Conveners
Spin Physics: Parallel Sessions 1
- Asmita Mukherjee (IIT Bombay)
Spin Physics
- Sanghwa Park (Stony Brook University)
Spin Physics: Parallel Sessions 3
- Martha Constantinou (Temple University)
Spin Physics: Parallel Sessions 3
- Asmita Mukherjee (IIT Bombay)
Spin Physics: Parallel Sessions 4
- Alexander Bazilevsky (BNL)
Spin Physics: Parallel Sessions 5
- Martha Constantinou (Temple University)
Spin Physics: Parallel Sessions 5
- Asmita Mukherjee (IIT Bombay)
Spin Physics
- Sanghwa Park (Stony Brook University)
We present recent results of transverse single-spin asymmetries (TSSA) for neutral pions using the Forward Meson Spectrometer at STAR at center of mass energies of 200 and 500 GeV in proton-proton collisions. The results from the two energies show that the pion TSSA increases continuously with Feynman-x. Comparisons with previous measurements show that the pion TSSA is mostly independent of...
The experimental observation of strikingly large transverse single-spin asymmetries (TSSAs) revealed that there were significant spin-momentum correlations present in hadronic collisions, both within nucleons and the process of hadronization. TSSA measurements have allowed for the development of both transverse momentum dependent and collinear twist-3 descriptions of these nonperturbative...
Understanding the transverse spin and momentum structure of the proton is of large interest to the nuclear physics community and it is one of the main goals of the spin physics program at the Relativistic Heavy Ion Collider (RHIC). Transverse single spin asymmetry measurements for charged particles produced in proton proton collisions provide keen insight into initial and final state...
Proton at high energy is a hugely complex many-body quantum system where gluons are the dominant degrees of freedom. The information of the three-dimensional structure of the proton is encoded in the transverse Momentum Dependent Parton distribution function (TMDs). Transverse Momentum Dependent Parton distribution functions (TMDs) are among the key subjects to be fully investigated at current...
We study the Sivers azimuthal asymmetry, and the role of the gluon Sivers function (GSF), in inelastic $J/\psi$ leptoproduction, $l\,p^\uparrow \to l'+ J/\psi+ X$, at small-to-moderate transverse momentum. To this end, we adopt the color-gauge invariant generalized parton model and the NRQCD framework for quarkonium formation. We compare our estimates for the unpolarized cross-section with...
Using Soft-Collinear Effective Theory, we develop the transverse-momentum-dependent factorization formalism for heavy flavor dijet production in polarized-proton-electron collisions. We consider heavy flavor mass corrections in the collinear-soft and jet functions, as well as the associated evolution equations. Using this formalism, we generate a prediction for the gluon Sivers asymmetry for...
We show that jet charge measurements can substantially enhance the sensitivity of spin asymmetries to different partonic flavors in the nucleon. As an example, we
use the Sivers asymmetry in back-to-back electron-jet production at the EIC to show that the jet charge can be a unique tool in constraining the Sivers function for different partonic flavors.
A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi-inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized protons is presented. These asymmetries include the previously published \hermes results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to...
The exploration of the transverse spin structure of the nucleon by measuring the transverse-spin-dependent azimuthal asymmetries in Drell-Yan process is one of the main topics of the phase-II research programme of the COMPASS experiment (CERN, SPS-M2 beamline).
In 2015 and 2018 the experiment performed Drell-Yan measurements using a 190 GeV $\pi^-$ beam interacting with a transversely...
We perform the global analysis of polarized Semi-Inclusive Deep Inelastic Scattering (SIDIS), pion-induced polarized Drell-Yan (DY), and W/Z boson production data and extract the Sivers function for u, d, s and for sea-quarks. We use the framework of transverse momentum dependent factorization at N3LO accuracy. The Qiu-Sterman function is determined in a model-independent way from the...
The Bayesian reweighting procedure is applied for the first time to a transverse momentum dependent distribution, the quark Sivers function extracted from Semi-Inclusive DIS (SIDIS) data. By exploting the recent published single spin asymmetry data for the inclusive jet production in $p^\uparrow p$ collisions from the STAR collaboration at RHIC, we show how such a procedure allows to...
Pseudo-data with simulated experimental errors can be generated to train an ensemble of Artificial Neural Networks (ANN) implemented on a regression to extract Transverse Momentum-dependent Distributions (TMDs). A preliminary analysis will be presented on the reliability in extraction of the Sivers function imposed in the pseudo-data given the bounds on the experimental errors, data sparsity,...
We perform explorative analyses of the 3D gluon content of the proton via a study of unpolarized and polarized gluon TMDs at twist-2, calculated in a spectator model for the parent nucleon. Our approach embodies a flexible parametrization for the spectator-mass function, suited to describe both moderate and small-$x$ effects. All these studies can serve as a useful guidance in the...
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...
The transversity distribution function, $h^{q}_{1}(x)$, a leading twist parton distribution function, is a fundamental component of the spin structure of the nucleon. $h^{q}_{1}(x)$ describes the distributions of transversely polarized quarks inside a transversely polarized nucleon, where x is the longitudinal8momentum fraction of the proton carried by quark q. It is loosely constrained by...
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 restriction to implement further constraints through the Lagrange multipliers method. The results are...
We propose a new method for the extraction of transversity distributions from Semi-Inclusive Deep Inelastic Scattering (SIDIS) data. The $u$-quark and $d$-quark transversity distributions are usually extracted from spin asymmetry data in the SIDIS processes, where it has to be coupled with a chiral odd-partner, typically the Collins or the di-hadron fragmentation function. Motivated by a...
Quasi-PDF approach, proposed by Ji in 2013, has made it possible to directly extract light-cone PDFs from lattice QCD. This approach relies on the extraction of matrix elements of space-like operators for fast-moving hadrons. Quasi-PDFs can be related to the light-cone PDFs through a perturbatively calculable matching coefficient. We explore the formalism of matching, for the very first time,...
Twist-3 PDFs contain important information that characterizes nucleon's structure. In this talk, we show our lattice exploration of the twist-3 PDFs g_T(x) and h_L(x). We use the quasi-distribution approach to connect the lattice-extracted matrix elements, renormalized in the RI/MOM scheme, to light-cone distributions, applying the matching procedure that we developed in parallel. We also...
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 $\pi^0$ ($2 < \eta < 4$) was brought up. Bigger asymmetry was observed in more isolated final state which was connected with the non-perturbative event topology. Since the non-perturbative contribution has been...
Hard exclusive meson production is a well established tool to study the 3D nucleon structure in terms of the transverse position and the longitudinal momentum component of the partons. The QCD factorisation mechanism in the "nearly forward region" ($t/Q^{2}$ small) can be divided into a hard part, described by perturbative QCD (pQCD) and in two general structure functions, the GPDs for the...
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...
We will present results on Spin Density Matrix Elements (SDMEs) measured in hard exclusive $\rho^{0}$ meson muoproduction on the proton at COMPASS using 160 GeV/c polarised $\mu^{+}$ and $\mu^{-}$ beams scattering off a liquid hydrogen target. The measurement covers the range 5 GeV/$c^{2}$ < $W$ < 17 GeV/$c^{2}$, 1.0 (GeV/$c$)$^{2}$ < Q$^{2}$ < 10.0 (GeV/$c$)$^{2}$ and 0.01 (GeV/$c$)$^{2}$...
Photoproduction of two photons is the simplest example allowing the study of QCD factorization in a family of $2\rightarrow 3$ processes. Because of the C-symmetry, the amplitude is sensitive only to valence quarks GPDs, which makes it interesting for the GPD extraction program. Leading-order calculation, presented in [1], and the subsequent work concerning electroproduction of 2 photons [2],...
In spectator tagged process on a nucleus, a nucleon or nuclear fragment is detected in the target fragmentation region where the spectator has a slow (0 - few 100 MeV) momentum compared to the ion center-of-mass. Detection of the spectator results in additional control over the initial nuclear configuration of the ion target compared to inclusive scattering where one averages over all possible...
In this talk we will outline the connections among the inclusive jet correlator, the single-hadron fragmentation correlator, and the quark propagator, which open the way to studies of fundamental mechanisms in QCD -such as the dynamical generation of mass- by looking at the fully inclusive hadronization of a quark. In particular, we will focus on observables in semi-inclusive DIS and $e^+e^-$...
The Solenoidal Tracker at the Relativistic Heavy Ion Collider (STAR) experiment probes the gluon helicity distribution $\Delta g(x, Q^2)$ using collisions of longitudinally polarized protons at $\sqrt{s} = 200$ GeV and $\sqrt{s} = 510$ GeV. $\Delta g(x, Q^2)$ can be accessed through the double spin asymmetries $A_{LL}$ in gluon-dominated hard scattering processes via inclusive jet and di-jet...
Understanding the proton spin composition from the quarks and gluons spin polarization and their motion is important to test various kinds of sum rules and nonperturbative properties of hadrons. At the Relativistic Heavy Ion Collider (RHIC), we collide longitudinally polarized proton beams and measure the double helicity asymmetry $A_{LL}$, which is an important physical quantity for...
We made simultaneous extraction of spin averaged and spin dependent PDFs within multistep MC procedures, with combined analysis of inclusive unpolarized and polarized Jet from RHIC to Tevatron energies. By analyzing the preliminary results we had, we were able to further constrain on $\Delta g$.
We present a new global QCD analysis of spin-averaged and spin-dependent PDFs from high-$x$ DIS and $W$ production data using a Monte Carlo approach. This analysis includes the first extraction of the helicity-dependent antiquark asymmetry $\Delta \bar{u} - \Delta \bar{d}$ using $W$ production data in $\vec{p} p$ collisions at RHIC. We also focus on the high-$x$, low-$W$ region, where...
The small-$x$ quark helicity evolution equations at double-logarithmic order, with the kernel $\sim \alpha_s\ln^2 (1/x)$, had been derived previously, and the equations were solved analytically at large $N_c$ and numerically at large $N_c$ and $N_f$. (Here, $N_c$ and $N_f$ are the numbers of quark colors and flavors, respectively.) In this work, we derive the single-logarithmic corrections to...
We discuss the role of the chiral “triangle” anomaly in deeply inelastic scattering (DIS) of electrons off polarized protons employing a powerful worldline formalism which allows for the efficient computation of perturbative multi-leg Feynman amplitudes. We demonstrate how the triangle anomaly appears at high energies in the DIS "box diagram" for the polarized structure function...
Different decompositions (sum rules) for the proton mass have been proposed in the literature. All of them are related to the energy-momentum tensor in quantum chromodynamics (QCD). In this talk, we will provide an overview and a comparison of the various mass decompositions by highlighting recent developments. Special attention will be paid to the physical interpretation of the individual...
A unique feature of generalised parton distributions (GPDs) is their relation to the QCD energy-momentum tensor. In particular, GPDs provide access to the mechanical properties of the proton i.e. the distributions of pressure and shear stress induced by the partonic structure. In principle, these distributions can be experimentally determined in a model-independent way from the subtraction...
We obtain the gravitational
form factors (GFFs) and investigate their applications for the description of the mechanical properties, i.e., the distributions of pressures, shear forces inside proton, and the mechanical radius, in a light-front quark-diquark model constructed by the soft-wall AdS/QCD. The GFFs, $A(Q^2)$ and $B(Q^2)$ are found to be consistent with the lattice QCD, while the...
The form factors of the energy-momentum tensor (EMT) contain a wealth of information about the nucleon. This information can be described at the density level in terms of energy, pressure, shear forces, and angular momentum distributions inside the nucleon. In this talk, we present new results on the associated 2D densities of the energy-momentum tensor in the bag model, formulated in the...
In recent years, a lot of attention has been invested in the study of the nucleon structure, in particular, its spin decomposition.
Early experiments such as HERMES and COMPASS showed that an important fraction of the latter could not be explained solely by the contribution of the intrinsic spins of the quarks. More recent experiments exhibit that even the gluon spin contribution isn't...
The global properties of particles can be studied through the Energy-Momentum Tensor (EMT) matrix elements. The forward EMT matrix elements allow one to construct different types of mass/energy decompositions, whereas the off-forward EMT matrix elements carry information on the distribution of energy, angular momentum, pressure and shear forces in the particles.
The structure of the EMT for...
Since the first surprising results on the spin structure of the proton by the EMC experiment in the late 1980s, much progress has been made in understanding the origin of the proton spin. However, the sea quark contribution to the proton spin, for example, the polarized distributions of the strange quark(anti-quark), s($\bar{s}$), is still not well constrained by experimental data. Since the...
Experimental data from Belle Collaboration for the transverse polarization of $\Lambda$'s measured in $e^+e^-$ annihilation processes are used to extract the polarizing fragmentation function (FF) within a TMD approach.
We consider both associated and inclusive $\Lambda$ production, showing a quite consistent scenario. Good separation in flavor is obtained, with four independent FFs....
We derive the transverse momentum dependent factorization and resummation formula of the unpolarized transverse momentum distribution for the single hadron production with the thrust axis in an electron-positron collision. Two different kinematic regions are considered, including small transverse momentum limit and joint transverse momentum and threshold limit. Using effective theory methods,...
In this talk I will present a study of transverse polarization of lambda-hyperons in single-inclusive leptonic annihilation (SIA). We show that when the transverse momentum of the lambda-baryon is measured with respect to the thrust axis, a transverse momentum dependent (TMD) formalism is required and the polarization is generated by the TMD polarizing fragmentation function (TMD PFF),...
We report new measurements of the production cross sections of pairs of charged pions and kaons as a function of their fractional energies as well as azimuthal asymmetries of back-to-back pairs of charged and neutral mesons. The former measurement aims at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or providing a means to characterise the...
The dynamical structure of hadronic matter is encoded in two non-perturbative, Transverse-Momentum-Dependent (TMD) partonic densities, the TMD distribution and fragmentation functions. TMD PDFs describe the way partons are arranged in nucleons, while TMD FFs are related to the mechanism of hadronization.
A successful phenomenological extraction of these functions relies on their universality...
The HERMES experiment has collected a wealth of data using the 27.6 GeV polarized HERA lepton beam and various polarized and unpolarized gaseous targets. This allows for a series of unique measurements of observables sensitive to the multidimensional (spin) structure of the nucleon, in particular semi-inclusive deep-inelastic scattering (SIDIS) measurements, for which the HERMES dual-radiator...
The understanding of the fragmentation process is important as it will provide us with a deep insight into the elusive mechanism of hadronization. In recent years, a hadron distribution inside jets has emerged as an important observable to understand and extract fragmentation functions. In this talk, I will demonstrate such usefulness of studying hadron distribution inside jets and how its...
Studying the partonic and spin structure of the nucleon via Semi-Inclusive measurements of DIS (SIDIS) is one of the most important objectives of the COMPASS experiment (CERN, SPS). Nucleon spin (in)dependent azimuthal asymmetries accessible in single-hadron and hadron-pair production in SIDIS encode information on both the partonic structure of the nucleon and the fragmentation process....
Many decades of experiments in deep inelastic scattering (DIS) of lepton beams off nucleons have mapped out the momentum distributions in the nucleon in terms of one-dimensional (1-D) parton distribution functions (PDFs). While these measurements provided significant insight into the structure of the nucleon, many important and interesting aspects of the nucleon structure cannot be revealed in...
Dihadron beam spin asymmetries provide a wide range of insights into nucleon structure and hadronization. Recent measurements at CLAS12 provide the first empirical evidence of a nonzero $G_1^\perp$, the parton helicity-dependent dihadron fragmentation function (DiFF) encoding spin-momentum correlations in hadronization. These measurements also allow for a point-by-point extraction of the...
Semi-Inclusive Deep-Inelastic Scattering (SIDIS) is one of the processes that allow us to extract information about Transverse Momentum Distributions (TMDs) and will be the main access to TMDs at the EIC.
Using sensitivity coefficients and reweighing techniques, we provide an estimate of the impact that EIC data will have on unpolarized Transverse-Momentum Dependent (TMD) Parton Distribution...
We present the first Monte Carlo based global QCD analysis of spin-averaged and spin-dependent parton distribution functions (PDFs) that includes nucleon isovector matrix elements in coordinate space from lattice QCD. We investigate the degree of universality of the extracted PDFs when the lattice and experimental data are treated under the same conditions within the Bayesian likelihood...
