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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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纠缠双原子和相干光场作用的光子统计非经典特性 总被引:2,自引:0,他引:2
采用数值计算法研究了纠缠双原子和相干光场相互作用中辐射光场光子数分布的演化特性。结果表明,通过和纠缠双原子的相互作用,使得不具有反聚束效应和光子亚泊松分布的相干光场获得了非经典特性。并且初始双原子间的纠缠强度越大,辐射光场的非经典性质越强,说明可以通过选择初始原子状态制备非经典辐射光场。 相似文献
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本文旨在对近期高能重离子超边缘碰撞中光致产生过程的研究做一个简要综述.相对论性重离子激发的超强电磁场可以被近似认为是一束极高亮度的等效相干光子束流.本文主要讨论两类等效光子参与的高能产生过程:准实光子融合产生轻子对即Breit-Wheeler过程,以及等效光子与原子核内的胶子物质相互作用导致的矢量介子衍射产生过程.这两类过程是研究重离子超边缘碰撞的传统课题,本文主要侧重于讨论碰撞参数依赖效应与末态软光子重求和效应.另一方面,最近一系列研究揭示了相对论重离子所激发的准实光子是高度线性极化的,其极化方向平行于光子横动量方向;并指出可以通过重离子超边缘碰撞中轻子对产生过程的cos 4?方位角不对称来测量光子的线偏振度.这一理论预言随后被SATR合作组的测量所证实.伴随这一新的理论与实验进展,线性极化光子束流同时也给我们提供了一种新颖的实验手段,用来研究量子色动力学唯象学.如线偏振准实光子可导致矢量介子衍射产生过程的各种方位角不对称,通过研究这些方位角不对称可以让我们更深入地理解高能散射过程的双缝干涉效应、库仑-核反应的干涉过程,以及抽取光子维格纳函数等.本文将详述这些效应并讨论未来的理论与实... 相似文献
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SU(2)相干态场与二能级原子的非简并双光子相互作用 总被引:5,自引:0,他引:5
研究了双模SU(2)相干态场与腔中二能级原子的非简并双光子相互作用。用数值计算讨论了SU(2)光场的反关联特性对原子动力学行的影响及场的量子统计性质时间的演化。 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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We study the transverse momentum distribution of vector mesons produced in ultraperipheral relativistic heavy ion collisions (UPCs). In UPCs there is no strong interaction between the nuclei, and the vector mesons are produced in photon-nucleus collisions where the (quasireal) photon is emitted from the other nucleus. Exchanging the role of both ions leads to interference effects. A detailed study of the transverse momentum distribution, which is determined by the transverse momentum of the emitted photon, the production process on the target, and the interference effect, is done. We study the unrestricted cross section and the one with an additional electromagnetic excitation of one or both ions; in the latter case small impact parameters are emphasized. 相似文献
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Rossi P Mirazita M Ronchetti F De Sanctis E Adams G Ambrozewicz P Anciant E Anghinolfi M Asavapibhop B Audit G Avakian H Bagdasaryan H Ball JP Barrow S Battaglieri M Beard K Bektasoglu M Bellis M Benmouna N Berman BL Bertozzi W Bianchi N Biselli AS Boiarinov S Bonner BE Bouchigny S Bradford R Branford D Briscoe WJ Brooks WK Burkert VD Butuceanu C Calarco JR Carman DS Carnahan B Chen S Cole PL Cords D Corvisiero P Crabb D Crannell H Cummings JP De Vita R Degtyarenko PV Denizli H Dennis L 《Physical review letters》2005,94(1):012301
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C. Adloff et al. 《The European Physical Journal C - Particles and Fields》2000,12(4):595-607
Measurements of transverse energy flow are presented for neutral current deep-inelastic scattering events produced in positron-proton
collisions at HERA. The kinematic range covers squared momentum transfers from 3.2 to 2 200 GeV, the Bjorken scaling variable x from to 0.11 and the hadronic mass W from 66 to 233 GeV. The transverse energy flow is measured in the hadronic centre of mass frame and is studied as a function
of , x, W and pseudorapidity. A comparison is made with QCD-based models. The behaviour of the mean transverse energy in the central
pseudorapidity region and an interval corresponding to the photon fragmentation region are analysed as a function of and W.
Received: 15 July 1999 / Published online: 27 January 2000 相似文献
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C. Adloff et al. 《The European Physical Journal C - Particles and Fields》2000,18(2):293-302
The inclusive cross section for the photoproduction of neutral pions has been measured as a function of the transverse momentum,
rapidity, and Feynman x of the mesons at an average photon–proton centre-of-mass energy of 208 GeV and for photon virtualities below GeV. The measurement extends the range covered by previous charged particle measurements at HERA by two units of rapidity in the photon
direction down to a value of in the centre-of-mass frame. The transverse momentum distribution is well described over the whole measured range by a power law ansatz, while an exponential
fit falls below the data at transverse momentum values above 1.5 GeV/c. Good agreement with the predictions of the Monte Carlo
models PYTHIA and PHOJET is found. In the context of the PYTHIA model the data are inconsistent with large intrinsic transverse
momentum values in the photon.
Received: 14 June 2000 / Published online: 27 November 2000 相似文献
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We present a calculation of the generalized parton distributions of the photon when there is nonzero momentum transfer both in the transverse and longitudinal directions. We consider only the contributions when the photon helicity is not flipped and calculate those at leading order in electromagnetic coupling α and zeroth order in the strong coupling αs. We keep the leading logarithmic terms as well as the quark mass terms in the vertex. By taking Fourier transforms of the GPDs with respect to the transverse and longitudinal momentum transfer, we obtain the parton distributions of the photon in position space. 相似文献
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《X射线光谱测定》2005,34(6):477-480
At photon energies below 100 keV, coherent scatter becomes important and because of its sharply forward peaked nature, it is the dominant interaction at small angles. Further, in the momentum transfer region above 0.5 Å?1, free atom form factors are sufficient to describe coherent scattering. The angular distribution of the coherent scattering carries detailed information about the object and can be used as a signature of the tissue type of the object. The aim of this work was to analyze the scattering properties of different human tissues according to histological classifications. The coherent scattering signatures of healthy and neoplastic breast, uterus and kidney tissues were measured using x‐ray synchrotron radiation at the XRD2 beamline at the Brazilian Synchrotron Light Laboratory (LNLS). Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Large transverse momentum dilepton Production in heavy ion collisions with two-photon processes 下载免费PDF全文
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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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