Tue·Oct 21, 2014Tuesday·October 21, 2014

1. 01*

   Study of Z production in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV in the dimuon and dielectron decay channels

   CMS Collaboration

   The production of Z bosons is studied in the dimuon and dielectron decay channels in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV, using data collected by the CMS experiment at the LHC. The PbPb data sample corresponds to an integrated luminosity of about 150 inverse microbarns, while the pp data sample collected in 2013 at the same nucleon-nucleon centre-of-mass energy has an integrated luminosity of 5.4 inverse picobarns. The Z boson yield is measured as a function of rapidity, transverse momentum, and collision centrality. The ratio of PbPb to pp yields, scaled by the number of inelastic nucleon-nucleon collisions, is found to be 1.06 +/- 0.05 (stat) +/- 0.08 (syst) in the dimuon channel and 1.02 +/- 0.08 (stat) +/- 0.15 (syst) in the dielectron channel, for centrality-integrated Z boson production. This binary collision scaling is seen to hold in the entire kinematic region studied, as expected for a colourless probe that is unaffected by the hot and dense QCD medium produced in heavy ion collisions.

   nucl-exhep-exJHEP(2015)·118 citations
2. 02*

   Clustering features of the ${}^7$Be nucleus in relativistic fragmentation

   N. K. Kornegrutsa · D. A. Artemenkov🇷🇺 · P. I. Zarubin🇷🇺 · R. R. Kattabekov🇷🇺 · K. Z. Mamatkulov🇷🇺

   Charge topology of fragmentation of 1.2 A GeV ${}^7$Be nuclei in nuclear track emulsion is presented.The dissociation channels ${}^4$He + ${}^3$He, 2${}^3$He+ n, ${}^4$He + 2${}^1$H are considered in detail. It is established that the events ${}^6$Be + n amount about to 27 % in the channel ${}^4$He + 2${}^1$H.

   nucl-exFew Body Syst.(2014)·6 citations
3. 03*

   ${}^8$He nuclei stopped in nuclear track emulsion

   D. A. Artemenkov · A. A. Bezbakh · V. Bradnova · M. S. Golovkov · A. V. Gorshkov · G. Kaminsky · N. K. Kornegrutsa · S. A. Krupko · K. Z. Mamatkulov · R. R. Kattabekov · V. V. Rusakova · R. S. Slepnev and 6 other authors

   The fragment separator ACCULINNA in the G. N. Flerov Laboratory of Nuclear Reactions of JINR was used to expose a nuclear track emulsion to a beam of radioactive ${}^8$He nuclei of energy of 60 MeV and enrichment of about 80%. Measurements of decays of ${}^8$He nuclei stopped in the emulsion allow one to evaluate possibilities of $\alpha$-spectrometry and to observe a thermal drift of ${}^8$He atoms in matter. Knowledge of the energy and emission angles of $\alpha$-particles allows one to derive the energy distribution of $\alpha$-decays Q${}_{2\alpha }$. The presence of a "tail" of large values Q${}_{2\alpha }$ is established. The physical reason for the appearance of this "tail" in the distribution Q${}_{2\alpha }$ is not clear. Its shape could allow one to verify calculations of spatial structure of nucleon ensembles emerging as $\alpha$-pairs of decays via the state ${}^8$Be${}_{2+}$.

   nucl-exFew Body Syst.(2014)·2 citations
4. 04*

   Determination of the Free Neutron Lifetime

   J. David Bowman · L. J. Broussard · S. M. Clayton · M. S. Dewey · N. Fomin · K. B. Grammer · G. L. Greene · P. R. Huffman · A. T. Holley · G. L. Jones · C.-Y. Liu · M. Makela and 16 other authors

   We present the status of current US experimental efforts to measure the lifetime of the free neutron by the "beam" and "bottle" methods. BBN nucleosynthesis models require accurate measurements with 1 second uncertainties, which are currently feasible. For tests of physics beyond the standard model, future efforts will need to achieve uncertainties well below 1 second. We outline paths achieve both.

   nucl-exphysics.ins-det10 citations
5. 05*

   Energy Dependence of $K\pi$, $p\pi$, and $Kp$ Fluctuations in Au+Au Collisions from $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}$ = 7.7 to 200 GeV

   STAR Collaboration: L. Adamczyk · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · I. Alekseev · J. Alford · A. Aparin · D. Arkhipkin · E. C. Aschenauer · G. S. Averichev · A. Banerjee and 322 other authors

   A search for the quantum chromodynamics (QCD) critical point was performed by the STAR experiment at the Relativistic Heavy Ion Collider, using dynamical fluctuations of unlike particle pairs. Heavy-ion collisions were studied over a large range of collision energies with homogeneous acceptance and excellent particle identification, covering a significant range in the QCD phase diagram where a critical point may be located. Dynamical $K\pi$, $p\pi$, and $Kp$ fluctuations as measured by the STAR experiment in central 0-5\% Au+Au collisions from center-of-mass collision energies $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}$ = 7.7 to 200 GeV are presented. The observable ${\nu }_{\mathrm{dyn}}$ was used to quantify the magnitude of the dynamical fluctuations in event-by-event measurements of the $K\pi$, $p\pi$, and $Kp$ pairs. The energy dependences of these fluctuations from central 0-5\% Au+Au collisions all demonstrate a smooth evolution with collision energy.

   nucl-exPRC(2015)·34 citations
6. 06*

   Effects of pion potential and nuclear symmetry energy on the ${\pi }^{-}/{\pi }^{+}$ ratio in heavy-ion collisions at beam energies around the pion production threshold

   Wen-Mei Guo🇨🇳 · Gao-Chan Yong🇨🇳 · Hang Liu🇺🇸 · Wei Zuo🇨🇳

   Within the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck(IBUU) transport model, we studied the effects of the pion potential and the symmetry energy on the pion production in the central ${}^{197}Au{+}^{197}Au$ collisions around the pion production threshold. It is found that the pion potential has opposite effects on the value of ${\pi }^{-}/{\pi }^{+}$ ratio at low and high pion energies. The effect of the pion potential on the total ${\pi }^{-}/{\pi }^{+}$ ratio becomes larger in heavy-ion collisions at beam energies below the pion production threshold. And at beam energies below the pion production threshold, with the pion potential, the effect of the symmetry energy on the ${\pi }^{-}/{\pi }^{+}$ ratio becomes smaller compared with that above the pion production threshold.

   ↳ nucl-thnucl-exPRC(2015)·34 citations
7. 07*

   Anisotropic Hydrodynamics: Three lectures

   Michael Strickland🇺🇸

   Anisotropic hydrodynamics is a non-perturbative reorganization of relativistic hydrodynamics that takes into account the large momentum-space anisotropies generated in ultrarelativistic heavy-ion collisions. As a result, it allows one to extend the regime of applicability of hydrodynamic treatments to situations that can be quite far from isotropic thermal equilibrium. In this paper, I review the material presented in a series of three introductory lectures. I review the derivation of ideal and second-order viscous hydrodynamics from kinetic theory. I then show how to extend the methods used to a system that can be highly anisotropic in local-rest-frame momenta. I close by discussing recent work on this topic and then present an outlook to the future.

   ↳ nucl-thhep-phnucl-exActa Phys.Polon.B(2014)·185 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.