18 research outputs found
The Kaon Parameter in the Chiral Limit
We introduce four-point functions in the hadronic ladder resummation approach
to large QCD Green functions. We determine the relevant one to calculate
the kaon parameter in the chiral limit. This four-point function contains
both the large momenta QCD OPE and the small momenta ChPT at NLO limits,
analytically. We get . We also give the ChPT
result at NLO for the relevant four-point function to calculate outside
the chiral limit, while the leading QCD OPE is the same as the chiral limit
one.Comment: 17 page
V_us and m_s from hadronic tau decays
Recent experimental results on hadronic tau decays into strange particles by
the OPAL collaboration are employed to determine V_us and m_s from moments of
the invariant mass distribution. Our results are V_us = 0.2208+-0.0034 and
m_s(2 GeV) = 81+-22 MeV. The error on V_us is dominated by experiment, and
should be improvable in the future. Nevertheless, already now our result is
competitive to the standard extraction of V_us from K_e3 decays, and it is
compatible with unitarity.Comment: 4 pages, 1 figur
Extraction of m_s and |V_us| from Hadronic Tau Decays
We review recent work to determine the strange quark mass m_s as well as the
proposal to determine |V_{us}| using hadronic tau decay data. The recent update
of the strange spectral function by OPAL and their moments of the invariant
mass distribution are employed. Our results are |V_us|=0.2208 +- 0.0034 and m_s
(2 GeV)=81 +- 22 MeV. Our result is already competitive to the standard
extraction of |V_us| from K_e3 decays and to the new proposals to determine it.
The error on V_us is dominated by experiment and will be eventually much
improved by the B-factories hadronic tau data.
Ultimately, a simultaneous fit of both m_s and |V_us| to a set of moments of
the hadronic tau decays invariant mass distribution will provide one of the
most accurate determinations of these Standard Model parameters.Comment: Invited talk given by J.P. at TAU04, 14-17 September 2004, Nara
(Japan
Microstructural evolution and functional fatigue of a Ti–25Ta high-temperature shape memory alloy
Titanium–tantalum based alloys can demonstrate a martensitic transformation well above 100 °C, which makes them attractive for shape memory applications at elevated temperatures. In addition, they provide for good workability and contain only reasonably priced constituents. The current study presents results from functional fatigue experiments on a binary Ti–25Ta high-temperature shape memory alloy. This material shows a martensitic transformation at about 350 °C along with a transformation strain of 2 pct at a bias stress of 100 MPa. The success of most of the envisaged applications will, however, hinge on the microstructural stability under thermomechanical loading. Thus, light and electron optical microscopy as well X-ray diffraction were used to uncover the mechanisms that dominate functional degradation in different temperature regimes. It is demonstrated the maximum test temperature is the key parameter that governs functional degradation in the thermomechanical fatigue tests. Specifically, ω-phase formation and local decomposition in Ti-rich and Ta-rich areas dominate when T max does not exceed ≈430 °C. As T max is increased, the detrimental phases start to dissolve and functional fatigue can be suppressed. However, when T max reaches ≈620 °C, structural fatigue sets in, and fatigue life is again deteriorated by oxygen-induced crack formation. Copyright © Materials Research Society 201
Unquenched determination of the kaon parameter B-K from improved staggered fermions
The use of improved staggered actions (HYP, Asqtad) has been proved to reduce
the scaling corrections that affected previous calculations of B_K with
unimproved (standard) staggered fermions in the quenched approximation. This
improved behaviour allows us to perform a reliable calculation of B_K including
quark vacuum polarization effects, using the MILC configurations with n_f=2+1
flavours of sea fermions. We perform such a calculation for a single lattice
spacing, a=0.125 fm, and with kaons made up of degenerate quarks with m_s/2.
The valence strange quark mass m_s is fixed to its physical value and we use
two different values of the light sea quark masses. After a chiral
extrapolation of the results to the physical value of the sea quark masses, we
find \hat B_K = 0.83+-0.18, where the error is dominated by the uncertainty in
the lattice to continuum matching at O(\alpha_s^2). The matching will need to
be improved to get the precision needed to make full use of the experimental
data on \epsilon_K to constrain the unitarity triangle.Comment: 15 pages, 6 figure
“Embedded” at hire? Predicting the voluntary and involuntary turnover of new employees
Embeddedness theory has been invoked to describe factors that constrain employee turnover, such as fit with the environment, interpersonal links, and potentially sacrificed benefits. In contrast with previous assumptions that embeddedness requires considerable time to develop on the job, we extend theory by demonstrating how biographical characteristics (i.e., biodata), assessed at or before the point of hire, are related to individual\u27s propensity to be embedded, while also showing how such characteristics predict one\u27s future turnover likelihood. Beyond voluntary turnover, we also build embeddedness-based theoretical explanations for involuntary turnover (i.e., terminations). To test these ideas, we conducted two studies at and before employees\u27 point of hire, respectively: Study 1 examined how assessed biodata items of new employees relate to established embeddedness measures, whereas Study 2 linked the same biodata items assessed during the application process to employees\u27 future involuntary, avoidable voluntary, and unavoidable voluntary turnover. Study 1 results revealed various biodata items predicted embeddedness in two distinct samples. In Study 2, results showed that biodata predicted turnover forms in unique ways. Our study highlights the utility of point-of-hire embeddedness propensity as a means to explain organizational exit, thereby demonstrating how organizations can use embeddedness tenets for employee recruitment and selection purposes