Fri·Mar 20, 2015Friday·March 20, 2015

1. 01*

   New measurement of the excited states in ${}^{11}$B via the elastic resonance scattering of ${}^{10}$Be + p

   Y. D. Liu · H. W. Wang🇨🇳 · Y. G. Ma🇨🇳 · X. G. Cao🇨🇳 · G. Q. Zhang🇨🇳 · D. Q. Fang🇨🇳 · M. Lyu · W. B. He · Z. T. Dai · C. Li🇨🇳 · C. L. Zhou🇨🇳 · S. Q. Ye and 12 other authors

   The elastic resonance scattering protons decayed from ${}^{11}$B to the ground state of ${}^{10}$Be were measured using the thick-target technique in inverse kinematics at the Heavy Ion Research Facility in Lanzhou (HIRFL). The obtained excitation functions were well described by a multichannel R-matrix procedure under the kinematics process assumption of resonant elastic scattering. The excitation energy of the resonant states ranges from 13.0 to 17.0 MeV, and their resonant parameters such as the resonant energy E${}_x$, the spin-parity J${}^{\pi }$, and the proton-decay partial width ${\Gamma }_p$ were determined from R-matrix fits to the data. Two of these states around E${}_x$ = 14.55 MeV [J${}^{\pi }$ = (3/2${}^{+}$, 5/2${}^{+}$), ${\Gamma }_p$ = 475 $\pm$ 80 keV] and E${}_x$ = 14.74 MeV [J${}^{\pi }$ = 3/2${}^{-}$, ${\Gamma }_p$ = 830 $\pm$ 145 keV], and a probably populated state at E${}_x$ = 16.18 MeV [J${}^{\pi }$ =(1/2${}^{-}$, 3/2${}^{-}$), ${\Gamma }_p$ $<$ 60 keV], are respectively assigned to the well-known states in ${}^{11}$B at 14.34 MeV, 15.29 MeV, and 16.43 MeV. The isospin of these three states were previously determined to be T = 3/2, but discrepancies exist in widths and energies due to the current counting statistics and energy resolution. We have compared these states with previous measurements, and the observation of the possibly populated resonance is discussed.

   nucl-exnucl-thPRC(2015)·2 citations
2. 02*

   Different mechanism of two-proton emission from proton-rich nuclei ${}^{23}$Al and ${}^{22}$Mg

   Y.G. Ma🇨🇳 · D.Q. Fang🇨🇳 · X.Y. Sun🇨🇳 · P. Zhou🇨🇳 · Y. Togano🇯🇵 · N. Aoi🇯🇵 · H. Baba🇯🇵 · X.Z. Cai🇨🇳 · X.G. Cao🇨🇳 · J.G. Chen🇨🇳 · Y. Fu🇨🇳 · W. Guo🇨🇳 and 34 other authors

   Two-proton relative momentum ($q_{pp}$) and opening angle (${\theta }_{pp}$) distributions from the three-body decay of two excited proton-rich nuclei, namely ${}^{23}$Al $\to$ p + p + ${}^{21}$Na and ${}^{22}$Mg $\to$ p + p + ${}^{20}$Ne, have been measured with the projectile fragment separator (RIPS) at the RIKEN RI Beam Factory. An evident peak at $q_{pp}\sim 20$ MeV/c as well as a peak in ${\theta }_{pp}$ around 30${}^{\circ }$ are seen in the two-proton break-up channel from a highly-excited ${}^{22}$Mg. In contrast, such peaks are absent for the ${}^{23}$Al case. It is concluded that the two-proton emission mechanism of excited ${}^{22}$Mg is quite different from the ${}^{23}$Al case, with the former having a favorable diproton emission component at a highly excited state and the latter dominated by the sequential decay process.

   nucl-exnucl-thPLB(2015)·41 citations
3. 03*

   Evidence for $\Delta (2200)7/2^{-}$ from photoproduction and consequence for chiral-symmetry restoration at high mass

   A.V. Anisovich🇩🇪 · V. Burkert🇺🇸 · J. Hartmann🇩🇪 · E. Klempt🇩🇪 · V.A. Nikonov🇩🇪 · E. Pasyuk🇺🇸 · A.V. Sarantsev🇩🇪 · S. Strauch🇺🇸 · U. Thoma🇩🇪

   We report a partial-wave analysis of new data on the double-polarization variable $E$ for the reactions $\gamma p\to {\pi }^{+}n$ and $\gamma p\to {\pi }^{0}p$ and of further data published earlier. The analysis within the Bonn-Gatchina (BnGa) formalism reveals evidence for a poorly known baryon resonance, the one-star $\Delta (2200)7/2^{-}$. This is the lowest-mass ${\Delta }^{\ast }$ resonance with spin-parity $J^P=7/2^{-}$. Its mass is significantly higher than the mass of its parity partner $\Delta (1950)7/2^{+}$ which is the lowest-mass ${\Delta }^{\ast }$ resonance with spin-parity $J^P=7/2^{+}$. It has been suggested that chiral symmetry might be restored in the high-mass region of hadron excitations, and that these two resonances should be degenerate in mass. Our findings are in conflict with this prediction.

   nucl-exnucl-thPLB(2017)·32 citations
4. 04*

   Broad resonances and beta-decay

   K. Riisager🇩🇰 · H.O.U. Fynbo🇩🇰 · S. Hyldegaard · A.S. Jensen🇩🇰

   Beta-decay into broad resonances gives a distorted lineshape in the observed energy spectrum. Part of the distortion arises from the phase space factor, but we show that the beta-decay matrix element may also contribute. Based on a schematic model for p-wave continuum neutron states it is argued that beta-decay directly to the continuum should be considered as a possible contributing mechanism in many decays close to the driplines. The signatures in R-matrix fits for such decays directly to continuum states are discussed and illustrated through an analysis of the beta-decay of ${}^8$B into $2^{+}$ states in ${}^8$Be.

   nucl-exnucl-thNPA(2015)·7 citations
5. 05*

   Study of W boson production in pPb collisions at sqrt(s[NN]) = 5.02 TeV

   CMS Collaboration

   The first study of W boson production in pPb collisions is presented, for bosons decaying to a muon or electron, and a neutrino. The measurements are based on a data sample corresponding to an integrated luminosity of 34.6 inverse nanobarns at a nucleon-nucleon centre-of-mass energy of sqrt(s[NN]) = 5.02 TeV, collected by the CMS experiment. The W boson differential cross sections, lepton charge asymmetry, and forward-backward asymmetries are measured for leptons of transverse momentum exceeding 25 GeV, and as a function of the lepton pseudorapidity in the abs(eta[lab]) < 2.4 range. Deviations from the expectations based on currently available parton distribution functions are observed, showing the need for including W boson data in nuclear parton distribution global fits.

   nucl-exhep-exPLB(2015)·116 citations
6. 06*

   A Helium Gas-Scintillator Active Target for Photoreaction Measurements

   R. Al Jebali🇬🇧 · J.R.M. Annand🇬🇧 · J.-O. Adler · I. Akkurt · E. Buchanan🇬🇧 · J. Brudvik🇸🇪 · K. Fissum🇸🇪 · S. Gardner🇬🇧 · D.J. Hamilton🇬🇧 · K. Hansen🇸🇪 · L. Isaksson🇸🇪 · K. Livingston and 11 other authors

   A multi-cell He gas-scintillator active target, designed for the measurement of photoreaction cross sections, is described. The target has four main chambers, giving an overall thickness of 0.103 $g/c{\mathrm{m}}^2$ at an operating pressure of 2 MPa. Scintillations are read out by photomultiplier tubes and the addition of small amounts of ${\mathrm{N}}_2$ to the He, to shift the scintillation emission from UV to visible, is discussed. First results of measurements at the MAX IV Laboratory tagged-photon facility show that the target has good timing resolution and can cope well with a high-flux photon beam. The determination of reaction cross sections from target yields relies on a Monte Carlo simulation, which considers scintillation light transport, photodisintegration processes in ${}^4\mathrm{He}$, background photon interactions in target windows and interactions of the reaction-product particles in the gas and target container. The predictions of this simulation are compared to the measured target response.

   ↳ physics.ins-detnucl-exEPJA(2015)·3 citations
7. 07*

   Interferometric signatures of the temperature dependence of the specific shear viscosity in heavy-ion collisions

   Christopher Plumberg🇺🇸 · Ulrich Heinz🇺🇸

   Recent work has shown that a temperature dependence of the shear viscosity to entropy ratio, $\eta /s$, influences the collective flow pattern in heavy-ion collisions in characteristic ways that can be measured by studying hadron transverse momentum spectra and their anisotropies. Here we point out that it also affects the pair momentum dependence of the Hanbury-Brown$-$Twiss (HBT) radii (the source size parameters extracted from two-particle intensity interferometry) and the variance of their event-by-event fluctuations. This observation establishes interferometric signatures as useful observables to complement the constraining power of single-particle spectra on the temperature dependence of $\eta /s$.

   ↳ nucl-thnucl-exPRC(2015)·14 citations
8. 08*

   Event simulations in a transport model for intermediate energy heavy ion collisions: Applications to multiplicity distributions

   S. Mallik🇮🇳 · S. Das Gupta · G. Chaudhuri🇮🇳

   We perform transport model calculations for central collisions of mass 120 on mass 120 at laboratory beam energy in the range 20 MeV/nucleon to 200 MeV/nucleon. A simplified yet accurate method allows calculation of fluctuations in systems much larger than what was considered feasible in a well-known and already existing model. The calculations produce clusters. The distribution of clusters is remarkably similar to that obtained in equilibrium statistical model.

   ↳ nucl-thnucl-exPRC(2015)·32 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.