121783594
Strong interaction effects in kaonic atoms
Abstract X-rays produced by kaons stopping in targets of S, Co, Ni, Ag and Cd have been observed. The shifts and widths of the last observed mesic X-ray due to the effects of the strong interaction have been measured. In addition, the relative yield of the sulphur K − n = 4 → 3 transition has been measured.
120799482
Charge collection and charge sharing in heavily irradiated n-side read-out silicon microstrip detectors
Abstract Hadron radiation damage of n-bulk silicon detectors leads to a change in the effective space charge from positive to negative. This effect is called type inversion. Type inversion occurs after exposure to a fluence of a few 10 13 proton cm −2 and is characterized by migration of the diode junction to the n + implanted side (n-side) of the detector. After inversion the charge collection efficiency (CCE) of segmented detectors at low voltage is higher when the n-side, rather than the p-side, is read out. A p-side read out (p–in–n) and an n-side read out (n–in–n) strip detector with identical strip geometry and a wafer thickness of 200 μm were simultaneously and inhomogenously irradiated to a maximum fluence of 7×10 14 proton cm −2 with 24 GeV  c −1 protons. A comparison of the CCE at very high irradiation doses is shown with these two read out geometries. The inhomogeneous irradiation induces an inhomogenous distribution of the effective space charge with a transverse component of the electric field that could in principle affect the resolution properties of the microstrip detector. The inter-strip charge sharing properties, as a function of dose, for the n–in–n detector have been measured. No systematic distortion of the reconstructed cluster position was detected within the limits of the measurement accuracy. The detectors were manufactured using oxygen enriched silicon substrates to limit the degradation of the full depletion voltage under charged hadron irradiation. The measured CCE confirms that the use of oxygenated n–in–n detectors is viable up to fluences of 7×10 14 proton cm −2 .
119337869
Accurate three-dimensional simulation of straw chambers using slow, medium and fast gas mixtures
Abstract The positional accuracy and efficiency of straw chambers using gas mixtures of carbon dioxide-isobutane (80:20), argon-isobutane-isopropanol (50:49:1) and argon-carbon tetrafluoride (90:10) are calculated as a function of drift distance with a precision of 1%. Large attachment effects on the resolution and efficiency are predicted for carbon-tetrafluoride-based gas mixtures which are important for SSC applications. The varying electric field in straw chambers leads to nonlinear drift time-distance relationships. The accurate prediction of this relationship to about 1% should allow the track fitting analysis to proceed with more tightly constrained parameters.
56301921
High rate behavior and discharge limits in micro-pattern detectors
Abstract We present and discuss a set of systematic measurements, carried out with gaseous proportional micro-pattern detectors, in order to assess their maximum gain when irradiated with high-rate soft X-rays and heavily ionizing alpha particles. The inventory of detectors tested includes: micro-strips, micromegas, micro-dot, gas electron multiplier, CAT (compteur a trous), trench (or groove), micro-CAT (or WELL) detectors, as well as systems with two elements of gaseous amplification in cascade. We confirm the general trend of all single-stage detectors to follow Raether's criterion, i.e. a spontaneous transition from avalanche to streamer, followed by a discharge, when the avalanche size reaches a value of a few 10 7 ; a noticeable exception is the micro-dot counter holding more than 10 8 . In multiple structures, where the gain is shared between two devices in cascade, the maximum overall gain under irradiation is increased by at least one order of magnitude; we speculate this to be a consequence of a voltage dependence of Raether's limit, larger for low operating potentials. Our conclusion is that only multiple devices can guarantee a sufficient margin of reliability for operation in harsh LHC running conditions.
119249031
Measurement of the atmospheric muon flux with the NEMO Phase-1 detector
Abstract The NEMO Collaboration installed and operated an underwater detector including prototypes of the critical elements of a possible underwater km 3 neutrino telescope: a four-floor tower (called Mini-Tower) and a Junction Box. The detector was developed to test some of the main systems of the km 3 detector, including the data transmission, the power distribution, the timing calibration and the acoustic positioning systems as well as to verify the capabilities of a single tridimensional detection structure to reconstruct muon tracks. We present results of the analysis of the data collected with the NEMO Mini-Tower. The position of photomultiplier tubes (PMTs) is determined through the acoustic position system. Signals detected with PMTs are used to reconstruct the tracks of atmospheric muons. The angular distribution of atmospheric muons was measured and results compared to Monte Carlo simulations.
36324839
Searches for clustering in the time integrated skymap of the ANTARES neutrino telescope
This paper reports a search for spatial clustering of the arrival directions of high energy muon neutrinos detected by the ANTARES neutrino telescope. An improved two-point correlation method is used to study the autocorrelation of 3058 neutrino candidate events as well as cross-correlations with other classes of astrophysical objects: sources of high energy gamma rays, massive black holes and nearby galaxies. No significant deviations from the isotropic distribution of arrival directions expected from atmospheric backgrounds are observed.
118473267
A parameterisation of the flux and energy spectrum of single and multiple muons in the deep water or ice
Abstract Atmospheric muons play an important role in underwater/ice neutrino detectors. A parameterisation of the flux of single and multiple muon events, of their lateral distribution and energy spectrum is presented. The kinematics parameters were modelled starting from a full Monte Carlo simulation of the interaction of primary cosmic rays with atmospheric nuclei. The parametric formulas are valid for a vertical depth of 1.5–5 km w.e. and up to 85 ∘ for the zenith angle, and can be used as input for a fast simulation of atmospheric muons in underwater/ice detectors.
118018120
First results on dark matter annihilation in the Sun using the ANTARES neutrino telescope
A search for high-energy neutrinos coming from the direction of the Sun has been performed using the data recorded by the ANTARES neutrino telescope during 2007 and 2008. The neutrino selection criteria have been chosen to maximize the selection of possible signals produced by the self-annihilation of weakly interacting massive particles accumulated in the centre of the Sun with respect to the atmospheric background. After data unblinding, the number of neutrinos observed towards the Sun was found to be compatible with background expectations. The 90% CL upper limits in terms of spin-dependent and spin-independent WIMP-proton cross-sections are derived and compared to predictions of two supersymmetric models, CMSSM and MSSM-7. The ANTARES limits are comparable with those obtained by other neutrino observatories and are more stringent than those obtained by direct search experiments for the spin-dependent WIMP-proton cross-section in the case of hard self-annihilation channels (W+W-, tau(+)tau(-)).
55753733
Measurement of the atmospheric muon depth intensity relation with the NEMO Phase-2 tower
Abstract The results of the analysis of the data collected with the NEMO Phase-2 tower, deployed at 3500 m depth about 80 km off-shore Capo Passero (Italy), are presented. Cerenkov photons detected with the photomultipliers tubes were used to reconstruct the tracks of atmospheric muons. Their zenith-angle distribution was measured and the results compared with Monte Carlo simulations. An evaluation of the systematic effects due to uncertainties on environmental and detector parameters is also included. The associated depth intensity relation was evaluated and compared with previous measurements and theoretical predictions. With the present analysis, the muon depth intensity relation has been measured up to 13 km of water equivalent.