We present an exploratory study of gaugino-pair production in polarized and unpolarized hadron collisions, focusing on the correlation of beam polarization and gaugino/Higgsino mixing in the general Minimal Supersymmetric Standard Model. Helicity-dependent cross sections induced by neutral and charged electroweak currents and squark exchanges are computed analytically in terms of generalized charges, defined similarly for chargino-pair, neutralino-chargino associated, and neutralino-pair production. Our results confirm and extend those obtained previously for negligible Yukawa couplings and nonmixing squarks. Assuming that the lightest chargino mass is known, we show numerically that measurements of the longitudinal single-spin asymmetry at the existing polarized pp collider RHIC and at possible polarization upgrades of the Tevatron or the LHC would allow for a determination of the gaugino/Higgsino fractions of charginos and neutralinos. The theoretical uncertainty coming from factorization scale and squark mass variations and the expected experimental error on the lightest chargino mass is generally smaller than the one induced by the polarized parton densities, so that more information on the latter would considerably improve on the analysis.
The contribution of the anomalous quark-gluon interaction induced by instantons to the polarized and unpolarized gluon distributions in nucleon is estimated. It is shown that this interaction leads to negative gluon polarization in nucleon.
We discuss the structure functions and the parton distributions in the virtual photon target, both polarized and unpolarized, beyond the leading order in QCD. We study the factorization-scheme dependence of the parton distributions.
A new Monte-Carlo generator including real radiated photons in DIS on polarized and unpolarized targets is presented. Analytical and numerical tests are performed and discussed in details.
A brief survey is given of recent results on the resummation of leading small-x terms for unpolarized and polarized non--singlet and singlet structure function evolution.
Some simple relations between unpolarized and polarized quark parton distributions have direct experimental consequences which will be presented here. In particular, we will see that it is possible to relate the deep inelastic structure functions $F_2$ and $g_1$, both for proton and deuteron, in fair agreement with experimental data.
The $O(α_s^2)$ massive operator matrix elements for unpolarized and polarized heavy flavor production at asymptotic values $Q^2 >> m^2$ are calculated in Mellin space without applying the integration-by-parts method. We confirm previous results given in Refs. \cite{BU1,BU2}, however, obtain much more compact representations.
A brief overview is presented of recent developments concerning resummed small-x evolution, based upon the renormalization group equation. The non-singlet and singlet structure functions are discussed for both polarized and unpolarized deep-inelastic scattering. Quantitative results are displayed and uncertainties from uncalculated subleading terms are discussed.
It is shown that the parity--violating deep--inelastic scatterings of unpolarized charged leptons on polarized protons, $\ell^{\mp} + \vec P\to \stackrel{\scriptscriptstyle(-)}{ν_{\ell}} + X$, could provide a sensitive test for the behavior and magnitude of the polarized strange--quark density in a proton. Below charm threshold these processes are also helpful to uniquely determine the magnitude of individual polarized parton distributions.
We present the study of accessing unpolarized and linearly polarized gluon TMDs in J/ψ and Υ(1S) production in unpolarized proton-proton collision at LHC, RHIC and AFTER energies. Non- relativistic QCD based color octet model (COM) is used for estimating quarkonium production rates within transverse momentum dependent factorization formalism. A comparison is drawn between the experimental data and the transverse momentum distribution of quarkonium obtained in COM and color evaporation model.
DIS of unpolarized electron by tensor-polarized deuteron with tagged collinear photon, radiated from initial electron, was considered. The cross section is derived in the Born approximation. The model-independent QED corrections to the Born cross section are also calculated using approach based on the account of all essential Feynman diagrams.
The production rates of lepton-photon and dimuon pairs at the HERA collider and the HERMES experiment are evaluated in the leading order equivalent photon approximation. It is shown that the production rates are sufficient to facilitate the extraction of the polarized and unpolarized equivalent photon distributions of the proton and neutron in the available kinematical regions. It is pointed out that these results indicate the possibility of additional, independent, tests concerning the unpolarized and polarized structure functions F_{1,2}^N and g_{1,2}^N, respectively, of the nucleon.
Starting from Martin, Roberts and Stirling fit for unpolarized deep inelastic structure functions and using the newest experimental data on spin asymmetries we get a fit which provides polarized quark distributions. We analyze the behaviour of such functions near $x$ equal to 1. The first moments of these distributions are also discussed. Our fit prefers combination of proton and neutron data versus proton-deuteron one.
The equivalent photon content of polarized and unpolarized nucleons (protons, neutrons), utilized in Weizsäcker--Williams approximations, are presented. For this purpose a new expression for the elastic photon component of a polarized nucleon is derived. The inelastic photon components are obtained from the corresponding momentum evolution equations subject to the boundary conditions of their vanishing at some low momentum scale. The resulting photon asymmetries, important for estimating cross section asymmetries in photon induced subprocesses are also presented for some typical relevant momen…
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…
New relations between Bjorken polarized, Bjorken unpolarized and Gross-Llewellyn Smith sum rules are desribed. These relations are valid in the region, where both perturbative series and the series in power-suppressed $1/Q^2$-terms do not yet mahifest the features of asymptotic expansions. The experimentally based considerations support these relations which may surve as the guide for possible in future measurements of the Bjorken unpolarized sum rule at Neutrino Factories.
I give an overview of the present knowledge about nonperturbative functions parametrizing the fragmentation into one or two hadrons of (un)polarized light quarks in vacuum, including information on their transverse momentum dependence.
We determine the two-loop 'time-like' Altarelli-Parisi splitting functions, appearing in the next-to-leading order Q^2-evolution equations for fragmentation functions, via analytic continuation of the corresponding 'space-like' splitting functions for the evolution of parton distributions. We do this for the case of unpolarized fragmentation functions and - for the first time - also for the functions describing the fragmentation of a longitudinally polarized parton into a longitudinally polarized spin-1/2 hadron such as a Lambda baryon. Our calculation is based on the method proposed and emplo…
The non-singlet and singlet evolution kernels of the twist--2 light-ray operators for unpolarized and polarized deep inelastic scattering are calculated in $O(α_s)$ for the general case of virtualities $q^2, q'^2 \neq 0$. Special cases as the kernels for the general single-variable evolution equation and the Altarelli-Parisi and Brodsky-Lepage limits are derived from these results.
The Drell-Yan (DY) processes with unpolarized colliding hadrons and with the single transversally polarized hadron are considered. The possibility of direct (without any model assumptions) extraction of both transversity and its accompanying T-odd parton distribution functions (PDF) is discussed. For DY processes measurements planned at GSI the preliminary estimations demonstrate that it is quite real to extract both transversity and its accompanying T-odd PDF in the PAX conditions.
We show that linearly polarized gluons inside unpolarized hadrons can be directly probed in jet or heavy quark pair production in electron-hadron collisions. We discuss the simplest cos (2 phi) asymmetries and estimate their maximal value, concluding that measurements of the unknown linearly polarized gluon distribution in the proton should be feasible in future EIC or LHeC experiments. Analogous asymmetries in hadron-hadron collisions suffer from factorization breaking contributions and would allow to quantify the importance of initial and final state interactions.
In this paper hadroproduction of charmonium states in polarized pp collisions is discussed. A thermal picture for the gluonic cloud of comovers is given making contact between the formalism and the measured unpolarized cross sections. The experimentally observed non-polarization of the final J/psi states leads to the consequence that no correlations between the initial proton spin and the final charmonium spin should be existent. Hence the single spin asymmetries vanish to leading order in that model.
QCD corrections to top quark pair production via fusion of both polarized and unpolarized photons are calculated in Supersymmetric Model. The corrections are found to be sizable. The dependence of the corrections on the masses of the supersymmetric particles is also investigated. Furthermore, we studied CP asymmetry effects arising from the complex couplings in the MSSM. The CP violating parameter can reach $10^{-2}$ for favorable parameter values.
We perform a new extraction for unpolarized and polarized parton distribution functions considering a flavor decompositions for sea quarks and applying very recent deep inelastic scattering (DIS) and semi inclusive deep inelastic scattering (SIDIS) data in the fixed flavor number scheme (FFNS) framework. In the new symmetry breaking scenario the light quark and antiquark densities are extracted separately and new parametrization forms are determined for them. The heavy flavors contribution, including charm and bottom quarks, are also taken to be account for unpolarized distributions.
Charged current charm and D meson production is studied in detail as a means of determining the unpolarized and polarized strange sea densities at HERA. All analyses are performed in next-to-leading order QCD, including a calculation of the so far unknown spin-dependent MSbar coefficient functions up to O(alpha_s). It is shown that a decent measurement is possible in the unpolarized case, provided a sufficient luminosity can be reached in the future, while for longitudinally polarized beams it appears to be extremely challenging due to limitations imposed on the expected statistical accuracy b…
We study the fragmentation of a transversely polarized quark into a non collinear (k_T not= 0) spinless hadron and the fragmentation of an unpolarized quark into a non collinear transversely polarized spin 1/2 baryon. These nonperturbative properties are described by spin and k_T dependent fragmentation functions and are revealed in the observation of single spin asymmetries. Recent data on the production of pions in polarized semi-inclusive DIS and long known data on Lambda polarization in unpolarized p-N processes are considered: these new fragmentation functions can describe the experimenta…
Gluons inside unpolarized hadrons can be linearly polarized provided they have a nonzero transverse momentum. The simplest and theoretically safest way to probe this distribution of linearly polarized gluons is through cos(2 phi) asymmetries in heavy quark pair or dijet production in electron-hadron collisions. Future Electron-Ion Collider (EIC) or Large Hadron electron Collider (LHeC) experiments are ideally suited for this purpose. Here we estimate the maximum asymmetries for EIC kinematics.
We examine the unparticle CP-conserving phase effects on the direct CP asymmetry for both polarized and unpolarized lepton in the inclusive $b\to d \ell^+ \ell^-$ transition, where the flavor changing neutral currents are forbidden at tree level but are induced by one-loop penguin diagrams. The averaged polarized and unpolarized CP asymmetries depict strong dependency on the unparticle parameters. In particular, a sizable discrepancy corresponding to the standard model is achieved when the scale dimension value is $1<d_{\UP}< 2$. We see that the unparticle stuff significantly enhances, suppres…
In this thesis the polarized and unpolarized photon distributions of the nucleon (proton, neutron) $(Δ)γ^N$, evaluated in the equivalent photon approximation (EPA), are computed theoretically and the possibility of their experimental determination is demonstrated. Both of them consist of two components: the elastic ones, $(Δ)γ^N_{\rm el}$, due to $N\to γN $, and the inelastic ones, $(Δ)γ^N_{\rm inel}$, due to $N\to γX$, with $X \neq N$. Special attention is devoted to the QED Compton process in $e N \to e γN$ and $e N \to e γX$, which is one of the most important reactions for directly measuri…
We present predictions for charged hadron production and Lambda polarization in p-p and p-Pb collisions at the LHC using the saturation inspired DHJ model for the dipole cross section in the extended geometric scaling region.
It has been known for a long time that hyperons produced in hadronic collisions are polarized perpendicular to the production plane of the reaction. This effect cannot be described by using twist-2 collinear parton correlators only. Here we compute the contribution of twist-3 fragmentation functions to the production of transversely polarized hyperons in unpolarized proton-proton collisions in the framework of collinear factorization. By taking into account the relations among the relevant twist-3 fragmentation functions which follow from the QCD equation of motion and the Lorentz invariance p…
We present numerical solutions of the $Q^2$ evolution equations at next-to-leading order (NLO) for unpolarized and polarized parton distributions, in both the flavor non-singlet and singlet channels. The numerical method is based on a contour integration algorithm in complex-moment space, and, unlike most standard fitting techniques, is not restricted to the use of analytic moments of distributions. We also compute analytic continuations of the recently calculated singlet anomalous dimensions, needed for evolving polarized quark and gluon distributions at NLO. Using these we study the NLO effe…
The QCD corrections to the top-quark pair production via both polarized and unpolarized gluon fusion in $pp$ collisions are calculated in the Minimal Supersymmetric Model(MSSM). We find the MSSM QCD corrections can reach 4% and may be observable in future precise experiments. Furthermore, we studied the CP violation in the MSSM, our results show that the CP violating parameter is sensitive to the masses of SUSY particles (It becomes zero, when the c.m. energy is less than twice the masses of both gluino and stop quarks.) and may reach $10^{-3}$.
We calculate one-loop R-parity violating corrections to the top quark decay into a bottom quark and a polarized W-gauge boson. The corrections are presented according to the total corrections, the longitudinal corrections and the transverse corrections, respectively. We compared our results with the ${\cal O}(α_s)$ QCD corrections, the ${\cal O}(α)$ electroweak (EW) and finite width corrections, and also the supersymmetric (SUSY) corrections with R-parity conservation, respectively.
We calculate $O(α_s)$ corrections to inclusive and isolated double prompt photon production, both for the unpolarized case, and for longitudinal polarization of the incoming hadrons. The calculation is performed using purely analytical techniques for the inclusive case, and a combination of analytical and Monte Carlo techniques to perform the phase space integration in the isolated case. A brief phenomenological study is made of the process $pp\rightarrow γγX$ at CMS energies appropriate for the RHIC heavy ion collider.
Analytical all-orders results are presented for the one-renormalon-chain contributions to the Bjorken unpolarized sum rule for the F_1 structure function of nu N deep-inelastic scattering in the large-N_F limit. The feasibility of estimating higher order perturbative QCD corrections, by the process of naive nonabelianization (NNA), is studied, in anticipation of measurement of this sum rule at a Neutrino Factory. A comparison is made with similar estimates obtained for the Bjorken polarized sum rule. Application of the NNA procedure to correlators of quark vector and scalar currents, in the eu…
We consider the top-antitop invariant mass distributions for production of unpolarized and polarized top quark pairs at LHC, in the theoretical framework of the MSSM. Assuming a "moderately" light SUSY scenario, we derive the leading logarithmic electroweak contributions at one loop in a region of large invariant mass, $M_{t\bar t}\simeq1$ TeV, for the unpolarized differential cross section $dσ/dM_{t\bar t}$ and for the differential longitudinal top polarization asymmetry $A_t(M_{t\bar t})$. We perform a realistic evaluation of the expected uncertainties of the two quantities, both from a theo…
We present a detailed analysis of meson-induced massive lepton (muon) Drell--Yan production for the process $π^{-}N\toμ^{+}μ^{-}X$, considering both an unpolarized nucleon target and longitudinally polarized protons. Using a QCD framework, we focus on the angular distribution of $μ^+$, which is sensitive to the shape of the pion distribution amplitude, the goal being to test corresponding results against available experimental data. Predictions are made, employing various pion distribution amplitudes, for the azimuthal angle dependence of the $μ^{+}$ distribution in the polarized case, relevan…
Reports on our latest extractions of parton distribution functions of the nucleon are given. First an overview of the recent JR14 upgrade of our unpolarized PDFs, including NNLO determinations of the strong coupling constant and a discussion of the role of the input scale in parton distribution analysis. In the second part of the talk recent results on the determination of spin-dependent PDFs from the JAM collaboration are reported, including a careful treatment of hadronic and nuclear corrections, as well as reports on the impact of present and future data in our understanding of the spin of …
The effects of new neutral $Z^\prime$ boson in $B_{s}\toϕ\ell^{+}\ell^{-}$, when $ϕ$ is longitudinal or transverse polarized, are studied. In addition, the implications of $Z^{\prime}$ boson on the unpolarized and polarized $CP$ violation asymmetries, with reference to lepton, are also presented. It is observed that the branching ratio with polarized $ϕ$ are quite sensitive to the $Z^{\prime}$ contributions which are coming through the modification of Wilson coefficients $C^{eff}_{9}$ and $C_{10}$. Moreover, the off-diagonal elements of the chiral $Z^{\prime}$ couplings contain new weak phase …
Recent e+e- annihilation experiments show a striking spin alignment of vector mesons produced in the fragmentation of a polarized quark.We show that these data imply a simple relation between the polarization of the anti-quark, which is produced in the fragmentation process to combine with the fragmenting quark to form the meson, and that of the fragmenting quark. After having obtained a good fit to the e+e- data, we extend the calculations to lepton-nucleon and nucleon-nucleon collisions with polarized beams. We also discuss the relation between the spin alignment of vector meson in unpolariz…
The Fortran package QCD-PEGASUS is presented. This program provides fast, flexible and accurate solutions of the evolution equations for unpolarized and polarized parton distributions of hadrons in perturbative QCD. The evolution is performed using the symbolic moment-space solutions on a one-fits-all Mellin inversion contour. User options include the order of the evolution including the next-to-next-to-leading order in the unpolarized case, the type of the evolution including an emulation of brute-force solutions, the evolution with a fixed number n_f of flavours or in the variable-n_f scheme…
A survey is given of recent developments on the resummed small-$x$ evolution, in a framework based on the renormalization group equation, of non--singlet and singlet structure functions in both unpolarized and polarized deep--inelastic scattering. The available resummed anomalous dimensions are discussed for all these cases, and the most important analytic and numerical results are compiled. The quantitative effects of these small-$x$ resummations on the evolution of the various parton densities and structure functions are presented, and their present uncertainties are investigated. An applica…
The role of various symmetries in the evaluation of splitting functions and coefficient functions is discussed. The scale invariance in hard processes is known to be a guiding tool to understand the dynamics. We discuss the constraints on splitting functions coming from various symmetries such as scale, conformal and supersymmetry. We also discuss the Drell-Levy-Yan relation among splitting and coefficient functions in various schemes. The relations coming from conformal symmetry are also presented.
We summarize recent attempts to calculate the flavor asymmetry of the nucleon's sea quark distributions in the large-$N_c$ limit, where the nucleon can be described as a soliton of an effective chiral theory. We discuss the leading-twist longitudinally polarized and transversity antiquark distributions, $Δ\bar u (x) - Δ\bar d (x)$ and $δ\bar u (x) - δ\bar d (x)$, as well as the unpolarized one, $\bar u (x) - \bar d (x)$, which appears only in the next-to-leading order of the $1/N_c$-expansion. Results for $\bar u (x) - \bar d (x)$ are in good agreement with the recent Drell-Yan data from the F…
We consider the azimuthal $\cos φ$ and $\cos 2φ$ distributions and the Callan-Gross ratio $R={\rm d}σ_L/{\rm d}σ_T$ in heavy-quark pair electroproduction, $lN\rightarrow l^{\prime}Q\bar{Q}X$, as probes of linearly polarized gluons in unpolarized nucleons. Our analysis shows that the azimuthal asymmetries and Callan-Gross ratio are predicted to be large and very sensitive to the contribution of the gluonic counterpart of the Boer-Mulders function, $h_{1}^{\perp g}$, describing the linear polarization of gluons inside unpolarized nucleon. In particular, the maximum values of the azimuthal distri…
We present a decomposition of the hadronic tensor for a general polarized Drell-Yan process AB --> l^+ l^- X in terms of helicity structure functions using the helicity axes of the dilepton rest frame as a basis. Next, we consider a QCD parton model and in the framework of a generalized QCD factorization scheme, which applies when the dilepton invariant mass M is much larger than the transverse component of the photon momentum, q_T, in the hadronic center of mass frame. In this approximation we compute the angular distribution of the unpolarized Drell Yan cross section and of the Sivers effect…
Complete analytical results for the production of heavy-quark pairs by polarized and unpolarized photons in next-to-leading order are presented. Two-, three- and two plus three-jet cross sections for total photon spin $J_z=0,\pm 2$ are presented for $b\bar{b}(g)$ production. The 2-jet cross sections are considered as a background to $γγ\rightarrow H^* \rightarrow b\bar{b}$ (standard model). Top production, not too far above threshold, is also considered for $J_z=0,\pm 2$. For both $b$- and $t$-quark production, the higher order QCD corrections are found to be significant.
We calculate total and differential cross sections for the production of sfermion pairs in photon-photon collisions, including contributions from resolved photons and arbitrary photon polarization. Sfermion production in photon collisions depends only on the sfermion mass and charge. It is thus independent of the details of the SUSY breaking mechanism, but highly sensitive to the sfermion charge. We compare the total cross sections for bremsstrahlung, beamstrahlung, and laser backscattering photons to those in $e^+e^-$ annihilation. We find that the total cross section at a polarized photon co…
Color-octet contributions to the associate $J/ψ+γ$ production are found to be negligible, compared to the ordinary color-singlet contribution. Within the color-singlet model the $J/ψ+γ$ production in the leading order is possible only through gluon-gluon fusion process. Therefore, the associate $J/ψ+γ$ production remains to be useful as a clean channel to probe the unpolarized and polarized gluon distribution inside proton (and photon), and to study heavy quarkonia production mechanism. We discuss in detail the associate production of $J/ψ+γ$ at $p \overline{p}$ (or $pp$) and $ep$ colliders. B…
Linear polarization of gluons inside unpolarized hadrons affects the transverse momentum distribution of produced spin-0 particles, such as of the Higgs or (pseudo-)scalar quarkonium states at LHC. Despite the currently unknown amount of linear gluon polarization, a range of predictions can be obtained, using TMD evolution, which indicates that their effect is on the few percent level in Higgs production, but can be much larger in quarkonium production. Together with asymmetries in open charm or bottom production in electro-production at an Electron-Ion Collider, the size and sign of the linea…
The isosinglet unpolarized and isovector polarized twist-2 quark distributions of the nucleon at low normalization point are calculated in the large-Nc limit. The nucleon is described as a soliton of the effective chiral theory. We derive the expressions for the distribution functions in the large-Nc limit starting from their definition as numbers of partons carrying momentum fraction x in the infinite momentum frame. We develop a numerical method for computation of the quark and antiquark distributions as sums over the quark single-particle levels in the pion field of the soliton. The contrib…
In this paper we shall focus on the effects of concrete models such as SM and Model III of 2HDM on the polarized and unpolarized forward-backward asymmetries of $\overline{B}\rightarrow \overline{K}_0^{*}(1430) \ell^+\ell^-$ and $\overline{B}\rightarrow \overline{K} \ell^+\ell^-$ decays. The obtained results of these decay modes are compared to each other. Also, we obtain the minimum required number of events for detecting each asymmetry and compare them with the number of produced $B\bar{B}$ pairs at the LHC or supposed to be produced at the Super-LHC. At the end, we conclude that the study o…
We study the production of polarized $Λ$ hyperon in semi-inclusive deep inelastic scattering off an unpolarized target. We include the cases in which the $Λ$ hyperon is longitudinally polarized or transversely polarized, and in which the lepton beam is unpolarized or longitudinally polarized. Within the framework of the transverse momentum dependent factorization, we take into account the complete decomposition of the parton correlator for fragmentation up to twist-3. We present the cross section of the process to order $1/Q$. The expressions of the polarized structure functions, which may giv…
We study the Callan-Gross ratio $R={\rm d}σ_L/{\rm d}σ_T$ in heavy-quark pair leptoproduction, $lN\rightarrow l^{\prime}Q\bar{Q}X$, as a probe of linearly polarized gluons inside unpolarized proton, where ${\rm d}σ_T$ (${\rm d}σ_L$) is the differential cross section of the $γ^*N\rightarrow Q\bar{Q}X$ process initiated by a transverse (longitudinal) virtual photon. Note first that the maximal value for the quantity $R$ allowed by the photon-gluon fusion with unpolarized gluons is large, about 2. We calculate the contribution of the transverse-momentum dependent gluonic counterpart of the Boer-M…
Radiation emitted by unpolarized high-energy electrons penetrating crystals may be linearly polarized. This occurs when the particle velocity makes an angle, with respect to some major crystal axis, being sufficiently larger than the axial-channelling angle. For such orientation, a complete description of spectral and polarization characteristics of the radiation is derived. At planar channelling, a non-perturbative contribution to the probability of the process appears caused by the plane field, and we must solve exactly a one~-~dimensional mechanical problem. For that, the approximate form o…
A survey is given on the new 2- and 3-loop results for the heavy flavor contributions to deep-inelastic scattering in the unpolarized and the polarized case. We also discuss related new mathematical aspects applied in these calculations.
The Pauli exclusion principle is advocated for constructing the proton and neutron deep inelastic structure functions in terms of Fermi-Dirac distributions that we parametrize with very few parameters. It allows a fair description of the recent NMC data on $F^p_2(x,Q^2)$ and $F^n_2(x,Q^2)$ at $Q^2=4 GeV^2$, as well as the CCFR neutrino data at $Q^2=3$ and $5 GeV^2$. We also make some reasonable and simple assumptions to relate unpolarized and polarized quark parton distributions and we obtain, with no additional free parameters, the spin dependent structure functions $xg^p_1(x,Q^2)$ and $xg^n_…
We recall our recent description of quark parton densities of the proton at $Q^2=4 GeV^2$ in terms of Fermi-Dirac distributions parametrized with very few free parameters. We have also proposed some simple assumptions to relate unpolarized and polarized quark parton densities which lead to a fair description of the spin-dependent structure functions $xg^p_1(x,Q^2)$ and $xg^n_1(x,Q^2)$ at low $Q^2$. We will show the predictions we obtain after a straightforward DGLAP $Q^2$ evolution and comparison in a much broader $x$ and $Q^2$ range, with several recent and accurate deep-inelastic scattering …
We briefly report our recent progress on the study of the polarized fragmentation functions of $Λ$ hyperon in unpolarized semi-inclusive deep-inelastic scatterings and electron-positron annihilations at low energies. In particular, we present a simple but practical method on how to measure the azimuthal-angle-dependent longitudinal polarization and the transverse polarization inside the production plane and bridge these observables to the corresponding structure functions and fragmentation functions at the leading twist. Our work diversifies the high energy reactions that can probe the polariz…
