Progress review on the dark matter direct detection experiments

Subject Code:A05 A progress review article on the dark matter direct detection experiments,authored by Prof.Liu Jianglai(刘江来),Dr.Chen Xun(谌勋)and Prof.Ji Xiangdong(季向东,corresponding author)from the Shanghai Jiao Tong University,was published online in Nature Physics(2017,13:212—216)recently.

Have we found conclusive evidence for dark matter through direct detection experiments?

A WIMP-model-independent method is used to examine the existing evidence for low mass dark matter. Using XENON100＇s recent result of 224.6 live days × 34 kg exposure and PICASSO＇s result that was published in 2012, we have obtained constraints on the couplings │an│ 〈 0.4 and │ap│ 〈 0.3, corresponding to spin-dependent cross-sections of σ〈2.5×10^-38 cm2 and σp〈1.4×10^-38cm2 for a WIMP mass of 10 GeV/c2. It is shown that the spin-independent isospin-violating dark matter model also fails to reconcile the recent result from XENON100 with the positive results from DAMA, CoGeNT and CDMS-Ⅱ.

Probing inelastic signatures of dark matter detection via polarized nucleus

We investigate the inelastic signatures of dark matter-nucleus interactions,explicitly focusing on the ramifications of polarization,dark matter splitting,and the Migdal effect.Direct detection experiments,crucial for testing the existence of dark matter,encounter formidable obstacles,such as indomitable neutrino backgrounds and elusive determination of dark matter spin.To overcome these challenges,we explore the potential of polarized-target dark matter scattering,examining the impact of nonvanishing mass splitting,and the role of the Migdal effect in detecting dark matter.Our analysis demonstrates the valuable utility of the polarized triple-differential event rate as an effective tool for examining inelastic dark matter.It enables us to investigate angular and energy dependencies,providing valuable insights into the scattering process.

Simplified dark matter models with loop effects in direct detection and the constraints from indirect detection and collider search

We reexamine the simplified dark matter(DM) models with fermionic DM particle and spin-0 mediator.The DM-nucleon scattering cross sections in these models are low-momentum suppressed at tree-level,but receive sizable loop-induced spin-independent contribution.We perform one-loop calculations for scalar-type and twist-2 DM-quark operators,and complete two-loop calculations for scalar-type DM-gluon operator.Analyzing the looplevel contribution from new operators,we find that future direct detection experiments could be sensitive to a fraction of the parameter space.The indirect detection and collider search also provide complementary constraints on these models.

Status and Perspectives of Dark Matter Searches in China

In this paper,we give a review of direct detection searches reported by the DAMA(China as a Co-Ⅰ),and indirect detection searches reported by the ATIC(China as a Co-Ⅰ).We also outline the future plans of dark matter search in China.

An improved bound on accelerated light dark matter

Light(sub-GeV)dark matter has gained increasing interest in terms of direct detection.Accelerated dark matter is a promising candidate that can generate detectable nuclear recoil energy within the sub-GeV range.Because of the large kinetic energy,its interactions with the nucleus are predominantly governed by inelastic scattering,including quasi-elastic and deep inelastic scattering.In this work,we calculated the inelastic effects in dark matter-Earth scattering mediated by a vector particle.Our analysis revealed that the impact of inelastic scattering relies on the mediator mass and the kinetic energy spectrum of dark matter.The results exhibited considerable disparity:the upper bounds of the exclusion limit for the spin-independent cross-section between accelerated dark matter and nuclei via a heavy mediator differ by several tens of times when inelastic scattering is considered.

Dark matter direct search sensitivity of the PandaX-4T experiment

The Panda X-4T experiment, a 4-ton scale dark matter direct detection experiment, is being planned at the China Jinping Underground Laboratory. In this paper we present a simulation study of the expected background in this experiment. In a 2.8-ton fiducial mass and the signal region between 1-10 keV electron equivalent energy, the total electron recoil background is found to be 4.9 × 10^(-5) kg^(-1) d^(-1) keV^(-1). The nuclear recoil background in the same region is 2.8 × 10^(-7) kg^(-1) d^(-1) keV^(-1). With an exposure of 5.6 ton-years, the sensitivity of Panda X-4 T could reach a minimum spin-independent dark matter-nucleon cross section of 6 × 10^(-48) cm^2 at a dark matter mass of 40 Ge V/c^2.

Interpretation of XENON1T excess with MeV boosted dark matter

The XENON IT excess of keV electron recoil events may be induced by the scattering of electrons and long-lived particles with an MeV mass and high speed.We consider a tangible model composed of two scalar MeV dark matter(DM) particles,S_(A) and S_(B),to interpret the XENON IT keV excess via boosted S_(B).A small mass splitting m_(S_(A))-m_(S_(B))>0 is introduced,and the boosted S_(B) can be produced using the dark annihilation process of S_(A)S_(A)^(■)→φ→S_(B)S_(B)^(■) via a resonant scalar φ.S_(B)-electron scattering is intermediated by a vector boson X.Although the constraints from Big Bang nucleosynthesis,cosmic microwave background(CMB),and low-energy experiments set the X-mediated S_(B)-electron scattering cross section to be≤10^(-35)cm^(2),the MeV scale DM with a resonance enhanced dark annihilation today can still provide sufficient boosted S_(B) and induce the XENON1 T keV excess.The relic density of S_(B) is significantly reduced by the s-wave process S_(B)S_(B)^(■)→XX,which is permitted by the constraints from CMB and 21-cm absorption.A very small relic fraction of S_(B) is compatible with the stringent bounds on un-boosted S_(B)-electron scattering in DM direct detection,and the S_(A)-electron scattering is also allowed.

Effective field theory approach to lepto-philic self-conjugate dark matter

We study self-conjugate dark matter(DM)particles interacting primarily with Standard Model(SM)leptons in an effective field theoretical framework.We consider SM gauge-invariant effective contact interactions between Majorana fermion,real scalar and real vector DM with leptons by evaluating the Wilson coefficients appropriate for interaction terms up to dimension 8,and obtain constraints on the parameters of the theory from the observed relic density,indirect detection observations and from the DM-electron scattering cross-sections in direct detection experiments.Low energy LEP data has been used to study sensitivity in the pair production of low mass(≤80 GeV)DM particles.Pair production of DM particles of mass≥50 GeV in association with mono-photons at the proposed ILC has rich potential to probe such effective operators.

First dark matter search results from the PandaX-Ⅰ experiment

We report on the first dark-matter(DM)search results from PandaX-I,a low threshold dual-phase xenon experiment operating at the China JinPing Underground Laboratory.In the 37-kg liquid xenon target with 17.4 live-days of exposure,no DM particle candidate event was found.This result sets a stringent limit for low-mass DM particles and disfavors the interpretation of previously-reported positive experimental results.The minimum upper limit,3.7×10-44cm2,for the spin-independent isoscalar DM-particle-nucleon scattering cross section is obtained at a DM-particle mass of 49 GeV/c2at 90%confidence level.

Experimental search for dark matter in China

The nature of dark matter is one of the greatest mysteries in modern physics and astronomy.A wide variety of experiments have been carried out worldwide to search for the evidence of particle dark matter.Chinese physicists started experimental search for dark matter about ten years ago,and have produced results with high scientific impact.In this paper,we present an overview of the dark matter program in China,and discuss recent results and future directions.

PandaX limits on the light dark matter with a light mediator in the singlet extension of MSSM

Using the latest PandaX limits on the light dark matter(DM) with a light mediator, we check their implication on the parameter space of the general singlet extension of MSSM(without Z3 symmetry), which can have a sufficient DM self-interaction to solve the small-scale structure problem. We find that the PandaX limits can tightly constrain the parameter space, depending on the coupling λ between the singlet and doublet Higgs fields. For the singlet extension of MSSM with Z3 symmetry, the so-called NMSSM, we also demonstrate the PandaX constraints on its parameter space, which gives a light DM with the correct relic density but without sufficient self-interaction to solve the small-scale structure problem. We find that in NMSSM, the GeV dark matter with a sub-GeV mediator is tightly constrained.

Dark matter search at colliders and neutrino floor

The sensitivity of the direct detection of dark matter(DM)approaches the so-called neutrino floor,below which it is difficult to disentangle the DM candidate from the neutrino background.In this work,we consider the scenario that no DM signals are reported in various DM direct detection experiments and explore whether collider searches could probe DM below the neutrino floor.We adopt several simplified models in which the DM candidate couples to electroweak gauge bosons or leptons in the standard model only through high-dimensional operators.After including the RGE running effect,we investigate the constraints of direct detection,indirect detection,and collider searches.The collider search can probe light DM below the neutrino floor.Particularly,for the effective interaction of χχBμνB^μν,current data from the mono-photon channel at the 13 TeV LHC has already covered the entire parameter space of the neutrino floor.

Results of dark matter search using the full PandaX-Ⅱ exposure

We report the dark matter search results obtained using the full 132 ton·day exposure of the PandaX-II experiment,including all data from March 2016 to August 2018.No significant excess of events is identified above the expected background.Upper limits are set on the spin-independent dark matter-nucleon interactions.The lowest 90%confidence level exclusion on the spin-independent cross section is 2.2×10−46 cm2 at a WIMP mass of 30 GeV/c2.

Constraining self-interacting dark matter with the full dataset of PandaX-II

Self-interacting dark matter(SIDM)is a leading candidate proposed to solve discrepancies between predictions of the prevailing cold dark matter theory and observations of galaxies.Many SIDM models predict the existence of a light force carrier that mediates strong dark matter self-interactions.If the mediator couples to the standard model particles,it could produce characteristic signals in dark matter direct detection experiments.We report searches for signals of SIDM models with a light mediator using the full dataset of the PandaX-II experiment,basing on a total exposure of 132 tonne-days.No significant excess over background is found,and our likelihood analysis leads to a strong upper limit on the dark matter-nucleon coupling strength.We further combine the PandaX-II constraints and those from observations of the light element abundances in the early universe,and show that direct detection and cosmological probes can provide complementary constraints on dark matter models with a light mediator.

暗物质简介

暗物质是当代物理学和天文学面临的一大挑战.文章介绍了暗物质的发现历史,暗物质存在的观测证据,以及已知的暗物质的基本性质.还介绍了广受关注的暗物质的候选者,以及目前暗物质探测实验的进展.

暗物质直接探测实验辐射本底研究--以锦屏大设施项目为例

暗物质研究是当前最重要的基础前沿课题之一。暗物质直接探测实验有助于人类理解暗物质进而认识物质的起源和宇宙的形成与演化。通过分析在暗物质直接探测实验中宇生和原生放射性核素两类本底源和屏蔽方法,以中国锦屏地下实验室(CJPL)极深地下极低辐射本底前沿物理实验设施(DURF)项目为例,从技术路线、建设地点和系统构成三方面详细介绍降低本底的实验方案。该项目为推动我国基础物理前沿研究提供一流实验平台。

寻找宇宙中的暗物质

宇宙中存在暗物质已经得到大量天文观测的证实,但关于暗物质粒子的本质我们仍旧一无所知。为了理解暗物质的性质,许多暗物质探测实验正在展开。直接探测实验探测的是暗物质粒子与探测器物质碰撞所留下的信号,而间接探测实验则寻找暗物质湮灭的产物,如高能伽马射线、高能中微子、正电子和反质子等。理解暗物质所产生的这些信号需要我们了解暗物质的微观粒子的性质,同时也需要了解暗物质在星系或星系团中的分布形式等宏观性质。随着更大规模、更高灵敏度的实验不断投入运行,暗物质之谜有可能在不久的将来得以破解。

宇宙中的暗物质

对当前高能物理与宇宙学的研究热点之一暗物质进行了系统的介绍.介绍了暗物质的发展历史、分类、研究现状和研究方式.

小Higgs模型下暗物质直接产生过程研究

暗物质是天文学研究的热点之一,但粒子物理标准模型却不能提供合适的候选者。带有T宇称的小Higgs模型中的重光子满足暗物质的要求,计算了重光子的直接探测过程,其结果可以用来作为区别其他新物理模型的理论依据。