https://indico.ihep.ac.cn//event/9242/

Liu Kai presented an interesting paper named as “First Measurement of Form Factors of the Decay of charmed baryon into sigma and electron and anti-neutrino pair”. In the paper they have mentioned that from polrization measured with sigma baryon with the decay of sigma into proton and neutral pion and electron neutrino pair, the g1/f1 to be 1.32+-0.21(0.17)(stat)+-0.05(syst) assuming the SU(3) (flavour) values for g2/f1 and f2/f1. This decay mode is identical to the well measured beta decay, except that the valence d quarks are replaced by s quarks in the initial and final state baryons. In the limit of exact SU(3) (flavor) symmetry the only differences between these processes arise from the different baryon masses and Cabibbo-Kobayashi-Maskawa (CKM) matrix elements. Modifications to the strong interaction dynamics due to the difference between the d and s quark masses can modify the form factors from their SU(3) values.

Questions: Yuhang’s Question:what’s mean about “second class current “ in page one ? Answer: Kai explained an equation for G-Parity conservation in the SM.

Ryuta’s Question: It would be out of this paper but, is there any investitation/report on the stimation of this form factor ratio g1/f1 from the lattice calculation side? (possibly the precision would not be good enough but …) Answer: Kai has presented with different investigation from another paper. The effects of SU(3) symmetry breaking in HSDs were examined from lattice QCD.

Xin’s Question: In Eq.3, it introduced the “fictitious particle Q” , could you explain more? Answer: Kai pointed the reference to be studied for that, but also he mentioned that the transverse momentum of the neutrino is just equal and opposite the transverse momentum of the sigma baryon, we can obtain unambiguous angular variables transverse to the direction of charmed baryon momentum. This could be termed as fictitious particle Q.

Yuzhen’s Question:Could you introduce the details of SU(3)? Answer: Kai showed the picture of Hexagon.

Suyu’s Question: What are upstream and downstream? Answer: the lower part of the detector is called as downstream and the upper part is called as uptream.

My question: Why the SU(3) value has been shifted towards left from central value also the theoretical values? (Fig 3) Answer: The value is fixed at 1.32 and the maximum likelihood well set with theoretical prediction.

Special Topic 62:

Yuhang presented the Special topic “Radiation Damage in Si-Detector”.

There are mainly 2 types of radiation damage in silicon devices.

1. Ionization Damage
2. Displacement Damage (related to not-ionizing energy loss) The most important radiation damage is displacement damage: Defects created in the bulk form energy levels in the band gap: releasing electrons in the conduction band or trapping those from the valence band.Defects-related energy level in the forbidden band increases the generation/recombination rate, thus increasing the leakage current as well. Modification of the effective bulk doping: change depletion voltage and increase leakage current. The microscopic origin of the initial acceptor removal has not been fully understood yet, but experimental observations suggest the creation of acceptors ion complexes that result in the de-activation of doping elements, which are removed from the lattice by interstitials. Reduction of the charge collection efficiency: increase of defects-related trapping centers. Hence the longer the drift time, the higher is the probability that a carrier has to be trapped. In LGAD: This effect of initial acceptor removal not been understood yet. One Possible explanation: In irradiated Silicon with a fluence-dependent concentration that forms with Boron B-I complexes which are electrically inert. These complexes make Boron atoms inactive. To overcome this issue two researches came out: 1.The first one is to reduce the concentration of interstitials available for capturing B atoms by using Carbon-enriched Si wafers where the interstitials get filled with C instead of with B. 2.The second one is to reduce the formation of the acceptor-interstitial complex by replacing Boron with Gallium.

Xin has introduced the next JC100 paper of ATLAS Collaboration “Search for scalar dark energy in tt¯ + EmissT and mono-jet final states with the ATLAS detector”.