Faculty
Publications Added in April, 2013
Query Results from the Smithsonian/NASA
Astrophysics Data System (ADS)
The
following are Harvard Physics faculty members' publications,
added to the ADS database last month. Please note that
some publications which appeared in print last month
may not be included in the database (and therefore
may not appear on this list) until the following month.
| 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.
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.
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.
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.
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
$\ell$.
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.
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.
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 B
s0→μ
+μ
- and
B
0→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 B
0 candidates is consistent
with background-only expectations and yields an upper
limit on the branching fraction of B(B
0→μ
+μ
-)<4.6×10
-9 at
95% confidence level. We observe an excess of B
s0 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 B
s0→μ
+μ
- could
produce such an excess or larger is 6.8%. These data
are used to determine a branching fraction B(B
s0→μ
+μ
-)=(1.3
-0.7+0.9)×10
-8 and
provide an upper limit of B(B
s0→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.
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.
Abstract
We report on ν
e and ν¯
e appearance
in ν
μ and ν¯
μ beams using the full
MINOS data sample. The comparison of these ν
e and
ν¯
e appearance data at a 735 km baseline with
θ
13 measurements by reactor experiments probes
δ, the θ
23 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 θ
23, and the mass hierarchy
at the 68% (90%) C.L. We measure a value of 2sin
2(2θ
13)sin
2(θ
23)
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).
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.
| see
also: |
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| Jan., 2008 |
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| Jan., 2009 |
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Apr., 2009 |
May, 2009 |
June, 2009 |
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June, 2010 |
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Dec., 2011 |
| Jan., 2012 |
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June, 2012 |
| July, 2012 |
Aug., 2012 |
Sep., 2012 |
Oct., 2012 |
Nov., 2012 |
Dec., 2012 |
| Jan., 2013 |
Feb., 2013 |
Mar., 2013 |
|
|
|
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