Faculty
Publications added in September, 2008
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 apeared in print last month may
not be included in the database (and therefore may not
appear on this list) until the following month.
| Title: |
|
ATLAS Muon Drift
Tube Electronics |
| Authors: |
|
Arai, Y.; Ball, B.; Beretta, M.; Boterenbrood, H.; Brandenburg, G. W.; Ceradini, F.; Chapman, J. W.; Dai, T.; Ferretti, C.; Fries, T.; Gregory, J.; Guimarães da Costa, J.; Harder, S.; Hazen, E.; Huth, J.;
... and 14 coauthors. |
| Publication: |
|
Journal of Instrumentation,
Volume 09, Issue 09, pp. 09001 (2008). |
| Publication
Date: |
|
09/2008 |
| Origin: |
|
IOP |
| DOI: |
|
10.1088/1748-0221/3/09/P09001 |
| Bibliographic
Code: |
|
2008JInst..09.9001A |
Abstract
This paper describes the electronics used for the ATLAS
monitored drift tube (MDT) chambers. These chambers are
the main component of the precision tracking system in
the ATLAS muon spectrometer. The MDT detector system
consists of 1,150 chambers containing a total of 354,000
drift tubes. It is capable of measuring the sagitta of
muon tracks to an accuracy of 60 μm, which corresponds
to a momentum accuracy of about 10% at pT= 1 TeV. The
design and performance of the MDT readout electronics
as well as the electronics for controlling, monitoring
and powering the detector will be discussed. These electronics
have been extensively tested under simulated running
conditions and have undergone radiation testing certifying
them for more than 10 years of LHC operation. They are
now installed on the ATLAS detector and are operating
during cosmic ray commissioning runs.
Abstract
For slow-roll inflation we study the phase transition
to the eternal regime. Starting from a finite inflationary
volume, we consider the volume of the universe at reheating
as order parameter. We show that there exists a critical
value for the classical inflaton speed, dot phi2/H4 =
3/(2π2), where the probability distribution for the reheating
volume undergoes a sharp transition. In particular, for
sub-critical inflaton speeds all distribution moments
become infinite. We show that at the same transition
point the system develops a non-vanishing probability
of having a strictly infinite reheating volume, while
retaining a finite probability for finite values. Our
analysis represents the exact quantum treatment of the
system at lowest order in the slow-roll parameters and
H2/MPl2.
| Title: |
|
Linking optical and
infrared observations with gravitational wave
sources through transient variability |
| Authors: |
|
Stubbs, C. W. |
| Publication: |
|
Classical and Quantum
Gravity, Volume 25, Issue 18, pp. 184033 (2008). |
| Publication
Date: |
|
09/2008 |
| Origin: |
|
IOP |
| DOI: |
|
10.1088/0264-9381/25/18/184033 |
| Bibliographic
Code: |
|
2008CQGra..25r4033S |
Abstract
Optical and infrared observations have thus far detected
more celestial cataclysms than have been seen in gravity
waves (GW). This argues that we should search for gravity
wave signatures that correspond to transient variables
seen at optical wavelengths, at precisely known positions.
There is an unknown time delay between the optical and
gravitational transient, but knowing the source location
precisely specifies the corresponding time delays across
the gravitational antenna network as a function of the
GW-to-optical arrival time difference. Optical searches
should detect virtually all supernovae that are plausible
gravitational radiation sources. The transient optical
signature expected from merging compact objects is not
as well understood, but there are good reasons to expect
detectable transient optical/IR emission from most of
these sources as well. The next generation of deep wide-field
surveys (for example PanSTARRS and LSST) will be sensitive
to subtle optical variability, but we need to fill the
'blind spots' that exist in the galactic plane, and for
optically bright transient sources. In particular, a
galactic plane variability survey at λ~ 2 µm seems worthwhile.
Science would benefit from closer coordination between
the various optical survey projects and the gravity wave
community.
| Title: |
|
The Kerr/CFT Correspondence |
| Authors: |
|
Guica, Monica; Hartman, Thomas; Song, Wei; Strominger, Andrew |
| Publication: |
|
eprint arXiv:0809.4266 |
| Publication
Date: |
|
09/2008 |
| Origin: |
|
ARXIV |
| Keywords: |
|
High Energy Physics
- Theory |
| Comment: |
|
21 pages, no figures |
| Bibliographic
Code: |
|
2008arXiv0809.4266G |
Abstract
Quantum gravity in the region very near the horizon of
an extreme Kerr black hole (whose angular momentum and
mass are related by J=GM^2) is considered. It is shown
that consistent boundary conditions exist, for which
the asymptotic symmetry generators form one copy of the
Virasoro algebra with central charge c_L=12J / \hbar.
This implies that the near-horizon quantum states can
be identified with those of (a chiral half of) a two-dimensional
conformal field theory (CFT). Moreover, in the extreme
limit, the Frolov-Thorne vacuum state reduces to a thermal
density matrix with dimensionless temperature T_L=1/2\pi
and conjugate energy given by the zero mode generator,
L_0, of the Virasoro algebra. Assuming unitarity, the
Cardy formula then gives a microscopic entropy S_{micro}=2\pi
J / \hbar for the CFT, which reproduces the macroscopic
Bekenstein-Hawking entropy S_{macro}=Area / 4\hbar G.
The results apply to any consistent unitary quantum theory
of gravity with a Kerr solution. We accordingly conjecture
that extreme Kerr black holes are holographically dual
to a chiral two-dimensional conformal field theory with
central charge c_L=12J / \hbar, and in particular that
the near-extreme black hole GRS 1915+105 is approximately
dual to a CFT with c_L \sim 2 \times 10^{79}.
Abstract
We propose a new approach to implement quantum repeaters
for long distance quantum communication. Our protocol
generates a backbone of encoded Bell pairs and uses the
procedure of classical error correction during simultaneous
entanglement connection. We illustrate that the repeater
protocol with simple Calderbank-Shor-Steane (CSS) encoding
can significantly extend the communication distance,
while still maintaining a fast key generation rate.
| Title: |
|
Electrically Driven
Light Emission from Individual CdSe Nanowires |
| Authors: |
|
Doh, Yong-Joo; Maher, Kristin N.; Ouyang, Lian; Yu, Chun L.; Park, Hongkun; Park, Jiwoong |
| Publication: |
|
eprint arXiv:0809.3475 |
| Publication
Date: |
|
09/2008 |
| Origin: |
|
ARXIV |
| Keywords: |
|
Condensed Matter
- Materials Science, Condensed Matter - Mesoscopic
Systems and Quantum Hall Effect |
| Comment: |
|
12 pages, 4 figures |
| Bibliographic
Code: |
|
2008arXiv0809.3475D |
Abstract
We report electroluminescence (EL) measurements carried
out on three-terminal devices incorporating individual
n-type CdSe nanowires. Simultaneous optical and electrical
measurements reveal that EL occurs near the contact between
the nanowire and a positively biased electrode or drain.
The surface potential profile, obtained by using Kelvin
probe microscopy, shows an abrupt potential drop near
the position of the EL spot, while the band profile obtained
from scanning photocurrent microscopy indicates the existence
of an n-type Schottky barrier at the interface. These
observations indicate that light emission occurs through
a hole leakage or an inelastic scattering induced by
the rapid potential drop at the nanowire-electrode interface.
| Title: |
|
From F-theory GUTs
to the LHC |
| Authors: |
|
Heckman, Jonathan J.; Vafa, Cumrun |
| Publication: |
|
eprint arXiv:0809.3452 |
| Publication
Date: |
|
09/2008 |
| Origin: |
|
ARXIV |
| Keywords: |
|
High Energy Physics
- Phenomenology, High Energy Physics - Theory |
| Comment: |
|
34 pages, 2 figures |
| Bibliographic
Code: |
|
2008arXiv0809.3452H |
Abstract
This paper provides an overview to three recent papers
on the bottom up approach to GUTs in F-theory. We assume
only a minimal familiarity with string theory and phenomenology.
After explaining the potential for predictive string
phenomenology within this framework, we introduce the
ingredients of F-theory GUTs, and show how these models
naturally address various puzzles in four-dimensional
GUT models. We next describe how supersymmetry is broken,
and show that in a broad class of models, solving the
mu/B mu problem requires a specific scale of supersymmetry
breaking consistent with a particular deformation of
the gauge mediation scenario. This rigid structure enables
us to reliably extract predictions for the sparticle
spectrum of the MSSM. A brief sketch of expected LHC
signals, as well as ways to falsify this class of models
is also included.
Abstract
The possibility that Lorentz violation can generate differences
between the limiting velocities of light and charged
matter is considered. Such effects would either lead
to efficient vacuum Cherenkov radiation or rapid photon
decay. The absence of such effects for 104.5 GeV electrons
at the Large Electron Positron (LEP) collider and for
300 GeV photons at the Tevatron therefore constrains
this type of Lorentz breakdown. Within the context the
Standard-Model Extension (SME), these ideas imply an
experimental bound at the level of -5.8 x 10^{-12} <=
kappa_{trace} <= 1.2 x 10^{-11}, tightening existing
laboratory measurements by 3-4 orders of magnitude. Prospects
for further improvements with terrestrial and astrophysical
methods are discussed.
| Title: |
|
Mechanics of Individual,
Isolated Vortices in a Cuprate Superconductor |
| Authors: |
|
Auslaender, Ophir M.; Luan, Lan; Straver, Eric W. J.; Hoffman, Jennifer E.; Koshnick, Nicholas C.; Zeldov, Eli; Bonn, Douglas A.; Liang, Ruixing; Hardy, Walter N.; Moler, Kathryn A. |
| Publication: |
|
eprint arXiv:0809.2817 |
| Publication
Date: |
|
09/2008 |
| Origin: |
|
ARXIV |
| Keywords: |
|
Condensed Matter
- Superconductivity, Condensed Matter - Soft
Condensed Matter |
| Bibliographic
Code: |
|
2008arXiv0809.2817A |
Abstract
Superconductors often contain quantized microscopic whirlpools
of electrons, called vortices, that can be modeled as
one-dimensional elastic objects. Vortices are a diverse
playground for condensed matter because of the interplay
between thermal fluctuations, vortex-vortex interactions,
and the interaction of the vortex core with the three-dimensional
disorder landscape. While vortex matter has been studied
extensively, the static and dynamic properties of an
individual vortex have not. Here we employ magnetic force
microscopy (MFM) to image and manipulate individual vortices
in detwinned, single crystal YBa2Cu3O6.991 (YBCO), directly
measuring the interaction of a moving vortex with the
local disorder potential. We find an unexpected and dramatic
enhancement of the response of a vortex to pulling when
we wiggle it transversely. In addition, we find enhanced
vortex pinning anisotropy that suggests clustering of
oxygen vacancies in our sample and demonstrates the power
of MFM to probe vortex structure and microscopic defects
that cause pinning.
| Title: |
|
F-theory, GUTs, and
the Weak Scale |
| Authors: |
|
Heckman, Jonathan J.; Vafa, Cumrun |
| Publication: |
|
eprint arXiv:0809.1098 |
| Publication
Date: |
|
09/2008 |
| Origin: |
|
ARXIV |
| Keywords: |
|
High Energy Physics
- Theory, High Energy Physics - Phenomenology |
| Comment: |
|
v2:87 pages, 8 figures,
updated references, corrected typos |
| Bibliographic
Code: |
|
2008arXiv0809.1098H |
Abstract
In this paper we study a deformation of gauge mediated
supersymmetry breaking in a class of local F-theory GUT
models where the scale of supersymmetry breaking determines
the value of the mu term. Geometrically correlating these
two scales constrains the soft SUSY breaking parameters
of the MSSM. In this scenario, the hidden SUSY breaking
sector involves an anomalous U(1) Peccei-Quinn symmetry
which forbids bare mu and B mu terms. This sector typically
breaks supersymmetry at the desired range of energy scales
through a simple stringy hybrid of a Fayet and Polonyi
model. A variant of the Giudice-Masiero mechanism generates
the value mu ~ 10^2 - 10^3 GeV when the hidden sector
scale of supersymmetry breaking is F^(1/2) ~ 10^(8.5)
GeV. Further, the B mu problem is solved due to the mild
hierarchy between the GUT scale and Planck scale. These
models relate SUSY breaking with the QCD axion, and solve
the strong CP problem through an axion with decay constant
f_a ~ M_(GUT) * mu / L, where L ~ 10^5 GeV is the characteristic
scale of gaugino mass unification in gauge mediated models,
and the ratio \mu / L ~ M_(GUT)/M_(pl) ~ 10^(-3). We
find f_a ~ 10^12 GeV, which is near the high end of the
phenomenologically viable window. Here, the axino is
the goldstino mode which is eaten by the gravitino. The
gravitino is the LSP with a mass of about 10^1 - 10^2
MeV, and a bino-like neutralino is (typically) the NLSP
with mass of about 10^2 - 10^3 GeV. Compatibility with
electroweak symmetry breaking also determines the value
of tan(beta) ~ 30 +/- 7.
| Title: |
|
Hydrodynamic correlations
in the translocation of biopolymer through a
nanopore: theory and multiscale simulations |
| Authors: |
|
Fyta, Maria; Melchionna, Simone; Succi, Sauro; Kaxiras, Efthimios |
| Publication: |
|
eprint arXiv:0809.1035 |
| Publication
Date: |
|
09/2008 |
| Origin: |
|
ARXIV |
| Keywords: |
|
Physics - Biological
Physics, Physics - Computational Physics |
| Comment: |
|
7 pages, 5 figures.
to appear in Phys. Rev. E |
| Bibliographic
Code: |
|
2008arXiv0809.1035F |
Abstract
We investigate the process of biopolymer translocation
through a narrow pore using a multiscale approach which
explicitly accounts for the hydrodynamic interactions
of the molecule with the surrounding solvent. The simulations
confirm that the coupling of the correlated molecular
motion to hydrodynamics results in significant acceleration
of the translocation process. Based on these results,
we construct a phenomenological model which incorporates
the statistical and dynamical features of the translocation
process and predicts a power law dependence of the translocation
time on the polymer length with an exponent $\alpha$
$\approx 1.2$. The actual value of the exponent from
the simulations is $\alpha = 1.28 \pm 0.01$, which is
in excellent agreement with experimental measurements
of DNA translocation through a nanopore, and is not sensitive
to the choice of parameters in the simulation. The mechanism
behind the emergence of such a robust exponent is related
to the interplay between the longitudinal and transversal
dynamics of both translocated and untranslocated segments.
The connection to the macroscopic picture involves separating
the contributions from the blob shrinking and shifting
processes, which are both essential to the translocation
dynamics.
| Title: |
|
Imaging and manipulating
electrons in a 1D quantum dot with Coulomb blockade
microscopy |
| Authors: |
|
Qian, Jiang; Halperin, Bertrand I.; Heller, Eric J. |
| Publication: |
|
eprint arXiv:0809.0834 |
| Publication
Date: |
|
09/2008 |
| Origin: |
|
ARXIV |
| Keywords: |
|
Condensed Matter
- Mesoscopic Systems and Quantum Hall Effect |
| Comment: |
|
4 pages 7 figures |
| Bibliographic
Code: |
|
2008arXiv0809.0834Q |
Abstract
Motivated by the recent experiments by the Westervelt
group using a mobile tip to probe the electronic state
of quantum dots formed on a segmented nanowire, we study
the shifts in Coulomb blockade peak positions as a function
of the spatial variation of the tip potential, which
can be termed ``Coulomb blockade microscopy''. We show
that if the tip can be brought sufficiently close to
the nanowire, one can distinguish a high density electronic
liquid state from a Wigner crystal state by microscopy
with a weak tip potential. In the opposite limit of a
strongly negative tip potential, the potential depletes
the electronic density under it and divides the quantum
wire into two partitions. There the tip can push individual
electrons from one partition to the other, and the Coulomb
blockade micrograph can clearly track such transitions.
We show that this phenomenon can be used to qualitatively
estimate the relative importance of the electron interaction
compared to one particle potential and kinetic energies.
Finally, we propose that a weak tip Coulomb blockade
micrograph focusing on the transition between electron
number N=0 and N=1 states may be used to experimentally
map the one-particle potential landscape produced by
impurities and inhomogeneities.
| Title: |
|
Probing spatial spin
correlations of ultracold gases by quantum noise
spectroscopy |
| Authors: |
|
Bruun, G. M.; Andersen, Brian M.; Demler, Eugene; Sørensen, Anders S. |
| Publication: |
|
eprint arXiv:0809.0312 |
| Publication
Date: |
|
09/2008 |
| Origin: |
|
ARXIV |
| Keywords: |
|
Condensed Matter
- Other |
| Comment: |
|
4 pages, 3 figures |
| Bibliographic
Code: |
|
2008arXiv0809.0312B |
Abstract
Spin noise spectroscopy with a single laser beam is demonstrated
theoretically to provide a direct probe of the spatial
correlations of cold fermionic gases. We show how the
generic many-body phenomena of anti-bunching, pairing,
antiferromagnetic, and algebraic spin liquid correlations
can be revealed in the measured spin noise as a function
of laser width, temperature, and frequency.
| Title: |
|
Constraining Cosmic
Evolution of Type Ia Supernovae |
| Authors: |
|
Foley, Ryan J.; Filippenko, Alexei V.; Aguilera, C.; Becker, A. C.; Blondin, S.; Challis, P.; Clocchiatti, A.; Covarrubias, R.; Davis, T. M.; Garnavich, P. M.; Jha, S. W.; Kirshner, R. P.; Krisciunas, K.; Leibundgut, B.; Li, W.; Matheson, T.; Miceli, A.; Miknaitis, G.; Pignata, G.; Rest, A.; Riess, A. G.; Schmidt, B. P.; Smith, R. C.; Sollerman, J.; Spyromilio, J.; Stubbs, C. W.; Suntzeff, N. B.; Tonry, J. L.; Wood-Vasey, W. M.; Zenteno, A. |
| Publication: |
|
The Astrophysical
Journal, Volume 684, Issue 1, pp. 68-87. (ApJ
Homepage) |
| Publication
Date: |
|
09/2008 |
| Origin: |
|
UCP |
| ApJ Keywords: |
|
Cosmology: Observations,
Cosmology: Distance Scale, Stars: Supernovae:
General |
| Abstract
Copyright: |
|
(c) 2008: The American
Astronomical Society |
| DOI: |
|
10.1086/589612 |
| Bibliographic
Code: |
|
2008ApJ...684...68F |
Abstract
We present a large-scale effort of creating composite
spectra of high-redshift SNe Ia and comparing them to
low-redshift counterparts in an attempt to understand
possible cosmic evolution of SNe Ia, which has major
implications for studies of dark energy. Through the
ESSENCE project, we have obtained 107 spectra of 88 high-redshift
SNe Ia with excellent light-curve information. In addition,
we have obtained 397 spectra of low-redshift SNe Ia through
a multiple-decade effort at the Lick and Keck Observatories,
and we have used 45 UV spectra obtained by HST and IUE.
The low-redshift spectra act as a control sample when
comparing to the ESSENCE spectra. In all instances, the
ESSENCE and Lick composite spectra appear very similar.
The addition of galaxy light to the Lick composite spectra
allows an excellent match of the overall SED with the
ESSENCE composite spectra, indicating that the high-redshift
SNe are more contaminated with host galaxy light than
their low-redshift counterparts. This is caused by observing
objects at all redshifts with similar angular slit widths,
which corresponds to different projected physical distances.
After correcting for the galaxy light contamination,
a few marginally significant differences in the spectra
remain. We have estimated the systematic errors when
using current spectral templates for K-corrections to
be ~0.02 mag. The variance in the composite spectra gives
an estimate of the intrinsic variance in low-redshift
maximum light SN spectra of ~3% relative flux in the
optical and growing toward the UV. The difference between
the maximum light low- and high-redshift spectra constrains
the evolution of SN spectral features between our samples
to be <10% relative flux in the rest-frame optical.
Currently, galaxy contamination and the small samples
of rest-frame UV spectra at low and high redshifts are
the limiting factors for future studies.
| Title: |
|
Temperature dependence
of the emissivity of platinum in the IR |
| Authors: |
|
Deemyad, Shanti; Silvera, Isaac F. |
| Affiliation: |
|
Lyman Laboratory
of Physics, Harvard University, Cambridge, Massachusetts
02138, USA |
| Publication: |
|
Review of Scientific
Instruments, Volume 79, Issue 8, pp. 086105-086105-2
(2008). (RScI
Homepage) |
| Publication
Date: |
|
08/2008 |
| Origin: |
|
AIP |
| Keywords: |
|
emissivity, infrared
spectra, platinum, pyrometers |
| Abstract
Copyright: |
|
(c) 2008: American
Institute of Physics |
| DOI: |
|
10.1063/1.2966394 |
| Bibliographic
Code: |
|
2008RScI...79h6105D |
Abstract
The accuracy of temperature determination by fitting
the spectral irradiance to a Planck curve depends on
knowledge of the emissivity at all temperatures and pressures
of interest within a spectral region. Here, the emissivity
of platinum is measured in the near infrared as a function
of temperature. In the wavelength range of study and
the temperature range of 650-1100 K, we find the emissivity
to be independent of temperature to within experimental
error. This result should lead to improved accuracy of
temperature measurement by optical pyrometry where platinum
is used as a thermal emitter.
Abstract
The drying dynamics in three dimensional porous media
are studied with confocal microscopy. We observe abrupt
air invasions in size from single particle to hundreds
of particles. We show that these result from the strong
flow from menisci in large pores to menisci in small
pores during drying. This flow causes air invasions to
start in large menisci and subsequently spread throughout
the entire system. We measure the size and structure
of the air invasions and show that they are in accord
with invasion percolation. By varying the particle size
and contact angle we unambiguously demonstrate that capillary
pressure dominates the drying process.
| Title: |
Study of B Meson Decays
with Excited η and η' Mesons |
| Authors: |
Aubert, B.; Bona, M.; Boutigny, D.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prudent, X.; Tisserand, V.; Zghiche, A.; Garra Tico, J.;... Morii, M.;...;
and 563 coauthors. |
| Publication: |
Physical Review Letters,
vol. 101, Issue 9, id. 091801 (PhRvL
Homepage) |
| Publication
Date: |
08/2008 |
| Origin: |
APS |
| Abstract Copyright: |
(c) 2008: The American
Physical Society |
| DOI: |
10.1103/PhysRevLett.101.091801 |
| Bibliographic
Code: |
2008PhRvL.101i1801A |
Abstract: Using 383×10
6 B&Bmacr;
pairs from the BABAR data sample, we report results for
branching fractions of six charged B-meson decay modes,
where a charged kaon recoils against a charmless resonance
decaying to K&Kmacr;
* or ηππ final states
with mass in the range (1.2–1.8)GeV/c
2. We
observe a significant enhancement at the low K&Kmacr;
* invariant
mass which is interpreted as B
+→η(1475)K
+,
find evidence for the decay B
+→η(1295)K
+,
and place upper limits on the decays B
+→η(1405)K
+,
B
+→f
1(1285)K
+, B
+→f
1(1420)K
+,
and B
+→ϕ(1680)K
+.
| Title: |
Publisher's Note: Search
for Pair Production of Scalar Top Quarks Decaying
to a τ Lepton and a b Quark in p&pmacr; Collisions
at s=1.96TeV [Phys. Rev. Lett. 101, 071802 (2008)] |
| Authors: |
Aaltonen, T.; Adelman, J.; Akimoto, T.; Albrow, M. G.; Álvarez González, B.; Amerio, S.; Amidei, D.; Anastassov, A.;... Franklin, M.;
... Guimaraes da Costa, J....;
and 609 coauthors. |
| Publication: |
Physical Review Letters,
vol. 101, Issue 8, id. 089901 (PhRvL
Homepage) |
| Publication
Date: |
08/2008 |
| Origin: |
APS |
| Abstract Copyright: |
(c) 2008: The American
Physical Society |
| DOI: |
10.1103/PhysRevLett.101.089901 |
| Bibliographic
Code: |
2008PhRvL.101h9901A |
Abstract: Not Available
| Title: |
Observation of Y(3940)→J/ψω
in B→J/ψωK at BABAR |
| Authors: |
Aubert, B.; Bona, M.; Boutigny, D.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prudent, X.; Tisserand, V.; Zghiche, A.; Garra Tico, J.;... Morii, M.;...;
and 561 coauthors. |
| Publication: |
Physical Review Letters,
vol. 101, Issue 8, id. 082001 (PhRvL
Homepage) |
| Publication
Date: |
08/2008 |
| Origin: |
APS |
| Abstract Copyright: |
(c) 2008: The American
Physical Society |
| DOI: |
10.1103/PhysRevLett.101.082001 |
| Bibliographic
Code: |
2008PhRvL.101h2001A |
Abstract: We present a study
of the decays B
0,+→J/ψωK
0,+ using
383×10
6 B&Bmacr; events obtained with the
BABAR detector at PEP-II. We observe Y(3940)→J/ψω, with
mass 3914.6
-3.4+3.8(stat)±2.0(syst)MeV/c
2,
and width 34
-8+12(stat)±5(syst)MeV.
The ratio of B
0 and B
+ decay to
YK is 0.27
-0.23+0.28(stat)
-0.01+0.04(syst),
and the relevant B
0 and B
+ branching
fractions are reported.
| Title: |
Measurements of B→{π,η,η'}lνl Branching
Fractions and Determination of |Vub|
with Semileptonically Tagged B Mesons |
| Authors: |
Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E.; Prudent, X.; Tisserand, V.; Garra Tico, J.;... Morii, M.;...;
and 527 coauthors. |
| Publication: |
Physical Review Letters,
vol. 101, Issue 8, id. 081801 (PhRvL
Homepage) |
| Publication
Date: |
08/2008 |
| Origin: |
APS |
| Abstract Copyright: |
(c) 2008: The American
Physical Society |
| DOI: |
10.1103/PhysRevLett.101.081801 |
| Bibliographic
Code: |
2008PhRvL.101h1801A |
Abstract: We report measurements
of branching fractions for the decays B→Pℓν
ℓ,
where P are the pseudoscalar charmless mesons π
-,
π
0, η and η
', based on 348fb
-1 of
data collected with the BABAR detector, using B
0 and
B
+ mesons found in the recoil of a second
B meson decaying as B→D
(*)ℓν
ℓ.
Assuming isospin symmetry, we combine pionic branching
fractions to obtain B(B
0→π
-ℓ
+ν
ℓ)=(1.54±0.17
(stat)±0.09
(syst))×10
-4;
we find 3.2σ evidence of the decay B
+→ηℓ
+ν
ℓ and
measure its branching fraction to be (0.64±0.20
(stat)±0.03
(syst))×10
-4,
and determine B(B
+→η
'ℓ
+ν
ℓ)<0.47×10
-4 to
90% confidence level. Using partial branching fractions
for the pionic decays in ranges of the momentum transfer
and a variety of form factor calculation, we obtain values
of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix
element |V
ub| in ranging from 3.6×10
-3 to
4.1×10
-3.
| Title: |
|
Suppression of Inelastic
Collisions Between Polar Molecules With a Repulsive
Shield |
| Authors: |
|
Gorshkov, A. V.; Rabl, P.; Pupillo, G.; Micheli, A.; Zoller, P.; Lukin, M. D.; Büchler, H. P. |
| blication: |
|
Physical Review Letters,
vol. 101, Issue 7, id. 073201 (PhRvL
Homepage) |
| Publication
Date: |
|
08/2008 |
| Origin: |
|
APS |
| Abstract
Copyright: |
|
(c) 2008: The American
Physical Society |
| DOI: |
|
10.1103/PhysRevLett.101.073201 |
| Bibliographic
Code: |
|
2008PhRvL.101g3201G |
Abstract
We propose and analyze a technique that allows one to
suppress inelastic collisions and simultaneously enhance
elastic interactions between cold polar molecules. The
main idea is to cancel the leading dipole-dipole interaction
with a suitable combination of static electric and microwave
fields in such a way that the remaining van der Waals-type
potential forms a three-dimensional repulsive shield.
We analyze the elastic and inelastic scattering cross
sections relevant for evaporative cooling of polar molecules
and discuss the prospect for the creation of stable crystalline
structures.
| Title: |
Search for Pair Production
of Scalar Top Quarks Decaying to a τ Lepton and
a b Quark in p&pmacr; Collisions at s=1.96TeV |
| Authors: |
Aaltonen, T.; Adelman, J.; Akimoto, T.; Albrow, M. G.; Álvarez González, B.; Amerio, S.; Amidei, D.; Anastassov, A.;... Franklin, M.;
... Guimaraes da Costa, J....;
and 609 coauthors. |
| Publication: |
Physical Review Letters,
vol. 101, Issue 7, id. 071802 (PhRvL
Homepage) |
| Publication
Date: |
08/2008 |
| Origin: |
APS |
| Abstract Copyright: |
(c) 2008: The American
Physical Society |
| DOI: |
10.1103/PhysRevLett.101.071802 |
| Bibliographic
Code: |
2008PhRvL.101g1802A |
Abstract: We search for
pair production of supersymmetric top quarks (&ttilde;
1),
followed by R-parity violating decay
&ttilde;
1→τb with a branching ratio β, using
322pb
-1 of p&pmacr; collisions at s=1.96TeV
collected by the upgraded Collider Detector at Fermilab.
Two candidate events pass our final selection criteria,
consistent with the standard model expectation. We set
upper limits on the cross section σ(&ttilde;
1&ttilde;¯
1)×β
2 as
a function of the top-squark mass m(&ttilde;
1).
Assuming β=1, we set a 95% confidence level limit m(&ttilde;
1)>153GeV/c
2.
The limits are also applicable to the case of a third-generation
scalar leptoquark (LQ
3) decaying LQ
3→τb.
| Title: |
Improved measurement
of the CKM angle γ in B∓→D(*)K(*)∓ decays
with a Dalitz plot analysis of D decays to KS0π+π- and
KS0K+K- |
| Authors: |
Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E.; Prudent, X.; Tisserand, V.; Garra Tico, J.;... Morii, M.;...;
and 534 coauthors. |
| Publication: |
Physical Review D,
vol. 78, Issue 3, id. 034023 (PhRvD
Homepage) |
| Publication
Date: |
08/2008 |
| Origin: |
APS |
| Abstract Copyright: |
(c) 2008: The American
Physical Society |
| DOI: |
10.1103/PhysRevD.78.034023 |
| Bibliographic
Code: |
2008PhRvD..78c4023A |
Abstract: We report on an
improved measurement of the Cabibbo-Kobayashi-Maskawa
CP-violating phase γ through a Dalitz plot analysis of
neutral D meson decays to K
S0π
+π
- and
K
S0K
+K
- produced
in the processes B
∓→DK
∓, B
∓→D
*K
∓ with
D
*→Dπ
0, Dγ, and B
∓→DK
*∓ with
K
*∓→K
S0π
∓.
Using a sample of 383×10
6 B&Bmacr; pairs collected
by the BABAR detector, we measure γ=(76±22±5±5)° (mod
180°), where the first error is statistical, the second
is the experimental systematic uncertainty, and the third
reflects the uncertainty on the description of the Dalitz
plot distributions. The corresponding 2-standard-deviation
region is 29°<γ<122°. This result has a significance
of direct CP violation (γ≠0) of 3.0 standard deviations.
| Title: |
Search for heavy, long-lived
neutralinos that decay to photons at CDF II using
photon timing |
| Authors: |
Aaltonen, T.; Adelman, J.; Akimoto, T.; Albrow, M. G.; González, B. Álvarez; Amerio, S.; Amidei, D.; Anastassov, A.;
... Franklin, M.;
... Guimaraes da Costa, J....;
and 590 coauthors. |
| Publication: |
Physical Review D,
vol. 78, Issue 3, id. 032015 (PhRvD
Homepage) |
| Publication
Date: |
08/2008 |
| Origin: |
APS |
| Abstract Copyright: |
(c) 2008: The American
Physical Society |
| DOI: |
10.1103/PhysRevD.78.032015 |
| Bibliographic
Code: |
2008PhRvD..78c2015A |
Abstract: We present the
results of the first hadron collider search for heavy,
long-lived neutralinos that decay via χ˜
10→γ&Gtilde;
in gauge-mediated supersymmetry breaking models. Using
an integrated luminosity of 570±34pb
-1 of
p&pmacr; collisions at s=1.96TeV, we select γ+jet+missingtransverseenergy
candidate events based on the arrival time of a high-energy
photon at the electromagnetic calorimeter as measured
with a timing system that was recently installed on the
CDF II detector. We find 2 events, consistent with the
background estimate of 1.3±0.7 events. While our search
strategy does not rely on model-specific dynamics, we
set cross section limits and place the world-best 95%
C.L. lower limit on the χ˜
10 mass
of 101GeV/c
2 at τ
χ˜10=5ns.
| Title: |
Search for standard
model Higgs boson production in association with
a W boson at CDF |
| Authors: |
Aaltonen, T.; Adelman, J.; Akimoto, T.; Albrow, M. G.; González, B. Álvarez; Amerio, S.; Amidei, D.; Anastassov, A.;
... Franklin, M.;
... Guimaraes da Costa, J....;
and 587 coauthors. |
| Publication: |
Physical Review D,
vol. 78, Issue 3, id. 032008 (PhRvD
Homepage) |
| Publication
Date: |
08/2008 |
| Origin: |
APS |
| Abstract Copyright: |
(c) 2008: The American
Physical Society |
| DOI: |
10.1103/PhysRevD.78.032008 |
| Bibliographic
Code: |
2008PhRvD..78c2008A |
Abstract: We present a search
for standard model Higgs boson production in association
with a W boson in proton-antiproton collisions (p&pmacr;→W
±H→ℓνb&bmacr;)
at a center of mass energy of 1.96 TeV. The search employs
data collected with the CDF II detector which correspond
to an integrated luminosity of approximately 1fb
-1.
We select events consistent with a signature of a single
lepton (e
±/μ
±), missing transverse
energy, and two jets. Jets corresponding to bottom quarks
are identified with a secondary vertex tagging method
and a neural network filter technique. The observed number
of events and the dijet mass distributions are consistent
with the standard model background expectations, and
we set 95% confidence level upper limits on the production
cross section times branching ratio ranging from 3.9
to 1.3 pb for Higgs boson masses from 110 to 150GeV/c
2,
respectively.
| Title: |
|
Microscopic dynamics
at the glass transition: insights from soft colloidal
dispersions |
| Authors: |
|
Romeo, G.; Imperiali, L.; Nieves, A. F.; Acierno, D.; Weitz, D. A. |
| Publication: |
|
IV INTERNATIONAL
CONFERENCE TIMES OF POLYMERS (TOP) AND COMPOSITES.
AIP Conference Proceedings, Volume 1042, pp.
52-54 (2008). (AIPC
Homepage) |
| Publication
Date: |
|
08/2008 |
| Origin: |
|
AIP |
| Keywords: |
|
reaction kinetics,
surface chemistry, glass transition, molecular
dynamics method, polymerisation, optical microscopy,
molecular configurations |
| Abstract
Copyright: |
|
(c) 2008: American
Institute of Physics |
| DOI: |
|
10.1063/1.2989070 |
| Bibliographic
Code: |
|
2008AIPC.1042...52R |
Abstract
We investigate the microscopic dynamics of compressible
colloidal particles as function of concentration through
dynamic light scattering and confocal microscopy experiments.
In analogy with hard sphere (HS) colloidal systems, we
find that the particles display liquid, supercooled liquid
or glassy dynamics, depending on volume fraction. In
the present case, however caging effects are observed
for particle volume fractions higher than one, i.e. when
the particles are compressed. We find that heterogeneous
dynamics, described by a non Gaussian distribution of
the displacements, play a major role in the supercooled
liquid in proximity of the relaxation time.
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