Measurement of (anti)deuteron and (anti)proton production in DIS at HERA

The first observation of (anti)deuterons in deep inelastic scattering at HERA has been made with the ZEUS detector at a centre-of-mass energy of 300--318 GeV using an integrated luminosity of 120 pb-1. The measurement was performed in the central rapidity region for transverse momentum per unit of mass in the range 0.3<p_T/M<0.7. The particle rates have been extracted and interpreted in terms of the coalescence model. The (anti)deuteron production yield is smaller than the (anti)proton yield by approximately three orders of magnitude, consistent with the world measurements.Comment: 26 pages, 9 figures, 5 tables, submitted to Nucl. Phys.

Forward jet production in deep inelastic ep scattering and low-x parton dynamics at HERA

Differential inclusive jet cross sections in neutral current deep inelastic ep scattering have been measured with the ZEUS detector. Three phase-space regions have been selected in order to study parton dynamics where the effects of BFKL evolution might be present. The measurements have been compared to the predictions of leading-logarithm parton shower Monte Carlo models and fixed-order perturbative QCD calculations. In the forward region, QCD calculations at order alpha_s^1 underestimate the data up to an order of magnitude at low x. An improved description of the data in this region is obtained by including QCD corrections at order alpha_s^2, which account for the lowest-order t-channel gluon-exchange diagrams, highlighting the importance of such terms in parton dynamics at low x.Comment: 25 pages, 4 figure

Deep inelastic inclusive and diffractive scattering at Q2Q^2 values from 25 to 320 GeV2^2 with the ZEUS forward plug calorimeter

Deep inelastic scattering and its diffractive component, $ep \to e^{\prime}\gamma^* p \to e^{\prime}XN$, have been studied at HERA with the ZEUS detector using an integrated luminosity of 52.4 pb$^{-1}$. The $M_X$ method has been used to extract the diffractive contribution. A wide range in the centre-of-mass energy $W$ (37 -- 245 GeV), photon virtuality $Q^2$ (20 -- 450 GeV$^2$) and mass $M_X$ (0.28 -- 35 GeV) is covered. The diffractive cross section for $2 < M_X < 15$ GeV rises strongly with $W$, the rise becoming steeper as $Q^2$ increases. The data are also presented in terms of the diffractive structure function, $F^{\rm D(3)}_2$, of the proton. For fixed $Q^2$ and fixed $M_X$, \xpom F^{\rm D(3)}_2 shows a strong rise as \xpom \to 0, where \xpom is the fraction of the proton momentum carried by the Pomeron. For Bjorken-$x < 1 \cdot 10^{-3}$, \xpom F^{\rm D(3)}_2 shows positive $\log Q^2$ scaling violations, while for $x \ge 5 \cdot 10^{-3}$ negative scaling violations are observed. The diffractive structure function is compatible with being leading twist. The data show that Regge factorisation is broken.Comment: 89 pages, 27 figure

Spectroscopic and theoretical studies on the excited state in diimine dithiolate complexes of platinum(II)

The photophysical properties of a series of Pt(N-N)(S-S) complexes have been studied where (N-N) is either an \u3b1,\u3b1\u2032-diimine or saturated diamine chelating ligand and (S-S) is either a dithiolate chelating ligand or two monothiolate ligands in order to determine the orbital composition of the excited state. The solvent dependence of the absorption spectra of these complexes and the temperature dependence of their emission intensities and lifetimes have been examined while the ligands have been systematically varied. The electronic spectra are found to be dependent on whether or not the nitrogen chelating ligand is unsaturated (contains a vacant \u3c0* orbital). All of the unsaturated diimine complexes show an intense solvatochromic band in the visible region of their electronic spectra which shifts to higher energy with increasing solvent polarity. In the related complexes in which a saturated diamine chelating ligand replaces the unsaturated diimine chelating ligand, no solvatochromism is observed. On the basis of the spectroscopic data, the lowest energy absorption band in the diimine complexes is assigned as a metal-dithiolate to \u3c0*(diimine) transition, whereas in the diamine complexes it is assigned as a metal-to-dithiolate MLCT transition. The only room-temperature emissive complexes are those that contain an \u3b1,\u3b1\u2032-diimine chelating ligand. The nature of the emission in these complexes at all temperatures depends on the dithiolate ligand, and the temperature dependence of the emission spectra has been examined. When (S-S) is the 1,2-dithiolate maleonitriledithiolate (mnt), the emission in rigid glass is structured and shows single exponential behavior with both emission intensity and lifetime, increasing with decreasing temperature. For the other (S-S) complexes studied, the emission in rigid glass shows evidence of multiple emitting states based on the observation that lifetimes increase while emission quantum yields decrease as the temperature is lowered. The nature of the HOMO and LUMO has been examined experimentally using cyclic voltammetry. On the basis of the electrochemical and spectroscopic data, the emission from all of the Pt(diimine)(S-S) complexes except those of mnt is assigned as a 3{d(Pt)/p(S)-\u3c0*(diimine)} transition, while, for the mnt complexes, it corresponds to a 3{d(Pt)/p(S)-\u3c0*(mnt)} transition. These assignments are supported by extended H\ufcckel molecular orbital calculations

The bond in the bacteriophage øX174 gene A protein-DNA complex is a tyrosyl-5'-phosphate ester

AbstractThe bacteriophage øX174 gene A protein cleaves the viral strand of the double-stranded replicative form (RF) DNA of the phage at a specific site, the origin. It leaves a free 3'-OH at nucleotide 4305 (G) of the øx DNA sequence and binds covalently to the DNA. The nature and position of the covalent bond have been determined using the octadecadesoxyribonucleotide CAACTTG[32P]ATATTAATAAC. This octadecamer, which corresponds to nucleotides 4299–4316 of øX viral DNA, is cleaved by gene A protein. Gene A protein is bound to the labelled phosphate via a tyrosyl residue, indicating that binding occurs to the nucleotide corresponding to 4306 (A) of the øX viral DNA strand.Bacteriophage øX174Gene A proteinDNA replicationProtein-DNA complexSynthetic oligonucleotideTyrosyl-5'-phosphate este