The impact of beamstrahlung on precision measurements at CLIC
The impact of beamstrahlung on precision measurements at CLIC
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束致辐射对 CLIC 精密测量的影响
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
K. Matchev
中科院分区：
文献类型：
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作者：
Asesh K. Datta;K. Kong;K. Matchev
我们回顾了轻子对撞机上束致辐射的两种常用近似处理方法。我们讨论了这些近似的适用性，并表明它们在超高能e+e−对撞机(如CLIC)上必然失效。我们用束致辐射演化方程的精确数值解来模拟CLIC的束致致辐射效应，并与两种近似进行了比较。我们还讨论了束致辐射对新物理参数精确测量的影响。作为一个例子，我们考虑了宇宙额外维度中的Kaluza-Klein轻子产生，并研究了束致辐射引起的终点轻子能谱的退化。固定的质心能量ECM是轻子对撞机的一个著名优点。与强子对撞机不同的是，强子对撞机的部分子水平ECM随着事件的不同而不同，额外的运动学约束允许许多新的测量。一些著名的例子是：在各种运动学可观测到的分布中存在尖锐的端点，阈值扫描的可能性，丢失质量的测量，在生产中的角分布等。所有这些新的实验工具的可用使得能够精确地确定新的物理参数，并且是追求建造下一代轻子对撞机的主要动机。然而，人们应该记住，实际上，由于束致辐射和韧致辐射的影响，束流能量的一小部分总是会损失，因此事件中真正的质心能量经常偏离其标称值。本说明的目的是调查这些效应在多大程度上会成为在超高能e+e−对撞机上精确测量新物理参数的问题。为此，以秒为单位。2.我们首先回顾了束致辐射的两种常用的参数化方法。然后是SEC。3我们讨论了这些近似对于具有亚TeV ECM的轻子对撞机(如ILC)以及多TeV ECM(如CLIC)的适用性。我们发现，后一种情况超出了两种近似的有效范围，需要对束致辐射效应进行精确的处理。我们使用Sokolov-Ternov跃迁几率的精确表达式来数值求解束致辐射的演化方程(见SEC。2)。在证券交易委员会。4我们考虑了通用额外维度(UED)中Kaluza-Klein Muon产生的例子，并使用了SEC的数值结果。3研究束致辐射对终点轻子能谱的影响。同样的分析也可以很容易地应用于超对称性中的smuon产生。
We review two commonly used approximate treatments of beamstrahlung at lepton colliders. We discuss the applicability of those approximations and show that they are bound to fail at very high energy e + e − colliders such as CLIC. We model the beamstrahlung effects at CLIC by an exact numerical solution to the evolution equation for beamstrahlung and compare to the two approximations. We also discuss the impact of beamstrahlung on precision measurements of new physics parameters. As an illustration we consider Kaluza-Klein lepton production in Universal Extra Dimensions and study the deterioration of the endpoint lepton energy spectrum caused by beamstrahlung. The fixed center of mass energy ECM is a celebrated virtue of lepton colliders. In contrast to hadron colliders, where the parton-level ECM varies from event to event, the additional kinematic constraint allows for a number of new measurements. Some well-known examples are: the presence of sharp endpoints in the distributions of various kinematic observables, the possibility of threshold scans, measurements of the missing mass, the angular distributions at production, etc. The availability of all these new experimental tools allows for precise determination of new physics parameters and is the primary motivation for pursuing the construction of a next generation lepton collider. One should keep in mind, however, that in reality a fraction of the beam energy is always lost due to the effects of beamstrahlung and bremsstrahlung, so that the true center of mass energy in the event is often displaced from its nominal value. The purpose of the present note is to investigate to what extent these effects can represent a problem for precision measurements of new physics parameters at very high energy e + e − colliders such as CLIC. To this end, in Sec. 2 we first review the two commonly used parametrizations of beamstrahlung. Then in Sec. 3 we discuss the applicability of those approximations for lepton colliders with sub-TeV ECM (such as ILC) as well as ECM in the multi-TeV range (such as CLIC). We find that the latter case falls outside the range of validity of the two approximations, and an exact treatment of beamstrahlung effects is required. We solve numerically the evolution equation for beamstrahlung using the exact expression for the Sokolov-Ternov transition probability (see Sec. 2). In Sec. 4 we consider the example of Kaluza-Klein muon production in Universal Extra Dimensions (UED) and use our numerical results from Sec. 3 to investigate the deterioration of the endpoint lepton energy spectrum caused by beamstrahlung. The same analysis can be readily applied to smuon production in supersymmetry as well.