Conveners
Spin Physics: Day2-morning-1
- Asmita Mukherjee (IIT Bombay)
- Renee Fatemi (University of Kentucky)
- Martha Constantinou (Temple University)
- Sanghwa Park
Spin Physics: Day2-morning-2
- Martha Constantinou (Temple University)
- Renee Fatemi (University of Kentucky)
- Asmita Mukherjee (IIT Bombay)
- Sanghwa Park
Spin Physics: Day2-afternoon-2
- There are no conveners in this block
Spin Physics: Day3-morning-1
- There are no conveners in this block
Spin Physics: Day3-morning-2
- There are no conveners in this block
Spin Physics: Day3-afternoon-1
- Renee Fatemi (University of Kentucky)
- Sanghwa Park
Spin Physics: Day3-afternoon-2
- There are no conveners in this block
Spin Physics: Day4-morning-1
- There are no conveners in this block
We report on the first simultaneous extraction of unpolarized parton distributions and fragmentation functions from a global QCD Monte Carlo analysis of inclusive and semi-inclusive deep-inelastic scattering, Drell-Yan lepton-pair production, and single-inclusive e+e- annihilation data. We use data resampling techniques to thoroughly explore the Bayesian posterior distribution of the...
We present a new approach to performing Bayesian inference for QCD analysis of nucleon structure and hadronization, using machine learning to construct the inverse function mapping quantum correlation functions to observables. The new concept provides an alternative paradigm to the standard maximum likelihood or Bayesian posterior sampling methods. The effectiveness of the new technology is...
We present a constrained analysis of the valence transversity Parton Distribution Functions from dihadron production in semi-inclusive DIS. While usual extractions of the transversity distributions rely explicitly on the fulfilment of the Soffer bounds, our analysis releases that implicit restriction to implement further explicit constraints through the Lagrange multipliers method. The results...
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 CERN and its sea quark and gluon PDFs from leading neutron electroproduction data from HERA [1]. While that analysis provided greater constraints at small parton momentum fractions $x$, the pion's gluon PDF remains...
We present a new global QCD analysis of inclusive unpolarized and polarized DIS data, using a Monte Carlo approach to simultaneously extract both the spin-averaged and spin-dependent PDFs. We focus on the high-$x$, low-$W$ region, where effects from power corrections, such as target mass corrections (TMCs) and higher twists, are particularly important. We quantify the effects on the extracted...
Jet production is the primary signal for hard scattering of the partons inside protons, which is one of the dominant processes in proton-proton collisions at the RHIC energies. The jet double-spin asymmetries $A_{\text{LL}}$, measured at the STAR detector in polarized $pp$ collisions, remain one of the main sources of constraint for the polarized gluon parton distribution function $\Delta g$....
The Solenoidal Tracker at the Relativistic Heavy Ion Collider (STAR) experiment probes the gluon helicity distribution $\Delta G(x)$ using collisions of longitudinally polarized protons at $\sqrt{s} = $ 200 GeV and $\sqrt{s} =$ 510 GeV. Access to $\Delta G(x)$ is possible through the double spin asymmetries $A_{LL}$ in gluon-dominated hard scattering processes of inclusive jet and di-jet...
Measuring the gluon spin contribution to the proton spin has been one of the main goals of the RHIC spin program. The PHENIX experiment has extracted double longitudinal spin asymmetries which are sensitive to the gluon spin contribution at intermediate x starting at around 0.01 for central rapidity measurements and even lower for forward measurements. The latest results from the data taking...
At RHIC energies high pT direct photons are mainly produced by the quark-gluon Compton scattering process. Being not disturbed by fragmentation processes, they provide access to initial condition of partonic collisions. Direct photon production in pp collisions serves an ideal probe for gluon parton distribution functions (PDF), whereas quark PDFs are well constrained by deeply inelastic...
The virtual photon asymmetry $A_1$ is one of the fundamental quantities that provide
information on the spin structure of the nucleon. The value of A1 at high $x_{Bj}$
is of particular interest because valence quark dominate in this region, which makes
it a relatively clean region to study the nucleon spin structure. There are several
theoretical calculations that apply to the high x...
Recent experimental measurement of deeply virtual Compton scattering off the neutron by Hall A JLab collaboration [Benali et al., Nat. Phys. 16, 191 (2020)] provides welcome addition to the endeavor of determination of nucleon GPDs. This should be an important step towards both determination of elusive GPD E and flavor decomposition of DVCS amplitude. We will describe repercussions of this...
Using a recent extraction of deeply virtual Compton scattering (DVCS) Compton form factors, done within the PARTONS framework, we derive timelike Compton scattering (TCS) amplitudes and calculate TCS observables only assuming leading-twist dominance. In the framework of collinear QCD factorization, the leading-twist scattering amplitudes for DVCS and TCS are intimately related thanks to...
Ioffe time essentially quantifies the distance along the lightcone that the quark fields that enter the correlator describing the Parton Distribution Function (PDF) are separated by. In this sense, it is a natural candidate for clearly separating the short distance physics from the long distance physics. We study how the behavior of the psrton distribution in Ioffe time can be mapped out given...
We study the relative importance of double Bethe-Heitler, single Bethe-Heitler and QCD processes in the electroproduction of two photons with a large invariant mass, for both JLab and EIC kinematics.
The form factors of the energy-momentum tensor (EMT) contain a wealth of information about the nucleon. At the density level, this information can be described in terms of energy, pressure, shear forces and angular momentum distributions inside the nucleon. In this talk we present recent results on the associated 2D densities of the energy-momentum tensor in the bag model, formulated in the...
While the investigation of TMDs is a major objective of the EIC, Double Parton Ditributions (DPDs) are crucial for a first principle QCD description of double parton interactions at LHC, which contribute to the standard model background for various BSM searches. Both groups of functions are genuinely non-collinear and non-perturbative. The non-collinearity required the development of new...
We consider the transverse spectrum and the $\cos 2\phi$ azimuthal distribution of $J/\psi$ mesons produced in semi-inclusive deep-inelastic electron-proton scattering, where the electron and the proton are unpolarized. At low transverse momentum, we propose factorized expressions in terms of transverse momentum dependent gluon distributions and shape functions. We show that our formulae...
We present cross sections for the weak bosons measured by the STAR experiment at
RHIC in unpolarized proton-proton collisions at $\sqrt{s}$ = 500(510) GeV. The results combine data from run 2011, 2012, and 2013, corresponding to an integrated luminosity of 350~$pb^{-1}$. The differential $Z^{0}$ cross section measured as a function of the boson's $p_{T}$, provides important constraints on...
We present an extraction of unpolarized transverse-momentum dependent (TMD) parton distribution functions (PDFs) based on a fit on data from Drell-Yan processes in different experiments and kinematic ranges, including in particular LHC experiments. The analysis is performed in the TMD factorization framework with perturbative accuracy up to next-to-next-to-next-to-leading-log (N$^3$LL),...
I will discuss complications that arise in the factorization of hard processes differential in transverse momentum due to ambiguities in the transition from the small to large transverse momentum regions. I will relate questions about the region transition to the implementation of evolution in transverse momentum sensitive processes such as spin asymmetries. In addition, I will relate the...
COMPASS is a fixed target experiment in operation at CERN since 2002, with
a research program focused on the structure of the hadrons and spectroscopy.
An important part of this program is the study of transverse spin and momentum
dependent parton distribution and fragmentation functions. A review of recent
results on TMDs obtained by using muon beams scattering off unpolarised and...
I will discuss the cross section for the production of two unpolarized hadrons in the large transverse momentum configuration from $e^+ e^-$ annihilation, which is based on collinear fragmentation functions (FFs). Comparing with standard transverse-momentum-dependent (TMD) FF-based predictions intended for the small transverse momentum region, when the center of mass energy is not very large...
A complete understanding of the nucleon spin structure requires the knowledge of unpolarized parton distribution functions, helicity distribution functions, and the transversity distributions. Transversity, which describes the transverse spin structure of quarks in a transversely polarized proton, is the most difficult to probe and is still quite unconstrained in global analyses. It is...
We present recent results of transverse single spin asymmetries (TSSAs) for neutral pions using the Forward Meson Spectrometer at STAR at center of mass energies of 200 and 500 GeV in proton-proton collisions. Combining the results from the two energies shows that the pion TSSA increases monotonically with Feynman-x. Comparisons with previous measurements show that the pion TSSA is mostly...
We present a new extraction of unidentified charged hadron collinear fragmentation functions (ffs) using a multi-step Monte Carlo analysis. The extraction utilizes available charged hadron data from e+/e- and SIDIS experiments including the most recent results from COMPASS.
The analysis of single transverse-spin asymmetries (SSAs) gives us tremendous insight into the internal structure of hadrons. For example, the Sivers and Collins effects in semi-inclusive deep-inelastic scattering (SIDIS), Sivers effect in Drell-Yan, and the Collins effect in electron-positron annihilation have been widely investigated over many years in order to perform 3D momentum-space...
Transverse spin phenomena have challenged our understanding of the structure of the nucleon and the strong interaction in many ways. The single transverse spin asymmetries that were measured at RHIC continue to challenge us as the contributions from initial and final state effects as well as the contributions from various flavors are not well understood. The PHENIX experiment has contributed...
We perform a systematic study on the twist-3 gluon distribution and fragmentation
functions which appear in the collinear twist-3 factorization for hard inclusive
processes. Three types of twist-3 distribution and fragmentation functions,
i.e., intrinsic, kinematical and dynamical ones, which are necessary to describe
all kinds of twist-3 cross sections, are related to each other by...
Through the 21st and 22nd International Workshop on Deep Inelastic Scattering, a possibility of the non-perturbative contribution for the non-zero transverse single spin asymmetry of forward $\pi^{0}$ ($2 < \eta < 4$) was brought up. Bigger asymmetry was observed with more isolated final state which was connected with the non-perturbative event topology. Since the non-perturbative contribution...
We present our recent results on the QCD evolution of the Jaffe-Manohar orbital angular momentum distributions. We discuss both $Q^2$ evolution and small-$x$ evolution.
Deep Inelastic Scattering (DIS) and especially Semi-Inclusive Deep Inelastic Scattering (SIDIS) are leading processes in the study of hadron structure. The theoretical treatments of these processes involve approximations which only hold true in specific regions of kinematics, each region corresponding to a different physical picture. Ratios have been defined to be representative of terms which...
We study the semi-inclusive production of hard, isolated photons in unpolarized and polarized lepton-proton collisions, i.e., $\ell p\to \ell\gamma X$. We analyze the transverse nucleon single-spin asymmetry within the collinear twist-3 formalism in perturbative QCD to leading order accuracy (LO). We find that this spin asymmetry is generated by twist-3 dynamical quark-gluon-quark ($qgq$)...
The main focus of this talk is our recent work [1] on transverse single spin asymmetry (SSA) in semi-inclusive DIS in a collinear twist-3 framework. I will explicitly demonstrate that a genuinely new contribution containing the $g_T$ distribution function (alongside the kinematical and the dynamical Qiu-Sterman functions) is first seen at two loops. The phase required for a non-zero SSA from...
While significant steps toward the formal definition of quark TMDs and their extraction from experimental data through global fits has been made in the last years, the gluon-TMD field represents a largely unexplored territory. Pursuing the goal of extending our knowledge of this sector, we present analytic expressions for all $T$-even gluon TMDs at twist-2, calculated in a spectator model for...
Our understanding of the origin of the nucleon spin remains incomplete. Determining the partonic orbital angular momentum (OAM) contributions is particularly challenging experimentally. One possible signature for the partonic OAM would be detection of a non-zero Sivers effect, which characterizes the correlation between the transverse momentum of a parton ($\vec k_T$) and the transverse spin...
Sivers function is a fundamental TMD which allows to investigate the 3D structure of polarized nucleons. We present a recent extraction of this function from azimuthal asymmetries in semi-inclusive DIS. This study includes for the first time TMD evolution contributions and a parametrization of unpolarized TMDs determined directly from data. Through this analysis we can obtain a tomography of...
In this talk, I will introduce our study on the probing transverse momentum dependent gluon Sivers function in open charm and charm jets production at the future EIC. We derive the theoretical framework to calculate heavy-quark pair and heavy jet pair production in the small transverse momentum region. Based on the factorization and resummation formula, we resum large logarithms in the small...
We will present results on the nucleon spin decomposition and the momentum distribution among quarks in the nucleon. Techniques for lattice QCD simulations at the physical pion mass applied for the computation of sea-quark and gluon contributions will be presented. We will discuss several challenges and perspectives for future developments.
