Abstract
The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) will produce particle collisions with up to 200 simultaneous proton-proton interactions. These unprecedented conditions will ...create a combinatorial complexity for charged-particle track reconstruction that demands a computational cost that is expected to surpass the projected computing budget using conventional CPUs. Motivated by this and taking into account the prevalence of heterogeneous computing in cutting-edge High Performance Computing centers, we propose an efficient, fast and highly parallelizable bottom-up approach to track reconstruction for the HL-LHC, along with an associated implementation on GPUs, in the context of the Phase 2 CMS outer tracker. Our algorithm, called Segment Linking (or Line Segment Tracking), takes advantage of localized track stub creation, combining individual stubs to progressively form higher level objects that are subject to kinematical and geometrical requirements compatible with genuine physics tracks. The local nature of the algorithm makes it ideal for parallelization under the Single Instruction, Multiple Data paradigm, as hundreds of objects can be built simultaneously. The computing and physics performance of the algorithm has been tested on an NVIDIA Tesla V100 GPU, already yielding efficiency and timing measurements that are on par with the latest, multi-CPU versions of existing CMS tracking algorithms.
In the High-Luminosity Large Hadron Collider (HL-LHC), one of the most challenging computational problems is expected to be finding and fitting charged-particle tracks during event reconstruction. ...The methods currently in use at the LHC are based on the Kalman filter. Such methods have shown to be robust and to provide good physics performance, both in the trigger and offline. In order to improve computational performance, we explored Kalman-filter-based methods for track finding and fitting, adapted for many-core SIMD (single instruction, multiple data) and SIMT (single instruction, multiple thread) architectures. Our adapted Kalman-filter-based software has obtained significant parallel speedups using such processors, e.g., Intel Xeon Phi, Intel Xeon SP (Scalable Processors) and (to a limited degree) NVIDIA GPUs. Recently, an effort has started towards the integration of our software into the CMS software framework, in view of its exploitation for the Run III of the LHC. Prior reports have shown that our software allows in fact for some significant improvements over the existing framework in terms of computational performance with comparable physics performance, even when applied to realistic detector configurations and event complexity. Here, we demonstrate that in such conditions physics performance can be further improved with respect to our prior reports, while retaining the improvements in computational performance, by making use of the knowledge of the detector and its geometry.
The timing system for the CDF electromagnetic calorimeters Goncharov, M.; Kamon, T.; Khotilovich, V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2006, Letnik:
565, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We report on the design and performance of the electromagnetic calorimeter timing readout system (EMTiming) for the Collider Detector at Fermilab (CDF). The system will be used in searches for rare ...events with high-energy photons to verify that the photon is in time with the event collision, to reject cosmic-ray and beam-halo backgrounds, and to allow direct searches for new, heavy, long-lived neutral particles that decay to photons. The installation and commissioning of all 862 channels were completed in Fall 2004 as part of an upgrade to the Run II version of the detector. Using in situ data, including electrons from
W
→
e
ν
and
Z
→
ee
decays, we measure the energy threshold for a time to be recorded to be
3.8
±
0.3
GeV
(
1.9
±
0.1
GeV
)
in the central (plug) portion of the detector. Similarly, for the central (plug) portion we measure a timing resolution of
600
±
10
ps
(
610
±
10
ps
)
for electrons above 10
GeV (6
GeV). There are very few system pathologies such as recording a time when no energy is deposited, or recording a second, fake time for a single energy deposit.
We examine the discovery potential for SUSY new physics at a
p
p
̄
collider upgrade of Tevatron with
s
= 5.4 TeV and luminosity
L≃4×10
32
cm
−2
s
−1
(the Tripler). We consider the reach for gluinos
(
...g
̃
)
and squarks (
q
̃
) using the experimental signatures with large missing transverse energy
(
E
/
T)
of
jets+
E
/
T
and
1ℓ+
jets+
E
/
T
(where ℓ is an electron or muon) within the framework of minimal supergravity. The Tripler's strongest reach for the gluino is 1060 GeV for the
jets+
E
/
T
channel and 1140 GeV for the
1ℓ+
jets+
E
/
T
channel for 30 fb
−1 of integrated luminosity (approximately two years running time). This is to be compared with the Tevatron where the reach is 440 (460) GeV in the
jets+
E
/
T
channel for 15 (30) fb
−1 of integrated luminosity.
We present the results of a search for anomalous resonant production of tau lepton pairs with large invariant mass, the first such search using the CDF II Detector in Run II of the Tevatron pp ...collider. Such anomalous production could arise from various new physics processes. In a data sample corresponding to 195 pb(-1) of integrated luminosity we predict 2.8+/-0.5 events from standard model background processes and observe 4. We use this result to set limits on the production of heavy scalar and vector particles decaying to tau lepton pairs.
We report a measurement of the difference (D/Acp) between time-integrated-violating asymmetries in D{sup 0} K{sup +}K{sup -} and D{sup 0} {pi}{sup +}{pi}{sup -} decays reconstructed in the full data ...set of proton-antiproton collisions collected by the Collider Detector at Fermilab, corresponding to 9.7 fb{sup -1} of integrated luminosity. The strong decay D*{sup +} D{sup 0}{pi}{sup +} is used to identify the charm meson at production as D{sup 0} or 'D{sup 0}. We measure D/Acp = (-0.62 0.21 /stat 0.10 /syst)%, which differs from zero by 2.7 Gaussian standard deviations. This result supports similar evidence for violation in charm-quark obtained in proton-proton collisions.
We present the results of a search for pair production of a heavy toplike (t') quark decaying to Wq final states using data corresponding to an integrated luminosity of 5.6 fb(-1) collected by the ...CDF II detector in pp collisions at √s=1.96 TeV. We perform parallel searches for t'→Wb and t'→Wq (where q is a generic down-type quark) in events containing a lepton and four or more jets. By performing a fit to the two-dimensional distribution of total transverse energy versus reconstructed t' quark mass, we set upper limits on the t't' production cross section and exclude a standard model fourth-generation t' quark decaying to Wb (Wq) with mass below 358 (340) GeV/c(2) at 95% C.L.
Using Zγ candidate events collected by the CDF detector at the Tevatron Collider, we search for potential anomalous (non-standard-model) couplings between the Z boson and the photon. Zγ couplings ...vanish at tree level and are heavily suppressed at higher orders; hence any evidence of couplings indicates new physics. Measurements are performed using data corresponding to an integrated luminosity of 4.9 fb(-1) in the Z→νν¯ decay channel and 5.1 fb(-1) in the Z→l(+)l(-) (l=μ, e) decay channels. The combination of these measurements provides the most stringent limits to date on Zγ trilinear gauge couplings. Using an energy scale of Λ=1.5 TeV to allow for a direct comparison with previous measurements, we find limits on the CP-conserving parameters that describe Zγ couplings to be |h(3)(γ,Z)|<0.022 and |h(4)(γ,Z)|<0.0009. These results are consistent with standard model predictions.
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