Implications of the XENON1T excess on the dark matter interpretation

Abstract

The dark matter interpretation for a recent observation of excessive electron recoil events at the XENON1T detector seems challenging because its velocity is not large enough to give rise to recoiling electrons of $$ \mathcal{O}\left(\mathrm{keV}\right) $$ O keV . Fast-moving or boosted dark matter scenarios are receiving attention as a remedy for this issue, rendering the dark matter interpretation a possibility to explain the anomaly. We investigate various scenarios where such dark matter of spin 0 and 1/2 interacts with electrons via an exchange of vector, axial-vector, pseudo-scalar, or scalar mediators. We find parameter values not only to reproduce the excess but to be consistent with existing bounds. Our study suggests that the scales of mass and coupling parameters preferred by the excess can be mostly affected by the type of mediator, and that significantly boosted dark matter can explain the excess depending on the mediator type and its mass choice. The method proposed in this work is general, and hence readily applicable to the interpretation of observed data in the dark matter direct detection experiment.

Constraints on electron-scattering interpretation of XENON1T excess

“…Such a broad spectrum may be realized by a new particle χ scattering with electrons [3,6,10,26,42,48,50,52]. It is likely to be electrically neutral because events with multiple scatterings are vetoed in the analysis [1].…”

Solar Active-Sterile Neutrino Conversion with Atomic Effects at Dark Matter Direct Detection Experiments

“…4. As discussed below (23), the matrix element part is approximately 4m e E 2 ν /(2m e T r +m 2 Z ) 2 for the free electron scattering with vector mediator. For comparison, the scalar case has m e (2m e T r + m 2 s )/(2m e T r + m 2 φ ) 2 .…”

“…The excess might indicate new physics beyond the SM (BSM) if not the tritium background [5]. Possible explanations include axion or axion-like particles [6][7][8][9][10][11][12][13][14], elastic [15][16][17][18][19][20][21][22][23][24][25] and inelastic [26][27][28][29][30][31][32][33][34][35][36][37] scattering between DM and electron, the Migdal effect of DM scattering with nuclei [38], and DM decay [39][40][41][42]. Another possibility is sterile neutrino as DM in our galaxy.…”

Manifesting hidden dynamics of a sub-component dark matter

“…For σ self /m as large as ∼ 1 cm 2 /g, DM self-heating epoch could persist until the vicinity of the matterradiation equality, i.e., T dec,self ∼ T eq [Eq. (27)]. The resultant T χ1 around T eq is much larger than that without DM self-heating, and may be sizable to make χ 1 behave as warm dark matter (WDM).…”

“…Among them, the scenarios of non-minimal particle contents inside a dark sector have drawn lots of attention because of their abilities resolving various phenomenological issues and providing extra power to many current/future experiments of searching for their signals in new and creative ways. Examples include the scenarios of inelastic DM [3], self-interacting non-minimal dark sector to address small-scale issues [4][5][6][7][8][9][10] and the existence of the supermassive blackholes at high redshifts [11][12][13], and multi-component boosted dark matter (BDM) whose unique signals can be probed in a variety of neutrino and direct-detection experiments [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Nevertheless, less attention has been given to exploring the cosmological dynamics of the sub-dominant component of DM and the corresponding impact on their detectability.…”