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Sum rule improved double parton distributions in position space
No full textModels for double parton distributions that are realistic and consistent with theoretical constraints are crucial for a reliable description of double parton scattering. We show how an ansatz that has the correct behaviour in the limit of small transverse distance between the partons can be improved step by step, such as to fulfil the sum rules for double parton distributions with an accuracy around 10%
Highly Crystalline and Semiconducting Imine-Based Two-Dimensional Polymers Enabled by Interfacial Synthesis
No full textSingle‐layer and multi‐layer 2D polyimine films have been achieved through interfacial synthesis methods. However, it remains a great challenge to achieve the maximum degree of crystallinity in the 2D polyimines, which largely limits the long‐range transport properties. Here we employ a surfactant‐monolayer‐assisted interfacial synthesis (SMAIS) method for the successful preparation of porphyrin and triazine containing polyimine‐based 2D polymer (PI‐2DP) films with square and hexagonal lattices, respectively. The synthetic PI‐2DP films are featured with polycrystalline multilayers with tunable thickness from 6 to 200 nm and large crystalline domains (100–150 nm in size). Intrigued by high crystallinity and the presence of electroactive porphyrin moieties, the optoelectronic properties of PI‐2DP are investigated by time‐resolved terahertz spectroscopy. Typically, the porphyrin‐based PI‐2DP 1 film exhibits a p‐type semiconductor behavior with a band gap of 1.38 eV and hole mobility as high as 0.01 cm2 V−1 s−1, superior to the previously reported polyimine based materials
Polymer Foil Windows for Gas-Vacuum Separation in Accelerator Applications
No full textVarious applications in modern particle accelerators or experiments involving high energy particle beams require a gas atmosphere or involve the production of big amounts of residual gas. Among these are, e.g., gas cells for plasma acceleration, gas jet targets, or plasma lenses. As high beam quality and stable operation of RF-accelerator cavities demand for ultra-high vacuum (UHV) conditions, a separation between high pressure and UHV beamline sections is needed. Commonly, this is realized by differential pumping or thin windows, the main advantages of the latter being a simple and compact setup. Nevertheless, the interaction between the window and the beam particles reduces the beamquality via scattering. In this paper, low scattering, low permeability polymer foils that can withstand pressure differences up to 1 bar are investigated as electron beam windows. Measurements, analytical considerations, and simulations on the gas permeation, radiation, and UV resistivity as well as electron beam scattering are presented
Statistics of VHE γ -rays in temporal association with radio giant pulses from the Crab pulsar
No full textThe aim of this study is to search for evidence of a common emission engine between radio giant pulses (GPs) and very-high-energy (VHE, E>100 GeV) gamma-rays from the Crab pulsar. 16 hours of simultaneous observations of the Crab pulsar at 1.4 GHz with the Effelsberg radio telescope and the Westerbork Synthesis Radio Telescope (WSRT), and at energies above 60 GeV with the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes were performed. We searched for a statistical correlation between the radio and VHE gamma-ray emission with search windows of different lengths and different time lags to the arrival times of a radio GP. A dedicated search for an enhancement in the number of VHE gamma-rays correlated with the occurrence of radio GPs was carried out separately for the P1 and P2 phase ranges respectively. 99444 radio GPs have been detected in the radio data sample. We find no significant correlation between the GPs and VHE photons in any of the search windows. Depending on phase cuts and the chosen search windows we find upper limits at 95% confidence level on an increase in VHE gamma-ray events correlated with radio GPs between 7% and 61% of the average Crab pulsar VHE flux for the P1 and P2 phase ranges respectively. This puts upper limits on the flux increase during a radio GP of 12% to 2900% (depending on search window duration and phase cuts) of the pulsed VHE flux. This is the most stringent upper limit on a correlation between gamma-ray emission and radio GPs reported so far.
A NECTAr-based upgrade for the Cherenkov cameras of the H.E.S.S. 12-meter telescopes
No full textThe High Energy Stereoscopic System (H.E.S.S.) is one of the three arrays of imaging atmospheric Cherenkov telescopes (IACTs) currently in operation. It is composed of four 12-meter telescopes and a 28-meter one, and is sensitive to gamma rays in the energy range ~ 30 GeV – 100 TeV. The cameras of the 12-m telescopes recently underwent a substantial upgrade, with the goal of improving their performance and robustness. The upgrade involved replacing all camera components except for the photomultiplier tubes (PMTs). This meant developing new hardware for the trigger, readout, power, cooling and mechanical systems, and new software for camera control and data acquisition. Several novel technologies were employed in the cameras: the readout is built around the new NECTAr digitizer chip, developed for the next generation of IACTs; the camera electronics is fully controlled and read out via Ethernet using a combination of FPGA and embedded ARM computers; the software uses modern libraries such as Apache Thrift, ØMQ and Protocol buffers. This work describes in detail the design and the performance of the upgraded cameras
Constraining the MSSM Higgs sector at the LHC and beyond
No full textThe SM-like Higgs mass of the MSSM is a unique observable which is directly sensitive to the SUSY scale. To fully profit from the experimental precision, the calculation of higher-order corrections is mandatory. I discuss different approaches for their calculation and review the progress achieved in the last years. Afterwards, I show how this calculation is used to define MSSM benchmark scenarios and discuss LHC and future collider constraints on these scenarios
New insights into the microstructural evolution of Ti-5Al-5Mo-5V-3Cr alloy during hot working
No full textMicrostructural features resulting from thermomechanical treatment of the β-metastable Ti-5Al-5Mo-5V-3Cr (Ti-5553) alloy were studied by means of electron backscatter diffraction and X-ray diffraction. The alloy was deformed at 950 °C (β field) and 800 °C (α + β field) with strain rates of 0.001 s−1 and 0.1 s−1 in compression mode up to a compression ratio of 0.5 (true ratio = 0.7). It was concluded that β phase undergoes dynamic recovery both above and below its β-transus temperature, and recovery is more dominant at lower strain rates, which was corroborated by EBSD misorientation measurements. Meanwhile, α phase undergoes not only a process of breakage and globularization, but also decomposition, which contributes to flow softening. The increase in strain rate caused non-uniform recovery at 950 °C and a more intense refinement of α precipitates at 800 °C. Macrotexture evaluation after deformation indicates that β's texture is much stronger than that of α, with its (200) component being the strongest one