49 research outputs found
An Analysis of the Decay with Predictions from Heavy Quark and Chiral Symmetry
This paper considers the implications of the heavy quark and chiral
symmetries for the semi-leptonic decay . The general kinematic analysis for decays of the form {\sl
pseudoscalar meson vector meson pseudoscalar meson lepton
anti-lepton} is presented. This formalism is applied to the above exclusive
decay which allows the differential decay rate to be expressed in a form that
is ideally suited for the experimental determination of the different form
factors for the process through angular distribution measurements. Heavy quark
and chiral symmetry predictions for the form factors are presented, and the
differential decay rate is calculated in the kinematic region where chiral
perturbation theory is valid.Comment: 15 pages, uses jytex.tex and tables.tex; 3 figures not included but
available on reques
The Exact Critical Bubble Free Energy and the Effectiveness of Effective Potential Approximations
To calculate the temperature at which a first-order cosmological phase
transition occurs, one must calculate , the free energy of a critical
bubble configuration. is often approximated by the classical energy
plus an integral over the bubble of the effective potential; one must choose a
method for calculating the effective potential when . We test different
effective potential approximations at one loop. The agreement is best if one
pulls a factor of into the decay rate prefactor [where ], and takes the real part of the effective potential in the region
. We perform a similar analysis on the 1-dimensional kink.Comment: 11 pages plus 3 figures in jyTeX; CALT-68-188
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
CMB-S4---the next-generation ground-based cosmic microwave background (CMB)
experiment---is set to significantly advance the sensitivity of CMB
measurements and enhance our understanding of the origin and evolution of the
Universe, from the highest energies at the dawn of time through the growth of
structure to the present day. Among the science cases pursued with CMB-S4, the
quest for detecting primordial gravitational waves is a central driver of the
experimental design. This work details the development of a forecasting
framework that includes a power-spectrum-based semi-analytic projection tool,
targeted explicitly towards optimizing constraints on the tensor-to-scalar
ratio, , in the presence of Galactic foregrounds and gravitational lensing
of the CMB. This framework is unique in its direct use of information from the
achieved performance of current Stage 2--3 CMB experiments to robustly forecast
the science reach of upcoming CMB-polarization endeavors. The methodology
allows for rapid iteration over experimental configurations and offers a
flexible way to optimize the design of future experiments given a desired
scientific goal. To form a closed-loop process, we couple this semi-analytic
tool with map-based validation studies, which allow for the injection of
additional complexity and verification of our forecasts with several
independent analysis methods. We document multiple rounds of forecasts for
CMB-S4 using this process and the resulting establishment of the current
reference design of the primordial gravitational-wave component of the Stage-4
experiment, optimized to achieve our science goals of detecting primordial
gravitational waves for at greater than , or, in the
absence of a detection, of reaching an upper limit of at CL.Comment: 24 pages, 8 figures, 9 tables, submitted to ApJ. arXiv admin note:
text overlap with arXiv:1907.0447
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
Abstract: CMB-S4âthe next-generation ground-based cosmic microwave background (CMB) experimentâis set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the universe. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semianalytic projection tool, targeted explicitly toward optimizing constraints on the tensor-to-scalar ratio, r, in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2â3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments, given a desired scientific goal. To form a closed-loop process, we couple this semianalytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for r > 0.003 at greater than 5Ï, or in the absence of a detection, of reaching an upper limit of r < 0.001 at 95% CL
Quantum effective field theories in heavy quark physics and phase transitions in cosmology
This thesis is concerned with aspects of quantum effective field theories, effective
actions, and their applications. New spin-flavor symmetries of the strong interactions,
which arise in the limit of very large quark masses, can be incorporated into a heavy
quark effective field theory (HQEFT). A general method for deriving the effective
Lagrangian of this theory to any order in 1/m_Q (where m_Q is the heavy quark mass)
is developed; it is used to calculate terms up to order 1/m^3_Q. The renormalization of
terms in the Lagrangian to order 1/m^2_Q is performed. Such operators break these new
symmetries and consequently are important corrections to the leading-order predictions.
HQEFT can be combined with chiral perturbation theory into a heavy meson
chiral perturbation theory (HMChPT) which describes the low-momentum interactions
of hadrons containing a heavy quark with pseudo-Goldstone bosons. HMChPT
is used to investigate the semi-leptonic four-body decay of B and D mesons into final
states with at least one Goldstone boson. Such processes may be utilized to test
the above heavy quark symmetries. The remainder of this dissertation deals with the
evaluation of effective actions and their implications. A method to efficiently compute
the one-loop effective action at zero and finite temperatures is elucidated. In a first
order cosmological phase transition, the decay rate and the temperature at which it
occurs depends on the free energy of a critical bubble configuration. Since this free
energy is related to the effective action but is usually approximated with an effective
potential, the calculational method developed above is used to study the validity of
of this approximation. The corrections are found to be important for quantitative
work.</p
On the Power Dissipation of Embedded Memory Blocks Used to Implement Logic in Field-Programmable Gate Arrays
We investigate the power and energy implications of using embedded FPGA memory blocks to implement logic. Previous studies have shown that this technique provides extremely dense implementations of some types of logic circuits, however, these previous studies did not evaluate the impact on power. In this paper, we measure the effects on power and energy as a function of three architectural parameters: the number of available memory blocks, the size of the memory blocks, and the flexibility of the memory blocks. We show that although embedded memories provide area efficient implementations of many circuits, this technique results in additional power consumption. We also show that blocks containing smaller-memory arrays are more power efficient than those containing large arrays, but for most array sizes, the memory blocks should be as flexible as possible. Finally, we show that by combining physical arrays into larger logical memories, and mapping logic in such a way that some physical arrays can be disabled on each access, can reduce the power consumption penalty. The results were obtained from place and routed circuits using standard experimental physical design tools and a detailed power model. Several results were also verified through current measurements on a 0.13â ÎŒm CMOS FPGA