Fri·Oct 17, 2014Friday·October 17, 2014

1. 01*

   Measurement of inclusive jet spectra in pp, p-Pb, and Pb-Pb collisions with the ALICE detector

   Rüdiger Haake (for the ALICE Collaboration)🇩🇪

   Highly energetic jets are sensitive probes for the kinematic properties and the topology of high energy hadron collisions. Jets are collimated sprays of charged and neutral particles, which are produced in fragmentation of hard scattered partons from an early stage of the collision. In ALICE, jets have been measured in pp, p-Pb, and Pb-Pb collisions at several collision energies. While analyses of Pb-Pb events unveil properties of the hot and dense medium formed in heavy-ion collisions, pp and p-Pb collisions can shed light on hadronization and cold nuclear matter effects in jet production. Additionally, pp and p-Pb serve as a baseline for disentangling hot and cold nuclear matter effects. A possible modification of the initial state is tested in p-Pb analyses. For the extraction of a jet signal, the exact evaluation of the background from the underlying event is an especially important ingredient. Due to the different nature of underlying events, each collision system requires a different analysis technique for removing the effect of the background on the jet sample. The focus of this publication is on the ALICE measurements of nuclear modification factors connecting p-Pb and Pb-Pb events to pp collisions. Furthermore, the radial jet structure is explored by comparing jet spectra reconstructed with different resolution parameters.

   nucl-exJ.Phys.Conf.Ser.(2017)·0 citations
2. 02*

   Proton and Neutron Momentum Distributions in A = 3 Asymmetric Nuclei

   O. Hen🇮🇱 · L.B. Weinstein🇺🇸 · S. Gilad🇺🇸 · W. Boeglin🇺🇸

   A proposal approved by the Jefferson Lab (JLab) PAC to study the proton-to-neutron momentum distribution ratio in A=3 nuclei via (e,e'p) scattering off 3He and 3H mirror nuclei. The experiment will measure the 3H(e,e'p) and 3He(e,e'p) cross-sections and cross-section ratios at Q2 = 2 and xB>1 kinematics, over a missing momentum range of 0 - 450 MeV/c. The experiment was approved in 2014 at part of the JLab Hall-A Tritium run period for a total run time of 12 days.

   nucl-exnucl-th5 citations
3. 03*

   Beamline Instrumentation for Future Parity-Violation Experiments

   Robert Michaels🇺🇸

   The parity-violating electron scattering community has made tremendous progress over the last twenty five years in their ability to measure tiny asymmetries of order 100 parts per billion (ppb) with beam-related corrections and systematic errors of a few ppb. Future experiments are planned for about an order of magnitude smaller asymmetries and with higher rates in the detectors. These new experiments pose new challenges for the beam instrumentation and for the strategy for setting up the beam. In this contribution to PAVI14 I discuss several of these challenges and demands, with a focus on developments at Jefferson Lab.

   nucl-exphysics.acc-phphysics.ins-det1 citation
4. 04*

   Jet quenching beyond the energy loss approach

   Grigory Ovanesyan🇺🇸

   We study the jet quenching effect in heavy ion collisions, based on medium-induced splitting functions calculated from Soft Collinear Effective Theory with Glauber Gluons. Our method is formulated in the language of DGLAP evolution equations with medium-induced splitting functions. In the small-$x$ soft gluon approximation we analytically solve the evolution equations and find an intuitive connection to the energy loss approach. For central Pb+Pb collisions at the LHC we quantify the effect of finite-$x$ corrections for the nuclear modification factor and compare to data.

   ↳ hep-phnucl-exnucl-thInt.J.Mod.Phys.Conf.Ser.(2015)·2 citations
5. 05*

   Dilepton Production in Transport-based Approaches

   Janus Weil🇩🇪 · Stephan Endres🇩🇪 · Hendrik van Hees🇩🇪 · Marcus Bleicher🇩🇪 · Ulrich Mosel🇩🇪

   We investigate dilepton production in transport-based approaches and show that the baryon couplings of the $\rho$ meson represent the most important ingredient for understanding the measured dilepton spectra. At low energies (of a few GeV), the baryon resonances naturally play a larger role and affect already the vacuum spectra via Dalitz-like contributions, which can be captured well in an on-shell-transport scheme. At higher energies, the baryons mostly affect the in-medium self energy of the $\rho$, which is harder to tackle in transport models and requires advanced techniques.

   ↳ nucl-thhep-phnucl-ex5 citations
6. 06*

   Simulation of background reduction and Compton depression in low-background HPGe spectrometer at a surface laboratory

   ShunLi Niu · Xiao Cai · ZhenZhong Wu · YuGuang Xie · BoXiang Yu · ZhiGang Wang · Jian Fang · XiLei Sun · LiJun Sun · YingBiao Liu · Long Gao · Xuan Zhang and 4 other authors

   High-purity germanium detectors are well suited to analysis the radioactivity of samples. In order to reduce the environmental background, low-activity lead and oxygen free copper are installed outside of the probe to shield gammas, outmost is a plastic scintillator to veto the cosmic rays, and an anti-Compton detector can improve the Peak-to-Compton ratio. Using the GEANT4 tools and taking into account a detailed description of the detector, we optimize the sizes of the detectors to reach the design indexes. A group of experimental data from a HPGe spectrometer in using were used to compare with the simulation. As to new HPGe Detector simulation, considering the different thickness of BGO crystals and anti-coincidence efficiency, the simulation results show that the optimal thickness is 5.5cm, and the Peak-to-Compton ratio of 40K is raised to 1000 when the anti-coincidence efficiency is 0.85. As the background simulation, 15 cm oxygen-free copper plus 10 cm lead can reduce the environmental gamma rays to 0.0024 cps/100 cm3 Ge (50keV~2.8MeV), which is about 10-5 of environmental background.

   ↳ physics.ins-dethep-exnucl-exCPC(2015)·6 citations
7. 07*

   Recent development of complex scaling method for many-body resonances and continua in light nuclei

   Takayuki Myo🇯🇵 · Yuma Kikuchi🇯🇵 · Hiroshi Masui🇺🇸 · Kiyoshi Kato🇯🇵

   The complex scaling method (CSM) is a useful similarity transformation of the Schrödinger equation, in which bound-state spectra are not changed but continuum spectra are separated into resonant and non-resonant continuum ones. Because the asymptotic wave functions of the separated resonant states are regularized by the CSM, many-body resonances can be obtained by solving an eigenvalue problem with the $L^2$ basis functions. Applying this method to a system consisting of a core and valence nucleons, we investigate many-body resonant states in weakly bound nuclei very far from the stability lines. Non-resonant continuum states are also obtained with the discretized eigenvalues on the rotated branch cuts. Using these complex eigenvalues and eigenstates in CSM, we construct the extended completeness relations and Green's functions to calculate strength functions and breakup cross sections. Various kinds of theoretical calculations and comparisons with experimental data are presented.

   ↳ nucl-thnucl-exPPNP(2014)·172 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.