CERN Accelerating science

Posters

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2015-07-29
17:17
Radiation levels at CERN's injectors and their impact on electronic equipment / De Carvalho Saraiva, Joao Pedro (CERN) ; Brugger, Markus (CERN)
Electronic devices operating in hostile radiation environments, such as those found close to high-energy particle accelerators, can suffer from different types of radiation induced failures. [...]
CERN-ACC-POSTER-2015-0001.
- 2013. - 5 p.

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2015-07-27
11:28
b-flavour tagging in pp collisions
Reference: Poster-2015-500
Keywords:  LHCb
Created: 2015. -1 p
Creator(s): Birnkraut, Alex

An essential ingredient of all time-dependent CP violation studies of B mesons is the ability to tag the initial flavour of the B meson. The harsh environment of 7 and 8 TeV pp collisions makes this a particularly difficult enterprise. We report progresses in the flavour tagging of B0 and Bs mesons, including developments of novel techniques like the use of an opposite side charm tagger.

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2015-07-17
11:24
Layout of the ALICE detector (A Large Ion Collision Experiment), an experiment of the LHC
Schema du détecteur ALICE (A Large Ion Collision Experiment), une expérience de collision d'ions, pour le LHC.

Reference: Poster-2015-499
Keywords:  ALICE  LHC  set-up
Created: 2015. -1 p
Creator(s): Hatzifotiadou, Despina

The ALICE Set-up: 01. PMD 02. TRD 03. EMCAL 04. ACORDE 05. TPC 06. Absorber 07. Dipole Magnet 08-11. Muons 12. T0, V0, FMD 13. PHOS 14. ITS 15. TOF 16. HMPID 17. Solenoid Magnet 18. ZDC

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2015-06-19
11:40
LHCb : Behaviour of Multi-anode Photomultipliers in Magnetic Fields for the LHCb RICH Upgrde
Reference: Poster-2015-498
Keywords:  LHCb  MaPMT  magnetic field  magnetic shield
Created: 2015. -1 p
Creator(s): Gambetta, Silvia

A key feature of the LHCb upgrade, scheduled for 2019, is to remove the first level trigger and its data reduction from 40MHz to 1MHz, which is implemented in the on-detector readout electronics. The consequence for the LHCb Ring Imaging Cherenkov (RICH) detectors is that the Hybrid Photon Detectors need to be replaced as the readout chip is inside the detector vacuum. The baseline for replacement are Multianode Photomultiplier tubes (MaPMT) and new readout electronics. The MaPMTs will be located in the fringe field of the LHCb dipole magnet with residual fields up to 25 G. Therefore, their behaviour in magnetic fields is critical. Here we report about studies of the Hamamatsu models R11265 and H12700 in a magnetic field in an effort to qualify them for use in the LHCb RICH upgrade. Comparisons to the known model R7600 are also made. Measurements of the collection efficiency and gain were performed for all three space directions as a function of the magnetic field strength. In addition to measurements with bare tubes, measurements with different mu-metal shielding configurations were performed to optimize the configuration. This is important input for the layout of the upgraded LHCb RICH detector.

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LHCb poster
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2015-06-10
14:06
LHCb : LHCbVELO: Performance and Radiation Damage in LHC Run I and Preparationfor Run II
Reference: Poster-2015-497
Created: 2015. -1 p
Creator(s): Szumlak, Tomasz

LHCb is a dedicated experiment to study New Physics in the decays of heavy hadrons at the Large Hadron Collider (LHC) at CERN. Heavy hadrons are identified through their flight distance in the Vertex Locator (VELO). The VELO comprises 42 modules made of two n+-on-n 300 um thick half-disc silicon sensors with R-measuring and Phi-measuring micro-strips. In order to allow retracting the detector, the VELO is installed as two movable halves containing 21 modules each. The detectors are operated in a secondary vacuum and are cooled by a bi-phase CO2 cooling system. During data taking in LHC Run 1 the LHCb VELO has operated with an extremely high efficiency and excellent performance. The track finding efficiency is typically greater than 98%. An impact parameter resolution of less than 35 um is achieved for particles with transverse momentum greater than 1 GeV/c. An overview of all important performance parameters will be given. The VELO sensors have received a large and non-uniform radiation dose of up to 1.2 x 10^14 1 MeV neutron equivalent / cm^2 over the first LHC run. Type-inversion has been observed in regions close to the interaction point. Results of various radiation damage analyses will be presented. The preparations for LHC Run 2 are well under way and the VELO has already recorded tracks from injection line tests. The current status and plans for new operational procedures addressing the non-uniform radiation damage will be discussed.

Related links:
LHCb Poster
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2015-06-10
13:55
LHCb : Tracking system of the LHCb upgrade
Reference: Poster-2015-496
Created: 2015. -3 p
Creator(s): Szumlak, Tomasz

The upgrade of the LHCb experiment will run at an instantaneous luminosity of 2x10^33 cm^-2 s^-1 with a fully software based trigger, allowing to read out the detector at a rate of 40MHz. For this purpose, the full tracking system will be newly developed: the vertex locator (VELO) will be replaced by a pixel-based detector, withstanding the high radiation dose and providing an excellent track reconstruction with an efficiency of above 99% for all charged particles of interest. Upstream of the magnet, a silicon mico-strip detector with a high granularity and an improved acceptance coverage, called the Upstream Tracker (UT), will replace the current silicon strip tracker, and provide a rough momentum estimate. The tracking system downstream of the magnet will be replaced by the Scintillating Fibre tracker (SciFi), which will consist of 12 layers using 2.5m long scintillating fibres read out by silicon photo-multipliers, providing a spatial resolution better than 100 micron and resulting in a total momentum resolution of 0.4% for charged particles with a momentum of 20 GeV. We will present the performance of the tracking system for the LHCb upgrade, highlighting the improvements with respect to the current tracking system of LHCb, and review the track finding strategy. Special emphasize will be put on the need for fast track reconstruction in the software trigger, also giving examples of the potential use of parallelism in the pattern recognition. Finally, we will give some prospects of the physics performance with the LHCb upgrade for channels relying on excellent tracking capabilities.

Related links:
LHCb Poster
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2015-06-10
12:26
LHCb : The LHCb Turbo stream
Reference: Poster-2015-495
Created: 2015. -3 p
Creator(s): Puig Navarro, Albert

The LHCb experiment will record an unprecedented dataset of beauty and charm hadron decays during Run II of the LHC, set to take place between 2015 and 2018. A key computing challenge is to store and process this data, which limits the maximum output rate of the LHCb trigger. So far, LHCb has written out a few kHz of events containing the full raw sub-detector data, which are passed through a full offline event reconstruction before being considered for physics analysis. Charm physics in particular is limited by trigger output rate constraints. A new streaming strategy includes the possibility to perform the physics analysis with candidates reconstructed in the trigger, thus bypassing the offline reconstruction. In the "turbo stream" the trigger will write out a compact summary of "physics" objects containing all information necessary for analyses, and this will allow an increased output rate and thus higher average efficiencies and smaller selection biases. This idea will be commissioned and developed during 2015 with a selection of physics analyses. It is anticipated that the turbo stream will be adopted by an increasing number of analyses during the remainder of LHC Run-II (2015-2018) and ultimately in Run-III (starting in 2020) with the upgraded LHCb detector.

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LHCb Poster
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2015-06-10
12:18
LHCb : Performance of the LHCb tracking system in Run I of the LHC
Reference: Poster-2015-494
Created: 2015. -2 p
Creator(s): Davis, Adam

The LHCb tracking system consists of a Vertex Locator around the interaction point, a tracking station with four layers of silicon strip detectors in front of the magnet, and three tracking stations, using either straw-tubes or silicon strip detectors, behind the magnet. This system allows to reconstruct charged particles with a high efficiency (typically > 95% for particles with momentum > 5 GeV) and an excellent momentum resolution (0.5% for particles with momentum < 20 GeV). The high momentum resolution results in very narrow mass peaks, leading to a very good signal-to-background ratio in such key channels as Bs -> mu mu. Furthermore an optimal decay time resolution is an essential element in the studies of time dependent CP violation. Thanks to the excellent performance of the tracking system, a decay time resolution of ~50 fs is obtained, allowing to resolve the fast B0s oscillation with a mixing frequency of 17.7 ps-1. In this talk, we will give an overview of the track reconstruction in LHCb and review its performance in Run I of the LHC. We will highlight the challenges and improvements of the track reconstruction for the data taking period from 2015 on, discussing efforts to improve the timing in the online reconstruction as well as approaches to unify the online and offline reconstruction

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LHCb Poster
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2015-06-10
12:11
LHCb : The LHCb trigger system and its upgrade
Reference: Poster-2015-493
Created: 2015. -2 p
Creator(s): Dziurda, Agnieszka

The current LHCb trigger system consists of a hardware level, which reduces the LHC inelastic collision rate of 30 MHz to 1 MHz, at which the entire detector is read out. In a second level, implemented in a farm of 20k parallel-processing CPUs, the event rate is reduced to about 5 kHz. We review the performance of the LHCb trigger system during Run I of the LHC. Special attention is given to the use of multivariate analyses in the High Level Trigger. The major bottleneck for hadronic decays is the hardware trigger. LHCb plans a major upgrade of the detector and DAQ system in the LHC shutdown of 2018, enabling a purely software based trigger to process the full 30 MHz of inelastic collisions delivered by the LHC. We demonstrate that the planned architecture will be able to meet this challenge. We discuss the use of disk space in the trigger farm to buffer events while performing run-by-run detector calibrations, and the way this real time calibration and subsequent full event reconstruction will allow LHCb to deploy offline quality multivariate selections from the earliest stages of the trigger system. We discuss the cost-effectiveness of such a software-based approach with respect to alternatives relying on custom electronics. We discuss the particular importance of multivariate selections in the context of a signal-dominated production environment, and report the expected efficiencies and signal yields per unit luminosity in several key physics benchmarks the LHCb upgrade.

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LHCb Poster
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2015-06-10
11:56
LHCB : The upgraded LHCb RICH detector: status and perspectives
Reference: Poster-2015-492
Created: 2015. -1 p
Creator(s): Cardinale, Roberta

The LHCb experiment is designed to perform high-precision measurements of CP violation and search for New Physics using the enormous flux of beauty and charmed hadrons produced at the Large Hadron Collider (LHC). The two RICH detectors installed in LHCb have performed successfully during the 2010-2012 data taking period. The data from these detectors were essential to most of the physics results published by LHCb. In order to extend its potential for discovery and study of new phenomena it is planned to upgrade the LHCb experiment in 2018 with a 40MHz readout and a much more flexible software-based triggering system. This would increase the readout rate and occupancies for the RICH detectors. The RICH detector will require new photon detectors and modifications of the optics of the upstream RICH detector. Tests of the complete opto-electronic chain have been performed during testbeam sessions in autumn 2014. The status and perspectives of the RICH upgrade project will be presented.

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LHCb Poster
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Open Days 2013 Posters (58)