This paper describes a measurement of the flavour composition of dijet events produced in pp collisions at root s = 7 TeV using the ATLAS detector. The measurement uses the full 2010 data sample, ...corresponding to an integrated luminosity of 39 pb(-1). Six possible combinations of light, charm and bottom jets are identified in the dijet events, where the jet flavour is defined by the presence of bottom, charm or solely light flavour hadrons in the jet. Kinematic variables, based on the properties of displaced decay vertices and optimised for jet flavour identification, are used in a multidimensional template fit to measure the fractions of these dijet flavour states as functions of the leading jet transverse momentum in the range 40 GeV to 500 GeV and jet rapidity vertical bar y vertical bar < 2.1. The fit results agree with the predictions of leading-and next-to-leading-order calculations, with the exception of the dijet fraction composed of bottom and light flavour jets, which is underestimated by all models at large transverse jet momenta. The ability to identify jets containing two b-hadrons, originating from e. g. gluon splitting, is demonstrated. The difference between bottom jet production rates in leading and subleading jets is consistent with the next-to-leading-order predictions.
We are reporting about a scintillating fibre tracking detector which is proposed for the precise determination of the absolute luminosity of the CERN LHC at interaction point 1 where the ATLAS ...experiment is located. The detector needs to track protons elastically scattered under
μ
rad
angles in direct vicinity to the LHC beam. It is based on square shaped scintillating plastic fibres read out by multi-anode photomultiplier tubes and is housed in Roman Pots. We describe the design and construction of prototype detectors and the results of a beam test experiment at DESY. The excellent detector performance established in this test validates the detector design and supports the feasibility of the proposed challenging method of luminosity measurement.
Data acquisition system for a large TPC Bertrand, D.; De Lentdecker, G.; Dewulf, J-P. ...
2008 IEEE Nuclear Science Symposium Conference Record,
2008-Oct.
Conference Proceeding
A large Time Projection Chamber (TPC) is proposed as part of the tracking system for a detector at the future electron positron linear collider. The Linear Collider TPC (LCTPC) Collaboration is ...currently building a large TPC prototype (60 cm long, with an outer radius of 77 cm), offering some modularity to investigate various gas amplification systems (GEM or MICROMEGAS), pad sizes and geometries as well as different read-out systems. We present the new read-out system developed for this large prototype. It is based on the read-out electronics of the ALICE experiment at the LHC but several modifications have been necessary to adapt it to the expected output signals from the gas amplification systems, including a new programmable charge amplifier. The large prototype and its data acquisition system are being tested in a 6 GeV/c electron beam at DESY (Hamburg). In this paper we describe the TPC data acquisition system, enlightening the novelties and the modifications with respect to the ALICE system. We will also report on the performance of the DAQ system.
The transition radiation tracker (TRT) is one of three particle tracking detectors now under construction for the ATLAS experiment, whose goal is to exploit the highly exciting new physics potential ...at CERN's next accelerator, the so called Large Hadron Collider (LHC). The TRT consists of 370000 straw proportional tubes of 4 mm diameter with a 30 micron thick anode wire, which will be operated with a Xe/CO 2 /O 2 gas mixture at a high voltage of approximately 1.5 kV. While the construction of the TRT is now well under way, a number of interesting and challenging questions need to be solved with regard to wire aging phenomena, which are induced by pollution originating from very small amounts of silicon-based vacuum materials in some components of the gas system. Finally a guideline to avoid aging in wire chamber detectors in high luminosity experiments is given
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