Al-rich spinel in primitive arc volcanics

Al-rich spinels (100Cr/(Cr + Al) 50 wt%) are common in alpine peridotites, both terrestrial and lunar mafic and ultramafic cumulates, and in certain metamorphic rocks, but they are apparently rare in terrestrial volcanic rocks. Here we describe the occurrence of Al-rich spinel inclusions in olivine phenocrysts in island are volcanic rocks from five new localities: Bukit Mapas (Sumatra) and eastern Ball in the Sunda are, and Epi, Merelava, and Ambrym islands in the Vanuatu are. More commonly, relatively Cr-rich spinels also occur as inclusions in the same olivine phenocrysts, and it appears that the Cr-poor aluminous spinels must be in disequilibrium with the host basaltic melts. In the rocks studied, Al-rich spinels also coexist with trapped silicate glasses and highly aluminous clinopyroxene in melt inclusions in olivine. This paragenesis suggests an origin involving contamination by localised Al-rich melt pockets as opposed to a xenocrystic origin. Two mechanisms to produce this high-Al melt in basaltic magma chambers are suggested: (1) localized high-Al melt production by complete breakdown of assimilated lower crustal gabbroic rocks. In this model the high-Al melt may crystallise Al-rich spinels which are subsequently trapped as solid inclusions by phenocryst phases of the host basaltic melt or may be trapped as melt inclusions in which Al-rich spinels and Al-rich clinopyroxene crystallise as daughter phases, and (2) incongruent breakdown of amphibole in amphibole-rich cumulates in sub-are, or sub-GIB volcano magma chambers. The latter reaction produces a melt with similar to 20-22% of Al2O3, aluminous clinopyroxene, Al-rich spinel and olivine. Mixing between these amphibole breakdown products and host basaltic melt may occur throughout the evolution of a magmatic system, but particularly during recharge with hot magnesian basalt batches. Aluminous spinels and aluminous clinopyroxene produced during amphibole breakdown, or perhaps crystallised from aluminous melt produced in the same reaction, are incorporated into the magma during recharge, and subsequently trapped, together with the coexisting Cr-spinels, by crystallising olivine and clinopyroxene

Observation of associated near-side and away-side long-range correlations in √sNN=5.02 TeV proton-lead collisions with the ATLAS detector

Two-particle correlations in relative azimuthal angle (Δϕ) and pseudorapidity (Δη) are measured in √sNN=5.02  TeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1  μb-1 of data as a function of transverse momentum (pT) and the transverse energy (ΣETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Δη|<5) “near-side” (Δϕ∼0) correlation that grows rapidly with increasing ΣETPb. A long-range “away-side” (Δϕ∼π) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ΣETPb, is found to match the near-side correlation in magnitude, shape (in Δη and Δϕ) and ΣETPb dependence. The resultant Δϕ correlation is approximately symmetric about π/2, and is consistent with a dominant cos⁡2Δϕ modulation for all ΣETPb ranges and particle pT

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

Measurement of the cross-section of high transverse momentum vector bosons reconstructed as single jets and studies of jet substructure in pp collisions at √s = 7 TeV with the ATLAS detector

This paper presents a measurement of the cross-section for high transverse momentum W and Z bosons produced in pp collisions and decaying to all-hadronic final states. The data used in the analysis were recorded by the ATLAS detector at the CERN Large Hadron Collider at a centre-of-mass energy of √s = 7 TeV;{\rm Te}{\rm V}$and correspond to an integrated luminosity of$4.6\;{\rm f}{{{\rm b}}^{-1}}$. The measurement is performed by reconstructing the boosted W or Z bosons in single jets. The reconstructed jet mass is used to identify the W and Z bosons, and a jet substructure method based on energy cluster information in the jet centre-of-mass frame is used to suppress the large multi-jet background. The cross-section for events with a hadronically decaying W or Z boson, with transverse momentum${{p}_{{\rm T}}}\gt 320\;{\rm Ge}{\rm V}$and pseudorapidity$|\eta |\lt 1.9$, is measured to be${{\sigma }_{W+Z}}=8.5\pm 1.7$ pb and is compared to next-to-leading-order calculations. The selected events are further used to study jet grooming techniques

Search for the neutral Higgs bosons of the minimal supersymmetric standard model in pp collisions at root s=7 TeV with the ATLAS detector

A search for neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) is reported. The analysis is based on a sample of proton-proton collisions at a centre-of-mass energy of 7TeV recorded with the ATLAS detector at the Large Hadron Collider. The data were recorded in 2011 and correspond to an integrated luminosity of 4.7 fb-1 to 4.8 fb-1. Higgs boson decays into oppositely-charged muon or τ lepton pairs are considered for final states requiring either the presence or absence of b-jets. No statistically significant excess over the expected background is observed and exclusion limits at the 95% confidence level are derived. The exclusion limits are for the production cross-section of a generic neutral Higgs boson, φ, as a function of the Higgs boson mass and for h/A/H production in the MSSM as a function of the parameters mA and tan β in the mhmax scenario for mA in the range of 90GeV to 500 GeV. Copyright CERN

Search for direct pair production of the top squark in all-hadronic final states in proton-proton collisions at s√=8 TeV with the ATLAS detector

The results of a search for direct pair production of the scalar partner to the top quark using an integrated luminosity of 20.1fb−1 of proton–proton collision data at √s = 8 TeV recorded with the ATLAS detector at the LHC are reported. The top squark is assumed to decay via t˜→tχ˜01 or t˜→ bχ˜±1 →bW(∗)χ˜01 , where χ˜01 (χ˜±1 ) denotes the lightest neutralino (chargino) in supersymmetric models. The search targets a fully-hadronic final state in events with four or more jets and large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits are reported in terms of the top squark and neutralino masses and as a function of the branching fraction of t˜ → tχ˜01 . For a branching fraction of 100%, top squark masses in the range 270–645 GeV are excluded for χ˜01 masses below 30 GeV. For a branching fraction of 50% to either t˜ → tχ˜01 or t˜ → bχ˜±1 , and assuming the χ˜±1 mass to be twice the χ˜01 mass, top squark masses in the range 250–550 GeV are excluded for χ˜01 masses below 60 GeV

Search for pair-produced long-lived neutral particles decaying to jets in the ATLAS hadronic calorimeter in ppcollisions at √s=8TeV

The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in 20.3fb−1of data collected in proton–proton collisions at √s=8TeV. This search is sensitive to long-lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is observed. Limits are reported on the product of the scalar boson production cross section times branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles. Limits are reported for boson masses from 100 GeVto 900 GeV, and a long-lived neutral particle mass from 10 GeVto 150 GeV

Search for R-parity-violating supersymmetry in events with four or more leptons in sqrt(s) =7 TeV pp collisions with the ATLAS detector

A search for new phenomena in final states with four or more leptons (electrons or muons) is presented. The analysis is based on 4.7 fb−1 of $\sqrt{s}=7\;\mathrm{TeV}$ proton-proton collisions delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in two signal regions: one that requires moderate values of missing transverse momentum and another that requires large effective mass. The results are interpreted in a simplified model of R-parity-violating supersymmetry in which a 95% CL exclusion region is set for charged wino masses up to 540 GeV. In an R-parity-violating MSUGRA/CMSSM model, values of m 1/2 up to 820 GeV are excluded for 10 < tan β < 40

Search for high-mass resonances decaying to dilepton final states in pp collisions at s√=7 TeV with the ATLAS detector

The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to an electron-positron pair or a muon-antimuon pair. The search is sensitive to heavy neutral Z′ gauge bosons, Randall-Sundrum gravitons, Z * bosons, techni-mesons, Kaluza-Klein Z/γ bosons, and bosons predicted by Torsion models. Results are presented based on an analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9 fb−1 in the e + e − channel and 5.0 fb−1 in the μ + μ −channel. A Z ′ boson with Standard Model-like couplings is excluded at 95 % confidence level for masses below 2.22 TeV. A Randall-Sundrum graviton with coupling k/MPl=0.1 is excluded at 95 % confidence level for masses below 2.16 TeV. Limits on the other models are also presented, including Technicolor and Minimal Z′ Models

Comparing the short-term memory binding test and RAVLT as predictors of hippocampal atrophy

BACKGROUND: The Rey Auditory Verbal Learning Test (RAVLT) assesses the long-term verbal episodic memory, while the short-term memory binding (STMB) tests assess conjunctive memory binding. In the STMB, participants should remember the integration of shapes (or objects) and colors, forming a unique representation in memory. OBJECTIVE: The objective of this study was to compare the STMB and the RAVLT as predictors of hippocampal atrophy. METHODS: All participants underwent neuropsychological assessment and MRI data were collected. Participants were 17 patients with mild cognitive impairment (MCI) and 12 patients with Alzheimer’s disease (AD). All participants performed the RAVLT test and two different paradigms of the STMB test: change detection and free recall. In the change detection task, patients need to recognize if there was a difference in shapes and colors (unbound) or shape-color integrations (bound) between two consecutive screens. In the free recall task, patients were asked to recall aloud objects and colors individually (unbound condition) or object-color integrations (bound condition) that they had just seen in a screen. The groups were compared using ANCOVA analyses, and regression analyses were used to evaluate which cognitive paradigm better predicted the hippocampal atrophy. RESULTS: 10 patients showed no hippocampal atrophy (all were MCI patients) and 19 had atrophy (7 MCI and 12 AD). The group with atrophy was older and showed worse performance in the cognitive tasks. The regression model using the atrophy (positive or negative) as the dependent variable, and the STMB tasks, RAVLT delayed score, age and education as the predictors, indicated that only the STMB change detection bound task was retained in the model (R = 0.517, R2 = 0.268, p = 0.004), explaining 26,8% of the variance. Present findings suggest that the change detection STMB task may be a better marker of neurodegeneration than the other tests