Recent content by zhangyang

http://www.sciencedirect.com/science/article/pii/S0146641011001086 3.2. Expansion over multipole amplitudes Thank you!

When CLAS of Jlab describe the result of the process ep→epπ,the use the terminal "transverse amplitude" Ml±(W,Q2), El±(W,Q2),and "scalar(longitudinal) amplitudes"Sl±(W,Q2),they correspond to photons of the magnetic, electric, and Coulombic type.Are they observables? The index of...

Sorry ,there is some error in my operation,I want to delate one of them.

Pi-N scattering is useful for research on neucleon resonance.But pi meson is not stable,how could it be controlled to collide with a neucleon? While,virtual photon is also used to excite neucleon,it is internal line particle,which is determined by a reaction,so how hard could it be controlled...

From Luri's book,I find the content I want. This paper is also useful： http://arxiv.org/find/all/1/all:+AND+spin+AND+higher+AND+of+AND+quantization+AND+the+AND+to+AND+approach+AND+Projection+operator/0/1/0/all/0/1

If I want to calculate a decay of excited nucleons,sometimes I must treat the spin 3/2 field operator. If I use CG coefficient method, for example http://arxiv.org/abs/hep-ph/0210164 (page 3,the third equation) But it is a result,not the starting.The thought looks like a synthesis between...

From particle data group,(http://pdg.lbl.gov/2014/listings/contents_listings.html) I can see the decay branching ratios of N(1875),but the total width is not found.The "Breit Wigner width " are very different.So my question is ,How do they get the branching ratio without a certain total width?

In this process: N*→N+photon If we want to calculate the amplitude with the following interaction Lagrangian: (http://arxiv.org/abs/nucl-th/0205052) If we use functional method,the field operator is not polynomial,how to use "center formula"to bring functional derivative in? Or we must...

Ｉ Want to analyze the decay from a excited nucleon to a nucleon and an Omega meson.I have seen a propagator which descripes a process : a→b+c (Eur. Phys. J. A16, 537–547 (2003), Covariant tensor formalism for partial-wave analyses ofψdecay to mesons ,B.S. Zou and...

In the reaction :e,p→e,p,η; (p,η)is called a "baryon resonance",a state of which is "S11(1535)". (http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.86.1702) In Particle Data Group,there is an excited nucleon N(1535).Are they the same? But how could a (p,η)resonce be called excited...

For example, a decay J/psi →p, anti-p,gamma; An article analyze the invariant mass of p bar p as a whole, "Observation of a Near-Threshold Enhancement in thepp¯Mass Spectrum from RadiativeJ/ψ→γpp¯Decays"(http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.91.022001), but they treat the...

Thank you. Maybe I haven't considered some aspects,but if it is a two-body-product decay ,in the parent rest frame,the electrons must be back to back,and have same momentum,so how could it generate a spectrum? The inner product would be a constant,right?

Is there some contradiction in application of Feynman rule on the two-body-product decay?Because the probability amplitude is a function on momentum,if the momentum is discrete,or even unique,what is the meaning of it? Or,QFT is only about elementary particle,whose decay are all...

What can we learn from Invariant Mass Spectrum?How to measure it?So,how to read it? Mass measurement is converted into energy measurement,but how could we make the quantity change continuously in order to form the horizontal axis? How to divide different particles to measure them...

I agree.The reason is the conservation of momentum and the relation between momentum and energy which make the two-body-product decay's energy spectrum discrete. And the gamma decay is always after α or β decay,which make a nucleus excited.So gamma decay is very particular.