Real and virtual photon structure from dijet events

Jet production in $ep$ collisions is sensitive to the partonic structure of photon. The latest measurements of dijet production from the H1 experiment provide new results of the gluon density of real photons at low $x$ and, for the first time, on the partonic density of virtual photons. Properties of the photon remnant were measured as a function of the hard scale defined by the $p_T$ of the jets. The comparison of dijet cross sections with the NLO QCD calculation shows the non-triviality of the concept of virtual photon structure.Comment: 4 pages, Latex with 4 ps figures, references for section 5 updated, Talk presented at DIS99 Workshop at Zeuthen, April 199

Virtual Photon Structure from Jet Production at HERA

The feasibility of measuring parton distribution functions of of virtual photons via the jet production at HERA is investigated.Comment: Contribution to the Workshop on "Future Physics at HERA", eds. G. Ingelman, A. De Roeck, R. Klanner,4 pages, 3 figures, epsfi

SiPM Gain Stabilization Studies for Adaptive Power Supply

We present herein gain stabilization studies of SiPMs using a climate chamber at CERN. We present results for four detectors not tested before, three from Hamamatsu and one from KETEK. Two of the Hamamatsu SiPMs are novel sensors with trenches that reduce cross talk. We use an improved readout system with a digital oscilloscope controlled with a dedicated LabView program. We improved and automized the analysis to deal with large datasets. We have measured the gain-versus-bias-voltage dependence at fixed temperature and gain-versus-temperature dependence at fixed bias voltage to determine the bias voltage dependence on temperature $V(T)$ for stable gain. We show that the gain remains stable to better than $\pm 0.5\%$ in the $20^\circ \rm C - 30^\circ C$ temperature range if the bias voltage is properly adjusted with temperature.Comment: 14 pages, 41 figures, Talk presented at the International Workshop on Future Linear Colliders (LCWS15), Whistler, Canada, 2-6 November 201

Parton content of the real photon: astrophysical implications

We possess convincing experimental evidence for the fact that the real photon has non-trivial parton structure. On the other hand, interactions of the cosmic microwave background photons with high energy particles propagating through the Universe play an important role in astrophysics. In this context, to invoke the parton content could be convenient for calculations of the probabilities of different processes involving these photons. As an example, the cross section of inclusive resonant $W^+$ boson production in the reaction $\nu \gamma\to W^+X$ is calculated by using the parton language. Neutrino--photon deep inelastic scattering is considered.Comment: 4 pages, 2 figures. The spin states of the initial particles in the reaction $\nu\gamma\to W^+X$ are correctly treated. As a result, the corresponding cross section becomes two times greater than the one from the previous version. Some changes in the tex

Implementation of the Transit Node Routing Algorithm in the AgentPolis Simulation Framework

Výpočet nejkratší vzdálenosti mezi dvěma vrcholy v grafu je častým problémem v informatice. Spousta aplikací obsahuje nějakou komponentu pro výpočet nejkratších vzdáleností. Tato práce se zaměřuje na problém výpočtu nejkratší vzdálenosti ve vážených orientovaných grafech. Práce prozkoumává metody, které ze vstupního grafu předpočítají nějaké pomocné struktury, které poté urychlují samotné dotazy. Tento přístup je vhodný v situacích, kdy je potřeba zodpovědět velké množství dotazů a graf se nemění mezi jednotlivými dotazy. Výsledkem této práce je knihovna pro výpočet nejkratších vzdáleností pomocí tří metod nazvaných Contraction Hierarchies, Transit Node Routing a Transit Node Routing s využitím Arc Flags. Výsledná knihovna dokáže pro libovolný vážený orientovaný graf předpočítat pomocné struktury potřebné pro dané tři metody a následně je využít pro rychlý výpočet nejkratších vzdáleností. Výkon implementace byl vyhodnocen na grafech získaných z reálných silničních sítí. Implementace metody Transit Node Routing založené na Contraction Hierarchies s využitím Arc Flags obsažená ve výsledné knihovně dokáže vypočíst nejkratší vzdálenost mezi dvěma náhodnými vrcholy grafu 10 000krát rychleji než Dijkstrův Algoritmus pro největší z testovaných grafů, a přitom potřebuje pouze 50krát více paměti.Computation of the shortest distance from one node to another in a graph is a common problem in computer science. Many applications contain a component for the shortest distance computation. This thesis focuses on the problem of shortest distance computation in directed weighted graphs. The thesis explores methods that precompute some auxiliary structures from the input graph to speed up the queries. This approach is suitable in cases where a large amount of queries needs to be answered and the graph does not change between the queries. The result of this thesis is a library for shortest distance computation using three such methods called Contraction Hierarchies, Transit Node Routing, and Transit Node Routing with Arc Flags. The library can preprocess directed weighted graphs to obtain the auxiliary structures needed by the three methods and then answer shortest distance queries quickly by utilizing those structures. The implementation is evaluated on graphs obtained from real road networks. The implementation of the Transit Node Routing with Arc Flags method based on Contraction Hierarchies present in the library answers random shortest distance queries more than 10 000 times faster than Dijkstra's Algorithm on the largest test graph, while only needing about 50 times the amount of memory

The Time Structure of Hadronic Showers in highly granular Calorimeters with Tungsten and Steel Absorbers

The intrinsic time structure of hadronic showers influences the timing capability and the required integration time of hadronic calorimeters in particle physics experiments, and depends on the active medium and on the absorber of the calorimeter. With the CALICE T3B experiment, a setup of 15 small plastic scintillator tiles read out with Silicon Photomultipliers, the time structure of showers is measured on a statistical basis with high spatial and temporal resolution in sampling calorimeters with tungsten and steel absorbers. The results are compared to GEANT4 (version 9.4 patch 03) simulations with different hadronic physics models. These comparisons demonstrate the importance of using high precision treatment of low-energy neutrons for tungsten absorbers, while an overall good agreement between data and simulations for all considered models is observed for steel.Comment: 24 pages including author list, 9 figures, published in JINS