We apply recent developments in large momentum effective theory (LaMET) to formulate a non-perturbative calculation of the single-transverse spin asymmetry in terms of the quasi transverse-momentum-dependent quark distribution functions from the so-called Sivers mechanism. When the spin asymmetry is defined as the ratio of the quark Sivers function over the spin averaged distribution, it can be directly calculated in terms of the relevant quasi distributions with the soft functions and perturbative matching kernels cancelling out. Apart from the general formula presented, we have verified the result in the small transverse distance limit at one-loop order, which reduces to a collinear expansion at twist-three level.
We study the QCD evolution of the Sivers effect in both semi-inclusive deep inelastic scattering (SIDIS) and Drell-Yan production (DY). We pay close attention to the non-perturbative spin-independent Sudakov factor in the evolution formalism and find a universal form which can describe reasonably well the experimental data on the transverse momentum distributions in SIDIS, DY lepton pair and $W/Z$ production. With this Sudakov factor at hand, we perform a global fitting of all the experimental data on the Sivers asymmetry in SIDIS from HERMES, COMPASS and Jefferson Lab. We then make prediction…
We propose measurement of transverse single spin asymmetry (SSA) in charmonium production as a probe of gluon Sivers function. We estimate SSA in low virtuality electroproduction of $J/ψ$ using color evaporation model of charmonium production and existing models of the gluon Sivers function and find sizable asymmetry at JLab, HERMES, COMPASS and eRHIC energies.
We study the single spin asymmetry in the back-to-back dijet production in transversely polarized proton-proton collisions. Such an asymmetry is generated by the Sivers functions in the incoming polarized proton. We propose a QCD formalism in terms of the transverse momentum dependent parton distribution functions, which allow us to resum the large logarithms that arise in the perturbative calculations. We make predictions for the Sivers asymmetry of hadronic dijet production at the kinematic region that is relevant to the experiment at the Relativistic Heavy Ion Collider (RHIC). We further co…
We study the Sivers single spin asymmetry of the Drell-Yan lepton pair production in the small-$x$ regime. We find that in the corresponding kinematic region the spin asymmetry calculated in the small-$x$ approach is consistent with either the usual transverse-momentum-dependent factorization formalism or the collinear factorization formalism, respectively. We estimate the Sivers asymmetry for both polarized p+p and p+A collisions and argue that the Drell-Yan production is an interesting and unique probe for both the transverse spin physics and the small-$x$ saturation effect.
We investigate the Sivers asymmetry in the pion-induced single polarized Drell-Yan process in the theoretical framework of the transverse momentum dependent factorization up to next-to-leading logarithmic order of QCD. Within the TMD evolution formalism of parton distribution functions, the recently extracted nonperturbative Sudakov form factor for the pion distribution functions as well as the one for the Sivers function of the proton are applied to numerically estimate the Sivers asymmetry in the $π^- p$ Drell-Yan at the kinematics of the COMPASS at CERN. In the low $b$ region, the Sivers fu…
Recently, it has been pointed out that there exists a connection between the generalized parton distribution $E(x,0,t)$ and the Sivers asymmetry. For transversely polarized nucleon targets, generalized parton distributions are asymmetric in impact parameter space. This impact parameter space asymmetry, together with the final state interaction of the active quark, gives rise to the Sivers asymmetry in momentum space. We demonstrate this phenomenon explicitly in the scalar diquark model. This result also illustrates the physics that underlies the correlation between the anomalous magnetic momen…
We calculate the Sivers asymmetry in the photoproduction of almost back-to-back $J/ψ$-jet pair in the process $ep^\uparrow \to J/ψ+\mathrm{jet}+X$, which will be possible at the future planned electron-ion collider (EIC). We use the framework of generalized parton model (GPM), and NRQCD for calculating the $J/ψ$ production rate. We include contributions from both color singlet and color octate states in the asymmetry. We obtain sizable Sivers asymmetry that can be promising to determine the gluon Sivers function. We also investigate the effect of TMD evolution on the asymmetry.
A recent investigation of the single spin asymmetry (SSA) in low virtuality electroproduction/photoproduction of $J/ψ$ in color evaporation model is presented. It is shown that the asymmetry is sizable and can be used as a probe for the still unknown gluon Sivers function.
We study the Sivers asymmetry in semi-inclusive deep inelastic scattering: the three-gluon correlation function contribution. At the cross section level, we establish the matching between the twist-3 collinear factorization approach and the transverse momentum dependent factorization formalism at the moderate transverse momentum region. The so-called coefficient functions when one expands the quark Sivers function in terms of three-gluon correlation functions are derived, which are essential components in the usual transverse momentum dependent evolution formalism. Finally we calculate the tra…
The SIDIS transverse spin asymmetries weighted with powers of $P_T$, the hadron transverse momentum in the $γN$ reference system,have been introduced already twenty years ago and are considered quite interesting. While the amplitudes of the modulations in the azimuthal distribution of the hadrons are the ratios of convolutions over transverse momenta of the transverse--momentum dependent parton distributions and of the corresponding fragmentation functions, and can be evaluated analytically only making assumptions on the transverse--momentum dependence of these functions, the weighted asymmetr…
The determination of quark angular momentum requires the knowledge of the generalized parton distribution $E$ in the forward limit. We assume a connection between this function and the Sivers transverse-momentum distribution, based on model calculations and theoretical considerations. Using this assumption, we show that it is possible to fit at the same time nucleon anomalous magnetic moments and semi-inclusive single-spin asymmetries. This imposes additional constraints on the Sivers function and opens a plausible way to quantifying the quark angular momentum.
The abundant production of lepton pairs via $J/Ψ$ creation at COMPASS, $π^\pm \, p^\uparrow \to J/Ψ\, X \to \ell^+ \ell^- X$, allows a measurement of the transverse Single Spin Asymmetry generated by the Sivers effect. The crucial issue of the sign change of the Sivers function in lepton pair production, with respect to Semi Inclusive Deep Inelastic Scattering processes, can be solved. Predictions for the expected magnitude of the Single Spin Asymmetry, which turns out to be large, are given.
We analyze the spin asymmetry for single inclusive jet production in proton-proton collisions collected by AnDY experiment at the Relativistic Heavy Ion Collider and the Sivers asymmetry data from semi-inclusive deep inelastic scattering experiments. In particular, we consider the role color gauge invariance plays in determining the process-dependence of the Sivers effect. We find that after carefully taking into account the initial-state and final-state interactions between the active parton and the remnant of the polarized hadron, the calculated jet spin asymmetry based on the Sivers functio…
We study the next-to-leading order perturbative QCD corrections to the transverse momentum-weighted Sivers asymmetry in semi-inclusive hadron production in lepton-proton deep inelastic scattering. The corresponding differential cross section is evaluated as a convolution of a twist-three quark-gluon correlation function, often referred to as Qiu-Sterman function, the usual unpolarized fragmentation function, and a hard coefficient function. By studying the collinear divergence structure, we identify the evolution kernel for the Qiu-Sterman function. The hard coefficient function, which is fini…
We calculate the Sivers and $\cos2ϕ$ azimuthal asymmetries in $J/ψ$ production in polarized and unpolarized semi-inclusive $ep$ collision respectively, using the formalism based on transverse momentum dependent parton distributions (TMDs). Non-relativistic QCD based color octet model is employed for calculating the $J/ψ$ production rate. The Sivers asymmetry in this process directly probes the gluon Sivers function. The estimated Sivers asymmetry at $z=1$ is negative which is in good agreement with COMPASS data. We also investigate the effect of TMD evolution on the Sivers asymmetry. The $\cos…
We review our transverse momentum dependent factorization and resummation formalism for heavy flavor dijet production at the EIC. In this formalism, we have calculated the heavy flavor mass corrections in the collinear-soft and jet functions, and in the resummed expression for the cross section. By establishing this formalism, we then study the effects of the mass corrections by providing predictions at the EIC for the massive case and for the case where the mass is neglected. We find that the heavy flavor mass effects can give sizable corrections to the predicted asymmetry.
We analyze the Sivers asymmetry in both Drell-Yan (DY) production and semi-inclusive deep inelastic scattering (SIDIS), while considering properly defined transverse momentum dependent parton distribution and fragmentation functions and their QCD evolution. After finding a universal non-perturbative spin-independent Sudakov factor that can describe reasonably well the world's data of SIDIS, DY lepton pair and $W/Z$ production in unpolarized scatterings, we perform a global fitting of all the experimental data on the Sivers asymmetry in SIDIS from HERMES, COMPASS and Jefferson Lab. Then we make…
We discuss the possibility of using electroproduction of $J/ψ$ as a probe of gluon Sivers function by measuring single spin asymmetry (SSA) in experiments with transversely polarized protons and electron beams. We estimate SSA for JLab, HERMES, COMPASS and eRHIC energies using the color evaporation model of charmonium production and find asymmetry up to 25% for certain choices of model parameters which have been used earlier for estimating SSA in the SIDIS and Drell-Yan processes.
Probing the Sivers Asymmetry with Transverse Energy-Energy Correlators in the Small-$x$ Regime
University of Connecticut（康涅狄格大学）；University of California, Los Angeles（加州大学洛杉矶分校）；Mani L. Bhaumik Institute for Theoretical Physics, University of California, Los Angeles（加州大学洛杉矶分校马尼·L·巴乌米克理论物理研究所）；Center for Frontiers in Nuclear Science, Stony Brook University（石溪大学核科学前沿中心）
We study the Sivers asymmetry in inelastic $J/ψ$ leptoproduction, $ep^\uparrow \to e+ J/ψ+X$, within a transverse momentum dependent scheme, the so-called generalized parton model (GPM). The effects of final-state interactions are properly taken into account by employing the color-gauge invariant GPM (CGI-GPM). For the $J/ψ$ formation the non-relativistic QCD (NRQCD) framework is adopted. Predictions for unpolarized cross sections and maximized Sivers asymmetries at EIC energies are given.
A new approach to nonperturbative QCD, holographic light-front QCD, provides a comprehensive model for hadron dynamics and spectroscopy, incorporating color confinement, a universal hadron mass scale, the prediction of a massless pion in the chiral limit, and connections between the spectroscopy of mesons, baryons and tetraquarks across the full hadron spectrum. In this article we present predictions for the Sivers asymmetry and related transverse momentum distributions for the proton based on the light-front wavefunctions of the baryon eigenstate predicted by holographic QCD.
We study the Sivers asymmetry in semi-inclusive hadron production in deep inelastic scattering. We concentrate on the contribution from the photon-gluon fusion channel at ${\cal O}(α_{em}^2 α_s)$, where three-gluon correlation functions play a major role within the twist-3 collinear factorization formalism. We establish the correspondence between such a formalism with three gluon correlation functions and the usual transverse momentum dependent (TMD) factorization formalism at moderate hadron transverse momenta. We derive the coefficient functions used in the usual TMD evolution formalism rela…
The energy scale dependence of the Sivers asymmetry in semi-inclusive deep inelastic scattering is studied numerically within the framework of TMD factorization that was put forward in 2011. The comparison to previous results in the literature shows that the treatment of next-to-leading logarithmic effects is important for the fall-off of the Sivers asymmetry with energy in the measurable regime. The TMD factorization based approach indicates that the peak of the Sivers asymmetry falls off with energy scale Q to good approximation as 1/Q^{0.7}, somewhat faster than found previously based on th…
We investigate the single transverse-spin asymmetry with a $\sin (ϕ_h-ϕ_S)$ modulation in the charged Kaon produced and in $Λ$ hyperon produced SIDIS process within the theoretical framework of transverse momentum dependent (TMD) factorization at the next-to-leading-logarithmic order. The asymmetry is contributed by the convolution of Sivers function and the unpolarized fragmentation function $D_1$ for the produced hadron. The parametrization for the proton Qiu-Sterman function, which is closely related to the Sivers function, is adopted to numerically estimate the Sivers asymmetry at the kine…
We derive the time-reversal modified universality for both quark and gluon Sivers function from the parity and time-reversal invariance of QCD. We calculate the single transverse-spin asymmetry of inclusive lepton from the decay of $W$ bosons in polarized proton-proton collision at RHIC, in terms of the Sivers function. We find that although the asymmetry is diluted from the $W$ decay, the lepton asymmetry is at the level of several percent and is measurable for a good range of lepton rapidity at RHIC. We argue that this measurable lepton asymmetry at RHIC is an excellent observable for testin…
We study a weighted asymmetry in the azimuthal distribution of photon-jet pairs produced in the process p^\uparrow p --> γjet X with a transversely polarized proton. We focus on the contribution of the Sivers effect only, considering experimental configurations accessible at RHIC-BNL. We show that predictions for the asymmetry, obtained in terms of gluonic-pole cross sections calculable in perturbative QCD, can be tested and clearly discriminated from those based on a generalized parton model, involving standard partonic cross sections. Experimental measurements of the asymmetry will therefore…
I study the effect of scalar and spin-orbit rescattering terms, in the production of a nonzero Sivers-like asymmetry in proton-proton collisions (nclusive production and Drell-Yan) at moderate center of mass energies $\sqrt{s}$ $<$ 15 GeV and transverse momentum up to 3 GeV/c. An ultrarelativistic generalization of the Glauber formalism is here used to (i) fit the scalar and spin-orbit interaction terms on proton-proton elastic scattering data, including analyzing power, (ii) transfer such information to inclusive proton-proton scattering. It is shown that the phenomenological interactions res…
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 charm and bottom dijet production at the future Electron-Ion Collider. Furthermore, we compare theoretical predictions with and without the inclusion of finite quark masses. We find that the heavy flavor m…
The single spin asymmetry A_N, for large P_T single inclusive particle production in p(transv. pol.) p collisions, is considered within a generalised parton model and a transverse momentum dependent factorisation scheme. The focus is on the Sivers effect and the study of its potential contribution to A_N, based on a careful analysis of the Sivers functions extracted from azimuthal asymmetries in semi-inclusive deep inelastic scattering processes. It is found that such Sivers functions could explain most features of the A_N data, including some recent STAR results which show the persistence of …
We extend our analysis of transverse single spin asymmetry (SSA) in electroproduction of $J/ψ$ to include the effect of the scale evolution of the transverse momentum dependent (TMD) parton distribution functions and gluon Sivers function. We estimate SSA for JLab, HERMES, COMPASS, and eRHIC energies using the color evaporation model of charmonium production, using an analytically obtained approximate solution of TMD evolution equations discussed in the literature. We find that there is a reduction in the asymmetry compared with our predictions for the earlier case considered by us, wherein th…
A formalism is presented to evaluate the Sivers function in constituent quark models. A non-relativistic reduction of the scheme is performed and applied to the Isgur-Karl model. The results obtained are consistent with a sizable Sivers effect and the signs for the u and d flavor contributions turn out to be opposite. The Burkardt Sum Rule is fulfilled to a large extent. After the estimate of the QCD evolution of the results from the momentum scale of the model to the experimental one, a reasonable agreement with the available data is obtained. A calculation of nuclear effects in the extractio…
We show that the transverse double spin asymmetry (DSA) in the Drell-Yan process contributed only from the Sivers functions can be picked out by the weighting function $\frac{Q_T}{M^2}(\cos(ϕ-ϕ_{S_1})\cos(ϕ-ϕ_{S_2})+3\sin(ϕ-ϕ_{S_1})\sin(ϕ-ϕ_{S_2}))$. The asymmetry is proportional to the product of two Sivers functions from each hadron $f_{1T}^{\perp(1)}\times f_{1T}^{\perp (1)}$. Using two sets of Sivers functions extracted from the semi-inclusive deeply elastic scattering data at HERMES, we estimate this asymmetry in the $p^\uparrow\bar{p}^\uparrow$ Drell-Yan process which is possible to be p…
We investigate the transverse momentum weighted Sivers asymmetries in the processes with transversely polarized proton target, including the $\frac{P_{hT}}{zM_p}\sin (ϕ_h-ϕ_S)$ weighted asymmetry in charged hadron production in semi-inclusive deeply inelastic scattering (SIDIS) and the $\frac{q_T}{M_p}\sin (ϕ_S)$ weighted asymmetry in $π^- p$ Drell-Yan process. Due to the integration over the transverse momentum, the weighted asymmetries can be expressed as the product of the transverse-moments of the transverse momentum dependent (TMD) parton distribution functions (PDFs) and fragmentation fu…
In this contribution, we will present a short overview of the transverse momentum dependent (TMD) approach as a tool for studying the 3-dimensional structure of hadrons in high-energy (un)polarized hadron collisions. We will then summarize the present status of a running research programme that aims at constraining the poorly known transverse momentum dependent gluon Sivers function, through the study of single spin asymmetries in quarkonium (mainly $J/ψ$), pion, and $D$-meson production in polarized proton-proton collisions at RHIC. Finally, we will shortly discuss perspectives for this field…
We study the single transverse spin asymmetries in the single inclusive particle production within the framework of the generalized parton model (GPM). By carefully analyzing the initial- and final-state interactions, we include the process-dependence of the Sivers functions into the GPM formalism. The modified GPM formalism has a close connection with the collinear twist-3 approach. Within the new formalism, we make predictions for inclusive $π^0$ and direct photon productions at RHIC energies. We find the predictions are opposite to those in the conventional GPM approach.
The Sivers effect in single hadron semi-inclusive deep inelastic scattering (DIS) on a transversely polarized nucleon describes the modulation of the cross section with the sine of the azimuthal angle between the produced hadron's transverse momentum and the nucleon spin ($\boldsymbol{P}_h$ and $φ_S$ respectively). This effect is attributed to the so-called Sivers parton distribution function of the nucleon. We employ a simple phenomenological parton model to derive the relevant cross section for two-hadron production in semi-inclusive deep inelastic scattering including the Sivers effect. We …
The single transverse spin asymmetry in D meson production at RHIC can provide a clean measure of the gluon Sivers distribution function. At intermediate rapidity, D production is largely dominated by the elementary gg -> c c-bar channel, where there cannot be any transverse spin transfer. Therefore, any transverse single spin asymmetry observed for D's produced in polarized proton-proton interactions can only originate from the Sivers effect in the gluon distribution functions. A sizeable transverse single spin asymmetry measured by PHENIX or STAR experiments would then give direct informatio…
We compute the gluon Sivers function $f_{1T}^{\perp g}(x,k_\perp)$ of the transversely polarized nucleon at small-$x$ by exploiting the known connection between the dipole gluon Sivers function and the Odderon. We numerically solve the evolution equation for the Odderon both in the linear and nonlinear regimes. While we find that the $x$ and $k_\perp$ dependences of the Sivers function do not factorize as a result of the quantum evolution, factorization breaking is not numerically significant, and is much milder than what one expects in the case of unpolarized TMDs. We also point out the possi…
We propose low-virtuality leptoproduction of open-charm, $p^\uparrow l\to D^0+X$, as a probe of the gluon Sivers function (GSF). At leading-order, this process directly probes the gluon content of the proton, making detection of a trasverse single-spin asymmetry in the process a clear indication of a non-zero GSF. Considering the kinematics of the proposed future Electron-Ion Collider (EIC), we present predictions for asymmetry using fits of the GSF available in literature. We also study the asymmetry at the level of muons produced in D-meson decays and find that the asymmetry is preserved the…
We study the single transverse spin asymmetry of prompt photon production in high energy proton-proton scattering. We include the contributions from both the direct and fragmentation photons. While the asymmetry for direct photon production receives only the Sivers type of contribution, the asymmetry for fragmentation photons receives both the Sivers and Collins types of contributions. We make a model calculation for quark-to-photon Collins function, which is then used to estimate the Collins asymmetry for fragmentation photons. We find that the Collins asymmetry for fragmentation photons is v…
We study the low-virtuality inclusive leptoproduction of open charm, $p^\uparrow l\rightarrow D^0+X$ as a probe of the gluon Sivers function. We perform the analysis in a generalised parton model framework. At leading order, this process is sensitive only to the gluon content of the proton. Hence any detection of a transverse single-spin asymmetry in this process would be clear indication of a non-zero gluon Sivers function (GSF). Considering COMPASS and a future Electron-Ion Collider (EIC), we present predictions for asymmetry using fits for the GSF available in literature. Predictions for pe…
One of the important objectives of the COMPASS experiment (SPS, CERN) \cite{Abbon:2007pq} is the exploration of the transverse spin structure of the nucleon via spin dependent azimuthal asymmetries in single-hadron production in deep inelastic scattering of polarized leptons off transversely polarized targets. For this purpose a series of measurements were made in COMPASS, using 160 GeV/c longitudinally polarized muon beam and transversely polarized $^6LiD$ (in 2002, 2003 and 2004) and $NH_3$ (in 2007 and 2010) targets. In the past few years considerable theoretical interest and experimental e…
In this paper we propose to investigate the transverse single spin asymmetry in the inelastic $J/Ψ$ photoproduction in $p^\uparrow p$ and $p^\uparrow A$ collisions at RHIC energies. At leading order this process probes the gluon Sivers function. We predict large values for the cross sections, which indicates that its experimental analysis is, in principle, feasible. The rapidity dependence of the single spin asymmetry is presented. We obtain that the asymmetry is strongly dependent on the model used for the gluon Sivers function and that it can be probed by the analysis of the $J/Ψ$ production…
The Sivers function, an asymmetric transverse-momentum distribution of the quarks in a transversely polarized nucleon, is calculated in the MIT bag model. The bag quark wave functions contain both $S$-wave and $P$-wave components, and their interference leads to nonvanishing Sivers function in the presence of the final state interactions. We approximate these interactions through one-gluon exchange. An estimate of another transverse momentum dependent distribution $h_1^\perp$ is also performed in the same model.
Sivers asymmetry, adopted to explain transverse single spin asymmetries (SSA) observed in inclusive pion production, p(transv. polarized) p --> pion + X and p-bar(transv. polarized) p --> pion + X is used here to compute SSA in Drell-Yan processes; in this case, by considering the differential cross section in the lepton-pair invariant mass, rapidity and transverse momentum, other mechanisms which may originate SSA cannot contribute. Estimates for RHIC experiments are given.
Polarised Semi-Inclusive Deep Inelastic Scattering (SIDIS) processes allow to study Transverse Momentum Dependent partonic distributions (TMDs), which reveal a non trivial three dimensional internal structure of the hadrons in momentum space. One of the most representative of the TMDs is the so-called Sivers function that describes the distribution of unpolarized quarks inside a transversely polarized proton. We present a novel extraction of the Sivers distribution functions from the most recent experimental data of HERMES and COMPASS experiments. Using suitable parametrizations, within the TM…
We perform global fit to the quark Sivers function within the transverse momentum dependent (TMD) factorization formalism in QCD. We simultaneously fit Sivers asymmetry data from Semi-Inclusive Deep Inelastic Scattering (SIDIS) at COMPASS, HERMES, and JLab, from Drell-Yan lepton pair production at COMPASS, and from $W/Z$ boson at RHIC. This extraction is performed at next-to-leading order (NLO) and next-to-next-to leading logarithmic (NNLL) accuracy. We find excellent agreement between our extracted asymmetry and the experimental data for SIDIS and Drell-Yan lepton pair production, while tensi…
The Sivers effect describes the correlation of the unpolarized parton's transverse momentum with the transverse spin of the nucleon. It manifests as a sine modulation of the cross section for single hadron semi-inclusive deep inelastic scattering (SIDIS) on a transversely polarized nucleon with the azimuthal angle between the produced hadron's transverse momentum and the nucleon spin ($φ_h$ and $φ_S$, respectively). It has been recently suggested that the Sivers effect can also be measured in two hadron SIDIS process as sine modulations involving the azimuthal angles $φ_T$ and $φ_R$ of both th…
We consider the recent RHIC data on the transverse single spin asymmetry (SSA) A_N, measured in p(transv. polarized) p -> pi^0 X processes at mid-rapidity by the PHENIX collaboration. The measurement is consistent with a vanishing SSA. We analyze this experimental information within a hard scattering approach based on a generalized QCD factorization scheme, with unintegrated, transverse momentum dependent (TMD), parton distribution and fragmentation functions. It turns out that, in the kinematical region of the data, only the gluon Sivers effect could give a large contribution to A_N; its vani…
We perform a calculation of Sivers function in a light-cone SU(6) quark-diquark model with both scalar diquark and vector diquark spectators. We derive the transverse momentum dependent light-cone wave function of the proton by taking into account the Melosh-Wigner rotation. By adopting one-gluon exchange, we obtain a non-vanishing Sivers function of $down$ quark from interference of proton spin amplitudes. We analyze the $\frac{|P_{h\perp}|}{M}$ weighted Sivers asymmetries in $π^+$, $π^-$ and $π^0$ electroproduction off transverse polarized proton target, averaged and not averaged by the kine…
We calculate the gluon Sivers function of the proton in the valence-$x$ region using a light-cone spectator model with the presence of the gluon degree of freedom. We obtain the values of the parameters by fitting the model resulting gluon density distribution to the known parametrization. We find that our results agree with the recent phenomenological extraction of the gluon Sivers function after considering the evolution effect. We also estimate the mean transverse momentum of the gluon in a transversely polarized proton and find that it is within the range implied by the Burkardt sum rule.
The production of D mesons in the scattering of transversely polarized protons off unpolarized protons at RHIC offers a clear opportunity to gain information on the Sivers gluon distribution function. D production at intermediate rapidity values is dominated by the elementary g g --> c cbar channel; contributions from q qbar --> c cbar s-channel become important only at very large values of x_F. In both processes there is no single spin transfer, so that the final c or cbar quarks are not polarized. Therefore, any transverse single spin asymmetry observed for D's produced in p(transv. polarize…
Heavy flavour production like $J/ψ$ and $D$- meson production in scattering of electrons/unpolarized protons off polarized proton target offer promising probes to investigate gluon Sivers function. In this talk, I will summarize our recent work on trasverse single spin asymmetry in $J/ψ$ -production and $D$ - meson production in $p p^\uparrow$ scattering using a generalized parton model approach. We compare predictions obtained using different models of gluon Sivers function within this approach and then, taking into account the transverse momentum dependent evolution of the unpolarized parton…
I study the effect of scalar and spin-orbit absorption potentials, in the production of a nonzero Sivers-like asymmetry in hadron-hadron high energy collisions (Drell-Yan and single spin asymmetries). A basic model is built for the intrinsic state of a quark in the projectile hadron. S-wave and P-wave 2-component states are considered. Before the hard event, this quark is subject to absorbing scalar and spin-orbit local mean fields simulating interactions with a composite target. The relevant interaction terms are found to be the imaginary diagonal spin-orbit ones. Spin rotating terms, and sca…
We perform the global analysis of polarized Semi-Inclusive Deep Inelastic Scattering (SIDIS), pion-induced polarized Drell-Yan (DY), and $W^\pm/Z$ 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 N$^3$LO accuracy. The Qiu-Sterman function is determined in a model-independent way from the extracted Sivers function. We also evaluate the significance of the predicted sign change of Sivers function in DY with respect to SIDIS.
The Sivers mechanism gives rise to a non-zero average transverse momentum of partons inside a transversely polarized target. According to a sum rule of Burkardt this transverse momentum vanishes when summing over all partons. We explicitly check the Burkardt sum rule by means of one-loop calculations for a quark target in perturbative QCD and for a diquark spectator model of the nucleon. In both cases the sum rule is fulfilled.
In this paper we probe the Sivers asymmetries through $\rm J/ψ$ photoproduction in $\rm p^\uparrow p$ collision within the non-relativistic QCD framework, based on color octet model and the Transverse Momentum Dependent Parton Distributions (TMDs). Both the DGLAP evolution and the TMD evolution are included. The intensity and the sign of the Sivers asymmetry is strongly related on evolution model used to investigate the Gluon Sivers Function (GSF). A sizable asymmetry is obtained as a function of the rapidity, $\rm log{(x_γ)}$ or $\rm log{(x_{g})}$ dependence using a recent parametrization of …
In this paper we study the single spin asymmetry $A_{UT}^{\sin(ϕ_h-ϕ_S)}$ of a single hadron production in semi-inclusive deep inelastic scattering (SIDIS) within the framework of transverse momentum dependent (TMD) factorization up to next-to-leading logarithmic (NLL) order of QCD. The asymmetry is contributed by the convolution of the Sivers function and the unpolarized fragmentation function. Specifically, the Sivers function in the coordinate space and perturbative region can be represented as the convolution of the $C$-coefficients and the corresponding collinear correlation functions, am…
