Pirmin Berger

The observation of Higgs boson production in association with a top quark-antiquark pair is reported, based on a combined analysis of proton-proton collision data at center-of-mass energies of √s = 7, 8, and 13 TeV, corresponding to integrated luminosities of up to 5.1, 19.7, and 35.9  fb^(-1), respectively. The data were collected with the CMS detector at the CERN LHC. The results of statistically independent searches for Higgs bosons produced in conjunction with a top quark-antiquark pair and decaying to pairs of W bosons, Z bosons, photons, τ leptons, or bottom quark jets are combined to maximize sensitivity. An excess of events is observed, with a significance of 5.2 standard deviations, over the expectation from the background-only hypothesis. The corresponding expected significance from the standard model for a Higgs boson mass of 125.09 GeV is 4.2 standard deviations. The combined best fit signal strength normalized to the standard model prediction is 1.26^(+0.31)_(−0.26).

The first layer of the CMS Phase 1 pixel detector will be located at a distance of 3 cm from the interaction point. Pixel hit rates up to 600 MHz/cm2 are expected at the instantaneous luminosity of 2×1034 cm−2 s−1 foreseen by LHC in the coming years. The CMS Phase 1 pixel detector will be in operation until 2024/25 and the total fluence received by the first layer in its lifetime will reach 2–3×1015 neq/cm2 that corresponds to 0.8–1.2 MGy. A new readout chip, called PROC600, to be used for layer 1 modules has been designed at PSI. To validate robust and efficient operation of PROC600, it has been irradiated to doses ranging from 0.6 MGy up to 4.8 MGy. The chip performance before and after irradiation including the pixel hit efficiency will be presented.

We study the symmetries of the post-recombination cosmological magnetohydrodynamical equations which describe the evolution of dark matter, baryons and magnetic fields in a self-consistent way. This is done both at the level of fluid equations and of Vlasov-Poisson-Maxwell equations in phase space. We discuss some consistency relations for the soft limit of the (n + 1)-correlator functions involving magnetic fields and matter overdensities. In particular, we stress that any violation of such consistency relations at equal-time would point towards an inflationary origin of the magnetic field.

An RLC model of ferrite chokes for suppressing common-mode (CM) currents is presented. The equivalent lumped-element circuit parameters are obtained from the frequency-dependent input impedance of a ferrite choke on a wire above the ground plane. This input impedance can be either measured (using vector network analyzer or impedance analyzer), or numerically modeled based on the known ferrite material properties (permittivity and permeability). An example of using both numerical modeling and measurements is provided. Results show good agreement at comparatively low frequencies (below 200 MHz). The upper frequency limit for the proposed equivalent lumped-circuit model is discussed.

Bottlenecks have significant impact on routing options and network exploitation.Therefore, it is essential to know the location of critical areas in order to use the existing infrastructure more efficiently and to expand the network appropriately.This paper presents a method to identify bottlenecks based on delays and to weight them by their significance.As delays can be derived from operational data or from simulations, statements about past operating conditions or forecasts based on simulated operating conditions are possible.The method considers the occurrence of delays at one location and delay increases based on trains' initial delays.It aims to weight additional delay increases higher for punctual trains compared to already heavily delayed trains.This reflects that a deviation from planned times of trains without initial delays has particularly negative impacts on operational quality as these disruptions are indicators for bottlenecks and can lead to delay propagations.Additional delays for already highly delayed trains however have lower significance for operational quality.Furthermore, such delays are often caused by the already existing deviation from the timetable and do not necessarily indicate a bottleneck.Therefore, delays are categorised.Both delay increases and delay category changes can be weighted based on the affected train type to calculate the bottleneck's severity.This gives information on the specific infrastructure's significance concerning the networks performance.Sorting investigated railway lines and stations by their severity gives an overview on the most

view Abstract Citations (11) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Rotational Cooling by Carbon Monoxide in Dark Clouds Berger, P. S. ; Simon, M. Abstract The role of cooling by the rotational transitions of CO in the dark clouds is discussed. It is shown that the strength of the J = 1 transition of 12C160 and 13C160 observed by Penzias et al. in the p Oph cloud is suffident to perrnit the cloud to collapse, with the 12C160 line principally cooling the surface of the cloud and the 13C16O line cooling the interior. Subject headings: interstellar matter - molecules, interstellar Publication: The Astrophysical Journal Pub Date: February 1973 DOI: 10.1086/181149 Bibcode: 1973ApJ...180L..43B full text sources ADS |

The instantaneous luminosity of the Large Hadron Collider will increase to up to 2x1034\;cm−2s−1 by 2023. In order to cope with such luminosities, the pixel detector of the CMS experiment has been replaced in January 2017. The upgraded detector features four sensitive layers in the barrel part. A designated readout chip (PROC600V2) is used for layer 1, which is located only 3 cm from the interaction point and therefore has to handle large particle fluxes. An irradiation campaign has been performed with PROC600V2 to verify its radiation tolerance up to the maximum expected dose for 2017 of 0.2 MGy which proved that no performance loss is expected at the tested doses. Modules for layer 1 have been built with PROC600V2 for the detector production. The quality of every inserted module was assessed in a number of tests, some of which were performed using X-radiation. The characteristics of the modules used in the detector as well as the main failure modes will be presented. It will be shown that the installed modules have an efficiency of over 98% at the maximum expected particle hit rate in CMS.

In the isobaric model for multiple pion production, it is assumed that the isobars need a long lifetime compared to the interaction time. The interaction time for various reactions is estimated from a semiclassical picture of the collisions, and compared with the lifetime of the isobars, which can be estimated from the resonance widths in the total pi -- N cross section. Only at very high velocities of the outgoing particles is the long-isobar-lifetime hypothesis true. A table is computed of isobaric thresholds,'' i.e., the energy of the incoming pions or nucleons needed to insure the validity of the model, for a variety of reactions. The isobaric threshold is considerably larger (by a factor of 2 to 3) than the production threshold for a given re action. (auth)

In high energy particle physics, accelerator- and detector-upgrades always go hand in hand. The instantaneous luminosity of the Large Hadron Collider will increase to up to L = 2×1034cm−2s−1 during Run 2 until 2023. In order to cope with such luminosities, the pixel detector of the CMS experiment has been replaced early 2017. The so-called CMS Pixel phase 1 upgrade detector consists of 1184 modules with new design. An important production step is the module qualification and calibration, ensuring their proper functionality within the detector. This paper summarizes the qualification and calibration tests and results of modules used in the innermost two detector layers with focus on methods using module-internal calibration signals. Extended characterizations on pixel level such as electronic noise and bump bond connectivity, optimization of operational parameters, sensor quality and thermal stress resistance were performed using a customized setup with controlled environment. It could be shown that the selected modules have on average 0.55‰ ± 0.01‰ defective pixels and that all performance parameters stay within their specifications.