Faculty Publications: July, 2015

Query Results from the Smithsonian/NASA Astrophysics Data System (ADS)

The following are Harvard Physics faculty members' publications, added to the ADS database last month. Please note that some publications which appeared in print last month may not be included in the database (and therefore may not appear on this list) until the following month.

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Title:
Origin of the visible emission of black silicon microstructures
Authors:
Fabbri, Filippo; Lin, Yu-Ting; Bertoni, Giovanni; Rossi, Francesca; Smith, Matthew J.; Gradečak, Silvija; Mazur, Eric; Salviati, Giancarlo
Publication:
Applied Physics Letters, Volume 107, Issue 2, id.021907 (ApPhL Homepage)
Publication Date:
07/2015
Origin:
AIP
Abstract Copyright:
2015: AIP Publishing LLC
DOI:
10.1063/1.4926912
Bibliographic Code:
2015ApPhL.107b1907F

Abstract

Silicon, the mainstay semiconductor in microelectronics, is considered unsuitable for optoelectronic applications due to its indirect electronic band gap that limits its efficiency as light emitter. Here, we univocally determine at the nanoscale the origin of visible emission in microstructured black silicon by cathodoluminescence spectroscopy and imaging. We demonstrate the formation of amorphous silicon oxide microstructures with a white emission. The white emission is composed by four features peaking at 1.98 eV, 2.24 eV, 2.77 eV, and 3.05 eV. The origin of such emissions is related to SiOx intrinsic point defects and to the sulfur doping due to the laser processing. Similar results go in the direction of developing optoelectronic devices suitable for silicon-based circuitry.

Title:
A Three-Dimensional Map of Milky-Way Dust
Authors:
Green, Gregory M.; Schlafly, Edward F.; Finkbeiner, Douglas P.; Rix, Hans-Walter; Martin, Nicolas; Burgett, William; Draper, Peter W.; Flewelling, Heather; Hodapp, Klaus; Kaiser, Nicholas; Kudritzki, Rolf Peter; Magnier, Eugene; Metcalfe, Nigel; Price, Paul; Tonry, John; Wainscoat, Richard
Publication:
eprint arXiv:1507.01005
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
Astrophysics - Astrophysics of Galaxies
Comment:
Accepted for publication in ApJ
Bibliographic Code:
2015arXiv150701005G

Abstract

We present a three-dimensional map of interstellar dust reddening, covering three-quarters of the sky out to a distance of several kiloparsecs, based on Pan-STARRS 1 and 2MASS photometry. The map reveals a wealth of detailed structure, from filaments to large cloud complexes. The map has a hybrid angular resolution, with most of the map at an angular resolution of 3.4' to 13.7', and a maximum distance resolution of ~25%. The three-dimensional distribution of dust is determined in a fully probabilistic framework, yielding the uncertainty in the reddening distribution along each line of sight, as well as stellar distances, reddenings and classifications for 800 million stars detected by Pan-STARRS 1. We demonstrate the consistency of our reddening estimates with those of two-dimensional emission-based maps of dust reddening. In particular, we find agreement with the Planck 353 GHz optical depth-based reddening map to within 0.05 mag in E(B-V) to a depth of 0.5 mag, and explore systematics at reddenings less than E(B-V) ~ 0.08 mag. We validate our per-star reddening estimates by comparison with reddening estimates for stars with both SDSS photometry and SEGUE spectral classifications, finding per-star agreement to within 0.1 mag out to a stellar E(B-V) of 1 mag. We compare our map to two existing three-dimensional dust maps, by Marshall et al. (2006) and Lallement et al. (2013), demonstrating our finer angular resolution, and better distance resolution compared to the former within ~3 kpc. The map can be queried or downloaded at http://argonaut.skymaps.info. We expect the three-dimensional reddening map presented here to find a wide range of uses, among them correcting for reddening and extinction for objects embedded in the plane of the Galaxy, studies of Galactic structure, calibration of future emission-based dust maps and determining distances to objects of known reddening.

Title:
Theory of Graphene Raman Spectroscopy
Authors:
Heller, Eric J.; Yang, Yuan; Kocia, Lucas; Chen, Wei; Fang, Shiang; Borunda, Mario; Kaxiras, Efthimios
Publication:
eprint arXiv:1507.01647
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
Condensed Matter - Materials Science
Bibliographic Code:
2015arXiv150701647H

Abstract

Raman spectroscopy plays a key role in studies of graphene and related carbon systems. Graphene is perhaps the most promising material of recent times for many novel applications, including electronics. In this paper, the traditional and well established Kramers-Heisenberg-Dirac (KHD) Raman scattering theory (1925-1927) is extended to crystalline graphene for the first time. It demands different phonon production mechanisms and phonon energies than does the popular "double resonance" Raman scattering model. The latter has never been compared to KHD. Within KHD, phonons are produced instantly along with electrons and holes, in what we term an electron-hole-phonon triplet, which does not suffer Pauli blocking. A new mechanism for double phonon production we name "transition sliding" explains the brightness of the 2D mode and other overtones, as a result of linear (Dirac cone) electron dispersion. Direct evidence for sliding resides in hole doping experiments performed in 2011 \cite{chenCrommie}. Whole ranges of electronic transitions are permitted and may even constructively interfere for the same laser energy and phonon q, explaining the dispersion, bandwidth, and strength of many two phonon Raman bands. Graphene's entire Raman spectrum, including dispersive and fixed bands, missing bands not forbidden by symmetries, weak bands, overtone bands, Stokes anti-Stokes anomalies, individual bandwidths, trends with doping, and D-2D band spacing anomalies emerge naturally and directly in KHD theory.

Title:
Prethermal Floquet steady-states and instabilities in the periodically-driven, weakly-interacting Bose-Hubbard model
Authors:
Bukov, M.; Gopalakrishnan, S.; Knap, M.; Demler, E.
Publication:
eprint arXiv:1507.01946
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
Condensed Matter - Quantum Gases, Condensed Matter - Other Condensed Matter
Comment:
Three (3) numerical simulations in mp4 format available in the source code files. A legend for them is available in appendix F
Bibliographic Code:
2015arXiv150701946B

Abstract

We explore the prethermal Floquet steady-states and instabilities of the weakly interacting two-dimensional Bose Hubbard model subject to periodic driving. We develop a description of the nonequilibrium dynamics using a weak-coupling conserving approximation. This approach allows us to explore dynamics at arbitrary drive strength and frequency. We establish the regimes in which conventional (zero-momentum) and unconventional ($(\pi,\pi)$-momentum) condensates are stable on intermediate time scales. We find that the condensate stability is \emph{enhanced} by increasing the drive strength, because this decreases the bandwidth of quasiparticle excitations and thus impedes resonant absorption and heating. Our results are directly relevant to a number of current experiments with ultracold lattice bosons.

Title:
High-Temperature Quantum Anomalous Hall Effect in n-p Codoped Topological Insulators
Authors:
Qi, Shifei; Qiao, Zhenhua; Deng, Xinzhou; Cubuk, Ekin D.; Chen, Hua; Zhu, Wenguang; Kaxiras, Efthimios; Zhang, S. B.; Xu, Xiaohong; Zhang, Zhenyu
Publication:
eprint arXiv:1507.03218
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
Condensed Matter - Materials Science
Comment:
5 pages, 3 figures
Bibliographic Code:
2015arXiv150703218Q

Abstract

The quantum anomalous Hall effect (QAHE) is a fundamental quantum transport phenomenon that manifests as a quantized transverse conductance in response to a longitudinally applied electric field in the absence of an external magnetic field, and promises to have immense application potentials in future dissipation-less quantum electronics. Here we present a novel kinetic pathway to realize the QAHE at high temperatures by $n$-$p$ codoping of three-dimensional topological insulators. We provide proof-of-principle numerical demonstration of this approach using vanadium-iodine (V-I) codoped Sb$_2$Te$_3$ and demonstrate that, strikingly, even at low concentrations of $\sim$2\% V and $\sim$1\% I, the system exhibits a quantized Hall conductance, the tell-tale hallmark of QAHE, at temperatures of at least $\sim$ 50 Kelvin, which is three orders of magnitude higher than the typical temperatures at which it has been realized so far. The proposed approach is conceptually general and may shed new light in experimental realization of high-temperature QAHE.

Title:
Similarity and singularity in adhesive elastohydrodynamic touchdown
Authors:
Carlson, Andreas; Mahadevan, L.
Publication:
eprint arXiv:1507.03912
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
Physics - Fluid Dynamics
Bibliographic Code:
2015arXiv150703912C

Abstract

We consider the touchdown of an elastic sheet as it adheres to a wall, which has a dynamics that is limited by the viscous resistance provided by the squeeze flow of the intervening liquid trapped between the two solid surfaces. The dynamics of the sheet is described mathematically by elastohydrodynamic lubrication theory, coupling the elastic deformation of the sheet, the microscopic van der Waals adhesion and the viscous thin film flow. We use a combination of numerical simulations of the governing partial differential equation and a scaling analysis to describe the self-similar solution of the touchdown of the sheet as it approaches the wall. An analysis of the equation satisfied by the similarity variables in the vicinity of the touchdown event shows that an entire sequence of solutions are allowed. However, a comparison of these shows that only the fundamental similarity solution is observed in the time-dependent numerical simulations, consistent with the fact that it alone is stable. Our analysis generalizes similar approaches for rupture in capillary thin film hydrodynamics and suggests experimentally verifiable predictions for a new class of singular flows linking elasticity, hydrodynamics and adhesion.

Title:
Testing the Foundations of Classical Entropy: Colloid Experiments
Authors:
Cates, Michael E.; Manoharan, Vinothan N.
Publication:
eprint arXiv:1507.04030
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
Condensed Matter - Soft Condensed Matter, Condensed Matter - Statistical Mechanics
Comment:
doi:10.1039/C5SM01014D
Bibliographic Code:
2015arXiv150704030C

Abstract

Defining the entropy of classical particles raises a number of paradoxes and ambiguities, some of which have been known for over a century. Several, such as Gibbs' paradox, involve the fact that classical particles are distinguishable, and in textbooks these are often `resolved' by appeal to the quantum-mechanical indistinguishability of atoms or molecules of the same type. However, questions then remain of how to correctly define the entropy of large poly-atomic particles such as colloids in suspension, of which no two are exactly alike. By performing experiments on such colloids, one can establish that certain definitions of the classical entropy fit the data, while others in the literature do not. Specifically, the experimental facts point firmly to an `informatic' interpretation that dates back to Gibbs: entropy is determined by the number of microstates that we as observers choose to treat as equivalent when we identify a macrostate. This approach, unlike some others, can account for the existence of colloidal crystals, and for the observed abundances of colloidal clusters of different shapes. We also address some lesser-known paradoxes whereby the physics of colloidal assemblies, which ought to be purely classical, seems to involve quantum mechanics directly. The experimental symptoms of such involvement are predicted to be `isotope effects' in which colloids with different inertial masses, but otherwise identical sizes and properties, show different aggregation statistics. These paradoxes are caused by focussing one's attention on some classical degrees while neglecting others; when all are treated equally, all isotope effects are found to vanish.

Title:
Precision measurement of the speed of propagation of neutrinos using the MINOS detectors
Authors:
Adamson, P.; Anghel, I.; Ashby, N.; Aurisano, A.;... Feldman, G. J.;... and 118 coauthors
Publication:
eprint arXiv:1507.04328
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
High Energy Physics - Experiment, Physics - Instrumentation and Detectors
Comment:
10 pages, six figures, submitted to PRD
Bibliographic Code:
2015arXiv150704328A

Abstract

We report a two-detector measurement of the propagation speed of neutrinos over a baseline of 734 km. The measurement was made with the NuMI beam at Fermilab between the near and far MINOS detectors. The fractional difference between the neutrino speed and the speed of light is determined to be $(v/c-1) = (1.0 \pm 1.1) \times 10^{-6}$, consistent with relativistic neutrinos.

Title:
Friedel Oscillations as a Probe of Fermionic Quasiparticles
Authors:
Dalla Torre, Emanuele G.; Benjamin, David; He, Yang; Dentelski, David; Demler, Eugene
Publication:
eprint arXiv:1507.04345
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity
Bibliographic Code:
2015arXiv150704345D

Abstract

When immersed in a see of cold electrons, local impurities give rise to density modulations known as Friedel oscillations. In spite of the generality of this phenomenon, the exact shape of these modulations is usually computed only for non-interacting electrons with a quadratic dispersion relation. In actual materials, one needs to take into account several additional factors, such as (i) the details of the band structure, (ii) the lifetime of quasiparticles, (iii) in superconductors, the presence of a pairing gap. Studying how these effects influence Friedel oscillations is a viable way to access the properties of fermionic excitations in strongly-correlated materials. In this work we analyze the signatures of Friedel oscillations in STM and X-ray scattering experiments, focusing on the concrete example of cuprates superconductors. A detailed comparison with recent experiments reveals a rich interplay between local modulation of the chemical potential and of the pairing gap.

Title:
Generalized Erdos Numbers for network analysis
Authors:
Morrison, Greg; Dudte, Levi; Mahadevan, L.
Publication:
eprint arXiv:1507.04400
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
Physics - Physics and Society, Computer Science - Social and Information Networks
Bibliographic Code:
2015arXiv150704400M

Abstract

In this paper we consider the concept of `closeness' between nodes in a weighted network that can be defined topologically even in the absence of a metric. The Generalized Erd\H{o}s Numbers (GENs) satisfy a number of desirable properties as a measure of topological closeness when nodes share a finite resource between nodes as they are real-valued and non-local, and can be used to create an asymmetric matrix of connectivities. We show that they can be used to define a personalized measure of the importance of nodes in a network with a natural interpretation that leads to a new global measure of centrality and is highly correlated with Page Rank. The relative asymmetry of the GENs (due to their non-metric definition) is linked also to the asymmetry in the mean first passage time between nodes in a random walk, and we use a linearized form of the GENs to develop a continuum model for `closeness' in spatial networks. As an example of their practicality, we deploy them to characterize the structure of static networks and show how it relates to dynamics on networks in such situations as the spread of an epidemic.

Title:
Hyperscaling at the spin density wave quantum critical point in two dimensional metals
Authors:
Patel, Aavishkar A.; Strack, Philipp; Sachdev, Subir
Publication:
eprint arXiv:1507.05962
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Quantum Gases, High Energy Physics - Theory
Comment:
46 pages, 5 figures
Bibliographic Code:
2015arXiv150705962P

Abstract

The hyperscaling property implies that spatially isotropic critical quantum states in $d$ spatial dimensions have a specific heat which scales with temperature as $T^{d/z}$, and an optical conductivity which scales with frequency as $\omega^{(d-2)/z}$ for $\omega \gg T$, where $z$ is the dynamic critical exponent. We examine the spin-density-wave critical fixed point of metals in $d=2$ found by Sur and Lee (Phys. Rev. B 91, 125136 (2015)) in an expansion in $\epsilon = 3-d$. We find that the contributions of the "hot spots" on the Fermi surface to the optical conductivity and specific heat obey hyperscaling (up to logarithms), and agree with the results of the large $N$ analysis of the optical conductivity by Hartnoll et al. (Phys. Rev. B 84, 125115 (2011)). With a small bare velocity of the boson associated with the spin density wave order, there is an intermediate energy regime where hyperscaling is violated with $d \rightarrow d_t$, where $d_t = 1$ is the number of dimensions transverse to the Fermi surface. We also present a Boltzmann equation analysis which indicates that the hot spot contribution to the DC conductivity has the same scaling as the optical conductivity, with $T$ replacing $\omega$.

Title:
Streamlining resummed QCD calculations using Monte Carlo integration
Authors:
Farhi, David; Feige, Ilya; Freytsis, Marat; Schwartz, Matthew D.
Publication:
eprint arXiv:1507.06315
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
High Energy Physics - Phenomenology
Comment:
30 pages, 10 figures, code included with submission
Bibliographic Code:
2015arXiv150706315F

Abstract

Some of the most arduous and error-prone aspects of precision resummed calculations are related to the partonic hard process, having nothing to do with the resummation. In particular, interfacing to parton-distribution functions, combining various channels, and performing the phase space integration can be limiting factors in completing calculations. Conveniently, however, most of these tasks are already automated in many Monte Carlo programs, such as MadGraph, Alpgen or Sherpa. In this paper, we show how such programs can be used to produce distributions of partonic kinematics with associated color structures representing the hard factor in a resummed distribution. These distributions can then be used to weight convolutions of jet, soft and beam functions producing a complete resummed calculation. In fact, only around 1000 unweighted events are necessary to produce precise distributions. A number of examples and checks are provided, including $e^+e^-$ two- and four-jet event shapes, $n$-jettiness and jet-mass related observables at hadron colliders. Attached code can be used to modify MadGraph to export the relevant leading-order hard functions and color structures for arbitrary processes.

Title:
The NuMI Neutrino Beam
Authors:
Adamson, P.; Anderson, K.; Andrews, M.; Andrews, R.;... Feldman, G. J.;... and 185 coauthors
Publication:
eprint arXiv:1507.06690
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
Physics - Accelerator Physics, High Energy Physics - Experiment
Bibliographic Code:
2015arXiv150706690A

Abstract

This paper describes the hardware and operations of the Neutrinos at the Main Injector (NuMI) beam at Fermilab. It elaborates on the design considerations for the beam as a whole and for individual elements. The most important design details of individual components are described. Beam monitoring systems and procedures, including the tuning and alignment of the beam and NuMI long-term performance, are also discussed.

Title:
Atomic-scale Electronic Structure of the Cuprate d-Symmetry Form Factor Density Wave State
Authors:
Hamidian, M. H.; Edkins, S. D.; Kim, Chung Koo; Séamus Davis, J. C.; Mackenzie, A. P.; Eisaki, H.; Uchida, S.; Lawler, M. J.; Kim, E.-A.; Sachdev, Subir; Fujita, K.
Publication:
eprint arXiv:1507.07865
Publication Date:
07/2015
Origin:
ARXIV
Keywords:
Condensed Matter - Superconductivity
Bibliographic Code:
2015arXiv150707865H

Abstract

Extensive research into high temperature superconducting cuprates is now focused upon identifying the relationship between the classic 'pseudogap' phenomenon$^{1,2}$ and the more recently investigated density wave state$^{3-13}$. This state always exhibits wave vector $Q$ parallel to the planar Cu-O-Cu bonds$^{4-13}$ along with a predominantly $d$-symmetry form factor$^{14-17}$ (dFF-DW). Finding its microscopic mechanism has now become a key objective$^{18-30}$ of this field. To accomplish this, one must identify the momentum-space ($k$-space) states contributing to the dFF-DW spectral weight, determine their particle-hole phase relationship about the Fermi energy, establish whether they exhibit a characteristic energy gap, and understand the evolution of all these phenomena throughout the phase diagram. Here we use energy-resolved sublattice visualization$^{14}$ of electronic structure and show that the characteristic energy of the dFF-DW modulations is actually the 'pseudogap' energy $\Delta_{1}$. Moreover, we demonstrate that the dFF-DW modulations at $E=-\Delta_{1}$ (filled states) occur with relative phase $\pi$ compared to those at $E=\Delta_{1}$ (empty states). Finally, we show that the dFF-DW $Q$ corresponds directly to scattering between the 'hot frontier' regions of $k$-space beyond which Bogoliubov quasiparticles cease to exist$^{31,32,33}$. These data demonstrate that the dFF-DW state is consistent with particle-hole interactions focused at the pseudogap energy scale and between the four pairs of 'hot frontier' regions in $k$-space where the pseudogap opens.

Title:
Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at TeV with the ATLAS detector
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Barreiro Guimarães da Costa, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2822 coauthors
Publication:
The European Physical Journal C, Volume 75, article id. #299, 43 pp. (EPJC Homepage)
Publication Date:
07/2015
Origin:
SPRINGER
Abstract Copyright:
(c) 2015: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-015-3517-3
Bibliographic Code:
2015EPJC...75..299A

Abstract

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 of TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between GeV and 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 presented.

Title:
Identification and energy calibration of hadronically decaying tau leptons with the ATLAS experiment in pp collisions at
Authors:
Aad, G.; Abbott, B.; Abdallah, J.Barreiro Guimarães da Costa, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2881 coauthors
Publication:
The European Physical Journal C, Volume 75, article id. #303, 33 pp. (EPJC Homepage)
Publication Date:
07/2015
Origin:
SPRINGER
Abstract Copyright:
(c) 2015: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-015-3500-z
Bibliographic Code:
2015EPJC...75..303A

Abstract

This paper describes the trigger and offline reconstruction, identification and energy calibration algorithms for hadronic decays of tau leptons employed for the data collected from pp collisions in 2012 with the ATLAS detector at the LHC center-of-mass energy . The performance of these algorithms is measured in most cases with decays to tau leptons using the full 2012 dataset, corresponding to an integrated luminosity of 20.3 fb. An uncertainty on the offline reconstructed tau energy scale of 2-4 %, depending on transverse energy and pseudorapidity, is achieved using two independent methods. The offline tau identification efficiency is measured with a precision of 2.5 % for hadronically decaying tau leptons with one associated track, and of 4 % for the case of three associated tracks, inclusive in pseudorapidity and for a visible transverse energy greater than 20 . For hadronic tau lepton decays selected by offline algorithms, the tau trigger identification efficiency is measured with a precision of 2-8 %, depending on the transverse energy. The performance of the tau algorithms, both offline and at the trigger level, is found to be stable with respect to the number of concurrent proton-proton interactions and has supported a variety of physics results using hadronically decaying tau leptons at ATLAS.

Title:
Search for supersymmetry in events containing a same-flavour opposite-sign dilepton pair, jets, and large missing transverse momentum in TeV pp collisions with the ATLAS detector
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Barreiro Guimarães da Costa, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2815 coauthors
Publication:
The European Physical Journal C, Volume 75, article id. #318, 40 pp. (EPJC Homepage)
Publication Date:
07/2015
Origin:
SPRINGER
Abstract Copyright:
(c) 2015: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-015-3518-2
Bibliographic Code:
2015EPJC...75..318A

Abstract

Two searches for supersymmetric particles in final states containing a same-flavour opposite-sign lepton pair, jets and large missing transverse momentum are presented. The proton-proton collision data used in these searches were collected at a centre-of-mass energy TeV by the ATLAS detector at the Large Hadron Collider and corresponds to an integrated luminosity of 20.3 fb. Two leptonic production mechanisms are considered: decays of squarks and gluinos with Z bosons in the final state, resulting in a peak in the dilepton invariant mass distribution around the Z-boson mass; and decays of neutralinos (e.g. ), resulting in a kinematic endpoint in the dilepton invariant mass distribution. For the former, an excess of events above the expected Standard Model background is observed, with a significance of three standard deviations. In the latter case, the data are well-described by the expected Standard Model background. The results from each channel are interpreted in the context of several supersymmetric models involving the production of squarks and gluinos.

Title:
Measurement of the top quark mass in the tt → lepton+jets and  tt → dilepton and channels using √s= 7 TeV ATLAS data
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Barreiro Guimarães da Costa, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2819 coauthors
Publication:
The European Physical Journal C, Volume 75, article id. #330, 36 pp. (EPJC Homepage)
Publication Date:
07/2015
Origin:
SPRINGER
Abstract Copyright:
(c) 2015: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-015-3544-0
Bibliographic Code:
2015EPJC...75..330A

Abstract

The top quark mass was measured in the channels $t\bar{t} \to \mathrm{lepton+jets}$ and $t\bar{t} \to \mathrm{dilepton}$ (lepton=$e, \mu$) based on ATLAS data recorded in 2011. The data were taken at the LHC with a proton--proton centre-of-mass energy of $\sqrt{s}=7$ TeV and correspond to an integrated luminosity of 4.6fb$^{-1}$. The $t\bar{t} \to \mathrm{lepton+jets}$ analysis uses a three-dimensional template technique which determines the top quark mass together with a global jet energy scale factor (JSF), and a relative $b$-to-light-jet energy scale factor (bJSF), where the terms $b$-jets and light-jets refer to jets originating from $b$-quarks and $u, d, c, s$-quarks or gluons, respectively. The analysis of the $t\bar{t} \to \mathrm{dilepton}$ channel exploits a one-dimensional template method using the $m_{\ell b}$ observable, defined as the average invariant mass of the two lepton+$b$-jet pairs in each event. The top quark mass is measured to be $172.33\pm 0.75(\rm {stat}) \pm 1.02(\rm {syst})$ GeV, and $173.79 \pm 0.54({\rm stat}) \pm 1.30({\rm syst})$ GeV in the $t\bar{t} \to lepton+jets$ and $t\bar{t} \to dilepton$ channels, respectively. The combination of the two results yields $m_{\mathrm top} = 172.99 \pm 0.48({\rm stat}) \pm 0.78({\rm syst})$ GeV, with a total uncertainty of $0.91$ GeV.

Title:
Constraints on the off-shell Higgs boson signal strength in the high-mass ZZ and WW final states with the ATLAS detector
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Barreiro Guimarães da Costa, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2815 coauthors
Publication:
The European Physical Journal C, Volume 75, article id. #330, 36 pp. (EPJC Homepage)
Publication Date:
07/2015
Origin:
SPRINGER
Abstract Copyright:
(c) 2015: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-015-3544-0
Bibliographic Code:
2015EPJC...75..330A

Abstract

The top quark mass was measured in the channels $t\bar{t} \to \mathrm{lepton+jets}$ and $t\bar{t} \to \mathrm{dilepton}$ (lepton=$e, \mu$) based on ATLAS data recorded in 2011. The data were taken at the LHC with a proton--proton centre-of-mass energy of $\sqrt{s}=7$ TeV and correspond to an integrated luminosity of 4.6fb$^{-1}$. The $t\bar{t} \to \mathrm{lepton+jets}$ analysis uses a three-dimensional template technique which determines the top quark mass together with a global jet energy scale factor (JSF), and a relative $b$-to-light-jet energy scale factor (bJSF), where the terms $b$-jets and light-jets refer to jets originating from $b$-quarks and $u, d, c, s$-quarks or gluons, respectively. The analysis of the $t\bar{t} \to \mathrm{dilepton}$ channel exploits a one-dimensional template method using the $m_{\ell b}$ observable, defined as the average invariant mass of the two lepton+$b$-jet pairs in each event. The top quark mass is measured to be $172.33\pm 0.75(\rm {stat}) \pm 1.02(\rm {syst})$ GeV, and $173.79 \pm 0.54({\rm stat}) \pm 1.30({\rm syst})$ GeV in the $t\bar{t} \to lepton+jets$ and $t\bar{t} \to dilepton$ channels, respectively. The combination of the two results yields $m_{\mathrm top} = 172.99 \pm 0.48({\rm stat}) \pm 0.78({\rm syst})$ GeV, with a total uncertainty of $0.91$ GeV.

Title:
Search for invisible decays of the Higgs boson produced in association with a hadronically decaying vector boson in pp collisions at TeV with the ATLAS detector
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Barreiro Guimarães da Costa, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2820 coauthors
Publication:
The European Physical Journal C, Volume 75, article id. #337, 24 pp. (EPJC Homepage)
Publication Date:
07/2015
Origin:
SPRINGER
Abstract Copyright:
(c) 2015: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-015-3551-1
Bibliographic Code:
2015EPJC...75..337A

Abstract

A search for Higgs boson decays to invisible particles is performed using 20.3 of pp collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the Large Hadron Collider. The process considered is Higgs boson production in association with a vector boson ( or Z) that decays hadronically, resulting in events with two or more jets and large missing transverse momentum. No excess of candidates is observed in the data over the background expectation. The results are used to constrain VH production followed by H decaying to invisible particles for the Higgs boson mass range GeV. The 95 % confidence-level observed upper limit on varies from 1.6 pb at 115 GeV to 0.13 pb at 300 GeV. Assuming Standard Model production and including the contribution as signal, the results also lead to an observed upper limit of 78 % at 95 % confidence level on the branching ratio of Higgs bosons decays to invisible particles at a mass of 125 GeV.

Title:
Search for the Standard Model Higgs boson produced in association with top quarks and decaying into in collisions at with the ATLAS detector
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Barreiro Guimarães da Costa, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2817 coauthors
Publication:
The European Physical Journal C, Volume 75, article id. #349, 50 pp. (EPJC Homepage)
Publication Date:
07/2015
Origin:
SPRINGER
Abstract Copyright:
(c) 2015: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-015-3543-1
Bibliographic Code:
2015EPJC...75..349A

Abstract

A search for the Standard Model Higgs boson produced in association with a top-quark pair, , is presented. The analysis uses 20.3 fb-1 of pp collision data at , collected with the ATLAS detector at the Large Hadron Collider during 2012. The search is designed for the decay mode and uses events containing one or two electrons or muons. In order to improve the sensitivity of the search, events are categorised according to their jet and b-tagged jet multiplicities. A neural network is used to discriminate between signal and background events, the latter being dominated by +jets production. In the single-lepton channel, variables calculated using a matrix element method are included as inputs to the neural network to improve discrimination of the irreducible background. No significant excess of events above the background expectation is found and an observed (expected) limit of 3.4 (2.2) times the Standard Model cross section is obtained at 95 % confidence level. The ratio of the measured signal cross section to the Standard Model expectation is found to be assuming a Higgs boson mass of 125.
Title:
Search for low-scale gravity signatures in multi-jet final states with the ATLAS detector at TeV
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Barreiro Guimarães da Costa, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2818 coauthors
Publication:
Journal of High Energy Physics, Volume 2015, article id. #32, 38 pp.
Publication Date:
07/2015
Origin:
SPRINGER
Keywords:
Exotics, Hadron-Hadron Scattering
Abstract Copyright:
(c) 2015: The Author(s)
DOI:
10.1007/JHEP07(2015)032
Bibliographic Code:
2015JHEP...07..032A

Abstract

A search for evidence of physics beyond the Standard Model in final states with multiple high-transverse-momentum jets is performed using 20.3 fb-1 of proton-proton collision data at TeV recorded by the ATLAS detector at the LHC. No significant excess of events beyond Standard Model expectations is observed, and upper limits on the visible cross sections for non-Standard Model production of multi-jet final states are set. A wide variety of models for black hole and string ball production and decay are considered, and the upper limit on the cross section times acceptance is as low as 0.16 fb at the 95% confidence level. For these models, excluded regions are also given as function of the main model parameters. [Figure not available: see fulltext.]

Title:
Fast plunges into Kerr black holes
Authors:
Hadar, Shahar; Porfyriadis, Achilleas P.; Strominger, Andrew
Publication:
Journal of High Energy Physics, Volume 2015, article id. #78, 15 pp.
Publication Date:
07/2015
Origin:
SPRINGER
Keywords:
AdS-CFT Correspondence, Black Holes, Space-Time Symmetries
Abstract Copyright:
(c) 2015: The Author(s)
DOI:
10.1007/JHEP07(2015)078
Bibliographic Code:
2015JHEP...07..078H

Abstract

Most extreme-mass-ratio-inspirals of small compact objects into supermassive black holes end with a fast plunge from an eccentric last stable orbit. For rapidly rotating black holes such fast plunges may be studied in the context of the Kerr/CFT correspondence because they occur in the near-horizon region where dynamics are governed by the infinite dimensional conformal symmetry. In this paper we use conformal transformations to analytically solve for the radiation emitted from fast plunges into near-extreme Kerr black holes. We find perfect agreement between the gravity and CFT computations.

Title:
Plasmonic Tipless Pyramid Arrays for Cell Poration
Authors:
Courvoisier, Sébastien; Saklayen, Nabiha; Huber, Marinus; Chen, Jun; Diebold, Eric D.; Bonacina, Luigi; Wolf, Jean-Pierre; Mazur, Eric
Publication:
Nano Letters, vol. 15, issue 7, pp. 4461-4466
Publication Date:
07/2015
Origin:
CROSSREF
DOI:
10.1021/acs.nanolett.5b01697
Bibliographic Code:
2015NanoL..15.4461C

Abstract

Not Available

Title:
Direct Observation of Wet Biological Samples by Graphene Liquid Cell Transmission Electron Microscopy
Authors:
Park, Jungwon; Park, Hyesung; Ercius, Peter; Pegoraro, Adrian F.; Xu, Chen; Kim, Jin Woong; Han, Sang Hoon; Weitz, David A.
Publication:
Nano Letters, vol. 15, issue 7, pp. 4737-4744
Publication Date:
07/2015
Origin:
CROSSREF
DOI:
10.1021/acs.nanolett.5b01636
Bibliographic Code:
2015NanoL..15.4737P

Abstract

Not Available


Title:
Quenching of dynamic nuclear polarization by spin-orbit coupling in GaAs quantum dots
Authors:
Nichol, John M.; Harvey, Shannon P.; Shulman, Michael D.; Pal, Arijeet; Umansky, Vladimir; Rashba, Emmanuel I.; Halperin, Bertrand I.; Yacoby, Amir
Publication:
Nature Communications, Volume 6, id. 7682 (2015).
Publication Date:
07/2015
Origin:
NATURE
Abstract Copyright:
(c) 2015: Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.
DOI:
10.1038/ncomms8682
Bibliographic Code:
2015NatCo...6E7682N

Abstract

The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood. Here we show that spin-orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron-nuclear system, despite weak spin-orbit coupling in GaAs. Using Landau-Zener sweeps to measure static and dynamic properties of the electron spin-flip probability, we observe that the size of the spin-orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin-orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin-orbit coupling in central-spin systems.

Title:
Renormalization group approach to the Fröhlich polaron model: application to impurity-BEC problem
Authors:
Grusdt, F.; Shchadilova, Y. E.; Rubtsov, A. N.; Demler, E.
Publication:
Nature Scientific Reports, Volume 5, id. 12124 (2015).
Publication Date:
07/2015
Origin:
NATURE
Abstract Copyright:
(c) 2015: Macmillan Publishers Limited
DOI:
10.1038/srep12124
Bibliographic Code:
2015NatSR...5E2124G

Abstract

When a mobile impurity interacts with a many-body system, such as a phonon bath, a polaron is formed. Despite the importance of the polaron problem for a wide range of physical systems, a unified theoretical description valid for arbitrary coupling strengths is still lacking. Here we develop a renormalization group approach for analyzing a paradigmatic model of polarons, the so-called Fröhlich model, and apply it to a problem of impurity atoms immersed in a Bose-Einstein condensate of ultra cold atoms. Polaron energies obtained by our method are in excellent agreement with recent diagrammatic Monte Carlo calculations for a wide range of interaction strengths. They are found to be logarithmically divergent with the ultra-violet cut-off, but physically meaningful regularized polaron energies are also presented. Moreover, we calculate the effective mass of polarons and find a smooth crossover from weak to strong coupling regimes. Possible experimental tests of our results in current experiments with ultra cold atoms are discussed.

Title:
Long-distance entanglement distribution using individual atoms in optical cavities
Authors:
Borregaard, J.; Kómár, P.; Kessler, E. M.; Lukin, M. D.; Sørensen, A. S.
Publication:
Physical Review A, Volume 92, Issue 1, id.012307 (PhRvA Homepage)
Publication Date:
07/2015
Origin:
APS
PACS Keywords:
Quantum communication, Entanglement production and manipulation, Entanglement and quantum nonlocality, Coherent control of atomic interactions with photons
Abstract Copyright:
2015: American Physical Society
DOI:
10.1103/PhysRevA.92.012307
Bibliographic Code:
2015PhRvA..92a2307B

Abstract

Individual atoms in optical cavities can provide an efficient interface between stationary qubits and flying qubits (photons), which is an essential building block for quantum communication. Furthermore, cavity-assisted controlled-not (cnot) gates can be used for swapping entanglement to long distances in a quantum repeater setup. Nonetheless, dissipation introduced by the cavity during the cnot may increase the experimental difficulty in obtaining long-distance entanglement distribution using these systems. We analyze and compare a number of cavity-based repeater schemes combining various entanglement generation schemes and cavity-assisted cnot gates. We find that a scheme, where high-fidelity entanglement is first generated in a two-photon detection scheme and then swapped to long distances using a recently proposed heralded controlled-Z (cz) gate, exhibits superior performance compared to the other schemes. The heralded gate moves the effect of dissipation from the fidelity to the success probability of the gate thereby enabling high-fidelity entanglement swapping. As a result, high-rate entanglement distribution can be achieved over long distances even for low cooperativities of the atom-cavity systems. This high-fidelity repeater is shown to outperform the other cavity-based schemes by up to two orders of magnitude in the rate for realistic parameters and large distances (1000 km).

Title:
Dynamical instabilities and transient short-range order in the fermionic Hubbard model
Authors:
Bauer, Johannes; Babadi, Mehrtash; Demler, Eugene
Publication:
Physical Review B, Volume 92, Issue 2, id.024305 (PhRvB Homepage)
Publication Date:
07/2015
Origin:
APS
PACS Keywords:
Metal-insulator transitions and other electronic transitions, Strongly correlated electron systems, heavy fermions, Lattice fermion models, Non-Fermi-liquid ground states electron phase diagrams and phase transitions in model systems
Abstract Copyright:
2015: American Physical Society
DOI:
10.1103/PhysRevB.92.024305
Bibliographic Code:
2015PhRvB..92b4305B

Abstract

We study the dynamics of magnetic correlations in the half-filled fermionic Hubbard model following a fast ramp of the repulsive interaction. We use Schwinger-Keldysh self-consistent second-order perturbation theory to investigate the evolution of single-particle Green's functions and solve the nonequilibrium Bethe-Salpeter equation to study the dynamics of magnetic correlations. This approach gives us new insights into the interplay between single-particle relaxation dynamics and the growth of antiferromagnetic correlations. Depending on the ramping time and the final value of the interaction, we find different dynamical behavior which we illustrate using a dynamical phase diagram. Of particular interest is the emergence of a transient short-range ordered regime characterized by the strong initial growth of antiferromagnetic correlations followed by a decay of correlations upon thermalization. The discussed phenomena can be probed in experiments with ultracold atoms in optical lattices.

Title:
Probing competing and intertwined orders with resonant inelastic x-ray scattering in the hole-doped cuprates
Authors:
Benjamin, David; Klich, Israel; Demler, Eugene
Publication:
Physical Review B, Volume 92, Issue 3, id.035151 (PhRvB Homepage)
Publication Date:
07/2015
Origin:
APS
PACS Keywords:
X-ray scattering
Abstract Copyright:
2015: American Physical Society
DOI:
10.1103/PhysRevB.92.035151
Bibliographic Code:
2015PhRvB..92c5151B

Abstract

We develop a formalism to study indirect resonant inelastic x-ray scattering (RIXS) in systems with itinerant electrons, accounting for the attraction between valence electrons and the positively charged core hole exactly, and apply this formalism to the hole-doped cuprate superconductors. We focus on the relationship between RIXS line shapes and band structure, including broken symmetries. We show that RIXS is capable of distinguishing between competing order parameters, establishing it as a useful probe of the pseudogap phase.

Title:
Observation and measurement of Higgs boson decays to WW* with the ATLAS detector
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Barreiro Guimarães da Costa, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2871 coauthors
Publication:
Physical Review D, Volume 92, Issue 1, id.012006 (PhRvD Homepage)
Publication Date:
07/2015
Origin:
APS
PACS Keywords:
Inelastic scattering: many-particle final states, Hadron-induced high- and super-high-energy interactions, Standard-model Higgs bosons
Abstract Copyright:
2015: CERN
DOI:
10.1103/PhysRevD.92.012006
Bibliographic Code:
2015PhRvD..92a2006A

Abstract

We report the observation of Higgs boson decays to W W* based on an excess over background of 6.1 standard deviations in the dilepton final state, where the Standard Model expectation is 5.8 standard deviations. Evidence for the vector-boson fusion (VBF) production process is obtained with a significance of 3.2 standard deviations. The results are obtained from a data sample corresponding to an integrated luminosity of 25 fb-1 from √{s }=7 and 8 TeV p p collisions recorded by the ATLAS detector at the LHC. For a Higgs boson mass of 125.36 GeV, the ratio of the measured value to the expected value of the total production cross section times branching fraction is 1.0 9-0.15+0.16(stat)-0.14 +0.17(syst) . The corresponding ratios for the gluon fusion and vector-boson fusion production mechanisms are 1.02 ±0.19 (stat)-0.18 +0.22(syst) and 1.2 7-0.40+0.44(stat)-0.21 +0.30(syst) , respectively. At √{s }=8 TeV , the total production cross sections are measured to be σ (g g →H →W W*)=4.6 ±0.9 (stat)-0.7 +0.8(syst) pb and σ (V B F H →W W*)=0.5 1-0.15+0.17(stat)-0.08 +0.13(syst) pb . The fiducial cross section is determined for the gluon-fusion process in exclusive final states with zero or one associated jet.

Title:
Search for long-lived, weakly interacting particles that decay to displaced hadronic jets in proton-proton collisions at √{s }=8 TeV with the ATLAS detector
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Barreiro Guimarães da Costa, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2819 coauthors
Publication:
Physical Review D, Volume 92, Issue 1, id.012010 (PhRvD Homepage)
Publication Date:
07/2015
Origin:
APS
PACS Keywords:
Models beyond the standard model, Limits on production of particles
Abstract Copyright:
2015: CERN
DOI:
10.1103/PhysRevD.92.012010
Bibliographic Code:
2015PhRvD..92a2010A

Abstract

A search for the decay of neutral, weakly interacting, long-lived particles using data collected by the ATLAS detector at the LHC is presented. This analysis uses the full data set recorded in 2012: 20.3 fb-1 of proton-proton collision data at √{s }=8 TeV . The search employs techniques for reconstructing decay vertices of long-lived particles decaying to jets in the inner tracking detector and muon spectrometer. Signal events require at least two reconstructed vertices. No significant excess of events over the expected background is found, and limits as a function of proper lifetime are reported for the decay of the Higgs boson and other scalar bosons to long-lived particles and for Hidden Valley Z' and Stealth SUSY benchmark models. The first search results for displaced decays in Z' and Stealth SUSY models are presented. The upper bounds of the excluded proper lifetimes are the most stringent to date.

Title:
Revealing the Empty-State Electronic Structure of Single-Unit-Cell FeSe /SrTiO3
Authors:
Huang, Dennis; Song, Can-Li; Webb, Tatiana A.; Fang, Shiang; Chang, Cui-Zu; Moodera, Jagadeesh S.; Kaxiras, Efthimios; Hoffman, Jennifer E.
Publication:
Physical Review Letters, Volume 115, Issue 1, id.017002 (PhRvL Homepage)
Publication Date:
07/2015
Origin:
APS
PACS Keywords:
Electronic structure, Superconducting films and low-dimensional structures
Abstract Copyright:
2015: American Physical Society
DOI:
10.1103/PhysRevLett.115.017002
Bibliographic Code:
2015PhRvL.115a7002H

Abstract

We use scanning tunneling spectroscopy to investigate the filled and empty electronic states of superconducting single-unit-cell FeSe deposited on SrTiO3(001 ) . We map the momentum-space band structure by combining quasiparticle interference imaging with decay length spectroscopy. In addition to quantifying the filled-state bands, we discover a Γ -centered electron pocket 75 meV above the Fermi energy. Our density functional theory calculations show the orbital nature of empty states at Γ and explain how the Se height is a key tuning parameter of their energies, with broad implications for electronic properties.

Title:
Search for a Heavy Neutral Particle Decaying to e μ , e τ , or μ τ in p p Collisions at √{s }=8 TeV with the ATLAS Detector
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Barreiro Guimarães da Costa, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2813 coauthors
Publication:
Physical Review Letters, Volume 115, Issue 3, id.031801 (PhRvL Homepage)
Publication Date:
07/2015
Origin:
APS
PACS Keywords:
Limits on production of particles, Extensions of electroweak gauge sector, Supersymmetric models, Supersymmetric partners of known particles
Abstract Copyright:
2015: CERN
DOI:
10.1103/PhysRevLett.115.031801
Bibliographic Code:
2015PhRvL.115c1801A

Abstract

This Letter presents a search for a heavy neutral particle decaying into an opposite-sign different-flavor dilepton pair, e±μ, e±τ, or μ±τ using 20.3 fb-1 of p p collision data at √{s }=8 TeV collected by the ATLAS detector at the LHC. The numbers of observed candidate events are compatible with the standard model expectations. Limits are set on the cross section of new phenomena in two scenarios: the production of ν˜ τ in R -parity-violating supersymmetric models and the production of a lepton-flavor-violating Z' vector boson.

Title:
Evidence of W γ γ Production in p p Collisions at √{s }=8 TeV and Limits on Anomalous Quartic Gauge Couplings with the ATLAS Detector
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Barreiro Guimarães da Costa, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2822 coauthors
Publication:
Physical Review Letters, Volume 115, Issue 3, id.031802 (PhRvL Homepage)
Publication Date:
07/2015
Origin:
APS
PACS Keywords:
Applications of electroweak models to specific processes, Inclusive production with identified leptons photons or other nonhadronic particles, Photons, W bosons
Abstract Copyright:
2015: CERN
DOI:
10.1103/PhysRevLett.115.031802
Bibliographic Code:
2015PhRvL.115c1802A

Abstract

This Letter reports evidence of triple gauge boson production p p →W (ℓν )γ γ +X , which is accessible for the first time with the 8 TeV LHC data set. The fiducial cross section for this process is measured in a data sample corresponding to an integrated luminosity of 20.3 fb-1 , collected by the ATLAS detector in 2012. Events are selected using the W boson decay to e ν or μ ν as well as requiring two isolated photons. The measured cross section is used to set limits on anomalous quartic gauge couplings in the high diphoton mass region.

Title:
Effect of additions of sodium hydroxide on the catalytic activity of partially deactivated skeletal nickel in reactions of the liquid-phase hydrogenation of sodium maleate in aqueous-organic media
Authors:
Lukin, M. V.; Afineevskii, A. V.
Affiliation:
AA(Ivanovo State University of Chemistry and Technology), AB(Ivanovo State University of Chemistry and Technology)
Publication:
Russian Journal of Physical Chemistry A, Volume 89, Issue 7, pp.1173-1177
Publication Date:
07/2015
Origin:
SPRINGER
Keywords:
liquid-phase hydrogenation, adsorption complex, catalyst activity, catalytic poison
Abstract Copyright:
(c) 2015: Pleiades Publishing, Ltd.
DOI:
10.1134/S0036024415070237
Bibliographic Code:
2015RJPCA..89.1173L

Abstract

The effect the concentration of sodium hydroxide has on the catalytic activity of skeletal nickel in reactions of the liquid-phase hydrogenation of sodium maleate in ternary methanol-water-sodium hydroxide solutions with a methanol content of 0.11 mole fractions and different concentrations of sodium hydroxide is studied. The key role of the solvent during changes in the activity of skeletal nickel in the hydrogenation reaction of sodium maleate is assumed, based on data on the redistribution of individual forms of adsorbed hydrogen.

Title:
3D structure of individual nanocrystals in solution by electron microscopy
Authors:
Park, Jungwon; Elmlund, Hans; Ercius, Peter; Yuk, Jong Min; Limmer, David T.; Chen, Qian; Kim, Kwanpyo; Han, Sang Hoon; Weitz, David A.; Zettl, A.; Alivisatos, A. Paul
Publication:
Science, Volume 349, Issue 6245, pp. 290-295 (2015). (Sci Homepage)
Publication Date:
07/2015
Category:
MAT SCI
Origin:
SCIENCE
Abstract Copyright:
(c) 2015: Science
DOI:
10.1126/science.aab1343
Bibliographic Code:
2015Sci...349..290P

Abstract

Knowledge about the synthesis, growth mechanisms, and physical properties of colloidal nanoparticles has been limited by technical impediments. We introduce a method for determining three-dimensional (3D) structures of individual nanoparticles in solution. We combine a graphene liquid cell, high-resolution transmission electron microscopy, a direct electron detector, and an algorithm for single-particle 3D reconstruction originally developed for analysis of biological molecules. This method yielded two 3D structures of individual platinum nanocrystals at near-atomic resolution. Because our method derives the 3D structure from images of individual nanoparticles rotating freely in solution, it enables the analysis of heterogeneous populations of potentially unordered nanoparticles that are synthesized in solution, thereby providing a means to understand the structure and stability of defects at the nanoscale.


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