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.
67766701
The CMS alignment challenge
The CMS tracking detectors are of unprecedented complexity: 66 million pixel cells distributed over 1440 modules in the Pixel Tracker; 9.6 million readout channels in 15 148 silicon strip modules in the Strip Tracker; 250 drift, 468 cathode strip, and 360+252 resistive plate chambers in the Muon System. All of them need to be aligned to a precision better than their intrinsic resolution in order not to degrade tracking performance. Besides being a numerical and time-intensive challenge, it is a difficult task to constrain all the possible degrees of freedom, to properly handle the large amount of data, and to face the modeling imperfections and subtle systematics the data will show once the detector is turned on. We briefly introduce the topic to set up the scene for the following articles about CMS alignment, in which more results will be presented.
118621343
Validation of Kalman Filter alignment algorithm with cosmic-ray data using a CMS silicon strip tracker endcap
A Kalman Filter alignment algorithm has been applied to cosmic-ray data. We discuss the alignment algorithm and an experiment-independent implementation including outlier rejection and treatment of weakly determined parameters. Using this implementation, the algorithm has been applied to data recorded with one CMS silicon tracker endcap. Results are compared to both photogrammetry measurements and data obtained from a dedicated hardware alignment system, and good agreement is observed.
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.
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.
120842226
GALACTIC MODEL UNCERTAINTIES IN INDIRECT DARK MATTER SEARCH
If Dark Matter (DM) particles are a thermal relic from the early universe, they are expected to annihilate into quarks and leptons in order to reduce the number density with respect to the number of photons. The annihilation into quarks is expected to be dominant which may lead to a significant excess in gamma rays, antiprotons and positrons, as discussed in recent reviews. An excess in gamma rays above the background from interactions between cosmic rays (CR) and the interstellar medium has indeed been observed by the EGRET gamma ray spectrometer on board of the NASA Compton Gamma Ray Observatory, which has been taken data in space between the years 1991 and 2000. This excess shows all the properties of the annihilation of a 60 GeV Weakly Interacting Massive Particle (WIMP), as discussed by de Boer et al. . Especially the distribution of the excess could be used to predict the shape of the rotation curve of the Galaxy, thus proving that the excess is a tracer of Dark Matter. The main assumption in this analysis was that the shape of the CR background is the same everywhere in the Galaxy, as is expected from the fact that the energy loss time for protons is large compared with the diffusion time. The interaction of CR protons with the interstellar gas is the major source of background for gamma ray energies in the few GeV range. The CR electrons have large energy losses by inverse Compton scattering and Bremsstrahlung, which are additional sources of gamma rays. It is the main purpose of the present note to study the uncertainties in the shape of the CR background and the corresponding uncertainties in the gamma ray spectra. This was done with the publicly available GALPROP propagation model after modifying it to include DMA. In addition the effects of the inhomogeneous local solar neighborhood were studied. Furthermore anisotropic diffusion, expected in spiral galaxies with strong anisotropic magnetic fields, was studied which increases the uncertainties of charged secondary particles by a wide margin. The latter is relevant, since in a recent paper Bergstrom et al. claimed that the flux of antiprotons excludes the DMA interpretation of the EGRET excess. This conclusion was based on their isotropic propagation model in the DarkSusy program.
11389899
Centrality dependence of K+ produced in Pb+Pb collisions at 158 GeV per nucleon
The NA52 collaboration searches for a discontinuous behaviour of charged kaons produced in Pb+Pb collisions at 158 A GeV as a function of the impact parameter, which could reveal a hadron to quark-gluon plasma (QGP) phase transition. The K+ yield is found to grow proportional to the number of participating ('wounded') nucleons N, above N=100. Previous NA52 data agree with the above finding and show a discontinuous behaviour in the kaon centrality dependence near N=100, marking the onset of strangeness enhancement -over e.g. p+A data at the same \sqrt{s}- in a chemically equilibrated phase.
110779087
The SVX4 integrated circuit
Abstract A first prototype of the SVX4 readout IC with enclosed transistor layout for radiation tolerance has been fabricated in a commercial 0.25 μm bulk CMOS process. The SVX4 is intended to instrument the CDF and D0 Run IIB silicon strip detector upgrades at Fermilab. The design and test results are discussed.
14164208
A prototype liquid Argon Time Projection Chamber for the study of UV laser multi-photonic ionization
This paper describes the design, realization and operation of a prototype liquid Argon Time Projection Chamber (LAr TPC) detector dedicated to the development of a novel online monitoring and calibration system exploiting UV laser beams. In particular, the system is intended to measure the lifetime of the primary ionization in LAr, in turn related to the LAr purity level. This technique could be exploited by present and next generation large mass LAr TPCs for which monitoring of the performance and calibration play an important role. Results from the first measurements are presented together with some considerations and outlook.
14039647
JET SHAPES AND DETERMINATIONS OF s FROM HADRONIC FINAL STATES IN DEEP INELASTIC SCATTERING AT HERA
Recent results from the study of hadronic nal states in deep inelastic scattering at HERA are reviewed. Jet shapes from neutral and charged current interactions at HERA are compared to those from e + e ? annihilation and p p collisions. The (2+1) jet event rate distributions R2+1(Q 2) and y2 are measured using the modiied JADE jet algorithm. The value of the strong coupling constant s is determined from a comparison with QCD predictions in next{ to{leading order. An analysis of event shape distributions in terms of next{to{leading order QCD calculations and power corrections is presented.