Central Tracking Detector Research Articles

TPC Development by the LCTPC Collaboration for future Higgs factories

A future Higgs factory will impose demanding requirements on the detectors both in precision and in rate. To study the possibility of a time projection chamber as a central tracking detector at such a facility, the Linear Collider TPC (LCTPC) collaboration was founded in 2007. It is investigating various Micropattern Gaseous Detectors as a readout option for such a detector. A test setup was installed at the test beam area at DESY and many test beams campaigns have been performed since 2010. It was demonstrated that the required spatial resolutions could be reached.

TPC development by the LCTPC collaboration for the ILD detector at ILC

The International Large Detector (ILD) at the International Linear Collider (ILC) requires significantly improved subdetector systems to comply with the envisioned performance. Its central tracking detector is a Time Projection Chamber (TPC) which is equipped with Micropattern Gaseous Detector (MPGD) readout modules. The LCTPC collaboration was founded in 2007 to design such a MPGD-based TPC and to build and test demonstrator modules. For this an experimental setup at DESY, Hamburg, was built, where four different readout concepts have been studied in many successful test beam campaigns since 2010. It could be demonstrated that the required transverse and longitudinal space point resolutions can be reached. Also, a new gating concept was developed that can effectively eliminate the ion backflow, while marginally degrading the performance of the detector.

Measuring the light meson nuclear modification factor in p-Pb collisions over an unprecedented $p_{\text{T}}$ range with ALICE

Differential invariant cross sections of light neutral mesons in p-Pb collisions at \sqrt{s_{NN}}sNN = 8.16 TeV and in pp collisions at \sqrt{s}s = 8 TeV have been measured up to very high transverse momentum (p_TpT). By combining independent reconstruction techniques available in ALICE using the EMCal and PHOS calorimeters as well as the central barrel tracking detectors, the combined spectra cover almost two orders of magnitude in p_TpT~for the \pi^0π0~meson. The nuclear modification factor R_{pPb}RpPb~has been measured for the \pi^0π0~and \etaη~mesons and is found to be consistent with NLO pQCD, CGC and energy loss calculations. Comparisons to the R_{pPb}RpPb~of \pi^0π0~measured in \sqrt{s_{NN}}sNN = 5.02 TeV hint at a stronger suppression at low p_TpT~with increasing collision energy.

Measurement of the inclusive isolated photon production cross section in text{ p }text{ p } collisions at sqrt{s}=7 TeV

The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at a centre-of-momentum energy of sqrt{s}= 7 TeV. The measurement is performed with the electromagnetic calorimeter EMCal and the central tracking detectors, covering a range of |eta |<0.27 in pseudorapidity and a transverse momentum range of 10< p_mathrm {T}^{gamma }< 60~mathrm {GeV}/c. The result extends the p_mathrm {T} coverage of previously published results of the ATLAS and CMS experiments at the same collision energy to smaller p_mathrm {T}. The measurement is compared to next-to-leading order perturbative QCD calculations and to the results from the ATLAS and CMS experiments. All measurements and theory predictions are in agreement with each other.

Upgrade of the ALICE central barrel tracking detectors: ITS and TPC

The ALICE Collaboration will undertake a major upgrade of the detector apparatus during the second LHC Long Shutdown LS2 (2019–2020) in view of the Runs 3 and 4 (2021–2029). The objective of the upgrade is two-fold: i) an improvement of the tracking precision and efficiency, in particular in the low-momentum range; ii) an improvement of the readout capabilities of the experiment, in order to fully exploit the luminosity for heavy ions envisaged after LS2. The first goal will be achieved by replacing the Inner Tracking System with a new tracker, composed of seven layers of silicon pixel detectors. The new tracker will be made up of about 25000 Monolithic Active Pixel Sensors with fast readout, resulting in a material thickness reduced to 0.3% (inner layers) – 1% (outer layers) of the radiation length and a granularity of 28×28μm2. The second goal will be achieved, among other measures, by replacing the readout chambers of the 90m3 Time Projection Chamber with Micro Pattern Gaseous Detectors. In particular, the new readout chambers will consist of stacks of 4 Gas Electron Multiplier foils combining different hole pitches. The upgraded detector will operate continuously without the use of a triggered gating grid. It will thus be able to record all Pb–Pb collisions at the LHC interaction rate of 50kHz.

Performance studies of the [formula omitted]ANDA planar GEM-tracking detector in physics simulations

The P¯ANDA experiment will be installed at the future facility for antiproton and ion research (FAIR) in Darmstadt, Germany, to study events from the annihilation of protons and antiprotons. The P¯ANDA detectors can cover a wide physics program about baryon spectroscopy and nucleon structure as well as the study of hadrons and hypernuclear physics including the study of excited hyperon states. One very specific feature of most hyperon ground states is the long decay length of several centimeters in the forward direction. The central tracking detectors of the P¯ANDA setup are not sufficiently optimized for these long decay lengths. Therefore, using a set of the planar GEM-tracking detectors in the forward region of interest can improve the results in the hyperon physics-benchmark channel. The current conceptual designed P¯ANDA GEM-tracking stations contribute the measurement of the particles emitted in the polar angles between about 2 to 22 degrees. For this designed detector performance and acceptance, studies have been performed using one of the important hyperonic decay channel p¯p→Λ¯Λ→p¯pπ+π− in physics simulations. The simulations were carried out using the PandaRoot software packages based on the FairRoot framework.

Forward-central two-particle correlations in p–Pb collisions at [formula omitted

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5<|η|<4.0) and associated particles in the central range (|η|<1.0) are measured with the ALICE detector in p–Pb collisions at a nucleon–nucleon centre-of-mass energy of 5.02 TeV. The trigger particles are reconstructed using the muon spectrometer, and the associated particles by the central barrel tracking detectors. In high-multiplicity events, the double-ridge structure, previously discovered in two-particle angular correlations at midrapidity, is found to persist to the pseudorapidity ranges studied in this Letter. The second-order Fourier coefficients for muons in high-multiplicity events are extracted after jet-like correlations from low-multiplicity events have been subtracted. The coefficients are found to have a similar transverse momentum (pT) dependence in p-going (p–Pb) and Pb-going (Pb–p) configurations, with the Pb-going coefficients larger by about 16±6%, rather independent of pT within the uncertainties of the measurement. The data are compared with calculations using the AMPT model, which predicts a different pT and η dependence than observed in the data. The results are sensitive to the parent particle v2 and composition of reconstructed muon tracks, where the contribution from heavy flavour decays is expected to dominate at pT>2 GeV/c.

Measurement of dijet [formula omitted] in p–Pb collisions at [formula omitted

A measurement of dijet correlations in p–Pb collisions at sNN=5.02 TeV with the ALICE detector is presented. Jets are reconstructed from charged particles measured in the central tracking detectors and neutral energy deposited in the electromagnetic calorimeter. The transverse momentum of the full jet (clustered from charged and neutral constituents) and charged jet (clustered from charged particles only) is corrected event-by-event for the contribution of the underlying event, while corrections for underlying event fluctuations and finite detector resolution are applied on an inclusive basis. A projection of the dijet transverse momentum, kTy=pT,jetch+nesin(Δφdijet) with Δφdijet the azimuthal angle between a full and charged jet and pT,jetch+ne the transverse momentum of the full jet, is used to study nuclear matter effects in p–Pb collisions. This observable is sensitive to the acoplanarity of dijet production and its potential modification in p–Pb collisions with respect to pp collisions. Measurements of the dijet kTy as a function of the transverse momentum of the full and recoil charged jet, and the event multiplicity are presented. No significant modification of kTy due to nuclear matter effects in p–Pb collisions with respect to the event multiplicity or a PYTHIA8 reference is observed.

Front-end electronics and readout system for the ILD TPC

A high resolution TPC is the main option for a central tracking detector at the future International Linear Collider (ILC). It is planned that the MPGD (Micro Pattern Gas Detector) technology will be used for the readout. A Large Prototype TPC at DESY has been used to test the performance of MPGDs in an electron beam of energies up to 6 GeV. The first step in the technology development was to demonstrate that the MPGDs are able to achieve the necessary performance set by the goals of ILC. For this `proof of principle' phase, the ALTRO front-end electronics from the ALICE TPC was used, modified to adapt to MPGD readout. The proof of principle has been verified and at present further improvement of the MPGD technology is going on, using the same readout electronics. The next step is the 'feasibility phase', which aims at producing front-end electronics comparable in size (few mm2) to the readout pads of the TPC. This development work is based on the succeeding SALTRO16 chip, which combines the analogue and digital signal processing in the same chip. This paper summarizes the status of this work and discusses how the experiences made so far can be exploited to improve the final readout electronics.

The alignment of the BESIII drift chamber using cosmic-ray data

BESIII experiment adopts a drift chamber as the central tracking detector. Big distortion of the chamber due to mechanical imperfection causes bad momentum resolution. Software alignment is the only possible strategy to estimate the displacements of sub-endplates of the chamber. We have developed an alignment software in the framework of the BESIII Offine Software System. Cosmic-ray data are used in preliminary alignment. The alignment method is introduced in the paper. The results of the alignment are also presented.

MUNU final results

The MUNU detector has been designed to study ν e ¯ e − elastic scattering at low energy. The central tracking detector is a 1 m3 Time Projection Chamber surrounded by an anti-Compton detector. In this paper the results from final analysis of the data recorded at 3-bar and 1-bar pressure are presented. At 3-bar a new upper limit on the neutrino magnetic moment μ ν 9 × 10 − 11 ( 7 × 10 − 11 ) μ B at 90 (68%) C.L. is derived. At 1-bar pressure electron tracks down to 80 keV are measured in the TPC. A 137Cs photopeak is reconstructed by measuring both the energy and direction of the Compton electrons in the TPC.

Charged particle identification with PHOS and central tracking of ALICE

The ALICE Photon Spectrometer (PHOS) has been designed to measure the photon spectrum produced in pp and AA collisions at LHC over a broad transverse momentum range from 0.5–100 GeV/c. We present a study on the matching of charged tracks, detected by the ALICE central tracking detectors, with clusters of hit PHOS elements. Matching efficiency and contamination due to false matches have been deduced for charged pions, muons and electrons. The study indicates also that material from other detectors in front of PHOS disturbs the photon detection.

High pt and photon physics with ALICE at LHC

ALICE, A Large Ion Collider Experiment, is dedicated to study the QCD matter at extreme high temperature and density to understand the Quark Gluon Plasma (QGP) and phase transition. High-transverse-momentum photons and neutral mesons from the initial hard scattering of partons can be measured with ALICE calorimeters, PHOS (PHOton Spectrometer) and EMCAL (ElectroMagnetic CALorimeter). Combing the additional central tracking detectors, the γ-jet and π0-jet measurements thus can be accessed. These measurements offer us a sensitive tomography probe of the hot-dense medium generated in the heavy ion collisions. In this paper, high pT and photon physics is discussed and the ALICE calorimeters capabilities of high-transverse-momentum neutral mesons and γ-jet measurements are presented.

Construction and tests of the MRPC detectors for TOF in ALICE

CERN-LHC (Large Hadron Collider) accelerator facility will provide heavy ions (Pb–Pb) collisions with a center-of-mass (CM) energy of about 5.5 TeV per nucleon pair. In the extreme conditions of temperature and energy density created in such collisions, a transition from hadronic matter towards a deconfined state of quarks and gluons is predicted by Quantum Chromodynamics (QCD) calculations on the lattice. The Time Of Flight (TOF) detector system of the ALICE (A Large Ion Collider Experiment) apparatus, is presently progressing in the assembling process at LHC at CERN. The TOF, in combination with the other central tracking detectors of ALICE provides an excellent Particle IDentification (PID) in the momentum range 0.2 – 2.5 GeV / c for K / π and up to 4 GeV/ c for K/p. The ALICE TOF is a barrel detector consisting of double-stack Multigap Resistive Plate Chamber (MRPC) strips, equipped with readout pads. The MRPC is characterized by an intrinsic time resolution below 50 ps and an efficiency over 99%. The assembling procedures, the tests of mechanics, cooling system and electronics of the 8 m long TOF “supermodules”, together with the performance tests before installation in the experimental area, will be presented.

The design and performance of the ZEUS global tracking trigger

The Global Tracking Trigger (GTT) of the ZEUS experiment is described. The GTT is data driven at the ZEUS first level trigger rate of ⩽ 600 Hz and performs event-based track finding on data from the experiment's Central Tracking Detector (CTD), silicon Micro Vertex Detector (MVD) and Straw Tube Tracker (STT) forward detectors. The resulting track-based trigger quantities calculated (track multiplicity, vertices, vector meson masses, background event probabilities, etc.) are available within ∼ 9 ms and are used in the experiment's second level trigger to improve the selection of physics events. Detector information is pushed to the PC farm of the GTT using PowerPC VME board computers which are either embedded within the detector's frontend readout system (MVD) or are parasitically attached to them via multiple serial transputer links (CTD and STT). Data flow and control is performed via point-to-point Fast and Giga ethernet switched network connections using the TCP protocol. The principal design challenges were: integrating new and interfacing to existing frontend systems, providing a useful trigger result, satisfying the rate and latency requirements and not interfering with ongoing data taking during commissioning. These aims have been achieved. The GTT has been actively used in the ZEUS trigger since 2004 when an initial CTD-only algorithm was used; in 2005 this was upgraded to use MVD information which significantly improves track and primary vertex resolutions. Commissioning problems delayed the STT implementation and its use in the GTT has only been tested.

The optical alignment system of the ZEUS microvertex detector

The laser alignment system of the ZEUS microvertex detector is described. The detector was installed in 2001 as part of an upgrade programme in preparation for the second phase of electron–proton physics at the HERA collider. The alignment system monitors the position of the vertex detector support structure with respect to the central tracking detector using semi-transparent amorphous-silicon sensors and diode lasers. The system is fully integrated into the general environmental monitoring of the ZEUS detector and data has been collected over a period of 5 years. The primary aim of defining periods of stability for track-based alignment has been achieved and the system is able to measure movements of the support structure to a precision around 10 μ m .

Study of QGP signatures with the ϕ → K + K – signal in Pb-Pb ALICE events

The phi->K+K- decay channel in Pb-Pb collisions at LHC is studied through a full simulation of the ALICE detector. The study focuses on possible signatures in this channel of quark-gluon plasma (QGP) formation. On a basis of 10^6 collisions at high centrality some proposed QGP signatures are clearly visible both in K+K- invariant mass and transverse mass distributions. The high significance of this observation appears to reside heavily on the use of the TOF (Time Of Flight) system of ALICE in addition to its central tracking detectors.

Study of QGP signatures with the ϕ → K + K – signal in Pb-Pb ALICE events

The ϕ → K+K– decay channel in Pb-Pb collisions at LHC is studied through a full simulation of the ALICE detector. The study focuses on possible signatures in this channel of quark-gluon plasma (QGP) formation. On a basis of 106 collisions at high centrality some proposed QGP signatures are clearly visible both in K + K– invariant mass and transverse mass distributions. The high significance of this observation appears to reside heavily on the use of the TOF (Time Of Flight) system of ALICE in addition to its central tracking detectors.

Resolution studies of cosmic-ray tracks in a TPC with GEM readout

A large volume time projection chamber (TPC) is a leading candidate for the central tracking detector at a future high energy linear collider. To improve the resolution a new readout based on micro-pattern gas detectors is being developed. Measurements of the spatial resolution of cosmic-ray tracks in a GEM TPC are presented. We find that the resolution suffers if the readout pads are too wide with respect to the charge distribution at the readout plane due to insufficient charge sharing. For narrow pads of 2 × 6 mm 2 we measure a resolution of 100 μ m at short drift distances in the absence of an axial magnetic field. The dependence of the spatial resolution as a function of drift distance allows the determination of the underlying electron statistics. Our results show that the present technique uses about half the statistical power available from the number of primary electrons. The track angle effect is observed as expected.

Experience with the ZEUS central tracking detector

The central tracking detector of the ZEUS experiment has been in operation since 1992. It is a cylindrical drift chamber, approximately 2 m in length and 1 m in diameter, and has operated reliably in a magnetic field of 1.43 T using a gas mixture of 83:12:5 argon/CO 2/ethane with a trace (∼0.5%) of ethanol. Initial studies conducted between 1995 and 2000 using d E/d x to search for a long-term loss of gain were inconclusive. During the course of 2000, operational problems caused by repeated trips of high-voltage in the outer superlayers of the detector were experienced. These were attributed to the Malter effect, which has shown to be alleviated by the addition of water to the gas mixture. Consequently, a trace of water (∼0.15%) was added to the gas and has, to date, proved to be a successful remedy. Changes in the chamber performance due to the additional water are covered and solutions to the problems encountered are detailed.