OpenAccess

We report measurements of the branching fraction and $CP$ asymmetry in $B^{0} \to \pi^{0} \pi^{0}$ decays reconstructed at Belle II in an electron-positron collision sample containing $198 \times 10^{6}$$B\overline{B}$ pairs. We measure a branching fraction $\mathcal{B}(B^0 \rightarrow \pi^0 \pi^0) = (1.38 \pm 0.27 \pm 0.22) \times 10^{-6}$ and a $\it CP$ asymmetry $\mathcal{A}_{\rm CP}(B^0 \rightarrow \pi^0 \pi^0) = 0.14 \pm 0.46 \pm 0.07$, where the first uncertainty is statistical and the second is systematic..

The H1 collaboration has been asked to present to the October PRC meeting a “close to full” simula- tion of the first level part of the Fast Track Trigger algorithm, including the current understanding of the prospects for providing information to the level 1 H1 central trigger. This document contains the requested information, including a near to final specification of the full level 1 system. [...]

Space charge induced micro bunch instabilities, amplified in cascadedbunch compression stages, spoil the phase space of compressed bunches and leadto unstable seeding. To “heat” up the bunch with an external laser and induce anuncorrelated energy spread to suppresses the micro bunching instabilities, a shortundulator will be installed in front of the first compression chicane. [...]

DESY is planning to upgrade its current storage ring PETRA III into the ultra-lowemittance photon source PETRA IV. The current H6BA cell design for the PETRA IV latticewill allow for insertion devices of up to 4 m length in the standard straight sections. [...]

In 2018 the high energy X-ray beamlines P07 and P21b at DESY's storage ring PETRA III received new undulators. The two identical devices were built by an industry collaboration of Research Instruments GmbH and Kyma S.p.A. [...]

The origin of the Fermi bubbles, which constitute two gamma-ray emitting lobes above and below the Galactic plane, remains unclear. The possibility that this Fermi bubbles gamma-ray emission originates from hadronic cosmic rays advected by a subsonic Galactic outflow, or breeze, is here explored. [...]

Superluminous supernovae (SLSNe) are a rare class of stellar explosions with luminosities ∼ 10–100 times greater than ordinary core-collapse supernovae. One popular model to explain the enhanced optical output of hydrogen-poor (Type I) SLSNe invokes energy injection from a rapidly spinning magnetar. [...]