Search for pair-produced resonances decaying to quark pairs in proton-proton collisions at root s=13 TeV

A general search for the pair production of resonances, each decaying to two quarks, is reported. The search is conducted separately for heavier resonances (masses above 400 GeV), where each of the four final-state quarks generates a hadronic jet resulting in a four-jet signature, and for lighter resonances (masses between 80 and 400 GeV), where the pair of quarks from each resonance is collimated and reconstructed as a single jet resulting in a two-jet signature. In addition, a b-tagged selection is applied to target resonances with a bottom quark in the final state. The analysis uses data collected with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 35.9 fb(-1), from proton-proton collisions at a center-of-mass energy of 13 TeV. The mass spectra are analyzed for the presence of new resonances, and are found to be consistent with standard model expectations. The results are interpreted in the framework of R-parity-violating supersymmetry assuming the pair production of scalar top quarks decaying via the hadronic coupling lambda ''(312) or lambda ''(323) and upper limits on the cross section as a function of the top squark mass are set. These results probe a wider range of masses than previously explored at the LHC, and extend the top squark mass limits in the (t) over tilde -> qq' scenario.Peer reviewe

Operation and performance of the ATLAS Tile Calorimeter in Run 1

The Tile Calorimeter is the hadron calorimeter covering the central region of the ATLAS experiment at the Large Hadron Collider. Approximately 10,000 photomultipliers collect light from scintillating tiles acting as the active material sandwiched between slabs of steel absorber. This paper gives an overview of the calorimeter’s performance during the years 2008–2012 using cosmic-ray muon events and proton–proton collision data at centre-of-mass energies of 7 and 8TeV with a total integrated luminosity of nearly 30 fb−1. The signal reconstruction methods, calibration systems as well as the detector operation status are presented. The energy and time calibration methods performed excellently, resulting in good stability of the calorimeter response under varying conditions during the LHC Run 1. Finally, the Tile Calorimeter response to isolated muons and hadrons as well as to jets from proton–proton collisions is presented. The results demonstrate excellent performance in accord with specifications mentioned in the Technical Design Report

Methodology for the Absolute Configuration Determination of Epoxythymols Using the Constituents of <i>Ageratina glabrata</i>

A methodology to determine the enantiomeric excess and the absolute configuration (AC) of natural epoxythymols was developed and tested using five constituents of <i>Ageratina glabrata</i>. The methodology is based on enantiomeric purity determination employing 1,1′-bi-2-naphthol (BINOL) as a chiral solvating agent combined with vibrational circular dichroism (VCD) measurements and calculations. The conformational searching included an extensive Monte Carlo protocol that considered the rotational barriers to cover the whole conformational spaces. (+)-(8<i>S</i>)-10-Benzoyloxy-6-hydroxy-8,9-epoxythymol isobutyrate (<b>1</b>), (+)-(8<i>S</i>)-10-acetoxy-6-methoxy-8,9-epoxythymol isobutyrate (<b>4</b>), and (+)-(8<i>S</i>)-10-benzoyloxy-6-methoxy-8,9-epoxythymol isobutyrate (<b>5</b>) were isolated as enantiomerically pure constituents, while 10-isobutyryloxy-8,9-epoxythymol isobutyrate (<b>2</b>) was obtained as a 75:25 (8<i>S</i>)/(8<i>R</i>) scalemic mixture. In the case of 10-benzoyloxy-8,9-epoxythymol isobutyrate (<b>3</b>), the BINOL methodology revealed a 56:44 scalemic mixture and the VCD measurement was beyond the limit of sensitivity since the enantiomeric excess is only 12%. The racemization process of epoxythymol derivatives was studied using compound <b>1</b> and allowed the clarification of some stereochemical aspects of epoxythymol derivatives since their ACs have been scarcely analyzed and a particular behavior in their specific rotations was detected. In more than 30 oxygenated thymol derivatives, including some epoxythymols, the reported specific rotation values fluctuate from −1.6 to +1.4 passing through zero, suggesting the presence of scalemic and close to racemic mixtures, since enantiomerically pure natural constituents showed positive or negative specific rotations greater than 10 units

pH-Sensitive Fluorescence Lifetime Molecular Probes Based on Functionalized Tristyrylbenzene

The dependence of the fluorescence on pH for two 1,3,5-tristyrylbenzenes decorated with polyamine (compound <b>1</b>) and poly­(amidoamine) (compound <b>2</b>) chains at the periphery was investigated. The highest fluorescence intensities were observed under acidic conditions because electrostatic repulsions between positively charged molecules reduce the fluorescence quenching. The slopes observed in the fluorescence pH titration curves were associated with deprotonation of the different types of amine groups, which results in quenching by photoinduced electron transfer and aggregation processes. The linear dependence of fluorescence lifetime observed for different pH ranges is a valuable property for applications in the field of fluorescence lifetime sensors and imaging microscopy. The influence of the pH and the peripheral chains on the aggregation processes was also analyzed by absorption and emission spectroscopy, dynamic light scattering measurements, and transmission electron microscopy. For compound <b>1</b>, bands associated with the formation of aggregates were detected along with micrometric aggregates surrounded by fibers with lattice fringes typical of columnar mesophases. For compound <b>2</b>, which contains longer peripheral chains with a higher degree of branching, aggregates with lower internal order were observed. In this case, the peripheral chains hindered aggregation by π-stacking although the amine groups did allow hydrogen bonding

Room-Temperature Polar Order in [NH₄][Cd(HCOO)₃] - A Hybrid Inorganic–Organic Compound with a Unique Perovskite Architecture

We report on the hybrid inorganic–organic ammonium compound [NH₄]­[Cd­(HCOO)₃], which displays a most unusual framework structure: instead of the expected 4⁹·6⁶ topology, it shows an ABX₃ perovskite architecture with the peculiarity and uniqueness (among all the up-to-date reported hybrid metal formates) that the Cd ions are connected only by <i>syn</i>–<i>anti</i> formate bridges, instead of <i>anti</i>–<i>anti</i> ones. This change of the coordination mode of the formate ligand is thus another variable that can provide new possibilities for tuning the properties of these versatile functional metal–organic framework materials. The room-temperature crystal structure of [NH₄]­[Cd­(HCOO)₃] is noncentrosymmetric (S.G.: <i>Pna</i>2₁) and displays a polar axis. DFT calculations and symmetry mode analysis show that the rather large polarization arising from the off-center shift of the ammonium cations in the cavities (4.33 μC/cm²) is partially canceled by the antiparallel polarization coming from the [Cd­(HCOO)₃]⁻ framework, thus resulting in a net polarization of 1.35 μC/cm². As shown by second harmonic generation studies, this net polarization can be greatly increased by applying pressure (<i>P</i>_max = 14 GPa), an external stimulus that, in turn, induces the appearance of new structural phases, as confirmed by Raman spectroscopy

info:eu-repo/semantics/acceptedVersion

Highly substituted benzene derivatives have been easily prepared in a regioselective way from readily available 1,3-hexadien-5-ynes through a gold(I)-catalyzed tandem reaction. The process involves an initial cyclization followed by a selective Wagner-Meerwein shift in which the migration preference seems to be determined by the ability to stabilize a positive chargeMinisterio de Ciencia e Innovacion (MICINN) and FEDER (CTQ2010-15358 and CTQ2009-09949/BQU) and Junta de Castilla y Leon (BU021A09 and GR-172) for financial suport. A.M. S. thanks Junta de Castilla y Leon for a predoctoral fellowship. P.G.-G. and M.A.F.-R. thank MICINN for "Juan de la Cierva" and "Ramon y Cajal" contractsMinisterio de Ciencia e Innovacion (MICINN) and FEDER (CTQ2010-15358 and CTQ2009-09949/BQU) and Junta de Castilla y Leon (BU021A09 and GR-172) for financial suport. A.M. S. thanks Junta de Castilla y Leon for a predoctoral fellowship. P.G.-G. and M.A.F.-R. thank MICINN for "Juan de la Cierva" and "Ramon y Cajal" contractsThis document is the Accepted Manuscript version of a Published Work that appeared in final form in Organic letters, copyright © American Chemical Society after peer review and technical editing by the publisher