Azimuthal Asymmetries: Access to Novel Structure Functions

One of the most interesting consequence of non-zero intrinsic transverse momentum of partons in the nucleon is the nontrivial azimuthal dependence of the cross section of hard scattering processes. Many of the observable asymmetries contain unknown functions which provide essential information on the quark and gluon structure. Several of them have been studied in the last few years; we discuss their qualitative and quantitative features in semi-inclusive DIS.Comment: 6 pages, LaTeX, 7 eps figures, Talk presented at the 15th International Spin Physics Symposium, Spin 2002, Brookhaven National Laboratory, September 9-14, 200

Influence of seed coat color on germination rate and seedling development of Trifolium repens. Is physiological dormancy possible?

Trifolium repens L. (var. Regal Ladino) is among the most used species of Italian legumes as fodder for pastures, for direct consumption, or as mowing for stocks and then pastures. The seed integument of Trifolium repens L. has different colors ranging from light yellow to dark brown. In this work, the physiology of germination of light-colored, light intermediate, dark and dark intermediate seeds was studied to highlight any difference in the percentage of seed germination and seedling development. The results showed a lower germination rate and a noticeable reduction of the root length in dark seeds compared to light seeds. In this context, tests to exclude a physiological dormancy of dark seeds were performed. Light microscope and scanning electron microscope observation were conducted to detect substantial differences in the structure and thickness of the integument and in the quality of reserves. Biochemical investigations have evidenced that total polyphenols content is similar in all the seeds categories, while higher amount of total flavonoids was detected in dark seeds. Total Polyphenols and flavonoids content decreased during germination in all seed groups

Mineral nutrients in soil and pea plants after exposition to TiO2 nanoparticles through a biosolid-amended soil

In addition to the benefits derived from nanotechnology, there is also concern about the potential risks of engineered nanoparticles (ENPs) when released into the environment. Their possible accumulation and effects in agricultural soils and Nanonnovation 2018 Conference & Exibition crops are closely linked to food and agriculture safety. Particular attention has been focused on the reuse of biosolids from wastewater treatment plants that are considered a cost-effective practice for the improvement of nutrients and organic matter in agricultural soils and, but also a sink of contaminants such as nanoparticles (NPs). TiO2NPs have a global production of about 10.000 tons/year and it are among the most extensively used ENPs. Moreover, dissimilar or inconclusive results have been reported concerning the impact of TiO2 NPs on the soil-crop system, thus more information regarding their behavior are necessary. This study aimed to evaluate the potential effects of TiO2 NPs (anatase and rutile) and larger particles (bulk) on the availability of soil nutrients and on the nutritional status of Pisum sativum plants, simulating low (80 mg/kg) and high load of TiO2 (800 mg/kg ) in a biosolid-amended soil. Treated soils were analyzed for N, P, K, Ca, Mg, Mn, Fe, Cu, Zn, soil microbial community, and plants grown in laboratory for 30d were analyzed for growth, pigments and mineral nutrition. Results showed that the treatment with TiO2 at macro- and nano-scale significantly reduced the availability of Mn, Fe and P in soils, this last more evident for the NPs treatments. Indeed, the soil bacterial diversity was reduced when the mixture of anatase and rutile were spiked in the biosolid-amended soil at high concentration. Moreover, the pea plants from treated soils showed an imbalance in the mineral nutrition, with reduction in the plant tissues of Mn and K and increase of N. This study pose a reflection on the use of biosolid, which could act as a vehicle for the spread and accumulation of ENPs in agro-ecosystems

Experimental Review of Baryons in the Nuclear Medium

Inclusive studies of nuclear photoabsorption have provided clear evidence of medium modifications but the results have not yet been explained in a model independent way. A deeper understanding of the situation is anticipated from a detailed experimental study of meson photoproduction from nuclei in exclusive reactions. Recent results on meson production in photonuclear experiments indicate a large difference between quasifree meson production from the nuclear surface and non-quasifree components.Comment: Proceedings Baryons200

Low energy onset of nuclear shadowing in photoabsorption

The early onset of nuclear shadowing in photoabsorption at low photon energies has recently been interpreted as a possible signature of a decrease of the rho meson mass in nuclei. We show that one can understand this early onset within simple Glauber theory if one takes the negative real part of the rho N scattering amplitudes into account, corresponding to a higher effective mass of the rho meson in nuclear medium.Comment: REVTEX, 9 pages, including 4 eps figure

Hadron formation in high energy photonuclear reactions

We present a new method to account for coherence length effects in a semi-classical transport model. This allows us to describe photo- and electroproduction at large nuclei (A>12) and high energies using a realistic coupled channel description of the final state interactions that goes beyond simple Glauber theory. We show that the purely absorptive treatment of the final state interactions can lead to wrong estimates of color transparency and formation time effects in particle production. As an example, we discuss exclusive rho^0 photoproduction on Pb at a photon energy of 7 GeV as well as K^+ production in the photon energy range 1-7 GeV.Comment: 14 pages, 6 figures, version published in Phys. Rev.

Performance of the Electromagnetic Calorimeter of the HERMES Experiment

The performance of the electromagnetic calorimeter of the HERMES experiment is described. The calorimeter consists of 840 radiation resistant F101 lead-glass counters. The response to positrons up to 27.5 GeV, the comparison between the measured energy and the momentum reconstructed from tracking, long-term stability, hadron rejection and neutral meson invariant mass reconstruction are shown.Comment: 22 pages, 13 figures, LaTeX, accepted by NI

Nuclear shadowing at low photon energies

We calculate the shadowing effect in nuclear photoabsorption at low photon energies (1-3 GeV) within a multiple scattering approach. We avoid some of the high energy approximations that are usually made in simple Glauber theory like the narrow width and the eikonal approximation. We find that the main contribution to nuclear shadowing at low energies stems from $\rho^0$ mesons with masses well below their pole mass. We also show that the possibility of scattering in non forward directions allows for a new contribution to shadowing at low energies: the production of neutral pions as intermediate hadronic states enhances the shadowing effect in the onset region. For light nuclei and small photon energies they give rise to about 30% of the total shadowing effect.Comment: RevTeX, 16 pages including 6 eps figures; new calculation of effective pion propagator, negligible effect on results; version to be published in Phys. Rev.

Photofission of heavy nuclei at energies up to 4 GeV

Total photofission cross sections for 238U, 235U, 233U, 237Np, 232Th, and natPb have been measured simultaneously, using tagged photons in the energy range Egamma=0.17-3.84 GeV. This was the first experiment performed using the Photon Tagging Facility in Hall B at Jefferson Lab. Our results show that the photofission cross section for 238U relative to that for 237Np is about 80%, implying the presence of important processes that compete with fission. We also observe that the relative photofission cross sections do not depend strongly on the incident photon energy over this entire energy range. If we assume that for 237Np the photofission probability is equal to unity, we observe a significant shadowing effect starting below 1.5 GeV.Comment: 4 pages of RevTex, 6 postscript figures, Submitted to Phys. Rev. Let

Photoproduction of mesons in nuclei at GeV energies

In a transport model that combines initial state interactions of the photon with final state interactions of the produced particles we present a calculation of inclusive photoproduction of mesons in nuclei in the energy range from 1 to 7 GeV. We give predictions for the photoproduction cross sections of pions, etas, kaons, antikaons, and $\pi^+\pi^-$ invariant mass spectra in ^{12}C and ^{208}Pb. The effects of nuclear shadowing and final state interaction of the produced particles are discussed in detail.Comment: Text added in summary in general reliability of the method, references updated. Phys. Rev. C (2000) in pres