Simulations of Time-Resolved X-Ray Diffraction in Laue Geometry

A method of computer simulation of Time-Resolved X-ray Diffraction (TRXD) in asymmetric Laue (transmission) geometry with an arbitrary propagating strain perpendicular to the crystal surface is presented. We present two case studies for possible strain generation by short-pulse laser irradiation: (i) a thermoelastic-like analytic model; (ii) a numerical model including effects of electron-hole diffusion, Auger recombination, deformation potential and thermal diffusion. A comparison with recent experimental results is also presented.Comment: 9 pages, 11 figure

Heavy Quark Fragmentation into Heavy Mesons

We present a QCD based interpretation of heavy quark fragmentation which utilizes the heavy quark mass expansion. By distinguishing between perturbative and non-perturbative QCD effects, we show how to reliably extract mass independent parameters characterizing the fragmentation function. Because these parameters are quark mass independent, this procedure should permit tests of heavy quark symmetry. Furthermore, we show that heavy quark mass corrections vanish at order $m^2/Q^2$ in QCD. There also exist higher twist corrections of order $\Lambda m/Q^2$ and ${\alpha_{QCD}\over\pi} {m^2\over Q^2} \ln (Q^2/m^2)$ which we relate to the leading twist fragmentation function.Comment: 36 pages (Plain TeX with a PostScript figure appended at end), MIT CTP #218

Energy Conservation Constraints on Multiplicity Correlations in QCD Jets

We compute analytically the effects of energy conservation on the self-similar structure of parton correlations in QCD jets. The calculations are performed both in the constant and running coupling cases. It is shown that the corrections are phenomenologically sizeable. On a theoretical ground, energy conservation constraints preserve the scaling properties of correlations in QCD jets beyond the leading log approximation.Comment: 11 pages, latex, 5 figures, .tar.gz version avaliable on ftp://www.inln.unice.fr

PLOS One: Development of a self-report instrument for measuring online teaching practices and discussion facilitation

Online learning in higher education has been increasing for many years. This is happening across all of higher education and it is happening more specifically within STEM fields. The growth of online learning has significantly accelerated the past couple of years during the COVID-19 pandemic as colleges and universities have sought ways to continue educating students while also keeping students, faculty and staff safe. As result, many college faculty and instructors across all fields of study including STEM fields have made and continue to make the transition to teaching online for the first time. Teaching in an online environment is different from traditional classroom teaching in many ways and presents a unique set of challenges to college instructors. This study documents the development of an instrument used for instructors to self-report their instructional techniques and practices. Data from 251 instructors is also used to examine how this instrument can be used to better understand particular practices, with a focus in this study on discussion facilitation. The results align with the Community of Inquiry framework, including indicating that teaching through discussion forums involves direct contribution and/or facilitation

Intermittency and Exotic Channels

It is pointed out that accurate measurements of short-range two-particle correlations in like-charge $K\pi$ and in $\pi^ 0\pi^ 0$ channels should be very helpful in determining the origin of the \lq\lq intermittency\rq\rq\ phenomenon observed recently for the like-charge pion pairs.Comment: 5 p., plain tex, preprint T94/078(Saclay), LPTHE 94/58(Orsay

Leptoquark production in ultrahigh-energy neutrino interactions revisited

The prospects for producing leptoquarks (LQs) in ultrahigh-energy (UHE) neutrino nucleon collisions are re-examined in the light of recent interpretations of HERA data in terms of leptoquark production. We update predictions for cross-sections for the production of first- and second-generation leptoquarks in UHE nu-N and nubar-N collisions including (i) recent experimental limits on masses and couplings from the LEP and TEVATRON colliders as well as rare processes, (ii) modern parton distributions, and (iii) radiative corrections to single leptoquark production. If the HERA events are due to an SU(2) doublet leptoquark which couples mainly to (e+,q) states, we argue that there are likely other LQ states which couple to neutrinos which are close in mass, due to constraints from precision electroweak measurements.Comment: 12 pages, LaTeX, 3 separate postscript figures. Added 1 reference plus discussion, updated another referenc

Method for Flavor Tagging in Neutral B Meson Decays

A method is proposed for tagging the flavor of neutral $B$ mesons in the study of CP-violating decay asymmetries. The method makes use of a possible difference in interactions in $B \pi$ or $B^* \pi$ systems with isospins 1/2 and 3/2, and would be particularly clean if the $I = 1/2$ systems can be detected as ``$B^{**}$'' resonances.Comment: Submitted to Phys. Rev. D. 11 pages, LaTeX, Technion-PH-92-40 / PITHA 92/39 / EFI 92-5