Rapidity gap survival in the black-disk regime

We summarize how the approach to the black-disk regime (BDR) of strong interactions at TeV energies influences rapidity gap survival in exclusive hard diffraction pp -> p + H + p (H = dijet, Qbar-Q, Higgs). Employing a recently developed partonic description of such processes, we discuss (a) the suppression of diffraction at small impact parameters by soft spectator interactions in the BDR; (b) further suppression by inelastic interactions of hard spectator partons in the BDR; (c) correlations between hard and soft interactions. Hard spectator interactions substantially reduce the rapidity gap survival probability at LHC energies compared to previously reported estimates.Comment: 4 pages, 3 figures. Proceedings of XV International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS 2007), Munich, Germany, Apr. 16-20, 200

Transverse imaging of the proton in exclusive diffractive pp scattering

In a recent paper (hep-ph/0608271) we describe a new approach to rapidity gap survival (RGS) in the production of high-mass systems (H = dijet, Higgs, etc.) in exclusive double-gap diffractive pp scattering, pp -> p + H + p. It is based on the idea that hard and soft interactions are approximately independent (QCD factorization), and allows us to calculate the RGS probability in a model-independent way in terms of the gluon generalized parton distributions (GPDs) in the colliding protons and the pp elastic scattering amplitude. Here we focus on the transverse momentum dependence of the cross section. By measuring the "diffraction pattern," one can perform detailed tests of the interplay of hard and soft interactions, and even extract information about the gluon GPD in the proton from the data.Comment: 4 pages, 2 figures, uses ws-procs9x6.cls. Proceedings of XIV International Workshop on Deep Inelastic Scattering (DIS2006), Tsukuba City, Japan, Apr 20 - 24, 200

The Inclusive-Exclusive Connection and the Neutron Negative Central Charge Density

We find an interpretation of the recent finding that the central charge density of the neutron is negative by using models of generalized parton distributions at zero skewness to relate the behavior of deep inelastic scattering quark distributions, evaluated at large values of Bjorken x, to the transverse charge density evaluated at small distances. The key physical input of these models is the Drell-Yan-West relation We find that the d quarks dominate the neutron structure function for large values of Bjorken x, where the large longitudinal momentum of the struck quark has a significant impact on determining the center-of-momentum of the system, and thus the "center" of the nucleon in the transverse position plane.Comment: 17 pages, 8 figures. Text of an invited talk presented by G. A. Miller at the 2008 Division of Nuclear Physics Meeting in Oakland. Prepared for Int. Journ. Mod. Phys.

Conformational transformations induced by the charge-curvature interaction at finite temperature

The role of thermal fluctuations on the conformational dynamics of a single closed filament is studied. It is shown that, due to the interaction between charges and bending degrees of freedom, initially circular aggregates may undergo transformation to polygonal shape. The transition occurs both in the case of hardening and softening charge-bending interaction. In the former case the charge and curvature are smoothly distributed along the chain while in the latter spontaneous kink formation is initiated. The transition to a non-circular conformation is analogous to the phase transition of the second kind.Comment: 23 pages (Latex), 10 figures (Postscript), 2 biblio file (bib-file and bbl-file

Detection of human influence on a new, validated 1500-Year temperature reconstruction

Climate records over the last millennium place the twentieth-century warming in a longer historical context. Reconstructions of millennial temperatures show a wide range of variability, raising questions about the reliability of currently available reconstruction techniques and the uniqueness of late-twentieth-century warming. A calibration method is suggested that avoids the loss of low-frequency variance. A new reconstruction using this method shows substantial variability over the last 1500 yr. This record is consistent with independent temperature change estimates from borehole geothermal records, compared over the same spatial and temporal domain. The record is also broadly consistent with other recent reconstructions that attempt to fully recover low-frequency climate variability in their central estimate. High variability in reconstructions does not hamper the detection of greenhouse gas-induced climate change, since a substantial fraction of the variance in these reconstructions from the beginning of the analysis in the late thirteenth century to the end of the records can be attributed to external forcing. Results from a detection and attribution analysis show that greenhouse warming is detectable in all analyzed high-variance reconstructions (with the possible exception of one ending in 1925), and that about a third of the warming in the first half of the twentieth century can be attributed to anthropogenic greenhouse gas emissions. The estimated magnitude of the anthropogenic signal is consistent with most of the warming in the second half of the twentieth century being anthropogenic

Izazov eksperimenata virtualnog Comptonovog raspršenja iznad 8 GeV

We discuss the experimental issues confronting measurements of the virtualCompton-scattering (VCS) reaction ep→epγ with electron beams of energy 6 – 30 GeV. We specifically address the kinematics of deeply-virtual-Comptonscattering (deep inelastic scattering, with coincident detection of the exclusive real photon nearly parallel to the virtual photon direction) and large transverse momentum VCS (high energy VCS of arbitrary Q2, and the recoil proton emitted with high-momentum transverse to the virtual photon direction). We discuss the experimental equipment necessary for these measurements. For the deeply virtual Compton scattering, we emphasize the importance of the Bethe-Heitler – Compton interference terms that can be measured with the electron-positron (beam charge) asymmetry, and the electron beam helicity asymmetryRaspravljamo teško´ce s kojima se sučeljavaju mjerenja reakcija virtualnog Comptonovog raspršenja (VCS) ep→epγ pri energijama elektrona od 6 do 30 GeV. Posebno se razmatra kinematika duboko virtualnog Comptonovog raspršenja i VCS s velikim prijenosom impulsa. Raspravljamo mjerne uređaje koji su potrebni za takva mjerenja. Za duboko virtualno Comptonovo raspršenje, naglašavamo važnost Bethe-Heitlerovih interferentnih članova koji se mogu mjeriti asimetrijom elektronpozitron (naboj snopa) i asimetrijom heliciteta elektronskog snopa

Izazov eksperimenata virtualnog Comptonovog raspršenja iznad 8 GeV

We discuss the experimental issues confronting measurements of the virtualCompton-scattering (VCS) reaction ep→epγ with electron beams of energy 6 – 30 GeV. We specifically address the kinematics of deeply-virtual-Comptonscattering (deep inelastic scattering, with coincident detection of the exclusive real photon nearly parallel to the virtual photon direction) and large transverse momentum VCS (high energy VCS of arbitrary Q2, and the recoil proton emitted with high-momentum transverse to the virtual photon direction). We discuss the experimental equipment necessary for these measurements. For the deeply virtual Compton scattering, we emphasize the importance of the Bethe-Heitler – Compton interference terms that can be measured with the electron-positron (beam charge) asymmetry, and the electron beam helicity asymmetryRaspravljamo teško´ce s kojima se sučeljavaju mjerenja reakcija virtualnog Comptonovog raspršenja (VCS) ep→epγ pri energijama elektrona od 6 do 30 GeV. Posebno se razmatra kinematika duboko virtualnog Comptonovog raspršenja i VCS s velikim prijenosom impulsa. Raspravljamo mjerne uređaje koji su potrebni za takva mjerenja. Za duboko virtualno Comptonovo raspršenje, naglašavamo važnost Bethe-Heitlerovih interferentnih članova koji se mogu mjeriti asimetrijom elektronpozitron (naboj snopa) i asimetrijom heliciteta elektronskog snopa