Bhaskar Dutta, Wei-Chih Huang, Doojin Kim, Jayden L. Newstead, Jong-Chul Park, Iman Shaukat Ali
We propose a new approach to search for light dark matter (DM), with keV-GeV mass, via inelastic nucleus scattering at large-volume neutrino detectors such as Borexino, DUNE, Super-K, Hyper-K, and JUNO. The approach uses inelastic nuclear scattering of cosmic-ray boosted DM, enabling a low background search for DM in these experiments. Large neutrino detectors, with higher thresholds than dark matter detectors, can be used, since the nuclear deexcitation lines are O(10) MeV. Using a hadrophilic dark-gauge-boson-portal model as a benchmark, we show that the nuclear inelastic channels generally provide better sensitivity than the elastic scattering for a large region of light DM parameter space.
Koun Choi, Jong-Chul Park
Large-volume neutrino experiments are ideal for testing boosted dark matter (BDM) scenarios. We propose, for the first time, an approach to utilize knockout neutrons by detecting de-excitation $γ$ rays and coincident captured neutrons from dark-matter interactions with bound neutrons in oxygen, while previous studies have focused on knockout-protons and electrons. This method is especially crucial for water Čerenkov detectors, where high proton Čerenkov threshold ($\sim$1 GeV) suppresses signal acceptance. Recently, Super-Kamiokande (SK) was doped with 0.03\% gadolinium (SK-Gd) to enhance neutron tagging efficiency. Using SK-Gd as a target experiment, we demonstrate that this method increases sensitivity to BDM models by an order of magnitude compared to proton-based analysis, and it allows exploration of a wider range of light dark-matter models previously inaccessible with proton-based analysis. We also present the projected sensitivity for the upcoming Hyper-Kamiokande detector.
Jodi Cooley, Tongyan Lin, W. Hugh Lippincott, Tracy R. Slatyer, Tien-Tien Yu, Daniel S. Akerib, Tsuguo Aramaki, Daniel Baxter, Torsten Bringmann, Ray Bunker, Daniel Carney, Susana Cebrián, Thomas Y. Chen, Priscilla Cushman, C. E. Dahl, Rouven Essig, Alden Fan, Richard Gaitskell, Cristano Galbiati, Graciela B. Gelmini, Graham K. Giovanetti, Guillaume Giroux, Luca Grandi, J. Patrick Harding, Scott Haselschwardt, Lauren Hsu, Shunsaku Horiuchi, Yonatan Kahn, Doojin Kim, Geon-Bo Kim, Scott Kravitz, V. A. Kudryavtsev, Noah Kurinsky, Rafael F. Lang, Rebecca K. Leane, Benjamin V. Lehmann, Cecilia Levy, Shengchao Li, Ben Loer, Aaron Manalaysay, C. J Martoff, Gopolang Mohlabeng, M. E. Monzani, Alexander St J. Murphy, Russell Neilson, Harry N. Nelson, Ciaran A. J. O'Hare, K. J. Palladino, Aditya Parikh, Jong-Chul Park, Kerstin Perez, Stefano Profumo, Nirmal Raj, Brandon M. Roach, Tarek Saab, Maria Luísa Sarsa, Richard Schnee, Sally Shaw, Seodong Shin, Kuver Sinha, Kelly Stifter, Aritoki Suzuki, M. Szydagis, Tim M. P. Tait, Volodymyr Takhistov, Yu-Dai Tsai, S. E. Vahsen, Edoardo Vitagliano, Philip von Doetinchem, Gensheng Wang, Shawn Westerdale, David A. Williams, Xin Xiang, Liang Yang
This report summarizes the findings of the CF1 Topical Subgroup to Snowmass 2021, which was focused on particle dark matter. One of the most important scientific goals of the next decade is to reveal the nature of dark matter (DM). To accomplish this goal, we must delve deep, to cover high priority targets including weakly-interacting massive particles (WIMPs), and search wide, to explore as much motivated DM parameter space as possible. A diverse, continuous portfolio of experiments at large, medium, and small scales that includes both direct and indirect detection techniques maximizes the probability of discovering particle DM. Detailed calibrations and modeling of signal and background processes are required to make a convincing discovery. In the event that a candidate particle is found through different means, for example at a particle collider, the program described in this report is also essential to show that it is consistent with the actual cosmological DM. The US has a leading role in both direct and indirect detection dark matter experiments -- to maintain this leading role, it is imperative to continue funding major experiments and support a robust R\&D program.
Doojin Kim, Pedro A. N. Machado, Jong-Chul Park, Seodong Shin
Neutrino and dark matter experiments with large-volume ($\gtrsim 1$ ton) detectors can provide excellent sensitivity to signals induced by energetic light dark matter coming from the present universe. Taking boosted dark matter as a concrete example of energetic light dark matter, we scrutinize two representative search channels, electron scattering and proton scattering including deep inelastic scattering processes, in the context of elastic and inelastic boosted dark matter, in a completely detector-independent manner. In this work, a dark gauge boson is adopted as the particle to mediate the interactions between the Standard Model particles and boosted dark matter. We find that the signal sensitivity of the two channels highly depends on the (mass-)parameter region to probe, so search strategies and channels should be designed sensibly especially at the earlier stage of experiments. In particular, the contribution from the boosted-dark-matter-initiated deep inelastic scattering can be subleading (important) compared to the quasi-elastic proton scattering, if the mass of the mediator is below (above) $\mathcal{O}$(GeV). We demonstrate how to practically perform searches and relevant analyses, employing example detectors such as DarkSide-20k, DUNE, Hyper-Kamiokande, and DeepCore, with their respective detector specifications taken into consideration. For other potential detectors we provide a summary table, collecting relevant information, from which similar studies can be fulfilled readily.
Youngsub Yoon, Jong-Chul Park, Ho Seong Hwang
Jun 12, 2023·astro-ph.CO·PDF Gravitational lensing studies of the Bullet Cluster suggested convincingly in favor of the existence of dark matter. However, it was performed without the knowledge of the original orientation of each galaxy before gravitational lensing. A potential improvement to this issue lies in the measurement of the original orientation from the polarization direction of radio waves emitted from each galaxy. In this context, Francfort et al. derived a formula that can utilize the information about the original orientation of each galaxy to obtain what is called {\it shear}. However, we demonstrate that shear in their formula should be replaced by {\it reduced shear} when the change in sizes of images of galaxies is taken into account. As the previous gravitational lensing analysis of the Bullet Cluster used reduced shear, we suggest applying our improved formula directly for the reanalysis once we obtain the polarization direction of radio waves. In particular, we show that our new formula can yield a more accurate analysis than the previous one, if the polarization direction can be measured more precisely than $10^\circ$. Moreover, the approach discussed in this work is generically applicable to the gravitational lensing analysis of clusters, not only limited to the Bullet Cluster.
Bumseok Kyae, Jong-Chul Park
The 130 GeV gamma-ray line based on tentative analyses on the Fermi-LAT data is hard to be understood with dark matter annihilation in the conventional framework of the MSSM. We point out that it can be nicely explained with two body decay of a scalar dark matter ($\tildeφ_{\rm DM}\rightarrowγγ$) by the dimension 6 operator suppressed with the mass of the grand unification scale ($\sim 10^{16}$ GeV), ${\cal L}\supset|\tildeφ_{\rm DM}|^2F_{μν}F^{μν}/M_{\rm GUT}^2$, in which the scalar dark matter $\tildeφ_{\rm DM}$ develops a TeV scale vacuum expectation value. We propose a viable model explaining the 130 GeV gamma-ray line.
Eung Jin Chun, Jong-Chul Park
Motivated by the recent PAMELA and ATIC data, one is led to a scenario with heavy vector-like dark matter in association with a hidden $U(1)_X$ sector below GeV scale. Realizing this idea in the context of gauge mediated supersymmetry breaking (GMSB), a heavy scalar component charged under $U(1)_X$ is found to be a good dark matter candidate which can be searched for direct scattering mediated by the Higgs boson and/or by the hidden gauge boson. The latter turns out to put a stringent bound on the kinetic mixing parameter between $U(1)_X$ and $U(1)_Y$: $θ\lesssim 10^{-6}$. For the typical range of model parameters, we find that the decay rates of the ordinary lightest neutralino into hidden gauge boson/gaugino and photon/gravitino are comparable, and the former decay mode leaves displaced vertices of lepton pairs and missing energy with distinctive length scale larger than 20 cm for invariant lepton pair mass below 0.5 GeV. An unsatisfactory aspect of our model is that the Sommerfeld effect cannot raise the galactic dark matter annihilation by more than 60 times for the dark matter mass below TeV.
Gian F. Giudice, Doojin Kim, Jong-Chul Park, Seodong Shin
We explore a novel class of multi-particle dark sectors, called Inelastic Boosted Dark Matter (iBDM). These models are constructed by combining properties of particles that scatter off matter by making transitions to heavier states (Inelastic Dark Matter) with properties of particles that are produced with a large Lorentz boost in annihilation processes in the galactic halo (Boosted Dark Matter). This combination leads to new signals that can be observed at ordinary direct detection experiments, but require unconventional searches for energetic recoil electrons in coincidence with displaced multi-track events. Related experimental strategies can also be used to probe MeV-range boosted dark matter via their interactions with electrons inside the target material.
Doojin Kim, Kyoungchul Kong, Jong-Chul Park, Seodong Shin
We propose the idea of "Earth Shielding" to reject cosmic-ray backgrounds, in the search for boosted dark matter at surface neutrino detectors, resulting in the enhancement of the signal-to-background ratio. The identification of cosmic-originating rare signals, especially lacking features, at surface detectors is often considered hopeless due to a vast amount of cosmic-ray-induced background, hence underground experiments are better motivated to avoid such a challenge. We claim that surface detectors can attain remarkable sensitivities to even featureless signals, once restricting to events coming through the Earth from the opposite side of the detector location for the signals leaving appreciable tracks from which the source direction is inferred. By doing so, potential backgrounds in the signal region of interest can be substantially suppressed. To validate our claim, we study experimental reaches at several surface experiments such as SBN Program (MicroBooNE, ICARUS, and SBND) and ProtoDUNE for elastic boosted dark matter signatures stemming from the Galactic Center. We provide a systematic discussion on maximizing associated signal sensitivities.
Doojin Kim, Jong-Chul Park
We propose a novel mechanism enabling us to have a continuum bump as a signature of gamma-ray excess in indirect detection experiments of dark matter (DM), postulating a generic dark sector having (at least) two DM candidates. With the assumption of non-zero mass gap between the two DM candidates, the heavier one directly communicates to the partner of the lighter one. Such a partner then decays into a lighter DM particle along with an "axion-like" particle (ALP) or dark "pion", which subsequently decays into a pair of photons, via a more-than-one step cascade decay process. Since the cascade is initiated by the dark partner obtaining a non-trivial fixed boost factor, a continuum gamma-ray energy spectrum naturally arises even with a particle directly decaying into two photons. We apply the main idea to the energy spectrum of the GeV gamma-rays from around the Galactic Center (GC), and find that the relevant observational data is well-reproduced by the theory expectation predicted by the proposed mechanism. Remarkably, the relevant energy spectrum has a robust peak at half the mass of the ALP or dark pion, as opposed to popular DM models directly annihilating to Standard Model particles where physical interpretations of the energy peak are not manifest. Our data analysis reports substantially improved fits, compared to those annihilating DM models, and ~900 MeV mass of the ALP or dark pion.
Doojin Kim, Jong-Chul Park, Seodong Shin
We propose a new search channel for boosted dark matter (BDM) signals coming from the present universe, which are distinct from simple neutrino signals including those coming from the decay or pair-annihilation of dark matter. The signal process is initiated by the scattering of high-energetic BDM off either an electron or a nucleon. If the dark matter is dark-sector U(1)-charged, the scattered BDM may radiate a dark gauge boson (called "dark-strahlung") which subsequently decays to a Standard Model fermion pair. We point out that the existence of this channel may allow for the interpretation that the associated signal stems from BDM, not from the dark-matter-origin neutrinos. Although the dark-strahlung process is generally subleading compared to the lowest-order simple elastic scattering of BDM, we find that the BDM with a significant boost factor may induce an O(10-20%) event rate in the parameter regions unreachable by typical beam-produced dark-matter. We further find that the dark-strahlung channel may even outperform the leading-order channel in the search for BDM, especially when the latter is plagued by substantial background contamination. We argue that cosmogenic BDM searches readily fall in such a case, hence taking full advantage of dark-strahlung. As a practical application, experimental sensitivities expected in the leading-order and dark-strahlung channels are contrasted in dark gauge boson parameter space, under the environment of DUNE far-detectors, revealing usefulness of dark-strahlung.
Jong-Chul Park, Gaurav Tomar
Neutrino-electron scattering experiments play a crucial role in investigating the non-standard interactions of neutrinos. In certain models, these interactions can include interference terms that may affect measurements. Next-generation direct detection experiments, designed primarily for dark-matter searches, are also getting sensitive to probe the neutrino properties. We utilise the data from XENONnT, a direct detection experiment, and Borexino, a low-energy solar neutrino experiment, to investigate the impact of interference on non-standard interactions. Our study considers models with an additional $U(1)$, including $U(1)_{B-L}$, $U(1)_{L_e-L_μ}$, and $U(1)_{L_e-L_τ}$, to investigate the impact of interference on non-standard neutrino interactions. We demonstrate that this interference can lead to a transition between the considered non-standard interaction models in the energy range relevant to both the XENONnT and Borexino experiments. This transition can be used to distinguish among the considered models if any signals are observed at direct detection or neutrino experiments. Our findings underscore the importance of accounting for the interference and incorporating both direct detection and solar neutrino experiments to gain a better understanding of neutrino interactions and properties.
Jong-Chul Park, Seong Chan Park
In light of the recent observation of the Fermi-LAT 130 GeV gamma-ray line, we suggest a model of scalar dark matter in hidden sector, which can decay into two (hidden) photons. The process is radiatively induced by a GUT scale fermion in the loop, which is charged under a hidden sector U(1), and the kinetic mixing ($\sim εF^{μν}F'_{μν}$) enables us to fit the required decay width for the Fermi-LAT peak. The model does not allow any dangerous decay channels into light standard model particles.
Bumseok Kyae, Jong-Chul Park
Light fermionic/scalar dark matter (DM) (m_DM ~ 8 GeV) neutral under the standard model can be responsible for the CDMS and CoGeNT signals, and the Fermi-LAT gamma-ray excesses. In order to explain them in a relatively simple framework, we have explored various DM annihilation and scattering processes, discussing important phenomenological constraints coming from particle physics. Assuming that the two independent observations have a common DM origin and the processes arise through a common mediator, DM should annihilate into tau/anti-tau lepton pairs through an s-channel, and scatter with nuclei through a t-channel process. To avoid the p-wave suppression, a new Higgs-like scalar field with a mass of O(1) TeV is necessary as a common mediator of both the processes. We propose a supersymmetric model realizing the scenario.
Kyoungchul Kong, Jong-Chul Park, Seong Chan Park
Recently a weak X-ray emission around E ~ 3.5 keV was detected in the Andromeda galaxy and various galaxy clusters including the Perseus galaxy cluster but its source has been unidentified. Axino, the superpartner of axion, with a mass 2E is suggested as a possible origin of the line with R-parity violating decay into photon and neutrino. Moreover, most of parameter space is consistent with recent observation by the BICEP2 experiment.
Doojin Kim, Jong-Chul Park, Seodong Shin
We propose a novel dark matter (DM) detection strategy for the models with non-minimal dark sector. The main ingredients in the underlying DM scenario are a boosted DM particle and a heavier dark sector state. The relativistic DM impinged on target material scatters off inelastically to the heavier state which subsequently decays into DM along with lighter states including visible (Standard Model) particles. The expected signal event, therefore, accompanies a visible signature by the secondary cascade process associated with a recoiling of the target particle, differing from the typical neutrino signal not involving the secondary signature. We then discuss various kinematic features followed by DM detection prospects at large volume neutrino detectors with a model framework where a dark gauge boson is the mediator between the Standard Model particles and DM.
Ji-Haeng Huh, Jihn E. Kim, Jong-Chul Park, Seong Chan Park
Nov 22, 2007·astro-ph·PDF We present a possible explanation of the recently observed 511 keV $γ$-ray anomaly with a new ``millicharged'' fermion. The new fermion is light (${\cal O}({\rm MeV})$) but has never been observed by any collider experiments mainly because of its tiny electromagnetic charge $εe$. We show that constraints from its relic density in the Universe and collider experiments allow a parameter range such that the 511 keV cosmic $γ$-ray emission from the galactic bulge may be due to positron production from this millicharged fermion.
Hae Young Cho, Jong-Chul Park
In the Intriligator-Seiberg-Shih model, we parametrize spontaneous breaking of $U(1)_R$ symmetry with two gauge singlets with R-charges 1 and --1. These singlets can play the role of the messengers. The messenger scale is dynamically generated, and hence there is no hierarchy problem between the supersymmetry breaking scale and the messenger scale. In the gauge mediation scenario, supersymmetry breaking scale turns out to be around $\mathcal{O}(10^6)\textrm{GeV}$.
Doojin Kim, Jong-Chul Park, Gil-Ho Lee, Kin Chung Fong
We propose a new dark-matter detection strategy that will potentially enable the search for super-light dark matter $m_χ\simeq 0.1$ keV, improving the minimum detectable mass by more than three orders of magnitude compared to ongoing experiments. This can be achieved by intimately integrating the target material, specifically the $π$-bond electrons in graphene, into a Josephson junction to create a highly sensitive detector capable of detecting energy deposits from dark matter as small as $\sim 0.1$ meV. We investigate detection prospects of pg-, ng-, and $μ$g-scale detectors by calculating the scattering rate between dark matter and free electrons confined in two-dimensional graphene, including Pauli-blocking factors and in-medium screening effects. We find that the proposed detector is expected to not only serve as a complementary probe of super-light dark matter but also achieve higher experimental sensitivities than other proposed experiments, assuming zero readout noise, thanks to the extremely low threshold energy of our graphene Josephson junction sensor.
Shin'ichiro Ando, Sebastian Baum, Michael Boylan-Kolchin, Esra Bulbul, Michael Burgess, Ilias Cholis, Philip von Doetinchem, JiJi Fan, Patrick J. Harding, Shunsaku Horiuchi, Rebecca K. Leane, Oscar Macias, Katie Mack, Kohta Murase, Lina Necib, Ibles Olcina, Laura Olivera-Nieto, Jong-Chul Park, Kerstin Perez, Marco Regis, Nicholas L. Rodd, Carsten Rott, Kuver Sinha, Volodymyr Takhistov, Yun-Tse Tsai, Devin Walker
This whitepaper focuses on the astrophysical systematics which are encountered in dark matter searches. Oftentimes in indirect and also in direct dark matter searches, astrophysical systematics are a major limiting factor to sensitivity to dark matter. Just as there are many forms of dark matter searches, there are many forms of backgrounds. We attempt to cover the major systematics arising in dark matter searches using photons -- radio and gamma rays -- to cosmic rays, neutrinos and gravitational waves. Examples include astrophysical sources of cosmic messengers and their interactions which can mimic dark matter signatures. In turn, these depend on commensurate studies in understanding the cosmic environment -- gas distributions, magnetic field configurations -- as well as relevant nuclear astrophysics. We also cover the astrophysics governing celestial bodies and galaxies used to probe dark matter, from black holes to dwarf galaxies. Finally, we cover astrophysical backgrounds related to probing the dark matter distribution and kinematics, which impact a wide range of dark matter studies. In the future, the rise of multi-messenger astronomy, and novel analysis methods to exploit it for dark matter, will offer various strategic ways to continue to enhance our understanding of astrophysical backgrounds to deliver improved sensitivity to dark matter.