Kunitaka Kondo

Dynamical Likelihood Method for Reconstruction of Events with Missing Momentum. I. Method and Toy Models

A likelihood method is proposed for analysis of events which are produced in the hadron-hadron collision accompanied by the missing transverse momentum. The kinematical reconstruction is made by assuming variables sufficient to define the kinematics, and the likelihood of the assumption is evaluated by using the structure functions, the differential cross sections for intermediate states and the decay rate for final state configurations. The capability of the method is examined for simplified models of events including one- and two-missing massless particles. It is shown that (a) when events are well identified, dynamical parameters involved in the process canbe determined, and (b) in new particle searches, narrow mass spectrums are obtained.

The CDF central electromagnetic calorimeter

The central electromagnetic calorimeter for the Collider Detector at Fermilab uses a hybrid design with scintillator and wavelength shifter for energy measurement and an embedded strip chamber for position determination and longitudinal shower development. Complementary calibration systems are incorporated in the design. Calorimeter characteristics and performance are summarized. An average energy resolution, σ(E)E, of 13.5%√E sin θ (with E in GeV), and a position resolution of ±2 mm at 50 GeV are measured.

Dynamical likelihood method for reconstruction of events with missing momentum. II, Mass spectra for 2→2 processes

A method of the event reconstruction based on the parton level dynamics is formulated. Formulae for the mass probability are given for the 2→2 processes where 0 or 1 missing particles per channel are included in the final states. Uncertainties of the final parton momenta and their propagation to the reconstructed intermediate states are integrated into the formulation. An application to analysis of the top quark pair production with standard decay modes is discussed.

Stark-Zeeman Effects on Asymmetric Top Molecules. Formaldehyde H2CO.

The combined Stark-Zeeman effects for asymmetric top molecules with no accidental degeneracies are studied by perturbation treatments. The theory was applied successfully to the analysis of the experimental results of Stark-Zeeman effect on the microwave spectrum of formaldehyde H 2 CO. By the influence of the electric field perpendicular to the magnetic field, split components of the transition 2 11 →2 12 which, in the magnetic quantum number M , correspond to Δ M =±3 were observed. These components allowed a precise determination of the molecular g -factor for this transition.

A new scintillator and wavelength shifter

Abstract We have developed a new types of scintillator and a wavelength shifter to be used for high energy particle calorimeters. To obtain a long attenuation length, two kinds of fluors are mixed in a polystyrene base. The wavelength shifter has a new material matching its absorption spectrum to the wavelength of the scintillation light. Their common characteristics are a relatively high light output and a long attenuation length with a reasonable cost.

Dynamical Likelihood Method for Reconstruction of Events with Missing Momentum. III. Analysis of a CDF High P T eµ Event as t\bar t Production

A high P T dilepton event observed in 1.8 TeV bar p p collisions at CDF is analyzed with Dynamical Likelihood Method. A likelihood function for the dilepton decay channel in the t bar t production is given. We illustrate how the method can be applied to eliminate some typical Standard Model processes that could generate spurious events. By assuming that the event comes from the t bar t production, the maximum likelihood mass and the expectation value of mass are evaluated as 124 and 136 GeV/c 2 , respectively, and a mass range at the 68% confidence level is estimated to be (119,151) GeV/c 2 , including measurement errors.

Microwave Zeeman Effect of Formaldehyde

Zeeman effects in the absorption spectra of formaldehyde H 2 CO, HDCO, and D 2 CO were studied in microwave region with magnetic field of 1500∼300 oersteds. The effective g -values in several rotational states and the elements of g -tensor g a a , g b b , and g c c of these molecules were determined. Dependences of the effective g -values on the rotational quantum numbers J , τ were consistent among these isotopically substituted molecules. The components of the g -tensors of these molecules have been found to be g a a =2.86±0.04 for H 2 CO, 2.00±0.05 for HDCO, and 1.46±0.05 for D 2 CO. They are extraordinarily large compared to those of other molecules already known. A brief qualitative interpretation is given.

Coherent Bremsstrahlung from Si Single Crystal : I. Experiment

The interference effects in the production of bremsstrahlung in a silicon single crystal have been studied by using 720 MeV electrons. The energy spectrum of the bremsstrahlung has exhibited interference maxima of the first five orders. The intensity variation of the 150 MeV photons with the rotation of the crystal has shown also three interference Maxima on each side of the central minimum. The observed interference conditions for the photon energy and angles of incidence of electrons relative to crystal axes are in good agreement with the theory.

The Production Asymmetry in γ+n→π-+p Process with Polarized Photons

The production asymmetry in the reaction γ+ n →π - + p is measured at 90° in the center-of-mass system and at five photon energies from 357 to 555 MeV. Linearly polarized photons are obtained by means of the coherent breamsstrahlung process from a silicon single crystal. Negative pions and recoiling protons from a liquid-deuterium target are detected simultaneously so that events originated from neutrons almost at rest in the deuterons are selected. The asymmetry data are compared with the dispersion-relation calculation of Berends, Donnachie, and Weaver, and with that of Schmidt et al. It is shown that the contribution from the Roper P 11 (1470) resonance is small in the pion photoproduction process.

Measurement of Propagation Velocities of the Normal Zone in a 1 mφ×1 m Superconducting Solenoid Magnet

Propagation velocities of the normal zone in a 1 m×1 m superconducting solenoid magnet were unambiguously measured as a function of the magnet excitation current by inducing quenches with a heater. The magnet was built to study the feasibility of constructing thin, large solenoid magnets and it has a single layer aluminum-stabilized NbTi/Cu superconductor of 269 turns. The ratio of Al:NbTi:Cu of the conductor is 24:1:1. The design current of the conductor is 4.5 kA at 1.5 Tesla. Measured velocities are 30, 65, and 90 m/s in the direction of the conductor at 2020, 3030, and 3540 A, respectively. Thermal distributions inside the coil after quenches were quite uniform and no local overheating was observed.