New light physics beyond the Standard Model

该项目将包括研究超越粒子物理学标准模型的可能的新光粒子的特性，以及它们的天体物理学和宇宙学特征和约束，目的是对高能理论（如弦理论）以及即将到来的实验搜索做出预测。最初的目标将是可靠地计算来自超新星1987a中微子爆发观测的卡鲁扎克莱因引力子的约束，通过考虑等离子体混合效应来纠正先前的计算（这可能会将这些引力子与可见部分物质的耦合常数的最终限制改变几个数量级）。弦理论模型（有争议地）预测，这种粒子是宇宙常数不可避免的结果，加强约束可能会排除这种情况，或者为发现开辟一条道路。等离子体混合效应之前已经考虑过标量（自旋0）和矢量（自旋1），但这将是有史以来第一次计算自旋2的粒子。该方法将涉及使用有限温度场理论的技术来解释对生产速率的介质效应，特别是在先前对低自旋情况的工作基础上建立共振生产的可能性。根据结果，研究这种有限温度效应对Kaluza Klein引力子宇宙学历史的影响也可能是有趣的；由于宇宙在早期非常热，这种效应可能会再次导致与之前的预测相比的巨大变化。这将使我们能够精确地预测暗物质遗迹中这类粒子的丰度（这在以前只是估计的），并可能为实验搜索计划提供预测。随后，范围将扩大，以考虑对其他类型的新粒子的限制，包括轴子，它们的动机特别好，以及可能在暗能量来源中发挥作用的新光标量。同样，在这种情况下，有限的温度和密度效应并没有得到一致的解释。该项目的总体影响将是1。在标准模型和天体粒子物理学之外的物理学研究人员的直接领域。2. 在弦理论现象学领域，（其中的一部分）已经预言了这种新的光粒子的存在。3. 通过提供预测、目标和互补约束，在英国和世界范围内寻找新的光粒子的实验计划。

The project will involve studying the properties of possible new light particles beyond the Standard Model of particle physics and their astrophysical and cosmological signatures and constraints, with the aim to make predictions relevant to high energy theories, such as string theory, as well as upcoming experimental searches. The initial aim will be to reliably calculate the constraints on Kaluza Klein gravitons coming from the observation of a neutrino burst from supernoava 1987a, correcting previous calculations by taking into account plasma mixing effects (which might change the resulting limits on the coupling constants of such gravitons to visible sector matter by orders of magnitude). Such particles have been (controversially) predicted by string theory models as an inevitable consequence of the cosmological constant, and a strengthened constraint could rule out this scenario or open an avenue to a discovery. Plasma mixing effects have previously been considered for scalars (spin 0) and vectors (spin 1) but this would be the first ever computation for a spin 2 particle. The methodology will involve using techniques from finite temperature field theory to account for the in-medium effects on the production rate, and in particular the possibility of resonant production building on the previous work for the lower spin case. Depending on the results, it might also be interesting to investigate the impact of such finite temperature effects on the cosmological history of Kaluza Klein gravitons; since the Universe was extremely hot at early times such effects could again lead to dramatic changes compared to the previous prediction. This will enable a precise prediction of the Dark Matter relic abundance of such particles (which has previously been only estimated) and it might lead to predictions that can be feed into an experimental search programme. Subsequently, the scope will be widened to consider the constraints on other classes of new particles including axions, which are especially well motivated, as well as possible new light scalars that might play a role in sourcing Dark Energy. Again in this case, finite temperature and density effects have not been consistently accounted for. The overall impact of the project will be 1. On the immediate field of researchers in physics beyond the Standard Model and astroparticle physics. 2. On the field of string theory phenomenology, (part of which) has predicted such new light particles exist. 3. The experimental programme searching for new light particles in the UK and world-wide, by providing predictions and targets and complementary constraints.