6,207 research outputs found
Rare decays of heavy flavor at the Tevatron
In this report I review recent results in the field of rare decays at the
Tevatron CDF II and D0 experiments. The presentation is focused on rare decays
of charm and bottom mesons with two muons in the final state. This includes
improvements over the previously available limits on the following branching
ratios: , B(B_s^0 \to \phi
\mu^+ \mu^-)< 3.2\times 10^{-6}B(B_s^0 \to \mu^+ \mu^-)< 1 \times 10^{-7}B(B_d^0)< 3 \times 10{-8}D_s^+ \to \phi \pi^+ \to \mu^+ \mu^-
\pi^+D^+ \to \phi \pi^+ \to \mu^+ \mu^- \pi^+B(D^+ \to \phi \pi^+ \to \mu^+ \mu^- \pi^+)=(1.75 \pm0.7 \pm0.5)
\times 10^{-6}$.Comment: in proceedings of Hadron Collider Physics Symposium, Duke University,
NC, May 22-26 200
B-physics: new states, rare decays and branching ratios in CDF
We present results and prospects for searches for rare B and D meson decays
with final state dimuons, including B_s\to\mu\mu, B_d\to\mu\mu, and D\to\mu\mu.
Upper limits on the branching fractions are compared to previous CDF
measurements, recent results from the B factories and theoretical expectations.
We also report on new measurements of production and decay properties of the
X(3872) particle, discovered in 2003 by the Belle Collaboration. New results on
the measurement of the relative branching fraction for the Cabibbo suppressed
decay B^+\to J/\psi\pi^+ Br(B^+\to J/\psi\pi^+)/Br(B^+\to J/\psi K^+) are
presented too. The presented results are based on the analyses of 70 to 220
pb^-1 of data collected by the CDF II detector in p\bar p collisions at
\sqrt{s} = 1.96 GeV at Fermilab Tevatron.Comment: Presented at the 6th International Conference on Hyperons, Charm &
Beauty Hadrons (BEACH04), Chicago, IL, June 27 - July 03 2004. 5 page
Parallelized and Vectorized Tracking Using Kalman Filters with CMS Detector Geometry and Events
The High-Luminosity Large Hadron Collider at CERN will be characterized by
greater pileup of events and higher occupancy, making the track reconstruction
even more computationally demanding. Existing algorithms at the LHC are based
on Kalman filter techniques with proven excellent physics performance under a
variety of conditions. Starting in 2014, we have been developing
Kalman-filter-based methods for track finding and fitting adapted for many-core
SIMD processors that are becoming dominant in high-performance systems.
This paper summarizes the latest extensions to our software that allow it to
run on the realistic CMS-2017 tracker geometry using CMSSW-generated events,
including pileup. The reconstructed tracks can be validated against either the
CMSSW simulation that generated the hits, or the CMSSW reconstruction of the
tracks. In general, the code's computational performance has continued to
improve while the above capabilities were being added. We demonstrate that the
present Kalman filter implementation is able to reconstruct events with
comparable physics performance to CMSSW, while providing generally better
computational performance. Further plans for advancing the software are
discussed
Prospect for Searches for Gluinos and Squarks at a Tevatron Tripler
We examine the discovery potential for SUSY new physics at a p{\bar p}
collider upgrade of Tevatron with \sqrt s = 5.4 TeV and luminosity L ~= 4\times
10^{32} cm^{-2}s^{-1} (the Tripler). We consider the reach for gluinos and
squarks using the experimental signatures with large missing transverse energy
(\met) of jets + \met and 1l + jets + \met (where l=electron or muon) within
the framework of minimal supergravity. The Tripler's strongest reach for the
gluino is 1060 GeV for the jets + \met channel and 1140 GeV for the 1l + jets +
\met 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 + \met channel for 15(30) fb^{-1} of integrated
luminosity.Comment: 17 pages, latex, 7 figure
Performance of a Large-Area GEM Detector Prototype for the Upgrade of the CMS Muon Endcap System
Gas Electron Multiplier (GEM) technology is being considered for the forward
muon upgrade of the CMS experiment in Phase 2 of the CERN LHC. Its first
implementation is planned for the GE1/1 system in the region of the muon endcap mainly to control muon level-1 trigger rates
after the second long LHC shutdown. A GE1/1 triple-GEM detector is read out by
3,072 radial strips with 455 rad pitch arranged in eight -sectors.
We assembled a full-size GE1/1 prototype of 1m length at Florida Tech and
tested it in 20-120 GeV hadron beams at Fermilab using Ar/CO 70:30 and
the RD51 scalable readout system. Four small GEM detectors with 2-D readout and
an average measured azimuthal resolution of 36 rad provided precise
reference tracks. Construction of this largest GEM detector built to-date is
described. Strip cluster parameters, detection efficiency, and spatial
resolution are studied with position and high voltage scans. The plateau
detection efficiency is [97.1 0.2 (stat)]\%. The azimuthal resolution is
found to be [123.5 1.6 (stat)] rad when operating in the center of
the efficiency plateau and using full pulse height information. The resolution
can be slightly improved by 10 rad when correcting for the bias due
to discrete readout strips. The CMS upgrade design calls for readout
electronics with binary hit output. When strip clusters are formed
correspondingly without charge-weighting and with fixed hit thresholds, a
position resolution of [136.8 2.5 stat] rad is measured, consistent
with the expected resolution of strip-pitch/ = 131.3 rad. Other
-sectors of the detector show similar response and performance.Comment: 8 pages, 32 figures, submitted to Proc. 2014 IEEE Nucl. Sci.
Symposium, Seattle, WA, reference adde
Reconstruction of Charged Particle Tracks in Realistic Detector Geometry Using a Vectorized and Parallelized Kalman Filter Algorithm
One of the most computationally challenging problems expected for the
High-Luminosity Large Hadron Collider (HL-LHC) is finding and fitting particle
tracks during event reconstruction. Algorithms used at the LHC today rely on
Kalman filtering, which builds physical trajectories incrementally while
incorporating material effects and error estimation. Recognizing the need for
faster computational throughput, we have adapted Kalman-filter-based methods
for highly parallel, many-core SIMD and SIMT architectures that are now
prevalent in high-performance hardware. Previously we observed significant
parallel speedups, with physics performance comparable to CMS standard
tracking, on Intel Xeon, Intel Xeon Phi, and (to a limited extent) NVIDIA GPUs.
While early tests were based on artificial events occurring inside an idealized
barrel detector, we showed subsequently that our mkFit software builds tracks
successfully from complex simulated events (including detector pileup)
occurring inside a geometrically accurate representation of the CMS-2017
tracker. Here, we report on advances in both the computational and physics
performance of mkFit, as well as progress toward integration with CMS
production software. Recently we have improved the overall efficiency of the
algorithm by preserving short track candidates at a relatively early stage
rather than attempting to extend them over many layers. Moreover, mkFit
formerly produced an excess of duplicate tracks; these are now explicitly
removed in an additional processing step. We demonstrate that with these
enhancements, mkFit becomes a suitable choice for the first iteration of CMS
tracking, and eventually for later iterations as well. We plan to test this
capability in the CMS High Level Trigger during Run 3 of the LHC, with an
ultimate goal of using it in both the CMS HLT and offline reconstruction for
the HL-LHC CMS tracker
A novel application of Fiber Bragg Grating (FBG) sensors in MPGD
We present a novel application of Fiber Bragg Grating (FBG) sensors in the
construction and characterisation of Micro Pattern Gaseous Detector (MPGD),
with particular attention to the realisation of the largest triple (Gas
electron Multiplier) GEM chambers so far operated, the GE1/1 chambers of the
CMS experiment at LHC. The GE1/1 CMS project consists of 144 GEM chambers of
about 0.5 m2 active area each, employing three GEM foils per chamber, to be
installed in the forward region of the CMS endcap during the long shutdown of
LHC in 2108-2019. The large active area of each GE1/1 chamber consists of GEM
foils that are mechanically stretched in order to secure their flatness and the
consequent uniform performance of the GE1/1 chamber across its whole active
surface. So far FBGs have been used in high energy physics mainly as high
precision positioning and re-positioning sensors and as low cost, easy to
mount, low space consuming temperature sensors. FBGs are also commonly used for
very precise strain measurements in material studies. In this work we present a
novel use of FBGs as flatness and mechanical tensioning sensors applied to the
wide GEM foils of the GE1/1 chambers. A network of FBG sensors have been used
to determine the optimal mechanical tension applied and to characterise the
mechanical tension that should be applied to the foils. We discuss the results
of the test done on a full-sized GE1/1 final prototype, the studies done to
fully characterise the GEM material, how this information was used to define a
standard assembly procedure and possible future developments.Comment: 4 pages, 4 figures, presented by Luigi Benussi at MPGD 2015 (Trieste,
Italy). arXiv admin note: text overlap with arXiv:1512.0848
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