Exclusive ηc\eta_c photo- and electroproduction at HERA as a possible probe of the odderon singularity in QCD

Theory and phenomenology of the eta_c photo- and electroproduction is developed from the point of view of probing the odderon singularity in QCD which corresponds to the three gluon exchange mechanism. This mechanism leads to the cross-sections which are independent of W^2 for the exchange of three non-interacting gluons or exhibit increase with increasing W^2 (or 1/x) for the odderon intercept above unity. The \eta_c electroproduction in the three gluon exchange mechanism is shown to be entirely controlled by the transversely polarised virtual photons. The magnitude of the eta_c photoproduction cross-section is estimated to be around 11-45pb. The t-dependence of the differential cross-section is also discussed.Comment: 9 pages, LaTeX, uses epsfig.sty; Numerical error corrected. A factor of 1/3 missing in amplitude in Eq.(8) added. Obtained gamma p -> eta_c p cross-section smaller by a factor of 9 than in the original version of the paper. Figures 4 and 5 changed accordingl

Pomeron-Odderon interference effects in electroproduction of π+π−\pi^+ \pi^-

We review the results of our studies on the charge and the spin asymmetries in the electroproduction of $\pi^+ \pi^-$ which are the observables sensitive to the Pomeron-Odderon interference.Comment: 5 pages LATEX, Talk given by L.Sz. at the 9th Int. High-Energy Physics Conference QCD '02, Montpellier, France, 2-9th July 200

Nuclear Attenuation of high energy two-hadron system in the string model

Nuclear attenuation of the two-hadron system is considered in the string model. The two-scale model and its improved version with two different choices of constituent formation time and sets of parameters obtained earlier for the single hadron attenuation, are used to describe available experimental data for the $z$-dependence of subleading hadron, whereas satisfactory agreement with the experimental data has been observed. A model prediction for $\nu$-dependence of the nuclear attenuation of the two-hadron system is also presented.Comment: 8 page

Hunting the QCD-Odderon in hard diffractive electroproduction of two pions

Charge asymmetries in diffractive electroproduction of two mesons are proportional to the interference of Pomeron and Odderon exchange amplitudes. We calculate in the framework of QCD and in the Born approximation a forward-backward charge asymmetry which turns out to be sizable in a kinematical domain accessible to HERA experiments. We predict a distinctive dependence of this asymmetry on the invariant mass of the two pions. Testing this prediction is a crucial step in the discovery of the QCD-Odderon.Comment: 13 pages LATEX, 6 .eps figures, numerical error corrected, new figures,main conclusions not change

Application of the Two-Scale Model to the HERMES Data on Nuclear Attenuation

The Two-Scale Model and its improved version were used to perform the fit to the HERMES data for $\nu$ (the virtual photon energy) and z (the fraction of $\nu$ carried by hadron) dependencies of nuclear multiplicity ratios for $\pi^+$ and $\pi^-$ mesons electro-produced on two nuclear targets ($^{14}$N and $^{84}$Kr). The quantitative criterium $\chi ^2$ was used for the first time to analyse the results of the model fit to the nuclear multiplicity ratios data. The two-parameter's fit gives satisfactory agreement with the HERMES data. Best values of the parameters were then used to calculate the $\nu$- and $z$ - dependencies of nuclear attenuation for $\pi^0$, K$^+$, K$^-$ and $\bar{p}$ produced on $^{84}$Kr target, and also make a predictions for $\nu$, z and the Q$^2$ (the photon virtuality) - dependencies of nuclear attenuation data for those identified hadrons and nuclea, that will be published by HERMES

A global reanalysis of nuclear parton distribution functions

We determine the nuclear modifications of parton distribution functions of bound protons at scales $Q^2\ge 1.69$ GeV$^2$ and momentum fractions $10^{-5}\le x\le 1$ in a global analysis which utilizes nuclear hard process data, sum rules and leading-order DGLAP scale evolution. The main improvements over our earlier work {\em EKS98} are the automated $\chi^2$ minimization, simplified and better controllable fit functions, and most importantly, the possibility for error estimates. The resulting 16-parameter fit to the N=514 datapoints is good, $\chi^2/{\rm d.o.f}=0.82$. Within the error estimates obtained, the old {\em EKS98} parametrization is found to be fully consistent with the present analysis, with no essential difference in terms of $\chi^2$ either. We also determine separate uncertainty bands for the nuclear gluon and sea quark modifications in the large-$x$ region where they are not stringently constrained by the available data. Comparison with other global analyses is shown and uncertainties demonstrated. Finally, we show that RHIC-BRAHMS data for inclusive hadron production in d+Au collisions lend support for a stronger gluon shadowing at $x<0.01$ and also that fairly large changes in the gluon modifications do not rapidly deteriorate the goodness of the overall fits, as long as the initial gluon modifications in the region $x\sim 0.02-0.04$ remain small.Comment: 33 pages, 14 figure

Estimate of the Collins fragmentation function in a chiral invariant approach

We predict the features of the Collins function, which describes the fragmentation of a transversely polarized quark into an unpolarized hadron, by modeling the fragmentation process at a low energy scale. We use the chiral invariant approach of Manohar and Georgi, where constituent quarks and Goldstone bosons are considered as effective degrees of freedom in the non-perturbative regime of QCD. To test the approach we calculate the unpolarized fragmentation function and the transverse momentum distribution of a produced hadron, both of which are described reasonably well. In the case of semi-inclusive deep-inelastic scattering, our estimate of the Collins function in connection with the transversity distribution gives rise to a transverse single spin asymmetry of the order of 10%, supporting the idea of measuring the transversity distribution of the nucleon in this way. In the case of e+ e- annihilation into two hadrons, our model predicts a Collins azimuthal asymmetry of about 5%.Comment: 12 pages, 15 figures. Figs. 11-14 changed, minor changes in discussion, few typos fixed and some references added. Final version to appear in PR

Realtime monitoring of thrombus formation in vivo using a self-reporting vascular access graft

Background: Chronic kidney disease (CKD) affects 10% of the global population costing over a hundred billion dollars per annum and leading to increased risk of cardiovascular disease. Many patients with CKD require regular haemodialyses. Synthetic arteriovenous grafts (AVG) are increasingly used to provide rapid vascular connection for dialysis. Initially, they have excellent patency rates but are critically limited by neointimal hyperplasia at the venous anastomosis, which drives subsequent thrombosis, graft failure and death. Methods: Here, we describe a system in which electrical impedance spectroscopy sensors are incorporated circumferentially into the wall of a synthetic arteriovenous graft. This is combined with an implantable radiotelemetry system for data transmission outside the patient. The system was tested using monolayers of endothelial and smooth muscle cells as well as swine blood and clots with explanted human carotid artery plaques. Sensor testing was then performed in vitro and the device was implanted in vivo in female swine. Results: The device can wirelessly report the accumulation of biological material, both cells and blood. Differences are also detected when comparing controls with pathological atheroma. In swine differences between blockage formation in a graft were remotely obtained and wireless reported. Conclusions: Combining electrical impedance spectroscopy and an implantable radiotelemetry system enables graft surveillance. This has the potential to be used for early detection of venous stenosis and blood clot formation in real-time in vivo. In principle, the concept could apply to other cardiovascular diseases and vascular implantable devices

Predicting cardiovascular stent complications using self-reporting biosensors for noninvasive detection of disease

Self-reporting implantable medical devices are the future of cardiovascular healthcare. Cardiovascular complications such as blocked arteries that lead to the majority of heart attacks and strokes are frequently treated with inert metal stents that reopen affected vessels. Stents frequently re-block after deployment due to a wound response called in-stent restenosis (ISR). Herein, an implantable miniaturized sensor and telemetry system are developed that can detect this process, discern the different cell types associated with ISR, distinguish sub plaque components as demonstrated with ex vivo samples, and differentiate blood from blood clot, all on a silicon substrate making it suitable for integration onto a vascular stent. This work shows that microfabricated sensors can provide clinically relevant information in settings closer to physiological conditions than previous work with cultured cells

Quark fragmentation to π±\pi^{\pm}, π0\pi^{0}, K±K^{\pm}, pp and pˉ\bar{p} in the nuclear environment

The influence of the nuclear medium on lepto-production of hadrons was studied in the HERMES experiment at DESY in semi-inclusive deep-inelastic scattering of 27.6 GeV positrons off deuterium, nitrogen and krypton targets. The differential multiplicity for krypton relative to that of deuterium has been measured for the first time for various identified hadrons ($\pi^+$, $\pi^-$, $\pi^0$, $K^+$, $K^-$, $p$ and $\bar{p}$) as a function of the virtual photon energy $\nu$, the fraction $z$ of this energy transferred to the hadron, and the hadron transverse momentum squared $p_t^2$. The multiplicity ratio is strongly reduced in the nuclear medium at low $\nu$ and high $z$, with significant differences among the various hadrons. The distribution of the hadron transverse momentum is broadened towards high $p_t^2$ in the nuclear medium, in a manner resembling the Cronin effect previously observed in collisions of heavy ions and protons with nuclei.Comment: 8 pages, 5 figure