Kristan Allan Hahn

We report the results of a global analysis of dark matter simplified models (DMSMs) with leptophobic mediator particles of spin one, considering the cases of both vector and axial-vector interactions with dark matter (DM) particles and quarks. We require the DMSMs to provide all the cosmological DM density indicated by Planck and other observations, and we impose the upper limits on spin-independent and -dependent scattering from direct DM search experiments. We also impose all relevant LHC constraints from searches for monojet events and measurements of the dijet mass spectrum. We model the likelihood functions for all the constraints and combine them within the MasterCode framework, and probe the full DMSM parameter spaces by scanning over the mediator and DM masses and couplings, not fixing any of the model parameters. We find, in general, two allowed regions of the parameter spaces: one in which the mediator couplings to Standard Model (SM) and DM particles may be comparable to those in the SM and the cosmological DM density is reached via resonant annihilation, and one in which the mediator couplings to quarks are $\lesssim 10^{-3}$ and DM annihilation is non-resonant. We find that the DM and mediator masses may well lie within the ranges accessible to LHC experiments. We also present predictions for spin-independent and -dependent DM scattering, and present specific results for ranges of the DM couplings that may be favoured in ultraviolet completions of the DMSMs.

We describe the new CDF Level 2 Trigger, which was commissioned during Spring 2005. The upgrade was necessitated by several factors that included increased bandwidth requirements, in view of the growing instantaneous luminosity of the Tevatron, and the need for a more robust system, since the older system was reaching the limits of maintainability. The challenges in designing the new system were interfacing with many different upstream detector subsystems, processing larger volumes of data at higher speed, and minimizing the impact on running the CDF experiment during the system commissioning phase. To meet these challenges, the new system was designed around a general purpose motherboard, the PULSAR, which is instrumented with powerful FPGAs and modern SRAMs, and which uses mezzanine cards to interface with upstream detector components and an industry standard data link (S-LINK) within the system.

The high instantaneous luminosities expected following the upgrade of the Large Hadron Collider (LHC) to the High-Luminosity LHC (HL-LHC) pose major experimental challenges for the CMS experiment.A central component to allow efficient operation under these conditions is the reconstruction of charged particle trajectories and their inclusion in the hardwarebased trigger system.There are many challenges involved in achieving this: a large input data rate of about 20-40 Tb/s; processing a new batch of input data every 25 ns, each consisting of about 15,000 precise position measurements and rough transverse momentum measurements of particles ("stubs"); performing the pattern recognition on these stubs to find the trajectories; and producing the list of trajectory parameters within 4 µs.This paper describes a proposed solution to this problem, specifically, it presents a novel approach to pattern recognition and charged particle trajectory reconstruction using an all-FPGA solution.The results of an end-to-end demonstrator system, based on Xilinx Virtex-7 FPGAs, that meets timing and performance requirements are presented along with a further improved, optimized version of the algorithm together with its corresponding expected performance.

The CMS silicon strip tracker, providing a sensitive area of approximately 200 m2 and comprising 10 million readout channels, has recently been completed at the tracker integration facility at CERN. The strip tracker community is currently working to develop and integrate the online and offline software frameworks, known as XDAQ and CMSSW respectively, for the purposes of data acquisition and detector commissioning and monitoring. Recent developments have seen the integration of many new services and tools within the online data acquisition system, such as event building, online distributed analysis, an online monitoring framework, and data storage management. We review the various software components that comprise the strip tracker data acquisition system, the software architectures used for stand-alone and global data-taking modes. Our experiences in commissioning and operating one of the largest ever silicon micro-strip tracking systems are also reviewed.

The subsystems of the CMS silicon strip tracker were integrated and commissioned at the Tracker Integration Facility (TIF) in the period from November 2006 to July 2007. As part of the commissioning, large samples of cosmic ray data were recorded under various running conditions in the absence of a magnetic field. Cosmic rays detected by scintillation counters were used to trigger the readout of up to 15\,\% of the final silicon strip detector, and over 4.7~million events were recorded. This document describes the cosmic track reconstruction and presents results on the performance of track and hit reconstruction as from dedicated analyses.

Graphical Processing Units (GPUs) have evolved into highly parallel, multi-threaded, multicore powerful processors with high memory bandwidth. GPUs are used in a variety of intensive computing applications. The combination of highly parallel architecture and high memory bandwidth makes GPUs a potentially promising technology for e_ective real-time processing for High Energy Physics (HEP) experiments. However, not much is known of their performance in real-time applications that require low latency, such as the trigger for HEP experiments. We describe an R&D project with the goal to study the performance of GPU technology for possible low latency applications, performing basic operations as well as some more advanced HEP lower-level trigger algorithms (such as fast tracking or jet finding). We present some preliminary results on timing measurements, comparing the performance of a CPU versus a GPU with NVIDIA's CUDA general-purpose parallel computing architecture, carried out at CDF's Level-2 trigger test stand. These studies will provide performance benchmarks for future studies to investigate the potential and limitations of GPUs for real-time applications in HEP experiments.

Abstract Studying electron spin resonance in the relaxed excited state (RES) of F-centres via the optical pumping technique an additional signal is observed. There is considerable evidence that it is related to another relaxed state occupied in the optical cycle of the isolated F-centre. g -factors and linewidths are given for NaCl, KCl, KBr and CsBr, and the possible nature of the state is discussed.

The CDF data acquisition and trigger system is being upgraded to significantly increase the bandwidth for the upcoming high luminosity running of the Tevatron Collider (run IIb). This paper focuses on the upgrade for the level 2 (L2) trigger decision crate. This crate is at the heart of the L2 trigger system and has to interface with many different subsystems both upstream and downstream. The challenge of this upgrade is to have a uniform design to be able to interface with many different data paths upstream, merge and process the data at high speed for fast L2 trigger decision making, and minimize the impact on the running CDF experiment during the commissioning phase. In order to meet this challenge, the design philosophy of the upgrade is to use one type of general purpose motherboard, with a few powerful modern FPGAs and SRAMs, to interface any user data with any industrial standard link through the use of mezzanine cards. This general purpose motherboard, named "Pulsar" (PULSer And Recorder), is fully self-testable at board level as well as at system level. CERN S-LINK is chosen to allow Pulsar to communicate with commodity processors via high bandwidth, low latency S-LINK-to-PCI cards. Knowledge gained by using S-LINK at CDF will be transferable to and from the LHC community.

A fairly simple and effective method is described to detect spin resonances in the relaxed excited state (RES) of F-and similar color centres in alkali halides. It has been applied to F-centers in CsCl and CsBr, yielding g-factors of 1.77(4) and 1.54(4), respectively, for the RES.

During the latter months of 2006 and the first half of 2007, the CMS Tracker was assembled and operated at the Tracker Integration Facility at CERN. During this period the performance of the tracker at trigger rates up to 100 kHz was assessed, and a source of high occupancy events was uncovered, diagnosed, and mitigated.

Electron spin resonance in the relaxed excited state (RES) of F- and Fa-centres in alkali halides is observed via the change of the electronic groundstate polarization achieved under saturated optical pumping. ESR data on the RES have been measured systematically for a number of crystals. The data are interpreted in terms of a very extended wavefunction of the RES. Under appropriate conditions an additional signal is observed in the RES spectrum that seems to be related to a new state in the relaxed configuration of the F-centre. ESR data of this state are given and other experimental evidence for its existence is discussed.

Charge-dependent anisotropy Fourier coefficients ($v_n$) of particle azimuthal distributions are measured in pPb and PbPb collisions at $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 5.02 TeV with the CMS detector at the LHC. The normalized difference in the second-order anisotropy coefficients ($v_2$) between positively and negatively charged particles is found to depend linearly on the observed event charge asymmetry with comparable slopes for both pPb and PbPb collisions over a wide range of charged particle multiplicity. In PbPb, the third-order anisotropy coefficient, $v_3$, shows a similar linear dependence with the same slope as seen for $v_2$. The observed similarities between the $v_2$ slopes for pPb and PbPb, as well as the similar slopes for $v_2$ and $v_3$ in PbPb, are compatible with expectations based on local charge conservation in the decay of clusters or resonances, and constitute a challenge to the hypothesis that the observed charge asymmetry dependence of $v_2$ in heavy ion collisions arises from a chiral magnetic wave.

The CMS Silicon Strip Tracker at the LHC comprises a sensitive area of approximately 200 m2 and 10 million readout channels. Its data acquisition system is based around a custom analogue front-end chip. Both the control and the readout of the front-end electronics are performed by off-detector VME boards in the counting room, which digitise the raw event data and perform zero-suppression and formatting. The data acquisition system uses the CMS online software framework to configure, control and monitor the hardware components and steer the data acquisition. The first data analysis is performed online within the official CMS reconstruction framework, which provides many services, such as distributed analysis, access to geometry and conditions data, and a Data Quality Monitoring tool based on the online physics reconstruction.

During the latter months of 2006 and the first half of 2007, the CMS Tracker was assembled and operated at the Tracker Integration Facility in Building 186 at CERN. At this time, several dedicated studies were carried out to validate the performance of the tracker after assembly, testing general noise performance, looking at a specific problem showing up for part of the tracker [1], and also looking at the performance at high acquisition rates [2]. We report on the the results of these studies and their consequences for operation of the Tracker at the experiment. I. THE CMS SILICON STRIP TRACKER. With its 210 m of silicon, 5.4 m length, 2.4 m diameter and 9.6 million readout channels, the CMS strip tracker is clearly the largest and most complicated silicon detector ever built. It consists of 4 main parts: the endcaps (TEC), the inner barrel (TIB), the outer Barrel (TOB) and the inner disks (TID). All together 15148 modules are distributed amongst these 4 systems. Because of its size and complexity, the collaboration paid meticulous attention to quality control and testing all the way through construction. However, some effects could not be detected during the construction and the final assembly of the subdetectors and the first large-scale tests were needed to point them out. This paper discusses the investigations into the cause of these effects as well as the ramifications for operations at the LHC.