770 research outputs found
B Physics at the TeVatron
The CDF and D\O\ experiments at the Tevatron collider established
that extensive and detailed exploration of the --quark dynamics is possible
in hadron collisions, with results competitive and supplementary to those from
colliders. This provides a rich, and highly rewarding program that is
currently reaching full maturity. I report a few recent world-leading results
on rare decays, CP-violation in mixing, penguin decays, and
charm physics.Comment: 5 pages, 1 figure, proceedings for IFAE2011. To be published in the
Nuovo Cimento C - Colloquia on Physic
Measurement of CP Violation in
Charm physics has played all along a central role in particle physics,
however the level of attention on it has tremendously increased in the last
years because of the observation of "fast" flavour oscillations
and because of very recent observed hints of CP violation. While in the past
these would have been unambiguously interpreted as signs of New Physics, the
revisitation of theoretical expectations, prompted by the latest experimental
measurements, makes the picture not clear. This brief review covers the current
status of CP-violating measurements in the system, both on the
experimental and theoretical side.Comment: 17 pages, 6 figures, 3 tables. Accepted by Modern Physics Letters A
journa
Mixing and violation in decays
The theoretical parametrisation of mixing and time-dependent violation
for decays into two hadrons is reviewed, along with the experimental
methods to measure them. While these phenomena are usually neglected for decays, this approximation is not always justified at the
current level of experimental precision. In particular, it is shown to produce
a bias on the measurement of the parameter , when this is performed by
relying on decays as normalisation channel, whose size is
around 40% of the precision of the current world average. The sensitivity to
violation in the mixing achievable by studying and
untagged decays, where stands for either of or
mesons, is also estimated.Comment: 19 pages, 2 figures; fitting code available at
https://github.com/tpajero/charm-fitter; v2 prepared for submission to JHEP
(added 2 figures, fixed minor typos in equations, updated the values of charm
mixing parameters
AQUIFER Nano-Electrofuel Energy Economy and Powered Aircraft Operations
The Aqueous, QUick-charging battery Integration For Electric flight Research project is explained and the major subsystems are described, including nano-electric fluid, rim-driven motors, and integration concepts. The nano-electric fluid concept is a new type of aqueous flow battery that could reduce or retire the fire and explosion hazards of conventional batteries and fuel cells. The nano-electric fluid itself could enable energy storage and increased available energy per fuel weight ratios. The rim-driven motor is being developed to improve propulsion system safety and stability and to reduce noise. The rim-driven motor concept could enable motors that are more efficient both electrically and aerodynamically. The Energy Economy of the project concept is presented as a potential renewable or green energy sustainment for utilizing in-place infrastructure. The nano-electric fluid energy charge-use-recharge cycle is presented using renewable energy input from solar, wind, and hydroelectricity. Powered aircraft operations are presented, and the logistics of the new nano-electric fluid technology are explored. Powered aircraft operations topics include weight and balance, fueling, recharging, safety, and derivative considerations
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Measurements of CP asymmetries and branching fractions of two-body charmless decays of B^0 and B^0_s mesons
The thesis is organized as follows: Chapter 1 describes the theoretical framework of non-leptonic B{sub (s)}{sup 0} {yields} H{sup +}h{prime}{sup -} decays, with a simple overview of the CP violation mechanism within the Standard Model and of the most used phenomenological approaches in the evaluation of strong interaction contributions. The chapter contains also a review of the theoretical expectations and the current experimental measurements along with a discussion about the importance of studying such decays. Chapter 2 contains a general description of the Tevatron collider and of the CDF II detector. Chapter 3 is devoted to the description of the data sample used for the measurement and the method used in extracting the signal from the background. Particular attention is dedicated to the on-line trigger selection, which is crucial to collect a sample enriched in B{sub (s)}{sup 0} {yields} h{sup +}h{prime}{sup -} decays. Chapter 4 shows how the information from kinematics and particle identification was used to achieve a statistical discrimination amongst modes to extract individual measurements. The available resolutions in mass or in particle identification are separately insufficient for an event-by-event separation of B{sub (s)}{sup 0} {yields} h{sup +}h{prime}{sup -} modes. The choice of observables and the technique used to combine them is an important and innovative aspect of the analysis described in this thesis. Chapter 5 is devoted to the accurate determination of the invariant mass lineshape. This is a crucial ingredient for resolving overlapping mass peaks. This chapter details all resolution effects with particular attention at the tails due to the emission of low-energy photons from charged kaons and pions in the final state (FSR). For the first time the effect of FSR has been accurately accounted for in a CDF analysis. Chapter 6 describes how kinematic and PID information, discussed in chap. 4 and chap. 5 were combined in a maximum Likelihood fit to statistically determine the composition of the B{sub (s)}{sup 0} {yields} h{sup +}h{prime}{sup -} sample. This kinematics-PID combined fit has been developed and performed for the first time at CDF in the analysis presented in this thesis and this methodology was later inherited by several other analyses. Chapter 7 is devoted to the study of the isolation variable, which is a crucial handle to enhance the signal-to-background ratio in the off-line selection. It exploits the property that the b-hadrons tend to carry a larger fraction of the transverse momentum of the particles produced in the fragmentation, with respect to lighter hadrons. Since the simulators do not accurately reproduce the fragmentation processes, this chapter is devoted to the study of the control data sample of B{sub (s)}{sup 0} {yields} J/{psi}X decays to probe the characteristics of this variable. Chapter 8 describes an innovative procedure used to optimize the selection to minimize the statistical uncertainty on the quantities one wishes to measure. The procedure is based on the fit of composition described in chap. 6. Chapter 9 reports the results of the fit of composition described in chap. 6 and the cross-checks performed to verify the goodness of the fit of composition. In order to translate the parameters returned from the fit into physics measurements the relative efficiency corrections between the various decay modes need to be applied. Chapter 10 is devoted to the description of these corrections. Chapter 11 describes the measurement of the detector-induced charge asymmetry between positively and negatively charged kaons and pions, due to their different probability of strong interaction in the tracker material using the real data. This allows to extract the acceptance correction factor for the CP asymmetries measurement without any external inputs from the simulation, and to perform a powerful check of whole analysis. Chapter 12 describes the main sources of systematic uncertainties and the method used to evaluate the significance of the results on rare modes. The final results of the measurements and their interpretation are discussed in chap. 13
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Nightside clouds and disequilibrium chemistry on the hot Jupiter WASP-43b
Hot Jupiters are among the best-studied exoplanets, but it is still poorly understood how their chemical composition and cloud properties vary with longitude. Theoretical models predict that clouds may condense on the nightside and that molecular abundances can be driven out of equilibrium by zonal winds. Here we report a phase-resolved emission spectrum of the hot Jupiter WASP-43b measured from 5 μm to 12 μm with the JWST’s Mid-Infrared Instrument. The spectra reveal a large day–night temperature contrast (with average brightness temperatures of 1,524 ± 35 K and 863 ± 23 K, respectively) and evidence for water absorption at all orbital phases. Comparisons with three-dimensional atmospheric models show that both the phase-curve shape and emission spectra strongly suggest the presence of nightside clouds that become optically thick to thermal emission at pressures greater than ~100 mbar. The dayside is consistent with a cloudless atmosphere above the mid-infrared photosphere. Contrary to expectations from equilibrium chemistry but consistent with disequilibrium kinetics models, methane is not detected on the nightside (2σ upper limit of 1–6 ppm, depending on model assumptions). Our results provide strong evidence that the atmosphere of WASP-43b is shaped by disequilibrium processes and provide new insights into the properties of the planet’s nightside clouds. However, the remaining discrepancies between our observations and our predictive atmospheric models emphasize the importance of further exploring the effects of clouds and disequilibrium chemistry in numerical models.Peer reviewe
Nightside clouds and disequilibrium chemistry on the hot Jupiter WASP-43b
Hot Jupiters are among the best-studied exoplanets, but it is still poorly understood how their chemical composition and cloud properties vary with longitude. Theoretical models predict that clouds may condense on the nightside and that molecular abundances can be driven out of equilibrium by zonal winds. Here we report a phase-resolved emission spectrum of the hot Jupiter WASP-43b measured from 5-12 μm with JWST's Mid-Infrared Instrument (MIRI). The spectra reveal a large day-night temperature contrast (with average brightness temperatures of 1524±35 and 863±23 Kelvin, respectively) and evidence for water absorption at all orbital phases. Comparisons with three-dimensional atmospheric models show that both the phase curve shape and emission spectra strongly suggest the presence of nightside clouds which become optically thick to thermal emission at pressures greater than ~100 mbar. The dayside is consistent with a cloudless atmosphere above the mid-infrared photosphere. Contrary to expectations from equilibrium chemistry but consistent with disequilibrium kinetics models, methane is not detected on the nightside (2σ upper limit of 1-6 parts per million, depending on model assumptions)
Early Release Science of the Exoplanet WASP-39b with JWST NIRSpec G395H
Measuring the abundances of carbon and oxygen in exoplanet atmospheres is
considered a crucial avenue for unlocking the formation and evolution of
exoplanetary systems. Access to an exoplanet's chemical inventory requires
high-precision observations, often inferred from individual molecular
detections with low-resolution space-based and high-resolution ground-based
facilities. Here we report the medium-resolution (R600) transmission
spectrum of an exoplanet atmosphere between 3-5 m covering multiple
absorption features for the Saturn-mass exoplanet WASP-39b, obtained with JWST
NIRSpec G395H. Our observations achieve 1.46x photon precision, providing an
average transit depth uncertainty of 221 ppm per spectroscopic bin, and present
minimal impacts from systematic effects. We detect significant absorption from
CO (28.5) and HO (21.5), and identify SO as the
source of absorption at 4.1 m (4.8). Best-fit atmospheric models
range between 3 and 10x solar metallicity, with sub-solar to solar C/O ratios.
These results, including the detection of SO, underscore the importance of
characterising the chemistry in exoplanet atmospheres, and showcase NIRSpec
G395H as an excellent mode for time series observations over this critical
wavelength range.Comment: 44 pages, 11 figures, 3 tables. Resubmitted after revision to Natur
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