Biomedical subjects

Stanley J Brodsky

Publications and source records attributed to Stanley J Brodsky.

4 recordsLinked to original sources

PubMed2006

Hadronic spectra and light-front wave functions in holographic QCD.

We show how the string amplitude phi(z) defined on the fifth dimension in AdS5 space can be precisely mapped to the light-front wave functions of hadrons in physical space-time. We find an exact correspondence between the holographic variable z and an impact variable zeta, which represents the measure of transverse separation of the constituents within the hadrons. In addition, we derive effective four dimensional Schrödinger equations for the bound states of massless quarks and gluons which exactly reproduce the anti-de Sitter conformal field theory results and give a realistic description of the light-quark meson and baryon spectrum as well as the form factors for space-like Q2. Only one parameter which sets the mass scale, lambda(QCD), is introduced.

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PubMed2005

Hadronic spectrum of a holographic dual of QCD.

We compute the spectrum of light hadrons in a holographic dual of QCD defined on AdS5 x S5 which has conformal behavior at short distances and confinement at large interquark separation. Specific hadrons are identified by the correspondence of string modes with the dimension of the interpolating operator of the hadron's valence Fock state. Higher orbital excitations are matched quanta to quanta with fluctuations about the AdS background. Since only one parameter, the QCD scale Lambda(QCD), is used, the agreement with the pattern of physical states is remarkable. In particular, the ratio of delta to nucleon trajectories is determined by the ratio of zeros of Bessel functions.

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PubMed2005

Constraints on proton structure from precision atomic-physics measurements.

Ground-state hyperfine splittings in hydrogen and muonium are very well measured. Their difference, after correcting for magnetic moment and reduced mass effects, is due solely to proton structure-the large QED contributions for a pointlike nucleus essentially cancel. The rescaled hyperfine difference depends on the Zemach radius, a fundamental measure of the proton, computed as an integral over a product of electric and magnetic proton form factors. The determination of the Zemach radius, (1.019+/-0.016) fm, from atomic physics tightly constrains fits to accelerator measurements of proton form factors. Conversely, we can use muonium data to extract an experimental value for QED corrections to hydrogenic hyperfine data. There is a significant discrepancy between measurement and theory, in the same direction as a corresponding discrepancy in positronium.

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PubMed2003

Hunting for glueballs in electron-positron annihilation.

We calculate the cross section for the exclusive production of J(PC)=0(++) glueballs G0 in association with the J/psi in e(+)e(-) annihilation using the perturbative QCD factorization formalism. The required long-distance matrix element for the glueball is bounded by CUSB data from a search for resonances in radiative Upsilon decay. The cross section for e(+)e(-)-->J/psi+G0 at sqrt[s]=10.6 GeV is similar to exclusive charmonium-pair production e(+)e(-)-->J/psi+h for h=eta(c) and chi(c0), and is larger by a factor of 2 than that for h=eta(c)(2S). As the subprocesses gamma(*)-->(cc)(cc) and gamma(*)-->(cc)(gg) are of the same nominal order in perturbative QCD, it is possible that some portion of the anomalously large signal observed by Belle in e(+)e(-)-->J/psiX may actually be due to the production of charmonium-glueball J/psiG(J) pairs.

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