[Theory-seminars] Summer students' seminars next week

Carlota Andres Casas carlota at jlab.org
Fri Jul 26 14:49:41 EDT 2019


Dear all,

Next week the summer students will be giving 15 minute talks. You have below the titles and abstracts of their presentations.

Cake seminars:
Monday, July 29, 1:00PM, Room F113
Marston Copeland, "Self-energies in a relativistic chiral effective theory"
Abstract: We calculate the self-energies of the flavor SU(3) octet and decuplet baryons, using a relativistic chiral effective theory framework consistent with Lorentz and gauge invariance. The results are compared using several different regularization prescriptions, including finite-range regularization, Pauli-Villars, and dimensional regularization, which are shown to yield the same leading nonanalytic behaviors in the chiral limit, as expected in QCD. Using the same chiral effective theory, the self-energy corrections to the baryon masses can also be computed.


Luisa Velasco, "Improving the Particle Multiplicity Generator Model for the Empirically Trained Hadronic Event Regenerator"

Abstract:

Particle collision event generators are extremely useful, providing synthetic data quickly and to the user’s specifications. At present, all such event generators function via underlying theory that provides rules by which particle multiplicities and momenta are generated. To remove theory dependence, the Empirically Trained Hadronic Event Regenerator (ETHER) at Jefferson Lab implements machine learning models to be trained on experimental data.  The focus of this study is to improve the performance of the particle multiplicity generator and develop the implementation of a non-trivial conditional feature. An ensemble learning meta-algorithm is implemented to refine the model’s learning ability. The base model is altered to accept a conditional label and is trained on continuous and discrete encoded labels. We find that the model's ability to learn rare events can be augmented through ensemble training, but it struggles to learn the shifts in the underlying data distribution necessary for the successful implementation of a conditional feature. Preliminary results suggest that many more training steps are required to implement a conditional feature in the generator model.



Jake Bringewatt, "Confronting lattice parton densities with global QCD analysis"
Abstract:
Recent progress in lattice QCD simulations of parton quasi-distributions is paving the way towards the study of the
momentum dependence of PDFs from first principles. We are working on a combined global QCD analysis of inclusive deep-inelastic scattering, Drell-Yan and other high-energy scattering data with recent results from lattice calculations of the u − d PDFs in the proton. In this talk I present our initial fits for unpolarized and polarized PDFs anddiscuss how the lattice results match with phenomenological determinations of PDF parameters. I also analyze how these results may indicate which regions of parton fraction in the lattice data induce constraints on the  anti-down − anti-up PDF difference in the proton.



Cake seminars:
Wednesday, July 31st, 1:00PM, Room F113

Nina Cao, "Constraining the glue in the pion through Drell-Yan lepton-pair production"
Abstract:
Recently, a new global Monte Carlo analysis of parton distribution functions (PDFs) of the pion determined its valence quark distribution using Drell-Yan data from Fermilab and its sea quark and gluon PDFs from leading neutron electroproduction data from HERA. While that analysis provided greater constraints at small parton momentum fractions x, the pion's gluon PDF remains poorly known at large values of x. In the present study, we explore the extent to which transverse momentum (pT)-dependent Drell-Yan cross-section data can provide for greater sensitivity to the pion’s gluon PDF at large x. We present preliminary results of a combined QCD analysis of all available pT-integrated and pT-dependent pion data, which will provide the most complete imaging of the PDFs in the pion to date across all momentum fractions.

Alexandru Sturzu, "Scattering on a Finite, Minkowski 1+1D Lattice"
Abstract:

There has been recent developments to allow lattice calculations in Minkowski space-time in order to determine real-time observables. These still require the use of finite volumes, where scattering observables may not be accessed directly. Furthermore, it is not obvious how one can recover infinite-volume scattering amplitudes from finite-volume Minkowski observables. To address this issue, we introduce a physical quantity that can be accessed from finite-volume Minkowski correlates and smoothly recovers the two-particle amplitude in the infinite volume limit. We test the convergence of this idea by considering a strongly interacting 1+1D toy model.

Ben Slimmer, "Examining the Finite Volume Spectra of Coupled Channel Scattering Interactions"
Abstract:
At Jefferson Lab and other nuclear research facilities around the world, experimental groups are exploring the spectrum of composite states of fundamental particles, hadrons. These experimental efforts require robust theoretical calculations to interpret results in the scope of quantum chromodynamics (QCD), the theory governing the strong nuclear force. The only known rigorous ab-initio method to study QCD is its lattice regularization, which places it on a space-time grid of points in a finite volume. This results in discrete energy spectra of the finite volume correlation functions. In his seminal work, Lüscher derived a mapping between the finite volume spectra of a two-hadron system to the corresponding infinite volume elastic scattering amplitude, and further generalizations of the formalism now allow us to also study coupled channel scattering as well as other processes. In this study, we investigate the effect of different scattering amplitudes on the spectra; in particular, we are interested in the properties of coupled-channel scattering, like those where the a0(980) and f0(980) lie, and the associated spectra. This study presents our initial steps into understanding the photoproduction of hadronic resonances which couple to multiple strongly-coupled hadron-hadron systems.


Bluejeans connection: https://bluejeans.com/610445877

Raza, Miguel, Carlota






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