Unstable Particles Research Articles

Tails of Instability and Decay: a Hydrodynamic Perspective

In the context of quantum field theory (QFT), unstable particles are associated with complex-valued poles of two-body scattering matrices in the unphysical sheet of rapidity space. The Breit-Wigner formula relates this pole to the mass and life-time of the particle, observed in scattering events. In this paper, we uncover new, dynamical signatures of unstable excitations and show that they have a strong effect on the non-equilibrium properties of QFT. Focusing on a 1+1D integrable model, and using the theory of Generalized Hydrodynamics, we study the formation and decay of unstable particles by analysing the release of hot matter into a low-temperature environment. We observe the formation of tails and the decay of the emitted nonlinear waves, in sharp contrast to the situation without unstable excitations. We also uncover a new phenomenon by which a wave of a stable population of unstable particles may persist without decay for long times. We expect these signatures of the presence of unstable particles to have a large degree of universality. Our study shows that the out-of-equilibrium dynamics of many-body systems can be strongly affected not only by the spectrum, but also by excitations with finite life-times.

Astrophysical information from the Rayleigh-Jeans Tail of the CMB

One of the explanations for the recent EDGES-LOW band 21 cm measurements of a strong absorption signal around 80 MHz is the presence of an excess radio background to the Cosmic Microwave Background (CMB). Such excess can be produced by the decay of unstable particles into small mass dark photons which have a non-zero mixing angle with electromagnetism. We use the EDGES-LOW band measurements to derive joint constraints on the properties of the early galaxies and the parameters of such a particle physics model for the excess radio background. A Bayesian analysis shows that a high star formation efficiency and X-ray emission of 4–7 × 1048 erg per solar mass in stars are required along with a suppression of star formation in halos with virial temperatures ≲ 2 × 104 K. The same analysis also suggests a 68 percent credible intervals for the mass of the decaying dark matter particles, it's lifetime, dark photon mass and the mixing angle of the dark and ordinary photon oscillation of [10-3.5, 10-2.4] eV, [101.1, 102.7] × 13.8 Gyr, [10-12.2, 10-10] eV and [10-7, 10-5.6] respectively. This implies an excess radio background which is ≈ 5.7 times stronger than the CMB around 80 MHz. This value is a factor ∼ 3 higher than the previous predictions which used a simplified model for the 21 cm signal.

Mud pumping in the roadbed of ballastless high-speed railway

Mud pumping that is deliberately avoided in the design of a ballastless high-speed railway still occurs and induces extraordinary track vibrations. In this study, in situ investigations and laboratory tests were performed to disclose the initiation and development of mud pumping detected in the field. The in situ investigations indicated that mud pumping principally appeared at both ends of the concrete base up to a maximum distance of 2 m. Precipitation, instead of groundwater, was found to be the water source triggering mud pumping; this infiltrated the graded gravel roadbed through the detachments of the ends of the overlying concrete bases due to the whipping effect. Once mud pumping occurred, the vibrations of concrete bases were aggravated and caused severe track settlements under train loads. The results of laboratory tests indicated that the infiltrated rainwater was retained in the roadbed above the less permeable subgrade, and the roadbed contained an unstable particle skeleton with excessive plastic fine particles, both of which provided favourable conditions to form mud pumping under dense high-speed train loads. Soil particles of less than 7·1 mm in diameter migrated during mud pumping; these first accumulated at the lower roadbed, then gradually migrated to the upper roadbed, actuated by the hydraulic gradient generated, and were finally pumped out through the detachments around the expansion gaps, thereby resulting in large amounts of voids in the roadbed and a vicious cycle if not treated in a timely fashion. These features of mud pumping in ballastless tracks differ from those of ballasted tracks and will benefit the development of remediation measures and improvement of slab track designs.

Застосування 1,3-дифенілтріазена як антидетонаційної присадки до автомобільних бензинів.

The article presents an overview of the chemical principle of anti-detonation additives, which are now widely used in gasolines. The most probable reactions that occur with hydrocarbons in the fuel-air mixture when it enters the combustion chamber of an internal combustion engine are considered. These reactions are mainly represented by cracking with the formation of active radicals, which in turn enter into the oxidation reaction with oxygen. Formed in this way, hydroperoxides take part in chain oxidation reactions, which contributes to the effect of detonation combustion of the fuel-air mixture. In view of this reaction, it is proposed to use 1,3-diphenyltriazene, which belongs to the class of diazocompounds, as an anti-detonation additive for motor gasolines. The principle of anti-detonation effect of this substance is, first of all, the possibility of its thermal decomposition in the temperature range 130-160 °C. In this case, nitrogen, phenyl and aniline radicals will be formed. The phenyl radical, which is one of the most unstable particles, due to its increased reactivity reacts instantly with the most active fuel radicals: atomic hydrogen; methyl and hydroxyl radicals. At the same time, there is a high probability of formation of molecular hydrogen, toluene and phenol among the products of such interactions. These are stable compounds that are not able to continue and maintain the chain oxidation reactions that occur during the combustion of the fuel-air mixture in the combustion chamber of the engine. Thus, in the reaction zone with the direct participation of phenyl radicals there is a decrease in the concentration of radicals initiating chain oxidative reactions, which leads to chain breakage. Also, a very positive aspect of the use of 1,3-diphenyltriazene is that it can be used in compositions with alcohols or with methyl tert-butyl ether in straight-run gasoline fractions of oil, their mixtures with the fractions of the catalytic cracking and of the riforming. The using of the proposed additive in the composition of gasoline fully meets the requirements of the environmental safety standard Euro-5. Key words: gasoline, detonation resistance, additives, 1,3-diphenyltriazene, cracking, oxidation, radicals, internal combustion engine Corresponding author A. B. Grigorov, e-mail:grigorovandrey@ukr.net

Possibility of transporting material from Ceres to NEO region via 8:3 MMR with Jupiter

ABSTRACT In this work, we investigate the possibility of transporting material to the NEO region via the 8:3 MMR with Jupiter, potentially even material released from the dwarf planet Ceres. By applying the FLI map method to the 8:3 MMR region in the orbital plane of Ceres, we were able to distinguish between stable and unstable orbits. Subsequently, based on the FLI maps (for mean anomaly M = 60° and also M = 30°), 500 of the most stable and 500 of the most unstable particles were integrated for $15\, \mathrm{Myr}$ for each map. Long-term integration in the case of M = 60° showed that most of the stable particles evolved, in general, in uneventful ways with only 0.8 per cent of particles reaching the limit of q ≤ 1.3 au . However, in the case of M = 30°, a stable evolution was not confirmed. Over 40 per cent of particles reached orbits with q ≤ 1.3 au and numerous particles were ejected to hyperbolic orbits or orbits with a > 100 au. The results for stable particles indicate that short-term FLI maps are more suitable for finding chaotic orbits, than for detecting the stable ones. A rough estimate shows that it is possible for material released from Ceres to get to the region of 8:3 MMR with Jupiter. A long-term integration of unstable particles in both cases showed that transportation of material via 8:3 MMR close to the Earth is possible.

Luminous solar neutrinos. I. Dipole portals

Solar neutrinos upscattering inside the Earth can source unstable particles that can decay inside terrestrial detectors. Contrary to naive expectations we show that when the decay length is much shorter than the radius of the \emph{Earth} (rather than the detector), the event rate is independent of the decay length. In this paper we study a transition dipole operator (neutrino dipole portal) and show that Borexino's existing data probes previously untouched parameter space in the 0.5--20 MeV regime, complementing recent cosmological and supernova bounds. We briefly comment on similarities and differences with luminous dark matter and comment on future prospects for analogous signals stemming from atmospheric neutrinos.

Influence of intense laser fields on measurable quantities in [formula omitted]-boson decay

In principle, this paper suggests powerful laser technology as a promising instrument that can be experimentally useful to control the lifetime and branching ratio for an unstable particle decay. In a recent paper [ arXiv:2101.00224], we calculated theoretically the W−-boson leptonic decay (W−→ℓ−ν̄ℓ) in the presence of a circularly polarized laser and we showed that the laser significantly contributed to the diminution of the leptonic decay rate. In this paper, as a continuation of the previous one, we mainly deal with the theoretical calculation of the W−-boson hadronic decay (W−→qq̄′) and we combine the analytical results obtained in both papers to examine the effect of an intense laser, in terms of its field strength and frequency, on the three measurable quantities in W−-boson decay (total decay rate, lifetime and branching ratios). It was found that the laser has notably contributed to the reduction of the total decay rate leading to a longer lifetime. Most importantly, the two branching ratios (one for leptons and the other for hadrons) are affected (increased or decreased) by the presence of a strong external electromagnetic field. Combined together, these two complementary works may provide an in-depth and comprehensive study that would be useful for any experimental investigation in the future.

Decaying dark matter: simulations and weak-lensing forecast

Despite evidence for the existence of dark matter (DM) from very high and low redshifts, a moderate amount of DM particle decay remains a valid possibility. This includes both models with very long-lived yet unstable particles or mixed scenarios where only a small fraction of dark matter is allowed to decay. In this paper, we investigate how DM particles decaying into radiation affect non-linear structure formation. We look at the power spectrum and its redshift evolution, varying both the decay lifetime (τ) and the fraction of decaying-to-total dark matter (f), and we propose a fitting function that reaches sub-percent precision below k ∼ 10 h/Mpc. Based on this fit, we perform a forecast analysis for a Euclid-like weak lensing (WL) survey, including both massive neutrino and baryonic feedback parameters. We find that with WL observations alone, it is possible to rule out decay lifetimes smaller than τ = 75 Gyr (at 95 percent CL) for the case that all DM is unstable. This constraint improves to τ = 182 Gyr if the WL data is combined with CMB priors from the Planck satellite and to τ = 275 Gyr if we further assume baryonic feedback to be fully constrained by upcoming Sunyaev-Zeldovich or X-ray data. The latter shows a factor of 3.2 improvement compared to constraints from CMB data alone. Regarding the scenario of a strongly decaying sub-component of dark matter with τ ∼ 30 Gyr or lower, it will be possible to rule out a decaying-to-total fraction of f > 0.49, f > 0.21, and f > 0.13 (at the 95 percent CL) for the same three scenarios. We conclude that the upcoming stage-IV WL surveys will allow us to significantly improve current constraints on the stability of the dark matter sector.

Electromagnetic Proton Beam Instabilities in the Inner Heliosphere: Energy Transfer Rate, Radial Distribution, and Effective Excitation

Abstract Differential flows among different ion species are often observed in the solar wind, and such ion differential flows can provide the free energy to drive Alfvén/ion cyclotron and fast-magnetosonic/whistler instabilities. Previous works mainly focused on ion beam instability under the parameters representative of the solar wind nearby 1 au. In this paper we further study proton beam instability using the radial models of the magnetic field and plasma parameters in the inner heliosphere. We explore a comprehensive distribution of proton beam instability as functions of the heliocentric distance and the beam speed. We also perform a detailed analysis of the energy transfer between unstable waves and particles and quantify how much the free energy of the proton beam flows into unstable waves and other kinds of particle species (i.e., proton core, alpha particle, and electron). This work clarifies that both parallel and perpendicular electric fields are responsible for the excitation of oblique Alfvén/ion cyclotron and oblique fast-magnetosonic/whistler instabilities. Moreover, this work proposes an effective growth length to estimate whether the instability is efficiently excited or not. It shows that oblique Alfvén/ion cyclotron instability, oblique fast-magnetosonic/whistler instability, and oblique Alfvén/ion beam instability can be efficiently driven by proton beams drifting at the speed ∼600–1300 km s−1 in the solar atmosphere. In particular, oblique Alfvén/ion cyclotron waves driven in the solar atmosphere can be significantly damped therein, leading to solar corona heating. These results are helpful for understanding proton beam dynamics in the inner heliosphere and can be verified through in situ satellite measurements.

Chirping ion cyclotron emission (ICE) on NSTX-U

We report here on the discovery on NSTX-U of a qualitatively new type of non-thermal emission from plasmas in the ion-cyclotron frequency range (ICE). This new type of ICE is weakly damped, γdamp/ω ICE ≈ 0.14%, low order eigenmodes, excited by a fast ion population radially located near an internal transport barrier. The ICE appears as repetitive bursts with durations of ≈1 ms, and the bursts exhibit frequency chirps upwards and/or downwards with maximum δf/f ≈ 1%. We refer to this chirping ICE as ch-ICE. The bursts are longer than the typical ICE bursts of ≈100 μs reported previously for NSTX and NSTX-U, for simplicity, NSTX(-U). The chirping resembles that seen in modeling of weakly unstable fast particle driven instabilities (cf, Berk et al 1997 Phys. Lett. A 234 213). These data also provide some preliminary indications of non-linear coupling between the ch-ICE harmonics. Despite extensive experimental and theoretical studies of ICE, theoretical understanding of ICE remains qualitative at best. The detailed experimental observations of ICE from NSTX(-U) find a wide variation in the ICE characteristics. The new observations of ch-ICE presented here, combined with the characteristics of ICE on NSTX(-U) previously reported (Fredrickson et al 2019 Phys. Plasmas 26 032111), could guide the development of more complete theoretical models of ICE.

Perturbative versus Non-Perturbative Quantum Field Theory: Tao’s Method, the Casimir Effect, and Interacting Wightman Theories

We dwell upon certain points concerning the meaning of quantum field theory: the problems with the perturbative approach, and the question raised by ’t Hooft of the existence of the theory in a well-defined (rigorous) mathematical sense, as well as some of the few existent mathematically precise results on fully quantized field theories. Emphasis is brought on how the mathematical contributions help to elucidate or illuminate certain conceptual aspects of the theory when applied to real physical phenomena, in particular, the singular nature of quantum fields. In a first part, we present a comprehensive review of divergent versus asymptotic series, with qed as background example, as well as a method due to Terence Tao which conveys mathematical sense to divergent series. In a second part, we apply Tao’s method to the Casimir effect in its simplest form, consisting of perfectly conducting parallel plates, arguing that the usual theory, which makes use of the Euler-MacLaurin formula, still contains a residual infinity, which is eliminated in our approach. In the third part, we revisit the general theory of nonperturbative quantum fields, in the form of newly proposed (with Christian Jaekel) Wightman axioms for interacting field theories, with applications to “dressed” electrons in a theory with massless particles (such as qed), as well as unstable particles. Various problems (mostly open) are finally discussed in connection with concrete models.

Improved intolerance intervals and size bounds for a Schelling-type spin system

A spin system with long-range interacting particles is considered. The initial states of the particles are chosen uniformly at random and they are located at the nodes of a flat torus . Each node of the torus is connected to the nodes located in an l ∞-ball of radius w in the toroidal space centered at itself and it is assumed that h is exponentially larger than w 2. According to the states of the neighboring particles and based on the value of a common intolerance threshold τ, every particle is labeled ‘stable’ or ‘unstable’. Furthermore, unstable particles that can potentially become stable by flipping their states are labeled as ‘p-stable’. Finally, p-stable particles that remain so for a random, independent and identically distributed waiting time, will flip their states and become stable. When the waiting times have exponential distributions and τ ⩽ 1/2, this model is equivalent to a Schelling model of self-organized segregation in an open system, a zero-temperature Ising model with Glauber dynamics, or an asynchronous cellular automaton with extended Moore neighborhoods. Previous work has shown that if the intolerance parameter of the model τ ∈ (≈0.488, ≈0.512)\\{1/2}, then for a sufficiently large neighborhood of interaction N = (2w + 1)2, any particle will end up in an exponentially large ‘monochromatic’ region of particles of the same state, with high probability (w.h.p.). In this paper the above results are extended to the larger interval τ ∈ (≈0.433, ≈0.567)\\{1/2}, and the bounds on the size of the monochromatic ball are also improved by exponential factors. Furthermore, it is shown that when particles are placed on the infinite lattice rather than on a flat torus, for the values of τ mentioned above, sufficiently large N, and after a sufficiently long evolution time, any particle is contained in a large monochromatic ball of size exponential in N, w.h.p.

Particle yields in pp interactions at GeV interpreted in the statistical hadronization model

Following the recent measurement of several hadron yields by NA61/SHINE collaboration, the unified set of yields of particles produced in proton–proton collisions at = 17.3 GeV (laboratory beam momentum 158 GeV/c) is evaluated, combining the results of the NA49 and NA61/SHINE collaborations at the CERN SPS. With the statistical hadronization code Thermal-Fist we confirm the unacceptably high value of χ 2, both in the canonical and grand canonical—strangeness canonical approach, and the common volume for all the hadrons. The use of the energy-dependent width of the Breit–Wigner parametrization for the mass distributions of unstable particles improves the quality of the description of particle yields only slightly. We confirm the observation that exclusion of the ϕ meson yield makes the fit result more reasonable. The complete experimental data set of particle yields can be also reasonably fitted if the canonical volumes of hadrons without and with open strangeness are allowed to vary independently. The canonical volume of strangeness was found to be larger than that for non-strange hadrons. The femtoscopy measurements with kaon pairs and pion pairs at 27.4, 63 and 900 GeV are not precise enough to confirm or reject this observation. The model with the best-fit parameters allows to predict the yields of several not yet measured particles emitted from p + p at = 17.3 GeV.

Simultaneous Reciprocal and Real Space X-Ray Imaging of Time-Evolving Systems

Imaging the (sub)micron scale over large areas with high temporal resolution becomes increasingly necessary for the development and investigation of novel materials under realistic operation conditions. Small angle x-ray scattering imaging methods provide micro- and nanoscale structural information of materials. A fundamental shortcoming of such methods is the long acquisition time required to investigate macroscopic objects. In this work, we propose a single shot imaging method that allows reciprocal space sensitivity at a local level while maintaining spatial resolution for imaging macroscopic objects. We use an instrument that is sensitive to the ultrasmall angle x-ray scattering range and utilize it to image unstable polydisperse particle systems. This allows us to observe in real time the evolution of the local average particle diameter due to the stratification of the microparticles.

Destroying the structure of extracellular polymeric substance to improve the dewatering performance of waste activated sludge by ionic liquid

The disposal and resource utilization of waste activated sludge (WAS) is a big challenge for its high moisture content. Ionic liquid (IL), 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][OTf]), was innovatively used as a conditioner to improve the dewatering performance of WAS. The WAS was characterized by flocs size, three-dimensional excitation-emission matrix (3D-EEM), zeta potential, Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) for the investigation of intensification mechanism. The results showed that the dewatering performance of WAS conditioned by [EMIM][OTf] was significantly improved. The moisture content was successfully decreased to 64.99±0.92 %, and the intensification mechanism was investigated. The results showed that the structures of extracellular polymeric substance (EPS) were destroyed by [EMIM][OTf]. It brought a sharp decrease of the contents of polysaccharides (PS), proteins (PN), humic acid (HA) and fulvic acid (FA) in tightly bound extracellular polymeric substance (TB-EPS) structure. The inactivation of microbial cells promoted the disintegration of flocs. Large flocs were converted into unstable small particles and biopolymers. In addition, the negative charges of WAS were also neutralized for dissolution of biopolymers in [EMIM][OTf], and the electrostatic repulsion between flocs was weakened. [EMIM][OTf] was easily recycled five times. The research results indicate that specific IL, such as [EMIM][OTf], is a potential conditioner to improve the dewatering performance of WAS.

CP violation in mixing and oscillations in a toy model for leptogenesis with quasi-degenerate neutrinos

We study the sources of CP violation for baryogenesis models with quasi-degenerate neutrinos. Our approach is to use the renormalized propagator in a quantum field theory model of neutrino oscillations, paying close attention to unitarity requirements. From the probabilities of lepton number violating processes obtained in this way, we derive a source term for the time evolution of the lepton asymmetry. The source term has contributions that can be identified with CP violation from mixing, oscillations and interference between both. Given that this source term does not involve processes with unstable particles in the initial or final states, neither does it require to calculate number densities of neutrinos, no subtraction of real intermediate states must be performed. In equilibrium the source term is null, as demanded by unitarity and CPT invariance, due to a cancellation between the terms coming from CP violation in mixing and oscillations. The calculations are done in a simple scalar toy model, and the resummed propagator is diagonalized at first order in the decay widths over the mass difference. We also comment on the effect of the interference term, which is mild at the order we work, but seems to become more important with increasing degeneracy.

Dependence of the surfactant solutions surface tension on the concentration and on the temperature

This paper presents the dependence of the surface tension on the surfactant concentration and on the temperature for anionic cetyltrimethylammonium bromide (CTAB) with a concentration of 1 mmol/L and two-ionic lauryl hydroxysultaine (LHS) with a concentration of 2.8 mmol/L. At a low concentration of the surfactant, the surface tension drops sharply at a certain temperature, and at a high concentration it changes slightly, much slower than surface tension of the pure water. Surface tension rapidly drops because micelles in the bulk become unstable and surfactant particles relocate to the interface.

Discovery potential of FASER\u03bd with contained vertex and through-going events

FASERν is a newly proposed detector whose main mission is to detect the neutrino flux from the collision of the proton beams at the ATLAS Interaction Point (IP) during the run III of the LHC in 2022–2024. We show that this detector can also test certain beyond standard model scenarios, especially the ones in which the neutrino interaction with matter fields can produce new unstable particles decaying back into charged leptons. Models of this kind are motivated by the MiniBooNE anomaly. We show that, if the new physics involves multi-muon production by neutrinos scattering off matter fields, including the neutrino flux interactions in the rock before the detector in the analysis (i.e., accounting for the through-going muon pairs) can significantly increase the effective detector mass and its sensitivity to new physics. We propose a concrete model that can give rise to such a multi-muon signal.

Magnetic nanocomposite derived from Nopal cactus biopolymer and magnetic nanoparticles used for the microalgae flocculation of aqueous solution

A magnetic nanocomposite, using a Nopal cactus-derived biopolymer in combination with NH4OH-modified cobalt superparamagnetic (CoFe2O4) nanoparticles, was developed as a green flocculant system for recovery of microalgae from aqueous solutions. The obtained magnetic nanomaterials were subsequently dispersed in the biopolymer matrix with the support of ultrasonic waves. The effects of various factors on pectin extraction, fabrication of nanocomposites, and the flocculation process of microalgae were also studied. The characteristics of the obtained materials (pectin, modified magnetic nanoparticles, and nanocomposites) were evaluated via X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, thermogravimetric-differential scanning calorimetry, Fourier transform infrared spectroscopy, and zeta potential analysis. The optimal conditions for pectin extraction from Nopal cactus, as well as the fabrication of magnetic nanoparticles, modified magnetic nanoparticles, and nanocomposite were reported. The characteristic data of the fabricated materials showed heat resistance and abundant surface functional groups with high magnetization. The observed flocculation was attributed to the aggregation of unstable and small particles through surface charge neutralization, electrostatic patching, and/or bridging after addition of flocculants. The results showed that the nanocomposites could be a potential green flocculant for recovering microalgae with low cost and high efficiency.

Sedimentation rate of microfluidized sugarcane juice

Sugarcane juice contains unstable particles that readily undergo agglomeration and sedimentation. In this work, microfluidization was used as a processing tool to generate a possible solution to the sedimentation problem in sugarcane juice for the first time. Stoke's law was used to determine the particle sedimentation rate. Experiments were devised to explore the majority of the pressure range of microfluidization (50–200 MPa) with variation in processing cycles (1–7). Particle size and apparent viscosity of sugarcane juice were determined. Microscopic analysis was also carried out to visualize the effect of microfluidization on the particles in the juice. Microfluidization in the pressure range of 50-150 MPa with less than 7 cycles of processing reduced the size of suspended juice particles successfully. Results revealed that 150 MPa pressure with 5 cycles was suitable for sugarcane juice processing as it generates the lowest particle size (~437 nm) and minimum particle sedimentation rate (4.91 × 10−2 mm/day).