10,386 research outputs found
On Glauber modes in Soft-Collinear Effective Theory
Gluon interactions involving spectator partons in collisions at hadronic
machines are investigated. We find a class of examples in which a mode, called
Glauber gluons, must be introduced to the effective theory for consistency.Comment: 19 pages, three figures. Uses JHEP3.cl
Non-global Structure of the O({\alpha}_s^2) Dijet Soft Function
High energy scattering processes involving jets generically involve matrix
elements of light- like Wilson lines, known as soft functions. These describe
the structure of soft contributions to observables and encode color and
kinematic correlations between jets. We compute the dijet soft function to
O({\alpha}_s^2) as a function of the two jet invariant masses, focusing on
terms not determined by its renormalization group evolution that have a
non-separable dependence on these masses. Our results include non-global single
and double logarithms, and analytic results for the full set of non-logarithmic
contributions as well. Using a recent result for the thrust constant, we
present the complete O({\alpha}_s^2) soft function for dijet production in both
position and momentum space.Comment: 55 pages, 8 figures. v2: extended discussion of double logs in the
hard regime. v3: minor typos corrected, version published in JHEP. v4: typos
in Eq. (3.33), (3.39), (3.43) corrected; this does not affect the main
result, numerical results, or conclusion
Resonances in an external field: the 1+1 dimensional case
Using non-relativistic effective field theory in 1+1 dimensions, we
generalize Luescher's approach for resonances in the presence of an external
field. This generalized approach provides a framework to study the
infinite-volume limit of the form factor of a resonance determined in lattice
simulations.Comment: 13 pages, 2 postscript figure
Observations of Reduced Electron Gyroscale Fluctuations in National Spherical Torus Experiment H-Mode Plasmas with Large E X B Flow Shear
Electron gyroscale fluctuation measurements in National Spherical Torus Experiment H-mode plasmas with large toroidal rotation reveal fluctuations consistent with electron temperature gradient (ETG) turbulence. Large toroidal rotation in National Spherical Torus Experiment plasmas with neutral beam injection generates ExB flow shear rates comparable to ETG linear growth rates. Enhanced fluctuations occur when the electron temperature gradient is marginally stable with respect to the ETG linear critical gradient. Fluctuation amplitudes decrease when the ExB flow shear rate exceeds ETG linear growth rates. The observations indicate that ExB flow shear can be an effective suppression mechanism for ETG turbulence.X1129sciescopu
The Quark Beam Function at NNLL
In hard collisions at a hadron collider the most appropriate description of
the initial state depends on what is measured in the final state. Parton
distribution functions (PDFs) evolved to the hard collision scale Q are
appropriate for inclusive observables, but not for measurements with a specific
number of hard jets, leptons, and photons. Here the incoming protons are probed
and lose their identity to an incoming jet at a scale \mu_B << Q, and the
initial state is described by universal beam functions. We discuss the
field-theoretic treatment of beam functions, and show that the beam function
has the same RG evolution as the jet function to all orders in perturbation
theory. In contrast to PDF evolution, the beam function evolution does not mix
quarks and gluons and changes the virtuality of the colliding parton at fixed
momentum fraction. At \mu_B, the incoming jet can be described perturbatively,
and we give a detailed derivation of the one-loop matching of the quark beam
function onto quark and gluon PDFs. We compute the associated NLO Wilson
coefficients and explicitly verify the cancellation of IR singularities. As an
application, we give an expression for the next-to-next-to-leading logarithmic
order (NNLL) resummed Drell-Yan beam thrust cross section.Comment: 54 pages, 9 figures; v2: notation simplified in a few places, typos
fixed; v3: journal versio
Association between treatment with apixaban, dabigatran, rivaroxaban, or warfarin and the risk of osteoporotic fractures among patients with atrial fibrillation: A population-based cohort study
Background:
It is unclear whether anticoagulant type is associated with the risk for osteoporotic fracture, a deleterious complication of anticoagulants among patients with atrial fibrillation (AF).
Objective:
To compare the risk for osteoporotic fracture between anticoagulants.
Design:
Population-based cohort study.
Setting:
Territory-wide electronic health record database of the Hong Kong Hospital Authority.
Participants:
Patients newly diagnosed with AF between 2010 and 2017 who received a new prescription for warfarin or a direct oral anticoagulant (DOAC) (apixaban, dabigatran, or rivaroxaban). Follow-up ended on 31 December 2018.
Measurements:
Osteoporotic hip and vertebral fractures in anticoagulant users were compared using propensity score–weighted cumulative incidence differences (CIDs).
Results:
There were 23 515 patients identified (3241 apixaban users, 6867 dabigatran users, 3866 rivaroxaban users, and 9541 warfarin users). Overall mean age was 74.4 years (SD, 10.8), ranging from 73.1 years (warfarin) to 77.9 years (apixaban). Over a median follow-up of 423 days, 401 fractures were identified (crude event number [weighted rate per 100 patient-years]: apixaban, 53 [0.82]; dabigatran, 95 [0.76]; rivaroxaban, 57 [0.67]; and warfarin, 196 [1.11]). After 24-month follow-up, DOAC use was associated with a lower risk for fracture than warfarin use (apixaban CID, −0.88% [95% CI, −1.66% to −0.21%]; dabigatran CID, −0.81% [CI, −1.34% to −0.23%]; and rivaroxaban CID, −1.13% [CI, −1.67% to −0.53%]). No differences were seen in all head-to-head comparisons between DOACs at 24 months (apixaban vs. dabigatran CID, −0.06% [CI, −0.69% to 0.49%]; rivaroxaban vs. dabigatran CID, −0.32% [CI, −0.84% to 0.18%]; and rivaroxaban vs. apixaban CID, −0.25% [CI, −0.86% to 0.40%]).
Limitation:
Residual confounding is possible.
Conclusion:
Among patients with AF, DOAC use may result in a lower risk for osteoporotic fracture compared with warfarin use. Fracture risk does not seem to be altered by the choice of DOAC. These findings may help inform the benefit–risk assessment when choosing between anticoagulants.
Primary Funding Source:
The University of Hong Kong and University College London Strategic Partnership Fund
Jet Shapes and Jet Algorithms in SCET
Jet shapes are weighted sums over the four-momenta of the constituents of a
jet and reveal details of its internal structure, potentially allowing
discrimination of its partonic origin. In this work we make predictions for
quark and gluon jet shape distributions in N-jet final states in e+e-
collisions, defined with a cone or recombination algorithm, where we measure
some jet shape observable on a subset of these jets. Using the framework of
Soft-Collinear Effective Theory, we prove a factorization theorem for jet shape
distributions and demonstrate the consistent renormalization-group running of
the functions in the factorization theorem for any number of measured and
unmeasured jets, any number of quark and gluon jets, and any angular size R of
the jets, as long as R is much smaller than the angular separation between
jets. We calculate the jet and soft functions for angularity jet shapes \tau_a
to one-loop order (O(alpha_s)) and resum a subset of the large logarithms of
\tau_a needed for next-to-leading logarithmic (NLL) accuracy for both cone and
kT-type jets. We compare our predictions for the resummed \tau_a distribution
of a quark or a gluon jet produced in a 3-jet final state in e+e- annihilation
to the output of a Monte Carlo event generator and find that the dependence on
a and R is very similar.Comment: 62 pages plus 21 pages of Appendices, 13 figures, uses JHEP3.cls. v2:
corrections to finite parts of NLO jet functions, minor changes to plots,
clarified discussion of power corrections. v3: Journal version. Introductory
sections significantly reorganized for clarity, classification of logarithmic
accuracy clarified, results for non-Mercedes-Benz configurations adde
Parton Fragmentation within an Identified Jet at NNLL
The fragmentation of a light parton i to a jet containing a light energetic
hadron h, where the momentum fraction of this hadron as well as the invariant
mass of the jet is measured, is described by "fragmenting jet functions". We
calculate the one-loop matching coefficients J_{ij} that relate the fragmenting
jet functions G_i^h to the standard, unpolarized fragmentation functions D_j^h
for quark and gluon jets. We perform this calculation using various IR
regulators and show explicitly how the IR divergences cancel in the matching.
We derive the relationship between the coefficients J_{ij} and the quark and
gluon jet functions. This provides a cross-check of our results. As an
application we study the process e+ e- to X pi+ on the Upsilon(4S) resonance
where we measure the momentum fraction of the pi+ and restrict to the dijet
limit by imposing a cut on thrust T. In our analysis we sum the logarithms of
tau=1-T in the cross section to next-to-next-to-leading-logarithmic accuracy
(NNLL). We find that including contributions up to NNLL (or NLO) can have a
large impact on extracting fragmentation functions from e+ e- to dijet + h.Comment: expanded introduction, typos fixed, journal versio
Internal transport barriers in the National Spherical Torus Experiment
In the National Spherical Torus Experiment [M. Ono , Nucl. Fusion 41, 1435 (2001)], internal transport barriers (ITBs) are observed in reversed (negative) shear discharges where diffusivities for electron and ion thermal channels and momentum are reduced. While neutral beam heating can produce ITBs in both electron and ion channels, high harmonic fast wave heating can also produce electron ITBs (e-ITBs) under reversed magnetic shear conditions without momentum input. Interestingly, the location of the e-ITB does not necessarily match that of the ion ITB (i-ITB). The e-ITB location correlates best with the magnetic shear minima location determined by motional Stark effect constrained equilibria, whereas the i-ITB location better correlates with the location of maximum ExB shearing rate. Measured electron temperature gradients in the e-ITB can exceed critical gradients for the onset of electron thermal gradient microinstabilities calculated by linear gyrokinetic codes. A high-k microwave scattering diagnostic shows locally reduced density fluctuations at wave numbers characteristic of electron turbulence for discharges with strongly negative magnetic shear versus weakly negative or positive magnetic shear. Reductions in fluctuation amplitude are found to be correlated with the local value of magnetic shear. These results are consistent with nonlinear gyrokinetic simulations predicting a reduction in electron turbulence under negative magnetic shear conditions despite exceeding critical gradients.X1128sciescopu
MSH2 c.1452-1455delAATG Is a Founder Mutation and an Important Cause of Hereditary Nonpolyposis Colorectal Cancer in the Southern Chinese Population
Hereditary nonpolyposis colorectal cancer (HNPCC) accounts for ∼2% of all colorectal cancer (CRC) cases and is the most common hereditary CRC syndrome. We have previously reported a high incidence of microsatellite instability (MSI) and germline mismatch repair (MMR) gene mutations in young Hong Kong Chinese with CRC. Ongoing studies at the Hereditary Gastrointestinal Cancer Registry in Hong Kong have revealed a unique germline MSH2 c.1452-1455delAATG mutation that has not been reported in other ethnic groups. Detailed analysis showed that this specific MSH2 mutation constituted 21% of all germline MMR gene mutations and 36% of all MSH2 germline mutations identified. We designed a specific PCR-based diagnostic test on paraffin-embedded tissues and identified this germline mutation in 2 1.5%) of 138 consecutive patients with early-onset CRC (93 million. Further analysis suggested that this founder mutation may date back to between 22 and 103 generations ago. The identification of this MSH2 founder mutation has important implications for the design of mutation-detection strategies for the southern Chinese population. Since there were major emigrations from Hong Kong and Guangdong province during the 19th and 20th centuries, this finding is also significant for Chinese communities worldwide.published_or_final_versio
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