Dr. Fatma Aslan, Jefferson National Laboratory and UConn

Hadron structure-oriented approach to TMD phenomenology

We present a first practical implementation of a recently proposed hadron structure oriented (HSO) approach to TMD phenomenology applied to Drell-Yan like processes. We compare and contrast general features of our methodology with other common practices and emphasize the improvements derived from our approach that we view as essential for applications where extracting details of nonperturbative transverse hadron structure is a major goal. These include the HSO’s preservation of a basic TMD parton-model-like framework even while accounting for full TMD factorization and evolution, explicit preservation of the integral relationship between TMD and collinear PDFs, and the ability to meaningfully compare different theoretical models of nonperturbative TMD parton distributions.

Dr. Yossathorn Tawabutr, University of Jyväskylä

Fully Consistent NLO Calculation of Forward Single-Inclusive Hadron Production in Proton-Nucleus Collisions

We study the single-inclusive particle production from proton-nucleus collisions in the dilute-dense framework of the color glass condensate (CGC) at next-to-leading order (NLO) accuracy. In this regime, the cross section factorizes into hard impact factors and dipole-target scattering amplitude describing the eikonal interaction of the partons in the target color field. For the first time, we combine the NLO impact factors with the dipole amplitude evolved consistently using the NLO Balitsky-Kovchegov (BK) equation with the initial conditions fitted to HERA structure function data.

The resulting neutral pion cross section with all parton channels included are qualitatively consistent with the recent LHCb measurement. In particular, the NLO evolution coupled to the leading order impact factor is shown to produce a large Cronin peak that is not visible in the data, demonstrating the importance of consistently including NLO corrections to all the ingredients. Furthermore, the transverse momentum spectrum is found to be sensitive to the resummation scheme and the running coupling prescription in the BK evolution. This demonstrates how additional constraints for the initial condition of the BK evolution can be obtained from global analyses including both the HERA and LHC data. In light of the upcoming upgrades to the LHC, the dependence of our results on rapidity will also be discussed.

Prof. Lance Dixon, Stanford University

The DNA of Particle Scattering

Scattering amplitudes are the arena where quantum field theory meets particle experiments, for example at the Large Hadron Collider where the copious scattering of quarks and gluons in quantum chromodynamics (QCD) produces Higgs bosons and many backgrounds to searches for new physics. Particle scattering in QCD and other gauge theories is far simpler than standard perturbative approaches would suggest. Modern approaches based on unitarity and bootstrapping dramatically simplify many computations previously done with Feynman diagrams. Even so, the final results are often highly intricate, multivariate mathematical functions, which are difficult to describe, let alone compute. In many cases, the functions have a “genetic code” underlying them, called the symbol, which reveals much of their structure. The symbol is a linear combination of words, sequences of letters analogous to sequences of DNA base pairs. Understanding the alphabet, and then reading the code, exposes the physics and mathematics underlying the scattering process, including new symmetries. For example, the two scattering amplitudes that are known to the highest orders in perturbation theory (8 loops) are related to each other by a mysterious antipodal duality, which involves reading the code backwards as well as forwards. A third scattering amplitude, which contains both of these as limits, has an antipodal self-duality which “explains” the other duality. However, we still don’t know `who ordered’ antipodal (self-)duality, or what it really means.

Daniel Norman, Department of Physics, University of Connecticut

The Complex Analytic Properties of Bandwidth Limited Signals and their Application to Conformal Cosmology and Signal Processing

Conformal gravity is an alternative theory of gravity derived from the conformally invariant Weyl squared action as opposed to the standard Einstein-Hilbert action. The general equations of conformal gravity were applied to the cosmological scale to create a theory of Conformal Cosmology where the geometry of space-time is described by first order fluctuations on a conformal-to-flat background of constant negative curvature. The differential equations of this cosmological model have solutions in terms of Legendre functions with complex degree and order. In order to calculate the multipole expansion of Cosmic Background Radiation (CMB) anisotropy within this model, it is necessary to integrate the Legendre function solutions with respect to their complex degree. An analytic method for solving this integration problem was developed which makes use of the fact that the Legendre functions are Bandwidth Limit Signals (BLS’s) which are functions with a finite domain in frequency space. A general analysis of the properties of BLS’s in the complex plane was done which has yielded new theorems and expansion formulas applicable to all BLS’s as well as to other related families of complex functions. These results have both specific applications to Conformal Cosmology as well as broader applications to the field of signal processing. The methods of complex integration developed in this work, initially for the purpose of computing the CMB anisotropy in Conformal Cosmology, have been used to provide a novel solution to the infamous Borweinn integral as well as a novel proof of the Nyquist-Shannon sampling theorem.

Provakar Datta, Department of Physics, University of Connecticut

Probing the Neutron’s Internal Structure via High-Q2 Electromagnetic Form Factor Measurements

The electromagnetic form factors (EMFFs) are among the most basic observables sensitive to the nucleon’s internal structure. Knowing their values with high precision in a wide range of squared four-momentum transfer (Q2) is essential for the advancement of QCD. The high Q ² precision data of the nucleon EMFFs are scarce due to the challenges associated with such measurements. However, the Super BigBite Spectrometer (SBS) collaboration is currently running multiple experiments in Jefferson Lab’s experimental Hall A to precisely measure the proton and neutron EMFFs with unprecedented Q ² reach, which will vastly improve the situation. In this talk, I will give an overview of the SBS high Q ² program with a focus on the SBS-GMn experiment. SBSGMn, the very first SBS experiment, was completed during Oct. 2021 - Feb. 2022 running period to measure the neutron magnetic form factor (GnM) up to Q ² = 13.6 (GeV/c) ² using “ratio” method. I will briefly discuss the underlying theory, measurement technique, associated technical challenges, and present our progress of physics analysis including preliminary data/MC comparisons. I will also show realistic projections of the final uncertainties on GnM, emphasizing the high-Q ² data points.

Shaswat Tiwari, NCSU 

Entanglement measures in scattering and the S-matrix Bootstrap

Quantum information theory has been instrumental in offering new
insights into old physics problems. In this talk, I shall use it to
study 2-2 scattering in quantum field theories[1], defining the
Entanglement entropy and the relative entropy in this setting. I will
evaluate these measures for theories like φ4, chiral perturbation
theory ( χP T ), etc. Using known bounds on the differential elastic
cross section, I will argue a general bound on relative entropy at
high energy. I will also find definite sign properties of relative
entropy that shall help constrain the S-matrix Bootstrap. Reviving the
old 1960s effort to study Quantum field theory using S-matrices, the
S-matrix bootstrap is a recent attempt to study S-matrices
numerically. I will briefly describe the bootstrap methods and how
relative entropy becomes helpful in this study. These constraints help
isolate S-matrices, which have leading Regge trajectory compatible
with experiments[2].


[1] A. Bose, P. Haldar, A. Sinha, P. Sinha, and S. S. Tiwari,
“Relative entropy in scattering and the
S-matrix bootstrap,” SciPost Phys. 9, 081 (2020),arXiv:2006.12213 [hep-th]

[2]A. Bose, A. Sinha, and S. S. Tiwari, “Selection rules for the
S-Matrix bootstrap,” SciPost Phys. 10, 122 (2021),arXiv:2011.07944
[hep-th].

Prof. P. Mannheim, Department of Physics, University of Connecticut

Normalization of the vacuum and the ultraviolet completion of Einstein gravity

Second-order-derivative plus fourth-order-derivative gravity is the ultraviolet completion of second-order-derivative quantum Einstein gravity. While it achieves renormalizability through states of negative Dirac norm, the unitarity violation that this would entail can be postponed to Planck energies. As we show in this paper the theory has a different problem, one that occurs at all energy scales, namely that the Dirac norm of the vacuum of the theory is not finite. To establish this we present a procedure for determining the norm of the vacuum in any quantum field theory. With the Dirac norm of the vacuum of the second-order-derivative plus fourth-order-derivative theory not being finite, the Feynman rules that are used to establish renormalizability are not valid, as is the assumption that the theory can be used as an effective theory at energies well below the Planck scale. This lack of finiteness is also manifested in the fact that the Minkowski path integral for the theory is divergent. Because the vacuum Dirac norm is not finite, the Hamiltonian of the theory is not Hermitian. However, it turns out to be PT-symmetric. And when one continues the theory into the complex plane and uses the PT-symmetry inner product, viz. the overlap of the left-eigenstate of the Hamiltonian with its right-eigenstate, one then finds that for the vacuum this norm is both finite and positive, the Feynman rules now are valid, the Minkowski path integral now is well behaved, and the theory now can serve as a low energy effective theory. Consequently, the theory can now be offered as a fully consistent, unitary, and renormalizable theory of quantum gravity.

Prof. Michael Lublinsky, Department of Physics, Ben-Gurion University

Magnetic monopole in chiral plasma

Chiral anomaly induces qualitatively new transport phenomena in finite temperature plasma of massless fermions. In the first part of the talk, we will explore the effect of a magnetic monopole inserted into chiral plasma. Next, we will present various novel anomaly induced phenomena discovered in a holographically defined model.

Fatma Aslan, University of Connecticut Basics of factorization in a scalar Yukawa field theory The factorization theorems of QCD apply equally well to most simple quantum field theories that require renormalization but where direct calculations are much more straightforward. Working with these simpler theories is convenient for stress testing the limits of the factorization program and for examining general properties of the parton density functions or other correlation functions that might be necessary for a factorized description of a process. With this view in mind, we review the steps of factorization in a real scalar Yukawa field theory for both deep inelastic scattering and semi-inclusive deep inelastic scattering cross sections. In the case of semi-inclusive deep inelastic scattering, we illustrate how to separate the small transverse momentum region, where transverse momentum-dependent parton density functions are needed, from a purely collinear large transverse momentum region, and we examine the influence of subleading power corrections. We also review the steps for formulating transverse momentum-dependent factorization in transverse coordinate space, and we study the effect of transforming to the well-known scheme. Within the Yukawa theory, we investigate the consequences of switching to a generalized parton model approach and compare it with a fully factorized approach. Our results highlight the need to address similar or analogous issues in QCD.

Dr. Nobuyuki Matsumoto, Brookhaven National Lab Possible use of trivializing maps as a coarse-graining map In lattice calculation of quantum field theory, we encounter the infamous critical slowing down when approaching the continuum limit. Luscher in 2009 proposed to use a trivializing map in numerical simulations that map a gauge theory to its strong coupling limit. As the gauge configurations can be generated efficiently in the strong coupling, this method can potentially resolve the critical slowing down. However, the original algorithm was tested and asserted to have a fair amount of overhead eliminating the gain [Engel-Schaefer 2011]. This work considers how we can redesign the map so that one overcomes this practical difficulty. In this talk, I report an exploratory effort to use local trivializing maps as a coarse-graining map. The coarse-graining map allows us to use the effective action we obtain after integrating local degrees of freedom. The method is applied to a toy model of 2D U(1) pure gauge theory, for which we can see the gain at least in the unit of Monte Carlo steps.