The GridPP Collaboration is building a UK computing Grid for particle physics, as part of the international effort towards computing for the Large Hadron Collider. The project, funded by the UK Particle Physics and Astronomy Research Council (PPARC), began in September 2001 and completed its first phase 3 years later. GridPP is a collaboration of approximately 100 researchers in 19 UK university particle physics groups, the Council for the Central Laboratory of the Research Councils and CERN, reflecting the strategic importance of the project. In collaboration with other European and US efforts, the first phase of the project demonstrated the feasibility of developing, deploying and operating a Grid-based computing system to meet the UK needs of the Large Hadron Collider experiments. This note describes the work undertaken to achieve this goal.

The reactions of aqueous ClO2 With tyrosine, N-acetyltyrosine, and dopa (3,4-dihydroxyphenylalanine) are investigated from pH 4 to 7. The reaction rates increase greatly with pH to give a series of oxidized products. Tyrosine and N-acetyltyrosine have similar reactivities with second-order rate constants (25.0 degrees C) for their phenoxide forms equal to 1.8 x 10(8) and 7.6 x 10(7) M-1 s(-1), respectively. Both species generate phenoxyl radicals that react rapidly with a second ClO2 at the 3 position to give observable but short-lived adducts with proposed C(H)-OClO bonding. The decay of these phenoxyl-ClO2 adducts also is rapid and is base-assisted to form dopaquinone (from tyrosine) and N-acetyldopaquinone (from N-acetyltyrosine) as initial products. The consumption Of two ClO2 molecules corresponds to a four-electron oxidation that gives ClO2- in the first step and HOCl in the second step. The reaction between ClO2 and the deprotoned-catechol form of dopa is extremely fast (2.8 x 10(9) M-1 s(-1)). Dopa consumes two ClO2 to give dopaquinone and 2ClO(2)(-) as products. Above pH 4, dopaquinone cyclizes to give cyclodopa, which in turn is rapidly oxidized to dopachrome. A resolved first-order rate constant of 249 s(-1) is evaluated for the cyclization of the basic form of dopaquinone that leads to dopachrome as a product with strong absorption bands at 305 and 485 nm.

Self-decomposition of the nickel(III) doubly deprotonated peptide complex of Gly2HisGly occurs by base-assisted oxidation of the peptide. At < or =p[H+] 7.0, the major pathway is a four-electron oxidation (via 4 Ni(III) complexes) at the alpha carbon of the N-terminal glycyl residue. The product of this oxidation is oxamylglycylhistidylglycine, which hydrolyzes to yield ammonia and oxalylglycylhistidylglycine. Both of these peptide products decompose to give isocyanatoacetylhistidylglycine. A small amount (2%) of oxidative decarboxylation also is observed. In another major pathway above p[H+] 7.0, two Ni(III)-peptide complexes coordinate via an oxo bridge in the axial positions to form a reactive dimer species. This dimer generates two Ni(II)-peptide radical intermediates that cross-link at the alpha carbons of the N-terminal glycyl residues. In 0.13 mM Ni(III)-peptide at p[H+] 10.3, this pathway accounts for 60% of the reaction. The cross-linked peptide is subject to oxidation via atmospheric O2, where the 2,3-diaminobutanedioic acid is converted to a 2,3-diaminobutenedioic acid. The products observed at <p[H+] 7.0 are observed here as well, although in lower yields. The reactivity of Ni(III)(H(-2)Gly2HisGly) is significantly different than that of Cu(III)(H(-2)Gly2HisGly), which undergoes a two-electron oxidation at the histidyl residue with no peptide-peptide cross-linking in basic solution.

The decomposition kinetics of the Ni(III) complexes of Gly(2)HisGly and Gly(2)Ha are studied from p[H(+)] 3.5 to 10, where His is l-histidine and Ha is histamine. In these redox reactions, at least two Ni(III) complexes are reduced to Ni(II) while oxidizing a single peptide ligand. The rate of Ni(III) loss is first order at low pH, mixed order from pH 7.0 to 8.5, and second order at higher pH. The transition from first- to second-order kinetics is attributed to the formation of an oxo-bridged Ni(III)-peptide dimer. The rates of decay of the Ni(III) complexes are general-base assisted with Brønsted beta values of 0.62 and 0.59 for Ni(III)Gly(2)HisGly and Ni(III)Gly(2)Ha, respectively. The coordination of Gly(2)HisGly and Gly(2)Ha to Ni(II) are examined by UV-vis and CD spectroscopy. The square planar Ni(II)(H(-2)Gly(2)HisGly)(-) and Ni(II)(H(-2)Gly(2)Ha) complexes lose an additional proton from an imidazole nitrogen at high pH with pK(a) values of 11.74 and 11.54, respectively. The corresponding Ni(III) complexes have axially coordinated water molecules with pK(a) values of 9.37 and 9.44. At higher pH an additional proton is lost from the imidazole nitrogen with a pK(a) value of 10.50 to give Ni(III)(H(-3)Gly(2)Ha)(H(2)O)(OH)(2-).

The doubly-deprotonated Ni(III) complex of Gly(2)Ha (where Ha is histamine) undergoes base-assisted oxidative self-decomposition of the peptide. At </= p[H(+)] 7.0, a major pathway is a two-electron oxidation at the alpha-carbon of the N-terminal glycyl residue. Major products (up to 73%) of this two-electron oxidation are glyoxylglycylhistamine and ammonia. Glyoxylglycylhistamine will decay to give isocyanatoacetylhistamine and formaldehyde. Two-electron oxidations of the second glycyl and histamine residues occur as minor pathways (12% of the total possible reaction). Above p[H(+)] 8.5, two Ni(III)-peptide complexes form an oxo bridge in the axial positions to give a reactive dimer species. This proximity allows the resulting Ni(II)-peptide radical intermediates to undergo peptide-peptide cross-linking at the N-terminal glycyl residues. The products found below p[H(+)] 7.0 are observed above p[H(+)] 8.5 as well, although in lower yields. In contrast to this work, Ni(III)(H(-2)Gly(2)HisGly) undergoes a four-electron oxidation at the N-terminal glycyl residue. Oxidation at the internal glycyl and histidyl residues are not observed. The reactivity of Ni(III)(H(-2)Gly(2)Ha)(+) is also different than Cu(III)(H(-2)Gly(2)Ha)(+), which undergoes a two-electron oxidation at the histamine group with no peptide-peptide cross-linking in basic solution.

For the ATLAS experiment at the Large Hadron Collider (LHC) buffers are required which will accept data at rates in excess of 100 Mbytes/s and distribute selected data to the second and third level trigger systems. A design for a buffer using a digital signal processor as the memory manager is described and the performance of a prototype module is given. Tests of the system in a beam line will be used to develop and check discrete event simulation models of the buffers and a second level trigger system.

The performance of the ALEPH detector at the LEP e+e− collider is reviewed. The accuracy of the tracking detectors to measure the impact parameter and momentum of charged tracks is specified. Calorimeters are used to measure photons and neutral hadrons, and the accuracy obtained in energy and angle is given. An essential property of the detector is its ability to identify particles; the performance in identification of electrons, muons, neutrinos (from missing energy), charged hadrons, π0's and V0's is described.

The ratios of the numbers of Z bosons decaying to e+e−, μ+μ− and τ+τ− pairs to the number decaying to hadrons have been measured. The branching ratios and partial widths for each channel were determined and found to be equal, consistent with lepton universality. The mean leptonic branching ratio was found to be 0.0321 ± 0.0013 and the leptonic partial width to be 85.4 ± 5.3 MeV. The partial widths for hadronic decays and for invisible decays were deduced to be 1833 ± 116 MeV and 569 ± 92 MeV, respectively. The number of light neutrino types, assuming only the standard model value for the ratio ΘeΘv, was found to be 3.35 ± 0.41.

We have performed a search for supersymmetric particles using acoplanar pairs of oppositely-charged particles in decays of the Z0. In 0.53 pb−1 of integrated luminosity near the Z0 peak, we observe two events where approximately four are expected from background, allowing limits to be extended on combined photino and slepton masses, and also on combined photino and chargino masses.