M. Bluj

Dijet Azimuthal Decorrelations in pp Collisions at sqrt(s) = 7 TeV

Measurements of dijet azimuthal decorrelations in pp collisions at √ s = 7 TeV using the CMS detector at the CERN LHC are presented. The analysis is based on an inclusive dijet event sample corresponding to an integrated luminosity of 2.9 pb−1. The results are compared to predictions from perturbative QCD calculations and various Monte Carlo event generators. The dijet azimuthal distributions are found to be sensitive to initial-state gluon radiation. Submitted to Physical Review Letters ∗See Appendix A for the list of collaboration members ar X iv :1 10 1. 50 29 v2 [ he pex ] 2 1 A pr 2 01 1

Synchronization methods for the PAC RPC trigger system in the CMS experiment

The PAC (pattern comparator) is a dedicated muon trigger for the CMS (Compact Muon Solenoid) experiment at the LHC (Large Hadron Collider). The PAC trigger processes signals provided by RPC (resistive plate chambers), a part of the CMS muon system. The goal of the PAC RPC trigger is to identify muons, measure their transverse momenta and select the best muon candidates for each proton bunch collision occurring every 25 ns. To perform this task it is necessary to deliver the information concerning each bunch crossing from many RPC chambers to the trigger logic at the same moment. Since the CMS detector is large (the muon hits are spread over 40 ns), and the data are transmitted through thousands of channels, special techniques are needed to assure proper synchronization of the data. In this paper methods developed for the RPC signal synchronization and synchronous transmission are presented. The methods were tested during the MTCC (magnet test and cosmic challenge). The performance of the synchronization methods is illustrated by the results of the tests.

Implementation of the data acquisition system for the Resistive Plate Chamber pattern comparator muon trigger in the CMS experiment

This paper presents the implementation of the data acquisition system of the Resistive Plate Chamber (RPC) subdetector in the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) in CERN. The described readout system connects with the RPC detector, the RPC link system, the RPC trigger system and the CMS data acquisition system and creates one of multiple metrological systems in CMS experiment. The readout system receives the data provided by the multiple channels of the link system, filters out the non-triggered data, encapsulates the data into the standard CMS common data format events and sends them to the global data acquisition system. The main problem in the readout system design was to provide a sufficiently large throughput to reliably transfer the data. The implemented system is the scalable solution based on advanced Field Programmable Gate Arrays (FPGA) technology.

Implementation of the data acquisition system for the Overlap Muon Track Finder in the CMS experiment

The Overlap Muon Track Finder (OMTF) is the new system developed during the upgrade of the CMS experiment which includes the upgrade of its Level-1 trigger. It uses the novelty approach to finding muon candidates based on data received from three types of detectors: RPC, DT, and CSC . The upgrade of the trigger system requires also upgrade of the associated Data Acquisition (DAQ) system. The OMTF DAQ transmits the data from the connected detectors that were the basis for the Level-1 trigger decision. To increase its diagnostic potential, it may also transmit the data from a few bunch crossings (BXes) preceding or following the BX, in which the L1 trigger was generated. The paper describes the technical concepts and solutions used in the OMTF DAQ system. The system is still under development. However, it successfully passed the first tests.

OMTF firmware overview

This paper describes firmware architecture of a new part of muon trigger system of the CMS detector – one of four detectors installed along LHC accelerator in CERN. Overlap Muon Track Finder (OMTF) is a new trigger subsystem designed to work in difficult barrel-endcap region of CMS detector. OMTF is designed to receive data from different detector types and process it to select 3 best muon candidates. These muon candidates are then forwarded to Global Muon Trigger (GMT). Performance requirements demanded usage of custom designed hardware. All the data reception and processing takes part in modern, large FPGA device. The IPBus module allows easy firmware control and diagnostics via Ethernet connection.

Measurement of associated production of vector bosons and t t-bar at sqrt(s)= 7 TeV

The first measurement of vector-boson production associated with a top quarkantiquark pair in proton-proton collisions at √ s = 7 TeV is presented. The results are based on a dataset corresponding to an integrated luminosity of 5.0 fb−1, recorded by the CMS detector at the LHC in 2011. The measurement is performed in two independent channels through a trilepton analysis of ttZ events and a samesign dilepton analysis of ttV (V = W or Z) events. In the trilepton channel a direct measurement of the ttZ cross section σttZ = 0.28 +0.14 −0.11 (stat.) +0.06 −0.03 (syst.) pb is obtained. In the dilepton channel a measurement of the ttV cross section yields σttV = 0.43 +0.17 −0.15 (stat.) +0.09 −0.07 (syst.) pb. These measurements have a significance, respectively, of 3.3 and 3.0 standard deviations from the background hypotheses and are compatible, within uncertainties, with the corresponding NLO predictions of 0.137+0.012 −0.016 and 0.306 +0.031 −0.053 pb. Submitted to Physical Review Letters c

FPGA implementation of overlap MTF trigger: preliminary study

The paper presents the concept of the Overlap Muon Track Finder (OTF) trigger for the CMS experiment in CERN as a system implemented in the modern FPGA device. The parametrized description of the complex data processing system, allowing further optimization by iterative simulations and recompilations, is presented. Problems associated with synthesis of such complex systems with currently available synthesis tools, and their workarounds are described.

Object oriented hardware-software test bench for OMTF diagnosis

In this paper the object oriented hardware-software model and its sample implementation of diagnostics for the Overlap Muon Track Finder trigger for the CMS experiment in CERN is described. It presents realization of test-bench for control and diagnosis class of multichannel, distributed measurement systems based on FPGA chips. The test-bench fulfills requirements for system’s rapid changes, configurability and efficiency. This ability is very significant and desirable by expanded electronic systems. The solution described is a software model based on a method of address space management called the Component Internal Interface (CII). Establishment of stable link between hardware and software, as a purpose of designed and realized programming environment, is presented. The test-bench implementation and example of OMTF algorithm test is presented.