A Photoelectric Seed Counter

Small scale yield studies, germination tests, controlled plantings, and packaging often require the counting of large numbers of seeds. The system described in this paper uses a photosensitive detector and a vacuum pickup to count individual seeds and gives a direct digital readout. The count rate is limited only by how quickly the seeds can be fed through the counting tube without clogging it or having them touch each other. This greatly speeds seed counting, eliminates operator error, and reduces operator fatigue. With the addition of a relatively simple predetermining circuit, a fixed number of seeds may be counted and a control function can be exercised. This capability is immediately applicable to packaging or repetitious batching of seeds. Zero error for any given number of seeds is attainable if the seeds are fed through the count tube carefully because of the completely digital nature of the circuit

Top quark pair production cross section in the lepton+jets channel using b-tagging at D0

The top quark pair production cross section measurement in the lepton+jets channel with b-tagging algorithm is described. About 900 pb{sup -1} data collected by the D0 detector at the Fermilab Tevatron are used for this analysis. In this thesis, event selection, background estimation, and cross section calculation are discussed in detail. In addition, calibration of the Luminosity Monitor readout electronics and a new b-tagging algorithm, the SLTNN tagger, are also discussed in this thesis

Photoelectric Tachometer for Precise Centrifuge Speed Determination

Certain chemical and physical investigations such as the mechanical analysis of soils by centrifugation require that the speed of rotation of the centrifuge be precisely determined. For a cost of approximately $40.00, when used with instrumentation normally available in research laboratories, the system outlined provides a vivid, unambiguous indication of the speed of rotation, the accuracy of which is limited only by the frequency standard used

A Two-Channel Electrical Counter

Many studies require that the magnitude of 2 variables be determined simultaneously. Usually this is done by an operator using 2 hand-operated mechanical reciprocating counters. The operator records one variable on one counter and the second on the other. Our specific problem was to determine pollinator densities in field plots. The operators counted a fixed number of flowers and recorded the number of pollinators on these flowers. A number of problems arise from the use of these devices. The reciprocating counters are hard to use, resulting in manual fatigue, and are infamous for missing counts, particularly when they become worn. The operator must have both hands full all the time he is making the count. If the operator must do something else with his hands, he must store the counters where they will not become lost or interchanged

How the quark self-energy affects the color-superconducting gap

We consider color superconductivity with two flavors of massless quarks which form Cooper pairs with total spin zero. We solve the gap equation for the color-superconducting gap parameter to subleading order in the QCD coupling constant $g$ at zero temperature. At this order in $g$, there is also a previously neglected contribution from the real part of the quark self-energy to the gap equation. Including this contribution leads to a reduction of the color-superconducting gap parameter \f_0 by a factor b_0'=\exp \big[ -(\p ^2+4)/8 \big]\simeq 0.177. On the other hand, the BCS relation T_c\simeq 0.57\f_0 between \f_0 and the transition temperature $T_c$ is shown to remain valid after taking into account corrections from the quark self-energy. The resulting value for $T_c$ confirms a result obtained previously with a different method.Comment: Revtex, 8 pages, no figur

(Anti-)self-dual homogeneous vacuum gluon field as an origin of confinement and SUL(NF)×SUR(NF)SU_L(N_F)\times SU_R(N_F) symmetry breaking in QCD

It is shown that an (anti-)self-dual homogeneous vacuum gluon field appears in a natural way within the problem of calculation of the QCD partition function in the form of Euclidean functional integral with periodic boundary conditions. There is no violation of cluster property within this formulation, nor are parity, color and rotational symmetries broken explicitly. The massless limit of the product of the quark masses and condensates, $m_f \langle \bar\psi_f \psi_f \rangle$, is calculated to all loop orders. This quantity does not vanish and is proportional to the gluon condensate appearing due to the nonzero strength of the vacuum gluon field. We conclude that the gluon condensate can be considered as an order parameter both for confinement and chiral symmetry breaking.Comment: 16 pages, LaTe

Multiplicative renormalizability and quark propagator

The renormalized Dyson-Schwinger equation for the quark propagator is studied, in Landau gauge, in a novel truncation which preserves multiplicative renormalizability. The renormalization constants are formally eliminated from the integral equations, and the running coupling explicitly enters the kernels of the new equations. To construct a truncation which preserves multiplicative renormalizability, and reproduces the correct leading order perturbative behavior, non-trivial cancellations involving the full quark-gluon vertex are assumed in the quark self-energy loop. A model for the running coupling is introduced, with infrared fixed point in agreement with previous Dyson-Schwinger studies of the gauge sector, and with correct logarithmic tail. Dynamical chiral symmetry breaking is investigated, and the generated quark mass is of the order of the extension of the infrared plateau of the coupling, and about three times larger than in the Abelian approximation, which violates multiplicative renormalizability. The generated scale is of the right size for hadronic phenomenology, without requiring an infrared enhancement of the running coupling.Comment: 17 pages; minor corrections, comparison to lattice results added; accepted for publication in Phys. Rev.

Effects of dimensionality and anisotropy on the Holstein polaron

We apply weak-coupling perturbation theory and strong-coupling perturbation theory to the Holstein molecular crystal model in order to elucidate the effects of anisotropy on polaron properties in D dimensions. The ground state energy is considered as a primary criterion through which to study the effects of anisotropy on the self-trapping transition, the self-trapping line associated with this transition, and the adiabatic critical point. The effects of dimensionality and anisotropy on electron-phonon correlations and polaronic mass enhancement are studied, with particular attention given to the polaron radius and the characteristics of quasi-1D and quasi-2D structures. Perturbative results are confirmed by selected comparisons with variational calculations and quantum Monte Carlo data

Antiflow of kaons in relativistic heavy ion collisions

We compare relativistic transport model calculations to recent data on the sideward flow of neutral strange K^0_s mesons for Au+Au collisions at 6 AGeV. A soft nuclear equation of state is found to describe very well the positive proton flow data measured in the same experiment. In the absence of kaon potential, the K^0 flow pattern is similar to that of protons. The kaon flow becomes negative if a repulsive kaon potential determined from the impulse approximation is introduced. However, this potential underestimates the data which exhibits larger antiflow. An excellent agreement with the data is obtained when a relativistic scalar-vector kaon potential, that has stronger density dependence, is used. We further find that the transverse momentum dependence of directed and elliptic flow is quite sensitive to the kaon potential in dense matter.Comment: 5 pages, Revtex, 4 figure

Polaron Effective Mass, Band Distortion, and Self-Trapping in the Holstein Molecular Crystal Model

We present polaron effective masses and selected polaron band structures of the Holstein molecular crystal model in 1-D as computed by the Global-Local variational method over a wide range of parameters. These results are augmented and supported by leading orders of both weak- and strong-coupling perturbation theory. The description of the polaron effective mass and polaron band distortion that emerges from this work is comprehensive, spanning weak, intermediate, and strong electron-phonon coupling, and non-adiabatic, weakly adiabatic, and strongly adiabatic regimes. Using the effective mass as the primary criterion, the self-trapping transition is precisely defined and located. Using related band-shape criteria at the Brillouin zone edge, the onset of band narrowing is also precisely defined and located. These two lines divide the polaron parameter space into three regimes of distinct polaron structure, essentially constituting a polaron phase diagram. Though the self-trapping transition is thusly shown to be a broad and smooth phenomenon at finite parameter values, consistency with notion of self-trapping as a critical phenomenon in the adiabatic limit is demonstrated. Generalizations to higher dimensions are considered, and resolutions of apparent conflicts with well-known expectations of adiabatic theory are suggested.Comment: 28 pages, 15 figure