406 research outputs found
Unification modulo a 2-sorted Equational theory for Cipher-Decipher Block Chaining
We investigate unification problems related to the Cipher Block Chaining
(CBC) mode of encryption. We first model chaining in terms of a simple,
convergent, rewrite system over a signature with two disjoint sorts: list and
element. By interpreting a particular symbol of this signature suitably, the
rewrite system can model several practical situations of interest. An inference
procedure is presented for deciding the unification problem modulo this rewrite
system. The procedure is modular in the following sense: any given problem is
handled by a system of `list-inferences', and the set of equations thus derived
between the element-terms of the problem is then handed over to any
(`black-box') procedure which is complete for solving these element-equations.
An example of application of this unification procedure is given, as attack
detection on a Needham-Schroeder like protocol, employing the CBC encryption
mode based on the associative-commutative (AC) operator XOR. The 2-sorted
convergent rewrite system is then extended into one that fully captures a block
chaining encryption-decryption mode at an abstract level, using no AC-symbols;
and unification modulo this extended system is also shown to be decidable.Comment: 26 page
form factors from lattice QCD
We report the first lattice QCD calculation of the form factors for the
standard model tree-level decay . In combination with future
measurement, this calculation will provide an alternative exclusive
semileptonic determination of . We compare our results with previous
model calculations, make predictions for differential decay rates and branching
fractions, and predict the ratio of differential branching fractions between
and . We also present standard model
predictions for differential decay rate forward-backward asymmetries,
polarization fractions, and calculate potentially useful ratios of
form factors with those of the fictitious decay. Our lattice
simulations utilize NRQCD and HISQ light quarks on a subset of the MILC
Collaboration's asqtad gauge configurations, including two lattice
spacings and a range of light quark masses.Comment: 24 pages, 21 figures; Ver. 2 matches published versio
Form Factors and the Fragmentation Fraction Ratio
We present a lattice quantum chromodynamics determination of the scalar and
vector form factors for the decay over the full
physical range of momentum transfer. In conjunction with future experimental
data, our results will provide a new method to extract , which may
elucidate the current tension between exclusive and inclusive determinations of
this parameter. Combining the form factor results at non-zero recoil with
recent HPQCD results for the form factors, we
determine the ratios and . These results give the fragmentation
fraction ratios and ,
respectively. The fragmentation fraction ratio is an important ingredient in
experimental determinations of meson branching fractions at hadron
colliders, in particular for the rare decay . In addition to the form factor results, we make the first prediction
of the branching fraction ratio , where is an electron or muon. Current
experimental measurements of the corresponding ratio for the semileptonic
decays of mesons disagree with Standard Model expectations at the level of
nearly four standard deviations. Future experimental measurements of
may help understand this discrepancy.Comment: 21 pages, 15 figure
Summary of the 2018 CKM Working Group on Semileptonic and Leptonic b-Hadron Decays
A summary of WG II of the CKM 2018 conference on semileptonic and leptonic b-hadron decays is presented. This includes discussions on the CKM matrix element magitudes |Vub| and |Vcb|, lepton universality tests such as R(D∗) and leptonic decays. As is usual for semileptonic and leptonic decays, much discussion is devoted towards the interplay between theoretical QCD calculations and the experimental measurements
Polarization shaping for control of nonlinear propagation
We study the nonlinear optical propagation of two different classes of
space-varying polarized light beams -- radially symmetric vector beams and
Poincar\'e beams with lemon and star topologies -- in a rubidium vapour cell.
Unlike Laguerre-Gauss and other types of beams that experience modulational
instabilities, we observe that their propagation is not marked by beam breakup
while still exhibiting traits such as nonlinear confinement and self-focusing.
Our results suggest that by tailoring the spatial structure of the
polarization, the effects of nonlinear propagation can be effectively
controlled. These findings provide a novel approach to transport high-power
light beams in nonlinear media with controllable distortions to their spatial
structure and polarization properties.Comment: 5 pages, and 4 figure
Mirizzi Syndrome Type I: A Case Presentation.
Mirizzi syndrome (MS) is a rare complication of chronic cholelithiasis. The syndrome describes gallstone obstruction of Hartmann\u27s pouch or the cystic duct that extrinsically compresses the common hepatic duct, causing obstructive jaundice. In advanced cases, the gallstones may erode into the biliary tree creating a fistula, requiring prompt diagnosis and careful surgical management. We present a case of an 82-year-old female who presented with upper abdominal pain and jaundice, later diagnosed with suspected MS type I, and managed surgically. We aim to highlight MS type I because of the potential progression and damage to the bile duct, creating complications that may affect overall patient outcome
Rare decay B -> K ll form factors from lattice QCD
We calculate, for the first time using unquenched lattice QCD, form factors
for the rare decay B -> Kll in and beyond the Standard Model. Our lattice QCD
calculation utilizes a nonrelativistic QCD formulation for the b valence
quarks, the highly improved staggered quark formulation for the light valence
quarks, and employs the MILC 2+1 asqtad ensembles. The form factor results,
based on the z expansion, are valid over the full kinematic range of q^2. We
construct the ratios f0/f+ and fT/f+, which are useful in constraining new
physics and verifying effective theory form factor symmetry relations. We also
discuss the calculation of Standard Model observables.Comment: 30 pages, 23 figures; v2 adds a reference and fixes typos, results
unchanged; v3 corrects a typo, updates references, makes minor changes in
title and text, and is version published in Phys.Rev.D, results unchange
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