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.
118364878
On the superfield effective potential in three dimensions
We develop the superfield approach to the effective potential in three dimensions and calculate the one-loop and two-loop Kahlerian effective potential in commutative and noncommutative cases.
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.
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.
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.
122063121
Relativistic Anandan quantum phase in the Lorentz violation background
We study the influence of a classical background based on the violation of the Lorentz symmetry on the relativistic Anandan quantum phase. We show that the choice of the Lorentz symmetry violation background provides an abelian contribution for the relativistic Anandan quantum phase.
53499025
Performance of the NOMAD-STAR detector
The NOMAD-STAR detector is a silicon vertex installed in the NOMAD spectrometer at the CERN SPS neutrino beam. It consists of four layers of a passive boron carbide target with a total mass of 45 kg and five layers of 600 single sided silicon microstrip detectors covering a total area of 1.14m^2. About 11,500 nu_mu charged current interactions were reconstructed in the fiducial volume of NOMAD-STAR from the neutrino run in 1998. The potential use of silicon detectors for nu_mu (nu_e) nu_tau oscillations depends on the observation of the tau candidates by the experimental signature of a large impact parameter, in the case of the one prong decay of the tau, or a double vertex, in the case of the three prong decay. The main aim of NOMAD-STAR is to measure the impact parameter and vertex distributions of charged current interactions, which constitute the main backgrounds for the oscillation signals, to understand the significance of a potential signal in a future experiment. The present paper describes the experience gained in the operation of this silicon vertex detector, and the peformance achieved with it.
120356698
A study of two-particle momentum correlations in hadronic Z0 decays
Abstract We report on a measurement of two-particle momentum correlations in hadronic decays of the Z 0 at LEP. These data are compared with recent analytic QCD calculations based on the summation of leading and next-to-leading logarithms, and with QCD Monte Carlo simulations. We find that the analytic calculations show the same general features as the data, but that the overall level of the correlations is not reproduced, suggesting that higher order or hadronization effects are significant. This contrasts with the success of similar QCD calculations in describing single-particle momentum distributions. QCD Monte Carlo models are found to give a reasonable level of correlation, with parton shower models incorporating string hadronization giving the best description of the data.
123154769
A study of B meson oscillations using hadronic Z 0 decays containing leptons
An event sample enriched in semileptonic decays of b hadrons is selected using an inclusive lepton selection from approximately 3.0 million hadronic Z(0) decays collected with the OPAL detector. This sample is used to investigate B meson oscillations by reconstructing a proper decay time for the parent of each lepton, using a jet charge method to estimate the production flavour of this parent, and using the lepton charge to tag the decay flavour. We measure the mass difference between the two B-d(0) mass eigenstates upper-delta-m(d)=0.444plusminus0.029(-0.017)(+0.020)ps(-1).For the B-s(0) system, we find upper-delta-m(s)>3.1ps(-1) at the 95% confidence level. This limit varies only a little if alternative limit setting approaches are adopted. Regions at higher upper-delta-m(s) values are also excluded with some methods for setting the limit.By studying the charge symmetry of the B-d(0) mixing structure, we are able to constrain possible CP and CPT violating effects. We measure the CP violation parameter Re-epsilon(B)=-0.006plusminus0.010plusminus0.006 and the indirect CPT violating parameter Im-delta(B)=-0.020plusminus0.016plusminus0.006. If we invoke CPT symmetry, then we obtain Re-epsilon(B)=0.002plusminus0.007plusminus0.003.
6681884
Results from the beam test of the engineering model of the GLAST large area telescope
This paper describes the results of a beam test using the Engineering Model of the GLAST Large Area Telescope, which was installed in a beam of positrons, hadrons and tagged photons at SLAC. The performance of the four subsystems, Anti Coincidence Detector, Silicon Tracker, Calorimeter and Data Acquisition will be described.
121606064
Search for scalar top and scalar bottom quarks using the OPAL detector at LEP
The scalar top quark can be the lightest charged supersymmetric particle and it can be lighter than the top quark itself in supersymmetric extensions of the Standard Model. A search for a scalar top quark has been performed using a total data sample of 15.2 pb−1 at centre-of-mass energies of √s = 130, 136, and 161 GeV collected with the OPAL detector at LEP. No evidence was found above the background level expected from the Standard Model. The 95% C.L. lower limit on the scalar top quark mass is 58.7 GeV, if the mixing angle between the supersymmetric partners of the left- and right-handed states of the top quark is smaller than π4. If the mixing angle is zero, the limit is 65.4 GeV. These limits were obtained on the condition that the scalar top quark decays into a charm quark and the lightest neutralino, and that the mass difference between the scalar top quark and the lightest neutralino is larger than 10 GeV. Assuming a relatively light scalar neutrino, we also studied the complementary decay mode of the scalar top quark in which it decays into a bottom quark, a charged lepton, and a scalar neutrino. A mass limit on the light scalar bottom quark was also set in this study.