Faculty Publications: April, 2013

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Title:
The Physics of Cooking
Authors:
Weitz, David
Publication:
American Physical Society, APS April Meeting 2013, April 13-16, 2013, abstract #R7.004
Publication Date:
04/2013
Origin:
APS
Bibliographic Code:
2013APS..APR.R7004W

Abstract

Not Available
 

Title:
Einstein Prize Talk: The Anatomy of a Test of General Relativity
Authors:
Shapiro, Irwin
Publication:
American Physical Society, APS April Meeting 2013, April 13-16, 2013, abstract #T5.001
Publication Date:
04/2013
Origin:
APS
Bibliographic Code:
2013APS..APR.T5001S

Abstract

I will review the conceptual underpinnings of the time-delay test of general relativity (``the Shapiro Effect''), the difficulties in carrying it out, and some recent results of applying the effect in astrophysics.
 

Title:   Regulating the Many to Benefit the Few: Role of Weak Small RNA Targets
Authors:   Jost, Daniel; Nowojewski, Andrzej; Levine, Erel
Publication:   Biophysical Journal, vol. 104, issue 8, pp. 1773-1782
Publication Date:   04/2013
Origin:   CROSSREF
DOI:   10.1016/j.bpj.2013.02.020
Bibliographic Code:   2013BpJ...104.1773J

Abstract

Not Available
 

Title:
American Science and America's Future
Authors:
Randall, Lisa
Publication:
American Physical Society, APS April Meeting 2013, April 13-16, 2013, abstract #T6.003
Publication Date:
04/2013
Origin:
APS
Bibliographic Code:
2013APS..APR.T6003R

Abstract

Not Available
 

Title:
Recent Evidence for Gamma-ray Line Emission from Fermi-LAT: WIMP or Artifact?
Authors:
Su, Meng; Finkbeiner, D. P.
Affiliation:
AA(MIT; Harvard University), AB(Harvard University)
Publication:
American Astronomical Society, HEAD meeting #13, #112.02
Publication Date:
04/2013
Origin:
AAS
Abstract Copyright:
(c) 2013: American Astronomical Society
Bibliographic Code:
2013HEAD...1311202S

Abstract

The recent claims of a gamma-ray line in the Galactic center at 130 GeV have generated excitement, not least because it could be a signal of dark matter annihilation. I will summarize the current state of the observations of the Galactic center, clusters, and unassociated halo objects. I will also speculate about models of particle dark matter that could explain the data, and possible systematic of the Fermi-LAT instrument that might contaminate the line detection.
 

Title:
Fermi Bubbles: Formation Scenarios and Substructure
Authors:
Finkbeiner, Douglas P.
Affiliation:
AA(Harvard Univ.)
Publication:
American Astronomical Society, HEAD meeting #13, #203.01
Publication Date:
04/2013
Origin:
AAS
Abstract Copyright:
(c) 2013: American Astronomical Society
Bibliographic Code:
2013HEAD...1320301F

Abstract

The Milky Way has gamma-ray lobes extending several kpc above and below the Galactic center, known as the "Fermi Bubbles." Although the Galactic center is quiet today, these bubbles are a hint of past AGN activity, a burst of star formation, or some other dramatic energy injection. In the three years since their discovery, they have been modeled analytically and numerically, and additional radio and x-ray data have been obtained, leading to a number of ideas about their origins. I will review the latest data and report on some possible formation scenarios. I will also give an update on our tentative claim last year of a linear jet-like structure within the bubbles (arXiv:1205.5852).
 

Title:   Elasto-hydrodynamic adhesion
Authors:   Reyssat, Etienne; Mandre, Shreyas; Cizaire, Tanguy; Mahadevan, Lakshminarayanan
Publication:   EGU General Assembly 2013, held 7-12 April, 2013 in Vienna, Austria, id. EGU2013-3274
Publication Date:   04/2013
Origin:   COPERNICUS
Bibliographic Code:   2013EGUGA..15.3274R

Abstract

We are interested in the hydrodynamically mediated adhesion of a flexible membrane against a flat rigid substrate. A very primitive adhesion mechanism is encountered when trying to disjoin two parallel flat surfaces separated by a fluid layer. Drainage of the neighbouring fluid into the opening gap induces viscous resistance to traction. In the case of two stiff surfaces, this force was calculated more than a century ago by Stefan and Reynolds. We will present experimental and numerical results showing how elastic deformations of one of the membranes can greatly enhance this hydrodynamic adhesion.
 

Title:   The spectrum of strings on warped AdS3 × S3
Authors:   Azeyanagi, Tatsuo; Hofman, Diego M.; Song, Wei; Strominger, Andrew
Publication:   Journal of High Energy Physics, Volume 2013, article id. #78
Publication Date:   04/2013
Origin:   SPRINGER
Keywords:   Black Holes in String Theory, AdS-CFT Correspondence, Space-Time Symmetries
Abstract Copyright:   (c) 2013: SISSA, Trieste, Italy
DOI:   10.1007/JHEP04(2013)078
Bibliographic Code:   2013JHEP...04..078A

Abstract

String theory on NS-NS AdS3 × S3 admits an exactly marginal deformation which breaks the {{overline{{SL( {2,{R}} )}}}_R} × SL(2, {R} ) L isometry of AdS3 down to {{overline{{SL( {2,{R}} )}}}_R} × U(1) L . The holographic dual is an exotic and only partially understood type of two-dimensional CFT with a reduced unbroken global conformal symmetry group. In this paper we study the deformed theory on the string worldsheet. It is found to be related by a spectral flow which is nonlocal in spacetime to the undeformed worldsheet theory. An exact formula for the spectrum of massive strings is presented.
 

Title:   Quark and gluon jet substructure
Authors:   Gallicchio, Jason; Schwartz, Matthew D.
Publication:   Journal of High Energy Physics, Volume 2013, article id. #90
Publication Date:   04/2013
Origin:   SPRINGER
Keywords:   QCD Phenomenology, Jets
Abstract Copyright:   (c) 2013: SISSA, Trieste, Italy
DOI:   10.1007/JHEP04(2013)090
Bibliographic Code:   2013JHEP...04..090G

Abstract

Distinguishing quark-initiated jets from gluon-initiated jets has the potential to significantly improve the reach of many beyond-the-standard model searches at the Large Hadron Collider and to provide additional tests of QCD. To explore whether quark and gluon jets could possibly be distinguished on an event-by-event basis, we perform a comprehensive simulation-based study. We explore a variety of motivated and unmotivated variables with a semi-automated multivariate approach. General conclusions are that at 50% quark jet acceptance efficiency, around 80%-90% of gluon jets can be rejected. Some benefit is gained by combining variables. Different event generators are compared, as are the effects of using only charged tracks to avoid pileup. Additional information, including interactive distributions of most variables and their cut efficiencies, can be found at http://jets.physics.harvard.edu/qvg.
 

Title:   Solid-state electronic spin coherence time approaching one second
Authors:   Bar-Gill, N.; Pham, L. M.; Jarmola, A.; Budker, D.; Walsworth, R. L.
Publication:   Nature Communications, Volume 4, id. 1743 (2013).
Publication Date:   04/2013
Origin:   NATURE
Abstract Copyright:   (c) 2013: Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.
DOI:   10.1038/ncomms2771
Bibliographic Code:   2013NatCo...4E1743B

Abstract

Solid-state spin systems such as nitrogen-vacancy colour centres in diamond are promising for applications of quantum information, sensing and metrology. However, a key challenge for such solid-state systems is to realize a spin coherence time that is much longer than the time for quantum spin manipulation protocols. Here we demonstrate an improvement of more than two orders of magnitude in the spin coherence time (T2) of nitrogen-vacancy centres compared with previous measurements: T2≈0.6 s at 77 K. We employed dynamical decoupling pulse sequences to suppress nitrogen-vacancy spin decoherence, and found that T2 is limited to approximately half of the longitudinal spin relaxation time over a wide range of temperatures, which we attribute to phonon-induced decoherence. Our results apply to ensembles of nitrogen-vacancy spins, and thus could advance quantum sensing, enable squeezing and many-body entanglement, and open a path to simulating driven, interaction-dominated quantum many-body Hamiltonians.
 

Title:   Cooling through optimal control of quantum evolution
Authors:   Rahmani, Armin; Kitagawa, Takuya; Demler, Eugene; Chamon, Claudio
Publication:   Physical Review A, vol. 87, Issue 4, id. 043607 (PhRvA Homepage)
Publication Date:   04/2013
Origin:   APS
PACS Keywords:   Dynamic properties of condensates; collective and hydrodynamic excitations, superfluid flow, Atom cooling methods, Atoms in optical lattices, Fermions in reduced dimensions
DOI:   10.1103/PhysRevA.87.043607
Bibliographic Code:   2013PhRvA..87d3607R

Abstract

Nonadiabatic unitary evolution with tailored time-dependent Hamiltonians can prepare systems of cold-atomic gases with various desired properties such as low excess energies. For a system of two one-dimensional quasicondensates coupled with a time-varying tunneling amplitude, we show that the optimal protocol, for maximizing any figure of merit in a given time, is bang-bang, i.e., the coupling alternates between only two values through a sequence of sudden quenches. Minimizing the energy of one of the quasicondensates with such a nonadiabatic protocol, and then decoupling it at the end of the process, can result in effective cooling beyond the current state of the art. Our cooling method can be potentially applied to arbitrary systems through an integration of the experiment with simulated annealing computations.
 

Title:   Dispersing quasinormal modes in (2+1)-dimensional conformal field theories
Authors:   Witczak-Krempa, William; Sachdev, Subir
Publication:   Physical Review B, vol. 87, Issue 15, id. 155149 (PhRvB Homepage)
Publication Date:   04/2013
Origin:   APS
PACS Keywords:   Conformal field theory, algebraic structures
DOI:   10.1103/PhysRevB.87.155149
Bibliographic Code:   2013PhRvB..87o5149W

Abstract

We study the charge response of conformal field theories (CFTs) at nonzero temperature in 2+1 dimensions using the anti-de Sitter (AdS)/CFT correspondence. A central role is played by the quasinormal modes (QNMs), specifically, the poles and zeros of the current correlators. We generalize our recent study of the QNMs of the ac charge conductivity to include momentum dependence. This sheds light on the various excitations in the CFT. We begin by discussing the R-current correlators of the N=8 SU(Nc) super-Yang-Mills theory at its conformal fixed point using holography. For instance, transitions in the QNM spectrum as a function of momentum clearly identify “hydrodynamic-to-relativistic” crossovers. We then extend our study to include four-derivative terms in the gravitational description allowing us to study more generic charge response as well as the role of the S duality, which plays a central role in understanding the correlators. The presence of special purely damped QNMs can lead to new behavior, distinct from what occurs in the aforementioned gauge theory. We also extend previous conductivity sum rules to finite momentum and discuss their interpretation in the gravity picture. A comparison is finally made with the conformal fixed point of the vector O(N) model in the large-N limit.
 

Title:   The Pan-STARRS 1 Photometric Reference Ladder, Release 12.01
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:   The Astrophysical Journal Supplement, Volume 205, Issue 2, article id. 20, 13 pp. (2013). (ApJS Homepage)
Publication Date:   04/2013
Origin:   IOP
Astronomy Keywords:   catalogs, instrumentation: photometers, standards, surveys: PS1, techniques: photometric
DOI:   10.1088/0067-0049/205/2/20
Bibliographic Code:   2013ApJS..205...20M

Abstract

As of 2012 January 21, the Pan-STARRS 1 3π Survey has observed the 3/4 of the sky visible from Hawaii with a minimum of 2 and mean of 7.6 observations in five 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 data set. 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 right ascension and at four intervals in declination. We will release updates with increased area coverage (more rungs) from the latest data set until the PS1 survey and the final re-reduction are completed. The currently released catalog presents photometry of ~1000 objects per square degree in the rungs of the ladder. Saturation occurs at g P1, r P1, i P1 ~ 13.5; z P1 ~ 13.0; and y P1 ~ 12.0. Photometry is provided for stars down to g P1, r P1, i P1 ~ 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) mmag 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:   Colloidal Particles: Crystals, Glasses, and Gels
Authors:   Lu, Peter J.; Weitz, David A.
Publication:   Annual Review of Condensed Matter Physics, vol. 4, p.217-233
Publication Date:   04/2013
Origin:   ANNREV
DOI:   10.1146/annurev-conmatphys-030212-184213
Bibliographic Code:   2013ARCMP...4..217L

Abstract

Colloidal particles are microscopic solid particles suspended in a fluid. Colloids are small enough that thermal energy drives their dynamics and ensures equilibration with the suspending fluid; they are also large enough that their positions and motions can be measured precisely using optical methods, such as light scattering and laser-scanning confocal fluorescence microscopy. Colloidal suspensions are a powerful model system for the study of other phenomena in condensed matter physics, where the collective phase behavior of the solid particles mimics that of other condensed systems. We review three classes of interacting colloidal particles, crystals, glasses, and gels, each of which represents fascinating properties of colloidal particles as well as a model for more general types of materials and their behavior.
 

Title:   Nanometer scale quantum thermometry in a living cell
Authors:   Kucsko, G.; Maurer, P. C.; Yao, N. Y.; Kubo, M.; Noh, H. J.; Lo, P. K.; Park, H.; Lukin, M. D.
Publication:   eprint arXiv:1304.1068
Publication Date:   04/2013
Origin:   ARXIV
Keywords:   Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Optics
Bibliographic Code:   2013arXiv1304.1068K

Abstract

Sensitive probing of temperature variations on nanometer scales represents an outstanding challenge in many areas of modern science and technology. In particular, a thermometer capable of sub-degree temperature resolution as well as integration within a living system could provide a powerful new tool for many areas of biological research, including temperature-induced control of gene expression and cell-selective treatment of disease. Here, we demonstrate a new approach to nanoscale thermometry that utilizes coherent manipulation of the electronic spin associated with nitrogen-vacancy (NV) color centers in diamond. We show the ability to detect temperature variations down to 1.8 mK (sensitivity of 9 mK/sqrt(Hz)) in an ultra-pure bulk diamond sample. Using NV centers in diamond nanocrystals (nanodiamonds), we directly measure the local thermal environment at length scales down to 200 nm. Finally, by introducing both nanodiamonds and gold nanoparticles into a single human embryonic fibroblast, we demonstrate temperature-gradient control and mapping at the sub-cellular level, enabling unique potential applications in life sciences.
 

Title:   A Low Temperature Expansion for Matrix Quantum Mechanics
Authors:   Lin, Ying-Hsuan; Shao, Shu-Heng; Wang, Yifan; Yin, Xi
Publication:   eprint arXiv:1304.1593
Publication Date:   04/2013
Origin:   ARXIV
Keywords:   High Energy Physics - Theory
Comment:   72 pages, 5 figures
Bibliographic Code:   2013arXiv1304.1593L

Abstract

We analyze solutions to loop-truncated Schwinger-Dyson equations in massless N=2 and N=4 Wess-Zumino matrix quantum mechanics at finite temperature, where conventional perturbation theory breaks down due to IR divergences. We find a rather intricate low temperature expansion that involves fractional power scaling in the temperature, based on a consistent "soft collinear" approximation. We conjecture that at least in the N=4 matrix quantum mechanics, such scaling behavior holds to all perturbative orders in the 1/N expansion. We discuss some preliminary results in analyzing the gauged supersymmetric quantum mechanics using Schwinger-Dyson equations, and comment on the connection to metastable microstates of black holes in the holographic dual of BFSS matrix quantum mechanics.
 

Title:   Jet Sampling: Improving Event Reconstruction through Multiple Interpretations
Authors:   Kahawala, Dilani; Krohn, David; Schwartz, Matthew D.
Publication:   eprint arXiv:1304.2394
Publication Date:   04/2013
Origin:   ARXIV
Keywords:   High Energy Physics - Phenomenology
Bibliographic Code:   2013arXiv1304.2394K

Abstract

The classification of events involving jets as signal-like or background-like can depend strongly on the jet algorithm used and its parameters. This is partly due to the fact that standard jet algorithms yield a single partition of the particles in an event into jets, even if no particular choice stands out from the others. As an alternative, we propose that one should consider multiple interpretations of each event, generalizing the Qjets procedure to event-level analysis. With multiple interpretations, an event is no longer restricted to either satisfy cuts or not satisfy them - it can be assigned a weight between 0 and 1 based on how well it satisfies the cuts. These cut-weights can then be used to improve the discrimination power of an analysis or reduce the uncertainty on mass or cross-section measurements. For example, using this approach on a Higgs plus Z boson sample, with h->bb we find an 28% improvement in significance can be realized at the 8 TeV LHC. Through a number of other examples, we show various ways in which having multiple interpretations can be useful on the event level.
 

Title:   Decoupling of High Dimension Operators from the Low Energy Sector in Holographic Models
Authors:   Fitzpatrick, A. Liam; Kaplan, Jared; Katz, Emanuel; Randall, Lisa
Publication:   eprint arXiv:1304.3458
Publication Date:   04/2013
Origin:   ARXIV
Keywords:   High Energy Physics - Theory, High Energy Physics - Phenomenology
Comment:   21+9 pages, 1 figure
Bibliographic Code:   2013arXiv1304.3458F

Abstract

We study the decoupling of high dimension operators from the the description of the low-energy spectrum in theories where conformal symmetry is broken by a single scale, which we refer to as `broken CFTs'. Holographic duality suggests that this decoupling occurs in generic backgrounds. We show how the decoupling of high mass states in the (d+1)-dimensional bulk relates to the decoupling of high energy states in the d-dimensional broken CFT. In other words, we explain why both high dimension operators and high mass states in the CFT decouple from the low-energy physics of the mesons and glueballs. In many cases, the decoupling can occur exponentially fast in the dimension of the operator. Holography motivates a new kind of form factor proportional to the two point function between broken CFT operators with very different scaling dimensions. This new notion of decoupling can provide a systematic justification for holographic descriptions of QCD and condensed matter systems with only light degrees of freedom in the bulk.
 

Title:   Exclusion of exotic top-like quarks with -4/3 electric charge using jet-charge tagging in single-lepton ttbar events at CDF
Authors:   CDF Collaboration;Aaltonen, T.; Amerio, S.; Amidei, D.;...; Franklin, M.;... Guimaraes da Costa, J.;... and 408 coauthors.
Publication:   eprint arXiv:1304.4141
Publication Date:   04/2013
Origin:   ARXIV
Keywords:   High Energy Physics - Experiment
Comment:   submitted to Phys. Rev. D
Bibliographic Code:   2013arXiv1304.4141C

Abstract

We report on a measurement of the top-quark electric charge in ttbar events in which one W boson originating from the top-quark pair decays into leptons and the other into hadrons. The event sample was collected by the CDF II detector in sqrt(s)=1.96 TeV proton-antiproton collisions and corresponds to 5.6 fb^(-1). We find the data to be consistent with the standard model and exclude the existence of an exotic quark with -4/3 electric charge and mass of the conventional top quark at the 99% confidence level.
 

Title:   Unconventional magnetism via optical pumping of interacting spin systems
Authors:   Lee, Tony E.; Gopalakrishnan, Sarang; Lukin, Mikhail D.
Publication:   eprint arXiv:1304.4959
Publication Date:   04/2013
Origin:   ARXIV
Keywords:   Condensed Matter - Quantum Gases, Nonlinear Sciences - Pattern Formation and Solitons, Quantum Physics
Comment:   5 pages + appendix
Bibliographic Code:   2013arXiv1304.4959L

Abstract

We consider strongly interacting systems of effective spins, subject to dissipative spin-flip processes associated with optical pumping. We predict the existence of novel magnetic phases in the steady-state of this system, which emerge due to the competition between coherent and dissipative processes. Specifically, for strongly anisotropic spin-spin interactions, we find ferromagnetic, antiferromagnetic, spin-density-wave, and staggered-XY steady states, which are separated by nonequilibrium phase transitions meeting at a Lifshitz point. These transitions are accompanied by quantum correlations, resulting in spin squeezing. Experimental implementations in ultracold atoms and trapped ions are discussed.
 

Title:   Dicke Quantum Spin and Photon Glass in Optical Cavities: Non-equilibrium theory and experimental signatures
Authors:   Buchhold, Michael; Strack, Philipp; Sachdev, Subir; Diehl, Sebastian
Publication:   eprint arXiv:1304.5196
Publication Date:   04/2013
Origin:   ARXIV
Keywords:   Condensed Matter - Quantum Gases, Condensed Matter - Disordered Systems and Neural Networks, Quantum Physics
Comment:   25 pages, 12 figures
Bibliographic Code:   2013arXiv1304.5196B

Abstract

In the context of ultracold atoms in multimode optical cavities, the appearance of a quantum-critical glass phase of atomic spins has been predicted recently. Due to the long-range nature of the cavity-mediated interactions, but also the presence of a driving laser and dissipative processes such as cavity photon loss, the quantum optical realization of glassy physics has no analog in condensed matter, and could evolve into a "cavity glass microscope" for frustrated quantum systems out-of-equilibrium. Here we develop the non-equilibrium theory of the multimode Dicke model with quenched disorder and Markovian dissipation. Using a unified Keldysh path integral approach, we show that the defining features of a low temperature glass, representing a critical phase of matter with algebraically decaying temporal correlation functions, are seen to be robust against the presence of dissipation due to cavity loss. The universality class however is modified due to the Markovian bath. The presence of strong disorder leads to an enhanced equilibration of atomic and photonic degrees of freedom, including the emergence of a common low-frequency effective temperature. The imprint of the atomic spin glass physics onto a "photon glass" makes it possible to detect the glass state by standard experimental techniques of quantum optics. We provide an unambiguous characterization of the superradiant and glassy phases in terms of fluorescence spectroscopy, homodyne detection, and the temporal photon correlation function $g^{(2)}(\tau)$.
 

Title:   Topological Strings, D-Model, and Knot Contact Homology
Authors:   Aganagic, Mina; Ekholm, Tobias; Ng, Lenhard; Vafa, Cumrun
Publication:   eprint arXiv:1304.5778
Publication Date:   04/2013
Origin:   ARXIV
Keywords:   High Energy Physics - Theory, Mathematics - Algebraic Geometry, Mathematics - Geometric Topology, Mathematics - Symplectic Geometry
Comment:   154 pages, 25 figures
Bibliographic Code:   2013arXiv1304.5778A

Abstract

We study the connection between topological strings and contact homology recently proposed in the context of knot invariants. In particular, we establish the proposed relation between the Gromov-Witten disk amplitudes of a Lagrangian associated to a knot and augmentations of its contact homology algebra. This also implies the equality between the Q-deformed A-polynomial and the augmentation polynomial of knot contact homology (in the irreducible case). We also generalize this relation to the case of links and to higher rank representations for knots. The generalization involves a study of the quantum moduli space of special Lagrangian branes with higher Betti numbers probing the Calabi-Yau. This leads to an extension of SYZ, and a new notion of mirror symmetry, involving higher dimensional mirrors. The mirror theory is a topological string, related to D-modules, which we call the "D-model." In the present setting, the mirror manifold is the augmentation variety of the link. Connecting further to contact geometry, we study intersection properties of branches of the augmentation variety guided by the relation to D-modules. This study leads us to propose concrete geometric constructions of Lagrangian fillings for links. We also relate the augmentation variety with the large N limit of the colored HOMFLY, which we conjecture to be related to a Q-deformation of the extension of A-polynomials associated with the link complement.
 

Title:   Nutrient Shielding in Clusters of Cells
Authors:   Lavrentovich, Maxim O.; Koschwanez, John H.; Nelson, David R.
Publication:   eprint arXiv:1304.6256
Publication Date:   04/2013
Origin:   ARXIV
Keywords:   Physics - Biological Physics, Condensed Matter - Soft Condensed Matter, Quantitative Biology - Cell Behavior
Comment:   19 pages, 15 figures, submitted to Physical Review E
Bibliographic Code:   2013arXiv1304.6256L

Abstract

Cellular nutrient consumption is influenced by both the nutrient uptake kinetics of an individual cell and the cells' spatial arrangement. Large cell clusters or colonies have inhibited growth at the cluster's center due to the shielding of nutrients by the cells closer to the surface. We develop an effective medium theory that predicts a thickness $\ell$ of the outer shell of cells in the cluster that receives enough nutrient to grow. The cells are treated as partially absorbing identical spherical nutrient sinks, and we identify a dimensionless parameter $\nu$ that characterizes the absorption strength of each cell. The parameter $\nu$ can vary over many orders of magnitude between different cell types, ranging from bacteria and yeast to human tissue. The thickness $\ell$ decreases with increasing $\nu$, increasing cell volume fraction $\phi$, and decreasing ambient nutrient concentration $\psi_{\infty}$. The theoretical results are compared with numerical simulations and experiments. In the latter studies, colonies of budding yeast, \textit{Saccharomyces cerevisiae}, are grown on glucose media and imaged under a confocal microscope. We measure the growth inside the colonies via a fluorescent protein reporter and compare the experimental and theoretical results for the thickness $\ell$.
 

Title:   Measurement of Neutrino and Antineutrino Oscillations Using Beam and Atmospheric Data in MINOS
Authors:   MINOS Collaboration; Adamson, P.; Anghel, I.; Backhouse, C.;...; Feldman, G. J.; ... and 106 coauthors.
Publication:   eprint arXiv:1304.6335
Publication Date:   04/2013
Origin:   ARXIV
Keywords:   High Energy Physics - Experiment
Comment:   5 pages, 3 figures
Bibliographic Code:   2013arXiv1304.6335M

Abstract

We report measurements of oscillation parameters from $\nu_{mu}$ and $\bar{\nu}_{\mu}$ disappearance using beam and atmospheric data from MINOS. The data comprise exposures of \unit[$10.71 \times 10^{20}$]{protons on target (POT)} in the $\nu_{\mu}$-dominated beam, $\unit[3.36\times10^{20}]{POT}}$ in the $\bar{\nu}_{\mu}$-enhanced beam, and 37.88 kton-years of atmospheric neutrinos. Assuming identical $\nu$ and $\bar{\nu}$ oscillation parameters, we measure \mbox{$|\Delta m^2}| = \unit[2.41^{+0.09}_{-0.10}) \times 10^{-3}]{eV^{2}}$} and $\sin^{2}/!/left(2\theta \right) = 0.950^{+0.035}_{-0.036}$. Allowing independent $\nu$ and $\bar{\nu}$ oscillations, we measure antineutrino parameters of $|\Delta \bar{m}^2| = \unit[(2.50 ^{+0.23}_{-0.25}) \times 10^{-3}]{eV^{2}}$ and $\sin^{2}/!/left(2\bar{\theta} \right) = 0.97^{+0.03}_{-0.08}$, with minimal change to the neutrino parameters.
 

Title:   Noise-resistant optimal spin squeezing via quantum control
Authors:   Caneva, T.; Montangero, S.; Lukin, M. D.; Calarco, T.
Publication:   eprint arXiv:1304.7195
Publication Date:   04/2013
Origin:   ARXIV
Keywords:   Quantum Physics, Condensed Matter - Other Condensed Matter
Comment:   4 pages of main text + 3 pages of supplementary material
Bibliographic Code:   2013arXiv1304.7195C

Abstract

Entangled atomic states, such as spin squeezed states, represent a promising resource for a new generation of quantum sensors and atomic clocks. We demonstrate that optimal control techniques can be used to substantially enhance the degree of spin squeezing in strongly interacting many-body systems, even in the presence of noise and imperfections. Specifically, we present a time-optimal protocol that yields more than two orders of magnitude improvement with respect to conventional adiabatic preparation. Potential experimental implementations are discussed.
 

Title:   Imaging Universal Conductance Fluctuations in Graphene
Authors:   Borunda, Mario F.; Berezovsky, Jesse; Westervelt, Robert M.; Heller, Eric J.
Publication:   eprint arXiv:1304.7242
Publication Date:   04/2013
Origin:   ARXIV
Keywords:   Condensed Matter - Mesoscale and Nanoscale Physics
Comment:   15 Pages, 3 Figures. Related papers at this http <a href="http://physics.okstate.edu/borunda/index.html" >URL</a>; ACS Nano, 2011, 5 (5), pp 3622-3627; doi:10.1021/nn103450d.
Bibliographic Code:   2013arXiv1304.7242B

Abstract

We study conductance fluctuations (CF) and the sensitivity of the conductance to the motion of a single scatterer in two-dimensional massless Dirac systems. Our extensive numerical study finds limits to the predicted universal value of CF. We find that CF are suppressed for ballistic systems near the Dirac point and approach the universal value at sufficiently strong disorder. The conductance of massless Dirac fermions is sensitive to the motion of a single scatterer. CF of order $e^2/h$ result from the motion of a single impurity by a distance comparable to the Fermi wavelength. This result applies to graphene systems with a broad range of impurity strength and concentration while the dependence on the Fermi wavelength can be explored {\em via} gate voltages. Our prediction can be tested by comparing graphene samples with varying amounts of disorder and can be used to understand interference effects in mesoscopic graphene devices.
 

Title:   Search for dark matter candidates and large extra dimensions in events with a jet and missing transverse momentum with the ATLAS detector
Authors:   Aad, G.; Abajyan, T.; Abbott, B.;... Franklin, M.;... Guimaraes da Costa, J.;... Huth, J.;... Morii, M.;...; and 2896 coauthors.
Publication:   Journal of High Energy Physics, Volume 2013, article id. #75
Publication Date:   04/2013
Origin:   SPRINGER
Keywords:   Hadron-Hadron Scattering
Abstract Copyright:   (c) 2013: CERN, for the benefit of the ATLAS collaboration
DOI:   10.1007/JHEP04(2013)075
Bibliographic Code:   2013JHEP...04..075A

Abstract

A search for new phenomena in events with a high-energy jet and large missing transverse momentum is performed using data from proton-proton collisions at √{s}=7 TeV with the ATLAS experiment at the Large Hadron Collider. Four kinematic regions are explored using a dataset corresponding to an integrated luminosity of 4.7 fb-1. No excess of events beyond expectations from Standard Model processes is observed, and limits are set on large extra dimensions and the pair production of dark matter particles.
 

Title:   Nanoscale magnetic imaging of a single electron spin under ambient conditions
Authors:   Grinolds, M. S.; Hong, S.; Maletinsky, P.; Luan, L.; Lukin, M. D.; Walsworth, R. L.; Yacoby, A.
Publication:   Nature Physics, Volume 9, Issue 4, pp. 215-219 (2013).
Publication Date:   04/2013
Origin:   NATURE
Abstract Copyright:   (c) 2013: Nature Publishing Group
DOI:   10.1038/nphys2543
Bibliographic Code:   2013NatPh...9..215G

Abstract

The detection of ensembles of spins under ambient conditions has revolutionized the biological, chemical and physical sciences through magnetic resonance imaging and nuclear magnetic resonance. Pushing sensing capabilities to the individual-spin level would enable unprecedented applications such as single-molecule structural imaging; however, the weak magnetic fields from single spins are undetectable by conventional far-field resonance techniques. In recent years, there has been a considerable effort to develop nanoscale scanning magnetometers, which are able to measure fewer spins by bringing the sensor in close proximity to its target. The most sensitive of these magnetometers generally require low temperatures for operation, but the ability to measure under ambient conditions (standard temperature and pressure) is critical for many imaging applications, particularly in biological systems. Here we demonstrate detection and nanoscale imaging of the magnetic field from an initialized single electron spin under ambient conditions using a scanning nitrogen-vacancy magnetometer. Real-space, quantitative magnetic-field images are obtained by deterministically scanning our nitrogen-vacancy magnetometer 50nm above a target electron spin, while measuring the local magnetic field using dynamically decoupled magnetometry protocols. We discuss how this single-spin detection enables the study of a variety of room-temperature phenomena in condensed-matter physics with an unprecedented combination of spatial resolution and spin sensitivity.
 

Title:   Vacuum instabilities with a wrong-sign Higgs–gluon–gluon amplitude
Authors:   Reece, Matthew
Affiliation:   AA(Department of Physics, Harvard University, Cambridge, MA 02138, USA)
Publication:   New Journal of Physics, Volume 15, Issue 4, article id. 043003 (2013).
Publication Date:   04/2013
Origin:   IOP
DOI:   10.1088/1367-2630/15/4/043003
Bibliographic Code:   2013NJPh...15d3003R

Abstract

The recently discovered 125 GeV boson appears very similar to a Standard Model (SM) Higgs, but with data favoring an enhanced h → γγ rate. A number of groups have found that fits would allow (or, less so after the latest updates, prefer) that the ht\bar {t} coupling have the opposite sign. This can be given meaning in the context of an electroweak chiral Lagrangian, but it might also be interpreted to mean that a new colored and charged particle runs in loops and reinforces the W-loop contribution to hFF, while also producing the opposite-sign hGG amplitude to that generated by integrating out the top. Due to a correlation in sign of the new physics amplitudes, when the SM hFF coupling is enhanced the hGG coupling is decreased. Thus, in order to not suppress the rate of h → WW and h → ZZ, which appear to be approximately SM-like, one would need the loop to ‘overshoot’, not only canceling the top contribution but producing an opposite-sign hGG vertex of about the same magnitude as that in the SM. We argue that most such explanations have severe problems with fine-tuning and, more importantly, vacuum stability. In particular, the case of stop loops producing an opposite-sign hGG vertex of the same size as the SM one is ruled out by a combination of vacuum decay bounds and Large Electron–Positron Collider (LEP) constraints. We also show that scenarios with a sign flip from loops of color octet charged scalars or new fermionic states are highly constrained.
 

Title:   Search for extra dimensions in diphoton events from proton–proton collisions at \sqrt {s} = 7\,  TeV in the ATLAS detector at the LHC
Authors:   Aad, G.; Abajyan, T.; Abbott, B.;... Guimaraes da Costa, J.;... Huth, J.;... Morii, M.;...; and 2899 coauthors.
Publication:   New Journal of Physics, Volume 15, Issue 4, article id. 043007 (2013).
Publication Date:   04/2013
Origin:   IOP
DOI:   10.1088/1367-2630/15/4/043007
Bibliographic Code:   2013NJPh...15d3007A

Abstract

The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, is addressed in certain models through the postulate of extra spatial dimensions. A search for evidence of extra spatial dimensions in the diphoton channel has been performed using the full set of proton–proton collisions at \sqrt {s} = 7\,{ { TeV}} recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. This dataset corresponds to an integrated luminosity of 4.9 fb‑1. The diphoton invariant mass spectrum is observed to be in good agreement with the Standard Model expectation. In the context of the model proposed by Arkani–Hamed, Dimopoulos and Dvali, 95% confidence level lower limits of between 2.52 and 3.92 TeV are set on the ultraviolet cutoff scale MS depending on the number of extra dimensions and the theoretical formalism used. In the context of the Randall–Sundrum model, a lower limit of 2.06 (1.00) TeV at 95% confidence level is set on the mass of the lightest graviton for couplings of {k/\overline {M}_{ { Pl}}} = 0.1 (0.01) . Combining with the ATLAS dilepton searches based on the 2011 data, the 95% confidence level lower limit on the Randall–Sundrum graviton mass is further tightened to 2.23 (1.03) TeV for {k/\overline {M}_{ { Pl}}} = 0.1 (0.01).
 

Title:   Search for WH production with a light Higgs boson decaying to prompt electron-jets in proton–proton collisions 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 2909 coauthors.
Publication:   New Journal of Physics, Volume 15, Issue 4, article id. 043009 (2013).
Publication Date:   04/2013
Origin:   IOP
DOI:   10.1088/1367-2630/15/4/043009
Bibliographic Code:   2013NJPh...15d3009A

Abstract

A search is performed for WH production with a light Higgs boson decaying to hidden-sector particles resulting in clusters of collimated electrons, known as electron-jets. The search is performed with 2.04 fb-1 of data collected in 2011 with the ATLAS detector at the Large Hadron Collider in proton–proton collisions at \sqrt {s}=7\,{ { TeV}} . One event satisfying the signal selection criteria is observed, which is consistent with the expected background rate. Limits on the product of the WH production cross section and the branching ratio of a Higgs boson decaying to prompt electron-jets are calculated as a function of a Higgs boson mass in the range from 100 to 140 GeV.
 

Title:   A pendulum in a flowing soap film
Authors:   Bandi, M. M.; Concha, A.; Wood, R.; Mahadevan, L.
Publication:   Physics of Fluids, Volume 25, Issue 4, pp. 041702-041702-6 (2013). (PhFl Homepage)
Publication Date:   04/2013
Origin:   AIP
Keywords:   film flow, flow instability, flow visualisation, fluid oscillations, pendulums, vortices
PACS Keywords:   Spreading films, Flow instabilities, Flow visualization and imaging, Vortex dynamics; rotating fluids
Abstract Copyright:   (c) 2013: American Institute of Physics
DOI:   10.1063/1.4800057
Bibliographic Code:   2013PhFl...25d1702B

Abstract

We consider the dynamics of a pendulum made of a rigid ring attached to an elastic filament immersed in a flowing soap film. The system shows an oscillatory instability whose onset is a function of the flow speed, length of the supporting string, the ring mass, and ring radius. We characterize this system and show that there are different regimes where the frequency is dependent or independent of the pendulum length depending on the relative magnitude of the added-mass. Although the system is an infinite-dimensional, we can explain many of our results in terms of a one degree-of-freedom system corresponding to a forced pendulum. Indeed, using the vorticity measured via particle imaging velocimetry allows us to make the model quantitative, and a comparison with our experimental results shows we can capture the basic phenomenology of this system.
 

Title:   Search for displaced muonic lepton jets from light Higgs boson decay in proton-proton collisions at s=7 TeV with the ATLAS detector
Authors:   Aad, G.; Abajyan, T.; Abbott, B.;... Guimaraes da Costa, J.;... Huth, J.;... Morii, M.;...; and 2904 coauthors.
Publication:   Physics Letters B, Volume 721, Issue 1-3, p. 32-50.
Publication Date:   04/2013
Origin:   ELSEVIER
Abstract Copyright:   CERN
DOI:   10.1016/j.physletb.2013.02.058
Bibliographic Code:   2013PhLB..721...32A

Abstract

A search is performed for collimated muon pairs displaced from the primary vertex produced in the decay of long-lived neutral particles in proton-proton collisions at s=7 TeV centre-of-mass energy, with the ATLAS detector at the LHC. In a 1.9 fbevent sample collected during 2011, the observed data are consistent with the Standard Model background expectations. Limits on the product of the production cross section and the branching ratio of a Higgs boson decaying to hidden-sector neutral long-lived particles are derived as a function of the particles' mean lifetime.
 

Title:   Search for single b*-quark production with the ATLAS detector at s=7 TeV
Authors:   Aad, G.; Abajyan, T.; Abbott, B.;... Franklin, M.;... Guimaraes da Costa, J.;... Huth, J.;... Morii, M.;...; and 2898 coauthors.
Publication:   Physics Letters B, Volume 721, Issue 4, p. 171-189.
Publication Date:   04/2013
Origin:   ELSEVIER
Abstract Copyright:   CERN
DOI:   10.1016/j.physletb.2013.03.016
Bibliographic Code:   2013PhLB..721..171A

Abstract

The results of a search for an excited bottom-quark b* in pp collisions at s=7 TeV, using 4.7  fb of data collected by the ATLAS detector at the LHC are presented. In the model studied, a single b*-quark is produced through a chromomagnetic interaction and subsequently decays to a W boson and a top quark. The search is performed in the dilepton and lepton + jets final states, which are combined to set limits on b*-quark couplings for a range of b*-quark masses. For a benchmark with unit size chromomagnetic and Standard Model-like electroweak b* couplings, b* quarks with masses less than 870 GeV are excluded at the 95% credibility level.
 

Title:   Search for Bs0→μ+μ- and B0→μ+μ- decays with the full CDF Run II data set
Authors:   Aaltonen, T.; Amerio, S.; Amidei, D.;... Franklin, M.;... Guimaraes da Costa, J.;...; and 406 coauthors.
Publication:   Physical Review D, vol. 87, Issue 7, id. 072003 (PhRvD Homepage)
Publication Date:   04/2013
Origin:   APS
PACS Keywords:   Decays of bottom mesons, Neutral currents, Supersymmetric models, Leptonic, semileptonic, and radiative decays
DOI:   10.1103/PhysRevD.87.072003
Bibliographic Code:   2013PhRvD..87g2003A

Abstract

We report on a search for Bs0→μ+μ- and B0→μ+μ- decays using proton-antiproton collision data at s=1.96TeV corresponding to 10fb-1 of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron collider. The observed number of B0 candidates is consistent with background-only expectations and yields an upper limit on the branching fraction of B(B0→μ+μ-)<4.6×10-9 at 95% confidence level. We observe an excess of Bs0 candidates. The probability that the background processes alone could produce such an excess or larger is 0.94%. The probability that the combination of background and the expected standard model rate of Bs0→μ+μ- could produce such an excess or larger is 6.8%. These data are used to determine a branching fraction B(Bs0→μ+μ-)=(1.3-0.7+0.9)×10-8 and provide an upper limit of B(Bs0→μ+μ-)<3.1×10-8 at 95% confidence level.
 

Title:   Theory of interacting dislocations on cylinders
Authors:   Amir, Ariel; Paulose, Jayson; Nelson, David R.
Publication:   Physical Review E, vol. 87, Issue 4, id. 042314 (PhRvE Homepage)
Publication Date:   04/2013
Origin:   APS
PACS Keywords:   Suspensions, dispersions, pastes, slurries, colloids, Linear defects: dislocations, disclinations, Stochastic analysis methods, Interaction between different crystal defects; gettering effect
DOI:   10.1103/PhysRevE.87.042314
Bibliographic Code:   2013PhRvE..87d2314A

Abstract

We study the mechanics and statistical physics of dislocations interacting on cylinders, motivated by the elongation of rod-shaped bacterial cell walls and cylindrical assemblies of colloidal particles subject to external stresses. The interaction energy and forces between dislocations are solved analytically, and analyzed asymptotically. The results of continuum elastic theory agree well with numerical simulations on finite lattices even for relatively small systems. Isolated dislocations on a cylinder act like grain boundaries. With colloidal crystals in mind, we show that saddle points are created by a Peach-Koehler force on the dislocations in the circumferential direction, causing dislocation pairs to unbind. The thermal nucleation rate of dislocation unbinding is calculated, for an arbitrary mobility tensor and external stress, including the case of a twist-induced Peach-Koehler force along the cylinder axis. Surprisingly rich phenomena arise for dislocations on cylinders, despite their vanishing Gaussian curvature.
 

Title:   Resolving an Individual One-Proton Spin Flip to Determine a Proton Spin State
Authors:   DiSciacca, J.; Marshall, M.; Marable, K.; Gabrielse, G.
Publication:   Physical Review Letters, vol. 110, Issue 14, id. 140406 (PhRvL Homepage)
Publication Date:   04/2013
Origin:   APS
PACS Keywords:   Electric and magnetic moments, Protons and neutrons, Ion trapping
DOI:   10.1103/PhysRevLett.110.140406
Bibliographic Code:   2013PhRvL.110n0406D

Abstract

Previous measurements with a single trapped proton (p) or antiproton (p¯) 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 rapidly detected instead. The 96% fidelity and an efficiency expected to approach unity suggests that it may be possible to use quantum jump spectroscopy to measure the p and p¯ magnetic moments much more precisely.
 

Title:   Charge Noise Spectroscopy Using Coherent Exchange Oscillations in a Singlet-Triplet Qubit
Authors:   Dial, O. E.; Shulman, M. D.; Harvey, S. P.; Bluhm, H.; Umansky, V.; Yacoby, A.
Publication:   Physical Review Letters, vol. 110, Issue 14, id. 146804 (PhRvL Homepage)
Publication Date:   04/2013
Origin:   APS
PACS Keywords:   Quantum well devices, Quantum information, Electrometers, Spin echoes
DOI:   10.1103/PhysRevLett.110.146804
Bibliographic Code:   2013PhRvL.110n6804D

Abstract

Two level systems that can be reliably controlled and measured hold promise as qubits both for metrology and for quantum information science. Since a fluctuating environment limits the performance of qubits in both capacities, understanding environmental coupling and dynamics is key to improving qubit performance. We show measurements of the level splitting and dephasing due to the voltage noise of a GaAs singlet-triplet qubit during exchange oscillations. Unexpectedly, the voltage fluctuations are non-Markovian even at high frequencies and exhibit a strong temperature dependence. This finding has impacts beyond singlet-triplet qubits since nearly all solid state qubits suffer from some kind of charge noise. The magnitude of the fluctuations allows the qubit to be used as a charge sensor with a sensitivity of 2×10-8e/Hz, 2 orders of magnitude better than a quantum-limited rf single electron transistor. Based on these measurements, we provide recommendations for improving qubit coherence, allowing for higher fidelity operations and improved charge sensitivity.
 

Title:   Tetrahedral Colloidal Clusters from Random Parking of Bidisperse Spheres
Authors:   Schade, Nicholas B.; Holmes-Cerfon, Miranda C.; Chen, Elizabeth R.; Aronzon, Dina; Collins, Jesse W.; Fan, Jonathan A.; Capasso, Federico; Manoharan, Vinothan N.
Publication:   Physical Review Letters, vol. 110, Issue 14, id. 148303 (PhRvL Homepage)
Publication Date:   04/2013
Origin:   APS
PACS Keywords:   Colloids, Self-organized systems, Self-assembly, DNA
DOI:   10.1103/PhysRevLett.110.148303
Bibliographic Code:   2013PhRvL.110n8303S

Abstract

Using experiments and simulations, we investigate the clusters that form when colloidal spheres stick irreversibly to—or “park” on—smaller spheres. We use either oppositely charged particles or particles labeled with complementary DNA sequences, and we vary the ratio α of large to small sphere radii. Once bound, the large spheres cannot rearrange, and thus the clusters do not form dense or symmetric packings. Nevertheless, this stochastic aggregation process yields a remarkably narrow distribution of clusters with nearly 90% tetrahedra at α=2.45. The high yield of tetrahedra, which reaches 100% in simulations at α=2.41, arises not simply because of packing constraints, but also because of the existence of a long-time lower bound that we call the “minimum parking” number. We derive this lower bound from solutions to the classic mathematical problem of spherical covering, and we show that there is a critical size ratio αc=(1+2)≈2.41, close to the observed point of maximum yield, where the lower bound equals the upper bound set by packing constraints. The emergence of a critical value in a random aggregation process offers a robust method to assemble uniform clusters for a variety of applications, including metamaterials.
 

Title:   Phonon-Induced Spin-Spin Interactions in Diamond Nanostructures: Application to Spin Squeezing
Authors:   Bennett, S. D.; Yao, N. Y.; Otterbach, J.; Zoller, P.; Rabl, P.; Lukin, M. D.
Publication:   Physical Review Letters, vol. 110, Issue 15, id. 156402 (PhRvL Homepage)
Publication Date:   04/2013
Origin:   APS
PACS Keywords:   Impurity and defect levels, Micromechanical devices and systems, Nonclassical states of the electromagnetic field, including entangled photon states; quantum state engineering and measurements
DOI:   10.1103/PhysRevLett.110.156402
Bibliographic Code:   2013PhRvL.110o6402B

Abstract

We propose and analyze a novel mechanism for long-range spin-spin interactions in diamond nanostructures. The interactions between electronic spins, associated with nitrogen-vacancy centers in diamond, are mediated by their coupling via strain to the vibrational mode of a diamond mechanical nanoresonator. This coupling results in phonon-mediated effective spin-spin interactions that can be used to generate squeezed states of a spin ensemble. We show that spin dephasing and relaxation can be largely suppressed, allowing for substantial spin squeezing under realistic experimental conditions. Our approach has implications for spin-ensemble magnetometry, as well as phonon-mediated quantum information processing with spin qubits.
 

Title:   Dressed-State Resonant Coupling between Bright and Dark Spins in Diamond
Authors:   Belthangady, C.; Bar-Gill, N.; Pham, L. M.; Arai, K.; Le Sage, D.; Cappellaro, P.; Walsworth, R. L.
Publication:   Physical Review Letters, vol. 110, Issue 15, id. 157601 (PhRvL Homepage)
Publication Date:   04/2013
Origin:   APS
PACS Keywords:   Color centers and other defects, Magnetometers for magnetic field measurements, Spin polarized transport
DOI:   10.1103/PhysRevLett.110.157601
Bibliographic Code:   2013PhRvL.110o7601B

Abstract

Under ambient conditions, spin impurities in solid-state systems are found in thermally mixed states and are optically “dark”; i.e., the spin states cannot be optically controlled. Nitrogen-vacancy (NV) centers in diamond are an exception in that the electronic spin states are “bright”; i.e., they can be polarized by optical pumping, coherently manipulated with spin-resonance techniques, and read out optically, all at room temperature. Here we demonstrate a scheme to resonantly couple bright NV electronic spins to dark substitutional-nitrogen (P1) electronic spins by dressing their spin states with oscillating magnetic fields. This resonant coupling mechanism can be used to transfer spin polarization from NV spins to nearby dark spins and could be used to cool a mesoscopic bath of dark spins to near-zero temperature, thus providing a resource for quantum information and sensing, and aiding studies of quantum effects in many-body spin systems.
 

Title:   Interferometric Approach to Measuring Band Topology in 2D Optical Lattices
Authors:   Abanin, Dmitry A.; Kitagawa, Takuya; Bloch, Immanuel; Demler, Eugene
Publication:   Physical Review Letters, vol. 110, Issue 16, id. 165304 (PhRvL Homepage)
Publication Date:   04/2013
Origin:   APS
PACS Keywords:   Ultracold gases, trapped gases, Semiclassical theories and applications, Phases: geometric; dynamic or topological
DOI:   10.1103/PhysRevLett.110.165304
Bibliographic Code:   2013PhRvL.110p5304A

Abstract

Recently, optical lattices with nonzero Berry’s phases of Bloch bands have been realized. New approaches for measuring Berry’s phases and topological properties of bands with experimental tools appropriate for ultracold atoms need to be developed. In this Letter, we propose an interferometric method for measuring Berry’s phases of two-dimensional Bloch bands. The key idea is to use a combination of Ramsey interference and Bloch oscillations to measure Zak phases, i.e., Berry’s phases for closed trajectories corresponding to reciprocal lattice vectors. We demonstrate that this technique can be used to measure the Berry curvature of Bloch bands, the π Berry’s phase of Dirac points, and the first Chern number of topological bands. We discuss several experimentally feasible realizations of this technique, which make it robust against low-frequency magnetic noise.
 

Title:   Electron Neutrino and Antineutrino Appearance in the Full MINOS Data Sample
Authors:   Adamson, P.; Anghel, I.; Backhouse, C.;... Feldman, G. J.;...; and 106 authors.
Publication:   Physical Review Letters, vol. 110, Issue 17, id. 171801 (PhRvL Homepage)
Publication Date:   04/2013
Origin:   APS
PACS Keywords:   Neutrino mass and mixing, Ordinary neutrinos (nuW bosons, Beams in particle accelerators
DOI:   10.1103/PhysRevLett.110.171801
Bibliographic Code:   2013PhRvL.110q1801A

Abstract

We report on νe and ν¯e appearance in νμ and ν¯μ beams using the full MINOS data sample. The comparison of these νe and ν¯e appearance data at a 735 km baseline with θ13 measurements by reactor experiments probes δ, the θ23 octant degeneracy, and the mass hierarchy. This analysis is the first use of this technique and includes the first accelerator long-baseline search for ν¯μ→ν¯e. Our data disfavor 31% (5%) of the three-parameter space defined by δ, the octant of the θ23, and the mass hierarchy at the 68% (90%) C.L. We measure a value of 2sin⁡2(2θ13)sin⁡223) that is consistent with reactor experiments.
 

Title:   Spin-Orbit Suppression of Cold Inelastic Collisions of Aluminum and Helium
Authors:   Connolly, Colin Bryant; Au, Yat Shan; Chae, Eunmi; Tscherbul, Timur V.; Buchachenko, Alexei A.; Lu, Hsin-I.; Ketterle, Wolfgang; Doyle, John M.
Publication:   Physical Review Letters, vol. 110, Issue 17, id. 173202 (PhRvL Homepage)
Publication Date:   04/2013
Origin:   APS
PACS Keywords:   Scattering of atoms and molecules, Interatomic potentials and forces, Atom cooling methods
DOI:   10.1103/PhysRevLett.110.173202
Bibliographic Code:   2013PhRvL.110q3202C

Abstract

We present a quantitative study of suppression of cold inelastic collisions by the spin-orbit interaction. We prepare cold ensembles of >1011 Al(P1/22) atoms via cryogenic buffer-gas cooling and use a single-beam optical pumping method to measure their magnetic (mJ-changing) and fine-structure (J-changing) collisions with He3 atoms at millikelvin temperatures over a range of magnetic fields from 0.5 to 6 T. The experimentally determined rates are in good agreement with the functional form predicted by quantum scattering calculations using ab initio potentials. This comparison provides direct experimental evidence for a proposed model of suppressed inelasticity in collisions of atoms in P1/22 states [T. V. Tscherbul et al., Phys. Rev. A 80, 040701(R) (2009)PLRAAN1050-2947], which may allow for sympathetic cooling of other P1/22 atoms (e.g., In, Tl and metastable halogens).
 

Title:   Technical results from the surface run of the LUX dark matter experiment
Authors:   Akerib, D. S.; Bai, X.; Bernard, E.;...; Morii, M.;...; and 106 authors.
Publication:   Astroparticle Physics, Volume 45, p. 34-43. (APh Homepage)
Publication Date:   05/2013
Origin:   ELSEVIER
Abstract Copyright:   Elsevier B.V.
DOI:   10.1016/j.astropartphys.2013.02.001
Bibliographic Code:   2013APh....45...34A

Abstract

We present the results of the three-month above-ground commissioning run of the Large Underground Xenon (LUX) experiment at the Sanford Underground Research Facility located in Lead, South Dakota, USA. LUX is a 370 kg liquid xenon detector that will search for cold dark matter in the form of Weakly Interacting Massive Particles (WIMPs). The commissioning run, conducted with the detector immersed in a water tank, validated the integration of the various sub-systems in preparation for the underground deployment. Using the data collected, we report excellent light collection properties, achieving 8.4 photoelectrons per keV for 662 keV electron recoils without an applied electric field, measured in the center of the WIMP target. We also find good energy and position resolution in relatively high-energy interactions from a variety of internal and external sources. Finally, we have used the commissioning data to tune the optical properties of our simulation and report updated sensitivity projections for spin-independent WIMP-nucleon scattering.


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