令和6年度 茨城大学素粒子論研究室 セミナー案内
セミナー案内
場所は特に記載なければE301を予定 |
※ 現在、予定されているセミナー等
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5/16(金)15:30- |
萩原 薫 氏(KEK) |
セミナー |
タイトル：Discovering the toponium at the LHC
| 概要:
The toponium is the color-singlet bound state of top and anti-top
quarks, just like the bottomonium and charmonium states which
were discovered in the 70's.
The ground state mass is predicted to be about 2 GeV below the ttbar
pair production threshold: m(toponium) \approx 2*mtop -2GeV
Its properties, however, are very different from those of the known
heavy quarkonion, mainly because of its large decay width of 3 GeV,
which is twice the top quark decay width.
Because of the dominant top and anti-top decays, all annihilation
decay branching ratios into $gg$, $\gamma\gamma$, $W^+W^-$, etc
are strongly suppressed.
In addition, the large width covers the whole range of radial
excitations and P-wave states which are predicted to exist within about 1 GeV below the threshold.
Its formation and decay has been studied extensively for the future
$e^+e^-$ colliders, but little has been known for its impacts at
the LHC, except for a rise in the $t\bar{t}$ production cross section
at the threshold, which is less than a percent of the total $t\bar{t}$
events. (arXiv:0804.1014 and 1007.0075)
I would like to explain how I could identify the 3-sigma anomaly in
the di-lepton distributions in the 2019 data as a possible signal
of toponium formation at the LHC.
Refs) B.Fuks et al, [arXiv:2102.11281[hep-ph]] and [arXiv:2411.18962 [hep-ph]]
Basic knowledge to understand physics of toponium may be as follows
1. Angular momentum of two spin 1/2 states in quantum mechanics
2. Bohr level and radius of hydrogen atom
3. Charge conjugation parity of ortho- and para-positronium
4. Shroedinger equation for Hydrogen atom & positronium
5. Shroedinger equation for charmonium and bottomonium
6. Green function of non-relativistic QCD Hamiltonian (Fadin-Khoze, 1987)
7. Lorentz transformation of spin 1/2 particles in the chiral representation
8. Helicity amplitudes and spin polarization density matrix
I will try to explain each item clearly in my blackboard talk.
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6/20(金)16:00- |
神野 隆介 氏(神戸大学) |
セミナー |
タイトル：TBA
| 概要:TBA
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7/11(金)15:30- |
青木 勝輝 氏(京都大学) |
セミナー |
タイトル：TBA
| 概要:TBA
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