Faculty Publications: March, 2013

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Title:   Improving dopant incorporation during femtosecond-laser doping of Si with a Se thin-film dopant precursor
Authors:   Smith, Matthew J.; Sher, Meng-Ju; Franta, Benjamin; Lin, Yu-Ting; Mazur, Eric; Gradečak, Silvija
Publication:   Applied Physics A, Online First (ApPhA Homepage)
Publication Date:   03/2013
Origin:   SPRINGER
Abstract Copyright:   (c) 2013: Springer-Verlag Berlin Heidelberg
DOI:   10.1007/s00339-013-7673-8
Bibliographic Code:   2013ApPhA.tmp..181S

Abstract

We study the dopant incorporation processes during thin-film fs-laser doping of Si and tailor the dopant distribution through optimization of the fs-laser irradiation conditions. Scanning electron microscopy, transmission electron microscopy, and profilometry are used to study the interrelated dopant incorporation and surface texturing mechanisms during fs-laser irradiation of Si coated with a Se thin-film dopant precursor. We show that the crystallization of Se-doped Si and micrometer-scale surface texturing are closely coupled and produce a doped surface that is not conducive to device fabrication. Next, we use this understanding of the dopant incorporation process to decouple dopant crystallization from surface texturing by tailoring the irradiation conditions. A low-fluence regime is identified in which a continuous surface layer of doped crystalline material forms in parallel with laser-induced periodic surface structures over many laser pulses. This investigation demonstrates the ability to tailor the dopant distribution through a systematic investigation of the relationship between fs-laser irradiation conditions, microstructure, and dopant distribution.

 

Title:   Multi-channel search for squarks and gluinos in √{s}=7{ TeV} pp collisions with the ATLAS detector at the LHC
Authors:   Aad, G.; Abajyan, T.; Abbott, B.;... Franklin, M.;... Guimaraes da Costa, J.;... Huth, J.;... Morii, M.;...; and 2887 coauthors.
Publication:   The European Physical Journal C, Volume 73, article id. #2362 (EPJC Homepage)
Publication Date:   03/2013
Origin:   SPRINGER
Abstract Copyright:   (c) 2013: CERN for the benefit of the ATLAS collaboration
DOI:   10.1140/epjc/s10052-013-2362-5
Bibliographic Code:   2013EPJC...73.2362A

Abstract

A search for supersymmetric particles in final states with zero, one, and two leptons, with and without jets identified as originating from b-quarks, in 4.7 fb-1 of √{s}=7{ TeV} pp collisions produced by the Large Hadron Collider and recorded by the ATLAS detector is presented. The search uses a set of variables carrying information on the event kinematics transverse and parallel to the beam line that are sensitive to several topologies expected in supersymmetry. Mutually exclusive final states are defined, allowing a combination of all channels to increase the search sensitivity. No deviation from the Standard Model expectation is observed. Upper limits at 95 % confidence level on visible cross-sections for the production of new particles are extracted. Results are interpreted in the context of the constrained minimal supersymmetric extension to the Standard Model and in supersymmetry-inspired models with diverse, high-multiplicity final states.

 

Title:   Measurement of ZZ production in pp collisions at sqrt{s}=7 TeV and limits on anomalous ZZZ and ZZγ couplings with the ATLAS detector
Authors:   Aad, G.; Abajyan, T.; Abbott, B.;... Franklin, M.;... Guimaraes da Costa, J.;... Huth, J.;... Morii, M.;...; and 2894 coauthors.
Publication:   Journal of High Energy Physics, Volume 2013, article id. #128
Publication Date:   03/2013
Origin:   SPRINGER
Keywords:   Hadron-Hadron Scattering
Abstract Copyright:   (c) 2013: Cern for the benefit of the ATLAS collaboration
DOI:   10.1007/JHEP03(2013)128
Bibliographic Code:   2013JHEP...03..128A

Abstract

A measurement of the ZZ production cross section in proton-proton collisions at sqrt{s}=7 TeV using data recorded by the ATLAS experiment at the Large Hadron Collider is presented. In a data sample corresponding to an integrated luminosity of 4.6 fb-1 collected in 2011, events are selected that are consistent either with two Z bosons decaying to electrons or muons or with one Z boson decaying to electrons or muons and a second Z boson decaying to neutrinos. The ZZ (*) → ℓ +-'+'- and ZZto {ell+}{ell-}ν overline{ν} cross sections are measured in restricted phase-space regions. These results are then used to derive the total cross section for ZZ events produced with both Z bosons in the mass range 66 to 116 GeV, σ_{ZZ}^{tot} = 6.7 ± 0.7 ( {stat.} )_{-0.3}^{+0.4} ( {syst.} ) ± 0.3 ( {lumi.} ) pb, which is consistent with the Standard Model prediction of 5.89_{-0.18}^{+0.22 } pb calculated at next-to-leading order in QCD. The normalized differential cross sections in bins of various kinematic variables are presented. Finally, the differential event yield as a function of the transverse momentum of the leading Z boson is used to set limits on anomalous neutral triple gauge boson couplings in ZZ production.[Figure not available: see fulltext.]

 

Title:   Measurement of hard double-parton interactions in W(→ℓν) + 2-jet events at sqrt{s},=7  TeV with the ATLAS detector
Authors:   Aad, G.; Abajyan, T.; Abbott, B.;... Franklin, M.;... Guimaraes da Costa, J.;... Huth, J.;... Morii, M.;...; and 2910 coauthors.
Publication:   New Journal of Physics, Volume 15, Issue 3, id. 033038 (2013).
Publication Date:   03/2013
Origin:   IOP
DOI:   10.1088/1367-2630/15/3/033038
Bibliographic Code:   2013NJPh...15c3038A

Abstract

The production of W bosons in association with two jets in proton–proton collisions at a centre-of-mass energy of \sqrt {s} = 7\,{ {TeV}} has been analysed for the presence of double-parton interactions using data corresponding to an integrated luminosity of 36 pb‑1, collected with the ATLAS detector at the Large Hadron Collider. The fraction of events arising from double-parton interactions, f(D)DP, has been measured through the pT balance between the two jets and amounts to f(D)DP = 0.08 ± 0.01 (stat.) ± 0.02 (sys.) for jets with transverse momentum pT > 20 GeV and rapidity |y| < 2.8. This corresponds to a measurement of the effective area parameter for hard double-parton interactions of σeff = 15 ± 3 (stat.) +5‑3 (sys.) mb.

 

Title:   Search for charged Higgs bosons through the violation of lepton universality in toverline{t} events using pp collision data at sqrt{s}=7 TeV with the ATLAS experiment
Authors:   Aad, G.; Abajyan, T.; Abbott, B.;... Franklin, M.;... Guimaraes da Costa, J.;... Huth, J.;... Morii, M.;...; and 2894 coauthors.
Publication:   Journal of High Energy Physics, Volume 2013, article id. #76
Publication Date:   03/2013
Origin:   SPRINGER
Keywords:   Hadron-Hadron Scattering
Abstract Copyright:   (c) 2013: Cern for the benefit of the ATLAS collaboration
DOI:   10.1007/JHEP03(2013)076
Bibliographic Code:   2013JHEP...03..076A

Abstract

In several extensions of the Standard Model, the top quark can decay into a bottom quark and a light charged Higgs boson H +, t → bH +, in addition to the Standard Model decay t → bW. Since W bosons decay to the three lepton generations equally, while H + maypredominantlydecayinto τν, charged Higgs bosons can be searched for using the violation of lepton universality in top quark decays. The analysis in this paper is based on 4.6 fb-1 of proton-proton collision data at sqrt{s}=7 TeV collected by the ATLAS experiment at the Large Hadron Collider. Signatures containing leptons ( e or μ) and/or a hadronically decaying τ ( τ had) are used. Event yield ratios between e + τ had and e + μ, as well as between μ + τ had and μ + e, final states are measured in the data and compared to predictions from simulations. This ratio-based method reduces the impact of systematic uncertainties in the analysis. No significant deviation from the Standard Model predictions is observed. With the assumption that the branching fraction {B} ( H + → τν) is 100%, upper limits in the range 3.2%-4.4% can be placed on the branching fraction {B} ( t → bH +) for charged Higgs boson masses m H+ in the range 90-140 GeV. After combination with results from a search for charged Higgs bosons in toverline{t} decays using the τ had + jets final state, upper limits on {B} ( t → bH +) can be set in the range 0.8%-3.4%, for m H+ in the range 90-160 GeV.[Figure not available: see fulltext.]

 

Title:   Search for CP violation in the decays D±→KS0K±, Ds±→KS0K±, and Ds±→KS0π±
Authors:   Lees, J. P.; Poireau, V. ;Tisserand, V.;... Morii, M.;...; and 345 coauthors.
Publication:   Physical Review D, vol. 87, Issue 5, id. 052012 (PhRvD Homepage)
Publication Date:   03/2013
Origin:   ADS
PACS Keywords:   Charge conjugation, parity, time reversal, and other discrete symmetries, Decays of charmed mesons, Charmed mesons
DOI:   10.1103/PhysRevD.87.052012
Bibliographic Code:   2013PhRvD..87e2012L

Abstract

We report a search for CP violation in the decay modes D±→KS0K±, Ds±→KS0K±, and Ds±→KS0π± using a data set corresponding to an integrated luminosity of 469fb-1 collected with the BABAR detector at the PEP-II asymmetric energy e+e- storage rings. The decay rate CP asymmetries, ACP, are determined to be (+0.13±0.36(stat)±0.25(syst))%, (-0.05±0.23(stat)±0.24(syst))%, and (+0.6±2.0(stat)±0.3(syst))%, respectively. These measurements are consistent with zero, and also with the Standard Model prediction [(-0.332±0.006)% for the D±→KS0K± and Ds±→KS0K± modes, and (+0.332±0.006)% for the Ds±→KS0π± mode]. They are the most precise determinations to date.

 

Title:   Observation of direct CP violation in the measurement of the Cabibbo-Kobayashi-Maskawa angle γ with B±→D(*)K(*)± decays
Authors:   Lees, J. P.; Poireau, V. ;Tisserand, V.;... Morii, M.;...; and 350 coauthors.
Publication:   Physical Review D, vol. 87, Issue 5, id. 052015 (PhRvD Homepage)
Publication Date:   03/2013
Origin:   APS
PACS Keywords:   Decays of bottom mesons, Charge conjugation, parity, time reversal, and other discrete symmetries, Determination of Kobayashi-Maskawa matrix elements, Bottom mesons
DOI:   10.1103/PhysRevD.87.052015
Bibliographic Code:   2013PhRvD..87e2015L

Abstract

We report the determination of the Cabibbo-Kobayashi-Maskawa CP-violating angle γ through the combination of various measurements involving B±→DK±, B±→D*K±, and B±→DK decays performed by the BABAR experiment at the PEP-II e+e- collider at SLAC National Accelerator Laboratory. Using up to 474 million BB¯ pairs, we obtain γ=(69-16+17)° modulo 180°. The total uncertainty is dominated by the statistical component, with the experimental and amplitude-model systematic uncertainties amounting to ±4°. The corresponding two-standard-deviation region is 41°<γ<102°. This result is inconsistent with γ=0 with a significance of 5.9 standard deviations.

 

Title:   Dissipative Preparation of Spin Squeezed Atomic Ensembles in a Steady State
Authors:   Dalla Torre, Emanuele G.; Otterbach, Johannes; Demler, Eugene; Vuletic, Vladan; Lukin, Mikhail D.
Publication:   Physical Review Letters, vol. 110, Issue 12, id. 120402 (PhRvL Homepage)
Publication Date:   03/2013
Origin:   ADS
PACS Keywords:   Nonclassical states of the electromagnetic field, including entangled photon states; quantum state engineering and measurements, Decoherence; open systems; quantum statistical methods, Cavity quantum electrodynamics; micromasers
DOI:   10.1103/PhysRevLett.110.120402
Bibliographic Code:   2013PhRvL.110l0402D

Abstract

We present and analyze a new approach for the generation of atomic spin-squeezed states. Our method involves the collective coupling of an atomic ensemble to a decaying mode of an open optical cavity. We demonstrate the existence of a collective atomic dark state, decoupled from the radiation field. By explicitly constructing this state we find that it can feature spin squeezing bounded only by the Heisenberg limit. We show that such dark states can be deterministically prepared via dissipative means, thus turning dissipation into a resource for entanglement. The scaling of the phase sensitivity taking realistic imperfections into account is discussed.
 

Title:   Search for a Two-Higgs-Boson Doublet Using a Simplified Model in pp¯ Collisions at s=1.96TeV
Authors:   Aaltonen, T.; Adelman, J.; Álvarez González, B.;... Franklin, M.;... Guimaraes da Costa, J....; and 473 coauthors.
Publication:   Physical Review Letters, vol. 110, Issue 12, id. 121801 (PhRvL Homepage)
Publication Date:   03/2013
Origin:   ADS
PACS Keywords:   Extensions of electroweak Higgs sector, Limits on production of particles
DOI:   10.1103/PhysRevLett.110.121801
Bibliographic Code:   2013PhRvL.110l1801A

Abstract

We present a search for new particles in an extension to the standard model that includes a heavy Higgs boson (H0), a lighter charged Higgs boson (H±), and an even lighter Higgs boson h0, with decays leading to a W-boson pair and a bottom-antibottom quark pair in the final state. We use events with exactly one lepton, missing transverse momentum, and at least four jets in data corresponding to an integrated luminosity of 8.7fb-1 collected by the CDF II detector in proton-antiproton collisions at s=1.96TeV. We find the data to be consistent with standard model predictions and report the results in terms of a simplified Higgs-cascade-decay model, setting 95% confidence level upper limits on the product of cross section and branching fraction from 1.3 pb to 15 fb as a function of H0 and H± masses for mh0=126GeV/c2.

 

Title:   Search for Resonant Top-Antitop Production in the Lepton Plus Jets Decay Mode Using the Full CDF Data Set
Authors:   Aaltonen, T.; Amerio, S.; Amidei, D.;... Franklin, M.;... Guimaraes da Costa, J....; and 406 coauthors.
Publication:   Physical Review Letters, vol. 110, Issue 12, id. 121802 (PhRvL Homepage)
Publication Date:   03/2013
Origin:   ADS
PACS Keywords:   Limits on production of particles, Top quarks, Other gauge bosons
DOI:   10.1103/PhysRevLett.110.121802
Bibliographic Code:   2013PhRvL.110l1802A

Abstract

This Letter reports a search for a narrow resonant state decaying into two W bosons and two b quarks where one W boson decays leptonically and the other decays into a quark-antiquark pair. The search is particularly sensitive to top-antitop resonant production. We use the full data sample of proton-antiproton collisions at a center-of-mass energy of 1.96 TeV collected by the CDF II detector at the Fermilab Tevatron, corresponding to an integrated luminosity of 9.45fb-1. No evidence for resonant production is found, and upper limits on the production cross section times branching ratio for a narrow resonant state are extracted. Within a specific benchmark model, we exclude a Z' boson with mass, MZ', below 915GeV/c2 decaying into a top-antitop pair at the 95% credibility level assuming a Z' boson decay width of ΓZ'=0.012MZ'. This is the most sensitive search for a narrow qq¯-initiated tt¯ resonance in the mass region below 750GeV/c2.

 

Title:   One-Particle Measurement of the Antiproton Magnetic Moment
Authors:   DiSciacca, J.; Marshall, M.; Marable, K.; Gabrielse, G.; Ettenauer, S.; Tardiff, E.; Kalra, R.; Fitzakerley, D. W.; George, M. C.; Hessels, E. A.; Storry, C. H.; Weel, M.; Grzonka, D.; Oelert, W.; Sefzick, T.
Publication:   Physical Review Letters, vol. 110, Issue 13, id. 130801 (PhRvL Homepage)
Publication Date:   03/2013
Origin:   APS
PACS Keywords:   Protons and neutrons, Charge conjugation, parity, time reversal, and other discrete symmetries, Electric and magnetic moments, Ion trapping
DOI:   10.1103/PhysRevLett.110.130801
Bibliographic Code:   2013PhRvL.110m0801D

Abstract

For the first time a single trapped antiproton (p¯) is used to measure the p¯ magnetic moment μp¯. The moment μp¯=μp¯S/(ℏ/2) is given in terms of its spin S and the nuclear magneton (μN) by μp¯/μN=-2.792845±0.000012. The 4.4 parts per million (ppm) uncertainty is 680 times smaller than previously realized. Comparing to the proton moment measured using the same method and trap electrodes gives μp¯/μp=-1.000000±0.000005 to 5 ppm, for a proton moment μp=μpS/(ℏ/2), consistent with the prediction of the CPT theorem.

 

Title:   Coherence and Raman Sideband Cooling of a Single Atom in an Optical Tweezer
Authors:   Thompson, J. D.; Tiecke, T. G.; Zibrov, A. S.; Vuletić, V.; Lukin, M. D.
Publication:   Physical Review Letters, vol. 110, Issue 13, id. 133001 (PhRvL Homepage)
Publication Date:   03/2013
Origin:   APS
PACS Keywords:   Atom cooling methods
DOI:   10.1103/PhysRevLett.110.133001
Bibliographic Code:   2013PhRvL.110m3001T

Abstract

We investigate quantum control of a single atom in a tightly focused optical tweezer trap. We show that inevitable spatially varying polarization gives rise to significant internal-state decoherence but that this effect can be mitigated by an appropriately chosen magnetic bias field. This enables Raman sideband cooling of a single atom close to its three-dimensional ground state (vibrational quantum numbers n¯x=n¯y=0.01, n¯z=8) even for a trap beam waist as small as w=900nm. The small atomic wave packet with δx=δy=24nm and δz=270nm represents a promising starting point for future hybrid quantum systems where atoms are placed in close proximity to surfaces.

 

Title:   Microscopic Theory of Resonant Soft-X-Ray Scattering in Materials with Charge Order: The Example of Charge Stripes in High-Temperature Cuprate Superconductors
Authors:   Benjamin, David; Abanin, Dmitry; Abbamonte, Peter; Demler, Eugene
Publication:   Physical Review Letters, vol. 110, Issue 13, id. 137002 (PhRvL Homepage)
Publication Date:   03/2013
Origin:   APS
PACS Keywords:   Charge-density-wave systems, Electronic structure, X-ray scattering
DOI:   10.1103/PhysRevLett.110.137002
Bibliographic Code:   2013PhRvL.110m7002B

Abstract

We present a microscopic theory of resonant soft-x-ray scattering that accounts for the delocalized character of valence electrons. Unlike past approaches based on local form factors, our functional determinant method treats realistic band structures. This method builds upon earlier theoretical work in mesoscopic physics and accounts for excitonic effects as well as the orthogonality catastrophe arising from interaction between the core hole and the valence band electrons. We show that the two-peak structure observed near the O K edge of stripe-ordered La1.875Ba0.125CuO4 is due to dynamical nesting within the canonical cuprate band structure. Our results provide evidence for reasonably well-defined, high-energy quasiparticles in cuprates and establish resonant soft-x-ray scattering as a bulk-sensitive probe of the electron quasiparticles.

 

Title:   Hydrodynamics of Hemostasis in Sickle-Cell Disease
Authors:   Cohen, S. I. A.; Mahadevan, L.
Publication:   Physical Review Letters, vol. 110, Issue 13, id. 138104 (PhRvL Homepage)
Publication Date:   03/2013
Origin:   APS
PACS Keywords:   Large-scale biological processes and integrative biophysics, Fluid transport and rheology, Hemodynamics, Diseases
DOI:   10.1103/PhysRevLett.110.138104
Bibliographic Code:   2013PhRvL.110m8104C

Abstract

Vaso-occlusion, the stoppage of blood flow in sickle-cell disease, is a complex dynamical process spanning multiple time and length scales. Motivated by recent ex vivo microfluidic measurements of hemostasis using blood from sickle-cell patients, we develop a multiphase model that couples the kinetics and hydrodynamics of a flowing suspension of normal and sickled cells in a fluid. We use the model to derive expressions for the cell velocities and concentrations that quantify the hydrodynamics of hemostasis, and provide simple criteria as well as a phase diagram for occlusion, consistent with our simulations and earlier observations.

 

Title:   Fractional Quantum Hall Phase Transitions and Four-flux Composite Fermions in Graphene
Authors:   Feldman, Benjamin E.; Levin, Andrei J.; Krauss, Benjamin; Abanin, Dmitry; Halperin, Bertrand. I.; Smet, Jurgen H.; Yacoby, Amir
Publication:   eprint arXiv:1303.0838
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   Condensed Matter - Mesoscale and Nanoscale Physics
Bibliographic Code:   2013arXiv1303.0838F

Abstract

Graphene and its multilayers have attracted considerable interest owing to the fourfold spin and valley degeneracy of their charge carriers, which enables the formation of a rich variety of broken-symmetry states and raises the prospect of controlled phase transitions among them. In especially clean samples, electron-electron interactions were recently shown to produce surprising patterns of symmetry breaking and phase transitions in the integer quantum Hall regime. Although a series of robust fractional quantum Hall states was also recently observed in graphene, their rich phase diagram and tunability have yet to be fully explored. Here we report local electronic compressibility measurements of ultraclean suspended graphene that reveal a multitude of fractional quantum Hall states surrounding filling factors v = -1/2 and -1/4. In several of these states, we observe phase transitions that indicate abrupt changes in the underlying order and are marked by a narrow region of negative compressibility that cuts across the incompressible peak. Remarkably, as filling factor approaches v = -1/2, we observe additional oscillations in compressibility that appear to be related to the phase transitions and persist to within 2.5% of v = -1/2. We use a simple model based on crossing Landau levels of composite particles with different internal degrees of freedom to explain many qualitative features of the experimental data. Our results add to the diverse array of correlated states observed in graphene and demonstrate substantial control over their order parameters, showing that graphene serves as an excellent platform to study correlated electron phases of matter.

 

Title:   Resolving an Individual One-Proton Spin Flip to Determine a Proton Spin State
Authors:   DiSciacca, J.; Marshall, M.; Marable, K.; Gabrielse, G.
Publication:   eprint arXiv:1303.0924
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   Physics - Atomic Physics
Comment:   4 pages, 7 figures
Bibliographic Code:   2013arXiv1303.0924D

Abstract

Previous measurements with a single trapped proton or antiproton detected spin resonance from the increased scatter of frequency measurements caused by many spin flips. Here a measured correlation confirms that individual spin transitions and states are detected instead. The high fidelity suggests that it may be possible to use quantum jump spectroscopy to measure the p and \pbar magnetic moments much more precisely.


 

Title:   Local Spin Susceptibilities of Low-Dimensional Electron Systems
Authors:   Stano, Peter; Klinovaja, Jelena; Yacoby, Amir; Loss, Daniel
Publication:   eprint arXiv:1303.1151
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   Condensed Matter - Mesoscale and Nanoscale Physics
Comment:   11 pages, 12 figures
Bibliographic Code:   2013arXiv1303.1151S

Abstract

We investigate, assess, and suggest possibilities for a measurement of the local spin susceptibility of a conducting low-dimensional electron system. The basic setup of the experiment we envisage is a source-probe one. Locally induced spin density (e.g. by a magnetized atomic force microscope tip) extends in the medium according to its spin susceptibility. The induced magnetization can be detected as a dipolar magnetic field, for instance, by an ultra-sensitive nitrogen-vacancy center based detector, from which the spatial structure of the spin susceptibility can be deduced. We find that one-dimensional systems, such as semiconducting nanowires or carbon nanotubes, are expected to yield a measurable signal. The signal in a two-dimensional electron gas is weaker, though materials with high enough $g$-factor (such as InGaAs) seem promising for successful measurements.


 

Title:   Gate defined wires in HgTe quantum wells: from Majorana fermions to spintronics
Authors:   Reuther, Johannes; Alicea, Jason; Yacoby, Amir
Publication:   eprint arXiv:1303.1207
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity
Comment:   19 pages, 9 figures
Bibliographic Code:   2013arXiv1303.1207R

Abstract

We introduce a promising new platform for Majorana zero-modes and various spintronics applications based on gate-defined wires in HgTe quantum wells. Due to the Dirac-like band structure for HgTe the physics of such systems differs markedly from that of conventional quantum wires. Most strikingly, we show that the subband parameters for gate-defined HgTe wires exhibit exquisite tunability: modest gate voltage variation allows one to modulate the Rashba spin-orbit energies from zero up to ~30K, and the effective g-factors from zero up to giant values exceeding 600. The large achievable spin-orbit coupling and g-factors together allow one to access Majorana modes in this setting at exceptionally low magnetic fields while maintaining robustness against disorder. As an additional benefit, gate-defined wires (in HgTe or other settings) should greatly facilitate the fabrication of networks for refined transport experiments used to detect Majoranas, as well as the realization of non-Abelian statistics and quantum information devices.


 

Title:   Double-Disk Dark Matter
Authors:   Fan, JiJi; Katz, Andrey; Randall, Lisa; Reece, Matthew
Publication:   eprint arXiv:1303.1521
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   Astrophysics - Cosmology and Extragalactic Astrophysics, Astrophysics - Galaxy Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Phenomenology
Comment:   37 pages, 13 figures
Bibliographic Code:   2013arXiv1303.1521F

Abstract

Based on observational tests and constraints on halo structure, dark matter is generally taken to be cold and essentially collisionless. On the other hand, given the large number of particles and forces in the visible world, a more complex dark sector could be a reasonable or even likely possibility. This hypothesis leads to testable consequences, perhaps portending the discovery of a rich hidden world neighboring our own. We consider a scenario that readily satisfies current bounds that we call Partially Interacting Dark Matter (PIDM). This scenario contains self-interacting dark matter, but it is not the dominant component. Even if PIDM contains only a fraction of the net dark matter density, comparable to the baryonic fraction, the subdominant component's interactions can lead to interesting and potentially observable consequences. Our primary focus will be the special case of Double-Disk Dark Matter (DDDM), in which self-interactions allow the dark matter to lose enough energy to lead to dynamics similar to those in the baryonic sector. We explore a simple model in which DDDM can cool efficiently and form a disk within galaxies, and we evaluate some of the possible observational signatures. The most prominent signal of such a scenario could be an enhanced indirect detection signature with a distinctive spatial distribution. Even though subdominant, the enhanced density at the center of the galaxy and possibly throughout the plane of the galaxy can lead to large boost factors, and could even explain a signature as large as the 130 GeV Fermi line. Such scenarios also predict additional dark radiation degrees of freedom that could soon be detectable and would influence the interpretation of future data, such as that from Planck and from the Gaia satellite. We consider this to be the first step toward exploring a rich array of new possibilities for dark matter dynamics.


 

Title:   Charge ordering in metals with antiferromagnetic spin correlations
Authors:   Sachdev, Subir; La Placa, Rolando
Publication:   eprint arXiv:1303.2114
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   Condensed Matter - Superconductivity, Condensed Matter - Strongly Correlated Electrons
Comment:   5 pages, 4 figures; (v2) added refs and clarifications
Bibliographic Code:   2013arXiv1303.2114S

Abstract

Metals with antiferromagnetic spin correlations have an instability to the superconductivity of spin-singlet Cooper pairs with d symmetry (for the Fermi surface of the cuprates). Metlitski et al. (arXiv:1005.1288) noted that in two dimensions, in the low energy continuum theory, this superconductivity is degenerate with a charge density wave ordering which has a local d symmetry under rotations about the lattice points. We present a momentum-space Hartree-Fock computation on a simple lattice model, and find that the d symmetry is dominant for a range of small ordering wavevectors including those observed in recent experiments. We propose a charge order parameter for the underdoped cuprates.


 

Title:   Chiral Liouville Gravity
Authors:   Compère, Geoffrey; Song, Wei; Strominger, Andrew
Publication:   eprint arXiv:1303.2660
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   High Energy Physics - Theory, General Relativity and Quantum Cosmology
Comment:   17 pages
Bibliographic Code:   2013arXiv1303.2660C

Abstract

Classical two-dimensional Liouville gravity is often considered in conformal gauge which has a residual left and right Virasoro symmetry algebra. We consider an alternate, chiral, gauge which has a residual right Virasoro Kac-Moody algebra, and no left Virasoro algebra. The Kac-Moody zero mode is the left-moving energy. Dirac brackets of the constrained Hamiltonian theory are derived, and the residual symmetries are shown to be generated by integrals of the conserved chiral currents. The central charge and Kac-Moody level are computed. The possible existence of a corresponding quantum theory is discussed.


 

Title:   New Boundary Conditions for AdS3
Authors:   Compère, Geoffrey; Song, Wei; Strominger, Andrew
Publication:   eprint arXiv:1303.2662
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   High Energy Physics - Theory, General Relativity and Quantum Cosmology
Comment:   34 pages
Bibliographic Code:   2013arXiv1303.2662C

Abstract

New chiral boundary conditions are found for quantum gravity with matter on AdS3. The associated asymptotic symmetry group is generated by a single right-moving U(1) Kac-Moody-Virasoro algebra with c_R = 3l/2G. The Kac-Moody zero mode generates global left-moving translations and equals, for a BTZ black hole, the sum of the total mass and spin. The level is positive about the global vacuum and negative in the black hole sector, corresponding to ergosphere formation. Realizations arising in Chern-Simons gravity and string theory are analyzed. The new boundary conditions are shown to naturally arise for warped AdS3 in the limit that the warp parameter is taken to zero.


 

Title:   Monopoles in 2+1-dimensional conformal field theories with global U(1) symmetry
Authors:   Pufu, Silviu S.; Sachdev, Subir
Publication:   eprint arXiv:1303.3006
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   High Energy Physics - Theory, Condensed Matter - Strongly Correlated Electrons
Comment:   20 pages, 1 figure
Bibliographic Code:   2013arXiv1303.3006P

Abstract

In 2+1-dimensional conformal field theories with a global U(1) symmetry, monopoles can be introduced through a background gauge field that couples to the U(1) conserved current. We use the state-operator correspondence to calculate scaling dimensions of such monopoles. We obtain the next-to-leading term in the 1/N_b expansion of the Wilson-Fisher fixed point in the theory of N_b complex bosons.


 

Title:   A Dark-Disk Universe
Authors:   Fan, JiJi; Katz, Andrey; Randall, Lisa; Reece, Matthew
Publication:   eprint arXiv:1303.3271
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   High Energy Physics - Phenomenology, Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:   Concise companion to arXiv:1303.1521
Bibliographic Code:   2013arXiv1303.3271F

Abstract

We point out that current constraints on dark matter imply only that the majority of dark matter is cold and collisionless. A subdominant fraction of dark matter could have much stronger interactions. In particular, it could interact in a manner that dissipates energy, thereby cooling into a rotationally-supported disk, much as baryons do. We call this proposed new dark matter component Double-Disk Dark Matter (DDDM). We argue that DDDM could constitute a fraction of all matter roughly as large as the fraction in baryons, and that it could be detected through its gravitational effects on the motion of stars in galaxies, for example. Furthermore, if DDDM can annihilate to gamma rays, it would give rise to an indirect detection signal distributed across the sky that differs dramatically from that predicted for ordinary dark matter. DDDM and more general partially interacting dark matter scenarios provide a large unexplored space of testable new physics ideas.


 

Title:   Quantum flutter versus Bloch oscillations in one-dimensional quantum liquids out of equilibrium
Authors:   Knap, Michael; Mathy, Charles J. M.; Zvonarev, Mikhail B.; Demler, Eugene
Publication:   eprint arXiv:1303.3583
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   Condensed Matter - Quantum Gases
Bibliographic Code:   2013arXiv1303.3583K

Abstract

We study the dynamics of an impurity of finite mass injected into a one-dimensional quantum liquid at zero temperature, either at finite velocity or at zero velocity with a force driving the impurity. We obtain accurate results using numerical simulations based on matrix product states, and find that in both cases, the impurity undergoes oscillations, however the physical mechanism is different: the driven impurity undergoes Bloch oscillations by following the ground state branch while continuously emitting phonons, whereas the undriven impurity undergoes coherent quantum oscillations at an emergent energy scale, called quantum flutter in previous work, whose amplitude grows with increasing initial velocity. We find these results to be independent of whether the system is integrable or not, and robust to changes in the microscopics of the model, suggesting that they are universal.


 

Title:   The Pan-STARRS 1 Photometric Reference Ladder, Release 12.0
Authors:   Magnier, E. A.; Schlafly, E.; Finkbeiner, D.; Juric, M.; Tonry, J. L.; Burgett, W. S.; Chambers, K. C.; Flewelling, H. A.; Kaiser, N.; Kudritzki, R.-P.; Morgan, J. S.; Price, P. A.; Sweeney, W. E.; Stubbs, C. W.
Publication:   eprint arXiv:1303.3634
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   Astrophysics - Instrumentation and Methods for Astrophysics
Comment:   14 pages, 8 figures, download data from http://ipp.ifa.hawaii.edu, accepted for publication in ApJ Supplements 2013.03.08
Bibliographic Code:   2013arXiv1303.3634M

Abstract

As of 2012 Jan 21, the Pan-STARRS 1 3\pi Survey has observed the 3/4 of the sky visible from Hawaii with a minimum of 2 and mean of 7.6 observations in 5 filters, g_p1, r_p1, i_p1, z_p1, y_p1. Now at the end of the second year of the mission, we are in a position to make an initial public release of a portion of this unprecedented dataset. This article describes the PS1 Photometric Ladder, Release 12.01 This is the first of a series of data releases to be generated as the survey coverage increases and the data analysis improves. The Photometric Ladder has rungs every hour in RA and at 4 intervals in declination. We will release updates with increased area coverage (more rungs) from the latest dataset until the PS1 survey and the final re-reduction are completed. The currently released catalog presents photometry of \approx 1000 objects per square degree in the rungs of the ladder. Saturation occurs at g_p1, r_p1, i_p1 \approx 13.5; z_p1 \approx 13.0; and y_p1 \approx 12.0. Photometry is provided for stars down to g_p1, r_p1, i_p1 \approx 19.1 in the AB system. This data release depends on the rigid `Ubercal' photometric calibration using only the photometric nights, with systematic uncertainties of (8.0, 7.0, 9.0, 10.7, 12.4) millimags in (g_p1, r_p1, i_p1, z_p1, y_p1). Areas covered only with lower quality nights are also included, and have been tied to the Ubercal solution via relative photometry; photometric accuracy of the non-photometric regions is lower and should be used with caution.


 

Title:   Vortex Lattices and Crystalline Geometries
Authors:   Bao, Ning; Harrison, Sarah; Kachru, Shamit; Sachdev, Subir
Publication:   eprint arXiv:1303.4390
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   High Energy Physics - Theory, Condensed Matter - Strongly Correlated Electrons
Comment:   25 pages, 4 figures
Bibliographic Code:   2013arXiv1303.4390B

Abstract

We consider $AdS_2 \times R^2$ solutions supported by a magnetic field, such as those which arise in the near-horizon limit of magnetically charged $AdS_4$ Reissner-Nordstrom black branes. In the presence of an electrically charged scalar field, such magnetic solutions can be unstable to spontaneous formation of a vortex lattice. We solve the coupled partial differential equations which govern the charged scalar, gauge field, and metric degrees of freedom to lowest non-trivial order in an expansion around the critical point, and discuss the corrections to the free energy and thermodynamic functions arising from the formation of the lattice. We describe how such solutions can also be interpreted, via S-duality, as characterizing infrared crystalline phases of conformal field theories doped by a chemical potential, but in zero magnetic field; the doped conformal field theories are dual to geometries that exhibit dynamical scaling and hyperscaling violation.


 

Title:   A search for flavor-changing non-standard neutrino interactions by MINOS
Authors:   MINOS Collaboration; Adamson, P.; Barr, G.; Bishai, M.;... Feldman, G. J.;... and 98 coauthors.
Publication:   eprint arXiv:1303.5314
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   High Energy Physics - Experiment, High Energy Physics - Phenomenology
Bibliographic Code:   2013arXiv1303.5314M

Abstract

We report new constraints on flavor-changing non-standard neutrino interactions (NSI) using data from the MINOS experiment. We analyzed a combined set of beam neutrino and antineutrino data, and found no evidence for deviations from standard neutrino mixing. The observed energy spectra constrain the NSI parameter to the range $-0.20 < \varepsilon_{\mu\tau} < 0.07\;\text{(90% C.L.)}$


 

Title:   Fractional and integer quantum Hall effects in the zeroth Landau level in graphene
Authors:   Abanin, Dmitry A.; Feldman, Benjamin E.; Yacoby, Amir; Halperin, Bertrand I.
Publication:   eprint arXiv:1303.5372
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Strongly Correlated Electrons
Comment:   19 pages, 1 figure
Bibliographic Code:   2013arXiv1303.5372A

Abstract

Experiments on the fractional quantized Hall effect in the zeroth Landau level of graphene have revealed some striking differences between filling factors in the ranges 0<|\nu|<1 and 1<|\nu|<2. We argue that these differences can be largely understood as a consequence of the effects of terms in the Hamiltonian which break SU(2) valley symmetry, which we find to be important for |\nu|<1 but negligible for |\nu| >1. The effective absence of valley anisotropy for |\nu|>1 means that states with odd numerator, e.g. |\nu|=5/3 or 7/5 can accommodate charged excitations in the form of large valley skyrmions, which have a low energy cost, and may be easily induced by coupling to impurities. The absence of observed quantum Hall states at these fractions is likely due to the effects of valley skyrmions. For |\nu|<1, the anisotropy terms favor phases in which electrons occupy states with opposite spins, similar to the antiferromagnetic state previously hypothesized to be the ground state at \nu=0. The anisotropy and Zeeman energies suppress large-area skyrmions, so that quantized Hall states can be observable at a set of fractions similar to those in GaAs two-dimensional electron systems. In a perpendicular magnetic field B, the competition between the Coulomb energy, which varies as B^{1/2}, and the Zeeman energy, which varies as B, can explain the observation of apparent phase transitions as a function of B for fixed \nu, as transitions between states with different degrees of spin polarization. In addition to an analysis of various fractional states, and an examination of the effects of disorder on valley skyrmions, we present new experimental data for the energy gaps at integer fillings \nu=0 and \nu= -1, as a function of magnetic field, and we examine the possibility that valley-skyrmions may account for the smaller energy gaps observed at \nu= -1.


 

Title:   Defects on cylinders: superfluid helium films and bacterial cell walls
Authors:   Nelson, David R.; Amir, Ariel
Publication:   eprint arXiv:1303.5896
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   Condensed Matter - Soft Condensed Matter, Condensed Matter - Materials Science, Condensed Matter - Statistical Mechanics
Comment:   Lectures given by D. R. Nelson at the Les Houches School on "Soft Interfaces", July 2-27, 2012
Bibliographic Code:   2013arXiv1303.5896N

Abstract

There is a deep analogy between the physics of crystalline solids and the behavior of superfluids, dating back to pioneering work of Phillip Anderson, Paul Martin and others. The stiffness to shear deformations in a periodic crystal resembles the superfluid density that controls the behavior of supercurrents in neutral superfluids such as He^4. Dislocations in solids have a close analogy with quantized vortices in superfluids. Remarkable recent experiments on the way rod-shaped bacteria elongate their cell walls have focused attention on the dynamics and interactions of point-like dislocation defects in partially ordered cylindrical crystalline monolayers. In these lectures, we review the physics of superfluid helium films on cylinders and discuss how confinement in one direction affects vortex interactions with supercurrents. Although there are similarities with the way dislocations respond to strains on cylinders, important differences emerge, due to the vector nature of the topological charges characterizing the dislocations.


 

Title:   A signature of quantum spin liquids in superconductors with topological order
Authors:   Chowdhury, Debanjan; Swingle, Brian; Sachdev, Subir
Publication:   eprint arXiv:1303.6288
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity, High Energy Physics - Theory
Comment:   4.25 pages, 2 figures
Bibliographic Code:   2013arXiv1303.6288C

Abstract

We describe anomalous behavior of the London penetration depth (\lambda_L) across a quantum phase transition between a superconductor and a superconductor coexisting with a Z_2 spin liquid. Our study is motivated by the physics of heavy fermion materials, where it has been argued that the heavy Fermi liquid (FL) phase in a Kondo lattice model of conduction electrons and localized moments can be driven into a fractionalized Fermi liquid (FL*) phase in spatial dimensions d>=2. At low temperatures, both the FL and FL* phases will often be unstable to superconductivity, however, while the FL state forms an ordinary superconductor (SC), the superconducting phase (SC*) of the parent FL* is distinguished by the presence of a Z_2 spin liquid state for the local moments. Because of the relative simplicity of the SC and SC* phases, we propose to study the phase transition between these two phases for signatures of the spin liquid. In particular, we show that the superfluid density is enhanced as we approach this transition from either side. This is in contrast with recent experiments in the vicinity of a magnetic QCP in the iron-pnictides, where a suppression in the superfluid density was observed.


 

Title:   Optical conductivity of visons in Z2 spin liquids close to a VBS transition on the kagome lattice
Authors:   Huh, Yejin; Punk, Matthias; Sachdev, Subir
Publication:   eprint arXiv:1303.7235
Publication Date:   03/2013
Origin:   ARXIV
Keywords:   Condensed Matter - Strongly Correlated Electrons
Bibliographic Code:   2013arXiv1303.7235H

Abstract

We consider Z2 spin liquids on the kagome lattice on the verge of a valence bond solid (VBS) transition, where vortex excitations carrying Z2 magnetic flux - so-called visons - condense. We show that these vison excitations can couple directly to the external electromagnetic field, even though they carry neither spin nor charge. This is possible via a magneto-elastic coupling mechanism recently identified by Potter et al. For the case of transitions to a 36-site unit cell VBS state the corresponding finite ac-conductivity has a specific power law frequency dependence, which is related to the crossover exponent of the quantum critical point. The visons' contribution to the optical conductivity at transitions to VBS states with a 12-site unit cell vanishes, however.


 

Title:   Electricity and Magnetism
Authors:   Purcell, Edward M.; Morin, David J.
Publication:   Electricity and Magnetism, by Edward M. Purcell , David J. Morin, Cambridge, UK: Cambridge University Press, 2013
Publication Date:   03/2013
Origin:   CUP
Bibliographic Code:   2013elma.book.....P

Abstract

1. Electrostatics: charges and fields; 2. The electric potential; 3. Electric fields around conductors; 4. Electric currents; 5. The fields of moving charges; 6. The magnetic field; 7. Electromagnetic induction; 8. Alternating-current circuits; 9. Maxwell's equations and electromagnetic waves; 10. Electric fields in matter; 11. Magnetic fields in matter; Appendixes; References; Index.

 

Title:   Jet energy measurement with the ATLAS detector in proton-proton collisions at sqrt{s}=7 TeV
Authors:   Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Guimaraes da Costa, J.;... Huth, J.;... Morii, M.;...; and 3052 coauthors.
Publication:   The European Physical Journal C, Volume 73, article id. #2304 (EPJC Homepage)
Publication Date:   03/2013
Origin:   SPRINGER
Abstract Copyright:   (c) 2013: CERN for the benefit of the ATLAS collaboration
DOI:   10.1140/epjc/s10052-013-2304-2
Bibliographic Code:   2013EPJC...73.2304A

Abstract

The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of sqrt{s}=7 TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti- k t algorithm with distance parameters R=0.4 or R=0.6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta p T≥20 GeV and pseudorapidities | η|<4.5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2.5 % in the central calorimeter region (| η|<0.8) for jets with 60≤ p T<800 GeV, and is maximally 14 % for p T<30 GeV in the most forward region 3.2≤| η|<4.5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon p T, the sum of the transverse momenta of tracks associated to the jet, or a system of low- p T jets recoiling against a high- p T jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high- p T jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined.

 

Title:   Measurement of the mass difference between top and antitop quarks
Authors:   Aaltonen, T.; Amerio, S.; Amidei, D.;...; Franklin, M.;... Guimaraes da Costa, J.;... and 405 coauthors.
Publication:   Physical Review D, vol. 87, Issue 5, id. 052013 (PhRvD Homepage)
Publication Date:   03/2013
Origin:   ADS
PACS Keywords:   Top quarks, Inclusive production with identified hadrons, Inclusive production with identified leptons, photons, or other nonhadronic particles, Quark and lepton masses and mixing
DOI:   10.1103/PhysRevD.87.052013
Bibliographic Code:   2013PhRvD..87e2013A

Abstract

We present a measurement of the mass difference between top (t) and antitop (t¯) quarks using tt¯ candidate events reconstructed in the final state with one lepton and multiple jets. We use the full data set of Tevatron s=1.96TeV proton-antiproton collisions recorded by the CDF II detector, corresponding to an integrated luminosity of 8.7fb-1. We estimate event by event the mass difference to construct templates for top pair signal events and background events. The resulting mass difference distribution in data compared to signal and background templates using a likelihood fit yields ΔMtop=Mt-M=-1.95±1.11(stat)±0.59(syst)GeV/c2 and is in agreement with the standard model prediction of no mass difference.

 

Title:   Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC
Authors:   Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Guimaraes da Costa, J.;... Huth, J.;... Morii, M.;...; and 3047 coauthors.
Publication:   The European Physical Journal C, Volume 73, article id. #2305 (EPJC Homepage)
Publication Date:   03/2013
Origin:   SPRINGER
Abstract Copyright:   (c) 2013: CERN for the benefit of the ATLAS collaboration
DOI:   10.1140/epjc/s10052-013-2305-1
Bibliographic Code:   2013EPJC...73.2305A

Abstract

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt{s} = 900 {GeV} and 7 TeV collected during 2009 and 2010. Then, using the decay of K s and Λ particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5 % for central isolated hadrons and 1-3 % for the final calorimeter jet energy scale.


 

Title:   Jet energy resolution in proton-proton collisions at sqrt{s}=7{ TeV} recorded in 2010 with the ATLAS detector
Authors:   Aad, G.; Abajyan, T.; Abbott, B.;... Guimaraes da Costa, J.;... Huth, J.;... Morii, M.;...; and 2872 coauthors.
Publication:   The European Physical Journal C, Volume 73, article id. #2306 (EPJC Homepage)
Publication Date:   03/2013
Origin:   SPRINGER
Abstract Copyright:   (c) 2013: CERN for the benefit of the ATLAS collaboration
DOI:   10.1140/epjc/s10052-013-2306-0
Bibliographic Code:   2013EPJC...73.2306A

Abstract

The measurement of the jet energy resolution is presented using data recorded with the ATLAS detector in proton-proton collisions at sqrt{s}=7{ TeV}. The sample corresponds to an integrated luminosity of 35 pb-1. Jets are reconstructed from energy deposits measured by the calorimeters and calibrated using different jet calibration schemes. The jet energy resolution is measured with two different in situ methods which are found to be in agreement within uncertainties. The total uncertainties on these measurements range from 20 % to 10 % for jets within | y|<2.8 and with transverse momenta increasing from 30 GeV to 500 GeV. Overall, the Monte Carlo simulation of the jet energy resolution agrees with the data within 10 %.


 

Title:   Measurement of the tbar{t} production cross section in the tau + jets channel using the ATLAS detector
Authors:   Aad, G.; Abajyan, T.; Abbott, B.;... Franklin, M.;... Guimaraes da Costa, J.;... Huth, J.;... Morii, M.;...; and 2889 coauthors.
Publication:   The European Physical Journal C, Volume 73, article id. #2305 (EPJC Homepage)
Publication Date:   03/2013
Origin:   SPRINGER
Abstract Copyright:   (c) 2013: CERN for the benefit of the ATLAS collaboration
DOI:   10.1140/epjc/s10052-013-2305-1
Bibliographic Code:   2013EPJC...73.2305A

Abstract

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt{s} = 900 {GeV} and 7 TeV collected during 2009 and 2010. Then, using the decay of K s and Λ particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5 % for central isolated hadrons and 1-3 % for the final calorimeter jet energy scale.


 

Title:   Electric-Field Dependence of the Effective Dielectric Constant in Graphene
Authors:   Santos, Elton J. G.; Kaxiras, Efthimios
Publication:   Nano Letters, vol. 13, issue 3, pp. 898-902
Publication Date:   03/2013
Origin:   CROSSREF
DOI:   10.1021/nl303611v
Bibliographic Code:   2013NanoL..13..898S

Abstract

Not Available


 

Title:   The cytoplasm of living cells behaves as a poroelastic material
Authors:   Moeendarbary, Emad; Valon, Léo; Fritzsche, Marco; Harris, Andrew R.; Moulding, Dale A.; Thrasher, Adrian J.; Stride, Eleanor; Mahadevan, L.; Charras, Guillaume T.
Publication:   Nature Materials, Volume 12, Issue 3, pp. 253-261 (2013).
Publication Date:   03/2013
Origin:   NATURE
Abstract Copyright:   (c) 2013: Nature Publishing Group
DOI:   10.1038/nmat3517
Bibliographic Code:   2013NatMa..12..253M

Abstract

The cytoplasm is the largest part of the cell by volume and hence its rheology sets the rate at which cellular shape changes can occur. Recent experimental evidence suggests that cytoplasmic rheology can be described by a poroelastic model, in which the cytoplasm is treated as a biphasic material consisting of a porous elastic solid meshwork (cytoskeleton, organelles, macromolecules) bathed in an interstitial fluid (cytosol). In this picture, the rate of cellular deformation is limited by the rate at which intracellular water can redistribute within the cytoplasm. However, direct supporting evidence for the model is lacking. Here we directly validate the poroelastic model to explain cellular rheology at short timescales using microindentation tests in conjunction with mechanical, chemical and genetic treatments. Our results show that water redistribution through the solid phase of the cytoplasm (cytoskeleton and macromolecular crowders) plays a fundamental role in setting cellular rheology at short timescales.

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