Small x nonlinear evolution with impact parameter and the structure function data

The nonlinear Balitsky-Kovchegov equation at small x is solved numerically, incorporating impact parameter dependence. Confinement is modeled by including effective gluon mass in the dipole evolution kernel, which regulates the splitting of dipoles with large sizes. It is shown, that the solution is sensitive to different implementations of the mass in the kernel. In addition, running coupling effects are taken into account in this analysis. Finally, a comparison of the calculations using the dipole framework with the inclusive data from HERA on the structure functions F2 and FL is performed.Comment: 19 pages, 11 figures. Minor revision. One reference added, two figures update

Numerical solution of the nonlinear evolution equation at small x with impact parameter and beyond the LL approximation

Nonlinear evolution equation at small x with impact parameter dependence is analyzed numerically. Saturation scales and the radius of expansion in impact parameter are extracted as functions of rapidity. Running coupling is included in this evolution, and it is found that the solution is sensitive to the infrared regularization. Kinematical effects beyond leading logarithmic approximation are taken partially into account by modifying the kernel which includes the rapidity dependent cuts. While the local nonlinear evolution is not very sensitive to these effects, the kinematical constraints cannot be neglected in the evolution with impact parameter.Comment: 22 pages, 37 figures, RevTe

Fluctuations, Saturation, and Diffractive Excitation in High Energy Collisions

Diffractive excitation is usually described by the Good--Walker formalism for low masses, and by the triple-Regge formalism for high masses. In the Good--Walker formalism the cross section is determined by the fluctuations in the interaction. In this paper we show that by taking the fluctuations in the BFKL ladder into account, it is possible to describe both low and high mass excitation by the Good--Walker mechanism. In high energy $pp$ collisions the fluctuations are strongly suppressed by saturation, which implies that pomeron exchange does not factorise between DIS and $pp$ collisions. The Dipole Cascade Model reproduces the expected triple-Regge form for the bare pomeron, and the triple-pomeron coupling is estimated.Comment: 20 pages, 12 figure

The response of benthic foraminifer, ostracod and mollusc assemblages to environmental conditions: a case study from the Camalti Saltpan (Izmir-Western Turkey)

The subject of this report is benthic foraminifer populations preserved in the saltpan of Camalti in the Province of Izmir. High salinity in certain habitats of Ammonia tepida Cushman may be the primary cause of the high rate of twins and triplets as well as other morphological abnormalities recorded within this species (50 % as compared to an anomaly rate of 1 % in normal marine waters). Thicker cyst membrane developing in extremely saline environments may encourage twins and other morphological deformities by denying free movement of the offspring. Ecological factors such as heavy metal contamination of ambient waters as well as contamination by other wastes are also not ruled out as leading to such developmental anomalies. Of the 27 collected samples, Number 5 (that is closest to the sea) includes the typical marine foraminifers. Nonion depressulum (Walker & Jacob), Ammonia tepida Cushman and Porosononion subgronosum(Egger) are the dominant species in other samples. A total of 63 abnormal individuals (8 triplets, 24 twins, and 31 morphological anomalies) was found within seven of the 27 samples collected. Ten samples contained freshwater ostracods: Darwinula stevensoni(Brady and Robertson), Leptocythere lacertosa Hirschmann, Cyprideis torasa (Jones), Cyprideis (C.) anatolica Bassiouni, and Loxochoncha elliptica Brady. Among these samples (some of which contained only a few species of ostracods - and those limited in number of offspring), one had an unusually high ratio of healthy foraminifers vs those with anomalies. Worthy of note in another sample was a high abundance of molluscs. Among pelecypods, were found Ostrea edulis Linné, Lucinella divaricata (Linné), Pseudocama gryphina Lamarck,Cerastoderma edule (Linné), and Scrobicularia plana da Costa; and among gastropods were identified Hydrobi (Hydrobia) acuta(Draparnaud), Rissoa labiosa (Montagu), R. parva (da Costa), R. violacea Desmarest, Pirenella conica (Blainville), Bittium desayesi(Cerulli and Irelli), B. lacteum Philippi and B. reticulatum Philippi

Energy Conservation and Saturation in Small-x Evolution

Important corrections to BFKL evolution are obtained from non-leading contributions and from non-linear effects due to unitarisation or saturation. It has been difficult to estimate the relative importance of these effects, as NLO effects are most easily accounted for in momentum space while unitarisation and saturation are easier in transverse coordinate space. An essential component of the NLO contributions is due to energy conservation effects, and in this paper we present a model for implementing such effects together with saturation in Mueller's dipole evolution formalism. We find that energy conservation severely dampens the small-x rise of the gluon density and, as a consequence, the onset of saturation is delayed. Using a simple model for the proton we obtain a reasonable qualitative description of the x-dependence of F2 at low Q^2 as measured at HERA even without saturation effects. We also give qualitative descriptions of the energy dependence of the cross section for gamma*-gamma* and gamma*-nucleus scattering

The 2500 yr long paleoseismological record of the Hazar Lake, East Anatolian fault, Turkey

Understanding the Irregularity of Seismic Cycles: A Case Study in Turke

Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes

Two-dimensional materials offer new opportunities for both fundamental science and technological applications, by exploiting the electron spin. While graphene is very promising for spin communication due to its extraordinary electron mobility, the lack of a band gap restricts its prospects for semiconducting spin devices such as spin diodes and bipolar spin transistors. The recent emergence of 2D semiconductors could help overcome this basic challenge. In this letter we report the first important step towards making 2D semiconductor spin devices. We have fabricated a spin valve based on ultra-thin (5 nm) semiconducting black phosphorus (bP), and established fundamental spin properties of this spin channel material which supports all electrical spin injection, transport, precession and detection up to room temperature (RT). Inserting a few layers of boron nitride between the ferromagnetic electrodes and bP alleviates the notorious conductivity mismatch problem and allows efficient electrical spin injection into an n-type bP. In the non-local spin valve geometry we measure Hanle spin precession and observe spin relaxation times as high as 4 ns, with spin relaxation lengths exceeding 6 um. Our experimental results are in a very good agreement with first-principles calculations and demonstrate that Elliott-Yafet spin relaxation mechanism is dominant. We also demonstrate that spin transport in ultra-thin bP depends strongly on the charge carrier concentration, and can be manipulated by the electric field effect

Electronic Spin Transport in Dual-Gated Bilayer Graphene

The elimination of extrinsic sources of spin relaxation is key in realizing the exceptional intrinsic spin transport performance of graphene. Towards this, we study charge and spin transport in bilayer graphene-based spin valve devices fabricated in a new device architecture which allows us to make a comparative study by separately investigating the roles of substrate and polymer residues on spin relaxation. First, the comparison between spin valves fabricated on SiO2 and BN substrates suggests that substrate-related charged impurities, phonons and roughness do not limit the spin transport in current devices. Next, the observation of a 5-fold enhancement in spin relaxation time in the encapsulated device highlights the significance of polymer residues on spin relaxation. We observe a spin relaxation length of ~ 10 um in the encapsulated bilayer with a charge mobility of 24000 cm2/Vs. The carrier density dependence of spin relaxation time has two distinct regimes; n<4 x 1012 cm-2, where spin relaxation time decreases monotonically as carrier concentration increases, and n>4 x 1012 cm-2, where spin relaxation time exhibits a sudden increase. The sudden increase in the spin relaxation time with no corresponding signature in the charge transport suggests the presence of a magnetic resonance close to the charge neutrality point. We also demonstrate, for the first time, spin transport across bipolar p-n junctions in our dual-gated device architecture that fully integrates a sequence of encapsulated regions in its design. At low temperatures, strong suppression of the spin signal was observed while a transport gap was induced, which is interpreted as a novel manifestation of impedance mismatch within the spin channel

Nanosecond spin lifetimes in single- and few-layer graphene-hBN heterostructures at room temperature

We present a new fabrication method of graphene spin-valve devices which yields enhanced spin and charge transport properties by improving both the electrode-to-graphene and graphene-to-substrate interface. First, we prepare Co/MgO spin injection electrodes onto Si$^{++}$/SiO$_2$. Thereafter, we mechanically transfer a graphene-hBN heterostructure onto the prepatterned electrodes. We show that room temperature spin transport in single-, bi- and trilayer graphene devices exhibit nanosecond spin lifetimes with spin diffusion lengths reaching 10$\mu$m combined with carrier mobilities exceeding 20,000 cm$^2$/Vs.Comment: 15 pages, 5 figure

Assessment of Lake Sediment Sensitivity to Earthquakes and Climate Cycles along the North Anatolian Fault,

Understanding the irregularity of seismic cycles: A case study in Turke