two well motivated and popular DM scenarios: neutralinos in the NMSSM and a Z ′ portal with Dirac DM. We have found that the allowed parameter space of these models is subject to important variations when one includes both the SI and SD interactions at the same time, realistic neutron to proton ratios, as well as using different self-consistent speed distributions corresponding to popular DM halo density profiles, and distinct SD structure functions. Finally, we provide all the necessary information to include the upper bounds of SuperCDMS and LUX taking into account all these subtleties in the investigation of any particle physics model. The data for each experiment and example codes are available at this site http://goo.gl/1CDFYi, and their use is detailed in the appendices of this work.
Update of the direct detection of dark matter and the role of the nuclear spin
Physical Review D, 2001
We update our exploration of the minimal supersymmetric standard model 共MSSM兲 parameter space at the weak scale where new accelerator and cosmological constraints are respected. The dependence of weakly interacting massive particle nucleon cross sections on parameters of the MSSM, uncertainties of the nucleon structure and other theoretical assumptions such as universality and coannihilation are considered. In particular, we find that the coannihilation does not have a significant effect on our analysis in certain regions which are allowed even with coannihilation. The new cosmological constraint on the relic neutralino density used in the form 0.1⬍⍀ h 2 0 ⬍0.3 also does not significantly affect the regions of allowed neutralino-nucleon cross sec- tions. We notice that for nuclear targets with spin the spin-dependent interaction may determine the lower bound for the direct detection rate when the cross section of the scalar interaction drops below about 10 ⫺12 pb.
Theoretical expectations for dark matter detection at the LHC
I present an overview of theoretical expectations for detection of dark matter (DM) at the LHC, concentrating entirely on supersymmetric candidates. En route, I present a unified theory which explains dark matter signals at indirect and direct detection experiments. While direct DM detection is likely impossible at LHC, detection of SUSY matter states is robust, where LHC with \sqrt{s}=7 TeV and 1fb^{-1} can access m(gluino) 1 TeV for m(squark) m(gluino), and m(gluino) 640 GeV for m(squark)>> m(gluino). Models with well-tempered neutralinos will soon be tested by Xenon-100/LUX, and should provide a distinctive mass edge at LHC in the m(l+l-) distribution. In the case of SUSY, neutralino dark matter now seems highly disfavored by both the magnitude of the dark matter density, and also the gravitino problem. Alternatively, the PQMSSM yields a solution to the strong CP problem, provides all the benefits of SUSY, and solves several cosmological problems. Predictions for SUSY parti...
Probing dark forces and light hidden sectors at low-energy e+e- colliders
Physical Review D, 2009
A dark sector -- a new non-Abelian gauge group Higgsed or confined near the GeV scale -- can be spectacularly probed in low-energy e+e- collisions. A low-mass dark sector can explain the annual modulation signal reported by DAMA/LIBRA and the PAMELA, ATIC, and INTEGRAL observations by generating small mass splittings and new interactions for weak-scale dark matter. Some of these observations may be the first signs of a low-mass dark sector that collider searches can definitively confirm. Production and decay of O(GeV)-mass dark states is mediated by a Higgsed Abelian gauge boson that mixes kinetically with hypercharge. Existing data from BaBar, BELLE, CLEO-c, and KLOE may contain thousands of striking dark-sector events with a high multiplicity of leptons that reconstruct mass resonances and possibly displaced vertices. We discuss the production and decay phenomenology of Higgsed and confined dark sectors and propose e+e- collider search strategies. We also use the DAMA/LIBRA signal to estimate the production cross-sections and decay lifetimes for dark-sector states.
Iso-spin violating dark matter at the LHC
2012
We consider a toy model of dark matter (DM) with a gauge singlet Dirac fermion that has contact interactions to quarks that differ for right-handed up and down quarks. This is motivated by the isospin-violating dark matter scenario that was proposed to reconcile reported hints of direct DM detection with bounds from non-observation of the signal in other experiments. We discuss how the effects of isospin violation in these couplings can be observed at the LHC. By studying events with large missing transverse momentum (E T /), we show that the ratio of mono-photon and mono-jet events is sensitive to the ratio of the absolute values of the couplings to the up and down quarks, while a dedicated study of di-jet plus E T / events can reveal their relative sign. We also consider how our results are modified if instead of a contact interaction, a particle that mediates the interaction is introduced. Our methods have broad applicability to new physics that involves unequal couplings to up and down quarks.