Thu·Dec 1, 2016Thursday·December 1, 2016

1. 01*

   Long-range correlations in ALICE at the LHC

   Igor Altsybeev (for the ALICE collaboration)🇷🇺

   Long-range correlations between particles separated by a pseudorapidity gap are a powerful tool to explore the initial stages and evolution of the medium created in hadron-hadron collisions. An overview of the long-range correlations measured by the ALICE detector in pp, p-Pb and Pb-Pb will be presented. This includes analyses of forward-backward, two- and multi-particle correlations with the use of the central barrel and forward detectors.

   nucl-exhep-exJ.Phys.Conf.Ser.(2017)·5 citations
2. 02*

   Emergent phenomena and partonic structure in hadrons

   Craig D. Roberts🇺🇸 · Cedric Mezrag🇺🇸

   Modern facilities are poised to tackle fundamental questions within the Standard Model, aiming to reveal the nature of confinement, its relationship to dynamical chiral symmetry breaking (DCSB) - the origin of visible mass - and the connection between these two, key emergent phenomena. There is strong evidence to suggest that they are intimately connected with the appearance of momentum-dependent masses for gluons and quarks in QCD, which are large in the infrared: $m_g\sim 500$MeV and $M_q\sim 350$MeV. DCSB, expressed in the dynamical generation of a dressed-quark mass, has an enormous variety of verifiable consequences, including an enigmatic result that the properties of the (almost) massless pion are the cleanest expression of the mechanism which is responsible for almost all the visible mass in the Universe. This contribution explains that these emergent phenomena are expressed with particular force in the partonic structure of hadrons, e.g. in valence-quark parton distribution amplitudes and functions, and, consequently, in numerous hadronic observables, so that we are now in a position to exhibit the consequences of confinement and DCSB in a wide range of hadron observables, opening the way to empirical verification of their expression in the Standard Model.

   ↳ nucl-thhep-lathep-phnucl-exEPJ Web Conf.(2017)·7 citations
3. 03*

   Event patterns extracted from top quark-related spectra in proton-proton collisions at 8 TeV

   Ya-Hui Chen🇨🇳 · Fu-Hu Liu🇨🇳 · Roy A. Lacey🇺🇸

   We analyze the transverse momentum ($p_T$) and rapidity ($y$) spectra of top quark pairs, hadronic top quarks, and top quarks produced in proton-proton ($pp$) collisions at center-of-mass energy $\sqrt{s}=8$ TeV. For $p_T$ spectra, we use the superposition of the inverse power-law suggested by the QCD (quantum chromodynamics) calculus and the Erlang distribution resulting from a multisource thermal model. For $y$ spectra, we use the two-component Gaussian function resulting from the revised Landau hydrodynamic model. The modelling results are in agreement with the experimental data measured at the detector level, in the fiducial phase-space, and in the full phase-space by the ATLAS Collaboration at the Large Hadron Collider (LHC). Based on the parameter values extracted from $p_T$ and $y$ spectra, the event patterns in three-dimensional velocity (${\beta }_x$-${\beta }_y$-${\beta }_z$), momentum ($p_x$-$p_y$-$p_z$), and rapidity ($y_1$-$y_2$-$y$) spaces are obtained, and the probability distributions of these components are also obtained.

   ↳ hep-phhep-exnucl-exnucl-thCPC(2018)·2 citations
4. 04*

   Quasifission dynamics and stability of superheavy systems

   Kazuyuki Sekizawa🇯🇵 · Sophia Heinz🇩🇪

   Recent experiments revealed intriguing similarities in the ${}^{64}$Ni+${}^{207}$Pb, ${}^{132}$Xe+${}^{208}$Pb, and ${}^{238}$U+${}^{238}$U reactions at energies around the Coulomb barrier. The experimental data indicate that for all systems substantial energy dissipation takes place, in the first stage of the reaction, although the number of transferred nucleons is small. On the other hand, in the second stage, a large number of nucleons are transferred with small friction and small consumption of time. To understand the observed behavior, various reactions were analyzed based on the microscopic time-dependent Hartree-Fock (TDHF) theory. From a systematic analysis for ${}^{40,48}$Ca+${}^{124}$Sn, ${}^{40}$Ca+${}^{208}$Pb, ${}^{40}$Ar+${}^{208}$Pb, ${}^{58}$Ni+${}^{208}$Pb, ${}^{64}$Ni+${}^{238}$U, ${}^{136}$Xe+ ${}^{198}$Pt, and ${}^{238}$U+${}^{238}$U reactions, we find that TDHF reproduces well the measured trends. In addition, the Balian-Vénéroni variational principle is applied to head-on collisions of ${}^{238}$U+${}^{238}$U, and the variance of the fragment masses is compared with the experimental data, showing significant improvement. The underlying reaction mechanisms and possible future studies are discussed.

   ↳ nucl-thnucl-exActa Phys.Polon.Supp.(2017)·8 citations
5. 05*

   Novel Role of Superfluidity in Low-Energy Nuclear Reactions

   Piotr Magierski🇵🇱 · Kazuyuki Sekizawa🇯🇵 · Gabriel Wlazłowski🇵🇱

   We demonstrate, within symmetry unrestricted time-dependent density functional theory, the existence of new effects in low-energy nuclear reactions which originate from superfluidity. The dynamics of the pairing field induces solitonic excitations in the colliding nuclear systems, leading to qualitative changes in the reaction dynamics. The solitonic excitation prevents collective energy dissipation and effectively suppresses fusion cross section. We demonstrate how the variations of the total kinetic energy of the fragments can be traced back to the energy stored in the superfluid junction of colliding nuclei. Both contact time and scattering angle in non-central collisions are significantly affected. The modification of the fusion cross section and possibilities for its experimental detection are discussed.

   ↳ nucl-thnucl-exPRL(2017)·79 citations
6. 06*

   J/psi+Z production at the LHC

   Jean-Philippe Lansberg🇫🇷 · Hua-Sheng Shao🇨🇭

   We briefly review recent results which we have obtained in the study of J/psi+Z production at the LHC. Considering our NLO computation in the Colour Evaporation Model (CEM) as an upper theory limit for the single-parton-scattering contributions, we claim that the existing data set from ATLAS points at a dominant double-parton-scattering contribution with an effective cross section smaller than that for jet-related observables. As a side product of our analysis, we have computed, for the first time, the one-loop QCD corrections to the J/psi P_T-differential cross section in the CEM.

   ↳ hep-phhep-exnucl-exnucl-thEPJ Web Conf.(2017)·1 citation
7. 07*

   Classifiers for centrality determination in proton-nucleus and nucleus-nucleus collisions

   Igor Altsybeev🇷🇺 · Vladimir Kovalenko🇷🇺

   Centrality, as a geometrical property of the collision, is crucial for the physical interpretation of nucleus-nucleus and proton-nucleus experimental data. However, it cannot be directly accessed in event-by-event data analysis. Common methods for centrality estimation in A-A and p-A collisions usually rely on a single detector (either on the signal in zero-degree calorimeters or on the multiplicity in some semi-central rapidity range). In the present work, we made an attempt to develop an approach for centrality determination that is based on machine-learning techniques and utilizes information from several detector subsystems simultaneously. Different event classifiers are suggested and evaluated for their selectivity power in terms of the number of nucleons-participants and the impact parameter of the collision. Finer centrality resolution may allow to reduce impact from so-called volume fluctuations on physical observables being studied in heavy-ion experiments like ALICE at the LHC and fixed target experiment NA61/SHINE on SPS.

   ↳ physics.data-annucl-exstat.MLEPJ Web Conf.(2017)·7 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.