122504641
Trilinear gauge boson couplings and vector boson pair production
55640233
Two dimensional localization of electrons and positrons under high counting rate
Abstract The construction of two wire chambers for high counting rate application is reported. Each chamber includes three wire planes – one anode and two orthogonal cathodes – in which the wires operate as independent proportional counters. One of the chambers is rotated with respect to the other, so that four position coordinates may be encoded for a charged particle crossing both chambers. Spatial resolution is determined by the wire pitch: 1 mm for cathodes, 2 mm for anodes. 320 electronic channels are involved in the detection system readout. Global counting rates in excess of 10 7 events per second have been measured, while the average electron–positron beam intensity may be as high as 3×10 7 events per second.
62199927
Data Storage Accounting and Verification at LHC experiments
All major experiments at the Large Hadron Collider (LHC) need to measure real storage usage at the Grid sites. This information is equally important for resource management, planning, and operations. To verify the consistency of central catalogs, experiments are asking sites to provide a full list of the files they have on storage, including size, checksum, and other file attributes. Such storage dumps, provided at regular intervals, give a realistic view of the storage resource usage by the experiments. Regular monitoring of the space usage and data verification serve as additional internal checks of the system integrity and performance. Both the importance and the complexity of these tasks increase with the constant growth of the total data volumes during the active data taking period at the LHC. The use of common solutions helps to reduce the maintenance costs, both at the large Tier1 facilities supporting multiple virtual organizations and at the small sites that often lack manpower. We discuss requirements and solutions to the common tasks of data storage accounting and verification, and present experiment-specific strategies and implementations used within the LHC experiments according to their computing models.
33958529
CHARGE ASYMMETRIES IN CHARM PHOTO-PRODUCTION
Charm quarks are expected to be produced mainly by the photongluon fusion mechanism in N interactions. However, a small part of the total charm cross section originates in similar processes to those appearing in charm hadroproduction through the resolved (hadronic) component of the photon. Although the contribution of the resolved part of the photon is small at fixed target energies, it can help to understand the small but sizeable charge asymmetries measured in charm hadron photoproduction experiments.
62166279
Distributed data transfers in CMS
The multi-tiered computing infrastructure of the CMS experiment at the LHC depends on the reliable and fast transfer of data between the different CMS computing sites. Data have to be transferred from the Tier-0 to the Tier-l sites for archival in a timely manner to avoid overflowing disk buffers at CERN. Data have to be transferred in bursts to all Tier-2 level sites for analysis as well as synchronized between the different Tier-l sites. The data transfer system is the key ingredient which enables the optimal usage of all distributed resources. The operation of the transfer system consists of monitoring and debugging of transfer issues to guarantee a timely delivery of data to all corners of the CMS computing infrastructure. Further task of transfer operation is to guarantee the consistency of the data at all sites, both on disk and on tape. Procedures to verify the consistency and to debug and repair problems will be discussed.
61326934
No file left behind - monitoring transfer latencies in PhEDEx
The CMS experiment has to move Petabytes of data among dozens of computing centres with low latency in order to make ecient use of its resources. Transfer operations are well established to achieve the desired level of throughput, but operators lack a system to identify early on transfers that will need manual intervention to reach completion. File transfer latencies are sensitive to the underlying problems in the transfer infrastructure, and their measurement can be used as prompt trigger for preventive actions. For this reason, PhEDEx, the CMS transfer management system, has recently implemented a monitoring system to measure the transfer latencies at the level of individual files. For the first time now, the system can predict the completion time for the transfer of a data set. The operators can detect abnormal patterns in transfer latencies early, and correct the issues while the transfer is still in progress. Statistics are aggregated for blocks of files, recording a historical log to monitor the long-term evolution of transfer latencies, which are used as cumulative metrics to evaluate the performance of the transfer infrastructure, and to plan the global data placement strategy. In this contribution, we present the typical patterns of transfer latencies that may be identified with the latency monitor, and we show how we are able to detect the sources of latency arising from the underlying infrastructure (such as stuck files) which need operator intervention.
118975585
Composite vectors in Higgless models at the LHC
In the context of a strongly coupled Electroweak Symmetry Breaking, composite triplet of heavy vectors degenerate in mass belonging to the SU(2)L+R adjoint representation may arise from a new strong interaction invariant under the global SU(2)L × SU(2)R symmetry, which is spontaneously broken down to SU(2)L+R. Assuming that the interactions among these heavy vectors states and with the Standard Model gauge bosons are described by an SU(2)L× SU(2)R/SU(2)L+R Effective Chiral Lagrangian, the heavy vector pair production at the LHC by Vector Boson Fusion and Drell-Yan annihilation is studied in this framework. The expected rates of same sign di-lepton and tri-lepton events from the decay of the composite vectors into Standard Model gauge bosons are computed. The determination of the corresponding SM backgrounds is deferred for a future work.