Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSingle spin asymmetries in ultra-peripheral $p^uparrow A$ collisions
104
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We suggest inclusive hadron production in ultra-peripheral proton-nucleus collisions (UPCs) $p^uparrow A to h AX$ as a new channel to investigate single spin asymmetries (SSAs), in particular, to test the assumed dominance of the contribution from twist-three fragmentation functions. The UPC cross sections are obtained by considering the photoproduction limit of semi-inclusive deep inelastic scattering (SIDIS). In particular, we find simple formulas for the polarized UPC cross sections in the collinear twist-three framework. We then numerically calculate the fragmentation contribution to SSA in $p^uparrow A to pi A X$ at $sqrt{s} = 200$ GeV and find a few percent asymmetry in the forward region.
rate research
Read More
We present estimates of transverse single-spin asymmetry in prompt photon production in the scattering of low virtuality photons off a polarized proton target and discuss the possibility of using this as a probe to get information about the gluon Sivers function (GSF). Using a generalized parton model (GPM) framework, we estimate the asymmetries at electron-ion collider energy ($sqrt{s}$ =140 GeV) taking into account both direct and resolved photon processes and find that the dominant contribution, up to $10%$, comes from quark Sivers function (QSF) while the contribution from GSF is found to be up to $2%$. However, upon taking into account the effects of the process-dependent initial and final state interactions through the color-gauge invariant generalized parton model approach we find that the situation is significantly changed, with near zero contributions from the QSFs and up to a $1%$ level contribution from the textit{f}-type GSF. Our results indicate that this process may be useful for distinguishing between GPM and color-gauge invariant generalized parton models and can be used as a good probe of textit{f}-type GSF.
We calculate the transverse single-spin asymmetry (SSA) for $J/psi$ production in proton-proton collisions, within non-relativistic QCD, employing the transverse momentum dependent, generalized parton model, which includes both spin and intrinsic motion effects. In particular, we study the role of the color octet mechanism in accessing the gluon Sivers function. In doing that, we also show, within this approach, how the singularities coming from color octet terms in the low-$P_T$ region can be handled, leading to finite cross sections. Predictions for both unpolarized cross sections and SSAs are given and compared against PHENIX data. Estimates for LHCb in the fixed target mode are also presented.
$J/psi$ production in p-p ultra-peripheral collisions through the elastic and inelastic photoproduction processes, where the virtual photons emitted from the projectile interact with the target, are studied. The comparisions between the exact treatment results and the ones of equivalent photon approximation are expressed as $Q^{2}$ (virtuality of photon), $z$ and $p_{T}$ distributions, and the total cross sections are also estimated. The method developed by Martin and Ryskin is employed to avoid double counting when the different production mechanism are considered simultaneously. The numerical results indicate that, the equivalent photon approximation can be only applied to the coherent or elastic electromagnetic process, the improper choice of $Q^{2}_{mathrm{max}}$ and $y_{mathrm{max}}$ will cause obvious errors. And the exact treatment is needed to deal accurately with the $J/psi$ photoproduction.
We report on a recent investigation of the single spin asymmetry (SSA) in low virtuality electroproduction of $J/psi$ in color evaporation model. We show that this can be used as a probe for the still unknown gluon Sivers function.
The lepton pair production in ultra-peripheral collisions (UPC) is studied in the classical field approximation. We derive a general form of the cross section in terms of photon distributions which depend on the transverse momentum and coordinate based on the wave packet form of nuclear wave functions. Such a general form of the cross section in the classical field approximation contains the results of the generalized equivalent photon approximation (EPA) as well as the corrections beyond EPA in the Born approximation. By rewriting the general form of the cross section in light-cone coordinates, we find a good connection with the transverse momentum dependent distribution (TMD) factorization formalism in the Born approximation. Our numerical results are consistent with current experimental data.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
