Tue·Jul 12, 2016Tuesday·July 12, 2016

1. 01*

   A Search for $0^{+}$ States in ${}^{50}$Cr: Implications for the Superallowed $\beta$-decay of ${}^{50}$Mn

   K.G. Leach🇺🇸 · P.E. Garrett🇨🇦 · G.C. Ball🇨🇦 · P.C. Bender🇨🇦 · V. Bildstein🇨🇦 · B.A. Brown🇺🇸 · C. Burbadge🇨🇦 · T. Faestermann🇩🇪 · B. Hadinia🇨🇦 · J.D. Holt🇨🇦 · A.T. Laffoley🇨🇦 · D.S. Jamieson and 7 other authors

   A ${}^{52}$Cr$(p,t)$${}^{50}$Cr two-neutron pickup reaction was performed using the Q3D magnetic spectrograph at the Maier-Leibnitz-Laboratorium in Garching, Germany. Excited states in ${}^{50}$Cr were observed up to an excitation energy of 5.3 MeV. Despite significantly increased sensitivity and resolution over previous work, no evidence of the previously assigned first excited $0^{+}$ state was found. As a result, the $0_2^{+}$ state is reassigned at an excitation energy of $E_x=3895.0(5)$ keV in ${}^{50}$Cr. This reassignment directly impacts direct searches for a non-analogue Fermi ${\beta }^{+}$ decay branch in ${}^{50}$Mn. These results also show better systematic agreement with the theoretical predictions for the $0^{+}$ state spectrum in ${}^{50}$Cr using the same formalism as the isospin-symmetry-breaking correction calculations for superallowed nuclei. The experimental data are also compared to $ab$-$initio$ shell-model predictions using the IM-SRG formalism based on $NN$ and $3N$ forces from chiral-EFT in the $pf$-shell for the first time.

   nucl-exnucl-thPRC(2016)·10 citations
2. 02*

   Reaction and fusion cross sections for the near-symmetric system ${}^{129}Xe{+}^{nat}Sn$ from $8$ to $35$ $AMeV$

   L. Manduci🇫🇷 · O. Lopez🇫🇷 · A. Chbihi🇫🇷 · M.F. Rivet🇫🇷 · R. Bougault🇫🇷 · J.D. Frankland🇫🇷 · B. Borderie🇫🇷 · E. Galichet🇫🇷 · M. La Commara🇮🇹 · N. Le Neindre🇫🇷 · I. Lombardo🇮🇹 · M. Pârlog🇫🇷 and 4 other authors

   \item[Background]Heavy-ion reactions from barrier up to Fermi energy. \item[Purpose]Reaction and fusion cross sections determination. Fusion reactions induced by ${}^{129}Xe$ projectiles on ${}^{nat}Sn$ targets for energies ranging from $8$ A.MeV to $35$ A.MeV were measured with the INDRA $4\pi$-array.\\ The evaluation of the fusion/incomplete fusion cross sections for the incident energies from 8 to 35 A.MeV is the main purpose of this paper. \item[Method] The reaction cross sections are evaluated for each beam energy thanks to INDRA $4\pi$-array. The events are also sorted in order to focus the study on a selected sample of events, in such a way that the fusion/fusion incomplete cross section is estimated. \item[Results] The excitation function of reaction and fusion cross sections were measured for the heavy and nearly symmetric system ${}^{129}Xe{+}^{nat}Sn$ from 8 to 35 A.MeV. \item[Conclusions] The fusion-like cross-sections evaluated show a good agrement with a recent systematics for beam energies greater than 20 A.MeV. For low beam energies the cross-section values are lower than the expected ones. A probable reason for these low values is in the fusion hindrance at energies above/close the barrier.

   nucl-exPRC(2016)·11 citations
3. 03*

   Mass ordering of spectra from fragmentation of saturated gluon states in high multiplicity proton-proton collisions

   Bjoern Schenke🇺🇸 · Soeren Schlichting🇺🇸 · Prithwish Tribedy🇺🇸 · Raju Venugopalan🇺🇸

   The mass ordering of mean transverse momentum $⟨p_T⟩$ and of the Fourier harmonic coefficient $v_2(p_T)$ of azimuthally anisotropic particle distributions in high energy hadron collisions is often interpreted as evidence for the hydrodynamic flow of the matter produced. We investigate an alternative initial state interpretation of this pattern in high multiplicity proton-proton collisions at the LHC. The QCD Yang-Mills equations describing the dynamics of saturated gluons are solved numerically with initial conditions obtained from the Color Glass Condensate based IP-Glasma model. The gluons are subsequently fragmented into various hadron species employing the well established Lund string fragmentation algorithm of the PYTHIA event generator. We find that this ab initio initial state approach reproduces characteristic features of bulk spectra, in particular the particle mass dependence of $⟨p_T⟩$ and $v_2(p_T)$.

   ↳ hep-phnucl-exnucl-thPRL(2016)·114 citations
4. 04*

   Parton Fragmentation Functions

   Andreas Metz🇺🇸 · Anselm Vossen🇺🇸

   The field of fragmentation functions of light quarks and gluons is reviewed. In addition to integrated fragmentation functions, attention is paid to the dependence of fragmentation functions on transverse momenta and on polarization degrees of freedom. Higher-twist and di-hadron fragmentation functions are considered as well. Moreover, the review covers both theoretical and experimental developments in single-inclusive hadron production in electron-positron annihilation, deep-inelastic lepton-nucleon scattering, and proton-proton collisions.

   ↳ hep-exhep-phnucl-exnucl-thPPNP(2016)·298 citations
5. 05*

   Detection System for Neutron $\beta$ Decay Correlations in the UCNB and Nab experiments

   L. J. Broussard🇺🇸 · B. A. Zeck🇺🇸 · E. R. Adamek🇺🇸 · S. Baeßler🇺🇸 · N. Birge🇺🇸 · M. Blatnik🇺🇸 · J. D. Bowman🇺🇸 · A. E. Brandt🇺🇸 · M. Brown🇺🇸 · J. Burkhart🇺🇸 · N. B. Callahan🇺🇸 · S. M. Clayton🇺🇸 and 42 other authors

   We describe a detection system designed for precise measurements of angular correlations in neutron $\beta$ decay. The system is based on thick, large area, highly segmented silicon detectors developed in collaboration with Micron Semiconductor, Ltd. The prototype system meets specifications for $\beta$ electron detection with energy thresholds below 10 keV, energy resolution of $\sim$3 keV FWHM, and rise time of $\sim$50 ns with 19 of the 127 detector pixels instrumented. Using ultracold neutrons at the Los Alamos Neutron Science Center, we have demonstrated the coincident detection of $\beta$ particles and recoil protons from neutron $\beta$ decay. The fully instrumented detection system will be implemented in the UCNB and Nab experiments, to determine the neutron $\beta$ decay parameters $B$, $a$, and $b$.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2017)·26 citations
6. 06*

   Large-scale shell-model calculations on the spectroscopy of $N<126$ Pb isotopes

   Chong Qi🇸🇪 · L.Y. Jia🇨🇳 · G.J. Fu🇨🇳

   Large-scale shell-model calculations are carried out in the model space including neutron-hole orbitals $2p_{1/2}$, $1f_{5/2}$, $2p_{3/2}$, $0i_{13/2}$, $1f_{7/2}$ and $0h_{9/2}$ to study the structure and electromagnetic properties of neutron deficient Pb isotopes. An optimized effective interaction is used. Good agreement between full shell-model calculations and experimental data is obtained for the spherical states in isotopes ${}^{194-206}$Pb. The lighter isotopes are calculated with an importance-truncation approach constructed based on the monopole Hamiltonian. The full shell-model results also agree well with our generalized seniority and nucleon-pair-approximation truncation calculations. The deviations between theory and experiment concerning the excitation energies and electromagnetic properties of low-lying $0^{+}$ and $2^{+}$ excited states and isomeric states may provide a constraint on our understanding of nuclear deformation and intruder configuration in this region.

   ↳ nucl-thnucl-exPRC(2016)·25 citations
7. 07*

   The anomalous quadrupole collectivity in Te isotopes

   Chong Qi🇸🇪

   We present systematic calculations on the spectroscopy and transition properties of even-even Te isotopes by using the large-scale configuration interaction shell model approach with a realistic interaction. These nuclei are of particular interest since their yrast spectra show a vibrational-like equally-spaced pattern but the few known E2 transitions show anomalous rotational-like behavior, which cannot be reproduced by collective models. Our calculations reproduce well the equally-spaced spectra of those isotopes as well as the constant behavior of the $B(E2)$ values in ${}^{114}$Te. The calculated $B(E2)$ values for neutron-deficient and heavier Te isotopes show contrasting different behaviors along the yrast line. The $B(E2)$ of light isotopes can exhibit a nearly constant bevavior upto high spins. We show that this is related to the enhanced neutron-proton correlation when approaching $N=50$.

   ↳ nucl-thnucl-exPRC(2016)·33 citations
8. 08*

   Hidden charm octet tetraquarks from a diquark-antidiquark model

   Ruilin Zhu🇨🇳

   Four exotic charmonium-like states, i.e. $X(4140)$, $X(4274)$, $X(4500)$, and $X(4700)$, have been observed very recently by LHCb Collaboration in the decay process $B^{+}\to J/\psi \varphi K^{+}$ using the 3${\mathrm{fb}}^{-1}$ data of $p\bar{p}$ collision at $\sqrt{s}=7$ and $8$ TeV. In this paper, we investigate systematically the properties of hidden charm tetraquark states. The hidden charm tetraquarks form an octet configuration and a singlet configuration according to flavor $SU(3)$ symmetry. Based on a diquark-antidiquark model, the hidden charm tetraquarks spectra are given. The previous XYZ exotic states altogether with the newly ones $X(4140)$, $X(4274)$, $X(4500)$, and $X(4700)$, can be well classified into certain representations. The spin-parities and masses of the XYZ are predicted, most of which are in agreement with the data. We particularly find that $Z_c(4430)$ may be treated as the first radial excitation of $Z_c(3900)$, while the $Y(1^{--})$ states can be obtained by the first orbital excitation of the $X/Z$ states. Besides, we calculate the decay widths of the hidden charm tetraquarks into two charmed mesons. This work gives a general tetraquark description for the XYZ states, which is helpful to uncover their inner structures.

   ↳ hep-phhep-exhep-latnucl-exPRD(2016)·50 citations
9. 09*

   Monopole excitation of the Hoyle state and linear-chain state in 12C

   Yasuro Funaki🇯🇵

   Background: Two new $J^{\pi }=0^{+}$ states are recently observed around a few MeV above the Hoyle state (the second $0^{+}$ state in 12C). The characters of them are only poorly discussed in theory and are still mysterious. Purpose: I give for the first time a comprehensive understanding of the structures of the $0^{+}$ states by analyzing their wave functions, and discuss relationship with the Hoyle state, similarities, and differences between the states. Method: I extend a microscopic $\alpha$-cluster model called Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function so as to incorporate $2\alpha +\alpha$ asymmetric configuration explicitly. The so-called $r^2$-constraint method to effectively eliminate spurious continuum components is also used. Results: The $0_3^{+}$ state is shown to have a very large squared overlap with a single configuration of the extended THSR wave function in an orthogonal space to the Hoyle state as well as to the ground state. The $0_4^{+}$ state has a maximal squared overlap with a single extended THSR wave function with an extremely prolately-deformed shape. Conclusions: The $0_3^{+}$ state appears as a family of the Hoyle state to have a higher nodal structure in the internal motions of the $3\alpha$ clusters, due to the orthogonalization to the Hoyle state. The $0_4^{+}$ state dominantly has a linear-chain structure, where the $3\alpha$ clusters move freely in a non-localized way, like a one-dimensional gas of the $3\alpha$ clusters.

   ↳ nucl-thnucl-exPRC(2016)·29 citations
10. 10*

    A new MC-based method to evaluate the fission fraction uncertainty at reactor neutrino experiment

    X.B. Ma🇨🇳 · R.M. Qiu🇨🇳 · Y.X. Chen🇨🇳

    Uncertainties of fission fraction is an important uncertainty source for the antineutrino flux prediction in a reactor antineutrino experiment. A new MC-based method of evaluating the covariance coefficients between isotopes was proposed. It was found that the covariance coefficients will varying with reactor burnup and which may change from positive to negative because of fissioning balance effect, for example, the covariance coefficient between ${}^{235}$U and ${}^{239}$Pu changes from 0.15 to -0.13. Using the equation between fission fraction and atomic density, the consistent of uncertainty of fission fraction and the covariance matrix were obtained. The antineutrino flux uncertainty is 0.55\% which does not vary with reactor burnup, and the new value is about 8.3\% smaller.

    ↳ hep-exnucl-exphysics.ins-detNPA(2017)·4 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.