Search

An overview of the first B-physics results from the LHC is presented, among which are various aspects of b production, rare B decays and CP violation. [ABSTRACT FROM AUTHOR]

Abstract: In the LHCb experiment at the Large Hadron Collider, powerful charged particle identification is performed by Ring Imaging CHerenkov (RICH) technology. In order to cover the full geometric acceptance and the wide momentum range (1–100GeV/c), two detectors with three Cherenkov radiators have been designed and installed. In the medium (10–40GeV/c) and high (30–100GeV/c) momentum ranges, gas radiators are used (C4F10 and CF4, respectively). In the low momentum range (1–10GeV/c), pion, kaon and proton separation is performed with solid silica aerogel radiator. A set of 16 tiles, with large transverse dimensions of up to and nominal refractive index 1.03 have been produced and integrated in the detector. These tiles have excellent optical properties and homogeneity of the refractive index at the percent level within the tile. The first data collected at the LHC are used to investigate the behaviour of the RICH; preliminary results of the performance of silica aerogel are presented and discussed. [Copyright &y& Elsevier]

Abstract: The LHCb experiment, currently operating at CERN, is designed for the precision measurement of CP violation and other rare phenomena in the decays of B hadrons. LHCb employs two RICH detectors to provide particle identification essential for this physics program. To reach design performance, the geometrical alignment of the RICH detectors should be established and calibrations made for the effects of the LHCb magnetic field. This paper describes the procedures developed towards this alignment and calibration using data from LHC collisions which began on 23 November 2009. [Copyright &y& Elsevier]

Abstract: Particle identification is one of the key requirements of the LHCb experiment. The ability to distinguish between pions, kaons and protons in a variety of final states is essential for the study of CP violation and rare decays of B hadrons. The particle identification system is composed of two RICH detectors, covering the full angular acceptance of the spectrometer and designed to give particle identification for the momentum range of 1 up to 100GeV/c. The two RICH detectors are based on gaseous (C4F10 and CF4) and aerogel radiators and an optical system of spherical and flat mirrors which focuses the Cherenkov photons onto the photon detectors planes. These are equipped with a total of 484 Hybrid Photon Detectors (HPDs). The silicon pixel detector of each HPD is read out to give a resolution on the photocathode of . First experience and results from RICH commissioning and operation at the LHC will be discussed. [Copyright &y& Elsevier]

Abstract: The Very High Momentum Charged Particle Identification (VHMPID) detector represents a possible upgrade for the ALICE experimental apparatus. It has been conceived to extend protons identification on a track-by-track basis up to p=30GeV/c. The VHMPID is a ring imaging Cherenkov with C4F10 gaseous radiator coupled to CsI-based photon detector. The focusing properties of a spherical mirror are exploited to focus Cherenkov photons on the photon detector. Mirror segmentation is a critical parameter for the ring pattern recognition performance and for the capability to identify tracks close in phase space. This feature is crucial for the contribution of VHMPID to the ALICE jets physics program. We will present the results of simulation studies that have been carried out in order to optimize the mirror segmentation. [Copyright &y& Elsevier]

Abstract: The LHCb experiment will search for new physics in CP violation and rare decays from heavy flavour production at the LHC. Particle identification is provided by two Ring Imaging Cherenkov (RICH) detectors, which incorporate a total of 484 Hybrid Photon Detectors (HPDs). The RICH detectors are located in the fringe field of the LHCb dipole magnet and fields as large as 2.5mT have been measured in some regions occupied by the RICH 1 photodetectors. It is necessary to make corrections for the distortion of the ring-images measured by the HPDs. RICH 1 incorporates a magnetic calibration system comprising a series of collimated LEDs mounted on x–y stages which scan over the front-faces of the HPD arrays. A similar system based on commercial projectors is used on RICH 2. The calibration is performed in dedicated runs with dipole field on and off. The calibration parameters are then stored in the Conditions Database and applied to the LHC collision data reconstruction. This report will present the improvement in Cherenkov angular resolutions with the magnetic calibration. [Copyright &y& Elsevier]

Abstract: The ALICE High Momentum Particle Identification RICH detector (HMPID) was installed, with its 10m2 of Cesium Iodide (CsI) photo-cathodes, in the ALICE experiment at the Large Hadron Collider (LHC) in 2006. Since then, it has been thoroughly commissioned, together with its auxiliary systems, with cosmic rays and particles from beam dump/splash events recorded during various LHC injection tests in 2008 and 2009. Finally, the HMPID has successfully detected particles produced by the first proton–proton collisions at LHC in winter 2009. The present paper reviews the experience gained during the commissioning phase and summarizes the present status of the detector. Preliminary results concerning the detector performance are also reported. [Copyright &y& Elsevier]

Abstract: Particle identification in the LHCb experiment is provided by two RICH detectors, covering a momentum range of approximately 1–100GeV/c. To maintain the integrity of the LHCb physics performance, it is essential to measure and monitor the particle identification efficiency and misidentification fraction over time. To achieve this, the unique decay kinematics associated with K S 0, and decays are exploited to obtain high purity samples of pions, protons and kaons through the use of tracking information alone. Such calibration samples then allow for an unbiased assessment of the performance of the RICH detectors. Given the high production rates of K S 0, and mesons at the LHC, monitoring of the RICH detectors performance is possible both “on-line” during running and “off-line” after full-reconstruction of the data. Following analysis of the first LHC collisions, the performance of the LHCb RICH detectors will be presented based on a preliminary alignment of the detector. Identification and mis-identification probabilities as a function of track momentum will be shown. [Copyright &y& Elsevier]

Abstract: Results are presented on the commissioning and operation of Hybrid Photon Detectors used in the Ring Imaging Cherenkov detectors of LHCb. Cherenkov photons from proton–proton interactions at a centre-of-mass energy of 7TeV have been recorded. An explanation is given of the steps that have been taken to achieve these results. [Copyright &y& Elsevier]

Abstract: RHIC results have shown the importance of high momentum particles as hard probes and the need for particle identification (PID) in a very large momentum range. A Very High Momentum PID (VHMPID) detector has been proposed as upgrade of ALICE to extend the track-by-track identification capabilities for charged hadrons from the present 5GeV/c limit to the momentum range 10–30GeV/c. The VHMPID detector is a focusing RICH using C4F10 gaseous radiator coupled to a CsI-based photon detector. Detector design studies, achievable Cherenkov angle resolution, expected performance and high momentum triggering will be discussed. [Copyright &y& Elsevier]

Abstract: The LHCb experiment is designed to operate at an LHC luminosity of 2×1032 cm−2 s−1, or typically one collision per bunch crossing. After about five years it will have recorded a data sample of 10fb−1. At this time LHCb plans an upgrade to operate the detector at a significantly increased luminosity that will greatly extend its potential for discovery and study of new phenomena. Studies performed to optimise the design of the LHCb upgrade are presented. The RICH detector will require new photon detectors as the current HPDs have encapsulated electronics which only support a readout rate of up to 1MHz. Multi-anode and flat-panel photo multiplier tubes (PMTs) are evaluated as photon detector candidates and their properties including pulse height, shape and cross-talk are measured. The particle identification performance is studied as a function of luminosities ranging up to ten times the design as foreseen for the LHCb upgrade. Finally, the performance of flavour tagging using kaons, which strongly relies on RICH particle identification is also presented. [Copyright &y& Elsevier]

Abstract: We propose to construct and install a limited acceptance detector to identify hadrons (pions, K, p) up to 30GeV/c on a track-by-track basis in space available in ALICE. Details and PID performance simulation results will be presented for two possible options, including a high transverse momentum () trigger for this detector. The first option is a RICH design with a gas UV-photon radiator, UV-mirror, quartz window and pad-readout. This design requires additional tracking detectors to enable high triggering. A second option is a combination of three detectors: a RICH with gas both as a UV-photon radiator and as a gas amplification medium (a windowless approach); and a threshold Cherenkov detector () with a quartz window and pad readout. The response for minimum ionizing particles (MIP) and UV-photons in these detectors can be well separated. With an additional tracking detector this design will also provide high triggering. The simulation includes UV-photon production due to scintillation. [Copyright &y& Elsevier]

Abstract: The LHCb experiment at the Large Hadron Collider has been optimised for high precision measurements of the charm and beauty quark sector. The different particle species produced in the high-energy collision are identified using two Ring-Imaging Cherenkov detectors. [Copyright &y& Elsevier]

Abstract: The LHCb experiment, currently being commissioned at CERN, uses two Ring Imaging Cherenkov (RICH) detectors as its principal particle identification system. These detectors are essential in allowing LHCb to perform the precision measurements of CP-violation in B-meson mixing and decays for which the experiment was designed. The photodetectors used in the LHCb RICH system are Hybrid Photon Detectors (HPDs), which employ a vacuum photocathode and a solid-state pixel sensor. The operating principle and production process of the HPDs are described. The performance criteria for the HPDs is outlined, along with the qualification procedures carried out at dedicated test facilities. The compiled results of tests performed on more than 500 HPDs are presented. The performance of the HPDs in a 25ns structured test-beam and during the RICH commissioning process with the HPDs installed is discussed. Finally, the time alignment of the HPDs via a pulsed laser system is described. [Copyright &y& Elsevier]

Abstract: A modular power supply system is described, for use in the Ring Imaging Cherenkov Detectors of the LHCb experiment. The main characteristics of the supply are very good time stability and voltage resolution, full programmability, floating supplies, self protection and remote control. The choice of a commercial HV module with standard control inputs allows easy customisation to adapt our design to different requirements. The realisation shown here supplies voltages up to 20kV with a maximum current of 0.5mA and up to 32 channels on a single crate. [Copyright &y& Elsevier]

Abstract: The LHCb experiment is a single forward arm spectrometer at the LHC at CERN. Particle identification (pion, kaon and proton discrimination) is a crucial requirement to meet the physics goals of the experiment. This is provided by two Ring Imaging Cherenkov (RICH) detectors providing particle identification coverage between 1 and 100GeV/c. After a brief description of the LHCb experiment and RICH detectors, the results from the latest beam test using the final detector components and readout system will be given and the anticipated particle identification performance of the RICH detectors from Monte Carlo simulations will be presented. Finally, a technique to calibrate the particle identification performance of the RICH system with data using decays will be described. [Copyright &y& Elsevier]

Abstract: Pion/kaon discrimination in the LHCb experiment will be provided by two Ring Imaging Cherenkov (RICH) counters. These use arrays of 484 Hybrid Photon Detectors (HPDs) to detect the Cherenkov photons emitted by charged particles traversing the RICH. The results from comprehensive quality assurance tests on the 550 HPDs manufactured for LHCb are described. Leakage currents, dead channel probabilities, dark count rates and ion feedback rates are reported. Furthermore, results from two specialised measurements carried out on a sample of HPDs to determine the efficiencies of the HPD pixel chip and photocathode, respectively, are described. Finally, an overview is given of the in situ performance of the HPDs which are now installed in the RICH. [Copyright &y& Elsevier]

Abstract: The LHCb experiment at the CERN Large Hadron Collider (LHC) utilises two Ring Imaging CHerenkov (RICH) detectors for particle identification. To verify that the RICH assembly will perform as expected prior to installation, an array of 48 production Hybrid Photon Detectors and their readout have been tested under realistic running conditions in a 25ns-structured charged particle beam provided by the SPS facility at CERN. This system test is an important milestone in the overall commissioning of the LHCb detector and demonstrates that all aspects meet the stringent physics requirements of the LHCb experiment. [Copyright &y& Elsevier]

Abstract: The status of the Ring Imaging Cherenkov system of the LHCb experiment is reviewed. The detector is in the commissioning phase and it is expected to take data later this year at the start-up of the Large Hadron Collider, providing essential contributions to the physics program of the experiment. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to present the design, the implementation and the operational modes of the Liquid Circulation System (LCS) built to circulate, purify and monitor the liquid perfluorohexane (C6F14) in the ALICE HMPID. The HMPID RICH uses C6F14 as Cherenkov radiator medium circulating in 21 quartz trays. LCS features a pressure-regulated closed circuit, ensuring the C6F14 highest transparency to ultraviolet light. Intrinsically safe working conditions are obtained, thanks to a novel liquid distribution “cascade” system. Moreover the system is protected against anomalous working conditions by a dedicated Control System, which operates it in both automatic and manual mode, locally and remotely, safeguarding the quartz radiator vessels. [Copyright &y& Elsevier]

Abstract: The main luminosity monitor of the ATLAS experiment consists of an array of Cherenkov counters. The intrinsically fast response of the detector and its readout electronics makes it ideal for measuring the number of interactions per LHC bunch crossing, and for providing an interaction trigger to the ATLAS experiment. The detector already took some data during the first beam interactions produced by the LHC. An original method to derive the detector response with an analytical approach is presented here. [ABSTRACT FROM AUTHOR]

Abstract: The LHCb experiment at the Large Hadron Collider has been optimised for high precision measurements of the charm and beauty quark sector. Efficient particle identification at high purities over a wide momentum range from around 1 to 100GeV/c is vital to many LHCb analyses. Central to the LHCb particle identification strategy are two Ring Imaging CHerenkov (RICH) detectors. Rigorous monitoring of the RICH sub-detector is being developed to insure that high-quality data is recorded which meets the stringent demands from physics analyses. [Copyright &y& Elsevier]

Abstract: The long-term development of the Ion Feedback rate of Hybrid Photon Detectors in the LHCb Ring Imaging Cherenkov detectors was studied as a sensitive measure of the vacuum quality. From a phenomenological understanding of the development reliable predictions can be made for individual photon detectors. Eighty percent of them will operate well for the lifetime of LHCb. In a 20% subsample a faster-than-expected degradation of the vacuum quality was found. A HPD repair and replacement programme guarantees a good performance of the LHCb RICH detector at all time during data taking. [Copyright &y& Elsevier]

Abstract: We describe the characterization of the high-voltage (HV) distribution system designed and produced for the pixel hybrid photon detectors of the ring imaging Cherenkov counters of the LHCb experiment. The HV system consists of a series of printed circuit boards with a specific layout designed to prevent any discharge arising from high electric fields. The system has dedicated monitoring and control features to supervise HV set-up during data taking. The full production of the HV system has been now completed and all the boards have been fully characterized and installed in the detector, which is currently being commissioned. [Copyright &y& Elsevier]

Abstract: The ALICE HMPID (High Momentum Particle IDentification) detector has been designed to identify charged pions and kaons in the range and protons in the range . It consists of seven identical proximity focusing RICH (Ring Imaging Cherenkov) counters, covering in total 11 m2, which exploit large area MWPC equipped with CsI photocathodes for Cherenkov light imaging emitted in a liquid C6F14 radiator. The ALICE detector has been widely commissioned using cosmics and LHC beam from December 2007 until October 2008. During the cosmics data taking the HMPID detector collected a large set of data, using mainly the trigger provided by the TOF detector. We present here preliminary results of detector alignment using TPC tracking. The HMPID could be operated in a stable way, at a safe HV setting, also during LHC beam injection and circulation tests, when a very large occupancy (up to 50%) was achieved. Resulting gain mapping and overall detector performance will also be discussed. [Copyright &y& Elsevier]