228 research outputs found
Investigation of the Impact of Magnetic Fields on Scattering Muography Images
Muography is a non-invasive imaging technique that exploits cosmic-ray muons
to probe various targets by analyzing the absorption or scattering of muons.
The method is particularly useful for applications ranging from geophysical
exploration to security screening, including the identification of nuclear
materials. This study leverages both Monte Carlo simulations and the Point of
Closest Approach (PoCA) algorithm for image reconstruction to specifically
explore the distortions caused by magnetic fields in scattering muography
images. In the PoCA algorithm, it is assumed that all scattering of a muon
during its travel in material occurs at a single point, known as the PoCA
point. Each PoCA point is characterized by a scattering angle, whose
distribution provides insights into the density and elemental composition of
the target material. However, magnetic fields can influence muon trajectories
according to Lorentz law, affecting the estimated positions of the PoCA points
and the calculated scattering angles. This introduces challenges in
applications such as border security control systems. Moreover, the presence of
magnetic fields can lead to what we term "magnetic jamming", where the
resulting muography image is distorted or misleading. This effect further
complicates the accurate identification and interpretation of target materials.
Our findings underline the necessity to account for magnetic field distortions
when utilizing scattering muography in practical scenarios
Portable Resistive Plate Chambers for Muography in confined environments
Muography (or muon radiography) is an imaging technique that relies on the
use of cosmogenic muons as a free and safe radiation source. It can be applied
in various fields such as archaeology, civil engineering, geology, nuclear
reactor monitoring, nuclear waste characterization, underground surveys, etc.
In such applications, sometimes deploying muon detectors is challenging due to
logistics, e.g. in a narrow underground tunnel or mine. Therefore, we are
developing muon detectors whose design goals include portability, robustness,
autonomy, versatility, and safety. Our portable muon detectors (or
``muoscopes'') are based on Resistive Plate Chambers (RPC), planar detectors
that use ionization in a thin gas gap to detect cosmic muons. Prototype RPCs of
active area and were built in our
laboratories at Louvain-la-Neuve (UCLouvain) and Ghent (UGent) to test and
compare various design options. Benefiting from the experience gained in
building and operating these prototypes, we are proceeding towards the
development of improved prototypes with more advanced technical layout and
readiness. In this paper we provide the status of our performance studies,
including the cross-validation of the two types of prototypes in a joint data
taking, and an outline of the direction ahead
Small-area Portable Resistive Plate Chambers for Muography
Muography is finding applications in various domains such as volcanology,
archaeology, civil engineering, industry, mining, and nuclear waste surveys. To
simplify transportation and installation in remote locations after laboratory
testing, a fully portable and autonomous muon telescope based on Resistive
Plate Chambers (RPCs) is being developed. Two glass-RPC prototypes have been
created, sharing the same design goals but with different detector parameters,
and comparative studies are ongoing. Drawing from prototype experience, a
double-gap RPC with advanced features and improved spatial resolution is
constructed. Resistive electrodes are produced manually, and a new data
acquisition board is currently undergoing calibration. The results on prototype
performance, readout board comparisons and the technical progress on the
double-gap RPC are presented
Search for composite and exotic fermions at LEP2
A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172 GeV and 161 GeV. The search for pair-produced new leptons establishes 95% confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermion
Measurement of the gluon fragmentation function and a comparison of the scaling violation in gluon and quarks jets
The fragmentation functions of quarks and gluons are measured in various three-jet topologies in Z decays from the full data set collected with the Delphi detector at the Z resonance between 1992 and 1995. The results at different values of transverse momentum-like scales are compared. A parameterization of the quark and gluon fragmentation functions at a fixed reference scale is given. The quark and gluon fragmentation functions show the predicted pattern of scaling violations. The scaling violation for quark jets as a function of a transverse momentum-like scale is in a good agreement with that observed in lower energy e+eâ annihilation experiments. For gluon jets it appears to be significantly stronger. The scale dependences of the gluon and quark fragmentation functions agree with the prediction of the DGLAP evolution equations from which the colour factor ratio CA/CF is measured to be: CACF=2.26±0.09stat.±0.06sys.±0.12clus.,scale
Investigation of the splitting of quark and gluon jets
The splitting processes in identified quark and gluon jets are investigated using longitudinal and transverse observables. The jets are selected from symmetric three-jet events measured in Z decays with the Delphi detector in 1991-1994. Gluon jets are identified using heavy quark anti-tagging. Scaling violations in identified gluon jets are observed for the first time. The scale energy dependence of the gluon fragmentation function is found to be about two times larger than for the corresponding quark jets, consistent with the QCD expectation TeX . The primary splitting of gluons and quarks into subjets agrees with fragmentation models and, for specific regions of the jet resolution TeX , with NLLA calculations. The maximum of the ratio of the primary subjet splittings in quark and gluon jets is TeX . Due to non-perturbative effects, the data are below the expectation at small TeX . The transition from the perturbative to the non-perturbative domain appears at smaller TeX for quark jets than for gluon jets. Combined with the observed behaviour of the higher rank splittings, this explains the relatively small multiplicity ratio between gluon and quark jets
Search for promptly produced heavy quarkonium states in hadronic Z decays
A search has been made for direct production of heavy quarkonium states in more than 3 million hadronicZ 0 decays in the 1991Âż1994 DELPHI data. PromptJ/Ï, Ï(2S) andÎ candidates have been searched for through their leptonic decay modes using criteria based on the kinematics and decay vertex positions. New upper limits are set at the 90% confidence level forBr(Z 0â(Qq)X)/Br(Z 0â hadrons) for various strong production mechanisms ofJ/Ï andÎ; these range down to 0.9Ă10â4. The limits are set in the presence of a small excess (âŒ1% statistical probability of a background fluctuation) in the sum of candidates from promptJ/Ï, Ï(2S),Îł(1S),Îł(2S) andÎł(3S) relative to the estimated background
A Measurement of B Meson Production and Lifetime Using D`â Events in Z0 Decays
A study of B meson decays into D l- X final states is presented. In these events, neutral and charged D mesons originate predominantly from B+ and B0 decays, respectively. The dilution of this correlation due to D** production has been taken into account. From 263700 hadronic Z0 decays collected in 1991 with the DELPHI detector at the LEP collider, 92 D0 --> K- pi+, 35 D+ --> K- pi+ pi+ and 61 D*+ --> D0 pi+ followed by D0 --> K- pi+ or D0 --> K- pi+ pi+ pi-, are found with an associated lepton of the same charge as the kaon. From the D0 l- and D*+ l-, the probability f(d) that a b quark hadronizes into a B- (or B0BAR),meson is found to be 0.44 +/-0.08 +/-0.09, corresponding to a total (B(s) + LAMBDA(b)) hadronization fraction of 0.12(-0.12)+0.24 .By reconstructing the energy of each B meson, the b quark fragmentation is directly measured for the first time. The mean value of the B meson energy fraction is: [X(E)(B)] = 0.695+/-0.015(stat.)+/-0.029(syst.) Reconstructing D-lepton vertices, the following B life-times are measured: tau(B) = 1.27(-0.18)+0.22(stat.)+/-0.15(syst.) ps, where bBAR --> D0 l- X, tau(B) = 1.18(-0.27)+0.39(stat.)+/-0.15(syst.) ps, where BBAR --> D+ l- X, T(B) = 1.19(-0.19)+0.25(stat.)+/-0.15(syst.) ps where BBAR --> D*+ l- X, and an average tau(B) = 1.23(-0.13)+0.14(stat.)+/-0.15(syst.) ps is found. Allowing for decays into D** l- vBAR, the B+ and B0 lifetimes are: tau(B+)= 1.30(0.29)+0.33(stat.)+/-0.15(syst. exp.) +/-0.05(syst. D**) ps, tau(B0)= 1.17(-0.23)+0.29(stat.)+/-0.15(syst. exp.) +/-0.05 (syst. D**) ps, tau(B+)/tau(B0) = 1.11(0.39)+0.51(stat.)+/-0.05(syst. exp.) +/-0.10(syst. D**) ps
Measurement of the triple-gluon vertex from 4-JET events at LEP
From the combined data of 1990 and 1991 of the DELPHI experiment at LEP, 13057 4-jet events are obtained and used for determining the contribution of the triple-gluon vertex. The relevant variables are the generalized Nachtmann Reiter angle theta(NR)* and the opening angle of the two least energetic jets. A fit to their two-dimensional distribution yields C(A)/C(F)=2.12+/-0.35 and N(C)/N(A)=0.46+/-0.19, where C(A)/C(F) is the ratio of the coupling strength of the triple-gluon vertex to that of gluon bremsstrahlung from quarks, and N(C)/N(A), the ratio of the number of quark colours to the number of gluons. This constitutes a convincing model-independent proof of the existence of the triple-gluon vertex, since its contribution is directly proportional to C(A)/C(F). The results are in agreement with the values expected from QCD: C(A)/C(F)=2.25, and N(C)/N(A)=3/8
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