Two factorization approaches have been proposed for single transverse spin asymmetries. One is the cofiinear factorization, the other is the transverse-momentum-dependent factorization. They have been previously deriv...Two factorization approaches have been proposed for single transverse spin asymmetries. One is the cofiinear factorization, the other is the transverse-momentum-dependent factorization. They have been previously derived in a formal way by using diagram expansion at hadron level. If the two factorizations hold or can be proven, they should also hold when we replace hadrons with patton states. We examine these two factorizations at patton level with massless partons. It is nontrivial to generate these asymmetries at parton level with massless patrons because the asymmetries require helicity-flip and nonzero absorptive parts in scattering amplitudes. By constructing suitable patton states with massless partons we derive the two factorizations for the asymmetry in Drell-Yan processes. It is found from our results that the collinear factorization derived at parton level is not the same as that derived at hadron level. Our results with massless partons confirm those derived with single massive parton state in our previous works.展开更多
In a simple hadronie model, the two-photon exchange contributions to the single spin asymmetries for the nucleon and the 3He are estimated. The results show that the elastic contributions of two-photon exchange to the...In a simple hadronie model, the two-photon exchange contributions to the single spin asymmetries for the nucleon and the 3He are estimated. The results show that the elastic contributions of two-photon exchange to the single spin asymmetries for the nucleon are rather small while those for the 3He are relatively large. Besides the strong angular dependence, the two-photon contributions to the single transfer. spin asymmetry for the 3He are very sensitive to the momentum展开更多
A Monte Carlo model considering the electron spin direction and spin asymmetry h as been developed. The energy distribution of the secondary electron polarizatio n and the primary energy dependence of the polarization...A Monte Carlo model considering the electron spin direction and spin asymmetry h as been developed. The energy distribution of the secondary electron polarizatio n and the primary energy dependence of the polarization from Fe are studied. The simulation results show that: (1) the intensity of the spin-up secondary electr ons is larger thanvthat of thevspin-down secondary electrons, suggesting the s econdary electrons are spin polarized; (2) the spin polarization of secondary el ectrons with nearly zero kinetic energy is higher than the average valance spin polarization, Pb=27% for Fe. With increasing kinetic energy, the spin polarizat ion of the secondary electrons decreases to the value of Pb, remaining constant at higher kinetic energies; (3) the spin polarization increases with an increase in the primary energy and reaches a saturation value at higher primary energy i n both the Monte Carlo simulation and experimental results.展开更多
The anomalous magnetic(MDM)and electric(EDM)dipole moments of theτlepton serve as crucial indicators of new physics beyond the standard model.Leveraging azimuthal angular asymmetry as a novel tool in ultraperipheral ...The anomalous magnetic(MDM)and electric(EDM)dipole moments of theτlepton serve as crucial indicators of new physics beyond the standard model.Leveraging azimuthal angular asymmetry as a novel tool in ultraperipheral collisions(UPCs),we attain unparalleled precision in the study of these key properties.Driven by the highly linear polarization of coherent photons,this method uniquely enables both the MDM and EDM to contribute to the cos 2φangular distribution in similar magnitudes.Importantly,our approach substantially narrows the parameter space,excluding more than half of it compared to expected UPC-based measurements reliant solely on the total cross-section.This method not only provides improved constraints but also minimizes the need for additional theoretical assumptions,and offers a novel avenue to probe the EDM effects.展开更多
Results are presented from the Hermes experiment which uses semi-inclusive deep inelastic lepton scattering to study the flavor structure of the nucleon.Data have been accumulated for pion and kaon double spin asymmet...Results are presented from the Hermes experiment which uses semi-inclusive deep inelastic lepton scattering to study the flavor structure of the nucleon.Data have been accumulated for pion and kaon double spin asymmetries,single-spin azimuthal asymmetries for meson electroproduction,deep virtual Compton scattering （DVCS）,and meson multiplicities.These results provide information on the properties of the strange sea in the proton,constraints on transverse momentum dependent quark parton distributions,and demonstrate the promise of DVCS for isolating the total angular momentum carried by the quarks in the proton.展开更多
基金Supported by National Natural Science Foundation of China under Grant Nos. 10721063, 10575126, and 10975169
文摘Two factorization approaches have been proposed for single transverse spin asymmetries. One is the cofiinear factorization, the other is the transverse-momentum-dependent factorization. They have been previously derived in a formal way by using diagram expansion at hadron level. If the two factorizations hold or can be proven, they should also hold when we replace hadrons with patton states. We examine these two factorizations at patton level with massless partons. It is nontrivial to generate these asymmetries at parton level with massless patrons because the asymmetries require helicity-flip and nonzero absorptive parts in scattering amplitudes. By constructing suitable patton states with massless partons we derive the two factorizations for the asymmetry in Drell-Yan processes. It is found from our results that the collinear factorization derived at parton level is not the same as that derived at hadron level. Our results with massless partons confirm those derived with single massive parton state in our previous works.
文摘In a simple hadronie model, the two-photon exchange contributions to the single spin asymmetries for the nucleon and the 3He are estimated. The results show that the elastic contributions of two-photon exchange to the single spin asymmetries for the nucleon are rather small while those for the 3He are relatively large. Besides the strong angular dependence, the two-photon contributions to the single transfer. spin asymmetry for the 3He are very sensitive to the momentum
基金This work was supported by the National Natural Science Foundation of China(No.10025420,No.60306006 and No.90206009).
文摘A Monte Carlo model considering the electron spin direction and spin asymmetry h as been developed. The energy distribution of the secondary electron polarizatio n and the primary energy dependence of the polarization from Fe are studied. The simulation results show that: (1) the intensity of the spin-up secondary electr ons is larger thanvthat of thevspin-down secondary electrons, suggesting the s econdary electrons are spin polarized; (2) the spin polarization of secondary el ectrons with nearly zero kinetic energy is higher than the average valance spin polarization, Pb=27% for Fe. With increasing kinetic energy, the spin polarizat ion of the secondary electrons decreases to the value of Pb, remaining constant at higher kinetic energies; (3) the spin polarization increases with an increase in the primary energy and reaches a saturation value at higher primary energy i n both the Monte Carlo simulation and experimental results.
基金supported by the National Natural Science Foundation of China(Grant Nos.12275052,and 12147101)supported by the National Natural Science Foundation of China(Grant Nos.11725520,11675002,and 12235001)+1 种基金Shanghai Natural Science Foundation(Grant No.21ZR1406100)supported by the Institute of High Energy Physics(Contract No.E25153U1)。
文摘The anomalous magnetic(MDM)and electric(EDM)dipole moments of theτlepton serve as crucial indicators of new physics beyond the standard model.Leveraging azimuthal angular asymmetry as a novel tool in ultraperipheral collisions(UPCs),we attain unparalleled precision in the study of these key properties.Driven by the highly linear polarization of coherent photons,this method uniquely enables both the MDM and EDM to contribute to the cos 2φangular distribution in similar magnitudes.Importantly,our approach substantially narrows the parameter space,excluding more than half of it compared to expected UPC-based measurements reliant solely on the total cross-section.This method not only provides improved constraints but also minimizes the need for additional theoretical assumptions,and offers a novel avenue to probe the EDM effects.
文摘Results are presented from the Hermes experiment which uses semi-inclusive deep inelastic lepton scattering to study the flavor structure of the nucleon.Data have been accumulated for pion and kaon double spin asymmetries,single-spin azimuthal asymmetries for meson electroproduction,deep virtual Compton scattering （DVCS）,and meson multiplicities.These results provide information on the properties of the strange sea in the proton,constraints on transverse momentum dependent quark parton distributions,and demonstrate the promise of DVCS for isolating the total angular momentum carried by the quarks in the proton.
