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A large-acceptance multiparticle spectrometer SAMURAI has been constructed at the RIKEN RI Beam Factory (RIBF) for RI beam experiments. It was designed primarily for kinematically complete experiments such as the invariant-mass spectroscopy of particle-unbound states in exotic nuclei, by detecting heavy fragments and projectile-rapidity nucleons in coincidence. The system consists of a superconducting dipole magnet, beam line detectors, heavy fragment detectors, neutron detectors, and proton detectors. The SAMURAI spectrometer was commissioned in March 2012, and a rigidity resolution of about 1/1500 was obtained for RI beams up to 2.4 GeV/c.

In order to study the S11(1535) resonance in the nuclear medium, total cross sections of the (γ, η) reactions on C, Al and Cu have been measured for photon energies between 680 and 1000 MeV. A broad resonance due to the excitation and decay of the S11 resonance in the nucleus has been clearly observed for the first time. The apparent energy and width of the resonance are 900 and 300 MeV, respectively. Model calculations based on the quantum molecular dynamics have been performed. A comparison of the calculations with the data indicates that the S11 resonance in nuclei should have a larger width; the width of about 250 MeV is required while the elementary one is about 150 MeV.

The experimental study of the reaction 3He(γ, pp)n is being carried out in the photon energy range Eγ = 200–500 MeV at the Tokyo 1.3 GeV electron synchrotron. By use of the tagged and linearly polarized photon beam, and the π-sr magnetic spectrometer TAGX, a kinematically complete measurement of the reaction 3He(γ, pp)n will be made. The high statistics measurements of dσdΩ and Σ of the reaction 3He(γ, pp)n will clarify the photon absorption mechanism.

The response of a scintillation detector array consisting of 7 pure CsI crystals with a thickness of 13.5 radiation lenghths has been measured to electrons, positrons and charged pions with momenta ranging from 250 to 1000 MeV/ c . For electrons and positrons the detector provides a very linear response to the incident energy. High energy charged pions make a peak at around 150 MeV corresponding to the ionization energy loss. In addition to the peak, comparable yields which are caused by nuclear reactions are distributed up to the maximum available enegy and form a broad bump. The shape of the broad bump for positive pions is different from that for negative pions with the same momentum. A simulation with a GEANT program cannot reproduce the shape of the broad bump.

The experimental study of nuclear moments of several neutron-rich nuclei, using the phenomenon of ejectile spin polarization in the projectile fragmentation reaction, is reported. The spin-polarized fragments14B and15B were produced in the fragmentation of18O projectiles on a Nb target at 64.7 MeV/u. They were implanted into a Mg single crystal, and the quadrupole momentsQ were determined by theβ-NMR method. The results, ¦Q(14B)¦ =29.84 ±0.75 mb and ¦Q(15B)¦=38.01 ±1.08 mb, are compared with theoretical models. Shell model calculations in a 0ħω model space, using effective charges commonly accepted in this mass region, predict values about 40% larger than the experimentalQ(15B). Agreement is obtained when a much smaller effective charge for neutrons is employed. The method was also applied to the measurement of the magnetic moments of17N and17B. The result reveals an important contribution of configurations with excess neutrons coupled to formJ π=2+.

A set of CsI(pure) crystals have been tested for use as an electromagnetic calorimeter for π0 detection in photonuclear reactions at photon energies below 1.2 GeV. Performances of the calorimeter including energy and position resolution are studied by using the electron and tagged-photon beams at the INS-Tokyo electron synchrotron. In the first experiment for the nuclear coherent π0 photoproduction carried out at INS, a π0 mass resolution of 7 MeV (rms) has been obtained in the π0 energy region between 0.5 and 1.0 GeV.

Phenomenon of ejectile spin polarization in the projectile fragmentation reaction was exploited as a tool to produce polarized radioactive nuclei. The polarized unstable nuclei were subjected to the β-detected NMR meaurements, and the magnetic moments and electric quadrupole moments were determined for several neutron-rich light nuclei. The comparison of the experimental results with theoretical predictions shows that the nuclear moments provide useful test of models for nuclear structure and interaction in the region of light-mass unstable nuclei.

We have made a kinematically complete measurement of the Coulomb dissociation of 11Be on Pb target at 72A MeV. The low-lying dipole strength distribution indicated the importance of the direct breakup mechanism, which was also supported by the observed effect of the Coulomb post acceleration. The E1 dominance of the reaction was confirmed by the angular distribution of 10Be in the rest frame of 11Be.

The Coulomb excitation of a very neutron-rich nucleus 32Mg to its 2+ state was studied using an unstable nuclear beam of 32Mg at 49.2 MeV/u with a 208Pb target. The B(E2) value of 454±78 e2fm4 was extracted by a coupled channel analysis. The value is in good agreement with recent predictions. It confirms a large deformation for 32Mg suggested by the low excitation energy of the 2+ state, and points to the vanishing of the N = 20 shell gap.

We have measured the excitation energy spectrum of the 10 Be+n system in the Coulomb dissociation of the one-neutron-halo nucleus 11Be on a Pb target at 72A MeV. We have determined the dipole strength distribution dB (E1) /dEx which shows a strong peak at about 800 keV excitation energy. The spectral shape is consistent with a direct breakup model. The Coulomb post accelaration effect has been observed also to support the direct breakup mechanism. The E1 dominance of the Coulomb dissociation is confirmed by observed angular distributions of 10Be in the 11Be rest frame.

SAMURAI project aims to open a new research field in nuclear physics by the use of a large acceptance spectrometer for kinematically complete measurements of multiple particles emitted in RI-beam induced reactions. The SAMURAI spectrometer consists of a large gap superconducting dipole magnet, heavy ion detectors, neutron detectors, and proton detectors. What is special about the SAMURAI system is that projectile-rapidity protons or neutrons are detected with large angular and momentum acceptance in coincidence with heavy projectile fragments. With an effective combination of these equipments, the SAMURAI system allows us to perform various experiments: electromagnetic dissociation, various direct reactions, polarized deuteron induced reactions, and EOS studies. SAMURAI project is currently underway at RIBF. The construction of the superconducting dipole magnet will start in autumn 2010 and finish in spring 2011. The detectors are also being constructed in parallel. The first commissioning run will be performed in early 2012.

Differential cross sections and vector and tensor analyzing powers for the 11 B(d, 2 He) 11 Be reaction at 70 MeV have been measured and Gamow-Teller and spinflip dipole transitions are identified. Observed mean excitation energy and strength for the spinflip dipole transition in which possible neutron halo effect manifests itself are consistent with the shell model prediction which takes the neutron halo into account.

The total photoproduction cross section is determined from a measurement of electroproduction with the ZEUS detector at HERA. The Q2 values of the virtual photons are in the range 10−7

Since the discovery of a neutron halo[1] in large neutron-excess nuclei, 11Li, 11Be and 14Be, a lot of interest has been placed on the nuclear structure of these nuclei. However such a study is hampered by experimental difficulties to excite those nuclei. Although the 11Be nucleus is the easiest to access among them, the spin and parity (Jπ) is assigned for only few states[2]. The ground state is known to have an anomalous Jπ of \({\frac{1}{2}^ + }\) which is very unexpected by the naive shell model predictions. The Jπ of the first excited state at E x =0.32 MeV is also known to be \({\frac{1}{2}^ - }\).

The reaction mechanism of projectile fragmentation at intermediate energies has been investigated observing the target dependence of the production cross sections of very neutron-rich nuclei. Measurement of longitudinal momentum distributions of projectile-like fragments within a wide range of fragment mass and its charge was performed using a hundred-MeV/n $^{40}$Ar beam incident on Be and Ta targets. By measurement of fragment momentum distribution, a parabolic mass dependence of momentum peak shift was observed in the results of both targets, and a phenomenon of light-fragment acceleration was found only in the Be-target data. The analysis of production cross sections revealed an obvious enhancement of the target dependence except target size effect when the neutron excess is increased. This result implies the breakdown of factorization (BOF) of production cross sections for very neutron-rich nuclei near the drip line., Comment: 16 pages, 18 figures, submitted to Phys. Rev. C

The momentum spectrum of the recoil protons in the reaction γ + p → p + anything is measured in the incident energy range from 710 MeV to 950 MeV. A tagged photon beam is used as an incident photon. From this measurement the cross sections of the reactions, γ + p → p + π+ + π− and γ + p → p + π0 + π0, are obtained as functions of the energy of the incident photon. The observed ratio of these two reactions ( p + π 0 + π 0 ) ( p + π + + π − ) is about 0.2 in the incident energy region investigated, and is consistent with the excitation of the isospin - 1 2 intermediate state in the s-channel. No serious deviations from the phase space are observed in the missing-mass spectrum of protons.

The polarized target asymmetry T(theta) for the reaction ..gamma..d..-->..pn has been measured at proton c.m. angles of 70/sup 0/, 100/sup 0/, and 130/sup 0/ in the photon energy region between 300 and 700 MeV. The observed asymmetry shows relatively small values. A phenomenological partial wave analysis is carried out by using the present T(theta) data together with recent results on the differential cross section dsigma/d..cap omega.., the recoil proton polarization P(theta), and the polarized beam asymmetry ..sigma..(theta). The gross features of dsigma/d..cap omega.., T(theta), and ..sigma..(theta) are reproduced reasonably well without dibaryon resonances, but those of P(theta) are not, even with arbitrary smooth backgrounds in the present scheme of analysis. Possible contributions of dibaryon resonances are studied.

Momentum spectra of protons from the ($\ensuremath{\gamma}$, $p$) reaction have been measured at ${\ensuremath{\theta}}_{p}=30\ifmmode^\circ\else\textdegree\fi{}$ for $^{1}\mathrm{H}$, $^{2}\mathrm{H}$, $^{4}\mathrm{He}$, $^{9}\mathrm{Be}$, $^{12}\mathrm{C}$, and $^{16}\mathrm{O}$ with a tagged photon beam with energies from 187 to 427 MeV. By analysis of these inclusive proton spectra, cross sections for the pion photoproduction from the quasifree nucleon in the target nucleus and those for the photodisintegration of the quasifree two-nucleon system have been obtained as a function of the photon energy and of the target mass number.

Differential cross sections for the processes e + e − → e + e − (Bhabha scattering) and e + e − → γγ have been measured with the TOPAZ detector at s =52 GeV . The results agree with the predictions of quantum electrodynamics (QED). The lower limits for the QED cut-off parameters have been obtained to be Λ + ⩾115 GeV and Λ − ⩾236 GeV for Bhabha scattering, and Λ + ⩾94 GeV and Λ − ⩾59 GeV for the reaction e + e − → γγ .

Momentum spectra of protons in the reactions of ..gamma..+Be..-->..p+anything and ..gamma..+C..-->..p+anything were measured in the photon energy range from 180 to 420 MeV for beryllium and from 340 to 580 MeV for carbon by use of a tagged photon beam. The spectrum obtained shows two peaks which are interpreted to be due to the protons in the reactions ..gamma..+''Nclzquo..-->..p+..pi.. and ..gamma..+''pnclzquo..-->..p+n, where ''Nclzquo and ''pnclzquo are the quasifree nucleons and proton-neutron systems in the target nuclei. .ID CW2014 .PG 46 56

High-statistics data on the reaction ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}n$ at 8.06 GeV/c were obtained. An isobarmodel partial-wave analysis was performed for the $\ensuremath{\eta}\ensuremath{\pi}\ensuremath{\pi}$ system. The $\ensuremath{\eta}(1275)$ meson was confirmed as a narrow $I{J}^{\mathrm{PC}}={00}^{\ensuremath{-}+}$ resonance. It decays through both $\ensuremath{\delta}\ensuremath{\pi}$ and $\ensuremath{\epsilon}\ensuremath{\eta}$. A narrow state with $I{J}^{\mathrm{PC}}={00}^{\ensuremath{-}+}$ was found in an $\ensuremath{\eta}\ensuremath{\pi}\ensuremath{\pi}$ decay channel at 1.42 GeV. It has a prominent peak in a $\ensuremath{\delta}\ensuremath{\pi}$ decay mode. No significant $E(1420)$ signal with $I{J}^{\mathrm{PC}}={01}^{++}$ was found near the mass region of 1.42 GeV.

A photon tagging system which determines the energy of each photon in the bremsstrahlung process is constructed, and is tested using an extracted electron beam from the 1.3 GeV electron synchrotron at the Institute for Nuclear Study, University of Tokyo. The system which consists of an analyzing magnet and twenty-five tagging counters detects the recoil electrons in the energy range from 100 MeV to 350 MeV. The energy of each tagged photon has been calibrated with a total absorption type lead glass Cerenkov counter. A good agreement within the error of ±10 MeV is obtained between the energy measured by the Cerenkov counter and the one calculated from the trajectory of the recoil electron. From the first experiment using this system, it is found that the intensity of the tagged photon beam is limited to 105 photons/s.

The cross sections of the reactions (\ensuremath{\gamma},p), (\ensuremath{\gamma},pn), and (\ensuremath{\gamma},pp) are measured for $^{1}\mathrm{H}$, $^{2}\mathrm{H}$, $^{9}\mathrm{Be}$, $^{12}\mathrm{C}$, and $^{16}\mathrm{O}$ in the \ensuremath{\Delta}(1232) resonance region by use of a tagged photon beam. Protons emitted at ${\ensuremath{\theta}}_{\mathrm{p}=30}$\ifmmode^\circ\else\textdegree\fi{} are measured by a magnetic spectrometer, and the other neutrons or protons are measured by an array of scintillation counter hodoscopes. From the present experiment, it is concluded that the reactions, \ensuremath{\gamma}+``N''\ensuremath{\rightarrow}p+\ensuremath{\pi} and \ensuremath{\gamma}+``pn''\ensuremath{\rightarrow}p+n, contribute dominantly to the (\ensuremath{\gamma},p) reaction in this energy region, where ``N'' denotes the nucleon and ``pn'' denotes the pn system in the nucleus.

Differential cross sections of the reaction γp→ηp have been measured by using a tagged photon beam in the energy range from 808 MeV to 1008 MeV at θ * η =45°C, 80°C, 100°C and 110°C. Photon couplings of nucleon resonances with masses below 1700 MeV are determined by a partial wave analysis of the reaction γp→ηp based on the isobar model. Results are compared with photon-couplings obtained by the analysis of the reaction γN→πN and by the quark model calculation.

The momentum spectra of the photoproduced positive and negative pions from the reaction γ p →ππ N have been measured using a tagged photon beam in the energy range from 710 MeV to 950 MeV. A magnetic spectrometer at 40° in the laboratory system is used to detect positive and negative pions. A hodoscope array which surrounded the liquid hydrogen target was used to identify the double pion photoproduction process. From the measured momentum spectra, the cross sections of the reaction, γ+ p → Δ +π were extracted. The results are well reproduced by the coherent sum of GIOPE rnodel and s -channel resonance contributions.

The differential cross sections for the reaction γ + n → π 0 + n have been measured at pions angles of 45°, 60°, 105°, 120° and 140° in the c.m.s. for photon energies of 500–900 MeV. Both π 0 meson and recoil neutron from a liquid deuterium target were detected with a pair of Cerenkov counters combined with lead spark chambers and a hodoscope consisting of 16 modules of plastic scintillation counters. The experimental results were compared with the recent phenomenological partial-wave analysis, and indicate that the ratio of the isoscalar part to the isovector part of the resonant amplitude of B 2 _(N′(1520)(D 13 )) is only about 0.2, and that in the γ + n → π 0 + n reaction there is no remarkable enhancement due to the N′(1470)(P 11 ) resonance.

Momentum spectra of protons in the reaction of $\ensuremath{\gamma}+\mathrm{Be}\ensuremath{\rightarrow}p$ + anything in the incident energy range from 180 to 420 MeV were measured. The spectrum obtained shows two peaks which are interpreted to be due to the protons in reactions $\ensuremath{\gamma}+``N''\ensuremath{\rightarrow}p+\ensuremath{\pi}$ and $\ensuremath{\gamma}+``d''\ensuremath{\rightarrow}p+n$, where $``N''$ and $``d''$ are the quasifree nucleons and neutron-proton systems, respectively, in the beryllium nucleus.

The momentum distributions of projectile-like fragments produced in the 40 Ar+ 9 Be reaction at E / A =90 MeV and the 16 O+ 12 C reaction at E / A =290 MeV were observed. A correlation between the width of the transverse momentum distribution and the velocity was found at E / A =90 MeV. Coulomb final-state interaction and AMD calculation cannot explain this correlation. A good agreement between EPAX2 and the production cross sections derived from observed momentum distribution of the fragments was found.