Charged Pion Form Factor Determination in the Range of Q2 = 0.6 ～ 1.6 (GeV/c)2

Using the most recent differential cross section data for ep quasi-elastic scattering, the charged pion formation and its form factor Fπ is calculated in the energy range of 2.4 ～ 4 GeV at Q2 = 0.6 ～ 1.6 (GeV/c)2. The functional dependence of the charged pion form factor to the separated cross section σL is investigated and compared to the previously determined result.     

In-medium pion dispersion relation and medium correction of Nπ■Δ near the threshold energy of pion production

Transport models cannot simultaneously explain very recent data on pion multiplicities and pion charged ratios from central collision of Sn+Sn at 0.27 A GeV.This stimulates further investigations on the pion dispersion relation,in-medium Nπ→Δ cross sections,and Δ→Nπ decay widths near the threshold energy or at subthreshold energy of pion production in isospin asymmetric nuclear matter.In this study,the pion dispersion relation,in-medium Nπ→Δ cross section,and Δ→Nπ decay width near the threshold energy are investigated in isospin asymmetric nuclear matter by using the one-boson-exchange model.With the consideration of the energy conservation effect,the in-medium Nπ→Δ cross sections are enhanced at s1/2 <1.11 GeV in a nuclear medium.The prediction of pion multiplicity and π-/π+ ratios near the threshold energy could be modified if this effect is considered in transport model simulations.     

K^＋ Scattering with the Nuclear Pion from Chiral Effective Lagrangian

The K^ scattering cross section with the in-medium virtual pion is evaluated in the lowest-order chiral perturbation theory with the density-dependent pion decay constant and mass.The contribution of nuclear pions to the total K^ -nucleus cross section is found to be about 5% and 12% when the excess pion numbers per nucleon nπ=0.057 and 0.13 are used.The inclusion of the off-mass-shell behavior of the K^ π amplitude produced a significant improvement in the K^ -nucleus cross section.     

High Energy Proton-Proton Elastic Scattering in the Pomeron Exchange Model

We study high energy proton-proton elastic scattering in the framework of Pomeron exchange model. The cross section of the process are calculated without any free parameters. Our finding is that Pomeron exchange theory gives perfect fits to total cross section at the energy of√s higher than 10 GeV and to differential cross section at the momentum transfer [t] less than 1.5 GeV2. For total cross section at lower energy √s ＜ 10 GeV and differential cross section at larger momentum transfer region of |t| ＞ 1.5 GeV2, the Pomeron exchange theory needs to be improved.     

Measurement of the pion form factor for M_(ππ)～2 between 0.1 and 0.85 GeV~2 with the KLOE detector

The KLOE experiment at the φ-factory DAΦNE has measured the pion form factor in the range between 0.1M_(ππ)～2 0.85 GeV2 using events taken at s～(1/2)=1 GeV with a photon emitted at large polar angles in the initial state.This measurement extends the M_(ππ)～2 region covered by KLOE ISR measurements of the pion form factor down to the two pion production threshold.The value obtained in this measurement of the dipion contribution to the muon anomalous magnetic moment of aμππ =(478.5±2.0stat±4.8syst±2.9theo)·10-10 further confirms the discrepancy between the Standard Model evaluation for aμ and the experimental value measured by the(g-2) collaboration at BNL.     

Vector meson J/ψ, Ф electro-production in QCD

We study the vector meson electro-production off the proton in a QCD inspired model. A calculation of the differential cross section is performed for the J/ψ, Ф meson off the proton. The theoretical results are consistent with the experimental data, and remind us to consider the contribution from the tensor glueball and Odderon to the differential cross section. Since gluons interact among themselves via self-interaction, the gluons can form a glueball with quantum numbers I^G, J^PC = 0^＋, 2^＋＋ with a decay width Гt = 100 MeV and mass of mG = 2.23 GeV. The three gluons can form a three gluon color bound state with charge conjugation quantum number C = -1. This study is quite important to verify the validity of QCD and to search for new particles （tensor glueball and Odderon） as well as quest for new physics.     

Vector meson J/ψ,φ electro-production in QCD

We study the vector meson electro-production off the proton in a QCD inspired model.A calculation of the differential cross section is performed for the J/ψ,φ meson off the proton.The theoretical results are consistent with the experimental data,and remind us to consider the contribution from the tensor glueball and Odderon to the differential cross section.Since gluons interact among themselves via self-interaction,the gluons can form a glueball with quantum numbers IG,JPC =0+,2++,with a decay width Γt =100 MeV and mass of mG = 2.23 GeV.The three gluons can form a three gluon color bound state with charge conjugation quantum number C =-1.This study is quite important to verify the validity of QCD and to search for new particles(tensor glueball and Odderon) as well as quest for new physics.     

Measurement of the pion form factor for Mππ^2 between 0.1 and 0.85 GeV2 with the KLOE detector

The KLOE experiment at the φ-factory DAФPNE has measured the pion form factor in the range between 0.1 〈 Mππ^2 〈 0.85 GeV^2 using events taken at √s = 1 GeV with a photon emitted at large polar angles in the initial state. This measurement extends the Mππ^2 region covered by KLOE ISR measurements of the pion form factor down to the two pion production threshold. The value obtained in this measurement of the dipion contribution to the muon anomalous magnetic moment of △αμ^ππ= （478.5±2-0stat±4.8syst±2.9theo）·10^-10 further confirms the discrepancy between the Standard Model evaluation for αμ and the experimental value measured by the （g-2） collaboration at BNL.     

An exclusive event generator for e＋e- scan experiments

An exclusive event generator is designed for e＋e- scan experiments, including initial state radiation effects up to the second order correction. The generator is coded within the framework of BesEvtGen. There are seventy hadronic decay modes available, with effective center-of-mass energy coverage from the two pion mass threshold up to about 6 GeV. The accuracy achieved for the initial state radiation correction reaches the level achieved by the KKMC generator. The uncertainty associated with the calculation of the correction factor to the initial state radiation is dominated by the measurements of the energy-dependent Born cross section.     

Probing the TC2 model via Production of Top Quark Pairs at Tevatron and LHC

The topcolour-assisted technicolour （TC2） model is an interesting dynamical theory among the various new physics models. We cMculate the total tt cross section and the relative correction of the TC2 model to the cross section at Tevatron Run Ⅱ and LHC. At the Tevatron Run Ⅱ, the cross section predicted by the standard model （SM） is consistent with the experimental data, and in most parameter spaces of the TC2 model, the relative correction of the TC2 model to the cross section is too small to be detectable. We find that the tt cross section is more sensitive to the parameters of the TC2 model at the LHC and the relative correction of the TC2 model to the cross section is over 10% in general. Such a value of the relative correction should be large enough to be detectable at the LHC. Therefore, it is promising to find the clue of the TC2 model via the tt production at the LHC.     

Determination of the pion charge form factor at Q2=1.60 and 2.45 (GeV/c)2

The 1H(e,e'pi+)n cross section was measured at four-momentum transfers of Q2=1.60 and 2.45 GeV2 at an invariant mass of the photon nucleon system of W=2.22 GeV. The charged pion form factor (F(pi)) was extracted from the data by comparing the separated longitudinal pion electroproduction cross section to a Regge model prediction in which F(pi) is a free parameter. The results indicate that the pion form factor deviates from the charge-radius constrained monopole form at these values of Q2 by one sigma, but is still far from its perturbative quantum chromodynamics prediction.     

The weak electroproduction of Σ in electron–proton scattering

We obtain differential cross sections for the reaction e⁻+p→Σ⁰+ν_e, for incident electron energies from 0.5 GeV to 6.0 GeV. This calculation is phenomenologically based and makes use of SU(3) and SU(2) relations. We obtain contributions of the individual form factors to the differential cross section and show that the vector current form factor dominates in the region of observability. We also obtain reaction rates for a standard set of conditions. Finally we compare this case with that for Λ production and discuss what might be learned from this reaction concerning the structure of the weak, strangeness changing, hadronic current.     

The Signatures of the Neutral Top-Pion at the NLC and the Tevatron in Topcolor-Assisted MWTC Model

The neutral top-pion π_t⁰ can couple to the gluons and the photons through the top quark triangle-loop. we calculate the corrections of the neutral top-pion π_t⁰ to the tt production cross section in topcolor-assisted multiscale walking technicolor model. We find that, for a heavy neutral top-pion, the corrections are quite significant. For m_t = 175 GeV, 5 GeV ≤ m_t¹ ≤ 20 GeV and M_πt = 350 GeV, the relative correction Δσ/σ₀ is larger than 10% which might be observed at a high-luminosity Tevatron. We further estimate the production cross section of π_t⁰ at the NLC experiment. We find that the production rate is significantly large. The neutral top-pion π_t⁰ may be detected in future e⁺e^- linear collider experiments.     

The Rare DecayK+ →π+vv and Effects of Charged Technipions

In this paper we calculate the contributions to the FCNC rare decay from the charged technipion P^± and P₈^± in the frarnervork of technicolor theory. We find that: (a) P^± can provide a positive but relatively small contribution to the process; (b) the contribution is large and positive for relatively light P₈^± and becomes negative for m_p8 ≥ 531 GeV; (c) the enhancement to the ratio BR() can be as large as a factor of 30 for m_p1 = 50 GeV and m_p8 = 100 GeV; (d) the lower mass bound on m_p8 is m_p8 > 220,190 GeV for m_p1 = 50,200 GeV, respectively     

Measurement of the charged pion electromagnetic form factor

Separated longitudinal and transverse structure functions for the reaction 1H(e,e(')pi(+))n were measured in the momentum transfer region Q2 = 0.6--1.6 (GeV/c)(2) at a value of the invariant mass W = 1.95 GeV. New values for the pion charge form factor were extracted from the longitudinal cross section by using a recently developed Regge model. The results indicate that the pion form factor in this region is larger than previously assumed and is consistent with a monopole parametrization fitted to very low Q2 elastic data.     

Supersymmetry for Fermion Masses

It is proposed that supersymmetry （SUSY） may be used to understand fermion mass hierarchies. A family symmetry ZSL is introduced, which is the cyclic symmetry among the three generation SU（2） doublets. SUSY breaks at a high energy scale - 10^11 GeV. The electroweak energy scale- 100 GeV is unnaturally small No additional global symmetry, like the R-parlty, is imposed. The Yukawa couplings and R-parity violating couplings all take their natural values, which are О（10^0 -10^-2）. Under the family symmetry, only the third generation charged ferrnions get their masses. This family symmetry is broken in the soft SUSY breaking terms, which result in a hierarchical pattern of the fermion masses. It turns out that for the charged leptons, the r mass is from the Higgs vacuum expectation value （VEV） and the sneutrino VEVs, the muon mass is due to the sneutrino VEVs, and the electron gains its mass due to both ZZL and SUSY hreaking. The large neutrino mixing are produced with neutralinos playing the partial role of right-handed neutrinos. │Ve3│, which is for Ve-Vr mixing, is expected to be about 0.1. For the quarks, the third generation masses are from the Higgs VEVs, the second generation masses are from quantum corrections, and the down quark mass due to the sneutrino VEVs. It explains me/ms, ms/me, md 〉 mu and so on. Other aspects of the model are discussed.     

Cross section of the charged current reaction C(ve, e)Ng.s.

The charged current nuclear transition ¹²C(v_e, e⁻)¹²N_g.s. has been observed in the KARMEN experiment. The flux average cross section for v_e from μ⁺ decay at rest is determined to be σ = [8.1±0.9(stat.)±0.75 (syst.)]×10⁻⁴²cm². For the first time also the energy dependence of the cross section has been measured for neutrino energies up to 50 MeV.     

HOW TO DETERMINE THE NUCLEAR MATRIX ELEMENT IN 2β-Decay?-A DISCUSSION OF PCAC, 2β-DECAY AND DOUBLE-CHARGE EXCHANGE REACTION OF PIONS ON NUCLEI

It is shown that by applying PCAC, the 2β-decay process can be directly related to double-charge-exchange reaction. Therefore, by studying double-charge-exchange reactions one is able to determine the nuclear matrix element of the relevant 2β-decay experimentally. A preliminary analysis has indicated that if the experimental data of forward-angle cross section on Ca⁴⁰ with pion beam at 164 Mev^[9] are used and extrapolated to Ca⁴⁸, then the squared nuclear matrix element thus determined is smaller than that calculated for Ca⁴⁰→Ti⁴⁸+2e^-+2v^[11] by 10⁵～10⁶.     

Mixing of Pseudo-Goldstone Bosons and Effects on HERA High-Q2 Events

We study the mixing of pseudo-Goldstone bosons predicted by technicolor theory and the effects on HERA high-Q² events. We find that: (a) there eyist two F = 0 scalar leptoquarks P₃′ with m(P₃′) = 200 GeV and P₃⁰ with m(₃⁰) =225 GeV for β₁ = β₂ = 0.4; (b) the P₃′ and P₃⁰ can contribute the required cross section to account for the excesses of NC and CC high-Q² events; (c) the coexistence of P₃′ and P₃⁰ may be responsible for the splitting of averaged mass of the H1 and ZEUS high-Q² neutral current events.     

Search for coherent charged pion production in neutrino-carbon interactions

We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed, and an upper limit of is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV.