p-A Drell-Yan Process in the Target Rest Frame

At high energies, Drell-Yan process can be viewed in the target rest frame as bremsstrahlung of massive photons, rather than parton annihilation. In this paper, the ratio of the p-A Drell-Yan cross section per nucleon for an 800 GeV proton beam incident on Fe, W, and Be targets are calculated by means of the color dipole approach in the target rest system. It is shown that our calculations can quite well fit the Fermilab E866 experimental data with considering the nuclear shadowing effect in p-A Drell-Yan process and without the energy loss effect in it.     

πp Drell-Yan Process in Color Dipole Model

We study pion-proton (πp) Drell-Yan (DY) dilepton production in the target rest frame with color dipole model. The prediction for πp DY cross section at the energies of RHIC and LHC is presented, and it can be compared with the data directly, because it does not need K factor. At the same time, the transverse momentum distribution is shown in quantities, which is not available from the standard parton model. The experimental studies of the process could test the color model for DY dilepton production.     

Inhomogeneous Shadowing Effect in High-Energy p-A Drell-Yan Process

Having studied the initial state energy loss versus nuclear shadowing for the Drell-Yan dimuon pair production in the color string model, the inhomogeneous shadowing effect is considered in this paper. We find that the inhomogeneous shadowing effect does amend the rate of energy loss per unit path length, -dE/dz. Finally, the theoretical results for the Drell-Yan differential cross-section ratios are compared with the E772 and E866 data. It is found that the theoretical results are in good agreement with the experimental data.     

p-A Drell-Yan过程中的核效应

利用色偶极模型,在靶静止系中计算了800GeV质子与原子核碰撞的Drell-Yan过程的微分截面,并与E772实验结果进行了比较.结果发现:不考虑能量损失,只计及p-A碰撞中的核遮蔽效应,理论计算就与实验数据甚好符合.     

高能p-A碰撞Drell-Yan过程中的初态核效应

核遮蔽和能量损失效应是p-A碰撞中两种重要的初态核效应. 本文利用从轻子-原子核深度非弹性散射实验数据中抽取的束缚核子的部分子分布函数, 在色弦模型中研究了Drell-Yan双轻子对产生过程中的能量损失效应. 通过对FNAL E772和E866实验数据的χ²分析, 得到夸克在冷核中的能量损失率为－dE/dz=2.06GeV/fm. 这和该模型理论预言的结果(－dE/dz～2GeV/fm)一致. 通过将理论计算结果与实验数据进行比较, 发现考虑到能量损失后能很好的解释实验现象.     

核Drell–Yan过程中的能量丢失现象

在考虑EMC效应的基础上进一步考虑了入射强子的能量丢失现象,用部分子演化模型预见核Drell-Yan过程,效果明显改进.     

On K-Factor's Non-Constancy for the Drell-Yan Process in Carbon-Carbon Nuclear Collision

The double Q²-rescaling model is used to compute the change of K-factor with x_A2 when the nucleus carbon-nucleus carbon collision occurs at different values of x_Al, where x are momentum fraction variables. In the calculation, the contributions of annihilations and Compton scattering have been considered for the Drell-Yan process. The calculated results show that the plots of K-factor versus X_A2 are very different for different values of x_Al. They are also compared with experimental data, which provides a test to the model of nuclear effect and the QCD theory itself     

Non-perturbative QCD Effect on K-Factor of Drell-Yan Process

By using a non-perturbative quark propagator with the lowest-dimensional condensate contributions from the QCD vacuum, the non-perturbative effect to K-factor of the Drell-Yan process is numerically investigated for ¹²₆C-¹²₆C collision at the center-of-mass energy √{s}=200 GeV, 630 GeV respectively. Calculated results show that the non-perturbative QCD effect has just a weak influence on K-factor in the two cases.     

Chargino-Pair Productions via Drell-Yan Process at the LHC

We present the analytical and numerical investigations of chargino-pair productions via Drell-Yan process a t proton-proton collider in the frame of minimal supersymmetric extension at tree level. For the χ_i⁺χ_j^-(i,j= 1,2) pair productions at the LHC, the cross section is in the order of 3～2.5 ×10^-3 pb. We find that the cross sections of all kinds of chargino-pair production processes are strongly related to the SUSY Lagrangian parameters M₂ and μ.     

高能核–核碰撞Drell–Yan过程K因子常数性的研究

在高能核–核碰撞Drell-Yan过程考虑湮没项和康普顿散射项的基础上,利用双重Q²重标度模型,分别计算了碳、钙、铁、锡与其自身的核–核碰撞.结果表明,对于不同的x₁值,K因子随x₂的变化很不相同;同时,K因子变化的幅度是随核素A不同而发生微弱变化的,在特定的x₁,x₂取值有限范围内它不能近似取为常数.计算结果与实验的对比是对所用模型及QCD理论适用性的一种检验.     

A Proof of Factorization Theorem of Drell–Yan Process at Operator Level

An alternative proof of factorization theorem for Drell–Yan process that works at operator level is presented in this paper. Contributions of interactions after the hard collision for such inclusive processes are proved to be canceled at operator level according to the unitarity of time evolution operator. After this cancellation, there are no longer leading pinch singular surface in Glauber region in the time evolution of electromagnetic currents. Effects of soft gluons are absorbed into Wilson lines of scalar-polarized gluons. Cancelation of soft gluons is attribute to unitarity of time evolution operator and such Wilson lines.     

改进的部分子演化模型及其对EMC效应和核Drell－Yan过程的解释

用解析方法证明了部分子演化模型可为双重Ｘ重新标度模型提供物理基础，进而利用修正的Ａｌｔｅｒａｌｌｉ－Ｐａｒｉｓｉ方程描述小ｘ区域的核遮蔽和反遮蔽效应，以改进部分子演化模型，使我们不必引入核遮蔽因子便可统一地描述ＥＭＣ效应、核遮蔽和反遮蔽效应．最后，利用改进的部分子演化模型相当好地解释了核Ｄｒｅｌｌ－Ｙａｎ过程的实验数据．     

Inhomogeneous Shadowing Effect in High-Energy p-A Drell-Yan Process

Having studied the initial state energy loss versus nuclear shadowing for the Drell- Yan dimuon pair production in the color string model, the inhomogeneous shadowing effect is considered in this paper. We find that the inhomogeneous shadowing effect does amend the rate of energy loss per unit path length, -dE/ dz. Finally, the theoretical results for the Drell Yan differential cross-section ratios are compared with the E772 and E866 data. It is found that the theoretical results are in good agreement with the experimental data.     

改进的核密度模型与强子-核Drell-Yan过程中的核效应

提出了改进的核密度模型，用唯象的方法找到了束缚核子内价夸克和海夸克的核效应的参数公式，其中利用了核密度与原子核的平均结合能之间的联系. 利用该模型所得到的束缚核子内部分子分布函数，对强子与核的Drell-Yan过程的核效应给出了满意的解释, 深化了对原子核内夸克分布受核效应影响的认识. 关键词： 核密度模型 核效应 强子-核Drell-Yan过程     

微扰QCD对Drell-Yan过程能量损失效应的修正

利用Glauber模型以及DGLAP方程下的核内核子的部分子分布函数, 在次领头阶QCD下计算了Drell-Yan过程中的能量损失效应, 计算表明QCD修正并不能改善理论结果与试验结果的符合, 尤其是p-W与p-Be以x₁为变量的微分截面比. 原因是所用的核内核子部分子的分布函数是以领头阶近似为基础并通过演化方程得到的. 于是利用在次领头阶微扰QCD下得到的核遮蔽效应核内核子的部分子分布函数重新计算了次领头阶QCD修正对Drell-Yan过程能量损失的贡献. 计算结果表明康普顿散射过程与湮没过程中应该有更多的能量损失.     

Quark Energy Loss and Shadowing in Nuclear Drell-Yan Process

The energy loss effect in nuclear matter is another nuclear effect apart from the nuclear effects on the parton distribution as in deep inelastic scattering process. The quark energy loss can be measured best by the nuclear dependence of the high energy nuclear Dre11-Yan process. By means of three kinds of quark energy loss parameterizations given in literature and the nuclear parton distribution extracted only with lepton-nucleus deep inelastic scattering experimental data, measured Dre11-Yan production cross sections are analyzed for 800 GeV proton incident on a variety of nuclear targets from FNAL E866. It is shown that our results with considering the energy loss effect are much different from those of the FNAL E866, who analyzes the experimental data with the nuclear parton distribution functions obtained by using the deep inelastic IA collisions and pA nuclear Drell-Yan data. Considering the existence of energy loss effect in Drell-Yan lepton pairs production, we suggest that the extraction of nuclear parton distribution functions shoul““““d not include Dre11-Yan experimental data.     

Quark Energy Loss and Shadowing in Nuclear Drell-Yan Process

The energy loss effect in nuclear matter is another nuclear effect apart from the nuclear effects on the parton distribution as in deep inelastic scattering process. The quark energy loss can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of three kinds of quark energy loss parameterizations given in literature and the nuclear parton distribution extracted only with lepton-nucleus deep inelastic scattering experimental data, measured Drell-Yan production cross sections are analyzed for 800 GeV proton incident on a variety of nuclear targets from FNAL E866. It is shown that our results with considering the energy loss effect are much different from those of the FNAL E866, who analyzes the experimental data with the nuclear parton distribution functions obtained by using the deep inelastic IA collisions and pA nuclear Drell-Yan data. Considering the existence of energy loss effect in Drell-Yan lepton pairs production, we suggest that the extraction of nuclear parton distribution functions should not include Drell-Yan experimental data.     

Associated production of one particle and a Drell-Yan pair in hadronic collisions

We propose a collinear factorization formula for the associated production of one particle and a Drell-Yan pair in hadronic collisions. It is shown that additional collinear singularities appearing in the next-to-leading order calculations that cannot be factorized into parton and fragmentation functions are systematically renormalized by introducing fracture functions. Next-to-leading order coefficient functions for cross-sections double differential in the fractional energy of the identified hadron and lepton pair invariant mass are presented.     

Drell-Yan dilepton production in relativistic heavy-ion collisions at RHIC

We investigate the lepton pair production with the Drell-Yan process in relativistic heavy ion collisions by computing the double differential cross section dσ/dM²dy and dσ/dM²dx_F at the next-to-leading order in p+Au and Au+Au collisions with √s_NN =200 GeV at RHIC. The resulting nuclear modification factors R^pAu and R^AuAu show strong sensitivity to the cold nuclear matter (CNM) effects and could probe the CNM effects at a very wide region of the longitudinal momentum fraction x. The variation of R with the invariant mass M, the rapidity y and the Feynman variable x_F is shown and we find that the nuclear modification factor for the double differential cross section could be smaller than 0.4 in some kinematic regions of high-energy nucleus-nucleus reactions at RHIC.     

Colour effects in Drell-Yan process

We examine the predictions of gauge theories with colour excitation for the processpp →μ ⁺ μ ⁻ X. Relative to the predictions of quark parton model (with three colours) we find enhancements as large as a factor 3 – 4 for the cross-sectionM ³ d ² σ/dMdy|_y=0 in the region 0·03 ≲M/√s ≲ 0·2 at √s=62 GeV,M being the invariant mass andy the rapidity of the muon pair. We study the sensitivity of this result to the colour gluon mass and the underlying parametrisation of the quark and gluon distribution functions.