王伟 上海交通大学 2015 怀柔 强子物理与核物理前沿研讨会 Production of Heavy Meson Molecules at LHC 王伟 上海交通大学 2015 怀柔 强子物理与核物理前沿研讨会
Content Motivation for Hadron Exotics Heavy Meson Molecule Production at the LHC Summary
Many Excellent Talks in this workshop! 强子是由什么构成？ 经典强子： 介子：夸克和反夸克 重子：三个夸克 超出夸克模型的强子是否存在？ Many Excellent Talks in this workshop!
Zc+= Zc(3900) is Exotic! ZcJ/ψp Zc state contains a cc quark pair _ ZcJ/ψp Zc state contains a cc quark pair charge = ± 1 Zc must contain additional light quarks “minimal” quark configuration : Four-quark states! Zc+=
Zc(3900) is not alone Y(3940) Z(4430) X(3872) Yb(10890) Zc(3900) Zb(10610) Zb(10650) Zc(4020) Y(4260) X(3940) X(4360) Y(4660) Y(4350) Ds(2460) Ds(2137)
What is the nature?
重介子分子态候选者 奇异粒子 组分 X(3872) DD* Xb BB* Zc(3900) Zc(4020) D*D* Zb(10610) Ds(2317) DK JPC 质量(GeV) 1++ 3.87169 ? 1+- 3.8887 4.0239 10.6072 10.6522 0+ 2.3177 PDG:CPC38, 090001 (2014)
How to study exotics? Effective field theory is an approximation to an underlying physical theory. EFT includes the appropriate degrees of freedom to describe physical phenomena occurring at a chosen length scale or energy scale: scale separation
At Low Energy, Quark-hadron duality: QCD degrees of freedom are equivalent to hadron degrees of freedom. Chiral perturbation theory!
ChiPT limited to low energies
mQ →∞时， Q →0 ，重轻夸克之间的自旋相互作用是压低的 轻夸克对于SQ不敏感，不依赖于SQz=1/2或者SQz= –1/2 重夸克对称性 mQ →∞时， Q →0 ，重轻夸克之间的自旋相互作用是压低的 轻夸克对于SQ不敏感，不依赖于SQz=1/2或者SQz= –1/2 轻夸克在与以下四种重夸克态组成的强子中是一样的： b(↑), b(↓); c(↑), c(↓) 如果轻夸克系统的角动量是Jl，与重夸克组成的强子角动量是 J=|Jl±1/2| 构造一个重强子有效理论
Heavy Meson Chiral Perturbation Theory Heavy Meson: DD*, BB* Heavy Meson+a Pseudo-Scalar: DK
Mass pole corresponds to a resonance structure 什么是Hadron Molecule? Summing All order contributions: 1-GV＝0 s=s0 Mass pole corresponds to a resonance structure Hadron Molecule
电子对撞机和强子对撞机 电子对撞机 强子对撞机 背景干净 末态包含很多强子 能量较低(<11GeV) 不能产生大质量粒子 能量高 可以产生较大质量的粒子 产生矢量粒子1— 其它粒子需要从1—衰变末态产生 可以产生任意量子数的粒子
Γ+ ΓGV + ΓGVGV+…. = Γ /(1-GV) Γ is tree-level amplitude. Production at LHC Γ+ ΓGV + ΓGVGV+…. = Γ /(1-GV) Γ is tree-level amplitude. 1-GV＝0
Monte Carlo Event Generators Herwig/Pythia: simulate production rates of constituents, Γ For charmonium/bottomonium-like states, heavy quarks move together, and a third parton is requested. 2->3 process: use Madgraph Use Rivet to analyze hadronic events
F.K. Guo, U.G. Meissner, WW, Z.Yang 1403.4032 X(3872): EFT vs data F.K. Guo, U.G. Meissner, WW, Z.Yang 1403.4032 Histograms: MC event generators Curves: fit according to EFT.
Counterpart of X(3872): JPC=1++; BB* molecule state Xb Counterpart of X(3872): JPC=1++; BB* molecule state Very heavy (11 GeV): difficult to directly produce at electron-positron collider Belle Phys.Rev.Lett.113(2014)142001 CMS made an attempt: Phys.Lett. B727 (2013) 57-76 ATLAS:Phys.Lett.B740(2015)199
Xb decays into Υπ+π- violates isospin tiny BR. F.K. Guo U.G. Meissner WW 1402.6236 Xb decays into Υπ+π- violates isospin tiny BR. One may look at Υγ, Υπ+π-π0,χbπ+π-. Radiative decays width are about 1 keV G.Li WW 1402.6463
Thank you for your attention! Summary Hadron Exotic is a fast-developing branch. EFT can be used to explore hadron molecules. We have studied the production of exotic states at the LHC: a) X-sections; b) decay modes More:Heavy Ion Collision? HZF? CEPC? Thank you for your attention!