Measurement Form Factors Of Proton And Research Of The Cross Section Of E~+e~-→φη On BESⅢ

Particle physics is a branch of physics that studies the elementary particles and the fundamental interactions and transitions between them,it is also the study for material,energy space and time.Quantum electrodynamics(QED)is the theory for describing electromagnetic interaction while quantum chromodynamics(QCD)is the theory of the strong interaction between quarks and gluons.Both of them are the most popular divisions in particle physics.Hadron is the particle which participant the strong interaction,includes baryon,meson and tetxaquark.The research on the form factors of baryon is not only a description for the spatial distributions of electric charge and current in QED theory,but also a test of perturbation and non-perturbation QCD theory.The research on the decay properties of Y(2175)has great significance in studying the nature of Y(2175)resonance.The researches on the the form factors of baryon and the Y(2175)resonance are at the cutting edge of QED and QCD as well as particle physics.The Beijing Electron-Positron Collider(BEPCⅡ)is a double-ring,multi-bunches,high luminosity r-charm factory.The Beijing Spectrometer(BESⅢ)is the unique detector on the BEPCⅡ.Based on 688.5 pb-1 of data collected with the BESⅢ detector,the Born cross sections of e+e-→pp and the effective form factors is studied by energy scan technique for the first time at 22 center-of-mass energy points from 2.00 to 3.08 GeV.Besides,the electromagnetic form factor ratio(|GE|GM|)as well as the absolute value of the electric(|GE|)and magnetic(|GM|)form factors are measured by studying the helicity angle of the proton at 16 center-of-mass energy points.The uncertainties are dominated by systematics and range from 3.0%to 23.5%for the Born cross section of the process e+e-→pp and 3.0%to 23.5%for the effective form factor of proton,respectively.The electromagnetic form factor ratio |GE/GM| is measured with total uncertainties around 10%for scan points ranging from low to intermediate energy.For the first time,the accuracy of the measured form factor ratio in the time-like region is comparable to that of data in the space-like region.The Born cross section is consistent with previous experimental results,|GE/GM| and |GM| are measured with high accuracy,and |GE| is measured for the first time.The precision of our results is unprecedented in the time-like region,providing uncertainties comparable to the space-like region for the first time.The improved results will provide information to understand the proton inner structure and test theoretical models which depend on non-perturbative QCD.Using 2015 R-scan data,647.9 pb-1,collected by BESⅢ detector,we measured Born cross sections of e+e-→φη by energy scan technique for the first time at 19 center-of-mass energy points from 2.00 to 3.08 GeV.The uncertainties are dominated by statistical and range from 5.2%to 20.6%,respectively.The Born cross section is consistent with previous experimental results at most of energy points,and it is the most accurate measurements.That our measurement has been compared with theoretical prediction by NJL model,which rule out this model.From our measurements,the Y(2175)signals is observed around 2.2 GeV,which significance is 5.6a.This is consistent with the expectation of Y(2175)as 23D1 ss quarkonium scenario.The improved results will provide information to study the decay properties and the essence of Y(2175).