March.20-21, 2014 战略研讨会 1 Z- 工厂物理及高能发展路线图设想 Chao-Hsi Chang ( 张肇西 ) Institute of Theoretical Physics Chinese Academy of Sciences, Beijing (ITP, CAS)

March.20-21, 2014 战略研讨会 2 Outline 引言 1. 高能物理的精确前沿 2. 超级 Z- 工厂及在精确前沿上的地位 超级 Z- 工厂 （标准模型已完备背景下） 1.Z- 玻色子精确性质 & 稀有过程 （超出标准模型线索） 2. 味（重、双重强子，轻子）物理 3.QCD 物理等 超级 Z- 工厂及后续发展路线图 1. 超级 Z- 工厂（大环，双环，高亮度） 2. 后续发展（ Higgs 工厂， ep 对撞， pp 对撞 etc ）

March.20-21, 2014 战略研讨会 3 引言 精确前沿 产额高 亮度高 （和共振效应） 背景 ‘ 干净 ’ 正负电子对撞  - 粲工厂 B- 工厂 Z- 工厂 W- 工厂 ( 广义 ) Higgs- 工厂 ( 广义 ) top- 工厂 ( 广义 ) etc 超级 Z- 工厂 : 我们考虑的 Z- 工厂： Z-boson events 〜 /year beyond ILC. (Giga-Z 〜 10 9 Z/year)

March.20-21, 2014 战略研讨会 4 Introduction The Z-Factories: An e + e - collider running at the Z resonance (properly apply the resonance effect) A factory for all kinds of fermions, except t-quark, in SM owing to the resonance effect! The old ones LEP-I: L 0 = 2.4  cm -2 s -1 Scan 88GeV~94GeV 1.55 ▪ 10 7 hadronic events; 1.7 ▪ 10 6 leptonic events. Detectors: Aleph, Delphi, L3, Opal. SLC: L 0 = 0.6  cm -2 s Z-peak 0.6 ▪ 10 6 events (Especially electron polarization beam: 70%) Detector: SLD

March.20-21, 2014 战略研讨会 5 Introduction The Z-Factories (cont’d): A modern ones: Luminosity: L =10 5 L 0 even higher Events the factory: Z/year ， All kinds of fermions （ except t-quark ） in SM obtained by Z-decay. (To equip well-designed detector(s) accordingly) Note: Considering the requested luminosity and the costs for running, a circle one is better than a linear one. (LC cannot reach to so high luminosity)

March.20-21, 2014 战略研讨会 Precision & rare physics for Z-boson: Exp. measurements ( LEP-I, SLC) vs Theor. prediction (SM) Characteristic Physics (Taken from PDG) SM works well so far, but the pulls are ‘dominant’ by experimental errors. (look for evidences BSM) 6 The effective coupling Z- ff’ (in tree and loops & especially when f, f’ are leptons) constraints for new physics!

March.20-21, 2014 战略研讨会 Precision & rare physics for Z-boson: Exp. measurements ( LEP-I, SLC) vs Theor. prediction (SM) Characteristic Physics 7 (Taken from arXiv: ) SM works well so far, but the pulls are ‘dominant’ by experimental errors. It is very difficult to suppress the expt. errors, but with better designed detectors and much higher statistics of events it is possible to confirm some super Z- factory. Polarization beam is helpful !

March.20-21, 2014 战略研讨会 8 Characteristic Physics arXiv: The precision and rare physics relevant to Z boson directly Z f f ’ = Lepton number violation & FCNC processes; CPV; d f Z etc. Longitudinal component of Z-boson couple to a pair of fermions  m f SM is complete, the theor. uncertainties in SM prediction are suppressed greatly in comparison with those before Higgs was observed 1n 2012 !

March.20-21, 2014 Very good place of τ-lepton physics Z-factory): 战略研讨会 9 Characteristic Physics σ Z- peak ~ 0.5 the highest one (threshold) ~ 2.3 B-factory An important factor is the Lorentz boost effects ! Based on SM: m Z, Sin 2 θ W, α,Γ Z, etc  is the heaviest lepton in SM!  -lepton is special (the heaviest lepton)  3   pairs/year

March.20-21, 2014 战略研讨会 10 Characteristic Physics The most important is the Lorentz boost effects:  -lepton lifetime : τ= ∙ s (comparatively small), cτ ≃ μm Lorentz Z-factory: γ Z-fac = 25.66, cτ γ ≃ μm For comparison: B + -meson: τ= ∙ s cτ ≃ μm B 0 -meson: τ= ∙ s cτ ≃ μm B s -meson: τ= ∙ s cτ ≃ 441 μm D + -meson: τ= ∙ s cτ ≃ μm D 0 -meson: τ= ∙ s cτ ≃ μm D s -meson: τ= 0.500∙ s cτ ≃ μm With vertex detector the momentum-energy of the produced τ-lepton may be well Z-factory, because γ is quite great indeed.

March.20-21, 2014 战略研讨会 11 CPV of V Z ττ : If we define: The limit means: LEP-I example: (weak dipole) Statistics errors quite large, so there are rooms to improve the measurement(s) ! New result: It is greatly helpful that the direction of produced  is measured. Characteristic Physics

March.20-21, 2014 战略研讨会 12 New Physics (hints for BSM): SUSY Models, Multi-Higgs Model, Little Higgs Model, RPV SUSY, Extra Z-boson Model etc It is expeced that Z-factory will offer the most precise constraint on them (especially now SM is ‘complete’). Characteristic Physics The effective couplings When f=f’, the fermion, is b-quark or c-quark or a light quarks R b & R c For leptons: Difficulties are in identifying the flavor ！ Z-boson 的纵分量 源于 Higgs 场！

March.20-21, 2014 战略研讨会 13 Flavor physics & QCD physics etc Z-factory vs super B-factory &  -charm factory c, b-hadron physics (especially open bottom) Characteristic Physics Double heavy hadrons H QQ’ : B c meson, ……, Ξ cc ， Ω cc ， Ξ bc,, Ω bc ， Ξ bb, etc & their excited states (easier to treat bg. ) The events produced in the factory are sufficient for thorough study of the hadrons themselves (mechanism for production and decays etc) and the flavors in hadrons. Roughly theo. estimate Br(Z  H QQ’ +……)  ( more 10 6 samples )

March.20-21, 2014 战略研讨会 14 Flavor physics & QCD physics etc (cont’d) Characteristic Physics D-meson: mixing: Due the Lorentz boost and the lifetime of D meson, at Z-factory the CP violation in the mixing can be observed, whereas it is impossible at B-factory & τ- Charm factory. Fragmentation functions (FFs) and hadronization: Significance: experimentally to use them for flavor tag in hadron collisions etc. ; theoretically to test QCD & models etc. For example: FF of a (heavy) hadron from a quark c or b or a light quark or a gluon etc

March.20-21, 2014 战略研讨会 15 Flavor physics & QCD physics etc (cont’d) Characteristic Physics Spectroscopy for heavy hadrons (especially open bottom) For example: Two body final state! (monoenergy photon)

March.20-21, 2014 战略研讨会 16 Flavor physics & QCD physics etc (cont’d) Characteristic Physics Spectroscopy for heavy hadrons (cont’d)

March.20-21, 2014 战略研讨会 17 Flavor physics & QCD physics etc (cont’d) Characteristic Physics Spectroscopy for heavy hadrons (cont’d)

March.20-21, 2014 战略研讨会 18 Neutrino physics: The invisible width of Z-boson  3 (2.984  0.008) types of light neutrinos. We think that we should estimate the number more carefully and to see how big a room left for the light neutrinos mixing with the sterile one and else. Characteristic Physics  -lepton physics: If Z-bosons/year or higher, then  -lepton pairs (more)/year with quite great Lorentz boost effects may be Super Z-factory. Therefore, the rare decays etc and/or CPV in decay may reach to level (even higher) ! Flavor physics & QCD physics etc (continued)

March.20-21, 2014 战略研讨会 19 Neutrino physics (cont’d) : Characteristic Physics Solid curve is of e-neutrino production; dished curve is of  - or  -neutrino production. Flavor physics & QCD physics etc (cont’d)

March.20-21, 2014 战略研讨会 20 Non-perturbative fragmentation models: LUND, Webber Cluster, Quark Combination (ShangDong) Model. It is the best place to test the models. Characteristic Physics Flavor physics & QCD physics etc (cont’d) Neutrino physics (cont’d) : Q: May be used as a source of monoenergy neutrino ? A: Depends. Yes, if the luminosity of the factory can reach to that of higher than cm -2 s -1. The differential cross-section:

March.20-21, 2014 战略研讨会 21 With modern tech., now a Z-factory may reach to such a luminosity so higher than that of LEP-I & SLC by a magnitude of Quite a lot of observations of the characteristic physics may be carried thus we can expect that some hints beyond SM and/or some fresh phenomena within SM will be explored at the factory and these kinds of discoveries will guide us to develop our knowledge further in a right way. Even if there is some LHC beyond SM, one may still obtain some understanding of it through theoretical loop calculations and the precision observables at Z-factory. We are quite sure that in the long march to explore the world of particle physics, to explore new physics BSM, a Z-factory concerned here would play an irreplaceable role. Summary on the Z-factory

March.20-21, 2014 战略研讨会 22 超级 Z- 工厂及后续发展路线图 1. 超级 Z- 工厂（大环，双环，加速与储存环分离） 大环和双环 （多束团，磁铁 - 真空管道相间，节电） Luminosity: L =10 36 cm -2 s -1 even m Z ！ 亮度超 ILC ，压低统计误差上处于竞争有力地位； 配合精密设计探测器，压低系统误差； 留有极化束的选项； 实现已定物理目标（发现标准模型外物理线索和 标准模型内的全新现象） 充分利用加速得到的电子、正电子束（同步辐射， ep 等固定靶实验等）

March.20-21, 2014 战略研讨会 后续发展（ W 工厂， Higgs 工厂， ep 对撞， pp 对 撞等） 超级 Z- 工厂及后续发展路线图 W 工厂 Higgs 工厂 top- 工厂 ？ 增加功率源，磁铁代替真空管道等 ！ ep 对撞：部分子分布函数, 极化部分子分布函数等 pp 对撞

March.20-21, 2014 战略研讨会 24 Thanks ! Z- 工厂物理及高能发展路线图设想