Charm Physics at CDF II

The CDF II detector has the capability of triggering on displaced tracks. Because of this ability, CDF II has accrued large samples of charmed meson decays to fully hadronic final states in 64 pb^-1 of ppbar collision data gathered at sqrt(s) = 1.96 TeV. Using initial Run II data samples, the production cross sections for J/psi, D0, D+, D*+ and Ds+ mesons have been measured. Ratios of branching ratios for Cabibbo suppressed final states and CP asymmetries in D0 meson decays have been studied. A measurement of the mass difference m(Ds+) - m(D+) has been done, and a limit for the branching fraction of the FCNC D0 -> mu+ mu- decays has been set.Comment: Presented at 17th Les Rencontres de Physique de la Vallee d'Aoste: Results and Perspectives in Particle Physics, La Thuile, Aosta Valley, Italy, 9-15 Mar 200

A Large Solid Angle Study of Pion Absorption on He3

Measurements have been made of pi+ absorption on He3 at T_pi+ = 118, 162, and 239 MeV using the Large Acceptance Detector System (LADS). The nearly 4pi solid angle coverage of this detector minimizes uncertainties associated with extrapolations over unmeasured regions of phase space. The total absorption cross section is reported. In addition, the total cross section is divided into components in which only two or all three nucleons play a significant role in the process. These are the first direct measurements of the total and three nucleon absorption cross sections.Comment: 8 pages, LaTeX. 3 figures, anonymous ftp MITLNS.MIT.EDU, cd LADS. Submitted to PRL. PSI-PR-94-11 (Paul Scherrer Institute) and LNS 94-56 (MIT Lab. for Nucl. Sci.

The CMS Modular Track Finder boards, MTF6 and MTF7

To accommodate the increase in energy and luminosity of the upgraded LHC, the CMS Endcap Muon Level 1 Trigger system has to be significantly modified. To provide the best track reconstruction, the Trigger system must now import all available trigger primitives generated by Cathode Strip Chambers and by other regional subsystems, such as Resistive Plate Chambers. In addition to massive input bandwidth, this also requires a significant increase in logic and memory resources. To satisfy these requirements, a new Sector Processor unit for muon track finding is being designed. This unit follows the micro-TCA standard recently adopted by CMS. It consists of three modules. The Core Logic module houses the large FPGA that contains the processing logic and multi-gigabit serial links for data exchange. The Optical module contains optical receivers and transmitters; it communicates with the Core Logic module via a custom backplane section. The Look-Up Table module contains a large amount of low-latency memory that is used to assign the final transverse momentum of the muon candidate tracks. The name of the unit — Modular Track Finder — reflects the modular approach used in the design. Presented here are the details of the hardware design of the prototype unit based on Xilinx's Virtex-6 FPGA family, MTF6, as well as results of the conducted tests. Also presented are plans for the pre-production prototype based on the Virtex-7 FPGA family, MTF7

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

Development and performance of Triple-GEM detectors for the upgrade of the muon system of the CMS experiment

The CMS Collaboration is evaluating GEM detectors for the upgrade of the muon system. This contribution will focus on the R&D performed on chambers design features and will discuss the performance of the upgraded detector

Overview of large area triple-GEM detectors for the CMS forward muon upgrade

In order to cope with the harsh environment expected from the high luminosity LHC, the CMS forward muon system requires an upgrade. The two main challenges expected in this environment are an increase in the trigger rate and increased background radiation leading to a potential degradation of the particle ID performance. Additionally, upgrades to other subdetectors of CMS allow for extended coverage for particle tracking, and adding muon system coverage to this region will further enhance the performance of CMS

Design of a constant fraction discriminator for the VFAT3 front-end ASIC of the CMS GEM detector

In this work the design of a constant fraction discriminator (CFD) to be used in the VFAT3 chip for the read-out of the triple-GEM detectors of the CMS experiment, is described. A prototype chip containing 8 CFDs was implemented using 130 nm CMOS technology and test results are shown. © CERN 2016

Search for the Supersymmetric Partner of the Top-Quark in ppˉp \bar{p} Collisions at s=1.8TeV\sqrt{s} = 1.8 {\rm TeV}

We report on a search for the supersymmetric partner of the top quark (stop) produced in $t \bar{t}$ events using $110 {\rm pb}^{-1}$ of $p \bar{p}$ collisions at $\sqrt{s} = 1.8 {\rm TeV}$ recorded with the Collider Detector at Fermilab. In the case of a light stop squark, the decay of the top quark into stop plus the lightest supersymmetric particle (LSP) could have a significant branching ratio. The observed events are consistent with Standard Model $t \bar{t}$ production and decay. Hence, we set limits on the branching ratio of the top quark decaying into stop plus LSP, excluding branching ratios above 45% for a LSP mass up to 40 {\rm GeV/c}$^{2}$.Comment: 11 pages, 4 figure

Combined search for the standard model Higgs boson decaying to a bb pair using the full CDF data set

We combine the results of searches for the standard model Higgs boson based on the full CDF Run II data set obtained from sqrt(s) = 1.96 TeV p-pbar collisions at the Fermilab Tevatron corresponding to an integrated luminosity of 9.45/fb. The searches are conducted for Higgs bosons that are produced in association with a W or Z boson, have masses in the range 90-150 GeV/c^2, and decay into bb pairs. An excess of data is present that is inconsistent with the background prediction at the level of 2.5 standard deviations (the most significant local excess is 2.7 standard deviations).Comment: To be published in Phys. Rev. Lett (v2 contains minor updates based on comments from PRL