18,925 research outputs found
Nonperturbative m_X cut effects in B -> Xs l+ l- observables
Recently, it was shown that in inclusive B -> Xs l+ l- decay, an angular
decomposition provides three independent (q^2 dependent) observables. A
strategy was formulated to extract all measurable Wilson coefficients in B ->
Xs l+ l- from a few simple integrals of these observables in the low q^2
region. The experimental measurements in the low q^2 region require a cut on
the hadronic invariant mass, which introduces a dependence on nonperturbative b
quark distribution functions. The associated hadronic uncertainties could
potentially limit the sensitivity of these decays to new physics. We compute
the nonperturbative corrections to all three observables at leading and
subleading order in the power expansion in \Lambda_QCD/m_b. We find that the
subleading power corrections give sizeable corrections, of order -5% to -10%
depending on the observable and the precise value of the hadronic mass cut.
They cause a shift of order -0.05 GeV^2 to -0.1 GeV^2 in the zero of the
forward-backward asymmetry.Comment: 11 pages, 4 figures, v2: corrected typos and Eq. (25), v3: journal
versio
A full field, 3-D velocimeter for microgravity crystallization experiments
The programming and algorithms needed for implementing a full-field, 3-D velocimeter for laminar flow systems and the appropriate hardware to fully implement this ultimate system are discussed. It appears that imaging using a synched pair of video cameras and digitizer boards with synched rails for camera motion will provide a viable solution to the laminar tracking problem. The algorithms given here are simple, which should speed processing. On a heavily loaded VAXstation 3100 the particle identification can take 15 to 30 seconds, with the tracking taking less than one second. It seeems reasonable to assume that four image pairs can thus be acquired and analyzed in under one minute
Quantum Algorithms for Fermionic Quantum Field Theories
Extending previous work on scalar field theories, we develop a quantum
algorithm to compute relativistic scattering amplitudes in fermionic field
theories, exemplified by the massive Gross-Neveu model, a theory in two
spacetime dimensions with quartic interactions. The algorithm introduces new
techniques to meet the additional challenges posed by the characteristics of
fermionic fields, and its run time is polynomial in the desired precision and
the energy. Thus, it constitutes further progress towards an efficient quantum
algorithm for simulating the Standard Model of particle physics.Comment: 29 page
Subleading Shape-Function Effects and the Extraction of |V_ub|
We derive a class of formulae relating moments of B -> Xu l nu to B -> Xs
gamma in the shape function region, where m_X^2 ~ m_b Lambda_QCD. We also
derive an analogous class of formulae involving the decay B -> Xs l+ l-. These
results incorporate Lambda_QCD/m_b power corrections, but are independent of
leading and subleading hadronic shape functions. Consequently, they enable one
to determine |V_ub|/|V_tb V_ts*| to subleading order in a model-independent
way.Comment: 23 page
Quantum Algorithms for Quantum Field Theories
Quantum field theory reconciles quantum mechanics and special relativity, and
plays a central role in many areas of physics. We develop a quantum algorithm
to compute relativistic scattering probabilities in a massive quantum field
theory with quartic self-interactions (phi-fourth theory) in spacetime of four
and fewer dimensions. Its run time is polynomial in the number of particles,
their energy, and the desired precision, and applies at both weak and strong
coupling. In the strong-coupling and high-precision regimes, our quantum
algorithm achieves exponential speedup over the fastest known classical
algorithm.Comment: v2: appendix added (15 pages + 25-page appendix
Quantum Computation of Scattering in Scalar Quantum Field Theories
Quantum field theory provides the framework for the most fundamental physical theories to be confirmed experimentally, and has enabled predictions of unprecedented precision. However, calculations of physical observables often require great computational complexity and can generally be performed only when the interaction strength is weak. A full understanding of the foundations and rich consequences of quantum field theory remains an outstanding challenge. We develop a quantum algorithm to compute relativistic scattering amplitudes in massive phi-fourth theory in spacetime of four and fewer dimensions. The algorithm runs in a time that is polynomial in the number of particles, their energy, and the desired precision, and applies at both weak and strong coupling. Thus, it offers exponential speedup over existing classical methods at high precision or strong coupling
Primary Teacher Education in Malawi: Insights Into Practice and Policy: Multi-Site Teacher Education Research Project (MUSTER), Country Report Three
Teaching/Communication/Extension/Profession,
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