Particle Signatures Research Articles

Heavy particle signatures in cosmological correlation functions with tensor modes

We explore the possibility to make use of cosmological data to look for signatures of unknown heavy particles whose masses are on the order of the Hubble parameter during the time of inflation. To be more specific we take up the quasi-single field inflation model, in which the isocurvaton σ is supposed to be the heavy particle. We study correlation functions involving both scalar (ζ ) and tensor (γ ) perturbations and search for imprints of the σ-particle effects. We make use of the technique of the effective field theory for inflation to derive the ζ σ and γ ζ σ couplings. With these couplings we compute the effects due to σ to the power spectrum ⟨ ζ ζ ⟩ and correlations ⟨ γs ζ ζ ⟩ and ⟨ γs1 γ s2 ζ ζ ⟩ , where s, s1 and s2 are the polarization indices of gravitons. Numerical analyses of the σ-mass effects to these correlations are presented. It is argued that future precise observations of these correlations could make it possible to measure the σ-mass and the strength of the ζ σ and γ ζ σ couplings. As an extension to the N-graviton case we also compute the correlations ⟨ γ s1 ⋯ γ sN ζ ζ ⟩ and ⟨ γ s1 ⋯ ⋯ γ s2N ζ ζ ⟩ and their σ-mass effects. It is suggested that larger N correlation functions are useful to probe larger σ-mass.

A minimal model for two-component FIMP dark matter: A basic search

In the multi-component configurations of dark matter phenomenology, we propose a minimal two-component configuration which is an extension of the Standard Model with only three new fields; one scalar and one fermion interact with the thermal soup through Higgs portal, mediated by the other scalar in such a way that the stabilities of dark matter candidates are made simultaneously by an explicit Z2 symmetry. Against the most common freeze-out framework, we look for dark matter particle signatures in the freeze-in scenario by evaluating the relic density and detection signals. A simple distinguishing feature of the model is the lack of dark matter conversion, so the dark matter components act individually and the model can be adapted entirely to both singlet scalar and singlet fermionic models, separately. We find dark matter self-interaction as the most promising approach to probe such feeble models. Although the scalar component satisfies this constraint, the fermionic one refuses it even in the resonant region.

The geochemical fingerprinting of geogenic particles in road deposited dust from Tehran metropolis, Iran: Implications for provenance tracking

Earlier studies focused on tracking anthropogenic sources of toxic trace metals associated with urban deposited dusts, while research on the provenance of natural-sourced dust particles deposited in the urban environment is still rare. We studied the geochemical signature of geogenic particles in street deposited dust (SDs) of Tehran metropolis, Iran, in order to infer their provenance and intensity of post-deposition weathering. The chemical index of alteration (CIA) and Ce anomalies suggested that SDs are chemically immature and partially weathered. The normalized REE pattern and positive Eu anomalies in conjunction with SiO2/Al2O3 values implied the derivation of SDs from intermediate to fully mafic igneous rocks. The REE composition and LaN/SmN, GdN/YbN and LaN/YbN values of Tehran SDs were similar to those found in a Post-Achaean Australian Shale (PAAS) reference, indicating that dust sources from local rocks of Archean greenstone shales in the north of Tehran were the dominant contributor to Tehran SDs. However, CaO enrichment of the SDs in comparison with PAAS implied dilution and mixing with windborne carbonates originating from Alborz formations, as well as from intrinsic anthropogenic sources of the urban environment. Abundance patterns of the major elements and REEs as well as scatter plots of light rare earth elements (LREE) to heavy rare earth elements (HREE) vs. Eu/Eu* and ∑REE vs. CaO (%) confirmed that conclusion. These results improved our knowledge about the nature of SDs and have implications for further investigations of urban deposited dust.

Noncommutative Black Holes at the LHC

Based on the latest public results, 13 TeV data from the Large Hadron Collider at CERN has not indicated any evidence of hitherto tested models of quantum black holes, semiclassical black holes, or string balls. Such models have predicted signatures of particles with high transverse momenta. Noncommutative black holes remain an untested model of TeV-scale gravity that offers the starkly different signature of particles with relatively low transverse momenta. Considerations for a search for charged noncommutative black holes using the ATLAS detector will be discussed.

From the PAMELA mission to the GAMMA-400 project – the indirect search for signatures of dark matter

In 2008, the PAMELA magnetic spectrometer has discovered unpredicted abundance of the ratio of the galactic positron flux to the total positron and electron flux at high energies. It does not agree with the cosmic-ray fluxes calculated using the GALPROP code. This abundance was called the “PAMELA anomalous effect” and one of the explanations of this effect was the appearance of the additional electron and positron flux due to annihilation or decay of the dark matter particles. Later the precision PAMELA results were confirmed by the Fermi-LAT gamma-ray telescope and the AMS-02 magnetic spectrometer. Currently, the new GAMMA-400 project is being developed. The one of its main goals is to search for signatures of dark matter particles, which produce gamma rays. The GAMMA-400 gamma-ray telescope will have unprecedented angular and energy resolutions. PAMELA and GAMMA-400 are the instruments with the best characteristics for their time, which will improve our understanding of the nature of dark matter. At present, the problem of the nature of dark matter still remains the main challenge in high-energy astrophysics.

Erratum: Detecting dark matter through dark photons from the Sun: Charged particle signatures [Phys. Rev. D 93 , 115036 (2016)

Erratum: Detecting dark matter through dark photons from the Sun: Charged particle signatures [Phys. Rev. D <b>93</b> , 115036 (2016)

Erratum: Dark photons from captured inelastic dark matter annihilation: Charged particle signatures [Phys. Rev. D 95 , 075015 (2017)

Received 9 October 2017DOI:https://doi.org/10.1103/PhysRevD.96.099902© 2017 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasDark matterParticle astrophysicsParticle dark matterWeakly interacting massive particlesTechniquesCosmic ray & astroparticle detectorsParticles & FieldsGravitation, Cosmology & Astrophysics

Quantum machine goes in search of the Higgs boson

D-Wave system shows quantum computers can learn to detect particle signatures in mountains of data, but doesn’t outpace conventional methods — yet.

Energetic particle signatures of magnetic field‐aligned potentials over Jupiter's polar regions

AbstractRecent results of the first ever orbit through Jupiter's auroral region by NASA's Juno spacecraft did not show evidence of coherent acceleration in the auroral or polar region. However, in this letter, we show energetic particle data from Juno's Jupiter Energetic‐particle Detector Instrument instrument during the third auroral pass that exhibits conclusive evidence of downward parallel electric fields in portions of Jupiter's polar region. The energetic particle distributions show inverted‐V ion and electron structures in a downward electric current region with accelerated peaked distributions in hundreds of keV to ~1 MeV range. The origin of these large electric potential structures is investigated and discussed within the current theoretical framework of current‐voltage relationships at both Earth and Jupiter. Parallel electric fields responsible for accelerating particles to maintain the aurora/magnetospheric circuit appear to be a common phenomenon among strongly magnetized planets with conducting ionospheres; however, their origin and generation mechanisms are subjects of ongoing research.

Reconstruction of low-momentum protons with the Fine-Grained Detector of the T2K experiment

Low-momentum protons are important in the searches for neutrino interactions with correlated pairs of nucleons, 2p-2h. An attempt using the T2K 0ff-axis near detector data was made to use vertex activity (energy deposited near the vertex of the neutrino interaction) to search for a signature of such low-momentum particles. The analysis is based on extracting a signal of non-reconstructed particles expected to be associated to the vertex activity, which is later used by a neural network to detect the presence of the low-momentum proton in the interaction.

Simplified models for displaced dark matter signatures

We propose a systematic programme to search for long-lived neutral particle signatures through a minimal set of displaced searches (dMETs). Our approach is to extend the well-established dark matter simplified models to include displaced vertices. The dark matter simplified models are used to describe the primary production vertex. A displaced secondary vertex, characterised by the mass of the long-lived particle and its lifetime, is added for the displaced signature. We show how these models can be motivated by, and mapped onto, complete models such as gauge-mediated SUSY breaking and models of neutral naturalness. We also outline how this approach may be used to extend other simplified models to incorporate displaced signatures and to characterise searches for long-lived charged particles. Displaced vertices are a striking signature which is often virtually background free, and thus provide an excellent target for the high-luminosity run of the Large Hadron Collider. The proposed models and searches provide a first step towards a systematic broadening of the displaced dark matter search programme.

Charged particle behavior in localized ultralow frequency waves: Theory and observations

AbstractThe formation and variability of the Van Allen radiation belts are highly influenced by charged particles accelerated via drift‐resonant interactions with ultralow frequency (ULF) waves. In the prevailing theory of drift resonance, the ULF wave amplitude is assumed independent of magnetic longitude. This assumption is not generally valid in Earth's magnetosphere, as supported by numerous observations that point to the localized nature of ULF waves. Here we introduce a longitude dependence of the ULF wave amplitude, achieved via a von Mises function, into the theoretical framework of ULF wave‐particle drift resonance. To validate the revised theory, the predicted particle signatures are compared with observational data through a best fit procedure. It is demonstrated that incorporation of nonlocal effects in drift‐resonance theory provides an improved understanding of charged particle behavior in the inner magnetosphere through the intermediary of ULF waves.

Martian magnetic storms

AbstractThe response of Mars to the major space weather events called interplanetary coronal mass ejections (ICMEs) is of interest for both general planetary solar wind interaction studies and related speculations on their evolutionary consequences—especially with respect to atmosphere escape. Various particle and field signatures of ICMEs have been observed on Phobos‐2, Mars Global Surveyor (MGS), Mars Express (MEX), and now Mars Atmosphere and Volatile EvolutioN (MAVEN). Of these, MAVEN's combined instrumentation and orbit geometry is particularly well suited to characterize both the event drivers and their consequences. However, MAVEN has detected only moderate disturbances at Mars due in large part to the general weakness of the present solar cycle. Nevertheless, the strongest event observed by MAVEN in March 2015 provides an example illustrating how further insights can be gained from available models. Here we first look more closely at what previously run BATS‐R‐US MHD simulations of the combined MAVEN observations tell us about the March 2015 event consequences. We then use analogous models to infer those same responses, including magnetic field topology changes and ionospheric consequences, to a hypothetical extreme ICME at Mars based on STEREO A measurements in July 2012. The results suggest how greatly enhanced, yet realistic, solar wind pressure, magnetic field, and convection electric field combine to produce strong magnetospheric coupling with important consequences for upper atmosphere and ionosphere energization.

Mass spectra features of biomass burning boiler and coal burning boiler emitted particles by single particle aerosol mass spectrometer

In this study, single particle mass spectra signatures of both coal burning boiler and biomass burning boiler emitted particles were studied. Particle samples were suspended in clean Resuspension Chamber, and analyzed by ELPI and SPAMS simultaneously. The size distribution of BBB (biomass burning boiler sample) and CBB (coal burning boiler sample) are different, as BBB peaks at smaller size, and CBB peaks at larger size. Mass spectra signatures of two samples were studied by analyzing the average mass spectrum of each particle cluster extracted by ART-2a in different size ranges. In conclusion, BBB sample mostly consists of OC and EC containing particles, and a small fraction of K-rich particles in the size range of 0.2–0.5μm. In 0.5–1.0μm, BBB sample consists of EC, OC, K-rich and Al_Silicate containing particles; CBB sample consists of EC, ECOC containing particles, while Al_Silicate (including Al_Ca_Ti_Silicate, Al_Ti_Silicate, Al_Silicate) containing particles got higher fractions as size increase. The similarity of single particle mass spectrum signatures between two samples were studied by analyzing the dot product, results indicated that part of the single particle mass spectra of two samples in the same size range are similar, which bring challenge to the future source apportionment activity by using single particle aerosol mass spectrometer. Results of this study will provide physicochemical information of important sources which contribute to particle pollution, and will support source apportionment activities.

Dark photons from captured inelastic dark matter annihilation: Charged particle signatures

The dark sector may contain a dark photon that kinetically mixes with the Standard Model photon, allowing dark matter to interact weakly with normal matter. In previous work we analyzed the implications of this scenario for dark matter capture by the Sun. Dark matter will gather in the core of the Sun and annihilate to dark photons. These dark photons travel outwards from the center of the Sun and may decay to produce positrons that can be detected by the Alpha Magnetic Spectrometer (AMS-02) on the ISS. We found that the dark photon parameter space accessible to this analysis is largely constrained by strong limits on the spin-independent WIMP-nucleon cross section from direct detection experiments. In this paper we build upon previous work by considering the case where the dark sector contains two species of Dirac fermion that are nearly degenerate in mass and couple inelastically to the dark photon. We find that for small values of the mass splitting $\Delta \sim 100 ~\text{keV}$, the predicted positron signal at AMS-02 remains largely unchanged from the previously considered elastic case while constraints from direct detection are relaxed, leaving a region of parameter space with dark matter mass $100 ~\text{GeV} \lesssim m_X \lesssim 10 ~\text{TeV}$, dark photon mass $1 ~\text{MeV} \lesssim m_{A'} \lesssim 100 ~\text{MeV}$, and kinetic mixing parameter $10^{-9} \lesssim \varepsilon \lesssim 10^{-8}$ that is untouched by supernova observations and fixed target experiments but where an inelastic dark sector may still be discovered using existing AMS-02 data.

Single particle mass spectral signatures from vehicle exhaust particles and the source apportionment of on-line PM2.5 by single particle aerosol mass spectrometry

In order to accurately apportion the many distinct types of individual particles observed, it is necessary to characterize fingerprints of individual particles emitted directly from known sources. In this study, single particle mass spectral signatures from vehicle exhaust particles in a tunnel were performed. These data were used to evaluate particle signatures in a real-world PM2.5 apportionment study. The dominant chemical type originating from average positive and negative mass spectra for vehicle exhaust particles are EC species. Four distinct particle types describe the majority of particles emitted by vehicle exhaust particles in this tunnel. Each particle class is labeled according to the most significant chemical features in both average positive and negative mass spectral signatures, including ECOC, NaK, Metal and PAHs species. A single particle aerosol mass spectrometry (SPAMS) was also employed during the winter of 2013 in Guangzhou to determine both the size and chemical composition of individual atmospheric particles, with vacuum aerodynamic diameter (dva) in the size range of 0.2–2μm. A total of 487,570 particles were chemically analyzed with positive and negative ion mass spectra and a large set of single particle mass spectra was collected and analyzed in order to identify the speciation. According to the typical tracer ions from different source types and classification by the ART-2a algorithm which uses source fingerprints for apportioning ambient particles, the major sources of single particles were simulated. Coal combustion, vehicle exhaust, and secondary ion were the most abundant particle sources, contributing 28.5%, 17.8%, and 18.2%, respectively. The fraction with vehicle exhaust species particles decreased slightly with particle size in the condensation mode particles.

Polarization-operator approach to optical signatures of axion-like particles in strong laser pulses

Hypothetical oscillations of probe photons into axion-like particles might be revealed by exploiting the strong fields of high-intensity laser pulses. Considering an arbitrary plane-wave background, we determine the polarization tensor induced by the quantum fluctuations of the axion field and use it to calculate how the polarimetric properties of an initially linear-polarized probe beam are modified. We find that various experimental setups based on contemporary facilities and instrumentation might lead to new exclusion bounds on the parameter space of these particle candidates. The impact of the pulse shape on the discovery potential is studied via a comparison between the cases in which the wave is modulated by a Gaussian envelope and a sin2 profile. This analysis shows that the upper limits resulting from the ellipticity are relatively insensitive to this change, whereas those arising from the rotation of the polarization plane turn out to be more dependent on the field shape.

3-D topological signatures and a new discrimination method for single-electron events and 0νββ events in CdZnTe: A Monte Carlo simulation study

In neutrinoless double beta (0νββ) decay experiments, the diversity of topological signatures of different particles provides an important tool to distinguish double beta events from background events and reduce background rates. Aiming at suppressing the single-electron backgrounds which are most challenging, several groups have established Monte Carlo simulation packages to study the topological characteristics of single-electron events and 0νββ events and develop methods to differentiate them. In this paper, applying the knowledge of graph theory, a new topological signature called REF track (Refined Energy-Filtered track) is proposed and proven to be an accurate approximation of the real particle trajectory. Based on the analysis of the energy depositions along the REF track of single-electron events and 0νββ events, the REF energy deposition models for both events are proposed to indicate the significant differences between them. With these differences, this paper presents a new discrimination method, which, in the Monte Carlo simulation, achieved a single-electron rejection factor of 93.8±0.3 (stat.)% as well as a 0νββ efficiency of 85.6±0.4 (stat.)% with optimized parameters in CdZnTe.

Van Allen Probes observation of a 360° phase shift in the flux modulation of injected electrons by ULF waves

AbstractWe present Van Allen Probe observation of drift‐resonance interaction between energetic electrons and ultralow frequency (ULF) waves on 29 October 2013. Oscillations in electron flux were observed at the period of ∼450 s, which is also the dominant period of the observed ULF magnetic pulsations. The phase shift of the electron fluxes (∼50 to 150 keV) across the estimated resonant energy (∼104 keV) is ∼360°. This phase relationship is different from the characteristic 180° phase shift as expected from the drift‐resonance theory. We speculate that the additional 180° phase difference arises from the inversion of electron phase space density (PSD) gradient, which in turn is caused by the drift motion of the substorm injected electrons. This PSD gradient adjusts the characteristic particle signatures in the drift‐resonance theory, which indicates a coupling effect between the magnetotail and the radiation belt and helps to better understand the wave‐particle interaction in the magnetosphere.

High-energy gamma-ray studying with GAMMA-400 after Fermi-LAT

Fermi-LAT has made a significant contribution to the study of high-energy gamma-ray diffuse emission and the observation of ∼3000 discrete sources. However, one third of all gamma-ray sources (both galactic and extragalactic) are unidentified, the data on the diffuse gamma-ray emission should be clarified, and signatures of dark matter particles in the high-energy gamma-ray range are not observed up to now. GAMMA-400, currently developing gamma-ray telescope, will have the angular (∼0.01° at 100 GeV) and energy (∼1% at 100 GeV) resolutions in the energy range of 10-1000 GeV better than the Fermi-LAT (as well as ground gamma-ray telescopes) by a factor of 5-10 and observe some regions of the Universe (such as Galactic Center, Fermi Bubbles, Crab, Cygnus, etc.) in the highly elliptic orbit (without shading the telescope by the Earth) continuously for a long time. It will permit to identify many discrete sources, to clarify the structure of extended sources, to specify the data on the diffuse emission, and to resolve gamma rays from dark matter particles.