Faculty Publications: June, 2014

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Title:
An X-Ray Line from eXciting Dark Matter
Authors:
Finkbeiner, Douglas P.; Weiner, Neal
Affiliation:
AA(Harvard Univ.), AB(New York University)
Publication:
American Astronomical Society, AAS Meeting #224, #115.08
Publication Date:
06/2014
Origin:
AAS
Abstract Copyright:
(c) 2014: American Astronomical Society
Bibliographic Code:
2014AAS...22411508F

Abstract

The recently reported 3.5 keV line from galaxy clusters and M31 has rekindled interest in dark matter production of lines at X-ray energies. We propose a model in which WIMPs are collisionally excited and de-excite via photon production, thereby converting WIMP kinetic energy into photons. Such a mechanism has different dependencies on density and velocity than sterile neutrino decay, and has more flexibility for explaining the data. I will summarize the current observational status of the 3.5 keV line and the merits of various scenarios to explain it.

 

Title:
A 3D Dust Map from PanSTARRS 1
Authors:
Green, Gregory; Schlafly, Eddie; Finkbeiner, Douglas P.
Affiliation:
AA(Harvard Univ.), AB(MPIA), AC(Harvard Univ.)
Publication:
American Astronomical Society, AAS Meeting #224, #220.05
Publication Date:
06/2014
Origin:
AAS
Abstract Copyright:
(c) 2014: American Astronomical Society
Bibliographic Code:
2014AAS...22422005G

Abstract

We present a 3D map of dust reddening in the Milky Way, using photometry from more than half a billion well observed stars in the PanSTARRS 1 (PS1) 3pi survey. We group stars into pixels, and then infer the line-of-sight reddening vs. distance relation from the individual stellar reddenings and distances. We derive the full probability density of reddening as a function of distance in each ~7'x7' pixel on the sky, incorporating prior knowledge about the distribution of stars throughout the Galaxy and 5-band PS1 photometry. We show that in the large-distance limit, our 3D map has good agreement with the emission-based 2D dust map of Schlegel, Finkbeiner & Davis (1998), despite the very different datasets and methods the two maps rely on. A greater understanding of the 3D distribution of dust in the Galaxy will allow a wealth of detailed science in the Galactic plane, where dust hinders stellar parameter estimation and obscures structure. The method we use can be extended to take advantage of other datasets, such as 2MASS, WISE, SDSS and, eventually, LSST.

 

Title:
Two-component Thermal Dust Emission Model: Application to the Planck HFI Maps
Authors:
Meisner, Aaron M.; Finkbeiner, Douglas P.
Affiliation:
AA(Harvard University), AB(Harvard University)
Publication:
American Astronomical Society, AAS Meeting #224, #220.14
Publication Date:
06/2014
Origin:
AAS
Abstract Copyright:
(c) 2014: American Astronomical Society
Bibliographic Code:
2014AAS...22422014M

Abstract

We present full-sky, 6.1 arcminute resolution maps of dust optical depth and temperature derived by fitting the Finkbeiner et al. (1999) two-component dust emission model to the Planck HFI and IRAS 100 micron maps. This parametrization of the far infrared thermal dust SED as the sum of two modified blackbodies serves as an important alternative to the commonly adopted single modified blackbody dust emission model. We expect our Planck-based maps of dust temperature and optical depth to form the basis for a next-generation, high-resolution extinction map which will additionally incorporate small-scale detail from WISE imaging.

 

Title:
A Low-cost 21 cm Horn-antenna Radio Telescope for Education and Outreach
Authors:
Patel, Nimesh A.; Patel, Rishi N; Kimberk, Robert S; Test, John H; Krolewski, Alex; Ryan, James; Karkare, Kirit S; Kovac, John M; Dame, Thomas M.
Publication:
American Astronomical Society, AAS Meeting #224, #415.01
Publication Date:
06/2014
Origin:
AAS
Abstract Copyright:
(c) 2014: American Astronomical Society
Bibliographic Code:
2014AAS...22441501P

Abstract

Small radio telescopes (1-3m) for observations of the 21 cm hydrogen line are widely used for education and outreach. A pyramidal horn was used by Ewen & Purcell (1951) to first detect the 21cm line at Harvard. Such a horn is simple to design and build, compared to a parabolic antenna which is usually purchased ready-made. Here we present a design of a horn antenna radio telescope that can be built entirely by students, using simple components costing less than $300. The horn has an aperture of 75 cm along the H-plane, 59 cm along the E-plane, and gain of about 20 dB. The receiver system consists of low noise amplifiers, band-pass filters and a software-defined-radio USB receiver that provides digitized samples for spectral processing in a computer. Starting from construction of the horn antenna, and ending with the measurement of the Galactic rotation curve, took about 6 weeks, as part of an undergraduate course at Harvard University. The project can also grow towards building a two-element interferometer for follow-up studies.

 

Title:
Measuring the CMB temperature in the classroom with a low-cost antenna and radiometer
Authors:
Karkare, Kirit S; Bowens-Rubin, Rachel; Connors, Jake; Dame, Thomas M.; Gao, Ryan; Harrison, Samuel; Kimberk, Robert S; Kovac, John M; Law-Smith, Jamie; Robins, Derek; Sansone, Steve; Wilson, Robert W.; Yermakova, Anya; Zeng, Lingzhen
Publication:
American Astronomical Society, AAS Meeting #224, #415.02
Publication Date:
06/2014
Origin:
AAS
Abstract Copyright:
(c) 2014: American Astronomical Society
Bibliographic Code:
2014AAS...22441502K

Abstract

Estimation of the cosmic microwave background (CMB) temperature through a skydip is an ambitious undergraduate laboratory exercise in which care must be taken to understand and account for systematic errors. It is an ideal environment for learning about careful experimental design. We present two versions of a low-cost antenna and radiometer system replicating the CMB discovery measurement (Penzias and Wilson, 1965), operating at 11 and 19 GHz. We describe two small-aperture (8") antenna designs: an HDPE lens-coupled corrugated horn, and a single-groove Potter horn, both of which are simple and inexpensive to fabricate. They have been designed to minimize far sidelobe pickup from the ground in conjunction with a straight-walled or Winston cone. The radiometers are based on low-cost commercial satellite TV receivers, read out with standard laboratory equipment. We describe the design of aperture-filling calibration loads necessary to characterize the radiometer performance. Several iterations of this experiment have been run in the advanced undergraduate astrophysics laboratory course (Ay 191) at Harvard University, with the students building the apparatus starting from scratch and finishing in about 6 weeks. Positive detections of background radiation have been achieved with typical uncertainties of 0.3 K.

 

Title:
Connecting high-field quantum oscillations to the pseudogap in the underdoped cuprates
Authors:
Allais, Andrea; Chowdhury, Debanjan; Sachdev, Subir
Publication:
eprint arXiv:1406.0503
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity
Comment:
Main article: 11 pages, 11 figures. Supplementary material: 3 pages, 5 figures
Bibliographic Code:
2014arXiv1406.0503A

Abstract

We show that a model of underdoped cuprates in which superconductivity competes with density wave order provides a unified description of quantum oscillations at low temperature and high magnetic fields, and photoemission spectra at intermediate temperatures and zero field. We treat quantum oscillations beyond semiclassical approximation and we find clear and robust signatures of the electron pocket proposed by Harrison and Sebastian (arXiv:1103.4181). We also describe the crossover from bidirectional (checkerboard) to unidirectional (stripe-like) density wave order. In the zero field, intermediate temperature regime we compute the photoemission spectrum in the presence of thermally fluctuating density and superconducting orders, and find general agreement with experimental trends.

 

Title:
Sharper Fermi LAT Images: instrument response functions for an improved event selection
Authors:
Portillo, Stephen K. N.; Finkbeiner, Douglas P.
Publication:
eprint arXiv:1406.0507
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Comment:
6 pages, 6 figures
Bibliographic Code:
2014arXiv1406.0507P

Abstract

The Large Area Telescope on the Fermi Gamma-ray Space Telescope has a point spread function with large tails, consisting of events affected by tracker ineffiencies, inactive volumes, and hard scattering; these tails can make source confusion a limiting factor. The parameter CTBCORE, available in the publicly available Extended Fermi LAT data, estimates the quality of each event's direction reconstruction; by implementing a cut in this parameter, the tails of the point spread function can be suppressed at the cost of losing effective area. We implement cuts on CTBCORE and present updated instrument response functions derived from the Fermi LAT data itself, along with all-sky maps generated with these cuts. Having shown the effectiveness of these cuts, especially at low energies, we encourage their use in analyses where angular resolution is more important than Poisson noise.

 

Title:
E + E $\rightarrow$ H
Authors:
Haghighat, Babak; Lockhart, Guglielmo; Vafa, Cumrun
Publication:
eprint arXiv:1406.0850
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Theory
Comment:
38+1 pages, 6 figures
Bibliographic Code:
2014arXiv1406.0850H

Abstract

E-strings arise from M2 branes suspended between an M5 brane and an M9 plane. In this paper we obtain explicit expressions for the elliptic genus of two E-strings using a series of string dualities. Moreover we show how this can be used to recover the elliptic genus of two $E_8\times E_8$ heterotic strings using the Horava-Witten realization of heterotic strings in M-theory. This involves highly non-trivial identities among Jacobi forms, and is remarkable in light of the fact that E-strings are 'sticky' and form bound states whereas heterotic strings do not form bound states.

 

Title:
D-branes and Azumaya/matrix noncommutative differential geometry, I: D-branes as fundamental objects in string theory and differentiable maps from Azumaya/matrix manifolds with a fundamental module to real manifolds
Authors:
Liu, Chien-Hao; Yau, Shing-Tung
Publication:
eprint arXiv:1406.0929
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
Mathematics - Differential Geometry, High Energy Physics - Theory, Mathematics - Algebraic Geometry, Mathematics - Symplectic Geometry, 58A40, 14A22, 81T30, 51K10, 16S50, 46L87
Comment:
100+2 pages, 12 figures
Bibliographic Code:
2014arXiv1406.0929L

Abstract

We consider D-branes in string theory and address the issue of how to describe them mathematically as a fundamental object (as opposed to a solitonic object) of string theory in the realm in differential and symplectic geometry. The notion of continuous maps, $k$-times differentiable maps, and smooth maps from an Azumaya/matrix manifold with a fundamental module to a (commutative) real manifold $Y$ is developed. Such maps are meant to describe D-branes or matrix branes in string theory when these branes are light and soft with only small enough or even zero brane-tension. When $Y$ is a symplectic manifold (resp. a Calabi-Yau manifold; a $7$-manifold with $G_2$-holonomy; a manifold with an almost complex structure $J$), the corresponding notion of Lagrangian maps (resp. special Lagrangian maps; associative maps, coassociative maps; $J$-holomorphic maps) are introduced. Indicative examples linking to symplectic geometry and string theory are given. This provides us with a language and part of the foundation required to study themes, new or old, in symplectic geometry and string theory, including (1) $J$-holomorphic D-curves (with or without boundary), (2) quantization and dynamics of D-branes in string theory, (3) a definition of Fukaya category guided by Lagrangian maps from Azumaya manifolds with a fundamental module with a connection, (4) a theory of fundamental matrix strings or D-strings, and (5) the nature of Ramond-Ramond fields in a space-time. The current note D(11.1) is the symplectic/differential-geometric counterpart of the more algebraic-geometry-oriented first two notes D(1) ([L-Y1]) (arXiv:0709.1515 [math.AG]) and D(2) ([L-L-S-Y], with Si Li and Ruifang Song) (arXiv:0809.2121 [math.AG]) in this project.

 

Title:
Naturalness, b to s gamma, and SUSY Heavy Higgses
Authors:
Katz, Andrey; Reece, Matthew; Sajjad, Aqil
Publication:
eprint arXiv:1406.1172
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Phenomenology
Bibliographic Code:
2014arXiv1406.1172K

Abstract

We explore naturalness constraints on the masses of the heavy Higgs bosons H^0, H^+/-, and A^0 in supersymmetric theories. We show that, in any extension of MSSM which accommodates the 125 GeV Higgs at the tree level, one can derive an upper bound on the SUSY Higgs masses from naturalness considerations. As is well-known for the MSSM, these bounds become weak at large tan beta. However, we show that measurements of b to s gamma together with naturalness arguments lead to an upper bound on tan beta, strengthening the naturalness case for heavy Higgs states near the TeV scale. The precise bound depends somewhat on the SUSY mediation scale: allowing a factor of 10 tuning in the stop sector, the measured rate of b to s gamma implies tan beta < 30 for running down from 10 TeV but tan beta < 4 for mediation at or above 100 TeV, placing m_A near the TeV scale for natural EWSB. Because the signatures of heavy Higgs bosons at colliders are less susceptible to being "hidden" than standard superpartner signatures, there is a strong motivation to make heavy Higgs searches a key part of the LHC's search for naturalness. In an appendix we comment on how the Goldstone boson equivalence theorem links the rates for H to hh and H to ZZ signatures.

 

Title:
Diamagnetism and density wave order in the pseudogap regime of YBa$_2$Cu$_3$O$_{6+x}$
Authors:
Hayward, Lauren E.; Achkar, Andrew J.; Hawthorn, David G.; Melko, Roger G.; Sachdev, Subir
Publication:
eprint arXiv:1406.2694
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Superconductivity
Comment:
9 pages, 6 figures
Bibliographic Code:
2014arXiv1406.2694H

Abstract

Clear experimental evidence of charge density wave correlations competing with superconducting order in YBCO have thrust their relationship with the pseudogap regime into the spotlight. To aid in characterizing the pseudogap regime, we propose a dimensionless ratio of the diamagnetic susceptibility to the correlation length of the charge density wave correlations. Using Monte Carlo simulations, we compute this ratio on the classical model of Hayward et. al. (Science 343, 1336 (2014)), which describes angular fluctuations of a multicomponent order, capturing both superconducting and density wave correlations. We compare our results with available data on YBa$_2$Cu$_3$O$_{6+x}$, and propose experiments to clarify the value of this dimensionless ratio using existing samples and techniques.

 

Title:
Spectral function of a localized fermion coupled to the Wilson-Fisher conformal field theory
Authors:
Allais, Andrea; Sachdev, Subir
Publication:
eprint arXiv:1406.3022
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, High Energy Physics - Theory
Comment:
26 pages, 4 figures
Bibliographic Code:
2014arXiv1406.3022A

Abstract

We describe the dynamics of a single fermion in a dispersionless band coupled to the 2+1 dimensional conformal field theory (CFT) describing the quantum phase transition of a bosonic order parameter with N components. The fermionic spectral functions are expected to apply to the vicinity of quantum critical points in two-dimensional metals over an intermediate temperature regime where the Landau damping of the order parameter can be neglected. Some of our results are obtained by a mapping to an auxiliary problem of a CFT containing a defect line with an external field which locally breaks the global O(N) symmetry.

 

Title:
Semiclassical Virasoro Symmetry of the Quantum Gravity S-Matrix
Authors:
Kapec, Daniel; Lysov, Vyacheslav; Pasterski, Sabrina; Strominger, Andrew
Publication:
eprint arXiv:1406.3312
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Theory, General Relativity and Quantum Cosmology
Comment:
22 pages, 1 figure
Bibliographic Code:
2014arXiv1406.3312K

Abstract

It is shown that the tree-level S-matrix for quantum gravity in four-dimensional Minkowski space has a Virasoro symmetry which acts on the conformal sphere at null infinity.

 

Title:
Nanoscale NMR Spectroscopy and Imaging of Multiple Nuclear Species
Authors:
DeVience, Stephen J.; Pham, Linh M.; Lovchinsky, Igor; Sushkov, Alexander O.; Bar-Gill, Nir; Belthangady, Chinmay; Casola, Francesco; Corbett, Madeleine; Zhang, Huiliang; Lukin, Mikhail; Park, Hongkun; Yacoby, Amir; Walsworth, Ronald L.
Publication:
eprint arXiv:1406.3365
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Chemical Physics
Bibliographic Code:
2014arXiv1406.3365D

Abstract

Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are well-established techniques that provide valuable information in a diverse set of disciplines but are currently limited to macroscopic sample volumes. Here we demonstrate nanoscale NMR spectroscopy and imaging under ambient conditions of samples containing multiple nuclear species, using nitrogen-vacancy (NV) colour centres in diamond as sensors. With single, shallow NV centres in a diamond chip and samples placed on the diamond surface, we perform NMR spectroscopy and one-dimensional MRI on few-nanometre-sized samples containing $^1$H and $^{19}$F nuclei. Alternatively, we employ a high-density NV layer near the surface of a diamond chip to demonstrate wide-field optical NMR spectroscopy of nanoscale samples containing $^1$H, $^{19}$F, and $^{31}$P nuclei, as well as multi-species two-dimensional optical MRI with sub-micron resolution. For all diamond samples exposed to air, we identify a ubiquitous $^1$H NMR signal, consistent with a $\sim 1$ nm layer of adsorbed hydrocarbons or water on the diamond surface and below any sample placed on the diamond. This work lays the foundation for nanoscale NMR and MRI applications such as studies of single proteins and functional biological imaging with subcellular resolution, as well as characterization of thin films with sub-nanometre resolution.

 

Title:
Phonon-Induced Population Dynamics and Intersystem Crossing in Nitrogen-Vacancy Centers
Authors:
Goldman, M. L.; Sipahigil, A.; Yao, N. Y.; Bennett, S. D.; Markham, M.; Twitchen, D. J.; Kubanek, A.; Lukin, M. D.
Publication:
eprint arXiv:1406.4065
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics
Bibliographic Code:
2014arXiv1406.4065G

Abstract

We report direct measurement of population dynamics in the excited state manifold of a nitrogen-vacancy center in diamond. We quantify the phonon-induced mixing rate and demonstrate that mixing can be completely suppressed at low temperatures. Further, we measure the intersystem crossing (ISC) rate for different excited states and develop a theoretical model that unifies the phonon-induced mixing and ISC mechanisms. We find excellent agreement between our model and experiment, and discuss the model's implications for enhancing the NV center's performance as a room-temperature sensor.

 

Title:
Force-Free Electrodynamics around Extreme Kerr Black Holes
Authors:
Lupsasca, Alexandru; Rodriguez, Maria J.; Strominger, Andrew
Publication:
eprint arXiv:1406.4133
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Theory, Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Comment:
24 pages, Related videos available at http://www.youtube.com/playlist?list=PLsrfyTK-g7cP-_8F7A5Zb71K_94_gaXgn
Bibliographic Code:
2014arXiv1406.4133L

Abstract

Plasma-filled magnetospheres can extract energy from a spinning black hole and provide the power source for a variety of observed astrophysical phenomena. These magnetospheres are described by the highly nonlinear equations of force-free electrodynamics, or FFE. Typically these equations can only be solved numerically. In this paper we consider the FFE equations very near the horizon of a maximally spinning black hole, where the energy extraction takes place. Thanks to an enhanced conformal symmetry which appears in this near-horizon region, we are able to analytically obtain several infinite families of exact solutions of the full nonlinear equations.

 

Title:
Indistinguishable photons from separated silicon-vacancy centers in diamond
Authors:
Sipahigil, Alp; Jahnke, Kay D.; Rogers, Lachlan J.; Teraji, T.; Isoya, J.; Zibrov, Alexander S.; Jelezko, Fedor; Lukin, Mikhail D.
Publication:
eprint arXiv:1406.4268
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Materials Science, Physics - Optics
Comment:
6 pages, 6 figures
Bibliographic Code:
2014arXiv1406.4268S

Abstract

We demonstrate that silicon-vacancy (SiV) centers in diamond can be used to efficiently generate coherent optical photons with excellent spectral properties. We show that these features are due to the inversion symmetry associated with SiV centers, and demonstrate generation of indistinguishable single photons from separate emitters in a Hong-Ou-Mandel (HOM) interference experiment.Prospects for realizing efficient quantum network nodes using SiV centers are discussed.

 

Title:
Detecting Majoranas in 1D wires by charge sensing
Authors:
Ben-Shach, Gilad; Haim, Arbel; Appelbaum, Ian; Oreg, Yuval; Yacoby, Amir; Halperin, Bertrand I.
Publication:
eprint arXiv:1406.5172
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics
Bibliographic Code:
2014arXiv1406.5172B

Abstract

The electron number-parity of the ground state of a semiconductor narowire proximity-coupled to a bulk superconductor can alternate between the quantised values $\pm 1$ if parameters such as the wire length $L$, the chemical potential $\mu$ or the magnetic field $B$ are varied inside the topological superconductor phase. % The parity jumps, which may be interpreted as changes in the occupancy of the fermion state formed from the pair of Majorana modes at opposite ends of the wire, are accompanied by jumps $\delta N$ in the charge of the nanowire, whose values decrease exponentially with the wire length. % We study theoretically the dependence of $\delta N$ on system parameters, and compare the locations in the $\mu$-$B$ plane of parity jumps when the nanowire is or is not proximity-coupled to a bulk superconductor. % We show that, despite the fact that the wave functions of the Majorana modes are localised near the two ends of the wire, the charge-density jumps have spatial distributions that are essentially uniform along the wire length, being proportional to the product of the two Majorana wave functions. % We explain how charge measurements, say by an external single-electron transistor, could reveal these effects. % Whereas existing experimental methods require direct contact to the wire for tunneling measurements, charge sensing avoids this issue and provides an orthogonal measurement to confirm recent experimental developments. % Furthermore, by comparing density of states measurements which show Majorana features at the wire ends with the uniformly-distributed charge measurements, one can rule out alternative explanations for earlier results. % We shed light on a new parameter regime for these wire-superconductor hybrid systems, and propose a related experiment to measure spin density.

 

Title:
Renormalization Group Analysis of a Fermionic Hot Spot Model
Authors:
Whitsitt, Seth; Sachdev, Subir
Publication:
eprint arXiv:1406.6061
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Superconductivity, Condensed Matter - Strongly Correlated Electrons
Bibliographic Code:
2014arXiv1406.6061W

Abstract

We present a renormalization group (RG) analysis of a fermionic "hot spot" model of interacting electrons on the square lattice. We truncate the Fermi surface excitations to linearly dispersing quasiparticles in the vicinity of eight hot spots on the Fermi surface, with each hot spot separated from another by the wavevector $(\pi, \pi)$. This motivated by the importance of these Fermi surface locations to the onset of antiferromagnetic order; however, we allow for all possible quartic interactions between the fermions, and also for all possible ordering instabilities. We compute the RG equations for our model, which depend on whether the hot spots are perfectly nested or not, and relate our results to earlier models. We also compute the RG flow of the relevant order parameters for both Hubbard and $J$, $V$ interactions, and present our results for the dominant instabilities in the nested and non-nested cases. In particular, we find that non-nested hot spots with $J$, $V$ interactions have competing singlet $d_{x^2-y^2}$ superconducting and $d$-form factor incommensurate density wave instabilities. We also investigate the enhancement of incommensurate density waves near experimentally observed wavevectors, and find dominant $d$-form factor enhancement for a range of couplings.

 

Title:
The Physics of the B Factories
Authors:
Bevan, A. J.; Golob, B.; Mannel, Th.;... Morii, M.;... ; and 2028 coauthors
Publication:
eprint arXiv:1406.6311
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Experiment, High Energy Physics - Phenomenology
Comment:
928 pages
Bibliographic Code:
2014arXiv1406.6311B

Abstract

This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C.

 

Title:
Observation of muon intensity variations by season with the MINOS Near Detector
Authors:
Adamson, P.; Anghel, I.; Aurisano, A.;... Feldman, G. J.;... ; and 108 coauthors
Publication:
eprint arXiv:1406.7019
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
High Energy Physics - Experiment, Astrophysics - Instrumentation and Methods for Astrophysics, Physics - Instrumentation and Detectors
Comment:
9 pages 10 figures
Bibliographic Code:
2014arXiv1406.7019A

Abstract

A sample of 1.53$\times$10$^{9}$ cosmic-ray-induced single muon events has been recorded at 225 meters-water-equivalent using the MINOS Near Detector. The underground muon rate is observed to be highly correlated with the effective atmospheric temperature. The coefficient $\alpha_{T}$, relating the change in the muon rate to the change in the vertical effective temperature, is determined to be 0.428$\pm$0.003(stat.)$\pm$0.059(syst.). An alternative description is provided by the weighted effective temperature, introduced to account for the differences in the temperature profile and muon flux as a function of zenith angle. Using the latter estimation of temperature, the coefficient is determined to be 0.352$\pm$0.003(stat.)$\pm$0.046(syst.).

 

Title:
Fluid breakup during simultaneous two-phase flow through a three-dimensional porous medium
Authors:
Datta, Sujit S.; Dupin, Jean-Baptiste; Weitz, David A.
Publication:
eprint arXiv:1406.7045
Publication Date:
06/2014
Origin:
ARXIV
Keywords:
Condensed Matter - Soft Condensed Matter, Condensed Matter - Disordered Systems and Neural Networks, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Fluid Dynamics, Physics - Geophysics
Comment:
Physics of Fluids (2014); doi:10.1063/1.4884955
Bibliographic Code:
2014arXiv1406.7045D

Abstract

We use confocal microscopy to directly visualize the simultaneous flow of both a wetting and a non-wetting fluid through a model three-dimensional (3D) porous medium. We find that, for small flow rates, both fluids flow through unchanging, distinct, connected 3D pathways; in stark contrast, at sufficiently large flow rates, the non-wetting fluid is broken up into discrete ganglia. By performing experiments over a range of flow rates, using fluids of different viscosities, and with porous media having different geometries, we show that this transition can be characterized by a state diagram that depends on the capillary numbers of both fluids, suggesting that it is controlled by the competition between the viscous forces exerted on the flowing oil and the capillary forces at the pore scale. Our results thus help elucidate the diverse range of behaviors that arise in two-phase flow through a 3D porous medium.

 

Title:
Search for direct top squark pair production in events with a boson, -jets and missing transverse momentum in TeV collisions with the ATLAS detector
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... ; Franklin, M.;... Guimarães da Costa, J.;... Huth, J.;...; Morii, M.; and 2880 coauthors
Publication:
The European Physical Journal C, Volume 74, article id. #2883 (EPJC Homepage)
Publication Date:
06/2014
Origin:
SPRINGER
Abstract Copyright:
(c) 2014: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-014-2883-6
Bibliographic Code:
2014EPJC...74.2883A

Abstract

A search is presented for direct top squark pair production using events with at least two leptons including a same-flavour opposite-sign pair with invariant mass consistent with the boson mass, jets tagged as originating from -quarks and missing transverse momentum. The analysis is performed with proton-proton collision data at collected with the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of 20.3 fb. No excess beyond the Standard Model expectation is observed. Interpretations of the results are provided in models based on the direct pair production of the heavier top squark state () followed by the decay to the lighter top squark state () via , and for pair production in natural gauge-mediated supersymmetry breaking scenarios where the neutralino () is the next-to-lightest supersymmetric particle and decays producing a boson and a gravitino () via the process.

 

Title:
Search for top quark decays t → qH with H → γγ using the ATLAS detector
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... ; Franklin, M.;... Guimarães da Costa, J.;... Huth, J.;...; Morii, M.; and 2884 coauthors
Publication:
Journal of High Energy Physics, Volume 2014, article id. #8
Publication Date:
06/2014
Origin:
SPRINGER
Keywords:
Hadron-Hadron Scattering
Abstract Copyright:
(c) 2014: The Author(s)
DOI:
10.1007/JHEP06(2014)008
Bibliographic Code:
2014JHEP...06..008A

Abstract

A search is performed for flavour-changing neutral currents in the decay of a top quark to an up-type ( c, u) quark and a Higgs boson, where the Higgs boson decays to two photons. The proton-proton collision data set used corresponds to 4.7 fb-1 at = 7TeV and 20.3fb-1 at = 8TeV collected by the ATLAS experiment at the LHC. Top quark pair events are searched for in which one top quark decays to qH and the other decays to bW. Both the hadronic and the leptonic decay modes of the W boson are used. No significant signal is observed and an upper limit is set on the t → qH branching ratio of 0.79 at the 95% confidence level. The corresponding limit on the tqH coupling combination is 0.17. [Figure not available: see fulltext.]

 

Title:
A new look at Higgs constraints on stops
Authors:
Fan, JiJi; Reece, Matthew
Publication:
Journal of High Energy Physics, Volume 2014, article id. #31
Publication Date:
06/2014
Origin:
SPRINGER
Keywords:
Supersymmetry Phenomenology
Abstract Copyright:
(c) 2014: The Author(s)
DOI:
10.1007/JHEP06(2014)031
Bibliographic Code:
2014JHEP...06..031F

Abstract

We present a simple new way to visualize the constraints of Higgs coupling measurements on light stops in natural SUSY scenarios beyond the MSSM, which works directly in the plane of stop mass eigenvalues (with no need to make assumptions about mixing angles). For given stop mass eigenvalues, the smallest value of X t that can bring the correction to the h → gg and h → γγ couplings into agreement with data is computed. Requiring that this X t is consistent — i.e. that the chosen mass eigenvalues can be the outcome of diagonalizing a matrix with a given off-diagonal term — rules out the possibility that both stops have a mass below ≈ 400 GeV. Requiring that X t is not fine-tuned for agreement with the data shows that neither stop can be lighter than ≈ 100 GeV. These constraints are interesting because, unlike direct searches, they apply no matter how stops decay, and suggest a minimum electroweak fine-tuning of between a factor of 5 and 10. We show that a multi-parameter fit can slightly weaken this conclusion by allowing a large Higgs coupling to b-quarks, but only if a second Higgs boson is within reach of experiment. Certain models, like R-symmetric models with Dirac gauginos, are much more strongly constrained because they predict negligible X t . We illustrate how the constraints will evolve given precise measurements at future colliders (HL-LHC, ILC, and TLEP), and comment on the more difficult case of Folded Supersymmetry.

 

Title:
State-specific detection of trapped HfF+ by photodissociation
Authors:
Ni, Kang-Kuen; Loh, Huanqian; Grau, Matt; Cossel, Kevin C.; Ye, Jun; Cornell, Eric A.
Affiliation:
AA(), AB(), AC(), AD(), AE(), AF()
Publication:
Journal of Molecular Spectroscopy, Volume 300, p. 12-15.
Publication Date:
06/2014
Origin:
ELSEVIER
Abstract Copyright:
(c) 2014 Elsevier Inc.
DOI:
10.1016/j.jms.2014.02.001
Bibliographic Code:
2014JMoSp.300...12N

Abstract

We use (1 + 1‧) resonance-enhanced multiphoton photodissociation (REMPD) to detect the population in individual rovibronic states of trapped HfF+ with a single-shot absolute efficiency of 18%, which is over 200 times better than that obtained with fluorescence detection. The first photon excites a specific rotational level to an intermediate vibronic band at 35 000-36 500 cm-1, and the second photon, at 37 594 cm-1 (266 nm), dissociates HfF+ into Hf+ and F. Mass-resolved time-of-flight ion detection then yields the number of state-selectively dissociated ions. Using this method, we observe rotational-state heating of trapped HfF+ ions from collisions with neutral Ar atoms. Furthermore, we measure the lifetime of the 3Δ1v=0, J=1 state to be 2.1(2) s. This state will be used for a search for a permanent electric dipole moment of the electron.

 

itle:
Graphene/MoS2Hybrid Technology for Large-Scale Two-Dimensional Electronics
Authors:
Yu, Lili; Lee, Yi-Hsien; Ling, Xi; Santos, Elton J. G.; Shin, Yong Cheol; Lin, Yuxuan; Dubey, Madan; Kaxiras, Efthimios; Kong, Jing; Wang, Han; Palacios, Tomás
Publication:
Nano Letters, vol. 14, issue 6, pp. 3055-3063
Publication Date:
06/2014
Origin:
CROSSREF
DOI:
10.1021/nl404795z
Bibliographic Code:
2014NanoL..14.3055Y

Abstract

Not Available

 

Title:
Two steps forward, one step back
Authors:
Lasry, Nathaniel; Guillemette, Jonathan; Mazur, Eric
Publication:
Nature Physics, Volume 10, Issue 6, pp. 402-403 (2014).
Publication Date:
06/2014
Origin:
NATURE
Abstract Copyright:
(c) 2014: Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.
DOI:
10.1038/nphys2988
Bibliographic Code:
2014NatPh..10..402L

Abstract

Among physics students there exists a wide variety of misconceptions, generally thought to be robust and resistant to change. But our analysis of the path of progress has changed our conception of how students learn physics.

 

Title:
Zeeman interaction in ThO H3Δ1 for the electron electric-dipole-moment search
Authors:
Petrov, A. N.; Skripnikov, L. V.; Titov, A. V.; Hutzler, N. R.; Hess, P. W.; O'Leary, B. R.; Spaun, B.; DeMille, D.; Gabrielse, G.; Doyle, J. M.
Publication:
Physical Review A, Volume 89, Issue 6, id.062505 (PhRvA Homepage)
Publication Date:
06/2014
Origin:
APS
PACS Keywords:
Electron correlation calculations for diatomic molecules, Electron electric dipole moment, Electric and magnetic moments polarizability, Electric and magnetic moments polarizability and magnetic susceptibility
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevA.89.062505
Bibliographic Code:
2014PhRvA..89f2505P

Abstract

The current limit on the electron's electric dipole moment, |de|<8.7×10-29 ecm (90% confidence), was set using the molecule thorium monoxide (ThO) in the J =1 rotational level of its H3Δ1 electronic state [J. Baron et al., Science 343, 269 (2014), 10.1126/science.1248213]. This state in ThO is very robust against systematic errors related to magnetic fields or geometric phases, due in part to its Ω-doublet structure. These systematics can be further suppressed by operating the experiment under conditions where the g-factor difference between the Ω doublets is minimized. We consider the g factors of the ThO H3Δ1 state both experimentally and theoretically, including dependence on Ω doublets, the rotational level, and the external electric field. The calculated and measured values are in good agreement. We find that the g-factor difference between Ω doublets is smaller in J =2 than in J =1 and reaches zero at an experimentally accessible electric field. This means that the H ,J=2 state should be even more robust against a number of systematic errors compared to H ,J=1.

 

Title:
Measurement of the ZZ production cross section using the full CDF II data set
Authors:
Aaltonen, T.; Amerio, S.; Amidei, D.;... Franklin, M.;... Guimaraes da Costa, J.;... .; and 403 coauthors
Publication:
Physical Review D, Volume 89, Issue 11, id.112001 (PhRvD Homepage)
Publication Date:
06/2014
Origin:
APS
PACS Keywords:
Other gauge bosons, Z bosons
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevD.89.112001
Bibliographic Code:
2014PhRvD..89k2001A

Abstract

We present a measurement of the ZZ-boson pair-production cross section in 1.96 TeV center-of-mass energy pp¯ collisions. We reconstruct final states incorporating four charged leptons or two charged leptons and two neutrinos from the full data set collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.7 fb-1 of integrated luminosity. Combining the results obtained from each final state, we measure a cross section of 1.04-0.25+0.32 pb, in good agreement with the standard model prediction at next-to-leading order in the strong-interaction coupling.

 

Title:
Evidence for the baryonic decay B¯0→D0ΛΛ¯
Authors:
Lees, J. P.; Poireau, V.; Tisserand, V.;... ... Morii, M.;... and 337 coauthors (Babar Collaboration)
Publication:
Physical Review D, Volume 89, Issue 11, id.112002 (PhRvD Homepage)
Publication Date:
06/2014
Origin:
APS
PACS Keywords:
Decays of bottom mesons, Baryon production, Charmed baryons
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevD.89.112002
Bibliographic Code:
2014PhRvD..89k2002L

Abstract

Evidence is presented for the baryonic B meson decay B¯0→D0ΛΛ¯ based on a data sample of 471×106 BB¯ pairs collected with the BABAR detector at the PEP-II asymmetric e+e- collider located at the SLAC National Accelerator Laboratory. The branching fraction is determined to be B(B¯0→D0ΛΛ¯)=(9.8-2.6+2.9±1.9)×10-6, corresponding to a significance of 3.4 standard deviations including additive systematic uncertainties. A search for the related baryonic B meson decay B¯0→D0Σ0Λ¯ with Σ0→Λγ is performed and an upper limit B(B¯0→D0Σ0Λ¯+B¯0→D0ΛΣ¯0)<3.1×10-5 is determined at 90% confidence level.

 

Title:
Dalitz plot analysis of ηc→K+K-η and ηc→K+K-π0 in two-photon interactions
Authors:
Lees, J. P.; Poireau, V.; Tisserand, V.;... ... Morii, M.;... and 312 coauthors (Babar Collaboration)
Publication:
Physical Review D, Volume 89, Issue 11, id.112004 (PhRvD Homepage)
Publication Date:
06/2014
Origin:
APS
PACS Keywords:
Decays of J/psi Upsilon and other quarkonia
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevD.89.112004
Bibliographic Code:
2014PhRvD..89k2004L

Abstract

We study the processes γγ→K+K-η and γγ→K+K-π0 using a data sample of 519 fb-1 recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e+e- collider at center-of-mass energies at and near the ϒ(nS) (n =2,3,4) resonances. We observe ηc→K+K-π0 and ηc→K+K-η decays, measure their relative branching fraction, and perform a Dalitz plot analysis for each decay. We observe the K0*(1430)→Kη decay and measure its branching fraction relative to the Kπ decay mode to be R(K0*(1430))=B(K/0*(1430)→Kη)B(K0*(1430)→Kπ)=0.092±0.025-0.025+0.010. The ηc →K+K-η and K0*(1430)→Kη results correspond to the first observations of these channels. The data also show evidence for ηc(2S)→K+K-π0 and first evidence for ηc (2S)→K+K-η.

 

Title:
Measurement of B(t→Wb)/B(t→Wq) in Top-Quark-Pair Decays Using Dilepton Events and the Full CDF Run II Data Set
Authors:
Aaltonen, T.; Amerio, S.; Amidei, D.;... Franklin, M.;... Guimaraes da Costa, J.;... .; and 403 coauthors
Publication:
Physical Review Letters, Volume 112, Issue 22, id.221801 (PhRvL Homepage)
Publication Date:
06/2014
Origin:
APS
PACS Keywords:
Determination of Kobayashi-Maskawa matrix elements, Inclusive production with identified leptons photons or other nonhadronic particles, Top quarks
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevLett.112.221801
Bibliographic Code:
2014PhRvL.112v1801A

Abstract

We present a measurement of the ratio of the top-quark branching fractions R=B(t→Wb)/B(t→Wq), where q represents any quark flavor, in events with two charged leptons, imbalance in total transverse energy, and at least two jets. The measurement uses proton-antiproton collision data at center-of-mass energy 1.96 TeV, corresponding to an integrated luminosity of 8.7 fb-1 collected with the Collider Detector at Fermilab during Run II of the Tevatron. We measure R to be 0.87±0.07, and extract the magnitude of the top-bottom quark coupling to be |Vtb|=0.93±0.04, assuming three generations of quarks. Under these assumptions, a lower limit of |Vtb|>0.85(0.87) at 95% (90%) credibility level is set.

 

Title:
Observation of s-Channel Production of Single Top Quarks at the Tevatron
Authors:
Aaltonen, T.; Abazov, V. M.; Abbott, B.;... Franklin, M.;... Guimaraes da Costa, J.;... .; and 763 coauthors; CDF Collaboration
Publication:
Physical Review Letters, Volume 112, Issue 23, id.231803 (PhRvL Homepage)
Publication Date:
06/2014
Origin:
APS
PACS Keywords:
Top quarks, Determination of Kobayashi-Maskawa matrix elements, Applications of electroweak models to specific processes, Inclusive production with identified leptons photons or other nonhadronic particles
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevLett.112.231803
Bibliographic Code:
2014PhRvL.112w1803A

Abstract

We report the first observation of single-top-quark production in the s channel through the combination of the CDF and D0 measurements of the cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb-1 per experiment. The measured cross section is σs=1.29-0.24+0.26 pb. The probability of observing a statistical fluctuation of the background to a cross section of the observed size or larger is 1.8×10-10, corresponding to a significance of 6.3 standard deviations for the presence of an s-channel contribution to the production of single-top quarks.

 

Title:
Evidence for s-Channel Single-Top-Quark Production in Events with One Charged Lepton and Two Jets at CDF
Authors:
Aaltonen, T.; Amerio, S.; Amidei, D.;... Franklin, M.;... Guimaraes da Costa, J.;... .; and 403 coauthors; CDF Collaboration
Publication:
Physical Review Letters, Volume 112, Issue 23, id.231804 (PhRvL Homepage)
Publication Date:
06/2014
Origin:
APS
PACS Keywords:
Top quarks, Applications of electroweak models to specific processes, Inclusive production with identified leptons photons or other nonhadronic particles
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevLett.112.231804
Bibliographic Code:
2014PhRvL.112w1804A

Abstract

We report evidence for s-channel single-top-quark production in proton-antiproton collisions at center-of-mass energy √s =1.96 TeV using a data set that corresponds to an integrated luminosity of 9.4 fb-1 collected by the Collider Detector at Fermilab. We select events consistent with the s-channel process including two jets and one leptonically decaying W boson. The observed significance is 3.8 standard deviations with respect to the background-only prediction. Assuming a top-quark mass of 172.5 GeV /c2, we measure the s-channel cross section to be 1.41-0.42+0.44 pb.

 

Title:
Search for s-Channel Single-Top-Quark Production in Events with Missing Energy Plus Jets in pp ¯ Collisions at √s =1.96 TeV
Authors:
Aaltonen, T.; Amerio, S.; Amidei, D.;... Franklin, M.;... Guimaraes da Costa, J.;... .; and 403 coauthors; CDF Collaboration
Publication:
Physical Review Letters, Volume 112, Issue 23, id.231805 (PhRvL Homepage)
Publication Date:
06/2014
Origin:
APS
PACS Keywords:
Top quarks, Applications of electroweak models to specific processes, Inclusive production with identified hadrons
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevLett.112.231805
Bibliographic Code:
2014PhRvL.112w1805A

Abstract

The first search for single-top-quark production from the exchange of an s-channel virtual W boson using events with an imbalance in the total transverse energy, b-tagged jets, and no identified leptons is presented. Assuming the electroweak production of top quarks of mass 172.5 GeV /c2 in the s channel, a cross section of 1.12-0.57+0.61 (stat+syst) pb with a significance of 1.9 standard deviations is measured. This measurement is combined with the result obtained from events with an imbalance in total transverse momentum, b-tagged jets, and exactly one identified lepton, yielding a cross section of 1.36-0.32+0.37 (stat+syst) pb, with a significance of 4.2 standard deviations.

 

Title:
Measurements of Four-Lepton Production at the Z Resonance in pp Collisions at √s =7 and 8 TeV with ATLAS
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... ; Franklin, M.;... Guimarães da Costa, J.;... Huth, J.;...; Morii, M.; and 2892 coauthors; Atlas Collaboration
Publication:
Physical Review Letters, Volume 112, Issue 23, id.231806 (PhRvL Homepage)
Publication Date:
06/2014
Origin:
APS
PACS Keywords:
Decays of Z bosons
Abstract Copyright:
2014: CERN
DOI:
10.1103/PhysRevLett.112.231806
Bibliographic Code:
2014PhRvL.112w1806A

Abstract

Measurements of four-lepton (4ℓ, ℓ=e,μ) production cross sections at the Z resonance in pp collisions at the LHC with the ATLAS detector are presented. For dilepton and four-lepton invariant mass regions mℓ+->5 GeV and 80<m4ℓ<100 GeV, the measured cross sections are 76±18(stat)±4(syst)±1.4(lumi) fb and 107±9(stat)±4(syst)±3.0(lumi) fb at √s =7 and 8 TeV, respectively. By subtracting the nonresonant 4ℓ production contributions and normalizing with Z→ μ+μ- events, the branching fraction for the Z boson decay to 4ℓ is determined to be (3.20±0.25(stat)±0.13(syst))×10-6, consistent with the standard model prediction.μ--

 

Title:
Detection of B-Mode Polarization at Degree Angular Scales by BICEP2
Authors:
Ade, P. A. R.; Aikin, R. W.; Barkats, D.; Benton, S. J.; Bischoff, C. A.; Bock, J. J.; Brevik, J. A.; Buder, I.; Bullock, E.; Dowell, C. D.; Duband, L.; Filippini, J. P.; Fliescher, S.; Golwala, S. R.; Halpern, M.; Hasselfield, M.; Hildebrandt, S. R.; Hilton, G. C.; Hristov, V. V.; Irwin, K. D.; Karkare, K. S.; Kaufman, J. P.; Keating, B. G.; Kernasovskiy, S. A.; Kovac, J. M.; Kuo, C. L.; Leitch, E. M.; Lueker, M.; Mason, P.; Netterfield, C. B.; Nguyen, H. T.; O'Brient, R.; Ogburn, R. W.; Orlando, A.; Pryke, C.; Reintsema, C. D.; Richter, S.; Schwarz, R.; Sheehy, C. D.; Staniszewski, Z. K.; Sudiwala, R. V.; Teply, G. P.; Tolan, J. E.; Turner, A. D.; Vieregg, A. G.; Wong, C. L.; Yoon, K. W.; Bicep2 Collaboration
Publication:
Physical Review Letters, Volume 112, Issue 24, id.241101 (PhRvL Homepage)
Publication Date:
06/2014
Origin:
APS
PACS Keywords:
Background radiations, Gravitational wave detectors and experiments, Radio microwave, Observational cosmology
Abstract Copyright:
2014: authors
DOI:
10.1103/PhysRevLett.112.241101
Bibliographic Code:
2014PhRvL.112x1101A

Abstract

We report results from the BICEP2 experiment, a cosmic microwave background (CMB) polarimeter specifically designed to search for the signal of inflationary gravitational waves in the B-mode power spectrum around ℓ˜80. The telescope comprised a 26 cm aperture all-cold refracting optical system equipped with a focal plane of 512 antenna coupled transition edge sensor 150 GHz bolometers each with temperature sensitivity of ≈300 μKCMB√s . BICEP2 observed from the South Pole for three seasons from 2010 to 2012. A low-foreground region of sky with an effective area of 380 square deg was observed to a depth of 87 nK deg in Stokes Q and U. In this paper we describe the observations, data reduction, maps, simulations, and results. We find an excess of B-mode power over the base lensed-ΛCDM expectation in the range 30<ℓ<150, inconsistent with the null hypothesis at a significance of >5σ. Through jackknife tests and simulations based on detailed calibration measurements we show that systematic contamination is much smaller than the observed excess. Cross correlating against WMAP 23 GHz maps we find that Galactic synchrotron makes a negligible contribution to the observed signal. We also examine a number of available models of polarized dust emission and find that at their default parameter values they predict power ˜(5-10)× smaller than the observed excess signal (with no significant cross-correlation with our maps). However, these models are not sufficiently constrained by external public data to exclude the possibility of dust emission bright enough to explain the entire excess signal. Cross correlating BICEP2 against 100 GHz maps from the BICEP1 experiment, the excess signal is confirmed with 3σ significance and its spectral index is found to be consistent with that of the CMB, disfavoring dust at 1.7σ. The observed B-mode power spectrum is well fit by a lensed-ΛCDM+tensor theoretical model with tensor-to-scalar ratio r =0.20-0.05+0.07, with r=0 disfavored at 7.0σ. Accounting for the contribution of foreground, dust will shift this value downward by an amount which will be better constrained with upcoming data sets.

 

Title:
Single-Band Model of Resonant Inelastic X-Ray Scattering by Quasiparticles in High-Tc Cuprate Superconductors
Authors:
Benjamin, David; Klich, Israel; Demler, Eugene
Publication:
Physical Review Letters, Volume 112, Issue 24, id.247002 (PhRvL Homepage)
Publication Date:
06/2014
Origin:
APS
PACS Keywords:
X-ray scattering
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevLett.112.247002
Bibliographic Code:
2014PhRvL.112x7002B

Abstract

We show that a simple model of noninteracting quasiparticles accurately describes resonant inelastic x-ray scattering (RIXS) experiments in the hole-doped cuprate superconductors. Band structure alone yields signatures previously attributed to collective magnetic modes, such as the dispersing peaks and nontrivial polarization dependence found in several experiments. We conclude that RIXS data can be explained without positing the existence of magnetic excitations that persist with increasing doping. In so doing we develop a formalism for RIXS in itinerant electron systems that accounts for the positively charged core hole exactly and discover a mechanism by which the core hole produces polarization dependence mimicking that of a magnetic system.

 

Title:
Buffer gas loaded magneto-optical traps for Yb, Tm, Er and Ho
Authors:
Hemmerling, Boerge; Drayna, Garrett K.; Chae, Eunmi; Ravi, Aakash; Doyle, John M.
Publication:
New Journal of Physics, Volume 16, Issue 6, article id. 063070 (2014).
Publication Date:
06/2014
Origin:
IOP
DOI:
10.1088/1367-2630/16/6/063070
Bibliographic Code:
2014NJPh...16f3070H

Abstract

Direct loading of lanthanide atoms into magneto-optical traps (MOTs) from a very slow cryogenic buffer gas beam source is achieved, without the need for laser slowing. The beam source has an average forward velocity of 60–70\;m\;{{s}^{-1}} and a velocity half-width of \sim 35\;m\;{{s}^{-1}}, which allows for direct MOT loading of Yb, Tm, Er and Ho. Residual helium background gas originating from the beam results in a maximum trap lifetime of about 80 ms (with Yb). The addition of a single-frequency slowing laser applied to the Yb in the buffer gas beam increases the number of trapped Yb atoms to 1.3\left( 0.7 \right)\times {{10}^{8}} with a loading rate of 2.0\left( 1.0 \right)\times {{10}^{10}}\;atoms\;{{s}^{-1}}. Decay to metastable states is observed for all trapped species and decay rates are measured. Extension of this approach to the loading of molecules into a MOT is discussed.

 

Title:
Characterization of Patterns Formed by Shadows of Spheres
Authors:
Kostinski, Sarah V.; Chen, Elizabeth R.; Brenner, Michael P.
Publication:
Physical Review Letters, Volume 112, Issue 23, id.235502 (PhRvL Homepage)
Publication Date:
06/2014
Origin:
APS
PACS Keywords:
Nanolithography, Euclidean and projective geometries, Nanoscale pattern formation, Surface cleaning etching patterning
Abstract Copyright:
2014: American Physical Society
DOI:
10.1103/PhysRevLett.112.235502
Bibliographic Code:
2014PhRvL.112w5502K

Abstract

Motivated by colloidal lithography, we study the problem of characterizing periodic planar patterns formed by shadows of spheres. The set of patterns accessible to shadow lithography spanned by lattice types, tilt, and rotation angles is rich, but topological considerations of shadow overlap along simplex edges and faces lead us to just 4+1 distinct categories. These planar patterns are in one-to-one correspondence with a 4-valued index linked to Cayley-Menger determinants. The characterization is confirmed by a phase diagram which predicts surface patterns for any experimental geometry.


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