arXiv subjects

Frank Würthwein

Publications and source records attributed to Frank Würthwein.

44 records · Page 3Linked to original sources

arXiv2017

Data Access for LIGO on the OSG

During 2015 and 2016, the Laser Interferometer Gravitational-Wave Observatory (LIGO) conducted a three-month observing campaign. These observations delivered the first direct detection of gravitational waves from binary black hole mergers. To search for these signals, the LIGO Scientific Collaboration uses the PyCBC search pipeline. To deliver science results in a timely manner, LIGO collaborated with the Open Science Grid (OSG) to distribute the required computation across a series of dedicated, opportunistic, and allocated resources. To deliver the petabytes necessary for such a large-scale computation, our team deployed a distributed data access infrastructure based on the XRootD server suite and the CernVM File System (CVMFS). This data access strategy grew from simply accessing remote storage to a POSIX-based interface underpinned by distributed, secure caches across the OSG.

cs.DC↗

arXiv2016

Kalman-Filter-Based Particle Tracking on Parallel Architectures at Hadron Colliders

Power density constraints are limiting the performance improvements of modern CPUs. To address this we have seen the introduction of lower-power, multi-core processors such as GPGPU, ARM and Intel MIC. To stay within the power density limits but still obtain Moore's Law performance/price gains, it will be necessary to parallelize algorithms to exploit larger numbers of lightweight cores and specialized functions like large vector units. Track finding and fitting is one of the most computationally challenging problems for event reconstruction in particle physics. At the High-Luminosity Large Hadron Collider (HL-LHC), for example, this will be by far the dominant problem. The need for greater parallelism has driven investigations of very different track finding techniques such as Cellular Automata or Hough Transforms. The most common track finding techniques in use today, however, are those based on the Kalman Filter. Significant experience has been accumulated with these techniques on real tracking detector systems, both in the trigger and offline. They are known to provide high physics performance, are robust, and are in use today at the LHC. We report on porting these algorithms to new parallel architectures. Our previous investigations showed that, using optimized data structures, track fitting with Kalman Filter can achieve large speedups both with Intel Xeon and Xeon Phi. We report here our progress towards an end-to-end track reconstruction algorithm fully exploiting vectorization and parallelization techniques in a realistic experimental environment.

physics.ins-det↗

arXiv2015

Any Data, Any Time, Anywhere: Global Data Access for Science

Data access is key to science driven by distributed high-throughput computing (DHTC), an essential technology for many major research projects such as High Energy Physics (HEP) experiments. However, achieving efficient data access becomes quite difficult when many independent storage sites are involved because users are burdened with learning the intricacies of accessing each system and keeping careful track of data location. We present an alternate approach: the Any Data, Any Time, Anywhere infrastructure. Combining several existing software products, AAA presents a global, unified view of storage systems - a "data federation," a global filesystem for software delivery, and a workflow management system. We present how one HEP experiment, the Compact Muon Solenoid (CMS), is utilizing the AAA infrastructure and some simple performance metrics.

physics.comp-ph↗

arXiv2015

Kalman Filter Tracking on Parallel Architectures

Power density constraints are limiting the performance improvements of modern CPUs. To address this we have seen the introduction of lower-power, multi-core processors, but the future will be even more exciting. In order to stay within the power density limits but still obtain Moore's Law performance/price gains, it will be necessary to parallelize algorithms to exploit larger numbers of lightweight cores and specialized functions like large vector units. Example technologies today include Intel's Xeon Phi and GPGPUs. Track finding and fitting is one of the most computationally challenging problems for event reconstruction in particle physics. At the High Luminosity LHC, for example, this will be by far the dominant problem. The need for greater parallelism has driven investigations of very different track finding techniques including Cellular Automata or returning to Hough Transform. The most common track finding techniques in use today are however those based on the Kalman Filter. Significant experience has been accumulated with these techniques on real tracking detector systems, both in the trigger and offline. They are known to provide high physics performance, are robust and are exactly those being used today for the design of the tracking system for HL-LHC. Our previous investigations showed that, using optimized data structures, track fitting with Kalman Filter can achieve large speedup both with Intel Xeon and Xeon Phi. We report here our further progress towards an end-to-end track reconstruction algorithm fully exploiting vectorization and parallelization techniques in a realistic simulation setup.

physics.ins-det↗

arXiv1999

Determination of the Phase of Vub from Charmless Hadronic B Decay Rates

We perform a model dependent fit to recent data on charmless hadronic B decays and determine $γ$, the phase of $V^*_{ub}$. We find $γ= 114^{+25}_{-21}$ degrees, which disfavors the often quoted $γ\sim 60^\circ$ at the two standard deviation level. We also fit for the form factors $F_0^{Bπ}$ and $A_0^{Bρ}$, and the strange-quark mass. They are consistent with theoretical expectations, although $m_s$ is somewhat low. Such agreement and the good $χ^2$ for the fit may be interpreted as a confirmation of the adequacy of our model assumptions.

hep-ex↗

arXiv1999

Charmless Hadronic B Decays at CLEO

The CLEO collaboration has studied two-body charmless hadronic decays of $B$ mesons into final states containing two pseudo-scalar mesons, or a pseudo-scalar and a vector meson. We summarize and discuss results presented during the winter/spring 1999 conference season, and provide a brief outlook towards future attractions to come. In particular, CLEO presented preliminary results on the decays $B^\pm \to π^\pmρ^0$ ($Br(B^\pm \to π^\pmρ^0) = (1.5 \pm 0.5 \pm 0.4)\times 10^{-5}$), $B\to π^\pmρ^\mp$ ($Br(B\to π^\pmρ^\mp)=(3.5^{+1.1}_{-1.0}\pm 0.5)\times 10^{-5}$), $B\to π^\pm K^{\star\mp}$ ($Br(B\to π^\pm K^{\star\mp}) = (2.2^{+0.8+0.4}_{-0.6-0.5})\times 10^{-5}$), and $B^\pm \to K^\pm π^0$ ($Br(B^\pm \to K^\pm π^0) = (1.5 \pm 0.4 \pm 0.3) \times 10^{-5}$) at DPF99, APS99, APS99, and ICHEP98 respectively. None of these decays had been observed previously. The first two of these constitute the first observation of hadronic $b\to u$ transitions. In addition, CLEO presented preliminary updates on a large number of previously published branching fractions and upper limits.

hep-ex↗

arXiv1997

Measuring Arg($V_{ub}$) in $B\to Kπ$

It has previously been shown that a measurement of Arg$(V_{ub})=γ$ can be obtained from a triangle construction using ${\cal B}(B^0\to K^+π^-)$, ${\cal B}(\bar{B^0}\to K^-π^+)$, ${\cal B}(B^\pm\to K^0_sπ^\pm)$, and ${\cal B}(B^\pm\to π^\pmπ^0)$. We evaluate experimental as well as theoretical uncertainties in this measurement. We find that a measurement of $γ$ with the next generation of B-factories (BaBar, BELLE, CLEO III) is statistics rather than theory limited if soft rescattering effects are small.

hep-ph↗

arXiv1997

B Decays to Two Charmless Pseudoscalar Mesons at CLEO

Using 3.3 Million $B\bar B$ pairs accumulated with the CLEO detector CLEO has measured ${\cal B}(B^0\to K^+π^-) = (1.5^{+ 0.5}_{-0.4}\pm 0.1\pm 0.1)\times 10^{-5}$, ${\cal B}(B^+\to K^0π^+) = (2.3^{+1.1}_{-1.0}\pm 0.2\pm 0.2)\times 10^{-5}$, and ${\cal B}(B^+\to η^{'}K^+) = (7.8^{+ 2.7}_{-2.2}\pm 1.0)\times 10^{-5}$. These constitute the first observations of exclusive $B$\ decays to charmless hadronic final states. Furthermore, a measurement of ${\cal B}(B^+\to h^+π^0) = (1.6^{+ 0.6 +0.3}_{-0.5 -0.2}\pm 0.1)\times 10^{-5}$, as well as upper limits on various other $B$ decays to two charmless pseudoscalar mesons are presented. In particular, an upper limit of ${\cal B}(B^0\to π^+π^-) < 1.5\times 10^{-5}$ @ 90%C.L. is placed. All of these results are still preliminary, and averaging over charge conjugate modes is always implied.

hep-ex↗