366 research outputs found
Supernova Neutrino Detection: Experimental Status and Perspectives
No full textAfter the historical detection of a neutrino burst coming from the supernova 1987A, the interest for supernova neutrinos continuously grew up. Such interest has been further strengthened by the recent enormous progresses in the understanding of neutrino mixing and oscillations. Since neutrinos are very elusive particles, they can preserve a lot of information about their production site even if they traverse huge distances (tens of Kpc or more) before being detected. On the other hand, supernovae are very peculiar physical systems, with unique conditions of density and temperature; then, the interior of a collapsed star is the ideal environment where the neutrino flavour conversion mediated by matter effects can be realized. Moreover, since the neutrino detectors are sensitive to stellar gravitational collapses everywhere in the galaxy, a type II supernova (from now on: SN) explosion offers an extraordinary possibility for studying neutrino properties beyond the Standard Model (mass, electric charge, magnetic moment, mixing ...) in huge ranges of distances and densities. FInally, supernovae emit neutrinos, photons and probably gravitational waves; then, a combined observation of all forms of radiation released during a stellar collapse would provide not only an unprecedented amount of information about the collapse mechanism, but also great opportunities for testing various aspects of Special and General Relativity theories.
In this paper I review the present and planned supernova neutrino detectors, their experimental techniques and the expected neutrino signal and discuss the implications for the supernova and neutrino physics of a high statistics neutrino burst detection
Track Reconstruction in the Forward Region of the Detector ILD at the Electron-Positron Linear Collider ILC
No full textThe subject of this thesis is the reconstruction of charged particle tracks in the forward region of the International Large Detector (ILD), one of two validated detector concepts for the future International Linear Collider (ILC). Recent results from the Large Hadron Collider (LHC) suggest that the last missing piece of the Standard Model (SM) of particle physics, the Higgs boson, could have been found. Complementary to the LHC, an electron-positron linear collider would have the capability to explore with high precision the characteristics of the Higgs boson (e.g. spin, parity, coupling strengths), to compare them against the predictions of the SM, and also give unbiased contributions to the search for physics beyond the SM, such as supersymmetry or extra spatial dimensions. Experiments at ILD will benefit from this detector's tracking system, consisting of a large central time projection chamber (TPC) augmented by several silicon tracking systems, granting unprecedented track resolution, redundancy and angular hermeticity. The forward region of ILD, covering the space between beam tube and TPC, contains the Forward Tracking Detector (FTD): two arms of seven disk-shaped silicon detectors (two Si pixel and ve double-sided Si strip detectors). In order to fully exploit ILD's hardware assets, the software for event reconstruction must aim for both the highest level of precision and efficiency. In this context, new software for track reconstruction in the forward region was developed by the author (packages KiTrack and ForwardTracking): it processes the signals of FTD with the goal to efficiently nd and precisely reconstruct the genuine tracks that have traversed FTD and caused these signals. The methods used are based on state-of-the-art algorithms: a cellular automaton (CA), a Kalman lter (KF), and a Hopeld neural network (HNN). The new packages follow a modern object-oriented design philosophy, granting high flexibility and maintainability. The results show superior performance w.r.t. older legacy software, yielding higher efficiencies and better handling of the expected background concerning ghost rate, efficiency and processing time. The forward tracking packages presented in this thesis have been successfully implemented into the standard event reconstruction framework of ILD. They are currently used for benchmark event processing for the Detailed Baseline Design (DBD), a report outlining the feasibility and features of the International Large Detector, to be published around the end of this year
EVIDENCE FOR A NARROW WIDTH BOSON OF MASS 2.95-GeV
No full textIn a search for resonances coupled to the pp pi /sup -/ system, pi /sup -/p interactions at 16 GeV/c giving a forward antiproton have been studied, using the Omega spectrometer at CERN. In the final states involving a p, p and pi /sup -/ a 5.6 (6.3) standard deviation enhancement is observed in the pp pi /sup -/ mass spectrum at (2.95+or-0.01) GeV with a width consistent with the resolution ( sigma =15 MeV). The production cross section*branching ratio is estimated to be of the order 1 mu b. The data are consistent with a resonance decaying partly via intermediate pp final states. (5 refs)
A study of intermittency in Hadronic Z Decays
No full textA study on the modifications of the relation between author and lector due to the translation from text to hypertex
Test of the Zweig rule in pi /sup -/p interactions at 19 GeV/c
No full textReports the observation of phi production in pi /sup -/p interactions at 19 GeV/c with (44+or-10) events in the final state phi pi /sup +/ pi /sup -/ pi /sup -/p and (45+or-9) events in phi K/sup +/K/sup -/ pi /sup -/p. The production ratios phi pi /sup +/ pi /sup -/p/ omega pi /sup +/ pi /sup -/ pi /sup -/p approximately=0.005 and phi K/sup +/K /sup -/ pi /sup -/p/ rho /sup 0/K/sup +/K/sup -/ pi /sup -/p approximately=0.45 agree with Zweig-rule expectations. (8 refs)
Search for single top quark production via contact interactions at LEP2
No full textSingle top quark production via four-fermion contact interactions associated to flavour-changing neutral currents was searched for in data taken by the DELPHI detector at LEP2. The data were accumulated at centre-ofmass energies ranging from 189 to 209 GeV, with an integrated luminosity of 598.1 pb−1. No evidence for a signal was found. Limits on the energy scale Λ, were set for scalar-, vector- and tensor-like coupling scenarios. © The Author(s) 2011
A study of the b-quark fragmentation function with the DELPHI detector at LEP I and an averaged distribution obtained at the Z Pole
No full textThe nature of b-quark jet hadronisation has been investigated using data taken at the Z peak by the DELPHI detector at LEP. Two complementarymethods are used to reconstruct the energy of weakly decaying b-hadrons, EweakB. The average value of xweakB = EweakB/Ebeam is measured to be 0.699 ± 0.011. The resulting xweakB distribution is then analysed in the framework of two choices for the perturbative contribution (parton shower and Next to Leading Log QCD calculation) in order to extract measurements of the non-perturbative contribution to be used in studies of bhadron production in other experimental environments than LEP. In the parton shower framework, data favour the Lund model ansatz and corresponding values of its parameters have been determined within PYTHIA 6.156 from DELPHI data: a=1.84+0.23-0.21 and b=0.642+0.073-0.063 GeV-2, with a correlation factor ρ=92.2%. Combining the data on the b-quark fragmentation distributions with those obtained at the Z peak by ALEPH, OPAL and SLD, the average value of xweakB is found to be 0.7092 ± 0.0025 and the non-perturbative fragmentation component is extracted. Using the combined distribution, a better determination of the Lund parameters is also obtained: a = 1.48+0.11-0.10 and b = 0.509+0.024-0.023 GeV-2, with a correlation factor ρ 92.6%. © The Author(s) 2011
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