A description of the ratio between electric and magnetic proton form factors by using space-like, time-like data and dispersion relations

We use the available information on the ratio between the electric and magnetic proton form factors coming from recently published space-like data and from the few available time-like data. We apply a dispersive procedure on these data to evaluate the behaviour of this ratio, as a complex function, for all values of q^2.Comment: 12 pages, 7 Encapsulated Postscript figures, uses epsfig, rotating, exscale, amsmath, cite, latexsym, graphics, color packages, added reference

Stress Response to Winter Warfare Training: Potential Impact of Location

Winter Warfare Training (WWT) is a critical component of military training to prepare individuals to move effectively in harsh conditions. Moving through snow and heavy terrain increases overall stress to the entire human system. PURPOSE: The purpose of this effort was to quantify the stress response during WWT to determine the level of physiological adaptation to extreme environments. METHODS: Mountain and mobility operators (age: 31.5±1.4 years; height: 71.1±0.5 inches; weight: 192.5±6.6 lbs.; body fat percentage: 18.0±5.0%) were recruited for this effort. Participants engaged in baseline laboratory metrics at their home station located in Colorado (CO) prior to WWT for one week in Montana (MT) and one week in Alaska (AK). WWT was separated by approximately one month. Blood was collected upon wake on the first and last day at each location. Plasma was analyzed for anabolic and stress-related hormones via enzyme-linked immunoassay (ELISA). RESULTS: Plasma adrenocorticotropic hormone (ACTH) levels increased from baseline to pre- (p=0.004), decreased from pre- to post-WWT in MT (p=0.004), and increased in from pre- to post-WWT in AK (p=0.005). Plasma cortisol levels decreased from pre- to post-WWT in MT (p=0.001) and, conversely, increased from pre- to post-WWT in AK (pCONCLUSION: The increase in stress-related hormones (i.e., ACTH and cortisol) exhibited throughout during WWT in AK suggest that operators experienced heightened physiological strain during WWT in AK compared to MT, despite similar training. We speculate that differences in sleep environment, changes in environmental temperature and terrain between MT and AK, and cumulative training load may have exacerbated the overall physiological strain on the operators

All electromagnetic form factors

The electromagnetic form factors of spin-1/2 particles are known, but due to historical reasons only half of them are found in many textbooks. Given the importance of the general result, its model independence, its connection to discrete symmetries and their violations we made an effort to derive and present the general result based only on the knowledge of Dirac equation. We discuss the phenomenology connected directly with the form factors, and spin precession in external fields including time reversal violating terms. We apply the formalism to spin-flip synchrotron radiation and suggest pedagogical projects.Comment: Latex, 22 page

Nucleon electromagnetic form factors

Elastic electromagnetic nucleon form factors have long provided vital information about the structure and composition of these most basic elements of nuclear physics. The form factors are a measurable and physical manifestation of the nature of the nucleons' constituents and the dynamics that binds them together. Accurate form factor data obtained in recent years using modern experimental facilities has spurred a significant reevaluation of the nucleon and pictures of its structure; e.g., the role of quark orbital angular momentum, the scale at which perturbative QCD effects should become evident, the strangeness content, and meson-cloud effects. We provide a succinct survey of the experimental studies and theoretical interpretation of nucleon electromagnetic form factors.Comment: Topical review invited by Journal of Physics G: Nuclear and Particle Physics; 34 pages (contents listed on page 34), 11 figure

Nucleon Form Factors - A Jefferson Lab Perspective

The charge and magnetization distributions of the proton and neutron are encoded in their elastic electromagnetic form factors, which can be measured in elastic electron--nucleon scattering. By measuring the form factors, we probe the spatial distribution of the proton charge and magnetization, providing the most direct connection to the spatial distribution of quarks inside the proton. For decades, the form factors were probed through measurements of unpolarized elastic electron scattering, but by the 1980s, progress slowed dramatically due to the intrinsic limitations of the unpolarized measurements. Early measurements at several laboratories demonstrated the feasibility and power of measurements using polarization degrees of freedom to probe the spatial structure of the nucleon. A program of polarization measurements at Jefferson Lab led to a renaissance in the field of study, and significant new insight into the structure of matter.Comment: 20 pages, 9 figures; Chapter in the book "A decade of Physics at Jefferson Lab", to be published in Journal of Physics: Conference Serie

Theoretical aspects of the CEBAF 89-009 experiment on inclusive scattering of 4.05 GeV electrons from nuclei

We compare recent CEBAF data on inclusive electron scattering on nuclei with predictions, based on a relation between structure functions (SF) of a nucleus, a nucleon and a nucleus of point-nucleons. The latter contains nuclear dynamics, e.g. binary collision contributions in addition to the asymptotic limit. The agreement with the data is good, except in low-intensity regions. Computed ternary collsion contributions appear too small for an explanation. We perform scaling analyses in Gurvitz's scaling variable and found that for $y_G\gtrless 0$, ratios of scaling functions for pairs of nuclei differ by less than 15-20% from 1. Scaling functions for $0$ are, for increasing $Q^2$, shown to approach a plateau from above. We observe only weak $Q^2$-dependence in FSI, which in the relevant kinematic region is ascribed to the diffractive nature of the NN amplitudes appearing in FSI. This renders it difficult to separate asymptotic from FSI parts and seriously hampers the extraction of $n(p)$ from scaling analyses in a model-independnent fashion.Comment: 11 p. Latex file, 2 ps fig

One-loop chiral amplitudes of Moller scattering process

The high energy amplitudes of the large angles Moller scattering are calculated in frame of chiral basis in Born and 1-loop QED level. Taking into account as well the contribution from emission of soft real photons the compact relations free from infrared divergences are obtained. The expressions for separate chiral amplitudes contribution to the cross section are in agreement with renormalization group predictions.Comment: 15 pages, 3 figure

GRS computation of deep inelastic electron scattering on 4He

We compute cross sections for inclusive scattering of high energy electrons on 4He, based on the two lowest orders of the Gersch-Rodriguez-Smith (GRS) series. The required one- and two-particle density matrices are obtained from non-relativistic 4He wave functions using realistic models for the nucleon-nucleon and three-nucleon interaction. Predictions for E=3.6 GeV agree well with the NE3 SLAC-Virginia data.Comment: 18 pages, 7 figures, submitted to PR

Transition between nuclear and quark-gluon descriptions of hadrons and light nuclei

We provide a perspective on studies aimed at observing the transition between hadronic and quark-gluonic descriptions of reactions involving light nuclei. We begin by summarizing the results for relatively simple reactions such as the pion form factor and the neutral pion transition form factor as well as that for the nucleon and end with exclusive photoreactions in our simplest nuclei. A particular focus will be on reactions involving the deuteron. It is noted that a firm understanding of these issues is essential for unraveling important structure information from processes such as deeply virtual Compton scattering as well as deeply virtual meson production. The connection to exotic phenomena such as color transparency will be discussed. A number of outstanding challenges will require new experiments at modern facilities on the horizon as well as further theoretical developments.Comment: 37 pages, 17 figures, submitted to Reports on Progress in Physic