119401854
Charge transfer and charge broadening of GEM structures in high magnetic fields
Abstract We report on the measurements of charge transfer in Gas Electron Multipliers (GEM) structures in high magnetic fields. These were performed in the framework of the R&D work for a Time Projection Chamber at a future Linear Collider. A small test chamber has been installed in the aperture of a superconducting magnet with the GEM structures mounted perpendicular to the B -field direction. The charge transfer is derived from the electrical currents monitored during irradiation with an 55 Fe source. No significant loss of primary ionisation charge is observed, and an improved ion feedback suppression is achieved for high magnetic fields. Additionally, the width of the charge cloud released by individual 55 Fe photons is measured using a finely segmented strip readout after the triple GEM structure. Charge widths between 0.3 and 0.5 mm RMS are observed, which originate from the charge broadening inside the GEM amplification. This charge broadening is only partly suppressed at high magnetic fields.
123036925
The low energy limit of the minimal nonlinear supersymmetric SU(5)-model; production and decay of Higgs particles
Abstract. We consider the Higgssector in the low energy limit of the minimal nonlinear supersymmetric SU(5) model. We estimate radiative corrections to the Higgs masses using the effective potential. Furthermore Higgs boson decays are investigated and differences to the MSSM are discussed.
119399268
Measurement of Boson Self Couplings at LEP and Search for Anomalies
With center of mass energies up to 209 GeV of LEP II, massive W and Z bosons can be produced in pairs and jointly with photons. This allows to study boson-boson couplings. Since the W and Z bosons are unstable and decay into fermions, two- and four-fermion final states, accompanied possibly by photons, play an important role for these measurements. The couplings of the W to other bosons have been measured to be g1Z = 0.990+0.023-0.024, kappa_gamma = 0.896+0.058-0.056, and lambda_gamma = -0.023 +0.025 -0.023. They are in agreement with the Standard Model expectation of g1Z = 1, kappa_gamma = 1, and lambda_gamma = 0. No sign for couplings of three neutral bosons, parametrized by the couplings f_i^V and h_i^V, and for anomalous couplings of four gauge bosons, parametrized by a_0, a_n and a_c has been found.
122519614
The CMS Tracker alignment strategy
CMS Silicon Tracker alignment consists of three key components: survey during Tracker construction, measurements with the Laser Alignment System during operation and track based alignment. Methods and results are explained in detail, with a special focus on track based alignment due to its enormous complexity and numerical challenges.
56244151
Experience with the L3 vertex drift chamber at LEP
The vertex drift chamber of the L3 Experiment at LEP, based on the time expansion principle, was in operation from the start-up of LEP in 1989 until the shutdown of LEP in 2000. The gas mixture used was 80% CO2 and 20% i-C4H10 at a pressure of . We present the design of the chamber, the infrastructure and the performance during the 11 years of operation. The total radiation received on the anode wires was ~10-4 C/cm. No degradation of the anode pulse amplitude, wire efficiencies and resolution was observed for the whole running period.
123173797
Calibration, alignment and tracking performance of the CMS silicon strip tracker
Abstract After its installation in the CMS experiment, the CMS silicon tracker has been commissioned, calibrated and aligned based on several million reconstructed tracks, recorded during extended cosmic ray data-taking in 2008 and 2009. The collision data at 900 GeV and 2.36 TeV which were recorded by the CMS experiment in December 2009 allowed to repeat the calibration measurements and derive compatible results. Calibration results are shown for the silicon strip detector only, whereas alignment and tracking performance are given for the complete CMS tracker, including the silicon pixel system.
54868784
Series tests of fine mesh photomultiplier tubes in magnetic fields of up to 1.2 Tesla
Abstract The new lead/scintillating-fibre calorimeter (“SpaCal”) for the backward region of the H1 experiment at HERA (DESY) is equipped with fine mesh phototubes which operate in a magnetic field close to 1 T. A large sample of these tubes of the types Hamamatsu R5505 and R5506, and Hamamatsu R2490-05, have been tested in fields of up to 1.2T. We have investigated the cathode homogeneity with and without magnetic field, the gain loss under the influence of the magnetic field, and stability with time. For a subsample of tubes, we have performed additional studies on stability with respect to temperature changes, variation of gain as a function of the magnetic field, high voltage discharges, single photo-electron response, and linearity. We finally summarize the experience with these tubes after one year of operation in the experiment.
121444397
New results from NA52 on particle production in Pb+Pb collisions at 158 GeV per nucleon
Abstract We present new results on the centrality and rapidity dependence and on azimuthal anisotropies of particle production in Pb+Pb collisions at 158 GeV per nucleon.
111420431
Ideas on DC-DC Converters for Delivery of Low Voltage and High Currents for the SLHC / ILC Detector Electronics in Magnetic field and Radiation environments
For more efficient power transport to the electronics embedded inside large colliding beam detectors, we explore the feasibility of supplying 48 Volts DC and using local DCDC conversion to 2 V (or lower, depending upon on the lithography of the embedded electronics) using switch mode regulators located very close to the front end electronics. These devices will be exposed to high radiation and high magnetic fields, 10 – 100 Mrads and 2 4 Tesla at the SLHC, and 20 Krads and 6 Tesla at the ILC.
16665734
Top Quark Production and Decay Properties at the Tevatron
The latest results from the CDF and D0 collaborations on the top-quark pair-production cross section and limits on electroweak production are presented. Included are measurements of properties of the top quark such as charge, lifetime, and the decay branching ratio t->Wb. In addition to measurements about the top quark, the selected event samples are used to study the helicity of the W boson and to search for additional exotic quarks (t') and resonances in the ttbar invariant mass spectrum.
119389130
Electroweak corrections to e+ e- -> nu anti-nu H and e+ e- -> t anti-t H
The most interesting Higgs-production processes at future e+ e- colliders belong to the process class e+ e- ->f anti-f H. We study the full O(alpha) corrections to this reaction in the Standard Model for neutrinos and top quarks in the final state. Leading higher-order corrections from initial-state radiation and QCD corrections are also taken into account. Although cancellations between the different kinds of corrections occur, the full corrections are of the order of +/-10% and thus important ingredients in the theoretical predictions for future e+ e- colliders.