arXiv subjects

Gordon P. Ramsey

Publications and source records attributed to Gordon P. Ramsey.

16 recordsLinked to original sources

arXiv2020

A First-Year Research Experience: The Freshman Project in Physics at Loyola University Chicago

Undergraduate research has become an essential mode of engaging and retaining students in physics. At Loyola University Chicago, first-year physics students have been participating in the Freshman Projects program for over twenty years, which has coincided with a period of significant growth for our department. In this paper, we describe how the Freshman Projects program has played an important role in advancing undergraduate research at Loyola, and the profound impact it has made on our program. We conclude with suggestions for adoption of similar programs at other institutions.

physics.ed-ph↗

arXiv2013

Physics Pedagogy and Assessment in Secondary Schools in the U.S.

The objective of this project is to compare the effectiveness of teaching styles used in high school physics classes and the methods used to assess them. We would like to determine those approaches to physics at the high schools that work and those that do not work for students from different demographics. We sent out a survey to high school physics teachers in the U.S. Midwest states, inquiring about student preparation, pedagogy in the classroom, assessment and professional development. We found that there are differences in the practices of physics teachers in all of these areas, depending on the school location, be it rural, suburban or urban. Our results enable us to report on the most common successful practices in physics courses for these demographic areas.

physics.ed-ph↗

arXiv2011

Studying Spin-Orbit Dynamics using Measurements of the Proton's Polarized Gluon Asymmetry

Measurements involving the gluon spin density, Delta G=G++ - G+-, can play an important role in the quantitative understanding of proton structure. To demonstrate this, we show that the shape of the gluon asymmetry, A(x,t)=Delta G(x,t)/G(x,t), contains significant dynamical information about non-perturbative spin-orbit effects. It is instructive to use a separation A(x,t)=A_0^epsilon(x)+epsilon(x,t), where A_0^epsilon(x) is an approximately scale-invariant form that can be calculated within a given factorization prescription from the measured distributions Delta q(x,t), q(x,t) and G(x,t). Applying this separation with the J_z=1/2 sum rule provides a convenient way to determine the total amount of orbital angular momentum generated by mechanisms associated with confinement and chiral dynamics. The results are consistent with alternate non-perturbative approaches to the determination of orbital angular momentum in the proton. Our studies help to specify the accuracy that future measurements should achieve to constrain theoretical models for nucleon structure.

hep-ph↗

arXiv2008

Spin-Orbit Dynamics from the Gluon Asymmetry

Determination of the orbital angular momentum of the proton is a difficult but important part of understanding fundamental structure. Insight can be gained from suitable models of the gluon asymmetry applied to the Jz = 1/2 sum rule. We have constrained the models of the asymmetry to gain possible scenarios for the angular momentum of the proton's constituents. Results and phenomenology for determining Lz are presented.

hep-ph↗

arXiv2006

Probing the Orbital Angular Momentum through the Polarized Gluon Asymmetry

The orbital angular momentum is one of the least understood of the spin characteristics of a proton. There are no direct ways to model the orbital angular momentum. However, the Jz=1/2 sum rule includes an angular momentum component and can provide indirect access to its properties. One of the other unknowns in the sum rule is the gluon polarization. We can define the gluon spin asymmetry in a proton as the ratio of the polarized to unpolarized gluon distributions. This can be written as a sum of a scale-invariant piece and a small scale-dependent term. The x-dependence of the asymmetry can be calculated and a suitable parametrization for scale-dependent term can be made to estimate this asymmetry. When combined with the measured unpolarized gluon density, this provides a model independent prediction for the polarized gluon distribution. This eliminates one unknown in the Jz=1/2 sum rule and allows a reasonable estimate for the size and evolution of the orbital angular momentum of the constituents.

hep-ph↗

arXiv2005

The Gluon Spin Asymmetry as a Link to Delta G and Orbital Angular Momentum

The fundamental program in high energy spin physics focuses on the spin structure of the nucleon. The gluon and orbital angular momentum components of the nucleon spin are virtually unknown. The J_z=1/2 sum rule involves the integrated parton densities and can be used to extract information on the orbital angular momentum and its evolution. To avoid any bias on a model of Delta G, we assume that the gluon asymmetry, A=Delta G/G can be used to extract Delta G over a reasonable kinematic region. Combining the results for Delta G with the evolution equations, we can determine a theoretical expression for the orbital angular momentum and its evolution.

hep-ph↗

arXiv2002

Determining Spin-Flavor Dependent Distributions

Many of the present and planned polarization experiments are focusing on determination of the polarized glue. There is a comparable set of spin experiments which can help to extract information on the separate flavor-dependent polarized distributions. This talk will discuss possible sets of experiments, some of which are planned at BNL, CERN, DESY and JHF, which can be used to determine these distributions. Comments will include the estimated degree to which these distributions can be accurately found.

hep-ph↗

arXiv2002

Polarized Parton Distributions and the Polarized Gluon Asymmetry

The flavor-dependent valence, sea quark and antiquark spin distributions can be determined separately from theoretical assumptions and experimental data. We have determined the valence distributions using the Bjorken sum rule and have extracted polarized sea distributions, assuming that the quarks and anti-quarks for each flavor are symmetric. Other experiments have been proposed which will allow us to completely break the SU(3) symmetry of the sea flavors. To create a physical model for the polarized gluons, we investigate the gluon spin asymmetry in a proton, $A_G(x,Q^2)={{ΔG(x,Q^2)}\over {G(x,Q^2)}}$. By assuming that htis is is approximately $Q^2$ invariant, we can completely determine the $x$-dependence of this asymmetry, which satisfies constituent counting rules and reproduces the basic results of the Bremsstrahlung model originated by Close and Sivers. This asymmetry can be combined with the measured unpolarized gluon density, $G(x,Q^2)$ to provide a prediction for $ΔG(x,Q^2)$. Existing and proposed experiments can test both the prediction of scale-invariance for $A_G(x,Q^2)$ and the nature of $ΔG$ itself. These models will be discussed along with suggestions for specific experiments which can be performed at energies typical of HERA, RHIC and LHC to determine these polarized distributions.

hep-ph↗

arXiv2001

The Shape and Experimental Tests of the Q^2-Invariant Polarized Gluon Asymmetry

The absence of "valence-gluon" degrees of freedom combined with an examination of radiative QCD diagrams leads to an implication that the gluon spin asymmetry in a proton, defined as A_G(x,Q^2) = (Delta G)/G, should be approximately Q^2 invariant. The condition for scale invariance completely determines the x-dependence of this asymmetry, which satisfies the constituent counting rules and reproduces the basic results of the Bremsstrahlung model originated by Close and Sivers. This asymmetry can be combined with the measured unpolarized gluon density, G(x,Q^2) to provide a prediction for Delta G(x,Q^2). Existing and proposed experiments can test both the prediction of scale invariance for A_G and the nature of Delta G itself.

hep-ph↗

arXiv2000

A Comparison of Spin Observable Predictions for RHIC

There have been many versions of spin-dependent parton distributions in the literature. Although most agree with present data within uncertainties, they are based upon different physical assumptions. Some physical models are discussed and the corresponding predictions for double spin asymmetries are shown. A summary of the most feasible measurements in the appropriate kinematic regions at RHIC, which should yield the most useful information about the polarized gluon distribution, is given.

hep-ph↗

arXiv1998

Polarized Parton Distributions for Spin Asymmetries

We have used QCD and polarized deep-inelastic scattering data to construct x-dependent polarized parton distributions. These flavor dependent distributions evolve under the NLO DGLAP equations, satisfy positivity constraints and agree well with the data. We perform all of the analysis in x-space, avoiding difficulties with moments, and use these distributions to predict spin observables. The small-x behavior is sensitive to the model for the polarized gluon distribution.

hep-ph↗

arXiv1998

x-Dependent Polarized Parton Distributions

Using QCD motivated and phenomenological considerations, we construct x- dependent polarized parton distributions, which evolve under GLAP evolution, satisfy DIS data and are within positivity constraints. Each flavor is done separately and the overall set can be used to predict polarization asymmetries for various processes. We perform our NLO analysis strictly in x space, avoiding difficulties in moment inversion. Small-x results and other physical considerations are discussed.

hep-ph↗

arXiv1997

Probing Nucleon Spin Structure

One of the important questions in high energy physics is the relation of quark and gluon spin to that of the nucleons which they comprise. Polarization experiments provide a mechanism to probe the spin properties of elementary particles and provide crucial tests of Quantum Chromodynamics (QCD). The theoretical and experimental status of this fundamental question will be reviewed in this paper.

hep-ph↗

arXiv1996

Polarized Parton Distributions: Theory and Experiments

I review the constituent contributions to the spin of the proton extracted from recent data at CERN, SLAC and DESY. The valence, sea quark and antiquark spin-weighted distributions are determined separately. The data appear to imply a small to moderate polarized gluon distribution, so that the anomaly term is not significant in determining these contributions. We have analyzed the consistency of the results obtained from various sets of data and the Bjorken Sum Rule. All data are consistent with the sum rule, but they differ in the contribution of the strange sea to proton spin. This and the remaining uncertainty in the polarized gluon distribution pose unanswered questions about hadronic spin. Further experiments are suggested which can extract information about the polarized gluon and sea to address these questions.

hep-ph↗

arXiv1996

Nucleon Spin Distributions From Recent SMC, SLAC and DESY Data

We have extracted polarized nucleon distributions from recent data at CERN, SLAC and DESY. The flavor-dependent valence and sea quark spin distributions are determined for each experiment. The up and down distributions are comparable, but the strange sea contribution determined from different experiments do not agree, even including higher order corrections. Only experiments sensitive to the polarized gluon and sea will reconcile these differences.

hep-ph↗

arXiv1995

What We Can Learn About Nucleon Spin Structure From Recent Data

We have used recent polarized deep-inelastic scattering data from CERN and SLAC to extract information about nucleon spin structure. We find that the SMC proton data, the E142 neutron data and the deuteron data from SMC and E143 give different results for fractions of the spin carried by each of the constituents. These appear to lead to two different and incompatible models for the polarized strange sea. The polarized gluon distribution occuring in the gluon anomaly does not have to be large in order to be consistent with either set of experimental data. However, it appears that the discrepancies in the implications of these data cannot be resolved with any simple theoretical arguments. We conclude that more experiments must be performed in order to adequately determine the fraction of spin carried by each of the nucleon constituents.

hep-ph↗