共查询到19条相似文献,搜索用时 125 毫秒
1.
计算了由准相干双光子相互作用导致的低横动量双轻子产生。 对于不同的质量范围, 准相干双光子相互作用在低横动量区域都很重要。 将计算结果与相对论重离子对撞机RHIC的PHENIX实验数据进行比较, 发现随着双轻子不变质量的增加, 准相干双光子过程的修正作用会更加明显。 相似文献
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通过考虑喷注淬火效应,分析了相对论性高能重离子碰撞中双强子的产生.结果表明,喷注淬火压低了大不变质量谱和大横动量的双强子的产生.与质子–质子碰撞的情形类似,核–核的擦边碰撞(碰撞参数很大)产生的强子有很强的背靠背的关联.在核–核对心碰撞(碰撞参数很小)中,由于喷注穿过强作用物质导致的喷注淬火介质效应,产生的强子的背靠背的关联几乎消失. 相似文献
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研究了RHIC和LHC能区的Au-Au和Pb-Pb周边重离子碰撞中,来自光子-核子相互作用产生的大横动量双轻子。利用微扰QCD 参数化和Weizs?cker-Williams近似计算了双轻子的产率。经过与领头阶和碎裂过程的双轻子产生数值计算结果相比较,光-核碰撞过程产生的大横动量双轻子在RHIC能区是可忽略的。但是在LHC能区,光-核碰撞在大横动量区域是周边重离子碰撞的一个重要的双轻子源。 相似文献
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在e-A深度非弹性散射过程中, 喷注穿过冷核介质时, 多重散射诱导胶子辐射会导致对碎裂函数的修正及喷注的能量损失.前期研究中关于计算e-A深度非弹性散射中胶子辐射振幅的两种方法: 螺旋振幅近似和微扰QCD严格计算都异常繁杂.
本文发展了一种新的方法, 可以方便计算出多重散射导致胶子辐射的振幅, 得到的碎裂函数的修正以及能量损失与严格计算的结果一致. 相似文献
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用蒙特卡洛模拟Jetset 7.4产生质心能量为91.2GeV的正负电子对撞事件. 在引入喷注的圆锥角后, 对不同味的夸克喷注和由不同味夸克发射的胶子产生的喷注的角分布特性进行了仔细研究. 结果发现, 在相同的能量下, 胶子喷注的角分布范围比夸克喷注的角分布范围要明显宽一些. 在带电粒子数、横动量相同的条件下, 胶子喷注的平均圆锥角比夸克喷注的平均圆锥角大很多. 喷注的平均圆锥角随带电多重数以及喷注的横动量的分布都呈线性正关联. 由不同味的夸克发射的胶子产生的喷注的圆锥角分布特性相同;而不同味的夸克喷注的圆锥角分布存在明显的差异. 相似文献
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夸克胶子喷注的人工神经网络识别研究 总被引:3,自引:0,他引:3
为了将人工神经网络用于高能物理中对喷注的分类识别,用从高能正负电子对撞的蒙特卡洛模拟中得到的不对称三喷注事件中的夸克喷注和胶子喷注的平均多重数、平均横动量和两类喷注所对的夹角的平均值作为输入BP神经网络的3个特征参量,对2?.5—2?2?.5GeV能区的8个能量间隔进行等精度的训练.用训练好的神经网络模型对不对称三喷注事件中的夸克喷注和胶子喷注样本进行检验判定,并对混合喷注样本进行分类识别.所得结果表明,有望将人工神经网络用于高能正负电子对撞产生的喷注的分类分析. 相似文献
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Hanzhong Zhang Zhongbo Kang Ben-Wei Zhang Enke Wang 《The European Physical Journal C - Particles and Fields》2010,67(3-4):445-454
Using the opacity expansion technique we investigate the photon radiation and dilepton production induced by multiple rescattering as an energetic parton jet passing through the strong interacting medium. The real photon radiation and dilepton invariant-mass spectra of the bremsstrahlung contribution from an energetic quark jet are presented. The leading contribution of total energy loss by photon emission in the medium of a high energetic quark jet is found to be proportional to the jet energy and has a linear dependence on the thickness of the nuclear target. The rescattering contribution to the dilepton production is important only when the pair has a small invariant mass and the jet has relatively low energy. The contribution fraction of the dilepton induced by rescattering in medium is found to be nearly a constant when the ratio of the jet energy to Debye screening mass E/μ is large. 相似文献
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We investigate the cold nuclear matter (CNM) effects on dijet productions in high-energy nuclear collisions at LHC with the
next-to-leading order perturbative QCD. The nuclear modifications for dijet angular distributions, dijet invariant mass spectra,
dijet transverse momentum spectra and dijet momentum imbalance due to CNM effects are calculated by incorporating EPS, EKS,
HKN and DS parametrization sets of parton distributions in nucleus. It is found that dijet angular distributions and dijet
momentum imbalance are insensitive to the initial-state CNM effects and thus provide optimal tools to study the final-state
hot QGP effects such as jet quenching. On the other hand, the invariant mass spectra and the transverse momentum spectra of
dijet are generally enhanced in a wide region of the invariant mass or transverse momentum due to CNM effects with a feature
opposite to the expected suppression because of the final-state parton energy loss effect in the QGP. The difference of EPS,
EKS, HKN and DS parametrization sets of nuclear parton distribution functions is appreciable for dijet invariant mass spectra
and transverse momentum spectra at p+Pb collisions, and becomes more pronounced for those at Pb+Pb reactions. 相似文献
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High-energy collisions of various nuclei, so called “Little Bangs” are observed in various experiments of heavy ion colliders. The time evolution of the strongly interacting quark-gluon plasma created in heavy ion collisions can be described by hydrodynamical models. After expansion and cooling, the hadrons are created in a freeze-out. Their distribution describes the final state of this medium. To investigate the time evolution one needs to analyze penetrating probes, such as direct photon or dilepton observables, as these particles are created throughout the evolution of the medium. In this paper we analyze an 1+3 dimensional analytic solution of relativistic hydrodynamics, and we calculate dilepton transverse momentum and invariant mass distributions. We investigate the dependence of dilepton production on time evolution parameters, such as emission duration and equation of state. Using parameters from earlier fits of this model to photon and hadron spectra, we compare our calculations to measurements as well. The most important feature of this work is that dilepton observables are calculated from an exact, analytic, 1+3D solution of relativistic hydrodynamics that is also compatible with hadronic and direct photon observables. 相似文献
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C. Mironov P. Constantin G.J. Kunde 《The European Physical Journal C - Particles and Fields》2007,49(1):19-22
We present simulation studies of a possible jet measurement at LHC using the leptonic decay of a high transverse momentum
virtual photon/Z0 in association with a quark/gluon jet. The interested production channels are q+q̄→Z0/γ*+g and g+q→Z0/γ*+q with the subsequent Z0/γ*→μ-+μ+ decay. The total energy of the jet is highly correlated to that of the dilepton coming from the Z0/γ* decay. The jet can be considered in this case as tagged (i.e. a dilepton-tag) with a known energy. Based on momentum balance
between the dilepton (whose energy is not modified by the medium) and the jet (which does suffer energy loss in the medium),
the angular correlation analysis that we plan to perform can shed light on the properties of the medium traversed (e.g. density)
and parton fragmentation functions. 相似文献
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R.L. Thews 《Physics letters. [Part B]》1981,100(4):339-341
Previous work on properties of dilepton angular distributions which are independent of parton distribution functions is extended to include scalar gluons. For moderate dilepton transverse momentum and large mass, the three measurable coefficients are quite sensitive to the gluon spin. Results are presented for both the annihilation and Compton scattering processes. 相似文献
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C. Adloff et al. 《The European Physical Journal C - Particles and Fields》2000,13(3):397-414
The triple-differential dijet cross-section, , is measured with the H1 detector at HERA as a function of the photon virtuality , the fraction of the photon's momentum carried by the parton entering the hard scattering, , and the square of the mean transverse energy, , of the two highest jets. Jets are found using a longitudinal boost-invariant clustering algorithm in the center of mass frame. The measurements cover the ranges GeV in virtuality and in inelasticity y. The results are well described by leading order QCD models which include the effects of a resolved component to the virtual
photon. Models which treat the photon as point-like fail to describe the data. An effective leading order parton density for
the virtual photon is extracted as a function of the photon virtuality, the probing scale and the parton momentum fraction.
The and probing scale dependences of the parton density show characteristic features of photon structure, and a suppression of
this structure with increasing is seen.
Received: 18 December 1998 / Published online: 25 February 2000 相似文献
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K. Gallmeister B. Kämpfer O.P. Pavlenko 《The European Physical Journal C - Particles and Fields》1999,8(3):473-478
In ultrarelativistic heavy-ion collisions at 20 (120) AGeV a copious production of charm (bottom) production sets in which, via correlated semileptonic () decays, gives rise to a dilepton yield at invariant mass 2–3 GeV in excess of the Drell-Yan yield and the thermal dilepton signal from deconfined matter as well. We show that appropriate
single-electron transverse momentum cuts (suitable for ALICE at LHC) cause a threshold like behavior of the dilepton spectra
from heavy-quark meson decays and the Drell-Yan process and can allow to observe a thermal dilepton signal from hot deconfined
matter.
Received: 28 September 1998 / Revised version: 27 November 1998 / Published online: 22 March 1999 相似文献
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The cold component of large transverse momentum dilepton production via semi-coherent two-photon interaction is calculated. The cold contribution is essential to the dilepton spectra in the soft region for different mass bins. The results are compared with the PHENIX experimental data at RHIC, and we find that the modification of semi-coherent two-photon processes is more evident with the rising dilepton mass bins. 相似文献
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Mechanisms of formation for low mass dilepton excess observed in the relativistic heavy ion collisions are considered. The experimental data are reviewed. In addition to discussing the standard mechanisms of dilepton production specific to the collisions of relativistic nuclei (the pion annihilation in the hadron-gas stage and the quark-antiquark annihilation in the quark-gluon phase), the mechanism of dilepton production in the mixed phase of nuclear matter is proposed, and its contribution to the low mass dilepton spectrum is estimated. In addition, the first-order corrections in the strong-interaction coupling constant to the dilepton production in the parton medium and the nonperturbative approaches are considered. 相似文献