Design and commissioning of a timestamp-based data acquisition system for the DRAGON recoil mass separator

The DRAGON recoil mass separator at TRIUMF exists to study radiative proton and alpha capture reactions, which are important in a variety of astrophysical scenarios. DRAGON experiments require a data acquisition system that can be triggered on either reaction product ($\gamma$ ray or heavy ion), with the additional requirement of being able to promptly recognize coincidence events in an online environment. To this end, we have designed and implemented a new data acquisition system for DRAGON which consists of two independently triggered readouts. Events from both systems are recorded with timestamps from a $20$ MHz clock that are used to tag coincidences in the earliest possible stage of the data analysis. Here we report on the design, implementation, and commissioning of the new DRAGON data acquisition system, including the hardware, trigger logic, coincidence reconstruction algorithm, and live time considerations. We also discuss the results of an experiment commissioning the new system, which measured the strength of the $E_{\text{c}.\text{m}.} = 1113$ keV resonance in the $^{20}$Ne$\left(p, \gamma \right)^{21}$Na radiative proton capture reaction.Comment: 11 pages, 7 figures, accepted for publication in EPJ A "tools for experiment and theory

‘‘There’s so much more to it than what I initially thought’’: Stepping into researchers’ shoes with a class activity in a first year psychology survey course

In psychology, it is widely agreed that research methods, although central to the discipline, are particularly challenging to learn and teach, particularly at introductory level. This pilot study explored the potential of embedding a student-conducted research activity in a one-semester undergraduate Introduction to Psychology survey course, with the aims of (a) engaging students with the topic of research methods; (b) developing students’ comprehension and application of research methods concepts; and (c) building students’ ability to link research with theory. The research activity explored shoe ownership, examining gender differences and relationships with age, and linking to theories of gender difference and of consumer identity. The process of carrying out the research and reflecting on it created a contextualized, active learning environment in which students themselves raised many issues that research methods lectures seek to cover. Students also wrote richer assignments than standard first year mid-term essay

Determination of the QCD color factor ratio CA/CF from the scale dependence of multiplicity in three jet events

I examine the determination of the QCD color factor ratio CA/CF from the scale evolution of particle multiplicity in e+e- three jet events. I fit an analytic expression for the multiplicity in three jet events to event samples generated with QCD multihadronic event generators. I demonstrate that a one parameter fit of CA/CF yields the expected result CA/CF=2.25 in the limit of asymptotically large energies if energy conservation is included in the calculation. In contrast, a two parameter fit of CA/CF and a constant offset to the gluon jet multiplicity, proposed in a recent study, does not yield CA/CF=2.25 in this limit. I apply the one parameter fit method to recently published data of the DELPHI experiment at LEP and determine the effective value of CA/CF from this technique, at the finite energy of the Z0 boson, to be 1.74+-0.03+-0.10, where the first uncertainty is statistical and the second is systematic.Comment: 20 pages including 6 figures Version 2 corrects typographical error in equation (2

Comparison of the Geometrical Characters Inside Quark- and Gluon-jet Produced by Different Flavor Quarks

The characters of the angular distributions of quark jets and gluon jets with different flavors are carefully studied after introducing the cone angle of jets. The quark jets and gluon jets are identified from the 3-jet events which are produced by Monte Carlo simulation Jetset7.4 in e+e- collisions at $\sqrt s$=91.2GeV. It turns out that the ranges of angular distributions of gluon jets are obviously wider than that of quark jets at the same energies. The average cone angles of gluon jets are much larger than that of quark jets. As the multiplicity or the transverse momentum increases, the cone-angle distribution without momentum weight of both the quark jet and gluon jet all increases, i.e the positive linear correlation are present, but the cone-angle distribution with momentum weight decreases at first, then increases when n > 4 or p_t > 2 GeV. The characters of cone angular distributions of gluon jets produced by quarks with different flavors are the same, while there are obvious differences for that of the quark jets with different flavors.Comment: 13 pages, 6 figures, to be published on the International Journal of Modern Physics

The dihadron fragmentation function and its evolution

Dihadron fragmentation functions and their evolution are studied in the process of $e^+e^-$ annihilation. Under the collinear factorization approximation and facilitated by the cut-vertex technique, the two hadron inclusive cross section at leading order (LO) is shown to factorize into a short distance parton cross section and a long distance dihadron fragmentation function. We provide the definition of such a dihadron fragmentation function in terms of parton matrix elements and derive its DGLAP evolution equation at leading log. The evolution equation for the non-singlet quark fragmentation function is solved numerically with a simple ansatz for the initial condition and results are presented for cases of physical interest.Comment: 27 pages, 2 column, Revtex4, 21 figure

Hadron multiplicities in e+e- annihilation with heavy primary quarks

The multiple hadron production in the events induced by the heavy primary quarks in $e^+e^-$ annihilation is reconsidered with account of corrected experimental data. New value for the multiplicity in $b\bar{b}$ events is presented on the basis of pQCD estimates.Comment: 16 pages, 6 figures. Version accepted for publication in EPJ

A Monte-Carlo generator for statistical hadronization in high energy e+e- collisions

We present a Monte-Carlo implementation of the Statistical Hadronization Model in e+e- collisions. The physical scheme is based on the statistical hadronization of massive clusters produced by the event generator Herwig within the microcanonical ensemble. We present a preliminary comparison of several observables with measurements in e+e- collisions at the Z peak. Although a fine tuning of the model parameters is not carried out, a general good agreement between its predictions and data is found.Comment: 19 pages, 28 figures, 6 tables. v2: added sections on comparison between the Statistical Hadronization Model and the Cluster Model and on the interplay between Herwig cluster splitting algorithm and Statistical Hadronization Model predictions. Fixed typos and references added. Version accepted for publication in EPJ