34,142 research outputs found
Operational experience with the ALICE pixel detector
No full textThe Silicon Pixel Detector (SPD) constitutes the two innermost layers of
the Inner Tracking System of the ALICE experiment and it is the closest
detector to the interaction point. As a vertex detector, it has the
unique feature of generating a trigger signal that contributes to the L0
trigger of the ALICE experiment. The SPD started collecting data since
the very first pp collisions at LHC in 2009 and since then it has taken
part in all pp, Pb-Pb and p-Pb data taking campaigns. This contribution
will present the main features of the SPD, the detector performance and
the operational experience, including calibration and optimization
activities from Run 1 to Run 2
Performance of the ALICE SPD cooling system
No full textThe new generation of silicon detectors for particle physics requires very reduced mass and high resistance to radiations with very limited access to the detector for maintenance. The Silicon Pixel Detector (SPD) is one of the 18 detectors of the ALICE (A Large Ion Collider Experiment) experiment at the Large Hadron Collider (LHC) at CERN. It constitutes the two innermost layers of the Inner Tracking System (ITS) and it is the closest detector to the interaction point.
An evaporative cooling system, based on C4F10 evaporation at 1.9 bar, was chosen to extract the 1.35 kW power dissipated by the on-detector electronics. The whole system was extensively tested and commissioned before its installation inside the ALICE experimental area. Since then we had to deal with a decrease of the flow in some lines of the system that imposed severe restrictions on the detector operation. Recently, a test bench has been built in order to carry out a series of tests to reproduce the misbehaviour of the system and investigate proper actions to cure the problem.
The performance of the systems and the most interesting results of the above mentioned tests will be presented
The ALICE TPC : a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events
No full textThe design, construction, and commissioning of the ALICE Time-Projection Chamber (TPC) is described. It is the main device for pattern recognition, tracking, and identification of charged particles in the ALICE experiment at the CERN LHC. The TPC is cylindrical in shape with a volume close to 90 m3 and is operated in a 0.5 T solenoidal magnetic field parallel to its axis.
In this paper we describe in detail the design considerations for this detector for operation in the extreme multiplicity environment of central Pb–Pb collisions at LHC energy. The implementation of the resulting requirements into hardware (field cage, read-out chambers, electronics), infrastructure (gas and cooling system, laser-calibration system), and software led to many technical innovations which are described along with a presentation of all the major components of the detector, as currently realized. We also report on the performance achieved after completion of the first round of stand-alone calibration runs and demonstrate results close to those specified in the TPC Technical Design Report
J/ψ production measurement at midrapidity from pp to Pb-Pb collisions with ALICE
No full textThe charmonium states provide essential information on the properties of a new state of matter predicted to be formed at extreme energy densities and temperatures, the Quark Gluon Plasma (QGP). ALICE is an experiment at LHC dedicated to the study of the QGP state in heavy ion collisions. The ALICE results on the J/ψ production using the dielectron decay channel in pp collisions at 7 TeV and Pb-Pb collisions at √sNN = 2.76 TeV will be discussed. Due to its excellent vertexing capabilities, ALICE can separate the non-prompt J//ψ component thus allowing for a measurement of the beauty production. beauty production. ALICE is the only experiment that measures the charmonium production at central rapidity (|y| < 0.9) down to pT=0
Charakterisierung von dem ALice-Tpc-ReadOut-Chip
No full textDie vorliegende Arbeit beschäftigt sich mit der Charakterisierung des ALTRO Chips (ALICE TPC Readout), der ein integraler und wichtiger Bestandteil der Auslesekette des TPC (Time Projection Chamber) Detektors von ALICE (A Large Ion Collider Experiment) ist. ALICE ist ein Experiment am noch im Bau befindlichen LHC (Large Hadron Collider) am CERN mit der zentralen Ausrichtung, Schwerionenkollisionen zu untersuchen. Diese sind von besonderem Interesse, da durch sie ein experimenteller Zugriff zu dem QGP (Quark Gluon Plasma) existiert, dem einzigen vom Standardmodell vorhergesagten Phasenübergang, der unter Laborbedingungen erreichbar ist. Im Jahr 2004 wurden Messungen an einem Teststrahl am CERN PS (Proton Synchrotron) durchgeführt. Der Prototyp wurde voll mit FECs bestückt, was 5400 Kanälen entspricht und einer anderen Gasmixtur (Ne/N2/CO2 90%/5%/5%) befüllt. Für das optimale Leistungsverhalten der ALICE TPC muß der Digitalprozessor im ALTRO, bestehend aus vier Berechnungseinheiten, mit den passenden Werten konfiguriert werden. Der Datenfluss beginnt mit dem BCS1 (Baseline Correction and Subtraction 1) Modul, das systematische Störungen und die Grundlinie entfernt. Da der ALTRO kontinuierlich das anliegende Signal abtastet, entfernt es automatisch langsame Grundlinienveränderungen, die Beispielsweise durch Temperaturänderungen auftreten können. Gefolgt von dem TCF (Tail Cancellation Filter), der den Schweif des langsam fallenden, vom PASA generierten Signals entfernt. Um die nichtsystematischen Störungen der Grundlinie zu entfernen, folgt die BCS2 (Baseline Correction and Subtraction 2), die auf einer gleitenden Mittelwertsberechnung mit Ausschluß von Detektorsignalen über einen doppelten Schwellenwert basiert. Die finale Einheit für die Signalverarbeitung ist die ZSU (Zero Suppression Unit), die Meßpunkte unterhalb eines definierten Schwellwertes entfernt. Hier wird der weg beschrieben die TCF und BCS1 Parameter aus vorhandenen Detektordaten zu extrahieren. Während der Analyse der Daten von kosmischen Teilchen fiel bei Signalen mit hoher Amplitude (>700 ADC) eine zusätzliche Struktur in dem Schweif auf. Der Monitor wurde deswegen mit einem gleitenden Mittelwertfilter erweitert, worauf sich diese Struktur auch in kleineren Signalen (> 200 ADC) zeigte. Dieses Signal wird von Ionen erzeugt, die zur Kathode oder zu den Pads driften, bisher ist jedoch weder die Streuung der Elektronenlawine an der Anode, noch die Variationsbreite in den erzeugten Elektronlawinen verstanden oder gemessen worden. Eine erfolgreiche Messung, sowie Charakterisierung wird in dieser Arbeit beschrieben. Im Jahr 2005 im Sommer beginnt der Einbau der Gaskammern der TPC in ALICE, die Elektronik folgt am Ende dieses Jahres. Parallel hierzu wurde der Prototyp der TPC wieder in Betrieb genommen und im Frühling wird ein kompletter Sektor mit der Detektorelektronik ausgestattet. An diesen zwei Aufbauten wird die ALTRO Charakterisierung fortgeführt, verfeinert und komplettiert
The pixel module for the Inner Tracking System upgrade of ALICE at LHC
No full textThe ALICE (A Large Ion Collider Experiment) detector at the CERN LHC collider was designed to address
the physics of strongly interacting matter, and in particular the properties of the Quark-Gluon
Plasma (QGP) using proton-proton, proton-nucleus, and nucleus-nucleus collisions. Even if with
this physics goal a lot of important results were already reached, there are still several fundamental
measurements to be finalized, like high precision measurements of rare probes (D, B mesons and
Lambda barions decays) over a broad range of transverse momenta. In order to achieve these new
results, a wide upgrade plan was approved that combined with a significant increase of luminosity
will enhance the ALICE physics capabilities enormously.
The ALICE Inner Tracking System (ITS) upgrade is one of the major improvements of the experimental
set-up that will take place in 2019-2020 where the whole ITS sub-detector will be replaced with
a new one realized using a innovative CMOS Monolithic Active Pixel silicon Sensor (MAPS), called
ALPIDE. This new upgraded ITS will be realized using more than twenty-four thousand ALPIDE
chips organized in seven different cylindrical layers surrounding the ALICE interaction point along
the beam-line, for a total surface of about ten square meters. The main features of the future ALICE
ITS are a low material budget, high granularity and low power consumption. All these peculiar capabilities
will allow for full reconstruction of rare heavy flavor decays and the achievement of the
physics goals.
In this talk after a description of new ALIPIDE pixel chip and the whole ITS upgrade project, will be
presented the construction procedure of the basic building block of the detector, namely the module,
and the laboratory characterization of this element
Validation of the 65 nm TPSCo CMOS imaging technology for the ALICE ITS3
No full textDuring the next Long Shutdown (LS3) of the LHC, planned for 2026, the innermost three
layers of the ALICE Inner Tracking System will be replaced by a new vertex detector composed of curved ultra-thin monolithic silicon sensors. The R&D initiative on monolithic sensors of the CERN Experimental Physics Department, in cooperation with the ALICE ITS3 upgrade project, prepared the first submission of chip designs in the TPSCo 65 nm technology, called MLR1 (Multi Layer Reticle). It contains four different test structures with different process splits and pixel designs. These proceedings illustrate the first validation of the technology in terms of pixel performance and radiation hardness
Production of identified and unidentified charged hadrons in Pb--Pb collisions at \sqrts_\rm NN~5.02~TeV
No full textIn late 2015, the ALICE collaboration recorded data from Pb--Pb collisions at
the unprecedented energy of \sqrts_\rm NN~5.02~TeV. The transverse-momentum
(p_\rm T) spectra of pions, kaons and protons are presented. The evolution
of the particle ratios as a function of collision energy and centrality is
discussed. The ratio between p_\rm T-integrated particle yields are
measured and compared to different collision energies as well as smaller
collision systems. For the study of energy loss mechanisms in the QCD medium at
high transverse momenta, the nuclear modification factors () are
computed and compared with results obtained at lower energy
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