# Preprints

 2020-05-1914:05 [PUBDB-2020-02166] Preprint/Report et al Superradiant Cherenkov-Wakefield Radiation as THz Source for FEL Facilities [DESY-20-081; arXiv:2005.05640]   An electron beam passing through a tube which is lined on the inside with a dielectric layer will radiate energy in the THz range due to the interaction with the boundary. The resonant enhancement of certain frequencies is conditioned by structure parameters as tube radius and permittivity of the dielectric layer. [...] OpenAccess: PDF PDF (PDFA); 2020-05-1410:52 [PUBDB-2020-01844] Preprint/Report et al Line and surface defects for the free scalar field [arXiv:2005.02413]   For a single free scalar field in $d \geq 2$ dimensions, almost all the unitary conformal defects must be trivial. The only possible exceptions are monodromy defects in $d \geq 4$ and co-dimension three defects in $d \geq 5$. [...] OpenAccess: PDF PDF (PDFA); 2020-05-1410:38 [PUBDB-2020-01841] Preprint/Report Servant, G. High-Temperature Electroweak Symmetry Non-Restoration from New Fermions and Implications for Baryogenesis [arXiv:2002.05174 DESY-19-207]   The strength of electroweak symmetry breaking may substantially differ in the early Universe compared to the present day value. In the Standard Model, the Higgs vacuum expectation value (vev) vanishes and electroweak symmetry gets restored at temperatures above $\sim 160$ GeV due to the Higgs field interactions with the high-temperature plasma. [...] OpenAccess: PDF PDF (PDFA); 2020-05-1213:09 [PUBDB-2020-01806] Preprint/Report et al Time-Scales for Nonlinear Processes in Preheating after Multifield Inflation with Nonminimal Couplings [arXiv:2005.00433]   We have conducted extensive lattice simulations to study the post-inflation dynamics of multifield models involving nonminimal couplings. We explore the parameter dependence of preheating in these models and describe the various time-scales that control such nonlinear processes as energy transfer, re-scattering, and the approach to radiation-domination and thermalization. [...] OpenAccess: PDF PDF (PDFA); 2020-05-1213:00 [PUBDB-2020-01805] Preprint/Report et al Dark Matter bound-state formation at higher order: a non-equilibrium quantum field theory approach [arXiv:2002.07145]   The formation of meta-stable dark matter bound states in coannihilating scenarios could efficiently occur through the scattering with a variety of Standard Model bath particles, where light bosons during the electroweak cross over or even massless photons and gluons are exchanged in the t-channel. The amplitudes for those higher-order processes, however, are divergent in the collinear direction of the in- and out-going bath particles if the mediator is massless. [...] OpenAccess: PDF PDF (PDFA); 2020-05-1212:54 [PUBDB-2020-01804] Preprint/Report et al Covert symmetries in the neutrino mass matrix [DESY-20-008; arXiv:1910.00576]   The flavour neutrino puzzle is often addressed by considering neutrino mass matrices m with a certain number of vanishing entries (m$_{ij}$ = 0 for some values of the indices), since a reduction in the number of free parameters increases the predictive power. Symmetries that can enforce textures zero can also enforce a more general type of conditions f(m$_{ij}$) = 0 with f some function of the matrix elements m$_{ij}$. [...] OpenAccess: PDF PDF (PDFA); 2020-05-1212:22 [PUBDB-2020-01801] Preprint/Report et al Straightening of Superconducting HERA Dipoles for the Any-Light-Particle-Search Experiment ALPS II [DESY-20-070; arXiv:2004.13441]   At DESY the ALPS II experiment is being installed in the HERA tunnel to search for axion like particles (ALPs). A laser beam will be injected into a string of superconducting HERA dipole magnets, to produce ALPs. [...] OpenAccess: PDF PDF (PDFA); 2020-05-1212:20 [PUBDB-2020-01800] Preprint/Report Talbert, J. Generic dijet soft functions at two-loop order: uncorrelated emissions [DESY-19-157; Nikhef 2020-007; QFET-2020-01; SI-HEP-2020-11; arXiv:2004.08396]   We extend our algorithm for automating the calculation of two-loop dijet soft functions to observables that do not obey the non-Abelian exponentiation theorem, i.e. to those that require an independent calculation of the uncorrelated-emission contribution. [...] OpenAccess: PDF PDF (PDFA); 2020-05-1212:11 [PUBDB-2020-01797] Preprint/Report et al Vacancy-Hydrogen Interaction in Niobium during Low-Temperature Baking [DESY-20-074; arXiv:2004.13450]   A recently discovered modified low-temperature baking leads to reduced surface losses and an increase of the accelerating gradient of superconducting TESLA shape cavities. We will show that the dynamics of vacancy-hydrogen complexes at low-temperature baking lead to a suppression of lossy nanohydrides at 2\,K and thus a significant enhancement of accelerator performance. [...] OpenAccess: PDF PDF (PDFA); 2020-05-1114:26 [PUBDB-2020-01794] Preprint/Report et al Search for disappearing tracks in proton-proton collisions at $\sqrt{s} =$ 13 TeV [CERN-EP-2020-043; CMS-EXO-19-010; FERMILAB-PUB-20-192-CMS; arXiv:2004.05153]   A search is presented for long-lived charged particles that decay within the volume of the silicon tracker of the CMS experiment. Such particles can produce events with an isolated track with no associated hits in the muon detectors, little energy deposited in the calorimeters, and missing hits in the outermost layers of the silicon tracker. [...] OpenAccess: PDF PDF (PDFA);