117536691
A CPT-even Lorentz-violating nonminimal coupling between fermions and photons
We propose a CPT-even and Lorentz-violating dimension-five nonminimal coupling between fermionic and gauge fields, involving the CPT-even and Lorentz-violating gauge tensor of the Standard-Model Extension. This nonminimal coupling modifies the nonrelativistic regime of Dirac particles, inducing new effects such as an electric-Zeeman-like spectrum splitting and an anomalous-like contribution to the electron magnetic moment. These new effects allow to constrain the magnitude of this nonminimal coupling in 1 part in $10^{16}.$
118609457
Relativistic Landau-Aharonov-Casher quantization based on the Lorentz symmetry violation background
Based on the discussions about the Aharonov-Casher effect in the Lorentz symmetry violation background, we show that the analogue of the relativistic Landau quantization in the Aharonov-Casher setup can be achieved in the Lorentz-symmetry violation background.
119686840
On Aharonov–Casher scattering in a CPT-odd Lorentz-violating background
The effects of a Lorentz symmetry-violating background vector on Aharonov?Casher scattering in the nonrelativistic limit are considered. Using the self-adjoint extension method, we find that there is additional scattering for any value of the self-adjoint extension parameter and non-zero energy bound states for negative values of this parameter. Expressions for the energy bound states, phase-shift and scattering matrix are explicitly determined in terms of the self-adjoint extension parameter. The expression obtained for the scattering amplitude reveals that the helicity is not conserved in this scenario.
119322655
Finiteness of the noncommutative supersymmetric Maxwell-Chern-Simons theory
Within the superfield approach, we prove the absence of UV/IR mixing in the three-dimensional noncommutative supersymmetric Maxwell-Chern-Simons theory at any loop order and demonstrate its finiteness in one, three, and higher loop orders.
119697349
On the spin- 1/2 Aharonov-Bohm problem in conical space: Bound states, scattering and helicity nonconservation
In this work the bound state and scattering problems for a spin-1/2 particle undergone to an Aharonov-Bohm potential in a conical space in the nonrelativistic limit are consider ed. The presence of a �-function singularity, which comes from the Zeeman spin interaction with the magnetic flux tube, is addressed by the self-adjoint extension method. One of the advantages of the present approach is the determination of the self-adjoint extension parameter in terms of physics of the problem. Expressions for the energy bound states, phase-shift and S matrix are determined in terms of the self-adjoint extension parameter, which is explicitly determined in terms of the parameters of the problem. The relation between the bound state and zero modes and the failure of helicity conservation in the scattering problem and its relation with the gyromagnetic ratio g are discussed. Also, as an application, we consider the spin-1/2 AharonovBohm problem in conical space plus a two-dimensional isotropic harmonic oscillator.
118670238
He–McKellar–Wilkens effect and scalar Aharonov–Bohm effect for a neutral particle based on the Lorentz symmetry violation
In this contribution, we discuss the He–McKellar–Wilkens effect and the scalar Aharonov–Bohm effect for neutral particles based on the Lorentz symmetry violation background, by showing that the background of the Lorentz symmetry violation yields Abelian quantum phases for a neutral particle. We also study the non-relativistic bound states for a neutral particle interacting with a Coulomb-like potential based on the Lorentz symmetry violation background given by a fixed vector field parallel to the radial direction.
29515893
Gamma-ray Large-Area Space Telescope (GLAST) balloon flight data handling overview
The Gamma-ray Large-Area Space Telescope (GLAST) balloon flight engineering model (BFEM) represents one of 16 towers that constitute the Large Area Telescope (LAT), a high-energy (> 20 MeV) gamma-ray pair-production telescope being built by an international partnership of astrophysicists and particle physicists for a satellite launch in 2006. The prototype tower consists of a Pb/Si pair-conversion tracker (TKR), a CsI hodoscopic calorimeter (CAL), an anticoincidence detector (ACD), and an autonomous data acquisition (DAQ) system. The self-triggering capabilities and performance of the detector elements have been previously characterized using positron, photon and hadron beams. External target scintillators were placed above the instrument to act as sources of hadronic showers. This paper provides a comprehensive description of the BFEM data-reduction process, from receipt of the flight data from telemetry through event reconstruction and background rejection cuts. The goals of the ground analysis presented here are to verify the functioning of the instrument and to validate the reconstruction software and the background-rejection scheme.
1529836
Search for a new gauge boson in π0 decays
Abstract A search was made for a new light gauge boson X which might be produced in π 0 → γ + X decay from neutral pions generated by 450 GeV protons in the CERN SPS neutrino target. The X's would penetrate the downstream shielding and be observed in the NOMAD detector via the Primakoff effect, in the process of X → π 0 conversion in the external Coulomb field of a nucleus. With 1.45×10 18 protons on target, 20 candidate events with energy between 8 and 140 GeV were found from the analysis of neutrino data. This number is in agreement with the expectation of 18.1±2.8 background events from standard neutrino processes. A new 90 % C.L. upper limit on the branching ratio Br ( π 0 → γ + X ) −5 for X masses ranging from 0 to 120 MeV/ c 2 is obtained.
121387721
A study of the electric charge distributions of quark and gluon jets in hadronic Z0 decays
Abstract A sample of three-jet events containing a lepton with high momentum and transverse momentum is selected from hadronic decays of the Z0. The presence of the lepton indicates the semi-leptonic decay of a bottom quark and allows us, in combination with energy ordering of the jets, to distinguish between quark and gluon jets. The sign of the lepton charge is used to identify jets originating from positively and negatively charged quarks, for the jets with the lepton and for the high energy jets. Defining the jet charge by summing the charge of the particles assigned to a jet, it is observed that the mean jet charge of the quark jets is incompatible with zero and that the sign of the jet charge corresponds to that expected from the charge of the primary quark. In contrast, the mean charge of the gluon jets is consistent with zero.
120875826
Search for massive, unstable photinos that violate R parity
Abstract A search for unstable, massive photinos pair produced in e + e − collisions has been performed using the OPAL detector at LEP. The data sample corresponds to an integrated luminosity of 21 pb −1 collected at center-of-mass energies near the Z 0 resonance. The unstable photino is assumed to decay into τ ± / gn l ( l = e or μ ) final states, thereby violating individual lepton numbers and R parity. This search is inspired by a particular model of supersymmetry which is of interest within the context of solar neutrino experiments because it allows for a large neutrino magnetic moment. The present search excludes a large portion of the parameter space allowed by the model.
123982766
Search for a scalar top quark using the OPAL detector
Abstract A search for a supersymmetric partner of the top quark (t 1 ) has been performed by the OPAL experiment in e + e - collisions at LEP. The integrated luminosity of the data sample analysed was 69.1 pb −1 , which corresponds to 1.68 × 10 6 produced Z 0 → qq events. No t 1 candidates have been found. This study excludes the existence of the t 1 with a mass below 45.1 GeV at 95% C.L., where the mixing angle of left- and right-handed partners is smaller than 0.85 rad or greater than 1.15 rad, and the mass difference between the t 1 and the lightest neutralino is greater than 5 GeV.