scholarly journals Dark Photon Searches Using Displaced Vertices at Low Energye+e-Colliders

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Fabio Bossi
Keyword(s):  
Search Strategy ◽  
Massive Particle ◽  
Interaction Point ◽  
Dark Photon ◽  
Electron Positron ◽  
The Standard Model ◽  
Long Lifetime ◽  
Electron Positron Pair ◽  
Very High ◽  
Primary Interaction

The existence of a new, photon-like, massive particle, theγ′or dark photon, is postulated in several extensions of the Standard Model. These models are often advocated to explain some recent puzzling astrophysical observations, as well as to solve the so far unexplained deviation between the measured and calculated values of the muon anomaly. Dark photons can be produced ate+e-colliders both in continuum events and in vector meson transitions and can eventually decay into an electron-positron pair. For a proper choice of the parameters of the theory, aγ′can have a relatively long lifetime and can therefore be observed as ane+e-vertex well separated by the primary interaction point. This case is discussed in reference to very high luminositye+e-colliders either in construction or under study in several laboratories in the world. It is shown that a search strategy based on the detection of displaced vertices can be in principle very effective in covering a rather wide and to date unexplored region of the theoretical parameters space.

scholarly journals STUDY OF THE ELECTROMAGNETIC TRANSITIONS J/ψ → P l+l- AND PROBE DARK PHOTON

2012 ◽  
Vol 27 (38) ◽  
pp. 1250223 ◽  
Author(s):  
JINLIN FU ◽  
HAI-BO LI ◽  
XIAOSHUAI QIN ◽  
MAO-ZHI YANG
Keyword(s):  
Form Factor ◽  
Internal Conversion ◽  
Massive Particle ◽  
Lepton Pairs ◽  
Data Set ◽  
Decay Modes ◽  
Electromagnetic Structure ◽  
Dark Photon ◽  
The Standard Model ◽  
Shed Light

We study the electromagnetic Dalitz decay modes of J/ψ → P l+l- (P = π0, η or η′). In these decays, the lepton pairs are formed by internal conversion of an intermediate virtual photon with invariant mass ml+l-. Study of the effective-mass spectrum of the l+l- will shed light on the dynamic transition form factor [Formula: see text], which characterizes the electromagnetic structure arising at the vertex of the transition J/ψ to pseudoscalars. We also discuss the direct productions of a GeV scale vector U boson in these processes J/ψ → PU (U → l+l-). It is responsible for mediating a new U(1)d interaction, as recently exploited in the context of weakly interacting massive particle dark matter. In this paper, we firstly use the usual pole approximation for the form factor to estimate the decay rate of J/ψ → P l+l- in the Standard Model. Then the reach of searching for the dark photon is estimated. We suggest that these Dalitz decays can be used to search for the light U boson in the BESIII experiment with a huge J/ψ data set.

scholarly journals Nuclear Adiabatic Effects of Electron-Positron Pairs on the Dynamical Instability of Very-Massive Stars

2021 ◽  
Vol 68 (1 Jan-Feb) ◽  
Author(s):  
Lurwan Garba ◽  
Firas A. Ahmed
Keyword(s):  
Pair Production ◽  
Massive Stars ◽  
Instability Region ◽  
Adiabatic Index ◽  
Dynamical Instability ◽  
Central Temperature ◽  
Electron Positron ◽  
Instability Regions ◽  
Electron Positron Pair ◽  
Very High

The adiabatic effects of electron-positron pair-production on the dynamical instability of very-massive stars is investigated from stellar progenitors of carbon-oxygen cores within the range of 64 M < MCO < 133 M  both with and without rotation. At a very high temperature and relatively low density; the production of electron-positron pairs in the centres of massive stars leads the adiabatic index to below 4/3. The adiabatic quantities are evaluated by constructing a model into a thermodynamically consistent electron-positron equation of state (EoS) table. It is observed that the adiabatic indices in the instability regions of the rotating models are fundamentally positive with central temperature and density. Similarly, the mass of the oxygen core within the instability region has accelerated the adiabatic indices in order to compress the star, while the mass loss and adiabatic index in the non-rotating model exponentially decay. In the rotating models, a small amount of heat is required to increase the central temperature for the end fate of the massive stars. The dynamic of most of the adiabatic quantities show a similar pattern for all the rotating models. The non-rotating model may not be suitable for inducing the instability. Many adiabatic quantities have shown great effects on the dynamical instability of the massive stars due to electron-positron pair-production in their centres. The results of this work would be useful for better understanding of the end fate of very-massive stars.

scholarly journals QED challenges at FCC-ee precision measurements

2019 ◽  
Vol 79 (9) ◽  
Author(s):  
S. Jadach ◽  
M. Skrzypek
Keyword(s):  
Cross Sections ◽  
Spin Asymmetry ◽  
Total Cross Sections ◽  
Electron Positron ◽  
The Standard Model ◽  
Model Predictions ◽  
Lepton Decay ◽  
Qed Effects ◽  
Almost All ◽  
Very High

Abstract The expected experimental precision of the rates and asymmetries in the Future Circular Collider with electron–positron beams (FCC-ee) in the center of the mass energy range 88–365 GeV considered for construction in CERN, will be better by a factor 5–200. This will be thanks to the very high luminosity, a factor up to $$10^5$$105 higher than in the past LEP experiments. Consequently, it poses the extraordinary challenge of improving the precision of the Standard Model predictions by a comparable factor. In particular the perturbative calculations of the trivial QED effects, which have to be removed from the experimental data, are considered to be a major challenge for almost all quantities to be measured at FCC-ee. The task of this paper is to summarize the “state of the art” in this class of the calculations left over from the LEP era and to examine what is to be done to match the precision of the FCC-ee experiments – what kind of technical advancements are necessary. The above analysis will be done for most important observables of the FCC-ee, like the total cross sections near Z and WW threshold, charge asymmetries, the invisible width of Z boson, the spin asymmetry from $$\tau $$τ lepton decay and the luminosity measurement.

scholarly journals VERY HIGH ENERGY GAMMA RAYS FROM e± PAIR HALOS

2009 ◽  
Vol 18 (06) ◽  
pp. 911-927 ◽  
Author(s):  
A. EUNGWANICHAYAPANT ◽  
F. AHARONIAN
Keyword(s):  
Energy Spectrum ◽  
Gamma Rays ◽  
High Energy ◽  
Angular Distributions ◽  
Extragalactic Background Light ◽  
Electron Positron ◽  
Very High Energy ◽  
Energy Gamma ◽  
Electron Positron Pair ◽  
Very High

In this paper we study the formation of giant electron–positron pair halos around the powerful high energy extragalactic sources. We investigate the dependence of radiation of pair halos, in particular the spectral and angular distributions on the energy spectrum of the primary gamma rays, the redshift of the source, and the flux of the extragalactic background light.

scholarly journals Tachyonic field theory and neutrino mass running

Open Physics ◽  
2012 ◽  
Vol 10 (4) ◽  
Author(s):  
Ulrich Jentschura
Keyword(s):  
Field Theory ◽  
Dispersion Relation ◽  
Neutrino Mass ◽  
Background Field ◽  
Tachyonic Field ◽  
Wave Solutions ◽  
Electron Positron ◽  
The Standard Model ◽  
Type Interaction ◽  
Electron Positron Pair

AbstractIn this paper three things are done. (i) We investigate the analogues of Cerenkov radiation for the decay of a superluminal neutrino and calculate the Cerenkov angles for the emission of a photon through a W loop, and for a collinear electron-positron pair, assuming the tachyonic dispersion relation for the superluminal neutrino. The decay rate of a freely propagating neutrino is found to depend on the shape of the assumed dispersion relation, and is found to decrease with decreasing tachyonic mass of the neutrino. (ii)We discuss a few properties of the tachyonic Dirac equation (symmetries and plane-wave solutions), which may be relevant for the description of superluminal neutrinos seen by the OPERA experiment, and discuss the calculation of the tachyonic propagator. (iii) In the absence of a commonly accepted tachyonic field theory, and in view of an apparent “running” of the observed neutrino mass with the energy, we write down a model Lagrangian, which describes a Yukawa-type interaction of a neutrino coupling to a scalar background field via a scalar-minus-pseudoscalar interaction. This constitutes an extension of the standard model. If the interaction is strong, then it leads to a substantial renormalization-group “running” of the neutrino mass and could potentially explain the experimental observations.

scholarly journals New physics searches at the ILC positron and electron beam dumps

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Kento Asai ◽  
Sho Iwamoto ◽  
Yasuhito Sakaki ◽  
Daiki Ueda
Keyword(s):  
Positron Beam ◽  
New Physics ◽  
Beam Dump ◽  
Dark Photon ◽  
Electron Positron ◽  
Pair Annihilation ◽  
Light Scalar ◽  
Production Mechanisms ◽  
Electron Positron Pair ◽  
Higher Sensitivity

Abstract We study capability of the ILC beam dump experiment to search for new physics, comparing the performance of the electron and positron beam dumps. The dark photon, axion-like particles, and light scalar bosons are considered as new physics scenarios, where all the important production mechanisms are included: electron-positron pair-annihilation, Primakoff process, and bremsstrahlung productions.We find that the ILC beam dump experiment has higher sensitivity than past beam dump experiments, with the positron beam dump having slightly better performance for new physics particles which are produced by the electron-positron pair-annihilation.

π-Meson-Elektron-Streuung und Struktur des π-Mesons

1960 ◽  
Vol 15 (12) ◽  
pp. 1023-1030 ◽  
Author(s):  
H. Salecker
Keyword(s):  
Form Factor ◽  
Cross Sections ◽  
High Energy ◽  
Electromagnetic Structure ◽  
Electron Positron ◽  
Pair Annihilation ◽  
Very High Energy ◽  
Scattering Cross Sections ◽  
Electron Positron Pair ◽  
Very High

In this article we propose π-meson-electron scattering as a possibility for investigating the electromagnetic structure of the pion. This experiment requires very high energy, but not necessarily such a high accuracy as the extrapolation procedure of CHEW and Low. After a short discussion of the general properties of the electromagnetic formfactor of the π-meson, we calculate the π—e and the e—π scattering cross sections with form factor. With an energy of 25 GeV and a 10% experimental error we can probe the root mean square radius of the pion down to 0.8 10-13 cm, with 50 GeV down to 0.6·10-13 cm and with 100 GeV to 0.36·10-13 cm. The rms radius of the pion may be larger than previously assumed, because there exists the possibility of a fairly large π — π interaction. A complementary possibility for investigating the electromagnetic structure of the pion consists in electron-positron pair annihilation with the creation of a π± pair. This process will probe the form factor of the π-meson for timelike arguments.

Vacuum polarization and particle creation in the presence of a potential step

2016 ◽  
Vol 31 (02n03) ◽  
pp. 1641031 ◽  
Author(s):  
S. P. Gavrilov ◽  
D. M. Gitman
Keyword(s):  
Electric Potential ◽  
Canonical Quantization ◽  
Particle Creation ◽  
Pair Creation ◽  
Dirac Field ◽  
Potential Step ◽  
Electron Positron ◽  
Physical Impact ◽  
Particle Interpretation ◽  
Electron Positron Pair

We consider QED with strong external backgrounds that are concentrated in restricted space areas. The latter backgrounds represent a kind of spatial x-electric potential steps for charged particles. They can create particles from the vacuum, the Klein paradox being closely related to this process. We describe a canonical quantization of the Dirac field with x-electric potential step in terms of adequate in- and out-creation and annihilation operators that allow one to have consistent particle interpretation of the physical system under consideration and develop a nonperturbative (in the external field) technics to calculate scattering, reflection, and electron-positron pair creation. We resume the physical impact of this development.

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