A Search for excited fermions in electron - proton collisions at HERA

A search for excited states of the standard model fermions was performed using the ZEUS detector at the HERA electron-proton collider, operating at a centre of mass energy of 296 GeV. In a sample corresponding to an integrated luminosity of 0.55 pb(-1), no evidence was found for any resonant state decaying into final states composed of a fermion and a gauge boson. Limits on the coupling strength times branching ratio of excited fermions are presented for masses between 50 GeV and 250 GeV, extending previous search regions significantly

A search for excited fermions in electron-proton collisions at HERA

A search for excited states of the standard model fermions was performed using the ZEUS detector at the HERA electron-proton collider, operating at a centre of mass energy of 296 GeV. In a sample corresponding to an integrated luminosity of 0.55 pb−1, no evidence was found for any resonant state decaying into final states composed of a fermion and a gauge boson. Limits on the coupling strength times branching ratio of excited fermions are presented for masses between 50 GeV and 250 GeV, extending previous search regions significantly

Diffractive hard photoproduction at HERA and evidence for the gluon content of the pomeron

Inclusive jet cross sections for events with a large rapidity gap with respect to the proton direction from the reaction $ep \rightarrow jet \; + \; X$ with quasi-real photons have been measured with the ZEUS detector. The cross sections refer to jets with transverse energies $E_T^{jet}>8$~GeV. The data show the characteristics of a diffractive process mediated by pomeron exchange. Assuming that the events are due to the exchange of a pomeron with partonic structure, the quark and gluon content of the pomeron is probed at a scale $\sim (E_T^{jet})^2$. A comparison of the measurements with model predictions based on QCD plus Regge phenomenology requires a contribution of partons with a hard momentum density in the pomeron. A combined analysis of the jet cross sections and recent ZEUS measurements of the diffractive structure function in deep inelastic scattering gives the first experimental evidence for the gluon content of the pomeron in diffractive hard scattering processes. The data indicate that between 30\% and 80\% of the momentum of the pomeron carried by partons is due to hard gluons.Comment: 25 pages, latex, 4 figures appended as uuencoded file. No change w.r.t. previous version (just avoiding warning latex messages while processing

The Unquantified Risk of Post-Fire Metal Concentration in Soil: a Review

Forest fire is a natural disturbance that occurs in many terrestrial ecosystems specifically in the semi-arid environments and is considered to be an important cause of environmental change. Though many causes of fire are identified, including lightning, volcanic eruption, power line sparks, etc., human involvement is the most significant factor. Fire events are able to alter the physical, chemical and biogeochemical properties of the soil and surface materials and are able to release major and trace metals into the environment. This may be more significant in mining-affected and industrial landscapes, where elevated concentrations of metals present in the soil. After the fire event, metals become more mobile due to the increase in soil surface exposure and the mobility associated with ash dispersal. This mobility may increase the bioavailability of the metals, which may generate water quality issues and may contribute to human and environmental health concerns. Even though, the influences of fire on many soil properties are well established, the behaviour of metals with respect to fire is not well investigated. However, a few studies report that major and trace metals include Cd, Cr, Co, Cu, Hg, Mn, Ni, Pb, Zn and As are mobilized after fire with increased concentrations in soil and water resources and this might pose a risk to human health and ecosystems. Climate change may increase the intensity, frequency and areal extend of fire events and hence increase the metal concentrations and their potential health impacts. This paper reviews post-fire (wild fire) mobility of metals in soil common in contaminated forest ecosystems. The human and ecological health risks of these metals are also considered. © 2017, Springer International Publishing Switzerland