We examine the single-spin asymmetry (SSA) caused by the five-quark components of the proton for semi-inclusive electroproduction of charged pions in deep-inelastic scattering on a transversely polarized hydrogen target. The large SSA is considered to have close relation with quark orbital motion in the proton and suggests that the quark orbital angular momentum is nonzero. For the five-quark $qqqq\bar{q}$ components of the proton, the lowest configurations with $qqqq$ system orbitally excited and the $\bar{q}$ in the ground state would give spin-orbit correlations naturally for the quarks in a polarized proton. We show that based on the basic reaction $γq \to πq'$, the orbital-spin coupling of the probed quarks in the five-quark configuration leads to the single-spin asymmetry consistent with recent experiment results.
Within the collinear twist-3 framework, we study the single-spin asymmetry (SSA) in collisions between unpolarized protons and transversely polarized protons with focus on the fragmentation term. The fragmentation mechanism must be analyzed in detail in order to unambiguously determine the impact of various contributions to SSAs in hadron production. Such a distinction may also settle the "sign mismatch" between the transverse SSA in proton-proton collisions and the Sivers effect in semi-inclusive deep inelastic scattering. We calculate terms involving quark-quark and quark-gluon-quark correla…
Double-spin asymmetry in elastic proton-proton scattering as a probe for the Odderon
极化质子弹性散射中的双自旋不对称性A_{NN}的大小是利用先前确定的领先Regge极的自旋翻转耦合的结果来估计的（参见图1）。T.L.Trueman，Proceedings of the 16th International Spin Physics Symposium SPIN 2004，eds. F. Bradamante等人，World Scientific，2005.）所需的Regge削减估计使用吸收Regge模型。这个估计，然后用来确定在RHIC的实验的灵敏度的存在下的Odderon。
The influence of the hard photon emission on the charge asymmetry in the (anti)lepton-proton elastic scattering was evaluated for the first time beyond the ultrarelativistic limit, while retaining the lepton mass at all steps of the calculation. This contribution - responsible for the charge asymmetry - is induced by interference between real photon emission from the lepton and proton. During the calculation any excited states of the intermediated proton are not considered, allowing us to use the standard fermionic propagator for this particle. The infrared divergence extracted using Lorenz-in…
We present model predictions of Collins asymmetries for proton in the SIDIS process for $π^+$ and $π^-$ channels. We use a recently proposed light-front quark-diquark model for proton with the light-front wave functions predicted in soft-wall AdS/QCD. The model predictions are compared with the HERMES and COMPASS data.
We estimate the beam-normal single-spin asymmetry in elastic lepton-proton scattering without employing the ultrarelativistic approximation. Our calculation is relevant for analyses of muon scattering at energies of few hundred MeV and below -- when effects of the muon mass become essential. At such energies, the transverse polarization of the muon beam is expected to contribute significantly to the systematic uncertainty of precision measurements of elastic muon-proton scattering. We evaluate such systematics using an example of the MUSE experiment at PSI. The muon asymmetry is estimated at a…
We compute the single-spin asymmetry $A_{UL}$ in semi-inclusive deep-inelastic scattering of unpolarized leptons and longitudinally polarized protons at large transverse momentum of the produced hadron. Our calculation is performed in collinear factorization at the lowest order of QCD perturbation theory. For photon exchange the asymmetry is T-odd and receives contributions from the interference of the tree level and one-loop absorptive amplitudes. We consider the behavior of the spin asymmetry at low transverse momentum where contact to the formalism based on transverse-momentum dependent dis…
We study the single spin asymmetry in the transversely polarized proton production and the lambda hyperon production in semi-inclusive deep inelastic scattering with a $\sin ϕ_{S_h}$ modulation, in which $S_h$ is the azimuthal angle of the transverse spin of the final hadron. The theoretical interpretation for the asymmetry is presented as the convolution of the twist-3 quark transverse momentum dependent distributions and twist-2 fragmentation functions. We investigate the role of the twist-3 distribution functions $h(x, p_T^2)$, $f^\perp(x, p_T^2)$ and $g^\perp(x, p_T^2)$ and the twist-2 fra…
This study focuses on hard diffractive events produced in proton-proton collision at LHC exhibiting one intact proton in the final state which can be tagged by forward detectors. We report prospective results on the W boson charge asymmetry measured for such events, which allow to constrain the quark diffractive density functions in the Pomeron.
A new approach is proposed to describe the parity violation in the process of scattering of a polarized proton by a proton at high energies. It is shown that in the tree approximation the P-odd amplitude of proton-proton scattering is substantially smaller than the P-odd amplitude in proton-neutron scattering. The main source of P-odd asymmetry in proton-proton scattering is radiative corrections due to the charge-exchange strong interaction. We predict that the asymmetry in the inelastic cross section is substantially less than the asymmetry in the elastic cross section.
We study two experimental ways to measure the heavy-quark content of the proton: using the Callan-Gross ratio $R(x,Q^2)=F_L/F_T$ and/or azimuthal $\cos(2φ)$ asymmetry in deep inelastic lepton-nucleon scattering. Our approach is based on the perturbative stability of the QCD predictions for these two quantities. We resume the mass logarithms of the type $α_{s}\ln\left( Q^{2}/m^{2}\right)$ and conclude that heavy-quark densities in the nucleon can, in principle, be determined from data on the Callan-Gross ratio and/or azimuthal asymmetry. In particular, the charm content of the proton can be mea…
We compute the light antiquark flavor asymmetry in the proton using the Chiral Quark Model ($χ_{\rm QM}$). The distribution functions for the light antiquarks $\bar{d}(x)$ and $\bar{u}(x)$ have been extracted with the help of experimental data from NuSea/E866 and HERMES for the Bjorken$-x$ range $0.015 < x < 0.35$ as well from the most recent SeaQuest data for an extended $x$ range $0.13 < x < 0.45$. Our results on the $\bar{d}(x)-\bar{u}(x)$, $\frac{\bar{d}(x)}{\bar{u}(x)}$ and Gottfried Integral $I_G$ are in agreement with the experimental data and confirm the presence of enhanced $\bar{d}$ …
Single-spin asymmetry from pomeron-odderon interference
在高能质子-质子碰撞p^ \uparrow p \to pi X中观察到的横向单自旋不对称性A_N随着π介子的动量分数x_F的增加而增加，最大测量值x_PDMATHABMO为0.8，其中A_N为\simeq 40%.我们考虑的可能性，不对称性是由于非微扰产生的自旋翻转耦合在目标质子上的软再散射。我们证明了使用微扰理论，一个非零的不对称性，可以通过偶数和奇数电荷共轭提供的螺旋翻转和非翻转耦合之间的交流产生的干扰。因此，Pomeron和odderon交换可以解释能量独立的不对称性，并预测，不对称性应该坚持在大的快度差距的事件。
The study of $ s-\bar s $ asymmetry is essential to better understand of the structure of nucleon and also the perturbative and nonperturbative mechanisms for sea quark generation. Actually, the nature and dynamical origins of this asymmetry have always been an interesting subject to research both experimentally and theoretically. One of the most powerful models can lead to $ s-\bar s $ asymmetry is the meson-baryon model (MBM). In this work, using a simplified configuration of this model suggested by Pumplin, we calculate the $ s-\bar s $ asymmetry for different values of cutoff parameter $Λ$…
A striking prediction of several extensions of the constituent quark model, including the unquenched quark model, the pion cloud model and the chiral quark model, is a proportionality relationship between the quark sea asymmetry and the orbital angular momentum of the proton. We investigate to which extent a relationship of this kind is corroborated by the experiment, through a systematic comparison between expectations based on models and predictions obtained from a global analysis of hard-scattering data in perturbative Quantum Chromodynamics. We find that the data allows the angular momentu…
Predictions for hadron polarizations and left-right asymmetry in inclusive reactions involving photons
一个唯象模型，其中有一些成功的解释极化现象和左右不对称的包容性质子-质子散射被认为是涉及光子的反应。特别地，考虑了反应（a）$ γ+ p \to H + X;$（b）$γ+ p (\uparrow) \to π^{\pm} + X $和（c）$p(\uparrow) + p \to γ+ X$，其中$γ=$分辨光子和超子$ H = Λ^0, Σ^{\pm}$等。（a）中超子极化的预测和（b）和（c）中的不对称性提供了对该特定模型的进一步检验。简要讨论了在HERA观测（b）的可行性和海水极化对$p (\uparrow) + p \to π^{\pm} + X$质子的影响。
The charge asymmetry due to higher-order QED corrections in elastic lepton-proton scattering is estimated without employing the ultrarelativistic approximation. Our calculation is performed by generalizing the soft-photon approximation approach suggested by Tsai. Corresponding loop integrals that take a form of Passarino-Veltman scalar three-point functions are calculated analytically without neglecting the mass of the lepton. Our results provide model-independent charge asymmetry predictions for scattering of unpolarized and massive leptons on proton targets. These predictions can be used in …
We present a recent calculation of the transverse momentum dependent gluon distributions inside unpolarised protons and show how the ratio of the linearly polarized and the unpolarized gluon distribution in the proton can be probed by looking at $Cos(2ϕ_h)$ asymmetry in $J/ψ$ production in unpolarized $ep$ collision. We use NRQCD for estimating $J/ψ$ production and include contributions both from color singlet and color octet states.
