3 research outputs found
Flavoured jets with exact anti- kinematics and tests of infrared and collinear safety
We propose extensions of the anti- and Cambridge/Aachen hierarchical jet
clustering algorithms that are designed to retain the exact jet kinematics of
these algorithms, while providing an infrared-and-collinear-safe definition of
jet flavour at any fixed order in perturbation theory. Central to our approach
is a new technique called Interleaved Flavour Neutralisation (IFN), whereby the
treatment of flavour is integrated with, but distinct from, the kinematic
clustering. IFN allows flavour information to be meaningfully accessed at each
stage of the clustering sequence, which enables a consistent assignment of
flavour both to individual jets and to their substructure. We validate the IFN
approach using a dedicated framework for fixed-order tests of infrared and
collinear safety, which also reveals unanticipated issues in earlier approaches
to flavoured jet clustering. We briefly explore the phenomenological impact of
IFN with anti- jets for benchmark tasks at the Large Hadron Collider.Comment: 36 pages, 27 figures, 1 table, code available from
https://github.com/jetflav/IFNPlugi
Leveraging universality of jet taggers through transfer learning
A significant challenge in the tagging of boosted objects via
machine-learning technology is the prohibitive computational cost associated
with training sophisticated models. Nevertheless, the universality of QCD
suggests that a large amount of the information learnt in the training is
common to different physical signals and experimental setups. In this article,
we explore the use of transfer learning techniques to develop fast and
data-efficient jet taggers that leverage such universality. We consider the
graph neural networks LundNet and ParticleNet, and introduce two prescriptions
to transfer an existing tagger into a new signal based either on fine-tuning
all the weights of a model or alternatively on freezing a fraction of them. In
the case of -boson and top-quark tagging, we find that one can obtain
reliable taggers using an order of magnitude less data with a corresponding
speed-up of the training process. Moreover, while keeping the size of the
training data set fixed, we observe a speed-up of the training by up to a
factor of three. This offers a promising avenue to facilitate the use of such
tools in collider physics experiments.Comment: 10 pages, 2 tables, 5 figure
Synthesis and Biotransformation of Bicyclic Unsaturated Lactones with Three or Four Methyl Groups
The aim of this study was to obtain new unsaturated lactones by chemical synthesis and their microbial transformations using fungal strains. Some of these strains were able to transform unsaturated lactones into different hydroxy or epoxy derivatives. Strains of Syncephalastrum racemosum and Absidia cylindrospora gave products with a hydroxy group introduced into a tertiary carbon, while the Penicillium vermiculatum strain hydroxylated primary carbons. The Syncephalastrum racemosum strain hydroxylated both substrates in an allylic position. Using the Absidia cylindrospora and Penicillium vermiculatum strains led to the obtained epoxylactones. The structures of all lactones were established on the basis of spectroscopic data