Wed·Jul 8, 2009Wednesday·July 8, 2009

1. 01*

   Measurement of the neutron electric dipole moment by crystal diffraction

   V.V. Fedorov🇷🇺 · M. Jentschel🇫🇷 · I.A. Kuznetsov🇷🇺 · E.G. Lapin🇷🇺 · E. Lelievre-Berna🇫🇷 · V. Nesvizhevsky🇫🇷 · A. Petoukhov🇫🇷 · S.Yu. Semenikhin🇷🇺 · T. Soldner🇫🇷 · F. Tasset🇫🇷 · V.V. Voronin🇷🇺 · Yu.P. Braginetz🇷🇺

   An experiment using a prototype setup to search for the neutron electric dipole moment by measuring spin-rotation in a non-centrosymmetric crystal (quartz) was carried out to investigate statistical sensitivity and systematic effects of the method. It has been demonstrated that the concept of the method works. The preliminary result of the experiment is $d_{\mathrm{n}}=(2.5\pm 6.5)\cdot 10^{-24}$ e$\cdot$cm. The experiment showed that an accuracy of $\sim 2.5\cdot 10^{-26}$ e$\cdot$cm can be obtained in 100 days data taking, using available quartz crystals and neutron beams.

   nucl-exhep-exphysics.ins-detNucl.Instrum.Meth.A(2009)·21 citations
2. 02*

   Isotopic Dependence of the Caloric Curve

   The ALADIN2000 Collaboration: W. Trautmann🇩🇪 · P. Adrich🇩🇪 · T. Aumann🇩🇪 · C.O. Bacri🇫🇷 · T. Barczyk🇵🇱 · R. Bassini🇮🇹 · S. Bianchin🇩🇪 · C. Boiano🇮🇹 · A.S. Botvina🇷🇺 · A. Boudard🇫🇷 · J. Brzychczyk🇵🇱 · A. Chbihi🇫🇷 and 44 other authors

   Isotopic effects in projectile fragmentation at relativistic energies have been studied with the ALADIN forward spectrometer at SIS. Stable and radioactive Sn and La beams with an incident energy of 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. Chemical freeze-out temperatures are found to be nearly invariant with respect to the A/Z ratio of the produced spectator sources, consistent with predictions for expanded systems. Consequences for the proposed interpretation of chemical breakup temperatures as representing the limiting temperatures predicted by microscopic models are discussed.

   nucl-exPPNP(2009)·2 citations
3. 03*

   Two-Photon Interactions with Nuclear Breakup in Relativistic Heavy Ion Collisions

   Anthony J. Baltz🇺🇸 · Yuri Gorbunov🇺🇸 · Spencer R. Klein🇺🇸 · Joakim Nystrand🇳🇴

   Highly charged relativistic heavy ions have high cross-sections for two-photon interactions. The photon flux is high enough that two-photon interactions may be accompanied by additional photonuclear interactions. Except for the shared impact parameter, these interactions are independent. Additional interactions like mutual Coulomb excitation are of experimental interest, since the neutrons from the nuclear dissociation provide a simple, relatively unbiased trigger. We calculate the cross sections, rapidity, mass and transverse momentum ($p_T)$ distributions for exclusive $\gamma \gamma$ production of mesons and lepton pairs, and for $\gamma \gamma$ reactions accompanied by mutual Coulomb dissociation. The cross-sections for $\gamma \gamma$ interactions accompanied by multiple neutron emission ($XnXn$) and single neutron emission ($1n1n$) are about 1/10 and 1/100 of that for the unaccompanied $\gamma \gamma$ interactions. We discuss the accuracy with which these cross-sections may be calculated. The typical $p_T$ of $\gamma \gamma$ final states is several times smaller than for comparable coherent photonuclear interactions, so $p_T$ may be an effective tool for separating the two classes of interactions.

   nucl-exPRC(2009)·108 citations
4. 04*

   Q-PYTHIA: a medium-modified implementation of final state radiation

   N. Armesto🇪🇸 · L. Cunqueiro🇮🇹 · C. A. Salgado🇪🇸

   We present a Monte Carlo implementation, within PYTHIA, of medium-induced gluon radiation in the final state branching process. Medium effects are introduced through an additive term in the splitting functions computed in the multiple-soft scattering approximation. The observable effects of this modification are studied for different quantities as fragmentation functions and the hump-backed plateau, and transverse momentum and angular distributions. The anticipated increase of intra-jet multiplicities, energy loss of the leading particle and jet broadening are observed as well as modifications of naive expectations based solely on analytical calculations. This shows the adequacy of a Monte Carlo simulator for jet analyses. Effects of hadronization are found to wash out medium effects in the soft region, while the main features remain. To show the performance of the implementation and the feasibility of our approach in realistic experimental situations we provide some examples: fragmentation functions, nuclear suppression factors, jet shapes and jet multiplicities. The package containing the modified routines is available for public use. This code, which is not an official PYTHIA release, is called Q-PYTHIA. We also include a short manual to perform the simulations of jet quenching.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2009)·207 citations
5. 05*

   A relativistic quark model for the Omega- electromagnetic form factors

   G. Ramalho🇺🇸 · K. Tsushima🇺🇸 · Franz Gross🇺🇸

   We compute the Omega- electromagnetic form factors and the decuplet baryon magnetic moments using a quark model application of the Covariant Spectator Theory. Our predictions for the Omega- electromagnetic form factors can be tested in the future by lattice QCD simulations at the physical strange quark mass.

   ↳ hep-phhep-latnucl-exnucl-thPRD(2009)·80 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.