Tue·Dec 22, 2015Tuesday·December 22, 2015

1. 01*

   Centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   ALICE Collaboration

   The pseudorapidity density of charged particles ($\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta$) at mid-rapidity in Pb-Pb collisions has been measured at a center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV. It increases with centrality and reaches a value of $1943\pm 54$ in $|\eta |<0.5$ for the 5% most central collisions. A rise in $\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta$ as a function of $\sqrt{s_{\mathrm{NN}}}$ for the most central collisions is observed, steeper than that observed in proton-proton collisions and following the trend established by measurements at lower energy. The centrality dependence of $\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta$ as a function of the average number of participant nucleons, $⟨N_{\mathrm{part}}⟩$, calculated in a Glauber model, is compared with the previous measurement at lower energy. A constant factor of about 1.2 describes the increase in $\frac{2}{⟨N_{\mathrm{part}}⟩}⟨\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta ⟩$ from $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV to $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV for all centrality intervals, within the measured range of 0-80% centrality. The results are also compared to models based on different mechanisms for particle production in nuclear collisions.

   nucl-exhep-exPRL(2016)·455 citations
2. 02*

   Study of the 238U(d,p) surrogate reaction via the simultaneous measurement of gamma-decay and fission probabilities

   Q. Ducasse🇫🇷 · B. Jurado🇫🇷 · M. Aïche🇫🇷 · P. Marini🇫🇷 · L. Mathieu🇫🇷 · A. Görgen🇳🇴 · M. Guttormsen🇳🇴 · A. C. Larsen🇳🇴 · T. Tornyi🇳🇴 · J. N. Wilson🇫🇷 · G. Barreau🇫🇷 · G. Boutoux🇫🇷 and 17 other authors

   We investigated the 238U(d,p) reaction as a surrogate for the n + 238U reaction. For this purpose we measured for the first time the gamma-decay and fission probabilities of 239U* simultaneously and compared them to the corresponding neutron-induced data. We present the details of the procedure to infer the decay probabilities, as well as a thorough uncertainty analysis, including parameter correlations. Calculations based on the continuum-discretized coupled-channels and distorted-wave Born approximations were used to correct our data from detected protons originating from elastic and inelastic deuteron breakup. In the region where the fission and gamma-decay probabilities compete, the corrected fission probability is in agreement with neutron-induced data, whereas the gamma-decay probability is much higher than the neutron-induced data. The performed statistical-model calculations are not able to explain these results.

   nucl-exPRC(2016)·41 citations
3. 03*

   $\gamma$-soft ${}^{146}$Ba and the role of non-axial shapes at N ~ 90

   A. J. Mitchell🇺🇸 · C. J. Lister🇺🇸 · E. A. McCutchan🇺🇸 · M. Albers🇺🇸 · A. D. Ayangeakaa🇺🇸 · P. F. Bertone🇺🇸 · M. P. Carpenter🇺🇸 · C. J. Chiara🇺🇸 · P. Chowdhury🇺🇸 · J. A. Clark🇺🇸 · P. Copp🇺🇸 · H. M. David🇺🇸 and 20 other authors

   Low-spin states in the neutron-rich, N = 90 nuclide ${}^{146}$Ba were populated following $\beta$-decay of ${}^{146}$Cs, with the goal of clarifying the development of deformation in Ba isotopes through delineation of their non-yrast structures. Fission fragments of ${}^{146}$Cs were extracted from a 1.7-Ci ${}^{252}$Cf source and mass-selected using the CARIBU facility. Low-energy ions were deposited at the center of a box of thin $\beta$ detectors, surrounded by a high-efficiency HPGe array. The new ${}^{146}$Ba decay scheme now contains 31 excited levels extending up to ~2.5 MeV excitation energy, double what was previously known. These data are compared to predictions from the Interacting Boson Approximation (IBA) model. It appears that the abrupt shape change found at N = 90 in Sm and Gd is much more gradual in Ba and Ce, due to an enhanced role of the $\gamma$ degree of freedom.

   nucl-exPRC(2016)·16 citations
4. 04*

   Shedding New Light on Kaon-Nucleon/Nuclei Interaction and Its Astrophysical Implications with the AMADEUS Experiment at DAFNE

   A. Scordo🇮🇹 · M. Bazzi🇮🇹 · G. Bellotti🇮🇹 · C. Berucci🇦🇹 · D. Bosnar🇭🇷 · A.M. Bragadireanu🇷🇴 · A. Clozza🇮🇹 · M. Cargnelli🇦🇹 · C. Curceanu🇮🇹 · A. Dawood Butt🇮🇹 · R. Del Grande🇮🇹 · L. Fabbietti🇩🇪 and 15 other authors

   The AMADEUS experiment deals with the investigation of the low-energy kaon-nuclei hadronic interaction at the DA{\Phi}NE collider at LNF-INFN, which is fundamental to respond longstanding questions in the non-perturbative QCD strangeness sector. The antikaon-nucleon potential is investigated searching for signals from possible bound kaonic clusters, which would open the possibility for the formation of cold dense baryonic matter. The confirmation of this scenario may imply a fundamental role of strangeness in astrophysics. AMADEUS step 0 consisted in the reanalysis of 2004/2005 KLOE dataset, exploiting K- absorptions in H, 4He, 9Be and 12C in the setup materials. In this paper, together with a review on the multi-nucleon K- absorption and the particle identification procedure, the first results on the {\Sigma}0-p channel will be presented including a statistical analysis on the possible accomodation of a deeply bound state

   nucl-exAIP Conf.Proc.(2016)·8 citations
5. 05*

   The latest STAR results on quarkonium production

   Barbara Trzeciak (for the STAR Collaboration)🇨🇿

   We report the latest results of J/psi, psi(2S) and Upsilon production in the dielectron decay channel at mid-rapidity, from the STAR experiment. We present J/psi cross section measurements in p+p collisions at 200 and 500 GeV, as well as the first measurement of the psi(2S) to J/psi ratio at 500 GeV. We also show J/psi and Upsilon production in heavy ion collisions: J/psi nuclear modification factors (R_{AA}) in Au+Au collisions at 200, 62.4 and 39 GeV and in U+U collisions at 193 GeV, Upsilon R_{AA} in d+Au, Au+Au and U+U collisions at 200, 200 and 193 GeV, respectively. The results are compared to different model calculations.

   nucl-exhep-exActa Phys.Polon.Supp.(2015)·0 citations
6. 06*

   STAR's latest results on quarkonium production

   Barbara Trzeciak (for the STAR Collaboration)🇨🇿

   In this proceedings, we report the latest results of J/psi and Upsilon production from the STAR experiment at RHIC, in different colliding systems and colliding energies. J/psi nuclear modification factors (R_{AA}) in Au+Au collisions at 200, 62.4 and 39 GeV and in U+U collisions at 193 GeV, Upsilon R_{AA} in d+Au and Au+Au collisions at 200 and in U+U collisions at 193 GeV are shown and compared to different theoretical models. We also present prospects of quarkonium measurements at STAR.

   nucl-exhep-ex0 citations
7. 07*

   Total kinetic energy release in the fast neutron-induced fission of ${}^{235}$U

   R. Yanez · W. Loveland · J. King · J.S. Barrett · N. Fotiades · H.Y. Lee

   We have measured the total kinetic energy (TKE) release for the ${}^{235}$U(n,f) reaction for $E_n$=2-100 MeV using the 2E method with an array of Si PIN diode detectors. The neutron energies were determined by time of flight measurements using the white spectrum neutron beam at the LANSCE facility. (To calibrate the apparatus, the TKE release for ${}^{235}$U(n${}_{th}$,f) was also measured using a thermal neutron beam from the OSU TRIGA reactor). The TKE decreases non-linearly from 169.0 MeV to 161.4 MeV for $E_n$=2-90 MeV. The standard deviation of the TKE distribution is constant from $E_n$=20-90 MeV. Comparison of the data with the multi-modal fission model of Brosa indicates the TKE decrease is a consequence of the growth of symmetric fission and the corresponding decrease of asymmetric fission with increasing neutron energy. The average TKE associated with the Brosa superlong, standard I and standard II modes for a given mass is independent of neutron energy.

   nucl-exnucl-thEPJA(2017)·16 citations
8. 08*

   Correlated fluctuations near the QCD critical point

   Lijia Jiang🇨🇳 · Pengfei Li🇨🇳 · Huichao Song (Peking U.)🇨🇳

   In this paper, we introduce a freeze-out scheme for the dynamical models near the QCD critical point through coupling the decoupled classical particles with the order parameter field. With a modified distribution function that satisfies specific static fluctuations, we calculate the correlated fluctuations of net protons on the hydrodynamic freeze-out surface. A comparison with recent STAR data shows that our model calculations could roughly reproduce energy dependent cumulant $C_4$ and $\kappa {\sigma }^2$ of net protons through tuning the related parameters. However, the calculated $C_2$ and $C_3$ with both Poisson and Binomial baselines are always above the experimental data due to the positive contributions from the static critical fluctuations. In order to qualitatively and quantitatively describe the experimental data, the dynamical critical fluctuations and more realistic non-critical fluctuation baselines should be investigated in the near future.

   ↳ nucl-thhep-phnucl-exPRC(2016)·69 citations
9. 09*

   PARTONS: PARtonic Tomography Of Nucleon Software. A computing framework for the phenomenology of Generalized Parton Distributions

   B. Berthou🇫🇷 · D. Binosi🇮🇹 · N. Chouika🇫🇷 · L. Colaneri🇫🇷 · M. Guidal🇫🇷 · C. Mezrag🇺🇸 · H. Moutarde🇫🇷 · J. Rodríguez-Quintero🇪🇸 · F. Sabatié🇫🇷 · P. Sznajder🇵🇱 · J. Wagner🇵🇱

   We describe the architecture and functionalities of a C++ software framework, coined PARTONS, dedicated to the phenomenology of Generalized Parton Distributions. These distributions describe the three-dimensional structure of hadrons in terms of quarks and gluons, and can be accessed in deeply exclusive lepto- or photo-production of mesons or photons. PARTONS provides a necessary bridge between models of Generalized Parton Distributions and experimental data collected in various exclusive production channels. We outline the specification of the PARTONS framework in terms of practical needs, physical content and numerical capacity. This framework will be useful for physicists - theorists or experimentalists - not only to develop new models, but also to interpret existing measurements and even design new experiments.

   ↳ hep-phhep-exnucl-exnucl-th+1EPJC(2018)·136 citations
10. 10*

    The X-Array and SATURN: A new decay-spectroscopy station for CARIBU

    A.J. Mitchell🇺🇸 · P.F. Bertone🇺🇸 · B. DiGiovine🇺🇸 · C.J. Lister🇺🇸 · M. P. Carpenter🇺🇸 · P. Chowdhury🇺🇸 · J.A. Clark · N. D'Olympia · A.Y. Deo · F.G. Kondev🇺🇸 · E.A. McCutchan🇺🇸 · J. Rohrer and 3 other authors

    A new decay-spectroscopy station has been commissioned for experiments with low-energy, fission-fragment radioactive beams from the CARIBU ion source. The new set-up consists of the 'X-array', a highly-efficient array of HPGe clover detectors, and 'SATURN' (Scintillator And Tape Using Radioactive Nuclei), a plastic scintillator detector combined with a tape-transport system for detection of beta particles and removal of long-lived isobaric decay products.

    ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2014)·24 citations
11. 11*

    Does non-monotonic behavior of directed flow signal the onset of deconfinement?

    Yasushi Nara🇯🇵 · Akira Ohnishi🇯🇵

    We investigate the effects of nuclear mean-field as well as the formation and decay of nuclear clusters on the directed flow $v_1$ in high energy nucleus-nucleus collisions from $\sqrt{s_{NN}}=7.7$ GeV to 27 GeV incident energies within a transport model. Specifically, we use the JAM transport model in which potentials are implemented based on the framework of the relativistic quantum molecular dynamics. Our approach reproduces the rapidity dependence of directed flow data up to $\sqrt{s_{NN}}\approx 8$ GeV showing the significant importance of mean-field. However, the slopes of $d{v}_1/dy$ at mid-rapidity are calculated to be positive at $\sqrt{s_{NN}}=11.7$ and 19.6 GeV, and becomes negative above 27 GeV. Thus the result from the JAM hadronic transport model with nuclear mean-field approach is incompatible with the data. Therefore within our approach, we conclude that the excitation function of the directed flow cannot be explained by the hadronic degree of freedom alone.

    ↳ nucl-thhep-phnucl-exNPA(2016)·11 citations
12. 12*

    Elliptic Anisotropy $v_2$ May Be Dominated by Particle Escape instead of Hydrodynamic Flow

    Zi-Wei Lin🇺🇸 · Liang He🇺🇸 · Terrence Edmonds🇺🇸 · Feng Liu🇨🇳 · Denes Molnar🇺🇸 · Fuqiang Wang🇺🇸

    It is commonly believed that azimuthal anisotropies in relativistic heavy ion collisions are generated by hydrodynamic evolution of the strongly interacting quark-gluon plasma. Here we use transport models to study how azimuthal anisotropies depend on the number of collisions that each parton suffers. We find that the majority of $v_2$ comes from the anisotropic escape of partons, not from the parton collective flow, for semi-central Au+Au collisions at 200A GeV. As expected, the fraction of $v_2$ from the anisotropic particle escape is even higher for smaller systems such as d+Au. Our transport model results also confirm that azimuthal anisotropies would be dominated by hydrodynamic flow at unrealistically-high parton cross sections. Our finding thus naturally explains the similarity of azimuthal anisotropies in small and large systems; however, it presents a challenge to the paradigm of anisotropic flow.

    ↳ nucl-thnucl-exNPA(2016)·43 citations
13. 13*

    Development of a low background liquid scintillation counter for a shallow underground laboratory

    J. L. Erchinger · C. E. Aalseth🇺🇸 · B. E. Bernacki · M. Douglas · E. S. Fuller · M. E. Keillor · S. M. Morley · C. A. Mullen · J. L. Orrell🇺🇸 · M. E. Panisko · G. A. Warren🇺🇸 · R. O. Williams · M. E. Wright

    Pacific Northwest National Laboratory has recently opened a shallow underground laboratory intended for measurement of low-concentration levels of radioactive isotopes in samples collected from the environment. The development of a low-background liquid scintillation counter is currently underway to further augment the measurement capabilities within this underground laboratory. Liquid scintillation counting is especially useful for measuring charged particle (e.g., $\beta$, $\alpha$) emitting isotopes with no (or very weak) gamma-ray yields. The combination of high-efficiency detection of charged particle emission in a liquid scintillation cocktail coupled with the low-background environment of an appropriately-designed shield located in a clean underground laboratory provides the opportunity for increased-sensitivity measurements of a range of isotopes. To take advantage of the 35 meters-water-equivalent overburden of the underground laboratory, a series of simulations have evaluated the scintillation counter's shield design requirements to assess the possible background rate achievable. This report presents the design and background evaluation for a shallow underground, low background liquid scintillation counter design for sample measurements.

    ↳ physics.ins-detnucl-exAppl.Radiat.Isot.(2015)·4 citations
14. 14*

    Constituent-counting rule in photoproduction of hyperon resonances

    Wen-Chen Chang (Taiwan, Inst. Phys.)🇹🇼 · S. Kumano (KEK, Tsukuba and J-PARC, Tokai)🇯🇵 · Takayasu Sekihara (RCNP, Osaka U.)🇯🇵

    We analyze the CLAS data on the photoproduction of hyperon resonances, as well as the available data for the ground state $\Lambda$ and ${\Sigma }^0$ of the CLAS and SLAC-E84 collaborations, by considering constituent-counting rule suggested by perturbative QCD. The counting rule emerges as a scaling behavior of cross sections in hard exclusive reactions with large scattering angles, and it enables us to determine the number of elementary constituents inside hadrons. Therefore, it could be used as a new method for identifying internal constituents of exotic-hadron candidates. From the analyses of the $\gamma p\to K^{+}\Lambda$ and $K^{+}{\Sigma }^0$ reactions, we find that the number of the elementary constituents is consistent with $n_{\gamma }=1$, $n_p=3$, $n_{K^{+}}=2$, and $n_{\Lambda }=n_{{\Sigma }^0}=3$. Then, the analysis is made for the photoproductions of the hyperon resonances $\Lambda (1405)$, $\Sigma (1385{)}^0$, and $\Lambda (1520)$, where $\Lambda (1405)$ is considered to be a $\bar{K}N$ molecule and hence its constituent number could be five. However, we find that the current data are not enough to conclude the numbers of their constituent. It is necessary to investigate the higher-energy region at $\sqrt{s}>2.8$ GeV experimentally beyond the energy of the available CLAS data for counting the number of constituents clearly. We also mention that our results indicate energy dependence in the constituent number, especially for $\Lambda (1405)$. If an excited hyperon is a mixture of three-quark and five-quark states, the energy dependence of the scaling behavior could be valuable for finding its composition and mixture.

    ↳ hep-phhep-exnucl-exnucl-thPRD(2016)·24 citations
15. 15*

    Investigating the Spectral Anomaly with Different Reactor Antineutrino Experiments

    Christian Buck🇩🇪 · Antoine P. Collin🇩🇪 · Julia Haser🇩🇪 · Manfred Lindner🇩🇪

    The spectral shape of reactor antineutrinos measured in recent experiments shows anomalies in comparison to neutrino reference spectra. New precision measurements of the reactor neutrino spectra as well as more complete input in nuclear data bases are needed to resolve the observed discrepancies between models and experimental results. This article proposes the combination of experiments at reactors which are highly enriched in ${}^{235}$U with commercial reactors with typically lower enrichment to gain new insights into the origin of the anomalous neutrino spectrum. The presented method clarifies, if the spectral anomaly is either solely or not at all related to the predicted ${}^{235}$U spectrum. Considering the current improvements of the energy scale uncertainty of present-day experiments, a significance of three sigma and above can be reached. As an example, we discuss the option of a direct comparison of the measured shape in the currently running Double Chooz near detector and the upcoming Stereo experiment. A quantitative feasibility study emphasizes that a precise understanding of the energy scale systematics is a crucial prerequisite in recent and next generation experiments investigating the spectral anomaly.

    ↳ hep-exnucl-exphysics.ins-detPLB(2017)·51 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.