1,143 research outputs found
Diffraction and sigma(gamma*rho)
No full textSchildknecht D, Tentyukov M, Kuroda M, Surrow B. Diffraction and sigma(gamma*rho). ACTA PHYSICA POLONICA B. 2002;33(11):3431-3438.The empirical scaling law, wherein the total photo-absorption cross section depends on the single variable eta = (Q(2) + m(0)(2))/A(2)(W-2), provides em pirical evidence for saturation in the sense of sigma(gamma*p)(W-2, Q(2))/sigma(gammap)(W-2) --> 1 for W-2 --> infinity at fixed Q(2). The total photo-absorption cross section is related to elastic diffraction in terms of a sum rule. The excess of diffractive production over the elastic component is due to inelastic diffraction that contains the production of hadronic states of higher spins. Motivated by the diffractive mass spectrum, the Generalized Vector Dominance/Color Dipole Picture (GVD/CDP) is extended to successfully describe the DIS data in the full region of x 0, where the diffractive two-gluon exchange mechanism dominates
Low-x scaling in gamma*p total cross sections
No full textSchildknecht D, Surrow B, Tentyukov M. Low-x scaling in gamma*p total cross sections. PHYSICS LETTERS B. 2001;499(1-2):116-124.We show that the experimental data for the total virtual-photon proton cross section, sigma gamma *p(W-2,Q(2)) for x(bj) less than or similar to 0.1 lie on a universal curve, when plotted against eta = (Q(2) + m(0)(2))/Lambda (2)(W-2), where Lambda (2)(W-2) = C-l(W-2 + W-0(2))(C2) is determined by the parameters C-1, C-2 and W-0(2) . The observed scaling law follows from the generalized-vector-dominance/colour-dipole picture (GVD/CDP) of low-x deep inelastic scattering. (C) 2001 Elsevier Science B.V. All rights reserved
Scaling in gamma*p total cross-sections, saturation and the gluon density
No full textSchildknecht D, Surrow B, Tentyukov M. Scaling in gamma*p total cross-sections, saturation and the gluon density. MODERN PHYSICS LETTERS A. 2001;16(28):1829-1839.Including the new HERA data, the gamma *p total cross-section is analyzed in the generalized vector dominance/color-dipole picture (GVD/CDP) that contains scaling in eta = (Q(2) + m(0)(2))/Lambda (2)(W-2), where Lambda (2)(W-2) is an increasing function of W-2. At any Q(2), for W-2 --> infinity, the cross-sections for virtual and real photons become identical, sigma (gamma *p)(W-2, Q(2))/(sigma gammap)(W-2) --> 1. The gluon density deduced from the color-dipole cross-section fulfills the leading order DGLAP relationship. Evolution a la DGLAP breaks down for n less than or similar to 0.1
Vector-meson electroproduction from generalized vector dominance
No full textSchildknecht D, Schuler GA, Surrow B. Vector-meson electroproduction from generalized vector dominance. PHYSICS LETTERS B. 1999;449(3-4):328-338.Including destructively interfering off-diagonal transitions of diffraction-dissociation type, we arl ive at a formulation of GVD for exclusive vector-meson production in terms of a continuous spectral representation of dipole form. The transverse cross-section, sigma(T.gamma*p) (-->) (Vp), behaves asymptotically as 1/Q(4), while R-v equivalent to sigma(L.gamma*p --> Vp)/sigma(T.gamma*p --> Vp) becomes asymptotically constant. Contributions violating s-channel helicity conservation stay at the level established in low-energy photoproduction and diffractive hadron-hadron interactions. The data on rho(0)-meson production from the Fermilab E665 Collaboration and on phi- and rho(0)-meson production from HERA are found to be in agreement with these predictions. (C) 1999 Elsevier Science B.V. All rights reserved
The generalised vector dominance/colour-dipole picture of deep-inelastic scattering at low x
No full textCvetic G, Schildknecht D, Surrow B, Tentyukov M. The generalised vector dominance/colour-dipole picture of deep-inelastic scattering at low x. EUROPEAN PHYSICAL JOURNAL C. 2001;20(1):77-91.We give a detailed account of the recently formulated generalised vector dominance/colour-dipole picture (GVD/CDP) of deep-inelastic scattering at low x congruent to Q(2)/W-2, including photoproduction. The approach, based on gamma*(q (q) over bar) transitions, q (q) over bar propagation and diffractive (q (q) over bar) p scattering via the generic structure of the two-gluon exchange, provides a unique and quantitatively successful theory for the gamma *p total cross section, sigma (gamma *p)(W-2, Q(2)), at low x. The GVD/CDP is shown to imply the empirical low-x scaling law, sigma (gamma *p)(W-2,Q(2)) = sigma (gamma *p)(eta) with eta = (Q(2) + m(o)(2))/Lambda (2)(W-2), that was established by a model-independent analysis of the experimental data
Future prospects of di-jet production constraining Dg(x) at low x at STAR at RHIC
No full text© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial Share like Licence. One of the main objectives of the high-energy spin physics program at RHIC at BNL is the precis determination of the polarized gluon distribution function, δg(x). Polarized p+p collision at ps = 200GeV and at √ = 500GeV at RHIC provide an unique way to probe the proton spi structure. Inclusive measurements, such as inclusive jet and hadron production, have so far bee the prime focus of various results at radic; = 200GeV constraining δg(x) for 0:05 < x < 0:2. A recen global analysis provides for the first time evidence of a non-zero value of the gluon polarizatio 10:05 δg(x)dx (Q2 =10GeV2)=0:20+0:006+0.07 First results of di-jet production at ps=200Ge by the STAR collaboration will allow a better constraint of the underlying event kinematics. Extendin the current program to smaller values of x is a key goal for the future high-energy spi physics program at RHIC. Forward di-jet production measurements at STAR beyond the curren acceptance from 1< <+2 to +2:5< <+4, in particular those carried out atps=500GeV provides access to low x values at the level of 103 where current uncertainties of Dg(x) remai very large. Those measurements will eventually be complemented by a future Electron-Ion Collide facility probing δg(x) in polarized e+p collisions
Results on di-jet production and hadron production in collisions from the OPAL experiment at LEP
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