Thu·Sep 11, 2014Thursday·September 11, 2014

1. 01*

   Comment on "Measurement of 2- and 3-nucleon short range correlation probabilities in nuclei"

   Douglas W. Higinbotham🇺🇸 · Or Hen🇮🇱

   "Measurement of 2- and 3-nucleon short range correlation probabilities in nuclei" claimed to observe plateaus in the inclusive A/3He (e,e') ratios in the xB > 2 region; yet, a subsequent measurement at a higher momentum transfer did not observe xB > 2 plateaus. Herein we comment on a possible experimental explanation for this discrepancy.

   nucl-exPRL(2015)·20 citations
2. 02*

   Ionization and scintillation of nuclear recoils in gaseous xenon

   J. Renner🇺🇸 · V. M. Gehman🇺🇸 · A. Goldschmidt🇺🇸 · H. S. Matis🇺🇸 · T. Miller🇺🇸 · Y. Nakajima🇺🇸 · D. Nygren🇺🇸 · C. A. B. Oliveira🇺🇸 · D. Shuman🇺🇸 · V. Álvarez🇪🇸 · F. I. G. Borges🇵🇹 · S. Cárcel🇪🇸 and 66 other authors

   Ionization and scintillation produced by nuclear recoils in gaseous xenon at approximately 14 bar have been simultaneously observed in an electroluminescent time projection chamber. Neutrons from radioisotope $\alpha$-Be neutron sources were used to induce xenon nuclear recoils, and the observed recoil spectra were compared to a detailed Monte Carlo employing estimated ionization and scintillation yields for nuclear recoils. The ability to discriminate between electronic and nuclear recoils using the ratio of ionization to primary scintillation is demonstrated. These results encourage further investigation on the use of xenon in the gas phase as a detector medium in dark matter direct detection experiments.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2015)·24 citations
3. 03*

   The impact of energy conservation in transport models on the ${\pi }^{-}/{\pi }^{+}$ multiplicity ratio in heavy-ion collisions and the symmetry energy

   M.D. Cozma🇷🇴

   The charged pion multiplicity ratio in intermediate energy central heavy-ion collisions has been proposed as a suitable observable to constrain the high density dependence of the isovector part of the equation of state, with contradicting results. Using an upgraded version of the Tübingen QMD transport model, which allows the conservation of energy at a local or global level by accounting for the potential energy of hadrons in two-body collisions and leading thus to particle production threshold shifts, we demonstrate that compatible constraints for the symmetry energy stiffness can be extracted from pion multiplicity and elliptic flow observables. Nevertheless, pion multiplicities are proven to be highly sensitive to the yet unknown isovector part of the in-medium $\Delta$(1232) potential which hinders presently the extraction of meaningful information on the high density dependence of the symmetry energy. A solution to this problem together with the inclusion of contributions presently neglected, such as in-medium pion potentials and retardation effects, are needed for a final verdict on this topic.

   ↳ nucl-thnucl-exPLB(2016)·88 citations
4. 04*

   Simulations and measurements of beam loss patterns at the CERN Large Hadron Collider

   R. Bruce🇨🇭 · R.W. Assmann🇩🇪 · V. Boccone🇨🇭 · C. Bracco🇨🇭 · M. Brugger🇨🇭 · M. Cauchi🇨🇭 · F. Cerutti🇨🇭 · D. Deboy🇨🇭 · A. Ferrari🇨🇭 · L. Lari🇨🇭 · A. Marsili🇨🇭 · A. Mereghetti🇨🇭 and 12 other authors

   The CERN Large Hadron Collider (LHC) is designed to collide proton beams of unprecedented energy, in order to extend the frontiers of high-energy particle physics. During the first very successful running period in 2010--2013, the LHC was routinely storing protons at 3.5--4 TeV with a total beam energy of up to 146 MJ, and even higher stored energies are foreseen in the future. This puts extraordinary demands on the control of beam losses. An un-controlled loss of even a tiny fraction of the beam could cause a superconducting magnet to undergo a transition into a normal-conducting state, or in the worst case cause material damage. Hence a multi-stage collimation system has been installed in order to safely intercept high-amplitude beam protons before they are lost elsewhere. To guarantee adequate protection from the collimators, a detailed theoretical understanding is needed. This article presents results of numerical simulations of the distribution of beam losses around the LHC that have leaked out of the collimation system. The studies include tracking of protons through the fields of more than 5000 magnets in the 27 km LHC ring over hundreds of revolutions, and Monte-Carlo simulations of particle-matter interactions both in collimators and machine elements being hit by escaping particles. The simulation results agree typically within a factor 2 with measurements of beam loss distributions from the previous LHC run. Considering the complex simulation, which must account for a very large number of unknown imperfections, and in view of the total losses around the ring spanning over 7 orders of magnitude, we consider this an excellent agreement. Our results give confidence in the simulation tools, which are used also for the design of future accelerators.

   ↳ physics.acc-phnucl-exPhys.Rev.ST Accel.Beams(2014)·151 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.