Neutrino Floor Research Articles

Solar neutrinos in cryogenic detectors

AbstractCoherent elastic neutrino-nucleus scattering (CE$$\nu $$ ν NS) poses an irreducible background in the search for dark matter-nucleus elastic scatterings, which is commonly known as the neutrino floor. As direct dark matter search experiments keep improving their sensitivity into so far unexplored regions, they face the challenge of approaching this neutrino floor. A precise description of the CE$$\nu $$ ν NS signal is therefore crucial for the description of backgrounds for future DM searches. In this work we discuss the scenario of detecting neutrinos in low-threshold, high-exposure cryogenic solid state experiments optimized for the search of low-mass dark matter. The energy range considered is completely dominated by solar neutrinos. In absence of any dark matter events, we treat solar neutrinos as the main signal of interest. We show that sensitivity to the flux of neutrinos from different production mechanisms can be achieved. In particular we investigate the sensitivity to the flux of pp and $$^{7}$$ 7 Be neutrinos, as well as CNO neutrinos. Furthermore, we investigate the sensitivity to dark matter signals in the presence of a solar neutrino background for different experimental scenarios, which are defined by three parameters: the target material, the energy threshold and the exposure. We show that experiments with thresholds of $$\mathcal {O}$$ O (eV) and exposures of $$\mathcal {O}$$ O (tonne-years), using $$\hbox {CaWO}_{4}$$ CaWO 4 or $$\hbox {Al}_{2}\hbox {O}_{3}$$ Al 2 O 3 targets, have discovery potential for dark matter interaction cross sections in the neutrino floor.

A closer look in the mirror: reflections on the matter/dark matter coincidence

We argue that the striking similarity between the cosmic abundances of baryons and dark matter, despite their very different astrophysical behavior, strongly motivates the scenario in which dark matter resides within a rich dark sector parallel in structure to that of the standard model. The near cosmic coincidence is then explained by an approximate ℤ2 exchange symmetry between the two sectors, where dark matter consists of stable dark neutrons, with matter and dark matter asymmetries arising via parallel WIMP baryogenesis mechanisms. Taking a top-down perspective, we point out that an adequate ℤ2 symmetry necessitates solving the electroweak hierarchy problem in each sector, without our committing to a specific implementation. A higher-dimensional realization in the far UV is presented, in which the hierarchical couplings of the two sectors and the requisite ℤ2-breaking structure arise naturally from extra-dimensional localization and gauge symmetries. We trace the cosmic history, paying attention to potential pitfalls not fully considered in previous literature. Residual ℤ2-breaking can very plausibly give rise to the asymmetric reheating of the two sectors, needed to keep the cosmological abundance of relativistic dark particles below tight bounds. We show that, despite the need to keep inter-sector couplings highly suppressed after asymmetric reheating, there can naturally be order-one couplings mediated by TeV scale particles which can allow experimental probes of the dark sector at high energy colliders. Massive mediators can also induce dark matter direct detection signals, but likely at or below the neutrino floor.

Nmssm with correct relic density and an additional 95 GeV Higgs boson

We investigate whether it is possible within the NMSSM to describe simultaneously a correct dark matter relic density complying with the latest null results from the LZ experiment, an extra Higgs boson with a mass of ∼95\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim 95$$\\end{document} GeV visible in the bb channel at LEP and the diphoton channel at the LHC, and the deviation of the anomalous magnetic moment of the muon from its value within the Standard Model. We find that this is still possible for a variety of dark matter annihilation mechanisms, for singlino-like but also bino-like lightest supersymmetric particles. We show the signal rates of the extra Higgs boson and the dark matter detection rates as function of the dark matter mass and annihilation mechanism. The dark matter direct detection cross section may well fall below the neutrino floor. The masses of the lightest electroweakly interacting supersymmetric particles are typically not far above 100 GeV, but not excluded due to unconventional decays.

A neutrino floor for the Migdal effect

Neutrino-nucleus scatterings in the detector could induce electron ionization signatures due to the Migdal effect. We derive prospects for a future detection of the Migdal effect via coherent elastic solar neutrino-nucleus scatterings in liquid xenon detectors, and discuss the irreducible background that it constitutes for the Migdal effect caused by light dark matter-nucleus scatterings. Furthermore, we explore the ionization signal induced by some neutrino electromagnetic and non-standard interactions on nuclei. In certain scenarios, we find a distinct peak on the ionization spectrum of xenon around 0.1 keV, in clear contrast to the Standard Model expectation.

Muon-induced background in a next-generation dark matter experiment based on liquid xenon

Muon-induced neutrons can lead to potentially irreducible backgrounds in rare event search experiments. We have investigated the implication of laboratory depth on the muon-induced background in a future dark matter experiment capable of reaching the so-called neutrino floor. Our simulation study focused on a xenon-based detector with 70 tonnes of active mass, surrounded by additional veto systems plus a water shield. Two locations at the Boulby Underground Laboratory (UK) were analysed as examples: an experimental cavern in salt at a depth of 2850 m w. e. (similar to the location of the existing laboratory), and a deeper laboratory located in polyhalite rock at a depth of 3575 m w. e. Our results show that no cosmogenic background events are likely to survive standard analysis cuts for 10 years of operation at either location. The largest background component we identified comes from beta-delayed neutron emission from 17\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{17}$$\\end{document}N which is produced from 19\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{19}$$\\end{document}F in the fluoropolymer components of the experiment. Our results confirm that a dark matter search with sensitivity to the neutrino floor is viable (from the point of view of cosmogenic backgrounds) in underground laboratories at these levels of rock overburden. This work was conducted in 2019–21 in the context of a feasibility study to investigate the possibility of developing the Boulby Underground Laboratory to host a next-generation dark matter experiment; however, our findings are also relevant for other underground laboratories.

Monochromatic neutrinos from dark matter through the Higgs portal

We define a minimal model of dark matter with a fermion singlet χ coupled to the visible sector through the Higgs portal and with a heavy Dirac neutrino N that opens the annihilation channel χχ → Nν. The model provides the observed relic abundance consistently with bounds from direct searches and implies a monochromatic neutrino signal at 10 GeV–1 TeV in indirect searches. In particular, we obtain the capture rate of χ by the Sun and show that the signal could be above the neutrino floor produced by cosmic rays showering in the solar surface. In most benchmark models this solar astrophysical background is above the expected dark matter signal, so the model that we propose is a canonical example of WIMP not excluded by direct searches that could be studied at neutrino telescopes and also at colliders.

Asymptotic analysis of binned likelihoods and the neutrino floor

Asymptotic analysis of binned likelihoods and the neutrino floor

Can LIGO Detect Nonannihilating Dark Matter?

Dark matter (DM) from the galactic halo can accumulate in neutron stars and transmute them into sub-2.5M_{⊙} black holes if the dark matter particles are heavy, stable, and have interactions with nucleons. We show that nondetection of gravitational waves from mergers of such low-mass black holes can constrain the interactions of nonannihilating dark matter particles with nucleons. We find benchmark constraints with LIGO O3 data, viz., σ_{χn}≥O(10^{-47}) cm^{2} for bosonic DM with m_{χ}∼PeV (or m_{χ}∼GeV, if they can Bose-condense) and ≥O(10^{-46}) cm^{2} for fermionic DM with m_{χ}∼10^{3} PeV. These bounds depend on the priors on DM parameters and on the currently uncertain binary neutron star merger rate density. However, with increased exposure by the end of this decade, LIGO will probe cross sections that are many orders of magnitude below the neutrino floor and completely test the dark matter solution to missing pulsars in the Galactic center, demonstrating a windfall science case for gravitational wave detectors as probes of particle dark matter.

Directional dark matter readout with a novel multi-mesh ThGEM for SF6 negative ion operation

Abstract Direct searches for Weakly Interacting Massive Particle (WIMP) dark matter could greatly benefit from directional measurement of the expected induced nuclear recoils. Gas-based Time Projection Chambers (TPCs) offer potential for this, opening the possibility of measuring WIMP signals below the so-called neutrino floor but also of directional measurement of recoils induced by neutrinos from the Sun, for instance as proposed by the CYGNUS collaboration. Presented here for the first time are results from a Multi-Mesh Thick Gas Electron Multiplier (MM-ThGEM) using negative ion gases for operation with such a directional dark matter TPC. Negative ion drift gases are favoured for directionality due to their low diffusion characteristics. The multiple internal mesh structure is designed to provide a high gain amplification stage when coupled to future large area Micromegas, strip or pixel charge readout planes. Experimental results and simulations are presented of MM-ThGEM gain and functionality using low pressure pure CF4, SF6 and SF6:CF4 mixtures irradiated with alpha particles and 55Fe x-rays. The concept is found to work well, providing stable operation with gains over 103 in pure SF6.

Status and future prospects of the NEWS-G experiment

The NEWS-G collaboration is searching for light dark matter using spherical proportional counters. Access to the mass range from 50 MeV to 10 GeV is enabled by the combination of low energy threshold, light gaseous targets (H, He, Ne), and highly radio-pure detector construction. Several of the recent developments that have paved the way for the operation of a new 140 cm in diameter, spherical proportional counter are presented. Constructed and commissioned at LSM using 4N copper with a 500\muμxm electroplated inner layer, the detector is now installed in SNOLAB, where it has begun data taking. Building on the electroplating of the current detector, the collaboration construct its next detector directly in the underground laboratory, using ultra-pure copper electroforming. The design and construction of ECUME, a 140 cm in diameter spherical proportional counter fully electroformed underground is discussed, along with the potential to achieve sensitivity reaching the neutrino floor in light Dark Matter searches with a next-generation detector.

Loop enhancement of direct detection cross section in a fermionic dark matter model

We investigate the effect of one loop quantum corrections on the elastic scattering of dark matter off the nucleon in a fermionic dark matter model. The model introduces two new singlet fermions and a singlet scalar. The fermions communicate with the SM particles through a Higgs portal. It is found that some viable regions in the parameter space respecting the bounds from the observed relic density, the Higgs invisible decay width, and direct detection experiment, will be shrunk significantly when one loop effects are taken into account. The regions already resided below the neutrino floor, partly may come into regions which are testable by the current or future direct detection experiments. In addition, some regions being viable at tree level, may be excluded when quantum corrections are included.

Reduction of ^{222}hbox {Rn}-induced backgrounds in a hermetic dual-phase xenon time projection chamber

The continuous emanation of ^{222}hbox {Rn} from detector surfaces causes the dominant background in current liquid xenon time projection chambers (TPCs) searching for dark matter. A significant reduction is required for the next generation of detectors which are aiming to reach the neutrino floor, such as DARWIN. ^{222}hbox {Rn}-induced backgrounds can be reduced using a hermetic TPC, in which the sensitive target volume is mechanically separated from the rest of the detector containing the majority of Rn-emanating surfaces. We present a hermetic TPC that mainly follows the well-established design of leading xenon TPCs and has been operated successfully over a period of several weeks. By scaling up the results achieved to the DARWIN-scale, we show that the hermetic TPC concept can reduce the ^{222}hbox {Rn} concentration to the required level, even with imperfect separation of the volumes.

Directional search for dark matter using nuclear emulsions with NEWSdm

Cosmological observations indicate that most of the matter in the Universe is Dark Matter. Dark Matter in the form of Weakly Interacting Massive Particles (WIMPs) can be detected directly, via its elastic scattering off target nuclei. Most current direct detection experiments only measure the energy of the recoiling nuclei. However, directional detection experiments are sensitive to the direction of the nuclear recoil as well. NEWSdm is meant to be the first experiment with a solid target for directional dark matter searches: the use of a nuclear emulsion based detector, acting both as target and tracking device, would allow to extend dark matter searches beyond the neutrino floor and provide an unambiguous signature of the detection of Galactic dark matter.

Direct Detection of Dark Matter with DarkSide-20k

DarkSide run since mid 2015 a 50-kg-active-mass dual phase Liquid Argon Time Projection Chamber (TPC), filled with low radioactivity argon from an underground source and produced world class results for both the low mass (< 20 GeV/c2) and high mass ( > 100 GeV/c2) direct detection search for dark matter. The next stage of the DarkSide program will be a new generation experiment involving a global collaboration from all the current Argon based experiments. DarkSide-20k, is designed as a 20-tonne fiducial mass dual phase Liquid Argon TPC with SiPM based cryogenic photosensors, and is expected to be free of any instrumental background for an exposure of >100 tonne year. Like its predecessor, DarkSide-20k will be housed at the INFN Gran Sasso (LNGS) underground laboratory, and it is expected to attain a WIMP-nucleon cross section exclusion sensitivity of 7.4 × 10−48 cm2 for a WIMP mass of 1 TeV/c2 in a 200 t yr run. DarkSide-20k will be installed inside a membrane cryostat containing more than 700 t of liquid Argon and be surrounded by an active neutron veto based on a Gd-loaded acrylic shell. The talk will give the latest updates of the ongoing R&D and prototype tests validating the initial design. A subsequent objective, towards the end of the next decade, will be the construction of the ultimate detector, ARGO, with a 300 t fiducial mass to push the sensitivity to the neutrino floor region for high mass WIMPs.

Semidark Higgs boson decays: Sweeping the Higgs neutrino floor

We study exotic Higgs decays $h \to Z X$, with $X$ an invisible beyond the Standard Model (SM) particle, resulting in a semi-dark final state. Such exotic Higgs decays may occur in theories of axion-like-particles (ALPs), dark photons or pseudoscalar mediators between the SM and dark matter. The SM process $h\to Z\nu\bar{\nu}$ represents an irreducible "neutrino floor" background to these new physics searches, providing also a target experimental sensitivity for them. We analyze $h \to Z + \text{invisible}$ searches at the LHC and a future ILC, showing that these exotic Higgs decays can yield sensitivity to unexplored regions of parameter space for ALPs and dark matter models.

The Solar Disk at High Energies

High energy cosmic rays illuminate the Sun and produce an image that could be observed in up to five different channels: a cosmic-ray shadow (whose energy dependence has been studied by HAWC); a gamma-ray flux (observed at E ≤ 200 GeV by Fermi-LAT); a muon shadow (detected by ANTARES and IceCube); a neutron flux (undetected, as there are no hadronic calorimeters in space); a flux of high energy neutrinos. Since these signals are correlated, the ones already observed can be used to reduce the uncertainty in the still undetected ones. Here we define a simple setup that uses the Fermi-LAT and HAWC observations to imply very definite fluxes of neutrons and neutrinos from the solar disk. In particular, we provide a fit of the neutrino flux at 10 GeV–10 TeV that includes its dependence on the zenith angle and on the period of the solar cycle. This flux represents a neutrino floor in indirect dark matter searches. We show that in some benchmark models the current bounds on the dark matter–nucleon cross section push the solar signal below this neutrino floor.

One-loop corrections to the Higgs boson invisible decay in a complex singlet extension of the SM

The search for dark matter (DM) at colliders is founded on the idea of looking for something invisible. There are searches based on production and decay processes where DM may reveal itself as missing energy. If nothing is found, our best tool to constrain the parameter space of many extensions of the Standard Model (SM) with a DM candidate is the Higgs boson. As the measurements of the Higgs couplings become increasingly precise, higher-order corrections will start to play a major role. The tree-level contribution to the invisible decay width provides information about the portal coupling. Higher-order corrections also give us access to other parameters from the dark sector of the Higgs potential that are not present in the tree-level amplitude. In this work we will focus on the complex singlet extension of the SM in the phase with a DM candidate. We calculate the one-loop electroweak corrections to the decay of the Higgs boson into two DM particles. We find that the corrections are stable and of the order of a few percent. The present measurement of the Higgs invisible branching ratio, $\mathrm{BR}(H\ensuremath{\rightarrow}\text{ }\mathrm{invisible})<0.11$, already constrains the parameter space of the model at leading order. We expect that by the end of the LHC the experimental measurement will require the inclusion of the electroweak corrections to the decay in order to match the experimental accuracy. Furthermore, the only competing process, which is direct detection, is shown to have a cross section below the neutrino floor.

The last complex WIMPs standing

We continue the study of weakly interacting massive particles (WIMP) started in Bottaro et al. (Eur Phys J C 82:31, 2022), focusing on a single complex electroweak n-plet with non-zero hypercharge added to the Standard Model. The minimal splitting between the Dark Matter and its electroweak neutral partner required to circumvent direct detection constraints allows only multiplets with hypercharge smaller or equal to 1. We compute for the first time all the calculable WIMP masses up to the largest multiplet allowed by perturbative unitarity. For the minimal allowed splitting, most of these multiplets can be fully probed at future large-exposure direct detection experiments, with the notable exception of the doublet with hypercharge 1/2. We show how a future muon collider can fully explore the parameter space of the complex doublet combining missing mass, displaced track and long-lived track searches. In the same spirit, we study how a future muon collider can probe the parameter space of complex WIMPs in regions where the direct detection cross section drops below the neutrino floor. Finally, we comment on how precision observables can provide additional constraints on complex WIMPs.

Purity monitor and TPC design for Xenoscope

The Xenoscope detector has the main goal of achieving electron drift over a 2.6 m distance, which is the scale of the future multi-ton scale dual-phase liquid xenon (LXe) TPCs for dark matter and rare event searches. The DARWIN experiment aims to have 40 tons of LXe as its active volume, reaching the neutrino floor background. Xenoscope will serve as a facility for photosensors and future technologies testing, in order to develop the next generation of LXe dark matter detectors. Metre-scale drift lengths will require a precise monitoring of the LXe purity. In this context, we have designed an integrated xenon purity monitor and a TPC, with the fabrication of the former nearly complete. We have characterised the electronics for charge readout, as well as different photocathode materials to optimise the charge yield and thus increase the precision in the purity measurement.

Flavor inspired model for dark matter

The discrepancies between data on rare $b$-hadron decays, controlled by the underlying neutral-current transitions $b\ensuremath{\rightarrow}s{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}(\ensuremath{\ell}=e,\ensuremath{\mu})$, and the corresponding Standard Model predictions constitute one of the most intriguing hints for new physics. Leptoquarks are prime candidates to solve these anomalies and, in particular, the scalar leptoquark, ${S}_{3}$, triplet under $SU(2{)}_{L}$ with hypercharge $Y=\ensuremath{-}1/3$, provides a very good fit to data. Here, we entertain the possibility that the same scalar leptoquark ${S}_{3}$, responsible for the lepton flavor universality anomalies, is the portal to a fermionic dark sector consisting of two additional vectorlike fermions, one of which is a candidate for the cosmological dark matter. We study two scenarios, where the dark matter candidate belongs to an $SU(2{)}_{L}$ singlet and triplet respectively, and discuss the theory parameter space in the context of the dark matter candidate's relic density and prospects for direct and indirect dark matter searches. Direct detection rates are highly suppressed and generically below the neutrino floor. Current observations with, and future prospects for, high-energy gamma-ray telescopes such as HESS and the Cherenkov Telescope Array are much more promising, as they already provide powerful constraints on the models under consideration, and will potentially probe the full parameter space in the future.