2,407 research outputs found
form factors with 2+1 flavors
Using the MILC 2+1 flavor asqtad quark action ensembles, we are calculating
the form factors and for the semileptonic decay. A total of six ensembles with lattice spacing from
to 0.06 fm are being used. At the coarsest and finest lattice
spacings, the light quark mass is one-tenth the strange quark mass
. At the intermediate lattice spacing, the ratio ranges from
0.05 to 0.2. The valence quark is treated using the Sheikholeslami-Wohlert
Wilson-clover action with the Fermilab interpretation. The other valence quarks
use the asqtad action. When combined with (future) measurements from the LHCb
and Belle II experiments, these calculations will provide an alternate
determination of the CKM matrix element .Comment: 8 pages, 6 figures, to appear in the Proceedings of Lattice 2017,
June 18-24, Granada, Spai
decay form factors from three-flavor lattice QCD
We compute the form factors for the semileptonic decay
process in lattice QCD using gauge-field ensembles with 2+1 flavors of sea
quark, generated by the MILC Collaboration. The ensembles span lattice spacings
from 0.12 to 0.045 fm and have multiple sea-quark masses to help control the
chiral extrapolation. The asqtad improved staggered action is used for the
light valence and sea quarks, and the clover action with the Fermilab
interpretation is used for the heavy quark. We present results for the form
factors , , and , where is the momentum
transfer, together with a comprehensive examination of systematic errors.
Lattice QCD determines the form factors for a limited range of , and we
use the model-independent expansion to cover the whole kinematically
allowed range. We present our final form-factor results as coefficients of the
expansion and the correlations between them, where the errors on the
coefficients include statistical and all systematic uncertainties. We use this
complete description of the form factors to test QCD predictions of the form
factors at high and low . We also compare a Standard-Model calculation of
the branching ratio for with experimental data.Comment: V2: Fig.7 added. Typos text corrected. Reference added. Version
published in Phys. Rev.
form factors for new-physics searches from lattice QCD
The rare decay arises from flavor-changing
neutral currents and could be sensitive to physics beyond the Standard Model.
Here, we present the first - QCD calculation of the
tensor form factor . Together with the vector and scalar form factors
and from our companion work [J. A. Bailey , Phys. Rev. D
92, 014024 (2015)], these parameterize the hadronic contribution to
semileptonic decays in any extension of the Standard Model. We obtain the total
branching ratio in
the Standard Model, which is the most precise theoretical determination to
date, and agrees with the recent measurement from the LHCb experiment [R. Aaij
, JHEP 1212, 125 (2012)]. Note added: after this paper was submitted
for publication, LHCb announced a new measurement of the differential decay
rate for this process [T. Tekampe, talk at DPF 2015], which we now compare to
the shape and normalization of the Standard-Model prediction.Comment: V3: Corrected errors in results for Standard-Model differential and
total decay rates in abstract, Fig. 3, Table IV, and outlook. Added new
preliminary LHCb data to Fig. 3 and brief discussion after outlook. Replaced
outdated correlation matrix in Table III with correct final version. Other
minor wording changes and references added. 7 pages, 4 tables, 3 figure
Cosmological Perturbations in a Big Crunch/Big Bang Space-time
A prescription is developed for matching general relativistic perturbations
across singularities of the type encountered in the ekpyrotic and cyclic
scenarios i.e. a collision between orbifold planes. We show that there exists a
gauge in which the evolution of perturbations is locally identical to that in a
model space-time (compactified Milne mod Z_2) where the matching of modes
across the singularity can be treated using a prescription previously
introduced by two of us. Using this approach, we show that long wavelength,
scale-invariant, growing-mode perturbations in the incoming state pass through
the collision and become scale-invariant growing-mode perturbations in the
expanding hot big bang phase.Comment: 47 pages, 4 figure
Recon 2.2: from reconstruction to model of human metabolism.
IntroductionThe human genome-scale metabolic reconstruction details all known metabolic reactions occurring in humans, and thereby holds substantial promise for studying complex diseases and phenotypes. Capturing the whole human metabolic reconstruction is an on-going task and since the last community effort generated a consensus reconstruction, several updates have been developed.ObjectivesWe report a new consensus version, Recon 2.2, which integrates various alternative versions with significant additional updates. In addition to re-establishing a consensus reconstruction, further key objectives included providing more comprehensive annotation of metabolites and genes, ensuring full mass and charge balance in all reactions, and developing a model that correctly predicts ATP production on a range of carbon sources.MethodsRecon 2.2 has been developed through a combination of manual curation and automated error checking. Specific and significant manual updates include a respecification of fatty acid metabolism, oxidative phosphorylation and a coupling of the electron transport chain to ATP synthase activity. All metabolites have definitive chemical formulae and charges specified, and these are used to ensure full mass and charge reaction balancing through an automated linear programming approach. Additionally, improved integration with transcriptomics and proteomics data has been facilitated with the updated curation of relationships between genes, proteins and reactions.ResultsRecon 2.2 now represents the most predictive model of human metabolism to date as demonstrated here. Extensive manual curation has increased the reconstruction size to 5324 metabolites, 7785 reactions and 1675 associated genes, which now are mapped to a single standard. The focus upon mass and charge balancing of all reactions, along with better representation of energy generation, has produced a flux model that correctly predicts ATP yield on different carbon sources.ConclusionThrough these updates we have achieved the most complete and best annotated consensus human metabolic reconstruction available, thereby increasing the ability of this resource to provide novel insights into normal and disease states in human. The model is freely available from the Biomodels database (http://identifiers.org/biomodels.db/MODEL1603150001)
Predictors of Nodal and Metastatic Failure in Early Stage Non-Small Cell Lung Cancer after Stereotactic Body Radiation Therapy
Introduction/Background
Many early-stage non-small cell lung cancer (ES-NSCLC) patients undergoing stereotactic body radiation therapy (SBRT) develop metastases, which is associated with poor outcomes. We sought to identify factors predictive of metastases after lung SBRT and created a risk stratification tool.
Materials and Methods
We included 363 patients with ES-NSCLC who received SBRT; median follow-up was 5.8 years. The following patient and tumor factors were retrospectively analyzed for their association with metastases (defined as nodal and/or distant failure): sex; age; lobe involved; centrality; previous NSCLC; smoking status; gross tumor volume (GTV); T-stage; histology; dose; minimum, maximum, and mean GTV dose; and parenchymal lung failure. A metastasis risk-score linear-model using beta coefficients from a multivariate Cox model was built.
Results
A total of 111/406 (27.3%) lesions metastasized. GTV volume and dose were significantly associated with metastases on univariate and multivariate Cox proportional hazards modeling (p<0.001 and HR=1.02 per mL, p<0.05 and HR=0.99 per Gy, respectively). Histology, T-stage, centrality, lung parenchymal failures, and previous NSCLC were not associated with development of metastasis. A metastasis risk-score model using GTV volume and prescription dose was built: [risk score=(0.01611 x GTV)–(0.00525 x dose (BED10))]. Two risk-score cutoffs separating the cohort into low-, medium-, and high-risk subgroups were examined. The risk-score identified significant differences in time to metastases between low-, medium-, and high-risk patients (p<0.001), with 3-year estimates of 81.1%, 63.8%, and 38%, respectively.
Conclusion
GTV volume and radiation dose are associated with time to metastasis and may be used to identify patients at higher risk of metastasis after lung SBRT
Strong-isospin-breaking correction to the muon anomalous magnetic moment from lattice QCD at the physical point
All lattice-QCD calculations of the hadronic-vacuum-polarization contribution to the muon's anomalous magnetic moment to-date have been performed with degenerate up- and down-quark masses. Here we calculate directly the strong-isospin-breaking correction to for the first time with physical values of and and dynamical , , , and quarks, thereby removing this important source of systematic uncertainty. We obtain a relative shift to be applied to lattice-QCD results obtained with degenerate light-quark masses of = +1.5(4)\%, in agreement with estimates from phenomenology and a recent lattice-QCD calculation with unphysically heavy pions
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