Tue·Dec 8, 2015Tuesday·December 8, 2015

1. 01*

   An analysis of the impact of LHC Run I proton-lead data on nuclear parton densities

   Néstor Armesto🇪🇸 · Hannu Paukkunen🇫🇮 · José Manuel Penín🇪🇸 · Carlos A. Salgado🇪🇸 · Pía Zurita🇪🇸

   We report on an analysis of the impact of available experimental data on hard processes in proton-lead collisions during Run I at the Large Hadron Collider on nuclear modifications of parton distribution functions. Our analysis is restricted to the EPS09 and DSSZ global fits. The measurements that we consider comprise production of massive gauge bosons, jets, charged hadrons and pions. This is the first time a study of nuclear PDFs includes this number of different observables. The goal of the paper is twofold: i) checking the description of the data by nPDFs, as well as the relevance of these nuclear effects, in a quantitative manner; ii) testing the constraining power of these data in eventual global fits, for which we use the Bayesian reweighting technique. We find an overall good, even too good, description of the data, indicating that more constraining power would require a better control over the systematic uncertainties and/or the proper proton-proton reference from LHC Run II. Some of the observables, however, show sizable tension with specific choices of proton and nuclear PDFs. We also comment on the corresponding improvements on the theoretical treatment.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2016)·48 citations
2. 02*

   On Quasibound N* Nuclei

   N. G. Kelkar🇨🇴 · D. Bedoya Fierro🇨🇴 · P. Moskal🇵🇱

   The possibility for the existence of unstable bound states of the S11 nucleon resonance N${}^{\ast }$(1535) and nuclei is investigated. These quasibound states are speculated to be closely related to the existence of the quasibound states of the eta mesons and nuclei. Within a simple model for the N N${}^{\ast }$ interaction involving a pion and eta meson exchange, N${}^{\ast }$-nucleus potentials for N*-${}^3$He and N*-${}^{24}$Mg are evaluated and found to be of a Woods-Saxon like form which supports two to three bound states. In case of N*-${}^3$He, one state bound by only a few keV and another by 4 MeV is found. The results are however quite sensitive to the N N${}^{\ast }$ $\pi$ and N N${}^{\ast }$ $\eta$ vertex parameters. A rough estimate of the width of these states, based on the mean free path of the exchanged mesons in the nuclei leads to very broad states with $\Gamma \sim$ 80 and 110 MeV for N*-${}^3$He and N*-${}^{24}$Mg respectively.

   ↳ nucl-thnucl-exActa Phys.Polon.B(2016)·12 citations
3. 03*

   Moving forward to constrain the shear viscosity of QCD matter

   Gabriel Denicol🇺🇸 · Akihiko Monnai🇺🇸 · Bjoern Schenke🇺🇸

   We demonstrate that measurements of rapidity differential anisotropic flow in heavy ion collisions can constrain the temperature dependence of the shear viscosity to entropy density ratio {\eta}/s of QCD matter. Comparing results from hydrodynamic calculations with experimental data from RHIC, we find evidence for a small {\eta}/s $\approx$ 0.04 in the QCD cross-over region and a strong temperature dependence in the hadronic phase. A temperature independent {\eta}/s is disfavored by the data. We further show that measurements of the event-by-event flow as a function of rapidity can be used to independently constrain the initial state fluctuations in three dimensions and the temperature dependent transport properties of QCD matter.

   ↳ nucl-thhep-phnucl-exPRL(2016)·101 citations
4. 04*

   Progress in Neutron EM Couplings

   Igor Strakovsky (GW)🇺🇸 · William Briscoe (GW)🇺🇸 · Alexander Kudryavtsev (ITEP/GW)🇷🇺 · Viacheslav Kulikov (ITEP)🇷🇺 · Maxim Martemianov (ITEP)🇷🇺 · Vladimir Tarasov (ITEP)🇷🇺 · Ron Workman (ITEP)🇺🇸

   An overview of the GW SAID and ITEP groups' effort to analyze pion photoproduction on the neutron-target will be given. The disentanglement of the isoscalar and isovector EM couplings of N* and Delta* resonances does require compatible data on both proton and neutron targets. The final-state interaction plays a critical role in the state-of-the-art analysis in extraction of the gn-->piN data from the deuteron target experiments. Then resonance couplings determined by the SAID PWA technique are then compared to previous findings. The neutron program is important component of the current JLab, MAMI-C, SPring-8, ELSA, and ELPH studies.

   ↳ nucl-thhep-exhep-phnucl-ex1 citation
5. 05*

   The Dortmund Low Background Facility - Low-Background Gamma Ray Spectrometry with an Artificial Overburden

   Holger Gastrich🇩🇪 · Claus Gößling🇩🇪 · Reiner Klingenberg🇩🇪 · Kevin Kröninger🇩🇪 · Till Neddermann🇩🇪 · Christian Nitsch🇩🇪 · Thomas Quante🇩🇪 · Kai Zuber🇩🇪

   High-purity germanium (HPGe) detectors used for low-background gamma ray spectrometry are usually operated under either a fairly low overburden of the order of one meter of water equivalent (mw.e.) or a high overburden of the order of 100mw.e. or more, e.g. in specialized underground laboratories. The Dortmund Low Background Facility (DLB) combines the advantages of both approaches. The artificial overburden of 10mw.e. already shields the hadronic component of cosmic rays. The inner shielding, featuring a state-of-the-art neutron shielding and an active muon veto, enables low-background gamma ray spectrometry at an easy-accessible location at the campus of the Technische Universität Dortmund. The integral background count rate between 40keV and 2700keV is 2.528+-0.004counts/kg/minute. This enables activity measurements of primordial radionuclides in the range of some 10mBq/kg within a week of measurement time.

   ↳ physics.ins-detnucl-exAppl.Radiat.Isot.(2016)·12 citations
6. 06*

   A simple model for rapidity fluctuations in the initial state of ultra-relativistic heavy-ion collisions

   Wojciech Broniowski🇵🇱 · Piotr Bozek🇵🇱

   Two-particle pseudorapidity correlations are analyzed in a simple model, where in the initial stage of the reaction multiple sources, extended in rapidity, are created. We show how the fluctuations of the length of the sources in rapidity generate correlations in the initial entropy deposition, which later contribute to the observed longitudinal correlations in hadron production. Our analysis, which is analytic and leads to straightforward formulas, allows us to understand the structure of the correlations, in particular to identify the component related to the fluctuation of the numbers of sources and the component from the length fluctuations. We also present the results in terms of the expansion in the basis of the Legendre polynomials. A number of further effects is discussed, such as smearing of the pseudorapidity distributions or resonance decays. Our results reproduce qualitatively and semiquantitatively the basic features of the recent measurements at the LHC.

   ↳ nucl-thnucl-exPRC(2016)·23 citations
7. 07*

   Observation of the Efimov state of the helium trimer

   Maksim Kunitski · Stefan Zeller🇺🇸 · Jörg Voigtsberger · Anton Kalinin · Lothar Ph. H. Schmidt · Markus Schöffler · Achim Czasch · Wieland Schöllkopf · Robert E. Grisenti🇩🇪 · Till Jahnke · Dörte Blume · Reinhard Dörner

   Quantum theory dictates that upon weakening the two-body interaction in a three-body system, an infinite number of three-body bound states of a huge spatial extent emerge just before these three-body states become unbound. Three helium atoms have been predicted to form a molecular system that manifests this peculiarity under natural conditions without artificial tuning of the attraction between particles by an external field. Here we report experimental observation of this long predicted but experimentally elusive Efimov state of ${}^4$He${}_3$ by means of Coulomb explosion imaging. We show spatial images of an Efimov state, confirming the predicted size and a typical structure where two atoms are close to each other while the third is far away.

   ↳ physics.atm-cluscond-mat.quant-gasnucl-exnucl-th+1Science(2015)·110 citations
8. 08*

   Power spectrum of flow fluctuations in relativistic heavy-ion collisions

   P. S. Saumia🇮🇳 · Ajit M. Srivastava🇮🇳

   We carry out hydrodynamical simulation of the evolution of fluid in relativistic heavy-ion collisions with random initial fluctuations. The time evolution of power spectrum of momentum anisotropies shows very strong correspondence with the physics of cosmic microwave anisotropies as was earlier predicted by some of us. In particular our results demonstrate suppression of superhorizon fluctuations and the correspondence between the location of the first peak in the power spectrum of momentum anisotropies and the length scale of fluctuations and expected freezeout time scale (more precisely, the sound horizon size at freezeout).

   ↳ nucl-thastro-ph.COhep-phnucl-exMod.Phys.Lett.A(2016)·6 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.