Tapio Lampén

Geant4 is a toolkit for simulating the passage of particles through matter. It includes a complete range of functionality including tracking, geometry, physics models and hits. The physics processes offered cover a comprehensive range, including electromagnetic, hadronic and optical processes, a large set of long-lived particles, materials and elements, over a wide energy range starting, in some cases, from 250eV and extending in others to the TeV energy range. It has been designed and constructed to expose the physics models utilised, to handle complex geometries, and to enable its easy adaptation for optimal use in different sets of applications. The toolkit is the result of a worldwide collaboration of physicists and software engineers. It has been created exploiting software engineering and object-oriented technology and implemented in the C++ programming language. It has been used in applications in particle physics, nuclear physics, accelerator design, space engineering and medical physics.

The CMS detector at the CERN LHC features a silicon pixel detector as its innermost subdetector. The original CMS pixel detector has been replaced with an upgraded pixel system (CMS Phase-1 pixel detector) in the extended year-end technical stop of the LHC in 2016/2017. The upgraded CMS pixel detector is designed to cope with the higher instantaneous luminosities that have been achieved by the LHC after the upgrades to the accelerator during the first long shutdown in 2013–2014. Compared to the original pixel detector, the upgraded detector has a better tracking performance and lower mass with four barrel layers and three endcap disks on each side to provide hit coverage up to an absolute value of pseudorapidity of 2.5. This paper describes the design and construction of the CMS Phase-1 pixel detector as well as its performance from commissioning to early operation in collision data-taking.

The upgrade of the LHC to the High-Luminosity LHC (HL-LHC) is expected to increase the LHC design luminosity by an order of magnitude. This will require silicon tracking detectors with a significantly higher radiation hardness. The CMS Tracker Collaboration has conducted an irradiation and measurement campaign to identify suitable silicon sensor materials and strip designs for the future outer tracker at the CMS experiment. Based on these results, the collaboration has chosen to use n-in-p type silicon sensors and focus further investigations on the optimization of that sensor type. This paper describes the main measurement results and conclusions that motivated this decision.

This document summarises the talks and discussions happened during the VBSCan Split17 workshop, the first general meeting of the VBSCan COST Action network. This collaboration is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.

A beam telescope based on the CMS Tracker data acquisition prototype cards has been developed in order to test sensor candidates for S-LHC tracking systems. The telescope consists of up to eight reference silicon microstrip modules and slots for a couple of test modules. Beam tracks, as measured by the reference modules, provide a means of determining the position resolution and efficiency of the test modules. The impact point precision of reference tracks at the location of the test modules is about 4μm. This note presents a detailed description of the silicon beam telescope (SiBT) along with some results from its initial operation in summer 2007 in the CERN H2 beamline.

The Silicon Beam Telescope (SiBT07) at the CERN H2 beam is a position-sensitive beam telescope targeted for LHC upgrade tests. The telescope consists of eight consecutive silicon microstrip detectors and slots for two test detectors. This article describes the reconstruction of reference tracks with the CMS data analysis software CMSSW. The related data analysis and calibration procedures, including pedestal corrections, common-mode corrections, and track-based alignment, are also described.

The degradation of signal in silicon sensors is studied under conditions expected at the CERN High-Luminosity LHC. 200 μm thick n-type silicon sensors are irradiated with protons of different energies to fluences of up to 3 · 1015 neq/cm2. Pulsed red laser light with a wavelength of 672 nm is used to generate electron-hole pairs in the sensors. The induced signals are used to determine the charge collection efficiencies separately for electrons and holes drifting through the sensor. The effective trapping rates are extracted by comparing the results to simulation. The electric field is simulated using Synopsys device simulation assuming two effective defects. The generation and drift of charge carriers are simulated in an independent simulation based on PixelAV. The effective trapping rates are determined from the measured charge collection efficiencies and the simulated and measured time-resolved current pulses are compared. The effective trapping rates determined for both electrons and holes are about 50% smaller than those obtained using standard extrapolations of studies at low fluences and suggest an improved tracker performance over initial expectations.

Abstract The CMS Inner Tracker, made of silicon pixel modules, will be entirely replaced prior to the start of the High Luminosity LHC period. One of the crucial components of the new Inner Tracker system is the readout chip, being developed by the RD53 Collaboration, and in particular its analogue front-end, which receives the signal from the sensor and digitizes it. Three different analogue front-ends (Synchronous, Linear, and Differential) were designed and implemented in the RD53A demonstrator chip. A dedicated evaluation program was carried out to select the most suitable design to build a radiation tolerant pixel detector able to sustain high particle rates with high efficiency and a small fraction of spurious pixel hits. The test results showed that all three analogue front-ends presented strong points, but also limitations. The Differential front-end demonstrated very low noise, but the threshold tuning became problematic after irradiation. Moreover, a saturation in the preamplifier feedback loop affected the return of the signal to baseline and thus increased the dead time. The Synchronous front-end showed very good timing performance, but also higher noise. For the Linear front-end all of the parameters were within specification, although this design had the largest time walk. This limitation was addressed and mitigated in an improved design. The analysis of the advantages and disadvantages of the three front-ends in the context of the CMS Inner Tracker operation requirements led to the selection of the improved design Linear front-end for integration in the final CMS readout chip.

During summer 2006 a fraction of the CMS silicon strip tracker was operated in a comprehensive slice test called the Magnet Test and Cosmic Challenge (MTCC). At the MTCC, cosmic rays detected in the muon chambers were used to trigger the readout of all CMS sub-detectors in the general data acquisition system and in the presence of the 4 T magnetic field produced by the CMS superconducting solenoid. This document describes the operation of the Tracker hardware and software prior, during and after data taking. The performance of the detector as resulting from the MTCC data analysis is also presented.

A new CMS tracker detector will be installed for operation at the High Luminosity LHC (HL-LHC). This detector comprises modules with two closely spaced parallel sensor plates and front-end ASICs capable of transmitting tracking information to the CMS Level-1 (L1) trigger at the 40 MHz beam crossing rate. The inclusion of tracking information in the L1 trigger decision will be essential for selecting events of interest efficiently at the HL-LHC. The CMS Binary Chip (CBC) has been designed to read out and correlate hits from pairs of tracker sensors, forming so-called track stubs. For the first time, a prototype irradiated module and a full-sized module, both equipped with the version 2 of the CBC, have been operated in test beam facilities. The efficiency of the stub finding logic of the modules for various angles of incidence has been studied. The ability of the modules to reject tracks with transverse momentum less than 2 GeV has been demonstrated. For modules built with irradiated sensors, no significant drop in the stub finding performance has been observed. Results from the beam tests are described in this paper.

To cope with the challenging environment of the planned high luminosity upgrade of the Large Hadron Collider (HL-LHC), scheduled to start operation in 2029, CMS will replace its entire tracking system. The requirements for the tracker are largely determined by the long operation time of 10 years with an instantaneous peak luminosity of up to 7.5 × 1034 cm−2 s−1 in the ultimate performance scenario. Depending on the radial distance from the interaction point, the silicon sensors will receive a particle fluence corresponding to a non-ionising energy loss of up to Φeq= 3.5 × 1016 cm−2. This paper focuses on planar pixel sensor design and qualification up to a fluence of Φeq = 1.4 × 1016 cm−2.For the development of appropriate planar pixel sensors an R&D program was initiated, which includes n+-p sensors on 150 mm (6”) wafers with an active thickness of 150 µm with pixel sizes of 100×25 µm2 and 50×50 µm2 manufactured by Hamamatsu Photonics K.K. (HPK). Single chip modules with ROC4Sens and RD53A readout chips were made. Irradiation with protons and neutrons, as well was an extensive test beam campaign at DESY were carried out. This paper presents the investigation of various assemblies mainly with ROC4Sens readout chips. It demonstrates that multiple designs fulfil the requirements in terms of breakdown voltage, leakage current and efficiency. The single point resolution for 50×50 µm2 pixels is measured as 4.0 µm for non-irradiated samples, and 6.3 µm after irradiation to Φeq = 7.2 × 1015 cm−2.

Abstract The Large Hadron Collider at CERN will undergo an upgrade in order to increase its luminosity to 7.5 × 10 34 cm -2 s -1 . The increased luminosity during this High-Luminosity running phase, starting around 2029, means a higher rate of proton-proton interactions, hence a larger ionizing dose and particle fluence for the detectors. The current tracking system of the CMS experiment will be fully replaced in order to cope with the new operating conditions. Prototype planar pixel sensors for the CMS Inner Tracker with square 50 μm × 50 μm and rectangular 100 μm × 25 μm pixels read out by the RD53A chip were characterized in the lab and at the DESY-II testbeam facility in order to identify designs that meet the requirements of CMS during the High-Luminosity running phase. A spatial resolution of approximately 3.4 μm (2 μm) is obtained using the modules with 50 μm × 50 μm (100 μm × 25 μm) pixels at the optimal angle of incidence before irradiation. After irradiation to a 1 MeV neutron equivalent fluence of Φ eq = 5.3 × 10 15 cm -2 , a resolution of 9.4 μm is achieved at a bias voltage of 800 V using a module with 50 μm × 50 μm pixel size. All modules retain a hit efficiency in excess of 99% after irradiation to fluences up to 2.1 × 10 16 cm -2 . Further studies of the electrical properties of the modules, especially crosstalk, are also presented in this paper.

Strip detectors with an area of 16cm2 were processed on high resistivity n-type magnetic Czochralski silicon. In addition, detectors were processed on high resistivity Float Zone wafers with the same mask set for comparison. The detectors were irradiated to several different fluences up to the fluence of 3×10151MeVneq/cm2 with protons or with mixed protons and neutrons. The detectors were fully characterized with CV- and IV-measurements prior to and after the irradiation. The beam test was carried out at the CERN H2 beam line using a silicon beam telescope that determines the tracks of the incoming particles and hence provides a reference measurement for the detector characterization. The n-type MCz-Si strip detectors have an acceptable S/N at least up to the fluence of 1×1015neq/cm2 and thus, they are a feasible option for the strip detector layers in the SLHC tracking systems.

Pad and strip detectors processed on high resistivity n-type magnetic Czochralski silicon (MCz-Si) were irradiated to several different fluences with protons.The pad detectors were characterized with the Transient Current Technique (TCT) and the full-size strip detectors with a reference beam telescope and a 225 GeV muon beam.The TCT measurements indicate a double junction structure and space charge sign inversion in MCz-Si detectors after 6 × 10 14 1 MeV n eq /cm 2 fluence.In the beam test a S/N of 50 was measured for a non-irradiated MCz-Si sensor, and a S/N of 20 for the sensors irradiated to the fluences of 1 × 10 14 1 MeV n eq /cm 2 , and 5 × 10 14 1 MeV n eq /cm 2 .

With an expected 10-fold increase in luminosity in S-LHC, the radiation environment in the tracker volumes will be considerably harsher for silicon-based detectors than the already harsh LHC environment. Since 2006, a group of CMS institutes, using a modified CMS DAQ system, has been exploring the use of Magnetic Czochralski silicon as a detector element for the strip tracker layers in S-LHC experiments. Both p+/n-/n+ and n+/p-/p+ sensors have been characterized, irradiated with proton and neutron sources, assembled into modules, and tested in a CERN beamline. There have been three beam studies to date and results from these suggest that both p+/n-/n+ and n+/p-/p+ Magnetic Czochralski silicon are sufficiently radiation hard for the R>25cm regions of S-LHC tracker volumes. The group has also explored the use of forward biasing for heavily irradiated detectors, and although this mode requires sensor temperatures less than −50 °C, the charge collection efficiency appears to be promising.

In March 2007 the assembly of the Silicon Strip Tracker was completed at the Tracker Integration Facility at CERN. Nearly 15% of the detector was instrumented using cables, fiber optics, power supplies, and electronics intended for the operation at the LHC. A local chiller was used to circulate the coolant for low temperature operation. In order to understand the efficiency and alignment of the strip tracker modules, a cosmic ray trigger was implemented. From March through July 4.5 million triggers were recorded. This period, referred to as the Sector Test, provided practical experience with the operation of the Tracker, especially safety, data acquisition, power, and cooling systems. This paper describes the performance of the strip system during the Sector Test, which consisted of five distinct periods defined by the coolant temperature. Significant emphasis is placed on comparisons between the data and results from Monte Carlo studies.

The results of the CMS tracker alignment analysis are presented using the data from cosmic tracks, optical survey information, and the laser alignment system at the Tracker Integration Facility at CERN. During several months of operation in the spring and summer of 2007, about five million cosmic track events were collected with a partially active CMS Tracker. This allowed us to perform first alignment of the active silicon modules with the cosmic tracks using three different statistical approaches; validate the survey and laser alignment system performance; and test the stability of Tracker structures under various stresses and temperatures ranging from +15 °C to −15 °C. Comparison with simulation shows that the achieved alignment precision in the barrel part of the tracker leads to residual distributions similar to those obtained with a random misalignment of 50 (80) μm RMS in the outer (inner) part of the barrel.

A heavily irradiated (3×1015 1 MeV neq/cm2) Current Injected Detector (CID) was tested with 225 GeV muon beam at CERN H2 beam line. In the CID concept the current is limited by the space charge. The injected carriers will be trapped by the deep levels and this induces a stable electric field through the entire bulk regardless of the irradiation fluence the detector has been exposed to. The steady-state density of the trapped charge is defined by the balance between the trapping and the emission rates of charge carriers (detrapping). Thus, the amount of charge injection needed for the electric field stabilization depends on the temperature. AC-coupled 16 cm2 detector was processed on high resistivity n-type magnetic Czochralski silicon, and it had 768 strips, 50 μm pitch, 10 μm strip width and 3.9 cm strip length. The beam test was carried out using a silicon beam telescope that is based on the CMS detector readout prototype components, APV25 readout chips, and eight strip sensors made by Hamamatsu having 60 μm pitch and intermediate strips. The tested CID detector was bonded to the APV25 readout, and it was operated at temperatures ranging from −40 to −53 °C. The CID detector irradiated at 3×1015 1 MeV neq/cm2 fluence shows about 40% relative Charge Collection Efficiency with respect to the non-irradiated reference plane sensors.

A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase~I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. In this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency is $99.95\pm0.05\,\%$, while the intrinsic spatial resolutions are $4.80\pm0.25\,\mu \mathrm{m}$ and $7.99\pm0.21\,\mu \mathrm{m}$ along the $100\,\mu \mathrm{m}$ and $150\,\mu \mathrm{m}$ pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.

During the high-luminosity phase of the LHC (HL-LHC), planned to start in 2027, the accelerator is expected to deliver an instantaneous peak luminosity of up to 7.5×1034 cm−2 s−1. A total integrated luminosity of 0300 or even 0400 fb−1 is foreseen to be delivered to the general purpose detectors ATLAS and CMS over a decade, thereby increasing the discovery potential of the LHC experiments significantly. The CMS detector will undergo a major upgrade for the HL-LHC, with entirely new tracking detectors consisting of an Outer Tracker and Inner Tracker. However, the new tracking system will be exposed to a significantly higher radiation than the current tracker, requiring new radiation-hard sensors. CMS initiated an extensive irradiation and measurement campaign starting in 2009 to systematically compare the properties of different silicon materials and design choices for the Outer Tracker sensors. Several test structures and sensors were designed and implemented on 18 different combinations of wafer materials, thicknesses, and production technologies. The devices were electrically characterized before and after irradiation with neutrons, and with protons of different energies, with fluences corresponding to those expected at different radii of the CMS Outer Tracker after 0300 fb−1. The tests performed include studies with β sources, lasers, and beam scans. This paper compares the performance of different options for the HL-LHC silicon sensors with a focus on silicon bulk material and thickness.

The formation of clusters in the data analysis of position-sensitive detectors is traditionally based on signal-to-noise ratio thresholds. For detectors with a very low signal-to-noise ratio, e.g., as a result of radiation damage, the total collected charge obtained from the clusters is biased to the greater signal values resulting from the thresholds. In this paper an unbiased method to measure the charge collection of a silicon strip detector in a test beam environment is presented. The method is based on constructing the clusters on test detectors around the impact point of the reference track.

Inelastic nuclear collisions of hadrons incident on silicon sensors can generate secondary highly ionising particles (HIPs) and deposit as much energy within the sensor bulk as several hundred minimum ionising particles. The large signals generated by these ‘HIP events’ can momentarily saturate the APV25 front-end readout chip for the silicon strip tracker (SST) sub-detector of the compact muon solenoid (CMS) experiment, resulting in deadtime in the detector readout system. This paper presents studies of this phenomenon through simulation, laboratory measurements and dedicated beam tests. A proposed change to a front-end component to reduce the APV25 sensitivity to HIP events is also examined. The results are used to infer the expected effect on the performance of the CMS SST at the future large hadron collider. The induced inefficiencies are at the percent level and will have a negligible effect on the physics performance of the SST.

We test the usage of a Toolkit for Multivariate Data Analysis (TMVA) in b tagging. Tagging b jets associated with heavy neutral MSSM Higgs bosons at the LHC can be used to extract the Higgs bosons from the Drell-Yan background, for which the associated jets are mainly light quark and gluon jets. Achievable b tagging efficiency is studied with more than ten MVA classifiers at 1% mistagging rate. Most classifiers were found to perform better than the simple track counting algorithm.

The high luminosity upgrade of the Large Hadron Collider, foreseen for 2026, necessitates the replacement of the CMS experiment’s silicon tracker. The innermost layer of the new pixel detector will be exposed to severe radiation, corresponding to a 1 MeV neutron equivalent fluence of up to $$\Phi _{eq} = 2 \times 10^{16}$$ cm $$^{-2}$$ , and an ionising dose of $${\approx } 5$$ MGy after an integrated luminosity of 3000 fb $$^{-1}$$ . Thin, planar silicon sensors are good candidates for this application, since the degradation of the signal produced by traversing particles is less severe than for thicker devices. In this paper, the results obtained from the characterisation of 100 and 200 $$\upmu $$ m thick p-bulk pad diodes and strip sensors irradiated up to fluences of $$\Phi _{eq} = 1.3 \times 10^{16}$$ cm $$^{-2}$$ are shown.

A new CMS Tracker is under development for operation at the High Luminosity LHC from 2026 onwards. It includes an outer tracker based on dedicated modules that will reconstruct short track segments, called stubs, using spatially coincident clusters in two closely spaced silicon sensor layers. These modules allow the rejection of low transverse momentum track hits and reduce the data volume before transmission to the first level trigger. The inclusion of tracking information in the trigger decision is essential to limit the first level trigger accept rate. A customized front-end readout chip, the CMS Binary Chip (CBC), containing stub finding logic has been designed for this purpose. A prototype module, equipped with the CBC chip, has been constructed and operated for the first time in a 4 GeV/c positron beam at DESY. The behaviour of the stub finding was studied for different angles of beam incidence on a module, which allows an estimate of the sensitivity to transverse momentum within the future CMS detector. A sharp transverse momentum threshold around 2 GeV/c was demonstrated, which meets the requirement to reject a large fraction of low momentum tracks present in the LHC environment on-detector. This is the first realistic demonstration of a silicon tracking module that is able to select data, based on the particle's transverse momentum, for use in a first level trigger at the LHC . The results from this test are described here.

CERN RD39 Collaboration develops radiation-hard cryogenic silicon detectors. Recently, we have demonstrated improved radiation hardness in novel Current Injected Detectors (CID). For detector characterization, we have applied cryogenic Transient Current Technique (C-TCT). In beam tests, heavily irradiated CID detector showed capability for particle detection. Our results show that the CID detectors are operational at the temperature -50degC after the fluence of 1 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> 1 MeV neutron equivalent/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

In 2017 a new pixel detector was installed in the CMS detector. This so-called Phase-1 pixel detector features four barrel layers in the central region and three disks per end in the forward regions. The upgraded pixel detector requires an upgraded data acquisition (DAQ) system to accept a new data format and larger event sizes. A new DAQ and control system has been developed based on a combination of custom and commercial microTCA parts. Custom mezzanine cards on standard carrier cards provide a front-end driver for readout, and two types of front-end controller for configuration and the distribution of clock and trigger signals. Before the installation of the detector the DAQ system underwent a series of integration tests, including readout of the pilot pixel detector, which was constructed with prototype Phase-1 electronics and operated in CMS from 2015 to 2016, quality assurance of the CMS Phase-1 detector during its assembly, and testing with the CMS Central DAQ. This paper describes the Phase-1 pixel DAQ and control system, along with the integration tests and results. A description of the operational experience and performance in data taking is included.

Abstract During the operation of the CMS experiment at the High-Luminosity LHC the silicon sensors of the Phase-2 Outer Tracker will be exposed to radiation levels that could potentially deteriorate their performance. Previous studies had determined that planar float zone silicon with n-doped strips on a p-doped substrate was preferred over p-doped strips on an n-doped substrate. The last step in evaluating the optimal design for the mass production of about 200 m 2 of silicon sensors was to compare sensors of baseline thickness (about 300 μm) to thinned sensors (about 240 μm), which promised several benefits at high radiation levels because of the higher electric fields at the same bias voltage. This study provides a direct comparison of these two thicknesses in terms of sensor characteristics as well as charge collection and hit efficiency for fluences up to 1.5 × 10 15 n eq /cm 2 . The measurement results demonstrate that sensors with about 300 μm thickness will ensure excellent tracking performance even at the highest considered fluence levels expected for the Phase-2 Outer Tracker.

Good geometrical calibration is essential in the use of high resolution detectors. The individual sensors in the detector have to be calibrated with an accuracy better than the intrinsic resolution, which typically is of the order of 10 um. We present an effective method to perform fine calibration of sensor positions in a detector assembly consisting of a large number of pixel and strip sensors. Up to six geometric parameters, three for location and three for orientation, can be computed for each sensor on a basis of particle trajectories traversing the detector system. The performance of the method is demonstrated with both simulated tracks and tracks reconstructed from experimental data. We also present a brief review of other alignment methods reported in the literature.

We report on test beam results obtained with a 32.5 cm2 microstrip detector processed on an n-type 380 μm thick magnetic Czochralski (MCZ) grown silicon substrate with 1200 Ωcm effective resistivity. The full depletion voltage of the as-processed detector was 420 V with a leakage current of 2 μA. The AC coupled detector had 1024 p+ strips, 10 μm by width and 6.154 cm by length with a pitch of 50 μm. The detector was irradiated with 10 MeV protons to 1.6×1014 1 MeV neutron equivalent fluence and annealed for 345 days at room temperature. The post-irradiation full depletion voltage of the detector was 225 V. The leakage current at the full depletion measured at −10 °C was 261 μA. The beam tests were carried out at the CERN H2 area using a Silicon Beam Telescope, which consists of pairs of horizontal and vertical position sensitive silicon detectors. This telescope determines the tracks of incoming particles and hence provides a reference measurement for the detector characterization. In the beam test an average signal to noise ratio of 3 with a spatial resolution of 20 μm and a particle detection efficiency of 36% were measured. These results show that the MCZ device detected particles, which encourages further investigations of MCZ silicon as a detector material. The poor performance of the MCZ detector may be explained by the problems observed in the reference telescope.

We present rst results of a track based alignment procedure applied to test beam data recorded with Cosmic Rack, a test setup which mimicks the outer barrel of the CMS Tracker. The Hits and Impact Points alignment method is used within the CMS reconstruction software framework to align this telescope-like device. These results were compared to results obtained with manual alignment and to results obtained with the Millepede algorithm. This study demonstrates that the software implementation of the recently developed alignment tools works properly and also represents the rst track based alignment results in CMS using real data.

Implementation of the CMS policy on long-term data preservation, re-use and open access has started.Current practices in providing data additional to published papers and distributing simplified data-samples for outreach are promoted and consolidated.The first measures have been taken for analysis and data preservation for the internal use of the collaboration and for open access to part of the data.Two complementary approaches are followed.First, a virtual machine environment, which will pack all ingredients needed to compile and run a software release with which the legacy data was reconstructed.Second, a validation framework, maintaining the capability not only to read the old raw data, but also to reprocess them with an updated release or to another format to help ensure long-term reusability of the legacy data.

Abstract The Large Hadron Collider (LHC) at CERN will undergo major upgrades to increase the instantaneous luminosity up to 5–7.5×10 34 cm -2 s -1 . This High Luminosity upgrade of the LHC (HL-LHC) will deliver a total of 3000–4000 fb -1 of proton-proton collisions at a center-of-mass energy of 13–14 TeV. To cope with these challenging environmental conditions, the strip tracker of the CMS experiment will be upgraded using modules with two closely-spaced silicon sensors to provide information to include tracking in the Level-1 trigger selection. This paper describes the performance, in a test beam experiment, of the first prototype module based on the final version of the CMS Binary Chip front-end ASIC before and after the module was irradiated with neutrons. Results demonstrate that the prototype module satisfies the requirements, providing efficient tracking information, after being irradiated with a total fluence comparable to the one expected through the lifetime of the experiment.

An iterative algorithm for track based alignment is presented. The algorithm can be applied to rigid composite detector structures or to individual modules. The iterative process involves track reconstruction and alignment, in which the chi <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> function of the hit residuals of each alignable object is minimized. Six alignment parameters per structure or per module, three for location and three for orientation, can be computed. The method is computationally light and easily parallelizable. The performance of the method is demonstrated with simulated tracks in the CMS pixel detector and tracks reconstructed from experimental data recorded with a test beam setup

Abstract The Short Strip ASIC (SSA) is one of the four front-end chips designed for the upgrade of the CMS Outer Tracker for the High Luminosity LHC. Together with the Macro-Pixel ASIC (MPA) it will instrument modules containing a strip and a macro-pixel sensor stacked on top of each other. The SSA provides both full readout of the strip hit information when triggered, and, together with the MPA, correlated clusters called stubs from the two sensors for use by the CMS Level-1 (L1) trigger system. Results from the first prototype module consisting of a sensor and two SSA chips are presented. The prototype module has been characterized at the Fermilab Test Beam Facility using a 120 GeV proton beam.

We present a cosmic rack, the FinnCRack. This device is a silicon strip detector-based telescope that measures tracks of cosmic particles. The FinnCRack is constructed using components of the Tracker Outer Barrel (TOB) of the CMS experiment at the CERN LHC. The device is part of the TOB integration and verification effort together with its sister telescope, the CERN CRack. Both CRacks mimick a six degree slice of the TOB barrel structure. The FinnCRack is intended to (a) serve as a platform for TOB software development, both analysis and online software such as run control; (b) be used for noise and cluster shape studies; (c) act as a reference tracker in detector studies; and (d) provide a testbed for track-based alignment testing and development. The construction and setup of the FinnCRack have been documented in detail—the entire chain from connecting cables to physics data analysis—and the operation guide was tested in practice. Both these actions serve the purpose of training and attracting future HEP students. We also showed that we were able to measure cosmic muon tracks.

The silicon strip tracker of CMS is by far the biggest detector of its kind ever operated. Its 15 000 detector modules and 9 million readout channels are individually calibrated in order to achieve the optimal data quality for the experiment. Software tools were designed to automate the operations and reduce the need for maintenance as much as possible, taking care to use pre-existing software frameworks, when possible. The calibration software implements a dedicated scheme of event building, on-line distributed analysis, storage management, data analysis and configuration archival. Dedicated user interfaces and web-applications were developed to ease the operations, speed-up the calibration process, monitor its quality, and track the problems. A complete set of monitoring analyses are also performed online during data taking to validate the data acquired. The calibration parameters are measured continuously, and the values are fed back to the calibration database in order to refine the on-line event reconstruction. A review of the software tools and calibration processes is given here and the obtained results are discussed.

The complex system of the CMS all-silicon tracker, with 15148 silicon strip and 1440 silicon pixel modules, requires sophisticated alignment procedures. In order to achieve an optimal track-parameter resolution, the position and orientation of its modules need to be determined with a precision of few micrometers. Several developments of computing and data analysis have been carried out for reaching these performances. Novel tracking tools have been implemented in the alignment algorithms. Special work flows are used for a balanced statistical treatment of the data in order to fully exploit the wide range of physics candles at the LHC that can be exploited by the alignment. We present results of the alignment of the full tracker, in its final position, used for the reconstruction of the first collisions recorded by the CMS experiment. Validation tools are used for checking the quality of the final geometries: the quantities monitored span from the basic track quantities to physics resonances. The geometry has been systematically monitored in the different periods of operation of the CMS detector.

The complex system of the CMS all-silicon tracker, with 15148 silicon strip and 1440 silicon pixel modules, requires sophisticated alignment procedures. In order to achieve an optimal track-parameter resolution, the position and orientation of its modules need to be determined with a precision of few micrometers. Several developments of computing and data analysis have been carried out for reaching these performances. Novel tracking tools have been implemented in the alignment algorithms. Special work flows are used for a balanced statistical treatment of the data in order to fully exploit the wide range of physics candles at the LHC that can be exploited by the alignment.

This thesis presents studies related to track-based alignment for the future CMS experiment at CERN. Excellent geometric alignment is crucial to fully benefit from the outstanding resolution of individual sensors. The large number of sensors makes it difficult in CMS to utilize computationally demanding alignment algorithms. A computationally light alignment algorithm, called the Hits and Impact Points algorithm (HIP), is developed and studied. It is based on minimization of the hit residuals. It can be applied to individual sensors or to composite objects. All six alignment parameters (three translations and three rotations), or their subgroup can be considered. The algorithm is expected to be particularly suitable for the alignment of the innermost part of CMS, the pixel detector, during its early operation, but can be easily utilized to align other parts of CMS also. The HIP algorithm is applied to simulated CMS data and real data measured with a test-beam setup. The simulation studies demonstrate that the algorithm is a promising candidate for the alignment of the pixel detector. The test-beam study shows that the use of the algorithm significantly improves the data measured with genuine CMS hardware. The positioning uncertainties of different parts of CMS have also been systematically estimated. Ready-made scenarios corresponding to these uncertainties have been implemented in the CMS reconstruction software ORCA. These scenarios have been used in the alignment studies. They have also been widely used for more realistic misalignment simulation in the physics performance studies of the CMS collaboration.

Efficient and accurate track reconstruction requires proper alignment of the tracking devices used. Here, we describe the general alignment strategy envisaged for the CMS experiment. The hardware alignment devices of the CMS are presented as well as the different track-based alignment approaches.

The experience on using ROOT package TMVA for multivariate data analysis is reported for a problem of τ tagging in the framework of heavy charged MSSM Higgs boson searches at the LHC. We investigate with a generator level analysis how the τ tagging could be performed in an ideal case, and hadronic τ decays separated from the hadronic jets of QCD multi-jet background present in LHC experiments. A successful separation of the Higgs signal from the background requires a rejection factor of 105 or better against the QCD background. The τ tagging efficiency and background rejection are studied with various MVA classifiers.

CERN RD39 Collaboration develops radiation-hard cryogenic silicon detectors. Recently, we have demonstrated improved radiation hardness in novel Current Injected Detectors (CID). For detector characterization, we have applied cryogenic Transient Current Technique (C-TCT). In beam tests, heavily irradiated CID detector showed capability for particle detection. Our results show that the CID detectors are operational at the temperature -50°C after 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> 1 MeV neutron equivalent fluence.

This document summarises the talks and discussions happened during the VBSCan Split17 workshop, the first general meeting of the VBSCan COST Action network. This collaboration is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.