Over the past 60 years a rich sample of experimental results concerning the inclusive production of
π
-
mesons has been obtained spanning a range from about 3 GeV to 13 TeV in interaction energy. ...This paper attempts a model-independent overview of these results with the aim at obtaining an internally consistent data description on a dense grid over the three inclusive variables transverse momentum, rapidity or Feynman
x
F
and interaction energy. The study concentrates on the non-perturbative sector of the strong interaction by limiting the transverse momenta to
p
T
<
1.3 GeV/c. The three-dimensional interpolation which is mandatory and necessary for this aim is shown to provide a controlled systematic precision of better than 5%. This accuracy allows for a critical inspection of each of the 40 experiments concerned in turn. It also allows precision tests of some of the physics concepts developed around inclusive processes like energy scaling, “thermal” production and the evolution of transverse momenta.
•Standardized test levels for high voltage direct current cable systems are not yet available.•Electromagnetic transient studies are an essential tool for insulation co-ordination.•Overvoltage ...analysis for the symmetrical monopolar scheme configuration.•Overvoltage parameters such as peak value, rise time and gradient are dependent on the cable route length.
This contribution focuses on high voltage direct current (HVDC) transmission systems comprising modular multilevel converters (MMC) equipped with half-bridge (HB) submodules and analyses cable voltage stresses during various station internal as well as dc side faults. In order to examine relevant overvoltage characteristics affecting HVDC cable systems, a systematic approach to evaluate overvoltage stresses is presented and an extensive set of time-domain simulations is analysed for schemes operating in symmetrical monopolar configuration. Obtained results are relevant for considerations on insulation co-ordination of HVDC cable systems and for a comprehensive definition of high voltage testing requirements.
•Thorough analysis of rigid bipolar configuration to reflect increasing interest.•Solution to bridge the gap between monopolar and full bipolar configuration.•Development of advanced control and ...balancing scheme for asymmetric power transfer.•Implementation of line loss estimation enables exact power set point achievement.•Validation of ac fault-ride through capability in electromagnetic transients software.
High voltage direct current transmission schemes equipped with modular multilevel converter technology are considered in several realized and planned bulk power transmission projects. Especially in the case of dc cable links with high system lengths, the rigid bipolar configuration presents a suitable compromise between power rating, cost-efficiency and converter redundancy. Caused by the absence of a metallic return path, system degrees of freedom are reduced in contrast to the bipolar configuration with dedicated metallic return. Therefore, the dc currents in positive and negative bipolar subsystem are not independent. This leads to new challenges and motivates the development of advanced control and balancing concepts for rigid bipolar schemes. This paper focuses on balanced and unbalanced ac grid operating conditions with subsystem-independent active power set points in an ac split-busbar scenario, which has not yet been covered in literature. In order to validate the presented methodology, case studies are performed in electromagnetic transient software.
The production of protons, anti-protons, neutrons, deuterons and tritons in minimum bias p+C interactions is studied using a sample of 385 734 inelastic events obtained with the NA49 detector at the ...CERN SPS at 158 GeV/c beam momentum. The data cover a phase space area ranging from 0 to 1.9 GeV/c in transverse momentum and in Feynman
x
from −0.8 to 0.95 for protons, from −0.2 to 0.3 for anti-protons and from 0.1 to 0.95 for neutrons. Existing data in the far backward hemisphere are used to extend the coverage for protons and light nuclear fragments into the region of intra-nuclear cascading. The use of corresponding data sets obtained in hadron–proton collisions with the same detector allows for the detailed analysis and model-independent separation of the three principle components of hadronization in p+C interactions, namely projectile fragmentation, target fragmentation of participant nucleons and intra-nuclear cascading.
•Fault detection and handling in full-bridge bipolar MMC-HVDC links.•Transients in mixed overheadline and cable HVDC transmission.•Control-wise dc fault current interruption to avoid IGBT ...blocking.•MMC-HVDC protection parameter determination.•Converter-internal differential protection.
In order to address challenges caused by an increasing need for power transmission, embedded bipolar HVDC links utilizing Modular Multilevel Converter (MMC-HVDC) technology present a preferred solution as several operational and dynamic advantages compared to conventional ac grid enforcement are provided. In this paper, an approach to quickly detect and handle internal as well as dc-side faults in a full-bridge bipolar MMC-HVDC link is presented. Due to non-technical reasons and environmental constraints, the system is comprised of mixed overheadline-cable (OHL-cable) transmission and single point solid grounding with dedicated metallic return (DMR). To validate and evaluate the proposed concept, detailed electromagnetic transient (EMT) simulations are provided. These highlight effects of mixed transmission system design on transient voltage and current stresses as well as on converter-internal quantities.
New data on the production of charged kaons in p+p interactions are presented. The data come from a sample of 4.8 million inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c ...beam momentum. The kaons are identified by energy loss in a large TPC tracking system. Inclusive invariant cross sections are obtained in intervals from 0 to 1.7 GeV/c in transverse momentum and from 0 to 0.5 in Feynman x. Using these data as a reference, a new evaluation of the energy dependence of kaon production, including neutral kaons, is conducted over a range from 3 GeV to
collider energies.
Recent data on proton and pion production in p+C interactions from the CERN PS and SPS accelerators are used in conjunction with other available data sets to perform a comprehensive survey of ...backward hadronic cross sections. This survey covers the complete backward hemisphere in the range of lab angles from 10 to 180 degrees, from 0.2 to 1.4 GeV/
c
in lab momentum and from 1 to 400 GeV/
c
in projectile momentum. Using the constraints of continuity and smoothness of the angular, momentum and energy dependences a consistent description of the inclusive cross sections is established which allows the control of the internal consistency of the nineteen available data sets.
The production of charged pions in minimum bias p+C interactions is studied using a sample of 377000 inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The ...data cover a phase space area ranging from 0 to 1.8 GeV/c in transverse momentum and from -0.1 to 0.5 in Feynman xF. Inclusive invariant cross sections are given on a grid of 270 bins per charge, thus offering for the first time a dense coverage of the projectile hemisphere and of the cross-over region into the target fragmentation zone.
The new data on pion production in p+C interactions from the NA49 experiment at the CERN SPS are used for a detailed study of hadronization in the collision of protons with light nuclei. The ...comparison to the extensive set of data from p+p collisions obtained with the same detector allows for the separation and extraction of the projectile and target contributions to the pion yield both in longitudinal and in transverse momentum.
Are there S = -2 pentaquarks? Fischer, H. G.; Wenig, S.
The European physical journal. C, Particles and fields,
09/2004, Letnik:
37, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Recent evidence for pentaquark baryons in the channels \(\Xi^-\pi^-\), \(\Xi^-\pi^ + \) and their anti-particles claimed by the NA49 collaboration is critically confronted with the vast amount of ...existing data on \(\Xi\) spectroscopy which was accumulated over the past decades. It is shown that the claim is inconsistent with these data. In addition two further exotic channels of the pentaquark type available in the NA49 data are investigated. It is argued that this study leads to internal inconsistency with the purported signals.
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