Quark helicity distributions in transverse momentum space and transverse coordinate space

The transverse momentum dependent helicity distributions of valence quarks are calculated in the light-cone diquark model by adopting two different approaches. We use the model results to analyze the $P_{h\perp}$-dependent double spin asymmetries for $\pi^+$, $\pi^-$ and $\pi^0$ productions in semi-inclusive deep inelastic scattering, and find that the asymmetries agree with the CLAS data in one of the approaches. By taking the Fourier transform of the transverse momentum dependent helicity distributions, we obtain the helicity distributions of valence quarks in the transverse coordinate space, and then apply them further to predict the Bessel-weighted double spin asymmetries of $\pi^+$, $\pi^-$ and $\pi^0$ productions in semi-inclusive deep inelastic scattering at CLAS, COMPASS and HERMES for the first time. The shape of the Bessel-weighted double spin asymmetry thereby provides a direct probe on the transverse structure of longitudinally polarized quarks.Comment: References added, version published in PR

EMC effect in semi-inclusive deep-inelastic scattering process

By considering the $x$-dependence of $\pi^+$, $\pi^-$, $K^+$, $K^-$, $\Lambda$, $\bar{\Lambda}$, $p$, $\bar{p}$ hadron productions in charged lepton semi-inclusive deep inelastic scattering off nuclear target (using Fe as an example) and deuteron D target, % at $Q^2=5$ GeV$^2$, we find that $(\bar{\Lambda}^A/\Lambda^A)/(\bar{\Lambda}^D/\Lambda^D)$ and $({\bar{p}}^A/{p}^A)/({\bar{p}}^A/p^A)$ are ideal to figure out the nuclear sea content, which is predicted to be different by different models accounting for the nuclear EMC effect.Comment: 21 latex pages, 15 figure

On the cos 2 phi asymmetry in unpolarized leptoproduction

We investigate the origin of the cos 2 phi azimuthal asymmetry in unpolarized semiinclusive DIS. The contributions to this asymmetry arising from the intrinsic transverse motion of quarks are explicitly evaluated, and predictions for the HERMES and COMPASS kinematic regimes are presented. We show that the effect of the leading-twist Boer-Mulders function h_1^perp(x, k_T^2), which describes a correlation between the transverse momentum and the transverse spin of quarks, is quite significant and may also account for a part of the cos 2 phi asymmetry measured by ZEUS in the perturbative domain.Comment: 11 pages, 7 figure

The sin⁡2ϕ\sin2\phi azimuthal asymmetry in single longitudinally polarized πN\pi N Drell-Yan process

We study the $\sin2\phi$ azimuthal asymmetry in the $\pi N$ Drell-Yan process, when the nucleon is longitudinally polarized. The asymmetry is contributed by the combination of the Boer-Mulders function and the longitudinal transversity distribution function. We consider the Drell-Yan processes by $\pi^\pm$ beams colliding on the proton and deuteron targets, respectively. We calculate the $\sin2\phi$ azimuthal asymmetries in these processes using the Boer-Mulders function and the longitudinal transversity from spectator models. We show that the study on single polarized $\pi N$ Drell-Yan processes can not only give the information on the new 3-dimensional parton distribution functions in momentum space, but also shed light on the chiral-odd structure of the longitudinally polarized nucleon.Comment: 7 pages, 3 figures. Final version for publication in PR

Transverse single-spin asymmetries of pion production in semi-inclusive DIS at subleading twist

We study the single-spin asymmetries with the $\sin\phi_S$ and $\sin(2\phi_h -\phi_S)$ angular dependences for charged and neutral pions produced in semi-inclusive deep inelastic scattering on the transversely polarized proton target. The theoretical interpretations of the two asymmetries are presented in terms of the convolution of the twist-3 quark transverse momentum dependent distributions and twist-2 fragmentation functions. Specifically, we investigate the role of the distributions $f_T$, $h_T$ and $h_T^\perp$ in the $\sin\phi_S$ asymmetry, as well as the role of the distributions $f_T^\perp$, $h_T$ and $h_T^\perp$ in the $\sin(2\phi_h -\phi_S)$ asymmetry. We calculate these distributions in a spectator-diquark model and predict the corresponding asymmetries for the first time, considering the kinematics at HERMES, JLab and COMPASS. The numerical estimates show that the asymmetries are sizable, and the dominant contribution to the $\sin\phi_S$ asymmetry comes from the T-odd distribution $f_T$, while $f_T^\perp$ gives the main contribution to the $\sin(2\phi_h -\phi_S)$ asymmetry. The future measurements on these asymmetries can shed light on the information of twist-3 transverse momentum dependent distributions.Comment: 11 pages, 12 figures, version published in PR

Transverse spin effects of sea quarks in unpolarized nucleons

We calculate the non-zero Boer-Mulders functions of sea quarks inside the proton in a meson-baryon fluctuation model. The results show that the transverse spin effects of sea quarks in an unpolarized nucleon are sizable. Using the obtained antiquark Boer-Mulders functions, we estimate the $\cos 2 \phi$ asymmetries in the unpolarized $pp$ and $p D$ Drell-Yan processes at FNAL E866/NuSea experiments. The prediction for the $\cos 2 \phi$ asymmetries in the unpolarized $pp$ Drell-Yan process at the BNL Relativistic Heavy Ion Collider (RHIC) is also given.Comment: 7 pages, 5 figures, to appear in Physical Review

Unitarity bounds on extensions of Higgs sector

It is widely believed that extensions of the minimal Higgs sector is one of the promising directions for resolving many puzzles beyond the Standard Model (SM). In this work, we study the unitarity bounds on the models by extending the two-Higgs-doublet model with an additional real or complex Higgs triplet scalar. By noting that the SM gauge symmetries $SU(2)_L\times U(1)_Y$ are recovered at high energies, we can classify the two-body scattering states by decomposing the direct product of two scalar multiplets into their direct sum of irreducible representations of electroweak gauge groups. In such state bases, the s-wave amplitudes of two-body scalar scatterings can be written in the form of block-diagonalized scattering matrices. Then the application of the perturbative unitarity conditions on the eigenvalues of scattering matrices leads to the analytic constraints on the model parameters. Finally, we numerically investigate the complex triplet scalar extension of the two-Higgs-doublet model, finding that the perturbative unitarity places useful stringent bounds on the model parameter space.Comment: 30 pages, 2 figures