scholarly journals Probing Scalar and Pseudoscalar Solutions to the g−2 Anomaly

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Fayez Abu-Ajamieh
Keyword(s):  
Parameter Space ◽  
Mass Range ◽  
The Other ◽  
Scalar Case ◽  
Horizontal Branch ◽  
Beam Dump ◽  
Yukawa Couplings ◽  
Dark Photon ◽  
Cosmological Observations ◽  
Open Window

I investigate a class of models with scalar and pseudoscalar solutions to the g−2 anomaly for both the muon and the electron over the mass range of perturbativity (mϕ≲50 GeV), with Yukawa couplings proportional to the lepton’s mass. In particular, I investigate the constraints from BaBar, beam dump experiments, Z decay measured quantities, LEP mono-γ searches, ee⟶ττγ searches, and solar and horizontal branch (HB) star bounds. For a pseudoscalar, I find that no region in the parameter space can simultaneously provide a solution for both the electron and the muon anomalies while maintaining the required form of the couplings, and therefore, the pseudoscalar solution is disfavored. On the other hand, I find for the scalar case that there is an open window above ~30 MeV in the allowed region, but with significant tension with experiment for the region mϕ≳10 GeV. In addition, there is a smaller window between ~350 KeV and 1 MeV that is not ruled out by cosmological observations. Part of the first open window is expected to be covered by the proposed NA64 experiment. Similar analysis can be readily applied to other proposed solutions to the anomaly, such as solutions with Z′ or with the dark photon.

scholarly journals Supernova constraints on an axion-photon-dark photon interaction

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Anson Hook ◽  
Gustavo Marques-Tavares ◽  
Clayton Ristow
Keyword(s):  
Longitudinal Mode ◽  
Transverse Mode ◽  
The Other ◽  
Unusual Feature ◽  
Dark Sector ◽  
Longitudinal Modes ◽  
Dark Photon ◽  
Transverse Modes ◽  
Weakly Coupled ◽  
Photon Coupling

Abstract We present the supernova constraints on an axion-photon-dark photon coupling, which can be the leading coupling to dark sector models and can also lead to dramatic changes to axion cosmology. We show that the supernova bound on this coupling has two unusual features. One occurs because the scattering that leads to the trapping regime converts axions and dark photons into each other. Thus, if one of the two new particles is sufficiently massive, both production and scattering become suppressed and the bounds from bulk emission and trapped (area) emission both weaken exponentially and do not intersection The other unusual feature occurs because for light dark photons, longitudinal modes couple more weakly than transverse modes do. Since the longitudinal mode is more weakly coupled, it can still cause excessive cooling even if the transverse mode is trapped. Thus, the supernova constraints for massive dark photons look like two independent supernova bounds super-imposed on top of each other.

scholarly journals Review of accelerator-based searches for Neutral Long-Lived Particles

2019 ◽  
Vol 43 (169) ◽  
pp. 638-645
Author(s):  
Marta Losada
Keyword(s):  
Parameter Space ◽  
Coupling Strength ◽  
Current Status ◽  
Next Generation ◽  
Fixed Target ◽  
Beam Dump ◽  
Basic Formalism ◽  
Neutral Lepton

In this paper we present the current status of searches for neutral long-lived particles. The basic formalism that allows the determination of the number of expected long-lived particles is presented. Heavy neutral leptons can be a type of long-lived particles. The main observational motivations for the existence of heavy neutral lepton is covered as well. A summary of the main results from both collider searches and fixed target/beam dump experiments is presented. The outlook for next generation experiments and their impact on the parameter space of coupling strength and mass of heavy neutral leptons is also discussed.

scholarly journals Probing the dark axion portal with muon anomalous magnetic moment

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Shao-Feng Ge ◽  
Xiao-Dong Ma ◽  
Pedro Pasquini
Keyword(s):  
Parameter Space ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Muon Anomalous Magnetic Moment ◽  
Negative Contribution ◽  
Dark Photon ◽  
Loop Level

AbstractWe propose a new scenario of using the dark axion portal at one-loop level to explain the recently observed muon anomalous magnetic moment by the Fermilab Muon g-2 experiment. Both axion/axion-like particle (ALP) and dark photon are involved in the same vertex with photon. Although ALP or dark photon alone cannot explain muon $$g-2$$ g - 2 , since the former provides only negative contribution while the latter has very much constrained parameter space, dark axion portal can save the situation and significantly extend the allowed parameter space. The observed muon anomalous magnetic moment provides a robust probe of the dark axion portal scenario.

scholarly journals The impact of structural error on parameter constraint in a climate model

2016 ◽  
Vol 7 (4) ◽  
pp. 917-935 ◽  
Author(s):  
Doug McNeall ◽  
Jonny Williams ◽  
Ben Booth ◽  
Richard Betts ◽  
Peter Challenor ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Parameter Space ◽  
Land Surface ◽  
History Matching ◽  
Climate Model ◽  
The Other ◽  
Future Climate Change ◽  
Amazon Forest ◽  
Structural Error ◽  
Rule Out

Abstract. Uncertainty in the simulation of the carbon cycle contributes significantly to uncertainty in the projections of future climate change. We use observations of forest fraction to constrain carbon cycle and land surface input parameters of the global climate model FAMOUS, in the presence of an uncertain structural error. Using an ensemble of climate model runs to build a computationally cheap statistical proxy (emulator) of the climate model, we use history matching to rule out input parameter settings where the corresponding climate model output is judged sufficiently different from observations, even allowing for uncertainty. Regions of parameter space where FAMOUS best simulates the Amazon forest fraction are incompatible with the regions where FAMOUS best simulates other forests, indicating a structural error in the model. We use the emulator to simulate the forest fraction at the best set of parameters implied by matching the model to the Amazon, Central African, South East Asian, and North American forests in turn. We can find parameters that lead to a realistic forest fraction in the Amazon, but that using the Amazon alone to tune the simulator would result in a significant overestimate of forest fraction in the other forests. Conversely, using the other forests to tune the simulator leads to a larger underestimate of the Amazon forest fraction. We use sensitivity analysis to find the parameters which have the most impact on simulator output and perform a history-matching exercise using credible estimates for simulator discrepancy and observational uncertainty terms. We are unable to constrain the parameters individually, but we rule out just under half of joint parameter space as being incompatible with forest observations. We discuss the possible sources of the discrepancy in the simulated Amazon, including missing processes in the land surface component and a bias in the climatology of the Amazon.

scholarly journals PROPERTIES OF ACCRETION SHOCKS IN VISCOUS FLOWS WITH COOLING EFFECTS

2004 ◽  
Vol 13 (09) ◽  
pp. 1955-1972 ◽  
Author(s):  
SANTABRATA DAS ◽  
SANDIP K. CHAKRABARTI
Keyword(s):  
Shock Wave ◽  
Angular Momentum ◽  
Shock Waves ◽  
Thermodynamic Parameters ◽  
Parameter Space ◽  
Viscous Flows ◽  
Critical Value ◽  
The Other ◽  
Accretion Flows ◽  
Cooling Effects

Low angular momentum accretion flows can have standing and oscillating shock waves. We study the region of the parameter space in which multiple sonic points occur in viscous flows in presence of various cooling effects such as bremsstrahlung and Comptonization. We also quantify the parameter space in which shocks are steady or oscillating. We find that cooling induces effects opposite to heating by viscosity even in modifying the topology of the solutions, though one can never be exactly balanced by the other due to their dissimilar dependence on dynamic and thermodynamic parameters. We show that beyond a critical value of cooling, the flow ceases to contain a shock wave.

Active noise control for open windows

2021 ◽  
Vol 263 (3) ◽  
pp. 3097-3107
Author(s):  
Shahin Sohrabi ◽  
Peter Svensson ◽  
Teresa Pàmies Gómez ◽  
Jordi Romeu Garbi
Keyword(s):  
Control System ◽  
Noise Control ◽  
Active Noise Control ◽  
Sound Intensity ◽  
The Other ◽  
Active Noise ◽  
Open Window ◽  
Pass Through ◽  
Level Reduction ◽  
Suitable Location

Over the last decades, the applications of the active noise control system are broadened. In this study, the active noise control is modeled to reduce the noise pass through an open window. The objective is to define a suitable location for the control sources and error microphones to achieve more noise level reduction at the other side of the window. The performances of the active noise control system are calculated for two different arrangements: (1) the control sources on the edge of the opening and (2) the control sources distributed on the surface of the window. Furthermore, two cost functions are considered to model the noise control system including the minimization of the total squared pressure at cancellation points and the minimization of sound intensity at the surface of the aperture.

scholarly journals Unidirectional Invisibility Induced by Complex Anti-Parity–Time Symmetric Periodic Lattices

2019 ◽  
Vol 9 (18) ◽  
pp. 3808 ◽  
Author(s):  
Hui Cao ◽  
Dong Zhao ◽  
Ming Fang ◽  
Huang Guo ◽  
Yonghong Hu ◽  
...  
Keyword(s):  
Reflection Coefficient ◽  
Parameter Space ◽  
Frequency Band ◽  
Angular Frequency ◽  
Lateral Shift ◽  
The Other ◽  
Wide Frequency Band ◽  
Highly Sensitive ◽  
Highly Sensitive Sensors

Complex anti-parity-time symmetric periodic lattices, in a wide frequency band, can act as unidirectional invisible media. The reflection from one end is suppressed while it is enhanced from the other. Furthermore, unidirectional laser points (ULPs) which correspond to the poles of reflection from one end, arise in the parameter space composed of the permittivity and angular frequency. The phase of the reflection coefficient changes sharply near the ULPs. Subsequently, large lateral shift which is proportional to the slope of phase could be induced for the reflected beam. The study may find great applications in unidirectional invisibility, unidirectional lasers and highly sensitive sensors.

scholarly journals The SHiP physics program

2018 ◽  
Vol 179 ◽  
pp. 01002
Author(s):  
Giovanni De Lellis
Keyword(s):  
Standard Model ◽  
Theoretical Models ◽  
Mass Range ◽  
Beyond The Standard Model ◽  
Beam Dump ◽  
Tau Neutrino ◽  
Physics Program ◽  
Weakly Coupled ◽  
Physics Potential ◽  
The Standard Model

The discovery of the Higgs boson has fully confirmed the Standard Model of particles and fields. Nevertheless, there are still fundamental phenomena, like the existence of dark matter and the baryon asymmetry of the Universe, which deserve an explanation that could come from the discovery of new particles. The SHiP experiment at CERN meant to search for very weakly coupled particles in the few GeV mass domain has been recently proposed. The existence of such particles, foreseen in different theoretical models beyond the Standard Model, is largely unexplored. A beam dump facility using high intensity 400 GeV protons is a copious source of such unknown particles in the GeV mass range. The beam dump is also a copious source of neutrinos and in particular it is an ideal source of tau neutrinos, the less known particle in the Standard Model. Indeed, tau anti-neutrinos have not been directly observed so far. We report the physics potential of such an experiment including the tau neutrino magnetic moment.

scholarly journals Population Models for Massive Globular Clusters

2012 ◽  
Vol 10 (H16) ◽  
pp. 247-248 ◽  
Author(s):  
Young-Wook Lee ◽  
Seok-Joo Joo ◽  
Sang-Il Han ◽  
Chongsam Na ◽  
Dongwook Lim ◽  
...  
Keyword(s):  
Parameter Space ◽  
Globular Clusters ◽  
Heavy Element ◽  
Milky Way ◽  
Population Modeling ◽  
Stellar Populations ◽  
Population Models ◽  
Horizontal Branch ◽  
Element Abundances ◽  
Hr Diagram

Increasing number of massive globular clusters (GCs) in the Milky Way are now turned out to host multiple stellar populations having different heavy element abundances enriched by supernovae. Recent observations have further shown that [CNO/Fe] is also enhanced in metal-rich subpopulations in most of these GCs, including ω Cen and M22 (Marino et al. 2011, 2012). In order to reflect this in our population modeling, we have expanded the parameter space of Y2 isochrones and horizontal-branch (HB) evolutionary tracks to include the cases of normal and enhanced nitrogen abundances ([N/Fe] = 0.0, 0.8, and 1.6). The observed variations in the total CNO content were reproduced by interpolating these nitrogen enhanced stellar models. Our test simulations with varying N and O abundances show that, once the total CNO sum ([CNO/Fe]) is held constant, both N and O have almost identical effects on the HR diagram (see Fig. 1).

scholarly journals Social Influence of Competing Groups and Leaders in Opinion Dynamics

2020 ◽  
Author(s):  
Catherine A. Glass ◽  
David H. Glass
Keyword(s):  
Social Influence ◽  
Group Size ◽  
Computer Simulations ◽  
Parameter Space ◽  
Optimal Strategies ◽  
Opinion Dynamics ◽  
The Other ◽  
Opinion Leaders ◽  
The Impact

Abstract This paper explores the influence of two competing stubborn agent groups on the opinion dynamics of normal agents. Computer simulations are used to investigate the parameter space systematically in order to determine the impact of group size and extremeness on the dynamics and identify optimal strategies for maximizing numbers of followers and social influence. Results show that (a) there are many cases where a group that is neither too large nor too small and neither too extreme nor too central achieves the best outcome, (b) stubborn groups can have a moderating, rather than polarizing, effect on the society in a range of circumstances, and (c) small changes in parameters can lead to transitions from a state where one stubborn group attracts all the normal agents to a state where the other group does so. We also explore how these findings can be interpreted in terms of opinion leaders, truth, and campaigns.

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