68 research outputs found
Inclusive Production of Four Charm Hadrons in e^+ e^- Annihilation at B Factories
Measurements by the Belle Collaboration of the exclusive production of two
charmonia in e^+ e^- annihilation differ substantially from theoretical
predictions. Till now, no conclusive explanation for this remarkable
discrepancy has been provided. Even the origin of the discrepancy is not
identified, yet. We suggest that the measurement of four-charm events in Belle
data must provide a strong constraint in identifying the origin of this large
discrepancy. Our prediction of the cross section for e^+e^- -> c c-bar c c-bar,
in lowest order in strong coupling constant, at sqrt{s}=10.6 GeV is about 0.1
pb. If measured four-charm cross section is compatible with the prediction
based on perturbative QCD, it is very likely that factorization of
hadronization process from perturbative part may be significantly violated or
there exists a new production mechanism. If the cross section for the
four-charm event is also larger than the prediction like that for the exclusive
J/psi+eta_c production, perturbative QCD expansion itself will be proved to be
unreliable and loses predictive power.Comment: 4 pages, 3 figures, version published in Phys. Rev. D as a Rapid
Communicatio
Inclusive Charm Production in Upsilon(nS) Decay
Based on the NRQCD factorization formalism, we calculate the inclusive charm
production rate in Upsilon(nS) decay at leading order in the strong coupling
constant alpha_s and the relative velocity v of the b quark in the quarkonium
rest frame. The branching fractions for Upsilon(nS) to charm for n=1, 2, and 3
are all around 7-9%. About 60% of the branching fraction into charm is from
annihilation of the color-singlet bb-bar pair into gamma^* -> cc-bar. Most of
the remaining branching fraction is from annihilation of the color-singlet
bb-bar pair decaying into cc-bar gg. We also compute the momentum distributions
of the charm quark and charmed hadrons in the decays. The virtual-photon
contribution to the charm quark momentum distribution is concentrated at the
end point while the cc-bar gg contribution is broad. The momentum distributions
for charmed hadrons are obtained by convolving the charm-quark momentum
distribution with charm fragmentation functions. This makes the momentum
distributions for charmed hadrons softer than that for the charm quark. This
effect is particularly significant in the virtual-photon contribution.Comment: 27 pages, 5 figures, minor corrections. version published in Phys.
Rev.
Color-evaporation-model calculation of e^+ e^- -> J/psi+cc-bar+X at root-s=10.6 GeV
Measurements by the Belle Collaboration of the cross section for inclusive
J/psi production in e^+e^- annihilation have been a serious challenge to
current heavy-quarkonium theory. Especially, the measured cross sections for
exclusive J/psi+eta_c and inclusive J/psi+cc-bar+X differ from nonrelativistic
QCD predictions by an order of magnitude. In order to check if other available
alternative theory can resolve such a large discrepancy, we calculate the cross
section for inclusive J/psi+cc-bar+X based on the color-evaporation model. As a
phenomenological model, the color-evaporation model is still employed to
predict cross sections for inclusive quarkonium production in various
processes. Our results show that the color-evaporation-model prediction is even
smaller than the nonrelativistic QCD prediction by an order of magnitude. The
resultant color-evaporation-model prediction for J/psi+cc-bar+X fraction in the
inclusive J/psi production cross section is 0.049, while the empirical value
measured by the Belle Collaboration is 0.82.Comment: 8 pages, 3 figures, text improved, version published in Physical
Review
Integrated Quantum Optical Phase Sensor
The quantum noise of light fundamentally limits optical phase sensors. A
semiclassical picture attributes this noise to the random arrival time of
photons from a coherent light source such as a laser. An engineered source of
squeezed states suppresses this noise and allows sensitivity beyond the
standard quantum limit (SQL) for phase detection. Advanced gravitational wave
detectors like LIGO have already incorporated such sources, and nascent efforts
in realizing quantum biological measurements have provided glimpses into new
capabilities emerging in quantum measurement. We need ways to engineer and use
quantum light within deployable quantum sensors that operate outside the
confines of a lab environment. Here we present a photonic integrated circuit
fabricated in thin-film lithium niobate that provides a path to meet these
requirements. We use the second-order nonlinearity to produce a squeezed state
at the same frequency as the pump light and realize circuit control and sensing
with electro-optics. Using a 26.2 milliwatts of optical power, we measure (2.7
0.2 ) squeezing and apply it to increase the signal-to-noise ratio of
phase measurement. We anticipate that on-chip photonic systems like this, which
operate with low power and integrate all of the needed functionality on a
single die, will open new opportunities for quantum optical sensing.Comment: 14 pages, 3+3 figure
Mid-infrared spectroscopy with a broadly tunable thin-film lithium niobate optical parametric oscillator
Mid-infrared spectroscopy, an important and widespread technique for sensing
molecules, has encountered barriers stemming from sources either limited in
tuning range or excessively bulky for practical field use. We present a
compact, efficient, and broadly tunable optical parametric oscillator (OPO)
device surmounting these challenges. Leveraging a dispersion-engineered
singly-resonant OPO implemented in thin-film lithium niobate-on-sapphire, we
achieve broad and controlled tuning over an octave, from 1.5 to 3.3 microns by
combining laser and temperature tuning. The device generates > 25 mW of
mid-infrared light at 3.2 microns, offering a power conversion efficiency of
15% (45% quantum efficiency). We demonstrate the tuning and performance of the
device by successfully measuring the spectra of methane and ammonia, verifying
our approach's relevance for gas sensing. Our device signifies an important
advance in nonlinear photonics miniaturization and brings practical field
applications of high-speed and broadband mid-infrared spectroscopy closer to
reality.Comment: 19 pages, 11 figure
Integrated frequency-modulated optical parametric oscillator
Optical frequency combs have revolutionized precision measurement,
time-keeping, and molecular spectroscopy. A substantial effort has developed
around "microcombs": integrating comb-generating technologies into compact,
reliable photonic platforms. Current approaches for generating these microcombs
involve either the electro-optic (EO) or Kerr mechanisms. Despite rapid
progress, maintaining high efficiency and wide bandwidth remains challenging.
Here, we introduce a new class of microcomb -- an integrated optical frequency
comb generator that combines electro-optics and parametric amplification to
yield a frequency-modulated optical parametric oscillator (FM-OPO). In stark
contrast to EO and Kerr combs, the FM-OPO microcomb does not form pulses but
maintains operational simplicity and highly efficient pump power utilization
with an output resembling a frequency-modulated laser. We outline the working
principles of FM-OPO and demonstrate them by fabricating the complete optical
system in thin-film lithium niobate (LNOI). We measure pump to comb internal
conversion efficiency exceeding 93% (34% out-coupled) over a nearly flat-top
spectral distribution spanning approximately 1,000 modes (approximately 6 THz).
Compared to an EO comb, the cavity dispersion rather than loss determines the
FM-OPO bandwidth, enabling broadband combs with a smaller RF modulation power.
The FM-OPO microcomb, with its robust operational dynamics, high efficiency,
and large bandwidth, contributes a new approach to the field of microcombs and
promises to herald an era of miniaturized precision measurement, and
spectroscopy tools to accelerate advancements in metrology, spectroscopy,
telecommunications, sensing, and computing.Comment: 8 pages, 4 figures main text; another 19 pages and 9 figures in
methods and supplementar
Single-Mode Squeezed Light Generation and Tomography with an Integrated Optical Parametric Oscillator
Quantum optical technologies promise advances in sensing, computing, and
communication. A key resource is squeezed light, where quantum noise is
redistributed between optical quadratures. We introduce a monolithic,
chip-scale platform that exploits the nonlinearity of a thin-film
lithium niobate (TFLN) resonator device to efficiently generate squeezed states
of light. Our system integrates all essential components -- except for the
laser and two detectors -- on a single chip with an area of one square
centimeter, significantly reducing the size, operational complexity, and power
consumption associated with conventional setups. Our work addresses challenges
that have limited previous integrated nonlinear photonic implementations that
rely on either nonlinear resonators or on integrated waveguide
parametric amplifiers. Using the balanced homodyne measurement
subsystem that we implemented on the same chip, we measure a squeezing of 0.55
dB and an anti-squeezing of 1.55 dB. We use 20 mW of input power to generate
the parametric oscillator pump field by employing second harmonic generation on
the same chip. Our work represents a substantial step toward compact and
efficient quantum optical systems posed to leverage the rapid advances in
integrated nonlinear and quantum photonics.Comment: 21 pages; 4 figures in main body, 8 supplementary figure
Identification of novel candidate variants including COL6A6 polymorphisms in early-onset atopic dermatitis using whole-exome sequencing
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