M. Konecki

The CMS experiment at the (LHC) includes a hybrid silicon pixel detector for the reconstruction of charged tracks and of the interaction vertices. The barrel region consists of n-in-n sensors with 100×150μm2 cell size processed on diffusion oxygenated float zone silicon. A biasing grid is implemented and pixel isolation is achieved with the moderated p-spray technique. An extensive test program was carried out on the H2 beam line of the CERN-SPS. In this paper we describe the sensor layout, the beam test setup and the results obtained with both irradiated and non-irradiated prototype devices. Measurements of charge collection, hit detection efficiency, Lorentz angle and spatial resolution are presented.

Charge collection measurements performed on heavily irradiated p-spray DOFZ pixel sensors with a grazing angle hadron beam provide a sensitive determination of the electric field within the detectors. The data are compared with a complete charge transport simulation of the sensor which includes free carrier trapping and charge induction effects. A linearly varying electric field based upon the standard picture of a constant type-inverted effective doping density is inconsistent with the data. A two-trap double junction model implemented in the ISE TCAD software can be tuned to produce a double peak electric field which describes the data reasonably well. The modeled field differs somewhat from previous determinations based upon the transient current technique. The model can also account for the level of charge trapping observed in the data.

The tracking system of the CMS experiment, currently under construction at the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland), will include a silicon pixel detector providing three spacial measurements in its final configuration for tracks produced in high-energy pp collisions. In this paper, we present the results of test beam measurements performed at CERN on irradiated silicon pixel sensors. Lorentz angle and charge collection efficiency were measured for two sensor designs and at various bias voltages.

We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5×1014 to 5.9×1014neq/cm2. The model correctly predicts the variation in the profiles as the temperature is changed from -10 to -25∘C. The measured charge collection profiles are inconsistent with the linearly varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon.

In this paper we discuss the measurement of charge collection in irradiated silicon pixel sensors and the comparison with a detailed simulation. The simulation implements a model of radiation damage by including two defect levels with opposite charge states and trapping of charge carriers. The modeling proves that a doubly peaked electric field generated by the two defect levels is necessary to describe the data and excludes a description based on acceptor defects uniformly distributed across the sensor bulk. In addition, the dependence of trap concentrations upon fluence is established by comparing the measured and simulated profiles at several fluences and bias voltages.

The barrel region of the CMS pixel detector will be equipped with “n-in-n” type silicon sensors. They are processed on diffusion oxygenated float zone (DOFZ) material, use the moderated p-spray technique for inter pixel isolation and feature a bias grid. The latter leads to a small fraction of the pixel area to be less sensitive to particles. In order to quantify this inefficiency prototype pixel sensors irradiated to particle fluences between 4.7×1013 and 2.6×1015neq/cm2 have been bump bonded to un-irradiated readout chips and tested using high energy pions at the H2 beam line of the CERN SPS. The readout chip allows a non-zero suppressed analog readout and is therefore well suited to measure the charge collection properties of the sensors. In this paper we discuss the fluence dependence of the collected signal and the particle detection efficiency. Further the position dependence of the efficiency is investigated.

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.

The general scheme for the fast, pipelined first level trigger on high pt muons in the CMS detector at LHC is presented. The prototype PACT system was tested in the high momentum muon beams in the RD5 experiment during 1993/94 runs. The obtained efficiency curves are shown.

This paper reports on the sensor R&D activity for the CMS pixel detector. Devices featuring several design and technology options have been irradiated up to a proton fluence of 1/spl times/10/sup 15/ n/sub eq//cm/sup 2/ at the CERN PS. Afterward, they were bump bonded to unirradiated readout chips and tested using high energy pions in the H2 beam line of the CERN SPS. The readout chip allows a nonzero suppressed full analogue readout and therefore a good characterization of the sensors in terms of noise and charge collection properties. The position dependence of signal is presented and the differences between the two sensor options are discussed.

During the summer 2006, a first integrated test of a part of the CMS experiment was performed at CERN collecting a data sample of several millions of cosmic rays events. A fraction of the Resistive Plate Chambers system was successfully operated. Results on the RPC performance are reported.

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.

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.

CMS is a general purpose detector that operates at the LHC. The PACT is a Level-1, RPC based muon sub-trigger of the CMS experiment. In this paper an overview of the CMS and its muon trigger is given. The principles of the PACT system are explained. The PACT performance during the LHC Run-1 is presented, including efficiency, stability and rate. The role of the PACT in the Level-1 muon trigger system is exposed. The perspectives for the RPC system in the context of CMS modifications are discussed.

The Pixel Detector is the innermost detector of the tracking system of the Compact Muon Solenoid (CMS) experiment. It provides the most precise measurements which contribute to the full track reconstruction. It also allows standalone track reconstruction, which is particularly useful for online event selection (called High-Level Triggering). The reconstruction algorithms using the Pixel Detector are presented, including pixel track reconstruction, primary vertex finding and seed generation.

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.

The experiments at the planned 14 TeV proton-proton collider LHC will need a good identification and measurement of muons with energies of up to about 800 GeV. The production of electromagnetic secondaries by muons of energy from 10 to 300 GeV has been measured at the RD5 experiment at CERN using various detector types proposed for LHC experiments. It is demonstrated that the detectors can recognize the presence of individual hits from em secondaries, and that the muon measurement would be seriously compromised if these hits are not suppressed.

A new method for the extraction of the electric field in the bulk of heavily irradiated silicon pixel sensors is presented. It is based on the measurement of the Lorentz deflection and mobility of electrons as a function of depth. The measurements were made at the CERN H2 beam line, with the beam at a shallow angle with respect to the pixel sensor surface. The extracted electric field is used to simulate the charge collection and the Lorentz deflection in the pixel sensor. The simulated charge collection and the Lorentz deflection is in good agreement with the measurements both for non-irradiated and irradiated up to 1E15 neq/cm2 sensors.

The CMS muon system is conceived for trigger and muon track reconstruction. The redundancy and robustness of the system are guaranteed by three complementary subsystems: drift tube in the barrel, cathode strip chamber in the end-cap and resistive plate chamber in barrel and end-cap. The installation of muon stations and read-out trigger electronic has been completed in middle 2007. Since than, a remarkable effort has been addressed to the detector commissioning in order to ensure the readiness of the hardware/software chain for the LHC start up operation. At the end of 2007, a test of an entire CMS slice has been performed, involving about 5% of muon stations. Several thousand cosmic muons events have been collected. Performance of the barrel chambers are reported.

In the CERN CMS experiment at LHC Collider special trigger signals called Technical Triggers will be used for the purpose of test and calibration. The Resistive Plate Chambers (RPC) based Technical Trigger system is a part of the CMS muon trigger system and is designed to detect cosmic muon tracks. It is based on two boards, namely RBC (RPC Balcony Collector) and TTU (Technical Trigger Unit). The proposed tracking algorithm (TA) written in VHDL and implemented in the TTU board detects single or multiple cosmic muon tracks at every bunch crossing along with their track lengths and corresponding chamber coordinates. The TA implementation in VHDL and its preliminary simulation results are presented.

During the LHC Run-1 (2010Run-1 ( -2013) ) the CMS experiment received almost 30 fb -1 of proton-proton data at the energies of √ s = 7 and 8 TeV.The accumulated statistics allow CMS to perform frontier measurements at high-energies.In this paper, the CMS detector and its performance are briefly described.The highlights of the CMS results are given.Selected Higgs physics results, measurements of vector boson, top-quark and jets production, B/B s → µµ and searches for new phenomena are described.The CMS upgrade plans are presented, including ongoing activities during present accelerator shut-down as well as modifications in the LHC Phase-I and beyond.

One of the key physics goals of the LHCb experiment at the LHC is the measurement of mixing induced CP violation in decays of B s → J/ψφ.The interference between mixing and decay gives rise to a CP-violating phase, φ J/ψφ s .Assuming a proper-time resolution and tagging performance as observed in simulated data, together with an expected luminosity of 1 fb -1 by the end of 2011, LHCb is expected to be able to measure φ J/ψφ s with an error of 0.07 rad.

The Resistive Plate Chambers [M. Abbrescia, et al., Nucl. Instr. and Meth. A 550 (2005) 116] are used in the CMS experiment [CMS Collaboration, The CMS experiment at the CERN LHC 2008, J. Inst. 3 (2008) S08004] as a dedicated muon trigger both in barrel and endcap system. About 4000m2 of double gap RPCs have been produced and have been installed in the experiment since more than one and half Years. The full barrel system and a fraction of the endcaps have been monitored to study dark current behaviour and system stability, and have been extensively commissioned with Cosmic Rays collected by the full CMS experiment.

In this paper we evaluate the potential of the CMS detector for the measurement of CP violation in the B system at the initial low luminosity of LHC (~10 33 cm −2 s −1 ). The sensitivity to the unitarity triangle angle β obtained from the [Formula: see text] channel is given by δ ( sin 2β) = 0.046, whilst the sensitivity to a from the [Formula: see text] channel is given by δ ( sin 2α) = 0.082. We also discuss the possibilities of observing semi-inclusive B → μ + D (s) final states, to measure [Formula: see text] oscillations and to observe some B baryon modes.

Charge collection measurements performed on heavily irradiated p-spray dofz pixel sensors with a grazing angle hadron beam provide a sensitive determination of the electric field within the detectors. The data are compared with a complete charge transport simulation of the sensor which includes signal trapping and charge induction effects. A linearly varying electric field based upon the standard picture of a constant type-inverted effective doping density is inconsistent with the data. A two-trap double junction model implemented in ISE TCAD software can be tuned to produce a doubly-peaked electric field which describes the data reasonably well at two different fluences. The modeled field differs somewhat from previous determinations based upon the transient current technique. The model can also account for the level of signal trapping observed in the data.

Triggering in the high‐rate environment of the LHC is a challenging task. The CMS experiment has developed a two‐stage trigger system. The Level‐1 Trigger is based on custom hardware devices and is designed to reduce the 40 MHz LHC bunch‐crossing rate to a maximum event rate of ∼ 100 kHz. The further reduction of the event rate to O(100 Hz), suitable for permanent storage, is performed in the High‐Level Trigger (HLT) which is based on a farm of commercial processors. The methods used for object identification and reconstruction are presented. The CMS event selection strategy is discussed. The performance of the HLT is also given.

The Muon System of the CMS experiment at CERN employees three different detector technologies—Drift Tube Chambers (DT) in the barrel part, Cathode Strip Chambers (CSC) in the endcaps and Resistive Plate Chambers (RPC) both in the barrel and the endcaps. TDs and CSCs serve as precise muon trajectory measurement devices. The RPCs are responsible for the bunch crossing identification and for a fast muon transverse momentum measurement. The total number of RPCs is 480 in the barrel and 756 in the endcaps, covering an area of about 3500 square meters. A brief overview of the system will be presented as well as some recent results about the system stability and performance.

An event reconstruction at LHC is a challenging task. The Compact Muon Solenoid (CMS) is a general purpose experiment with a precise and redundant Muon System. A good muon reconstruction and identification is one of its design goals. In CMS muons are initially identified by dedicated Level-1 muon trigger while the precise reconstruction is completed at the High-Level Trigger and offline. In this note the CMS Muon System is presented. The muon reconstruction algorithms both for event selection during triggering steps and offline, are described. The CMS experience with alignment of the Muon System using cosmic data are also given.

Triggering in the high-rate environment of LHC is a challenging task.The Compact Muon Solenoid (CMS) experiment has developed a two-stage trigger system.The Level-1 Trigger is based on custom hardware devices while the High-Level Trigger (HLT) is using a farm of commercial processors.One of the key aspects of HLT reconstruction is a fast and efficient track and vertex finding, in which CMS Pixel Detector, the innermost in the tracking system, is of primary importance.It provides precise measurements not only supporting the full track reconstruction, but also allowing the standalone reconstruction which is well suited for CMS online selection.The track and vertex reconstruction algorithms for HLT are presented with a focus on fast pixel track reconstruction, primary-vertex finding and seed generation.

The CMS detector will start its operation in the end of 2007. Until that time great care must be taken in order to assure that hardware operation is fully understood. In this paper an example of how emulation software helps achieving this goal in the CMS Level-1 RPC Trigger system is presented. The design of the RPC trigger allows to insert sets of so-called test pulses at any stage of the hardware pipeline. Reading out data from different stages is also possible. Such design allows for easy debugging of the trigger hardware by comparing hardware and software emulation values, since the software and hardware algorithms are identical.

Very high LHC luminosity will result in ∼ 1013 b-particles produced per year allowing general purpose detectors ATLAS and CMS to contribute to the exploration of phenomena in B physics. A review of simulation studies made by ATLAS and CMS B-physics groups is given. The expected numbers of reconstructed events, sensitivities to CP violating parameters, the xs measurements, and possibilities to observe very rare B-decays are discussed.

Abstract We discuss the potentials of the CMS detector for the study of b-physics and CP violation measurements during the initial low luminosity phase of the LHC. The sensitivity to the unitarity-triangle angle α obtained from the time-integrated B → ππ channel is expected to be δ(sin2α) = 0.082, whilst the sensitivity to the angle β obtained with the channel B → ( J ψ )K s 0 is given by δ(sin2β) = 0.046. We studied a number of control channels that will be needed to understand the measured asymmetries and which will allow us to monitor the B/ B production asymmetry, the dilution factors and the possible experimental biases. Possibilities of b-baryon physics have been investigated. The measurement of the B 0 s − B 0 s oscillation should be achievable for xs up to about 30 with the new baseline tracker complemented by a microvertex device. With our best knowledge of the background, the decay Bs0 → μμ could be visible after three years of running if BR(Bs0 → μμ) > 2.8 × 10−9.

This paper reports on a current R&D activity for the sensor part of the CMS pixel detector. Devices featuring several design and technology options have been irradiated up to a proton fluence of 1 /spl times/ 10/sup 15/ n/sup eq//cm/sup 2/ at the CERN PS. Afterwards they have been bump bonded to unirradiated readout chips. The chips allow a non zero suppressed full analogue readout and therefore a good characterization of the sensors in terms of noise and charge collection properties. The samples have been tested using high energy pions in the H2 beam line of the CERN SPS in June and September 2003. The results of this test beam are presented and the differences between the sensor options are discussed.

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.

The High Luminosity LHC (HL-LHC) is expected to commence operation in 2029 with an expected luminosity of 7.5×10 34 cm -2 s -1 .While this luminosity will bring a higher data rate beneficial to the search for interesting physics, it comes with the consequence of a pileup of ∼200.These harsher operating conditions will require the upgrade of the trigger system.The track reconstructing algorithms of the Level-1 Trigger for the three Muon Track Finder (MTF) regions (Barrel, Overlap, Endcap) will be developed in order to maintain and possibly improve the current event selection precision.Stand-alone candidates from the outer tracking system will also be taken into account in the decision of the Global Muon Trigger (GMT).The MTF and GMT will be implemented in a custom X2O board.

The momentum and angular distributions of punchthrough muons have been measured after a 10 λ calorimeter using an iron toroid magnet with 1.5 T as spectrometer. The calorimeter was inside a variable magnetic field of 0 to 3 T. The incident momentum of the π− beam ranged from 20 to 300 GeV/c. Measurements were also done at some beam momenta for π+, K+ and p. The results are compared with Monte Carlo predictions. A parameterization for the momentum spectrum of punchthrough muons was derived from the data.

The CMS experiment implements a sophisticated two-level triggering system composed of Level-1, instrumented by custom-design hardware boards, and a software High-Level Trigger.A new Level-1 trigger architecture with improved performance is now being used to maintain high physics efficiency for the more challenging luminosity conditions experienced during Run II.The CMS muon detector was designed for preserving the complementarity and partially redundant muon detection systems, Cathode Strip Chambers (CSC), Drift Tubes (DT) and Resistive Plate Chambers (RPC), until they were combined at the input to the Global Trigger.The upgraded muon trigger combines information from the three muon detectors in the track reconstruction in order to obtain a better efficiency and lower rates.Advanced pattern recognition and MVA (Boosted Decision Tree) regression techniques implemented directly on the trigger boards allow high-momentum signal muons to be distinguished from the overwhelming low-momentum background.The algorithms for the selection of events with muons, both for precision measurements and for searches of new physics beyond the Standard Model, will be described in detail.The performance of the upgraded muon trigger system is evaluated, based on proton-proton collision data collected in Run II.

We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5×10 14 neq/cm 2 to 5.9×10 14 neq/cm 2 . The model correctly predicts the variation in the profiles as the temperature is changed from 10 ◦ C to 25 ◦ C. The measured charge collection profiles are inconsistent with the linearly-varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon. The model is now being used to calibrate pixel hit reconstruction algorithms for CMS.

Charge collection measurements performed on heavily irradiated p-spray dofz pixel sensors with a grazing angle hadron beam provide a sensitive determination of the electric field within the detectors. The data are compared with a complete charge transport simulation of the sensor which includes signal trapping and charge induction effects. A linearly varying electric field based upon the standard picture of a constant type-inverted effective doping density is inconsistent with the data. A two-trap double junction model implemented in ISE TCAD software can be tuned to produce a doubly-peaked electric field which describes the data reasonably well at two different fluences. The modeled field differs somewhat from previous determinations based upon the transient current technique. The model can also account for the level of signal trapping observed in the data.

We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5x10^{14} Neq/cm^2 to 5.9x10^{14} Neq/cm^2. The model correctly predicts the variation in the profiles as the temperature is changed from -10C to -25C. The measured charge collection profiles are inconsistent with the linearly-varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon. The model is now being used to calibrate pixel hit reconstruction algorithms for CMS.

A new method for the extraction of the electric field in the bulk of heavily irradiated silicon pixel sensors is presented. It is based on the measurement of the Lorentz deflection and mobility of electrons as a function of depth. The measurements were made at the CERN H2 beam line, with the beam at a shallow angle with respect to the pixel sensor surface. The extracted electric field is used to simulate the charge collection and the Lorentz deflection in the pixel sensor. The simulated charge collection and the Lorentz deflection is in good agreement with the measurements both for non-irradiated and irradiated up to 1E15 neq/cm2 sensors.

The total punchthrough probability of showers produced by negative pions, positive pions, positive kaons and protons, has been measured as a function of depth in an absorber in a magnetic field ranging from 0 to 3 Tesla. The incident particle momentum varied from 10 to 300 GeV/c. The lateral shower development and particle multiplicity at several absorber depths have been determined. The measurements are compared with the predictions of Monte Carlo simulation programs.