1,935 research outputs found
The Debye-Waller Factor in solid 3He and 4He
The Debye-Waller factor and the mean-squared displacement from lattice sites
for solid 3He and 4He were calculated with Path Integral Monte Carlo at
temperatures between 5 K and 35 K, and densities between 38 nm^(-3) and 67
nm^(-3). It was found that the mean-squared displacement exhibits finite-size
scaling consistent with a crossover between the quantum and classical limits of
N^(-2/3) and N^(-1/3), respectively. The temperature dependence appears to be
T^3, different than expected from harmonic theory. An anisotropic k^4 term was
also observed in the Debye-Waller factor, indicating the presence of
non-Gaussian corrections to the density distribution around lattice sites. Our
results, extrapolated to the thermodynamic limit, agree well with recent values
from scattering experiments.Comment: 5 figure
Deep Optical Imaging of A Compact Group of Galaxies, Seyfert's Sextet
In order to investigate the dynamical status of Seyfert's Sextet (SS), we
have obtained a deep optical () image of this group. Our image shows that
a faint envelope, down to a surface brightness (AB) mag arcsec, surrounds the member galaxies. This envelope is
irregular in shape. It is likely that this shape is attributed either to
recent-past or to on-going galaxy interactions in SS. If the member galaxies
have experienced a number of mutual interactions over a long timescale, the
shape of the envelope should be rounder. Therefore, the irregular-shaped
morphology suggests that SS is in an early phase of dynamical interaction among
the member galaxies. It is interesting to note that the soft X-ray image
obtained with ROSAT (Pildis et al. 1995) is significantly similar in
morphology. We discuss the possible future evolution of SS briefly.Comment: 7 pages text (emulateapj LaTeX), 8 figures (3 EPS files, 1 PostScript
file, and 4 jpeg files) figures, The Astronomical Journal, 120, No. 5 inpres
Supermassive Black Holes in Galactic Nuclei: Past, Present and Future Research
This review discusses the current status of supermassive black hole research,
as seen from a purely observational standpoint. Since the early '90s, rapid
technological advances, most notably the launch of the Hubble Space Telescope,
the commissioning of the VLBA and improvements in near-infrared speckle imaging
techniques, have not only given us incontrovertible proof of the existence of
supermassive black holes, but have unveiled fundamental connections between the
mass of the central singularity and the global properties of the host galaxy.
It is thanks to these observations that we are now, for the first time, in a
position to understand the origin, evolution and cosmic relevance of these
fascinating objects.Comment: Invited Review, 114 pages. Because of space requirements, this
version contains low resolution figures. The full resolution version can be
downloaded from http://www.physics.rutgers.edu/~lff/publications.htm
Observation of two new baryon resonances
Two structures are observed close to the kinematic threshold in the mass spectrum in a sample of proton-proton collision data, corresponding
to an integrated luminosity of 3.0 fb recorded by the LHCb experiment.
In the quark model, two baryonic resonances with quark content are
expected in this mass region: the spin-parity and
states, denoted and .
Interpreting the structures as these resonances, we measure the mass
differences and the width of the heavier state to be
MeV,
MeV,
MeV, where the first and second
uncertainties are statistical and systematic, respectively. The width of the
lighter state is consistent with zero, and we place an upper limit of
MeV at 95% confidence level. Relative
production rates of these states are also reported.Comment: 17 pages, 2 figure
Search for CP violation in decays
A model-independent search for direct CP violation in the Cabibbo suppressed
decay in a sample of approximately 370,000 decays is
carried out. The data were collected by the LHCb experiment in 2010 and
correspond to an integrated luminosity of 35 pb. The normalized Dalitz
plot distributions for and are compared using four different
binning schemes that are sensitive to different manifestations of CP violation.
No evidence for CP asymmetry is found.Comment: 13 pages, 8 figures, submitted to Phys. Rev.
Observation of an Excited Bc+ State
Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+Ï+Ï- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bcâ(2S31)+ state reconstructed without the low-energy photon from the Bcâ(1S31)+âBc+Îł decay following Bcâ(2S31)+âBcâ(1S31)+Ï+Ï-. A second state is seen with a global (local) statistical significance of 2.2Ï (3.2Ï) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date
Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma
and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a
centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The
value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08
^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical,
the second systematic and the third is associated to the ratio of fragmentation
fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/-
0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be
(3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table
Precision measurement of violation in decays
The time-dependent asymmetry in decays is
measured using collision data, corresponding to an integrated luminosity
of fb, collected with the LHCb detector at centre-of-mass energies
of and TeV. In a sample of 96 000 decays, the
-violating phase is measured, as well as the decay widths
and of the light and heavy mass eigenstates of the
system. The values obtained are rad, ps, andps, where the first uncertainty is
statistical and the second systematic. These are the most precise single
measurements of those quantities to date. A combined analysis with decays gives rad. All
measurements are in agreement with the Standard Model predictions. For the
first time the phase is measured independently for each polarisation
state of the system and shows no evidence for polarisation
dependence.Comment: 6 figure
Measurement of the CKM angle Îł from a combination of B±âDh± analyses
A combination of three LHCb measurements of the CKM angle Îł is presented. The decays B±âD K± and
B±âDϱ are used, where D denotes an admixture of D0 and D0 mesons, decaying into K+Kâ, Ï+Ïâ, K±Ïâ, K±ÏâϱÏâ, K0SÏ+Ïâ, or K0S K+Kâ ïŹnal states. All measurements use a dataset corresponding to 1.0 fbâ1 of integrated luminosity. Combining results from B±âD K± decays alone a best-ïŹt value of
Îł =72.0⊠is found, and conïŹdence intervals are set
Îł â [56.4,86.7]⊠at 68% CL,
Îł â [42.6,99.6]⊠at 95% CL.
The best-ïŹt value of Îł found from a combination of results from B±âDϱ decays alone, is Îł =18.9âŠ,
and the conïŹdence intervals
Îł â [7.4,99.2]⊠âȘ [167.9,176.4]⊠at 68% CL
are set, without constraint at 95% CL. The combination of results from B± â D K± and B± â Dϱ
decays gives a best-ïŹt value of Îł =72.6⊠and the conïŹdence intervals
Îł â [55.4,82.3]⊠at 68% CL,
Îł â [40.2,92.7]⊠at 95% CL
are set. All values are expressed modulo 180âŠ, and are obtained taking into account the effect of D0âD0
mixing
Search for the rare decays and
A search for the rare decay of a or meson into the final
state is performed, using data collected by the LHCb experiment
in collisions at and TeV, corresponding to an integrated
luminosity of 3 fb. The observed number of signal candidates is
consistent with a background-only hypothesis. Branching fraction values larger
than for the decay mode are
excluded at 90% confidence level. For the decay
mode, branching fraction values larger than are excluded at
90% confidence level, this is the first branching fraction limit for this
decay.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-044.htm
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