Energy calibration of tagged photons by the d(γ,π~-pp) reaction

The energy of tagged photons, which were provided from the internal photon tagging system of the Laboratory of Nuclear Science, Tohoku University, has been calibrated using the d(γ,π-pp) reaction. Charged pions and protons in the final state were detected with the Neutral Kaon Spectrometer (NKS2). Photon energies were obtained from the reaction of d(γ,π-pp). The derived photon energy was consistent with the design of the tagger system and the previous measurement using electron-positron pair production. The consistency demonstrates the performance of NKS2 and the capability of the photon energy calibration using d(γ,π-pp).     

Energy calibration of tagged photons by the d(γ,π~-pp) reaction

The energy of tagged photons, which were provided from the internal photon tagging system of the Laboratory of Nuclear Science, Tohoku University, has been calibrated using the d(γ,π-pp) reaction. Charged pions and protons in the final state were detected with the Neutral Kaon Spectrometer (NKS2). Photon energies were obtained from the reaction of d(γ,π-pp). The derived photon energy was consistent with the design of the tagger system and the previous measurement using electron-positron pair production. The...     

Study of Charged Pion Photoproduction on Deuteron with Tagged Photons

The reactions γd→π~- pp and γd→npπ~+π~- have been studied in an energy range from 0.8 to 1.1 GeV at the tagged photon facility of Laboratory of Nuclear Science,T ohoku University.Charged pions and protons in the final state were measured by using the Neutral Kaon Spectrometer (NKS2).The analysis of the γd→π~- pp was mainly used to check the acceptance of the NKS2 and to calibrate the tagged photon energy.The photoproduction of the Δ~(++)Δ~- was identified in the γd→npπ~+π~- reaction.Since the data analyses are still in progress,we issue an interim report and preliminary results.     

Energy diffusion controlled reaction rate in dissipative Hamiltonian systems

In this paper the energy diffusion controlled reaction rate in dissipative Hamiltonian systems is investigated by using the stochastic averaging method for quasi Hamiltonian systems. The boundary value problem of mean first- passage time （MFPT） of averaged system is formulated and the energy diffusion controlled reaction rate is obtained as the inverse of MFPT. The energy diffusion controlled reaction rate in the classical Kramers bistable potential and in a two-dimensional bistable potential with a heat bath are obtained by using the proposed approach respectively. The obtained results are then compared with those from Monte Carlo simulation of original systems and from the classical Kraraers theory. It is shown that the reaction rate obtained by using the proposed approach agrees well with that from Monte Carlo simulation and is more accurate than the classical Kramers rate.     

Measurement of the astrophysical S factor for the low energy ^2H（d,γ）^4He reaction

The γ-rays and protons from an Ed = 20 keV deuteron beam incident on a D-Ti target were measured. A branching ratio of the 2H（d,γ）^4He reaction versus the ^2H（d,p）^3H reaction of Гγ/Гp = （1.061 0.34） x 10.7 has been obtained, and the astrophysical S factor of the ^2H（d,γ）He reaction at the center of mass energy Ecm ≈ 7 keV of （6.0±2.4） ×10^6 keV.b was deduced.     

A new beam asymmetry measurement from pion photoproduction on the neutron using CLAS

We present a preliminary analysis of the photon beam asymmetry observable （Z） from the pho- toproduction reaction channel γn → pπ in the invariant mass range 1.6--2.3 GeV. The measurement was obtained using the near-4π CEBAF Large Acceptance Spectrometer （CLAS） at Jefferson Laboratory, USA, employing a linearly polarised photon beam with an energy range 1.1 2.3 GeV, incident on a liquid deuterium target. The measurement will provide new data to address the poorly established neutron excitation spectrum and will greatly expand the sparse world data-set both in energy and angle.     

Precise measurement of the e^＋e^- →π^＋π^-（γ） cross section with the initial state radiation method at BABAR

We present a precise BABAR measurement on the cross section of the process e^＋e^- →π^＋π^-（γ） from threshold to an energy of 3 GeV with the initial state radiation （ISR） technique, using 232 fb^-1 of data collected with the BABAR detector at e^＋e^- center-of-mass energies near 10.58 GeV. The ISR luminosity is determined from a study of the leptonic process e^＋e^- →μ^＋μ^-γ（γ）. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the ππ cross section measured from threshold to 1.8 GeV is （514.1± 2.2（stat） ± 3.1（syst）） × 10^-10.     

Effective Atomic Numbers for Fe-Mn Alloy Using Transmission Experiment

The effective atomic numbers （Zeff ） and effective electron density （Ne ） for Fe-Mn alloy with different Mn contents are calculated using the mass attenuation coefficients μ/p obtained via XCOM in the photon energy range of i keV-1 GeV. The results are compared with the values measured at the photon energy of 662, 1170 and 1332keV.     

Isomeric ratio of the 181Ta(γ,3n)178m,gTa reaction products at energy Eγmax up to 95 MeV

The photoneutron reaction¹⁸Ta(y,3m)(178m,g)Ta was investigated with the beam from the NSC KIPT electron linear accelerator LUE-40.The measurements were performed using the residual y-activity method.The bremsstrahlung flux-averaged cross sections((E_γmax)>.(r(E_γmax)>m.γmax)g and the isomerie ratio of the re-action products d(E_γmax)were measured.The theoretical values of the averaged cross-sections and isomeric ratio were calculated using the partial cross-sections from the TALYS1.95 code for different level density models LD 1-6..The obtained experimental d(E_γmax)agree with the data in the lterature,but differ from the theoretical values in ab-solute magnitude and the behavior of the energy dependence.A comparison of the determined averaged cross-sec-tions with the calculated cross sections showed the best agreement for the case of the LD 5 model.     

π~0 Photoproduction on Deuteron for Photon Energies from 0.6 to 1.15 GeV

Differential and total cross sections of the γp→π~0 p and the γp→π~0 pn reaction were measured for photon energies between 640 and 1 150 MeV.The data have been compared with SAID and MAID model calculations.π~0 photoproduction on the deuteron shows a strong suppression of the 2nd resonance which is clearly seen in the γp→π~0 p reaction.     

Baryon resonance analysis from SAID

We discuss the analysis of data from πN elastic scattering and single pion photo- and electroproduction. The main focus is a study of low-lying non-strange baryon resonances. Here we concentrate on some difficulties associated with resonance identification, in particular the Roper and higher P11 states.     

Nuclear physics program at MAX-lab

The upgrade of the MAX-lab injector and the construction of MAX Ⅲ, provided the opportunity for upgrading the tagged-photon facility and thus lead to the possibility of more extensive program in nuclear physics research. This upgrade increased the injected electron energy to an eventual maximum of 250 MeV and allows for the extraction of electrons from the MAX Ⅰ ring operated in the stretcher mode. The first stretched beam was delivered in September 2005. The tagged-photon facility was commissioned in parallel with the commissioning of new experimental equipment. The PAC approved experimental program is current in progress, including measurements of pion photoproduction below the △（1232）. The efforts at the tagged photon-facility are pursued within an international collaboration with around fifty members.     

Measurement of R at VEPP-2000

The new e^＋e^- storage ring, VEPP-2000, is being commissioned at Budker Institute of Nuclear Physics, Novosibirsk. Measurement of the total cross section e^＋e^- → hadrons in the whole VEPP-2000 energy range is one of the main goals of the new experiments. We discuss the goals of the measurement and the expected systematic errors.     

πN Elastic Scattering and Resonances in Quark Potential Model

The quark potential model is used to investigate the low-energy elastic scattering of πN system. The model potential consists of the t-channel and s-channel one-gluon exchange potentials and the harmonic oscillator confining potential. By means of the resonating group method, a nonlocal effective potential for the πN system is derived from the interquark potentials and used to calculate the πN elastic scattering phase shifts. By considering the effect of QCD renormalization, the suppression of the spin-orbital coupling and the contribution of the color octet of the clusters （qq） and （qqq）, the numerical results are in fairly good agreement with the experimental data. The same model and method are employed to investigate the possible πN resonances. For this purpose, the resonating group equation is transformed into a standard Schrodinger equation in which the nonlocal effective πN interaction potential is included. Solving the Schrodinger equation by the variational method, we are able to reproduce the masses of some currently concerned πN resonances.     

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.     

Experiment of constraining symmetry energy at supra-saturation density with π^-/π^＋ at HIRFL-CSR

The possibility of the experiment for constraining the symmetry energy Esym（ρ） at supra-densities via π^-/π^＋ probe on the external target experiment of phase I （ ETE（I） ） with part coverage at forward angle at HIRFL-CSR is studied for the first time by using the isospin and momentum dependent hadronic transport model IBUU04. Based on the transport simulation with Au＋Au collisions at 400 MeV/u, it is found that the differential π^-/π^＋ ratios are more sensitive to Esym（ρ） at forward angles in laboratory reference, compared with the total yield ratio widely proposed. The insufficient coverage at lower transverse momentum maintains the sensitivity of the dependence of π^-/π^＋ ratio on the Esym（ρ） at high density, indicating that the ETF （I） under construction in Lanzhou provides the possibility of performing the experiment for probing the asymmetric nuclear equation of state.     

Baryon resonance analysis from MAID

The unitary isobar model MAID2007 has been used to analyze the recent data of pion electroproduction. The model contains all four-star resonances in the region below W = 2 GeV and both single-Q2 and Q2 dependent transition form factors could be obtained for the Delta, Roper, D13（1520）, S11 （1535）, S31 （1620）, $11（1650）, D15（1675）, F15（1680） and P13（1720）. From the complete world data base, including also π data on the neutron, also Q2 dependent neutron form factors are obtained. For all transition form factors we also give convenient numerical parameterizations that can be used in other reactions. Furthermore, we show how the transition form factors can be used to obtain empirical transverse charge densities and our first results are given for the Roper, the S11 and D13 resonances.     

Photoproduction of positive pions from hydrogen with PHOENICS at ELSA

The differential cross section of the reaction γp→π⁺n has been measured with the PHOENICS detector at ELSA in Bonn. For the first time this cross section has been determined simultaneously over a large range of photon energies (E_γ = 220−900 MeV) and pion angles (Θ^c.m._pi = 35°−135°) with a tagged photon facility. The experimental set-up allowed a considerable kinematic overdetermination of the investigated reaction. Accordingly, the background contributions have been suppressed to below 1%. The measured differential cross section is in good agreement with existing data. The comparison with different model calculations is presented.