scholarly journals Dark Atoms and the Positron-Annihilation-Line Excess in the Galactic Bulge

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
J.-R. Cudell ◽  
M. Yu. Khlopov ◽  
Q. Wallemacq
Keyword(s):  
Dark Matter ◽  
Positron Annihilation ◽  
Cross Section ◽  
Ground State ◽  
Galactic Bulge ◽  
Annihilation Line ◽  
Electron Positron ◽  
The Galaxy ◽  
Stable Particles ◽  
Electron Positron Pair

It was recently proposed that stable particles of charge −2,O--, can exist and constitute dark matter after they bind with primordial helium in O-helium (OHe) atoms. We study here in detail the possibility that this model provides an explanation for the excess of gamma radiation in the positron-annihilation line from the galactic bulge observed by INTEGRAL. This explanation assumes that OHe, excited to a 2s state through collisions in the central part of the Galaxy, deexcites to its ground state via anE0transition, emitting an electron-positron pair. The cross-section for OHe collisions with excitation to 2s level is calculated and it is shown that the rate of such excitations in the galactic bulge strongly depends not only on the mass of O-helium, which is determined by the mass ofO--, but also on the density and velocity distribution of dark matter. Given the astrophysical uncertainties on these distributions, this mechanism constrains theO--mass to lie in two possible regions. One of these is reachable in the experimental searches for stable multicharged particles at the LHC.

scholarly journals Detecting dark photons from atomic rearrangement in the galaxy

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
James Eiger ◽  
Michael Geller
Keyword(s):  
Dark Matter ◽  
Ground State ◽  
Bound State ◽  
Current Data ◽  
Dark Sector ◽  
Atomic Process ◽  
The Galaxy ◽  
Atomic States ◽  
Atomic Rearrangement

Abstract We study a new dark sector signature for an atomic process of “rearrangement” in the galaxy. In this process, a hydrogen-like atomic dark matter state together with its anti-particle can rearrange to form a highly-excited bound state. This bound state will then de-excite into the ground state emitting a large number of dark photons that can be measured in experiments on Earth through their kinetic mixing with the photon. We find that for DM masses in the GeV range, the dark photons have enough energy to pass the thresholds of neutrino observatories such as Borexino and Super-Kamiokande that can probe for our scenario even when our atomic states constitute a small fraction of the total DM abundance. We study the corresponding bounds on the parameters of our model from current data as well as the prospects for future detectors.

scholarly journals COHERENT PAIR PRODUCTION IN DEFORMED CRYSTALS WITH A COMPLEX BASE

2006 ◽  
Vol 20 (25) ◽  
pp. 1617-1627 ◽  
Author(s):  
A. R. MKRTCHYAN ◽  
A. A. SAHARIAN ◽  
V. V. PARAZIAN
Keyword(s):  
Differential Cross Section ◽  
Single Crystal ◽  
Cross Section ◽  
High Energy ◽  
Pair Creation ◽  
Deformation Field ◽  
Crystallographic Axis ◽  
Electron Positron ◽  
Coherent Pair ◽  
Electron Positron Pair

We investigate the coherent electron–positron pair creation by high-energy photons in a periodically deformed single crystal with a complex base. The formula for the corresponding differential cross-section is derived for an arbitrary deformation field. The conditions are specified under which the influence of the deformation is considerable. The case is considered in detail when the photon enters into the crystal at small angles with respect to a crystallographic axis. The results of the numerical calculations are presented for SiO 2 single crystal and Moliere parametrization of the screened atomic potentials in the case of the deformation field generated by the acoustic wave of S type. In dependence of the parameters, the presence of deformation can either enhance or reduce the pair creation cross-section. This can be used to control the parameters of the positron sources for storage rings and colliders.

scholarly journals ON THE THEORY OF COHERENT PAIR PRODUCTION IN CRYSTALS IN THE PRESENCE OF ACOUSTIC WAVES

2002 ◽  
Vol 17 (39) ◽  
pp. 2571-2580 ◽  
Author(s):  
A. R. MKRTCHYAN ◽  
A. A. SAHARIAN ◽  
L. SH. GRIGORYAN ◽  
B. V. KHACHATRYAN
Keyword(s):  
Differential Cross Section ◽  
Cross Section ◽  
Acoustic Waves ◽  
High Energy ◽  
Pair Creation ◽  
Wave Number ◽  
Electron Positron ◽  
Coherent Pair ◽  
Electron Positron Pair ◽  
Coherent Part

The influence of hypersonic waves excited in a single crystal is investigated on the process of electron–positron pair creation by high-energy photons. The coherent part of the corresponding differential cross-section is derived as a function of the amplitude and wave number of the hypersound. The values of the parameters are specified for which the latter affects remarkably on the pair creation cross-section. It is shown that under certain conditions the presence of hypersonic waves can result in enhancement of the process cross-section.

scholarly journals A REEVALUATION OF EVIDENCE FOR LIGHT NEUTRAL BOSONS IN NUCLEAR EMULSIONS

2011 ◽  
Vol 20 (08) ◽  
pp. 1787-1803 ◽  
Author(s):  
F. W. N. DE BOER ◽  
C. A. FIELDS
Keyword(s):  
Cross Section ◽  
Pion Production ◽  
Production Cross ◽  
Statistical Significance ◽  
Projectile Energy ◽  
Direct Production ◽  
Electron Positron ◽  
Data Yield ◽  
Electron Positron Pair ◽  
Combined Data

Electron–positron pair production data obtained by bombardment of emulsion detectors with either cosmic rays or projectiles with masses between 1 and 207 amu and kinetic energies between 18 GeV and 32 TeV have been reanalyzed using a consistent and conservative model of the background from electromagnetic pair conversion. The combined data yield a spectrum of putative neutral bosons decaying to e+e- pairs, with masses between 3 and 20 MeV /c2 and femtosecond lifetimes. The statistical significance against background for these "X-bosons" varies between 2σ and 8σ. The cross-section for direct production of X-bosons increases slowly with projectile energy, remaining over 1,000 times smaller than the pion production cross-section.

scholarly journals Is this the possible explanation to the unpredictability of the direction of of gamma ray emission during electron-positron annihilation ?

2021 ◽  
Author(s):  
Jayaram as
Keyword(s):  
Quantum Mechanics ◽  
Positron Annihilation ◽  
Alternative Explanation ◽  
Gamma Ray ◽  
Classical Mechanics ◽  
Annihilation Process ◽  
Electron Positron Annihilation ◽  
Electron Positron ◽  
Gamma Ray Emission ◽  
Electron Positron Pair

This paper shows the various parameters to be considered, duringelectron - positron annihilation. Many of the theories suggest that directionof gamma ray emission cannot be predicted. This is normally justifiedby using quantum mechanics. This paper gives an alternative explanation tounpredictability of gamma ray direction. This explanation does not require thelogic of quantum mechanics. It requires modification of classical mechanics toaccount of the forces between colliding particles.The logic of this paper is thatin case of pair production involving gamma ray and electron- positron pair, theclassical mechanics calculation itself shows perfect conservation of directionand magnitude of momentum. There, a little recoiling of the nucleus is observedfor conserving momentum. Hence it must be possible to use classicalmechanics for the process of electron- positron annihilation process also.

scholarly journals Extinct radio pulsars as a source of subrelativistic positrons

2020 ◽  
Vol 498 (2) ◽  
pp. 2089-2094
Author(s):  
Ya N Istomin ◽  
D O Chernyshov ◽  
D N Sob’yanin
Keyword(s):  
Neutron Stars ◽  
Relativistic Electron ◽  
Photon Absorption ◽  
Cascade Process ◽  
Radio Pulsars ◽  
Positron Source ◽  
Plasma Production ◽  
Annihilation Line ◽  
Electron Positron ◽  
The Galaxy

ABSTRACT Extinct radio pulsars, in which stationary, self-sustaining generation of a relativistic electron–positron plasma becomes impossible when rotation brakes down, can be sources of a subrelativistic flux of positrons and electrons. We assume that the observed excess of positrons in the bulge and the disc of the Galaxy is associated with these old neutron stars. The production of pairs in their magnetospheres occurs due to one-photon absorption of gamma quanta of the Galactic and extragalactic backgrounds. The cascade process of plasma production leads to the flux of positrons escaping from the open magnetosphere ≃3 × 1034 s−1. The total flux of positrons from all old Galactic neutron stars with rotational periods 1.5 < P < 35 s is ≃3 × 1043 s−1. The energy of positrons is less than ≃10 MeV. The estimated characteristics satisfy the requirements for the positron source responsible for the 511-keV Galactic annihilation line.

Vector meson production in electron positron annihilation process

2021 ◽  
pp. 2150120
Author(s):  
Weihua Yang ◽  
Fei Huang
Keyword(s):  
Differential Cross Section ◽  
Vector Meson ◽  
Positron Annihilation ◽  
Cross Section ◽  
Differential Cross ◽  
High Energy ◽  
Annihilation Process ◽  
Electron Positron Annihilation ◽  
Electron Positron ◽  
Fragmentation Functions

When tunneling events induced by nontrivial configurations of the quantum chromodynamics gauge fields are taken into consideration, parity violating quantities emerge. Based on this consideration, parity-odd fragmentation functions can be introduced in the high energy reactions. In this paper, we calculate the differential cross-section in terms of both the parity-even and parity-odd fragmentation functions in semi-inclusive electron positron annihilation process. Semi-inclusive implies that not only a vector meson in one jet but also the back-to-back jet is measured in this reaction. According to the differential cross-section, we further calculate the azimuthal asymmetries and hadron polarizations in terms of fragmentation functions. A method of measuring the parity violating effects in the semi-inclusive annihilation process is suggested.

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