Constraining dark matter annihilation with cosmic ray antiprotons using neural networks

The interpretation of data from indirect detection experiments searching for dark matter annihilations requires computationally expensive simulations of cosmic-ray propagation. In this work we present a new method based on Recurrent Neural Networks that significantly accelerates simulations of secondary and dark matter Galactic cosmic ray antiprotons while achieving excellent accuracy. This approach allows for an efficient profiling or marginalisation over the nuisance parameters of a cosmic ray propagation model in order to perform parameter scans for a wide range of dark matter models. We identify importance sampling as particularly suitable for ensuring that the network is only evaluated in well-trained parameter regions. We present resulting constraints using the most recent AMS-02 antiproton data on several models of Weakly Interacting Massive Particles. The fully trained networks are released as DarkRayNet together with this work and achieve a speed-up of the runtime by at least two orders of magnitude compared to conventional approaches.

Scintillation light increase of carbontetrafluoride gas at low temperature

Scintillation detector is widely used for the particle detection in the field of particle physics. Particle detectors containing fluorine-19 (19F) are known to have advantages for Weakly Interacting Massive Particles (WIMPs) dark matter search, especially for spin-dependent interactions with WIMPs due to its spin structure. In this study, the scintillation properties of carbontetrafluoride (CF4) gas at low temperature were evaluated because its temperature dependence of light yield has not been measured. We evaluated the light yield by cooling the gas from room temperature (300 K) to 263 K. As a result, the light yield of CF4 was found to increase by (41.0 ± 4.0stat. ± 6.6syst.)% and the energy resolution was also found to improve at low temperature.

Search for dark matter from the centre of the Earth with 8 years of IceCube data

Neutrinos have been proved to be unique messengers in the understanding of fundamental physics processes, and in astrophysical data sets they may provide hints of physics beyond the Standard Model. For example, neutrinos could be the key to discerning between various dark matter models that are based on Weakly Interacting Massive Particles (WIMPs). WIMPs can scatter off standard matter nuclei in the vicinity of massive bodies such as the Sun or the Earth, lose velocity, and be gravitationally trapped in the center of the body. Self-annihilation of dark matter into Standard Model particles may produce an observable flux of neutrinos. For the case of the Earth, an excess of neutrinos coming from the center of the planet could indicate WIMP capture and annihilation at the Earth’s core. The IceCube Neutrino Observatory, located at the geographical South Pole, is sensitive to these excess neutrinos. A search has been conducted on 8 years of IceCube data, probing multiple dark matter channels and masses. With this analysis, we show that IceCube has world-leading sensitivity to the spin-independent dark matter-nucleon scattering cross section above a WIMP mass of 100 GeV.

Strong constraints from COSINE-100 on the DAMA dark matter results using the same sodium iodide target

It is a long-standing debate as to whether or not the annual modulation in the event rate observed by the DAMA sodium iodide experiment is caused by the interaction of dark matter particles. To resolve this issue, several groups have been working to develop new experiments with the aim of reproducing or refuting DAMA's results using the same sodium iodide target medium. The COSINE-100 experiment is one of these that is currently operating with 106 kg of low-background sodium iodide crystals at the Yangyang underground laboratory. Analysis of the initial 59.5 days of COSINE-100 data showed that the annual modulation signal reported by DAMA is inconsistent with explanation using spin-independent interaction of weakly interacting massive particles (WIMPs), a favored candidate of dark matter particles, with sodium or iodine nuclei in the context of the standard halo mode. However, this first result left open interpretations using certain alternative dark matter models, dark matter halo distributions, and detector responses that could allow room for consistency between DAMA and COSINE-100. Here we present new results from over 1.7 years of COSINE-100 operation with improved event selection and energy threshold reduced from 2 keV to 1 keV. We find an order of magnitude improvement in sensitivity, sufficient for the first time to strongly constrain these alternative scenarios, as well as to further strengthen the previously observed inconsistency with the WIMP-nucleon spin-independent interaction hypothesis.

Sensitivity of the SHiP experiment to light dark matter

Dark matter is a well-established theoretical addition to the Standard Model supported by many observations in modern astrophysics and cosmology. In this context, the existence of weakly interacting massive particles represents an appealing solution to the observed thermal relic in the Universe. Indeed, a large experimental campaign is ongoing for the detection of such particles in the sub-GeV mass range. Adopting the benchmark scenario for light dark matter particles produced in the decay of a dark photon, with αD = 0.1 and mA′ = 3mχ, we study the potential of the SHiP experiment to detect such elusive particles through its Scattering and Neutrino detector (SND). In its 5-years run, corresponding to 2 · 1020 protons on target from the CERN SPS, we find that SHiP will improve the current limits in the mass range for the dark matter from about 1 MeV to 300 MeV. In particular, we show that SHiP will probe the thermal target for Majorana candidates in most of this mass window and even reach the Pseudo-Dirac thermal relic.

The effects of asymmetric dark matter on stellar evolution – I. Spin-dependent scattering

ABSTRACT Most of the dark matter (DM) search over the last few decades has focused on weakly interacting massive particles (WIMPs), but the viable parameter space is quickly shrinking. Asymmetric dark matter (ADM) is a WIMP-like DM candidate with slightly smaller masses and no present-day annihilation, meaning that stars can capture and build up large quantities. The captured ADM can transport energy through a significant volume of the star. We investigate the effects of spin-dependent ADM energy transport on stellar structure and evolution in stars with 0.9 ≤ M⋆/M⊙ ≤ 5.0 in varying DM environments. We wrote a mesa module1 that calculates the capture of DM and the subsequent energy transport within the star. We fix the DM mass to 5 GeV and the cross-section to 10−37 cm2, and study varying environments by scaling the DM capture rate. For stars with radiative cores (0.9 ≤ M⋆/M⊙ ≲ 1.3 ), the presence of ADM flattens the temperature and burning profiles in the core and increases main-sequence (MS) (Xc > 10−3) lifetimes by up to $\sim \! 20{{\ \rm per\ cent}}$. We find that strict requirements on energy conservation are crucial to the simulation of ADM’s effects on these stars. In higher mass stars, ADM energy transport shuts off core convection, limiting available fuel and shortening MS lifetimes by up to $\sim \! 40{{\ \rm per\ cent}}$. This may translate to changes in the luminosity and effective temperature of the MS turnoff in population isochrones. The tip of the red giant branch may occur at lower luminosities. The effects are largest in DM environments with high densities and/or low velocity dispersions, making dwarf and early forming galaxies most likely to display the effects.

Event Rates for the Scattering of Weakly Interacting Massive Particles from 23Na and 40Ar

Detection rates for the elastic and inelastic scattering of weakly interacting massive particles (WIMPs) off 23Na are calculated within the framework of Deformed Shell Model (DSM) based on Hartree-Fock states. At first, the spectroscopic properties of the detector nucleus, like energy spectra and magnetic moments, are evaluated and compared with experimental data. Following the good agreement of these results, DSM wave functions are used for obtaining elastic and inelastic spin structure functions, nuclear structure coefficients and so forth for the WIMP-23Na scattering. Then, the event rates are also computed with a given set of supersymmetric parameters. In the same manner, using DSM wavefunctions, nuclear structure coefficients and event rates for elastic scattering of WIMPs from 40Ar are also obtained. These results for event rates and also for annual modulation will be useful for the ongoing and future WIMP detection experiments involving detector materials with 23Na and 40Ar nuclei.

Stability and pulsation of the first dark stars

ABSTRACT The first bright objects to form in the Universe might not have been ‘ordinary’ fusion-powered stars, but ‘dark stars’ (DSs) powered by the annihilation of dark matter (DM) in the form of weakly interacting massive particles (WIMPs). If discovered, DSs can provide a unique laboratory to test DM models. DSs are born with a mass of the order of M⊙ and may grow to a few million solar masses; in this work we investigate the properties of early DSs with masses up to $\sim \! 1000 \, \mathrm{ M}_\odot$, fueled by WIMPS weighing 100 GeV. We improve the previous implementation of the DM energy source into the stellar evolution code mesa. We show that the growth of DSs is not limited by astrophysical effects: DSs up to $\sim \!1000 \, \mathrm{ M}_{\odot }$ exhibit no dynamical instabilities; DSs are not subject to mass-loss driven by super-Eddington winds. We test the assumption of previous work that the injected energy per WIMP annihilation is constant throughout the star; relaxing this assumption does not change the properties of the DSs. Furthermore, we study DS pulsations, for the first time investigating non-adiabatic pulsation modes, using the linear pulsation code gyre. We find that acoustic modes in DSs of masses smaller than $\sim \! 200 \, \mathrm{ M}_\odot$ are excited by the κ − γ and γ mechanism in layers where hydrogen or helium is (partially) ionized. Moreover, we show that the mass-loss rates potentially induced by pulsations are negligible compared to the accretion rates.

Capture Rate of Weakly Interacting Massive Particles (WIMPs) In Binary Star Systems

The distribution of dark matter (DM) inside galaxies is not uniform. Near the central regions, its density is the highest. Then, it is logical to suppose that, inside galaxies, DM affects the physics of stars in central regions more than outer regions. Besides, current stellar evolutionary models did not consider DM effects in their assumptions. To consider DM effects, at first one must estimate how much DM a star contains. The capture rate (CR) of DM particles by individual stars was investigated already in the literature. In this work, we discuss how CR can be affected when stars are members of binary star systems (BSS) (instead of studying them individually). When a star is a member of a BSS, its speed changes periodically due to the elliptical motion around its companion star. In this work, we investigated CR by BSSs in different BSS configurations. In the end, we discussed observational signatures that can be attributed to the DM effects in BSSs.