Wed·Oct 5, 2011Wednesday·October 5, 2011

1. 01*

   Properties of the Lambda(1405) Measured at CLAS

   Kei Moriya🇺🇸 · Reinhard Schumacher (for the CLAS Collaboration)🇺🇸

   The nature of the Lambda(1405), and its place in the baryon spectrum has remained uncertain for decades. Theoretical studies have shown that it may possess strong dynamical components which are not seen in other well-known baryons. Using the CLAS detector system in Hall B at Jefferson Lab, we have measured the photoproduction reaction gamma+p->K+ Lambda(1405) with high statistics and over different Sigma pi decay channels. The reconstructed invariant mass distribution (lineshape) has been measured, as well as the differential cross sections for the Lambda(1405), Sigma(1385), and Lambda(1520). Our analysis method is discussed and our near-final results for the Lambda(1405) lineshape and differential cross section are presented.

   nucl-exAIP Conf.Proc.(2012)·4 citations
2. 02*

   Effect of an electric field on superfluid helium scintillation produced by alpha-particle sources

   T. M. Ito🇺🇸 · S. M. Clayton🇺🇸 · J. Ramsey🇺🇸 · M. Karcz🇺🇸 · C.-Y. Liu🇺🇸 · J. C. Long🇺🇸 · T. G. Reddy🇺🇸 · G. M. Seidel🇺🇸

   We report a study of the intensity and time dependence of scintillation produced by weak alpha particle sources in superfluid helium in the presence of an electric field (0 - 45 kV/cm) in the temperature range of 0.2 K to 1.1 K at the saturated vapor pressure. Both the prompt and the delayed components of the scintillation exhibit a reduction in intensity with the application of an electric field. The reduction in the intensity of the prompt component is well approximated by a linear dependence on the electric field strength with a reduction of 15% at 45 kV/cm. When analyzed using the Kramers theory of columnar recombination, this electric field dependence leads to the conclusion that roughly 40% of the scintillation results from species formed from atoms originally promoted to excited states and 60% from excimers created by ionization and subsequent recombination with the charges initially having a cylindrical Gaussian distribution about the alpha track of 60 nm radius. The intensity of the delayed component of the scintillation has a stronger dependence on the electric field strength and on temperature. The implications of these data on the mechanisms affecting scintillation in liquid helium are discussed.

   nucl-exphysics.atom-phphysics.ins-detPRA(2012)·34 citations
3. 03*

   Identified hadron compositions in p+p and Au+Au collisions at high transverse momenta at $\sqrt{s_{{}_{NN}}}=200$ GeV

   STAR Collaboration

   We report transverse momentum ($p_T\le 15$ GeV/$c$) spectra of ${\pi }^{\pm }$, $K^{\pm }$, $p$, $\bar{p}$, $K_S^0$, and ${\rho }^0$ at mid-rapidity in p+p and Au+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV. Perturbative QCD calculations are consistent with ${\pi }^{\pm }$ spectra in p+p collisions but do not reproduce $K$ and $p(\bar{p})$ spectra. The observed decreasing antiparticle-to-particle ratios with increasing $p_T$ provide experimental evidence for varying quark and gluon jet contributions to high-$p_T$ hadron yields. The relative hadron abundances in Au+Au at $p_T{}_{\sim }^{>}8$ GeV/$c$ are measured to be similar to the p+p results, despite the expected Casimir effect for parton energy loss.

   nucl-exPRL(2012)·129 citations
4. 04*

   Particle Production at Large Transverse Momentum with ALICE

   Harald Appelshäuser (for the ALICE Collaboration)🇩🇪

   We present transverse momentum distributions of inclusive charged particles and identified hadrons in $pp$ and Pb--Pb collisions at $\text{rs}=2.76$ TeV, measured by ALICE at the LHC. The Pb--Pb data are presented in intervals of collision centrality and cover transverse momenta up to 50 GeV/$c$. Nuclear medium effects are studied in terms of the nuclear modification factor \raa. The results indicate a strong suppression of high-$p_T$ particles in Pb--Pb collisions, consistent with a large energy loss of hard-scattered partons in the hot, dense and long-lived medium created at the LHC. We compare the preliminary results for inclusive charged particles to previous results from RHIC and calculations from energy loss models. Furthermore, we compare the nuclear modification factors of inclusive charged particles to those of identified ${\pi }^0$, ${\pi }^{\pm }$, K${}_s^0$, and $\Lambda$.

   nucl-exnucl-thJ.Phys.G(2011)·43 citations
5. 05*

   Higher Flow Harmonics in Heavy Ion Collisions from STAR

   Paul Sorensen (for the STAR Collaboration)🇺🇸

   We report STAR measurements relating to higher flow harmonics including the centrality dependence of two- and four-particle cumulants for harmonics 1 to 6. Two-particle correlation functions vs. \Delta\eta and \Delta\phi are presented for pT and number correlations. We find the power spectra (Fourier Transforms of the correlation functions) for central collisions drop quickly for higher harmonics. The \Delta\eta dependence of v3{2}2 and the pT and centrality dependence of v2 and v3 are studied. Trends are conistent with expectations from models including hot-spots in the initial energy density and an expansion phase. We also present v3 and v2{2}2 - v2{4}2 vs. \surdsNN .

   nucl-exJ.Phys.G(2011)·46 citations
6. 06*

   Theory of Antineutrino Monitoring of Burning MOX Plutonium Fuels

   A.C. Hayes🇺🇸 · H.R. Trellue🇺🇸 · Michael Martin Nieto🇺🇸 · W.B. WIlson🇺🇸

   This letter presents the physics and feasibility of reactor antineutrino monitoring to verify the burnup of plutonium loaded in the reactor as a Mixed Oxide (MOX) fuel. It examines the magnitude and temporal variation in the antineutrino signals expected for different MOX fuels, for the purposes of nuclear accountability and safeguards. The antineutrino signals from reactor-grade and weapons-grade MOX are shown to be distinct from those from burning low enriched uranium. Thus, antineutrino monitoring could be used to verify the destruction of plutonium in reactors, though verifying the grade of the plutonium being burned is found to be more challenging.

   ↳ nucl-thhep-exnucl-exPRC(2012)·8 citations
7. 07*

   Systematics of 2+ states in C isotopes from the ab initio no-core shell model

   Christian Forssén🇸🇪 · Robert Roth🇩🇪 · Petr Navrátil🇨🇦

   We study low-lying states of even carbon isotopes in the range A = 10 - 20 within the large- scale no-core shell model (NCSM). Using several accurate nucleon-nucleon (NN) as well as NN plus three-nucleon (NNN) interactions, we calculate excitation energies of the lowest 2+ state, the electromagnetic B(E2; 2+1 -> 0+1) transition rates, the 2+1 quadrupole moments as well as se- lected electromagnetic transitions among other states. Recent experimental campaigns to measure 2+-state lifetimes indicate an interesting evolution of nuclear structure that pose a challenge to reproduce theoretically from first principles. Our calculations do not include any effective charges or other fitting parameters. However, calculated results extrapolated to infinite model spaces are also presented. The model-dependence of those results is discussed. Overall, we find a good agree- ment with the experimentally observed trends, although our extrapolated B(E2; 2+1 -> 0+1) value for 16C is lower compared to the most recent measurements. Relative transition strengths from higher excited states are investigated and the influence of NNN forces is discussed. In particular for 16C we find a remarkable sensitivity of the transition rates from higher excited states to the details of the nuclear interactions.

   ↳ nucl-thnucl-exJ.Phys.G(2013)·46 citations
8. 08*

   On microscopic theory of the gamma-ray strength functions

   Sergei Kamerdzhiev🇷🇺 · Dmitrii Voitenkov🇷🇺

   Using the Theory of Finite Fermi Systems, we obtained a non-magic nuclei generalization of the old theoretical results by J. Speth for magic nuclei dealing with the transitions between excited states and moment values of excited state. Such an extension is quite necessary for microscopic calculations of the gamma ray strength function. The comparison with the standard QRPA has shown that the modern many-body approach gives some new physics. The calculated value of the quadrupole moment of the excited state in 208Pb is agreed satisfactorily with the experiment. Some possible improvements of the theory are briefly discussed.

   ↳ nucl-thnucl-exProc. of the XII Intern. Seminar "On Elec…·4 citations
9. 09*

   Neutrino nucleus reactions within the GiBUU model

   O. Lalakulich🇩🇪 · K. Gallmeister🇩🇪 · U. Mosel🇩🇪

   The GiBUU model, which implements all reaction channels relevant at medium neutrino energy, is used to investigate the neutrino and antineutrino scattering on iron. Results for integrated cross sections are compared with NOMAD and MINOS data. It is shown, that final state interaction can noticeably change the spectra of the outgoing hadrons. Predictions for the Miner$\nu$a experiment are made for pion spectra, averaged over NuMI neutrino and antineutrino fluxes.

   ↳ hep-phhep-exnucl-exnucl-thJ.Phys.Conf.Ser.(2013)·21 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.