Luminosity Scans for Beam Diagnostics

A new type of fast luminosity separation scans ("Emittance Scans") was introduced at the CERN Large Hadron Collider (LHC) in 2015. The scans were performed systematically in every fill with full-intensity beams in physics production conditions at the Interaction Point (IP) of the Compact Muon Solenoid (CMS) experiment. They provide both emittance and closed orbit measurements at a bunch-by-bunch level. The precise measurement of beam-beam closed orbit differences allowed a direct, quantitative observation of long-range beam-beam PACMAN effects, which agrees well with numerical simulations from an improved version of the TRAIN code

A relativistic coupled-channel formalism for the pion form factor

The electromagnetic form factor of a confined quark-antiquark pair is calculated within the framework of point-form relativistic quantum mechanics. The dynamics of theexchanged photon is explicitly taken into account by treating theelectromagnetic scattering of an electron by a meson as a relativistic two-channel problem for a Bakamjian-Thomas type mass operator. This approach guarantees Poincare invariance. Using a Feshbach reduction the coupled-channel problem can be converted into a one-channel problem for the elastic electron-meson channel. By comparing the one-photon-exchange optical potential at the constituent and hadronic levels, we are able to unambiguously identify the electromagnetic meson form factor. Violations of cluster-separability properties, which are inherent in the Bakamjian-Thomas approach, become negligible for sufficiently large invariant mass of the electron-meson system. In the limit of an infinitely large invariant mass, an equivalence with form-factor calculations done in front-form relativistic quantum mechanics is established analytically.Comment: 3 pages, 1 figure, submitted to EPJ Web of Conference

Electromagnetic meson form factor from a relativistic coupled-channel approach

Point-form relativistic quantum mechanics is used to derive an expression for the electromagnetic form factor of a pseudoscalar meson for space-like momentum transfers. The elastic scattering of an electron by a confined quark-antiquark pair is treated as a relativistic two-channel problem for the $q\bar{q}e$ and $q\bar{q}e\gamma$ states. With the approximation that the total velocity of the $q\bar{q}e$ system is conserved at (electromagnetic) interaction vertices this simplifies to an eigenvalue problem for a Bakamjian-Thomas type mass operator. After elimination of the $q\bar{q}e\gamma$ channel the electromagnetic meson current and form factor can be directly read off from the one-photon-exchange optical potential. By choosing the invariant mass of the electron-meson system large enough, cluster separability violations become negligible. An equivalence with the usual front-form expression, resulting from a spectator current in the $q^+=0$ reference frame, is established. The generalization of this multichannel approach to electroweak form factors for an arbitrary bound few-body system is quite obvious. By an appropriate extension of the Hilbert space this approach is also able to accommodate exchange-current effects.Comment: 30 pages, 5 figure

Point-form quantum field theory and meson form factors

We shortly review point-form quantum field theory, i.e. the canonical quantization of a relativistic field theory on a Lorentz-invariant surface of the form $x_\mu x^\mu = \tau^2$. As an example of how point-form quantum field theory may enter the framework of relativistic quantum mechanics we discuss the calculation of the electromagnetic form factor of a confined quark-antiquark pair (e.g. the pion).Comment: 3 pages, 2 figures. Based on a talk presented by W. Schweiger at the 20th European Conference on Few-Body Problems in Physics, September 10-14 2007, Pisa, Ital

Fire as an evolutionary pressure shaping plant traits

6 páginas, 2 figuras, 1 cuadro.Traits, such as resprouting, serotiny and germination by heat and smoke, are adaptive in fire-prone environments. However, plants are not adapted to fire per se but to fire regimes. Species can be threatened when humans alter the regime, often by increasing or decreasing fire frequency. Fire-adaptive traits are potentially the result of different evolutionary pathways. Distinguishing between traits that are adaptations originating in response to fire or exaptations originating in response to other factors might not always be possible. However,fire has been a factor throughout the history of landplant evolution and is not strictly a Neogene phenomenon. Mesozoic fossils show evidence of fire-adaptive traits and, in some lineages, these might have persisted to the present as fire adaptations.JGP acknowledges VIRRA (CGL2009-12048/BOS)support from the Spanish Government. Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the US Government.Peer reviewe

Alteration of early dendritic cell activation by cancer cell lines predisposes immunosuppression, which cannot be reversed by TLR4 stimulation

Dendritic cells (DCs) have shown promise for use in cancer vaccine and cancer immunotherapy studies. However, we demonstrate that cancer cell lines can negatively interfere with DC generation in granulocyte-macrophage colony-stimulating factor (GM-CSF)-derived cultures, although cancer cells are able to enhance CD80 cell surface activation marker and cytokine secretion. Furthermore, in the presence of cancer cells, GM-CSF-derived DCs are unable to stimulate T-cells. Additional stimulation with toll-like receptor 4 cannot fully reverse the suppressive effect of cancer cells or supernatant. Hence, it is imperative to understand the immunosuppressive effects of cancer on DCs in order for DC-based cancer immunotherapy to be successful

Critical Ways of Making: Design Artefacts, De-Computation and Un-Crafting

This workshop intends to elaborate on new and emerging crit- ical approaches that aim to question the nature of contempo- rary computational artefacts. By interrogating interactive sys- tems from a perspective that is focussed on the arrangement of their constituent parts and the relations between them, we seek to challenge the constructive paradigms that might have led to those configurations. In particular, with this workshop we will introduce and further explore De-Computation as a methodology, and Un-Crafting as a method, both targeting a critical examination of contemporary computational arte- facts and the interaction paradigms they follow. Both De- Computation and Un-Crafting approach and explore possi- ble computational futures by critically examining the present. The workshop will include collaborative hands-on activities with reflection in practice and discussions around the topic. We are inviting interdisciplinary viewpoints that will enable us to further ground De-Computation and Un-Crafting in a diverse set of contexts