Wed·Oct 26, 2016Wednesday·October 26, 2016

1. 01*

   Baryon-Strangeness Correlations in Au+Au Collisions at $\sqrt{s_{\mathrm{NN}}}$=7.7-200 GeV from the UrQMD model

   Zhenzhen Yang🇨🇳 · Xiaofeng Luo🇨🇳 · Bedangadas Mohanty🇮🇳

   Fluctuations and correlations of conserved charges are sensitive observables for studying the QCD phase transition and critical point in high-energy heavy-ion collisions. We have studied the centrality and energy dependence of mixed-cumulants (up to fourth order) between net-baryon and net-strangeness in Au+Au collisions at $\sqrt{s_{NN}}$= 7.7, 11.5, 19.6, 27, 39, 62.4, 200 GeV from UrQMD model. To compare with other theoretical calculations, we normalize these mixed-cumulants by various order cumulants of net-strangeness distributions. We found that the results obtained from UrQMD calculations are comparable with the results from Lattice QCD at low temperature and hadron resonance gas model. The ratios of mixed-cumulants ($R_{11}^{BS},R_{13}^{BS},R_{22}^{BS}$,~$R_{31}^{BS}$) from UrQMD calculations show weak centrality dependence. However, the mixed-cumulant ratios $R_{11}^{BS}$ and $R_{31}^{BS}$ show strong increase at low energy, while the $R_{13}^{BS}$ snd $R_{22}^{BS}$ are similar at different energies. Furthermore, we have also studied the correlations between different hadron species and their contributions to the net-baryon and net-strangeness correlations. These models studies can provide baselines for searching for the signals of QCD phase transition and critical point in heavy-ion collisions.

   nucl-exhep-exhep-phnucl-thPRC(2017)·14 citations
2. 02*

   Activation cross sections of proton and deuteron induced nuclear reactions on holmium and erbium, related to the production of ${}^{161}$Er and ${}^{160}$Er medical isotopes

   F. Tárkányi · F. Ditrói · S. Takács · A. Hermanne · M. Baba

   Experimental excitation functions for long-lived products in proton induced reactions were measured with the activation method in the 37-65 MeV energy range on natural holmium. Stacked foil irradiation technique and high resolution gamma spectrometry were used in order to measure cross-section data for the production of ${}^{161}$Er, ${}^{160}$Er and ${}^{159,157}$Dy. For comparison of the production routes of medically related ${}^{161}$Er and ${}^{160}$Er radioisotopes new experimental cross section data were deduced for the ${}^{162}$Er(p,x)${}^{161,160}$Er and ${}^{162}$Er(d,x)${}^{161,160}$Er reactions by re-evaluating gamma-ray spectra from earlier measurements. No earlier data were found in the literature for these reactions. The experimental data are compared with results of TALYS theoretical code reported in TENDL-2015.

   nucl-exAppl.Radiat.Isot.(2016)·2 citations
3. 03*

   Model Selection for Pion Photoproduction

   J. Landay🇺🇸 · M. Döring🇺🇸 · C. Fernández-Ramírez🇲🇽 · B. Hu🇺🇸 · R. Molina🇺🇸

   Partial-wave analysis of meson and photon-induced reactions is needed to enable the comparison of many theoretical approaches to data. In both energy-dependent and independent parametrizations of partial waves, the selection of the model amplitude is crucial. Principles of the $S$-matrix are implemented to different degree in different approaches, but a many times overlooked aspect concerns the selection of undetermined coefficients and functional forms for fitting, leading to a minimal yet sufficient parametrization. We present an analysis of low-energy neutral pion photoproduction using the Least Absolute Shrinkage and Selection Operator (LASSO) in combination with criteria from information theory and $K$-fold cross validation. These methods are not yet widely known in the analysis of excited hadrons but will become relevant in the era of precision spectroscopy. The principle is first illustrated with synthetic data, then, its feasibility for real data is demonstrated by analyzing the latest available measurements of differential cross sections ($d\sigma /d\Omega$), photon-beam asymmetries ($\Sigma$), and target asymmetry differential cross sections ($d{\sigma }_T/d\Omega$) in the low energy regime.

   ↳ nucl-thhep-phnucl-exPRC(2017)·41 citations
4. 04*

   Unexpected properties of interactions of high energy protons

   I.M. Dremin🇷🇺

   Experimental data on proton-proton interactions in high energy collisions show quite a special and unexpected behaviour of the proportion of elastic scattering compared to inelastic processes with increasing energy. It decreases at the beginning (at comparatively low energies) but then starts increasing. From Intersecting Storage Rings (ISR) energies of 23.5 - 62.5 GeV up to higher energies 7 - 13 TeV at the Large Hadron Collider (LHC) it increases by a factor more than 1.5! According to intuitive classical ideas we would expect a stable tendency with increasing proportion of the break-down of protons compared to their survival probability. One can assume that either the asymptotic freedom or the extremely short time of flight of high energy protons through each other are in charge of such a surprising effect. The unquestionable principle of unitarity combined with the available experimental data on elastic scattering is used to get new conclusions about the shape of the interaction region of colliding protons. Its evolution at present energies is considered. Some predictions about its behaviour at even higher energies are described with different assumptions on relative roles of elastic scattering and inelastic processes. The shape can transform rather drastically if the proportion of elastic processes keeps rising. This unexpected property leads to an unexpected corollary. The possible origin of the effect and its interrelation to the strong interaction dynamics are speculated.

   ↳ hep-phhep-exnucl-exnucl-thPhys.Usp.(2017)·22 citations
5. 05*

   To CME or not to CME? Implications of p+Pb measurements of the chiral magnetic effect in heavy ion collisions

   R. Belmont🇺🇸 · J.L. Nagle🇺🇸

   The Chiral Magnetic Effect (CME) is a fundamental prediction of QCD, and various observables have been proposed in heavy ion collisions to access this physics. Recently the CMS Collaboration \cite{Khachatryan:2016got} has reported results from p+Pb collisions at 5.02 TeV on one such observable, the three-point correlator. The results are strikingly similar to those measured at the same particle multiplicity in Pb+Pb collisions, which have been attributed to the CME. This similarity, combined with two key assumptions about the magnetic field in p+Pb collisions, presents a major challenge to the CME picture. These two assumptions as stated in the CMS paper are (1) that the magnetic field in p+Pb collisions is smaller than that in Pb+Pb collisions and (2) that the magnetic field direction is uncorrelated with the flow angle. We test these two postulates in the Monte Carlo Glauber framework and find that the magnetic fields are not significantly smaller in central p+Pb collisions, however the magnetic field direction and the flow angle are indeed uncorrelated. The second finding alone gives strong evidence that the three-point correlator signal in Pb+Pb and p+Pb is not an indication of the CME. Similar measurements in d+Au over a range of energies accessible at RHIC would be elucidating. In the same calculational framework, we find that even in Pb+Pb collisions, where the magnetic field direction and the flow angle are correlated, there exist large inhomogeneities that are on the size scale of topological domains. These inhomogeneities need to be incorporated in any detailed CME calculation.

   ↳ nucl-thnucl-exPRC(2017)·35 citations
6. 06*

   CAKE: The Coincidence Array for K600 Experiments

   P. Adsley🇿🇦 · R. Neveling · P. Papka🇿🇦 · Z. Dyers · J.W. Brümmer🇿🇦 · C.Aa. Diget · N.J. Hubbard · K.C.W. Li🇿🇦 · A. Long · D.J. Marin-Lambarri🇿🇦 · L. Pellegri🇿🇦 · V. Pesudo🇪🇸 and 3 other authors

   The combination of a magnetic spectrometer and ancillary detectors such as silicon detectors is a powerful tool for the study of nuclear reactions and nuclear structure. This paper discusses the recently commissioned silicon array called the CAKE which is designed for use with the K600 magnetic spectrometer at iThemba LABS.

   ↳ physics.ins-detnucl-exJINST(2017)·16 citations
7. 07*

   Charge conservation effects for high order fluctuations

   Viktor Begun🇵🇱

   The exact charge conservation significantly impacts multiplicity fluctuations. The result depends strongly on the part of the system charge carried by the particles of interest. Along with the expected suppression of fluctuations for large systems, charge conservation may lead to negative skewness or kurtosis for small systems.

   ↳ nucl-thhep-phnucl-exActa Phys.Polon.Supp.(2017)·1 citation

* 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.