Fri·Aug 26, 2011Friday·August 26, 2011

1. 01*

   New Results on the ${\pi }^{+}{\pi }^{-}$ Electroproduction Cross Sections off Protons

   G.V. Fedotov🇺🇸 · R.W. Gothe🇺🇸

   In these proceedings we present preliminary ${\pi }^{+}{\pi }^{-}$ electroproduction cross sections off protons in the kinematical area of 1.4 GeV $<W<$ 1.8 GeV and 0.4 GeV${}^2$ $<Q^2<1.1$ GeV${}^2$. Our results extend the kinematical coverage for this exclusive channel with respect to previous measurements. Furthermore, the ${\pi }^{+}{\pi }^{-}$ electroproduction cross sections were obtained for $Q^2$-bins of much smaller size. The future analysis of this data within the framework of the JLAB-MSU reaction model (JM) will considerably improve our knowledge on the $Q^2$ evolution of the transition ${\gamma }_{v}N{N}^{\ast }$ electrocouplings, in particular for the resonances with masses above 1.6 GeV.

   nucl-exhep-phAIP Conf.Proc.(2012)·1 citation
2. 02*

   Absence of a self-induced decay effect in 198Au

   Richard M. Lindstrom🇺🇸 · Ephraim Fischbach🇺🇸 · John B. Buncher🇺🇸 · Jere H. Jenkins🇺🇸 · Andrew Yue🇺🇸

   We report the results of an improved experiment aimed at determining whether the half-life ($T_{1/2}$) of ${}^{198}$Au depends on the shape of the source. In this experiment, the half-lives of a gold sphere and a thin gold wire were measured after each had been irradiated in the NIST Center for Neutron Research. In comparison to an earlier version of this experiment, both the specific activities of the samples and their relative surface/volume ratios have been increased, leading to an improved test for the hypothesized self-induced decay (SID) effect. We find T_1/2(sphere)/T_1/2(wire) = 0.9993+/-0.0002, which is compatible with no SID effect.

   nucl-exNucl.Instrum.Meth.A(2011)·7 citations
3. 03*

   Azimuthal asymmetries in single polarized proton-proton Drell-Yan processes

   Zhun Lu🇨🇳 · Bo-Qiang Ma🇨🇳 · Jiacai Zhu🇨🇳

   We study the azimuthal asymmetries in proton-proton Drell-Yan processes with one incident proton being transversely or longitudinally polarized. We consider particularly the asymmetries contributed by the leading-twist chiral-odd quark distributions. We analyze the asymmetries with $\sin (2\varphi +{\varphi }_S)$ and $\sin (2\varphi -{\varphi }_S)$ modulations in transverse single polarized $p^{\uparrow }p$ Drell-Yan and $\sin 2\varphi$ asymmetries in longitudinal single polarized $p^{\to }p$ Drell-Yan at RHIC, J-PARC, E906 (Fermi Lab) and NICA (JINR). We show that the measurements of the asymmetries in those facilities can provide valuable information of the chiral-odd structure of the nucleon both in the valence and sea regions.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2011)·10 citations
4. 04*

   QCD Structure of Nuclear Interactions

   Carlos G. Granados🇺🇸

   This dissertation investigated selected processes involving baryons and nuclei in hard scattering reactions. Through these processes, this work explored the constituent structure of baryons and the mechanisms through which the interactions between these constituents ultimately control the selected reactions. First, hard nucleon-nucleon elastic scattering was studied considering the quark exchange (QE) between the nucleons to be the dominant mechanism of interaction in the constituent picture. It was found that an angular asymmetry exhibited by proton-neutron (pn) elastic scattering data is explained within this framework if a quark-diquark picture dominates the nucleon's structure instead of a more traditional SU(6) model. The latter yields an asymmetry around 90 deg center of mass scattering with a sign opposite to what is experimentally observed. The second process is the hard breakup by a photon of a nucleon-nucleon system in light nuclei. Proton-proton (pp) and pn breakup in 3He, and double Delta-isobars production in deuteron breakup were analyzed in the hard rescattering model (HRM), which in conjunction with the QE mechanism provides a QCD description of the reaction. Cross sections for both channels in 3He photodisintegration were computed without the need of a fitting parameter. The results presented here for pp breakup show excellent agreement with recent experimental data. In double Delta-isobars production in deuteron breakup, HRM angular distributions for the two double Delta channels were compared to the pn channel and to each other. An important prediction from this study is that the Delta++ Delta- channel consistently dominates Delta+Delta0, which is in contrast with models that unlike the HRM consider a double Delta system in the initial state of the interaction. For such models both channels should have the same strength.

   ↳ nucl-thhep-exhep-phnucl-ex(2011) FIU Electronic Theses and Disserta…·0 citations
5. 05*

   Quarkonia Measurements by the CMS Experiment in pp and PbPb Collisions

   Catherine Silvestre (for the CMS collaboration)🇫🇷

   Quarkonia have been studied in different collision system and energy in order to understand the effects of the hot and dense medium created in heavy-ion collisions. CMS is well suited to measure quarkonia decays to muons given the muon identification and charged particle tracking capability. We report here prompt, non-prompt J/\psi, and \Upsilon\ production measured by the CMS experiment in pp collisions at \sqrt{s}=7 TeV. In addition, the J/\psi\ and \Upsilon\ production in PbPb at \sqrt{s_{NN}}=2.76 TeV and pp collisions at the same per nucleon energy are measured and compared. Prompt and non-prompt J/\psi\ contributions are separated for the first time in heavy-ion collisions, as is the ground from the excited states in the \Upsilon\ family. Suppression in PbPb at \sqrt{s_{NN}}=2.76 TeV is quantified for prompt J/\psi, B->J/\psi, and \Upsilon(1S), as well as the relative suppression of \Upsilon(2S+3S) compared to \Upsilon(1S).

   ↳ hep-exnucl-exJ.Phys.G(2011)·22 citations
6. 06*

   A Laser System for the Spectroscopy of Highly-Charged Bismuth Ions

   S. Albrecht🇩🇪 · S. Altenburg🇩🇪 · C. Siegel🇩🇪 · N. Herschbach🇩🇪 · G. Birkl🇩🇪

   We present and characterize a laser system for the spectroscopy on highly-charged ^209Bi^82+ ions at a wavelength of 243.87 nm. For absolute frequency stabilization, the laser system is locked to a near-infra-red laser stabilized to a rubidium transition line using a transfer cavity based locking scheme. Tuning of the output frequency with high precision is achieved via a tunable rf offset lock. A sample-and-hold technique gives an extended tuning range of several THz in the UV. This scheme is universally applicable to the stabilization of laser systems at wavelengths not directly accessible to atomic or molecular resonances. We determine the frequency accuracy of the laser system using Doppler-free absorption spectroscopy of Te_2 vapour at 488 nm. Scaled to the target wavelength of 244 nm, we achieve a frequency uncertainty of \sigma_{244nm} = 6.14 MHz (one standard deviation) over six days of operation.

   ↳ physics.atom-phnucl-exAppl.Phys.B(2012)·3 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.