Thu·May 14, 2015Thursday·May 14, 2015

1. 01*

   Simulation of the reaction of fragmentation of deuterons into cumulative and twice-cumulative pions

   A.G. Litvinenko🇷🇺 · E.I. Litvinenko🇷🇺

   The paper discusses the features of the behavior of pion production cross section as a function of the atomic mass of the target nucleus for the reaction of fragmentation of the incident deuterons in the pions produced in the so-called "twice-cumulative" kinematic region. A distinctive feature of the twice-cumulative pions is that for their production the target nucleus must be heavier than hydrogen. The simulation results show that the dependence of the cross sections for pion production in the twice-cumulative region differs from the analogous dependence for the cumulative region. The paper discusses the reasons for such differences. In this work we present simulation results for some models of nuclear structure on small nucleon-nucleon distances.

   nucl-exhep-ex0 citations
2. 02*

   Spallation reactions. A successful interplay between modeling and applications

   J.-C. David🇫🇷

   The spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. The first spallation reactions induced with an accelerator took place in 1947 at the Berkeley cyclotron (University of California) with 200 MeV deuterons and 400 MeV alpha beams. They highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. The same year R. Serber describes the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. In 2010 IAEA organized a worskhop to present the results of the most widely used spallation codes within a benchmark of spallation models. If one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improvements achieved since Serber. Particle transport codes can then rely on such spallation models to treat the reactions between a light particle and an atomic nucleus with energies spanning from few tens of MeV up to some GeV. An overview of the spallation reactions modeling is presented in order to point out the incomparable contribution of models based on basic physics to numerous applications where such reactions occur. Validations or benchmarks, which are necessary steps in the improvement process, are also addressed, as well as the potential future domains of development. Spallation reactions modeling is a representative case of continuous studies aiming at understanding a reaction mechanism and which end up in a powerful tool.

   nucl-exEPJA(2015)·48 citations
3. 03*

   Geometric phases in electric dipole searches with trapped spin-1/2 particles in general fields and measurement cells of arbitrary shape with smooth or rough walls

   R. Golub🇺🇸 · A. Steyerl🇺🇸 · C. Kaufman🇺🇸 · G. Müller🇩🇪

   The important role of geometric phases in searches for a permanent electric dipole moment of the neutron, using Ramsey separated oscillatory field nuclear magnetic resonance, was first noted by Commins and investigated in detail by Pendlebury et al. Their analysis was based on the Bloch equations. In subsequent work using the spin density matrix Lamoreaux and Golub showed the relation between the frequency shifts and the correlation functions of the fields seen by trapped particles in general fields (Redfield theory). More recently we presented a solution of the Schrödinger equation for spin-$1/2$ particles in circular cylindrical traps with smooth walls and exposed to arbitrary fields [Steyerl et al.] Here we extend this work to show how the Redfield theory follows directly from the Schrödinger equation solution. This serves to highlight the conditions of validity of the Redfield theory, a subject of considerable discussion in the literature [e.g., Nicholas et al.] Our results can be applied where the Redfield result no longer holds, such as observation times on the order of or shorter than the correlation time and non-stochastic systems and thus we can illustrate the transient spin dynamics, i.e. the gradual development of the shift with increasing time subsequent to the start of the free precession. We consider systems with rough, diffuse reflecting walls, cylindrical trap geometry with arbitrary cross section, and field perturbations that do not, in the frame of the moving particles, average to zero in time. We show by direct, detailed, calculation the agreement of the results from the Schrödinger equation with the Redfield theory for the cases of a rectangular cell with specular walls and of a circular cell with diffuse reflecting walls.

   nucl-exPRA(2015)·10 citations
4. 04*

   Bose-Einstein correlations in hadron-pairs from lepto-production on nuclei ranging from hydrogen to xenon

   HERMES Collaboration: A. Airapetian🇩🇪 · N. Akopov🇦🇲 · Z. Akopov🇩🇪 · E.C. Aschenauer🇩🇪 · W. Augustyniak🇵🇱 · R. Avakian🇦🇲 · A. Avetissian🇦🇲 · E. Avetisyan🇩🇪 · S. Belostotski🇷🇺 · N. Bianchi🇮🇹 · H.P. Blok🇳🇱 · A. Borissov🇩🇪 and 106 other authors

   Bose-Einstein correlations of like-sign charged hadrons produced in deep-inelastic electron and positron scattering are studied in the HERMES experiment using nuclear targets of ${}^1$H, ${}^2$H, ${}^3$He, ${}^4$He, N, Ne, Kr, and Xe. A Gaussian approach is used to parametrize a two-particle correlation function determined from events with at least two charged hadrons of the same sign charge. This correlation function is compared to two different empirical distributions that do not include the Bose-Einstein correlations. One distribution is derived from unlike-sign hadron pairs, and the second is derived from mixing like-sign pairs from different events. The extraction procedure used simulations incorporating the experimental setup in order to correct the results for spectrometer acceptance effects, and was tested using the distribution of unlike-sign hadron pairs. Clear signals of Bose-Einstein correlations for all target nuclei without a significant variation with the nuclear target mass are found. Also, no evidence for a dependence on the invariant mass W of the photon-nucleon system is found when the results are compared to those of previous experiments.

   ↳ hep-exnucl-exEPJC(2015)·4 citations
5. 05*

   A General Analysis of Direct Dark Matter Detection: From Microphysics to Observational Signatures

   James B. Dent (1)🇺🇸 · Lawrence M. Krauss (2,3)🇺🇸 · Jayden L. Newstead (2)🇺🇸 · Subir Sabharwal (2) ((1) University of Louisiana at Lafayette, (2) Arizona State University, (3) Australian National University)🇺🇸

   Beginning with a set of simplified models for spin-0, spin-$\text{half}$, and spin-1 dark matter candidates using completely general Lorentz invariant and renormalizable Lagrangians, we derive the full set of non-relativistic operators and nuclear matrix elements relevant for direct detection of dark matter, and use these to calculate rates and recoil spectra for scattering on various target nuclei. This allows us to explore what high energy physics constraints might be obtainable from direct detection experiments, what degeneracies exist, which operators are ubiquitous and which are unlikely or sub-dominant. We find that there are operators which are common to all spins as well operators which are unique to spin-$\text{half}$ and spin-1 and elucidate two new operators which have not been previously considered. In addition we demonstrate how recoil energy spectra can distinguish fundamental microphysics if multiple target nuclei are used. Our work provides a complete roadmap for taking generic fundamental dark matter theories and calculating rates in direct detection experiments. This provides a useful guide for experimentalists designing experiments and theorists developing new dark matter models.

   ↳ hep-phastro-ph.COhep-exnucl-ex+1PRD(2015)·106 citations
6. 06*

   Microscopic description of large amplitude collective motion in the nuclear astrophysics context

   Denis Lacroix🇫🇷 · Yusuke Tanimura🇫🇷 · Guillaume Scamps🇫🇷 · Cédric Simenel🇦🇺

   In the last 10 years, we have observed an important increase of interest in the application of time-dependent energy density functional theory (TD-EDF). This approach allows to treat nuclear structure and nuclear reaction from small to large amplitude dynamics in a unified framework. The possibility to perform unrestricted three-dimensional simulations using state of the art effective interactions has opened new perspectives. In the present article, an overview of applications where the predictive power of TD-EDF has been benchmarked is given. A special emphasize is made on processes that are of astrophysical interest. Illustrations discussed here include giant resonances, fission, binary and ternary collisions leading to fusion, transfer and deep inelastic processes.

   ↳ nucl-thastro-ph.SRnucl-exIJMPE(2015)·4 citations
7. 07*

   A new measurement of antineutrino oscillation with the full detector configuration at Daya Bay

   Daya Bay Collaboration: F. P. An🇨🇳 · A. B. Balantekin🇺🇸 · H. R. Band🇺🇸 · M. Bishai🇺🇸 · S. Blyth🇹🇼 · I. Butorov🇷🇺 · G. F. Cao🇨🇳 · J. Cao🇨🇳 · W. R. Cen🇨🇳 · Y. L. Chan🇨🇳 · J. F. Chang🇨🇳 · L. C. Chang🇹🇼 and 206 other authors

   We report a new measurement of electron antineutrino disappearance using the fully-constructed Daya Bay Reactor Neutrino Experiment. The final two of eight antineutrino detectors were installed in the summer of 2012. Including the 404 days of data collected from October 2012 to November 2013 resulted in a total exposure of 6.9$\times$10${}^5$ GW${}_{\mathrm{th}}$-ton-days, a 3.6 times increase over our previous results. Improvements in energy calibration limited variations between detectors to 0.2%. Removal of six ${}^{241}$Am-${}^{13}$C radioactive calibration sources reduced the background by a factor of two for the detectors in the experimental hall furthest from the reactors. Direct prediction of the antineutrino signal in the far detectors based on the measurements in the near detectors explicitly minimized the dependence of the measurement on models of reactor antineutrino emission. The uncertainties in our estimates of ${\sin }^{2}2{\theta }_{13}$ and $|\Delta m_{ee}^2|$ were halved as a result of these improvements. Analysis of the relative antineutrino rates and energy spectra between detectors gave ${\sin }^{2}2{\theta }_{13}=0.084\pm 0.005$ and $|\Delta m_{ee}^2|=(2.42\pm 0.11)\times 10^{-3}$ eV${}^2$ in the three-neutrino framework.

   ↳ hep-exnucl-exphysics.ins-detPRL(2015)·283 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.