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The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric Standard Model (MSSM). The data of the four collaborations are statistically combined and examined for their consistency with the background hypothesis and with a possible Higgs boson signal. The combined LEP data show no significant excess of events which would indicate the production of Higgs bosons. The search results are used to set upper bounds on the cross-sections of various Higgs-like event topologies. The results are interpreted within the MSSM in a number of "benchmark" models, including CP-conserving and CP-violating scenarios. These interpretations lead in all cases to large exclusions in the MSSM parameter space. Absolute limits are set on the parameter tan β and, in some scenarios, on the masses of neutral Higgs bosons.

A precision measurement by AMS of the positron fraction in primary cosmic rays in the energy range from 0.5 to 500 GeV based on 10.9 million positron and electron events is presented. This measurement extends the energy range of our previous observation and increases its precision. The new results show, for the first time, that above ∼200 GeV the positron fraction no longer exhibits an increase with energy. 3Over the last two decades, there has been a strong interest in the cosmic ray positron fraction in both particle physics and astrophysics [1]. The positron fraction is defined as the ratio of the positron flux to the combined flux of positrons and electrons. The first results from the Alpha Magnetic Spectrometer (AMS) on the positron fraction were reported in [2]. They generated widespread interest [3]. In this Letter we report new results based on all the data collected during 30 months of AMS operations on the International Space Station (ISS), from 19 May 2011 to 26 November 2013. Due to the excellent and steady performance of the detector, and an increase of the data sample by a factor of 1.7, the measurement of the positron fraction is extended up to 500 GeV with improved precision.AMS detector.-The layout of the AMS-02 detector [4] is shown in Fig. 1. It consists of 9 planes of precision silicon tracker with two outer planes, 1 and 9, and the inner tracker, planes 2-8 [5]; a transition radiation detector, TRD [6]; four planes of time of flight counters, TOF [7]; a permanent magnet [8]; an array of anti-coincidence counters, ACC [9], inside the magnet bore; a ring imagingČerenkov detector, RICH [10]; and an electromagnetic calorimeter, ECAL [11]. The figure also shows a high energy positron of 369 GeV recorded by AMS. AMS operates without interruption on the ISS and is monitored continuously from the ground.The timing, location and attitude of AMS are determined by a combination of GPS units affixed to AMS and to the ISS. The AMS coordinate system is concentric with the center of the magnet. The x axis is parallel to the main component of the magnetic field and the z axis points vertically. The (y-z ) plane is the bending plane. The maximum detectable rigidity over tracker planes 1-9, a lever arm of 3 m, is ∼2 TV. Detector performance, described in detail in [2,4], is steady over time.Three main detectors provide clean and redundant identification of positrons and electrons with independent suppression of the proton background. These are the TRD (above the magnet), the ECAL (below the magnet) and the tracker. The TRD and the ECAL are separated by the magnet and the tracker. This ensures that most of the secondary particles produced in the TRD and in the upper TOF planes are swept away and do not enter into the ECAL. Events with large angle scattering are also rejected by a quality cut on the measurement of the trajectory using the tracker. The matching of the ECAL energy, E, and the momentum measured with the tracker, p, greatly improves the proton rejection.To differentiate between e ± and prot...

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Test beam measurements at the test beam facilities of DESY have been conducted to characterise the performance of the EUDET-type beam telescopes originally developed within the EUDET project. The beam telescopes are equipped with six sensor planes using MIMOSA 26 monolithic active pixel devices. A programmable Trigger Logic Unit provides trigger logic and time stamp information on particle passage. Both data acquisition framework and offline reconstruction software packages are available. User devices are easily integrable into the data acquisition framework via predefined interfaces. The biased residual distribution is studied as a function of the beam energy, plane spacing and sensor threshold. Its standard deviation at the two centre pixel planes using all six planes for tracking in a 6 GeV electron/positron-beam is measured to be (2.88 ± 0.08) μm. Iterative track fits using the formalism of General Broken Lines are performed to estimate the intrinsic resolution of the individual pixel planes. The mean intrinsic resolution over the six sensors used is found to be (3.24 ± 0.09) μm. With a 5 GeV electron/positron beam, the track resolution halfway between the two inner pixel planes using an equidistant plane spacing of 20 mm is estimated to (1.83 ± 0.03) μm assuming the measured intrinsic resolution. Towards lower beam energies the track resolution deteriorates due to increasing multiple scattering. Threshold studies show an optimal working point of the MIMOSA 26 sensors at a sensor threshold of between five and six times their RMS noise. Measurements at different plane spacings are used to calibrate the amount of multiple scattering in the material traversed and allow for corrections to the predicted angular scattering for electron beams.