289 research outputs found
First exploratory calculation of the long-distance contributions to the rare kaon decays <i>K</i> →π ℓ<sup>+</sup>ℓ<sup>-</sup>
The rare decays of a kaon into a pion and a charged lepton/antilepton pair
proceed via a flavour changing neutral current and therefore may only be
induced beyond tree level in the Standard Model. This natural suppression makes
these decays sensitive to the effects of potential New Physics. The CP
conserving decay channels however are dominated by a
single photon exchange; this involves a sizeable long-distance hadronic
contribution which represents the current major source of theoretical
uncertainty. Here we outline our methodology for the computation of the
long-distance contributions to these rare decay amplitudes using lattice QCD
and present the numerical results of the first exploratory studies of these
decays in which all but the disconnected diagrams are evaluated. The domain
wall fermion ensembles of the RBC and UKQCD collaborations are used, with a
pion mass of and a kaon mass of . In particular we determine the form factor, , of the
decay from the lattice at small values of
, obtaining for the
three values of respectively.Comment: 40 pages, 14 figures, 4 table
Universal Fluctuations of the Danube Water Level: a Link with Turbulence, Criticality and Company Growth
A global quantity, regardless of its precise nature, will often fluctuate
according to a Gaussian limit distribution. However, in highly correlated
systems, other limit distributions are possible. We have previously calculated
one such distribution and have argued that this function should apply
specifically, and in many instances, to global quantities that define a steady
state. Here we demonstrate, for the first time, the relevance of this
prediction to natural phenomena. The river level fluctuations of the Danube are
observed to obey our prediction, which immediately establishes a generic
statistical connection between turbulence, criticality and company growth
statistics.Comment: 5 pages, 1 figur
Exploratory lattice QCD study of the rare kaon decay
In Ref [1] we have presented the results of an exploratory lattice QCD
computation of the long-distance contribution to the
decay amplitude. In the present paper we describe the details of this
calculation, which includes the implementation of a number of novel techniques.
The decay amplitude is dominated by short-distance
contributions which can be computed in perturbation theory with the only
required non-perturbative input being the relatively well-known form factors of
semileptonic kaon decays. The long-distance contributions, which are the target
of this work, are expected to be of O(5%) in the branching ratio. Our study
demonstrates the feasibility of lattice QCD computations of the
decay amplitude, and in particular of the
long-distance component. Though this calculation is performed on a small
lattice () and at unphysical pion, kaon and charm quark masses,
MeV, MeV and m_c^{\overline{\mathrm{MS}}}(\mbox{2
GeV})=863 MeV, the techniques presented in this work can readily be applied to
a future realistic calculation.Comment: 74 pages, 12 figure
Structure-guided machine learning prediction of drug resistance mutations in Abelson 1 kinase.
Funder: State Government of VictoriaKinases play crucial roles in cellular signalling and biological processes with their dysregulation associated with diseases, including cancers. Kinase inhibitors, most notably those targeting ABeLson 1 (ABL1) kinase in chronic myeloid leukemia, have had a significant impact on cancer survival, yet emergence of resistance mutations can reduce their effectiveness, leading to therapeutic failure. Limited effort, however, has been devoted to developing tools to accurately identify ABL1 resistance mutations, as well as providing insights into their molecular mechanisms. Here we investigated the structural basis of ABL1 mutations modulating binding affinity of eight FDA-approved drugs. We found mutations impair affinity of type I and type II inhibitors differently and used this insight to developed a novel web-based diagnostic tool, SUSPECT-ABL, to pre-emptively predict resistance profiles and binding free-energy changes (ΔΔG) of all possible ABL1 mutations against inhibitors with different binding modes. Resistance mutations in ABL1 were successfully identified, achieving a Matthew's Correlation Coefficient of up to 0.73 and the resulting change in ligand binding affinity with a Pearson's correlation of up to 0.77, with performances consistent across non-redundant blind tests. Through an in silico saturation mutagenesis, our tool has identified possibly emerging resistance mutations, which offers opportunities for in vivo experimental validation. We believe SUSPECT-ABL will be an important tool not just for improving precision medicine efforts, but for facilitating the development of next-generation inhibitors that are less prone to resistance. We have made our tool freely available at http://biosig.unimelb.edu.au/suspect_abl/
Urokinase plasminogen activator receptor polymorphisms and airway remodelling in asthma
PLAUR polymorphisms and levels are associated with markers of airway remodelling in lung biopsies of asthma patients http://ow.ly/X5Sr
Domain wall QCD with physical quark masses
We present results for several light hadronic quantities (, ,
, , , , ) obtained from simulations of 2+1
flavor domain wall lattice QCD with large physical volumes and nearly-physical
pion masses at two lattice spacings. We perform a short, O(3)%, extrapolation
in pion mass to the physical values by combining our new data in a simultaneous
chiral/continuum `global fit' with a number of other ensembles with heavier
pion masses. We use the physical values of , and to
determine the two quark masses and the scale - all other quantities are outputs
from our simulations. We obtain results with sub-percent statistical errors and
negligible chiral and finite-volume systematics for these light hadronic
quantities, including: = 130.2(9) MeV; = 155.5(8) MeV; the
average up/down quark mass and strange quark mass in the scheme
at 3 GeV, 2.997(49) and 81.64(1.17) MeV respectively; and the neutral kaon
mixing parameter, , in the RGI scheme, 0.750(15) and the
scheme at 3 GeV, 0.530(11).Comment: 131 pages, 30 figures. Updated to match published versio
Prospects for a lattice computation of rare kaon decay amplitudes: K →π ℓ+ℓ- decays
The rare kaon decays and are
flavor changing neutral current (FCNC) processes and hence promising channels
with which to probe the limits of the standard model and to look for signs of
new physics. In this paper we demonstrate the feasibility of lattice
calculations of decay amplitudes for which long-distance
contributions are very significant. We show that the dominant finite-volume
corrections (those decreasing as powers of the volume) are negligibly small and
that, in the four-flavor theory, no new ultraviolet divergences appear as the
electromagnetic current and the effective weak Hamiltonian approach
each other. In addition, we demonstrate that one can remove the unphysical
terms which grow exponentially with the range of the integration over the time
separation between and . We will now proceed to exploratory numerical
studies with the aim of motivating further experimental measurements of these
decays. Our work extends the earlier study by Isidori, Turchetti and Martinelli
which focussed largely on the renormalization of ultraviolet divergences. In a
companion paper we discuss the evaluation of the long-distance contributions to
decays; these contributions are expected to be at the
level of a few percent for decays.Comment: Version published in Phys. Rev.
Prospects for a lattice computation of rare kaon decay amplitudes. II. K →π ν ν ¯ decays
The rare kaon decays are strongly suppressed in the
standard model and widely regarded as processes in which new phenomena, not
predicted by the standard model, may be observed. Recognizing such new
phenomena requires precise standard model prediction for the braching ratio of
with controlled uncertainty for both short-distance and
long-distance contributions. In this work we demonstrate the feasibility of
lattice QCD calculation of the long-distance contribution to rare kaon decays
with the emphasis on . Our methodology covers the
calculation of both - and -exchange diagrams. We discuss the
estimation of the power-law, finite-volume corrections and two methods to
consistently combine the long distance contribution determined by the lattice
methods outlined here with the short distance parts that can be reliably
determined using perturbation theory. It is a subsequent work of our first
methodology paper on , where the focus was made on the
-exchange diagrams.Comment: 47 pages, 5 figure
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