6,935 research outputs found
A Fast General-Purpose Clustering Algorithm Based on FPGAs for High-Throughput Data Processing
We present a fast general-purpose algorithm for high-throughput clustering of
data "with a two dimensional organization". The algorithm is designed to be
implemented with FPGAs or custom electronics. The key feature is a processing
time that scales linearly with the amount of data to be processed. This means
that clustering can be performed in pipeline with the readout, without
suffering from combinatorial delays due to looping multiple times through all
the data. This feature makes this algorithm especially well suited for problems
where the data has high density, e.g. in the case of tracking devices working
under high-luminosity condition such as those of LHC or Super-LHC. The
algorithm is organized in two steps: the first step (core) clusters the data;
the second step analyzes each cluster of data to extract the desired
information. The current algorithm is developed as a clustering device for
modern high-energy physics pixel detectors. However, the algorithm has much
broader field of applications. In fact, its core does not specifically rely on
the kind of data or detector it is working for, while the second step can and
should be tailored for a given application. Applications can thus be foreseen
to other detectors and other scientific fields ranging from HEP calorimeters to
medical imaging. An additional advantage of this two steps approach is that the
typical clustering related calculations (second step) are separated from the
combinatorial complications of clustering. This separation simplifies the
design of the second step and it enables it to perform sophisticated
calculations achieving online-quality in online applications. The algorithm is
general purpose in the sense that only minimal assumptions on the kind of
clustering to be performed are made.Comment: 11th Frontier Detectors For Frontier Physics conference (2009
Measurement of Heavy Quark cross-sections at CDF
The measurement of heavy quark cross-sections provides important tests of the
QCD theory. This paper reviews recent measurements of single b-quark and
correlated b-quark cross-sections at CDF. Two new measurements of the single
b-quark production at CDF agree with the first result from CDF Run II. This
clarifies the experimental situation and confirms the recent agreement of
theoretical prediction with data. A new measurement of the correlated
cross-section with dimuon events at CDF is presented. It agrees with
theory and it does not confirm the anomalously large cross-section
seen in Run I by CDF and D in dimuon events.Comment: EPS HEP2007 conference held in Mancheste
Development of FTK architecture: a fast hardware track trigger for the ATLAS detector
The Fast Tracker (FTK) is a proposed upgrade to the ATLAS trigger system that
will operate at full Level-1 output rates and provide high quality tracks
reconstructed over the entire detector by the start of processing in Level-2.
FTK solves the combinatorial challenge inherent to tracking by exploiting the
massive parallelism of Associative Memories (AM) that can compare inner
detector hits to millions of pre-calculated patterns simultaneously. The
tracking problem within matched patterns is further simplified by using
pre-computed linearized fitting constants and leveraging fast DSP's in modern
commercial FPGA's. Overall, FTK is able to compute the helix parameters for all
tracks in an event and apply quality cuts in approximately one millisecond. By
employing a pipelined architecture, FTK is able to continuously operate at
Level-1 rates without deadtime. The system design is defined and studied using
ATLAS full simulation. Reconstruction quality is evaluated for single muon
events with zero pileup, as well as WH events at the LHC design luminosity. FTK
results are compared with the tracking capability of an offline algorithm.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July
2009, eConf C09072
The Evolution of FTK, a Real-Time Tracker for Hadron Collider Experiments
We describe the architecture evolution of the highly-parallel dedicated
processor FTK, which is driven by the simulation of LHC events at high
luminosity (1034 cm-2 s-1). FTK is able to provide precise on-line track
reconstruction for future hadronic collider experiments. The processor,
organized in a two-tiered pipelined architecture, execute very fast algorithms
based on the use of a large bank of pre-stored patterns of trajectory points
(first tier) in combination with full resolution track fitting to refine
pattern recognition and to determine off-line quality track parameters. We
describe here how the high luminosity simulation results have produced a new
organization of the hardware inside the FTK processor core.Comment: 11th ICATPP conferenc
Search for Higgs-like particles produced in association with bottom quarks in proton-antiproton collisions
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Z boson production in Pb+Pb collisions at √Snn = 5.02 TeV measured by the ATLAS experiment
The production yield of Z bosons is measured in the electron and muon decay channels in Pb+Pb collisions at √S = 5.02 TeV with the ATLAS detector. Data from the 2015 LHC run corresponding to an integrated luminosity of 0.49 nb are used for the analysis. The Z boson yield, normalised by the total number of minimum-bias events and the mean nuclear thickness function, is measured as a function of dilepton rapidity and event centrality. The measurements in Pb+Pb collisions are compared with similar measurements made in proton-proton collisions at the same centre-of-mass energy. The nuclear modification factor is found to be consistent with unity for all centrality intervals. The results are compared with theoretical predictions obtained at next-to-leading order using nucleon and nuclear parton distribution functions. The normalised Z boson yields in Pb+Pb collisions lie 1-3σ above the predictions. The nuclear modification factor measured as a function of rapidity agrees with unity and is consistent with a next-to-leading-order QCD calculation including the isospin effect. nn -
Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb−1 of pp collisions at s=13TeV with the ATLAS experiment
A search for flavour-changing neutral current (FCNC) events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81 fb−1 of proton–proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Events with a photon, an electron or muon, a b-tagged jet, and missing transverse momentum are selected. A neural network based on kinematic variables differentiates between events from signal and background processes. The data are consistent with the background-only hypothesis, and limits are set on the strength of the tqγ coupling in an effective field theory. These are also interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tuγ coupling of 36 fb (78 fb) and on the branching ratio for t→γu of 2.8×10−5 (6.1×10−5). In addition, they are interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tcγ coupling of 40 fb (33 fb) and on the branching ratio for t→γc of 22×10−5 (18×10−5)
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Measurement of Azimuthal Anisotropy of Muons from Charm and Bottom Hadrons in pp Collisions at sqrt[s]=13 TeV with the ATLAS Detector.
The elliptic flow of muons from the decay of charm and bottom hadrons is measured in pp collisions at sqrt[s]=13 TeV using a data sample with an integrated luminosity of 150 pb^{-1} recorded by the ATLAS detector at the LHC. The muons from heavy-flavor decay are separated from light-hadron decay muons using momentum imbalance between the tracking and muon spectrometers. The heavy-flavor decay muons are further separated into those from charm decay and those from bottom decay using the distance-of-closest-approach to the collision vertex. The measurement is performed for muons in the transverse momentum range 4-7 GeV and pseudorapidity range |η|<2.4. A significant nonzero elliptic anisotropy coefficient v_{2} is observed for muons from charm decays, while the v_{2} value for muons from bottom decays is consistent with zero within uncertainties
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