We demonstrate measurements of the efficiency of competing Förster-type energy-transfer pathways in single bichromophoric systems by monitoring simultaneously the fluorescence intensity, fluorescence lifetime, and the number of independent emitters with time. Peryleneimide end-capped fluorene trimers, hexamers, and polymers with interchromophore distances of 3.4, 5.9, and on average 42 nm, resp...

The electromagnetic radiation by quark-gluon plasma in a strong magnetic field is calculated. The contributing processes are synchrotron radiation and one-photon annihilation. It is shown that in relativistic heavy-ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) synchrotron radiation dominates over the annihilation. Moreover, it constitutes ...

The CRYSTAL BARREL Collaboration has reported the discovery of the scalar mesons a 0 (1450) 1, 2] and f 0 (1370), together with a relatively narrow f 0 (1500), decaying into 0 0 3], 4], 0 5], K L K L 6] and 4 0 7]. The f 0 (1500) is interpreted as a glueball 8], but its precise KK decay rate has still not been measured precisely 6]. Also, a scalar ss meson decaying mainly into KK is needed to c...

Recent studies showed that positron annihilation methods can provide key insights into the nanostructure and electronic structure of thin film solar cells. In this study, positron annihilation lifetime spectroscopy (PALS) is applied to investigate CdSe quantum dot (QD) light absorbing layers, providing evidence of positron trapping at the surfaces of the QDs. This enables one to monitor their s...

We study the impact of bound state formation on dark matter annihilation rates in models where dark matter interacts via a light mediator, the dark photon. We derive the general cross section for radiative capture into all possible bound states, and point out its nontrivial dependence on the dark matter velocity and the dark photon mass. For indirect detection, our result shows that dark matter...

Positron and its bound state positronium are applied since a few decades as a tool in material investigations. Especially, positron annihilation lifetime spectroscopy (PALS) is widely used, as it gives a possibility to correlate the mean o-Ps lifetime value with cavity size in which annihilation undergoes. The relationship called Tao-Eldrup model [1, 2], describing o-Ps pick-off annihilation, a...

Described here is a proposed experiment to use laser-assisted photorecombination of positrons from a trap-based beam and metal atoms in the gas phase to measure positron–atom binding energies. Signal rates are estimated, based in part upon experience studying resonant annihilation spectra using a trapbased positron beam. While positrons are important in many areas of science and technology incl...

A careful investigation of 1/mb power suppressed effects is crucial for enhancing predictive power of the QCD factorization approach to charmless B decays. It is instructive to systematically investigate the 1/mb effects from soft and hard gluon exchanges, in addition to annihilation topology in the charmless B decays. In this work we try to give a systematic discussion on impact of such soft a...

We present a spectral analysis of the e + e − annihilation emission from the Galactic Centre region based on the first year of measurements made with the spectrometer SPI of the INTEGRAL mission. We have found that the annihilation spectrum can be modelled by the sum of a narrow and a broad 511 keV line plus an ortho-positronium continuum. The broad line is detected (significance 3.2σ) with a f...

Citation Slatyer, Tracy R. "Indirect dark matter signatures in the cosmic dark ages. I. Generalizing the bound on s-wave dark matter annihilation from Planck results. Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please shar...