Fri·Jan 18, 2019Friday·January 18, 2019

1. 01*

   Event-shape and multiplicity dependence of freeze-out radii in pp collisions at $\sqrt{\text{s}}=7$ TeV

   ALICE Collaboration

   Two-particle correlations in high-energy collision experiments enable the extraction of particle source radii by using the Bose-Einstein enhancement of pion production at low relative momentum $q\propto 1/R$. It was previously observed that in $\mathrm{p}\mathrm{p}$ collisions at $\sqrt{s}=7$ TeV the average pair transverse momentum $k_{\mathrm{T}}$ range of such analyses is limited due to large background correlations which were attributed to mini-jet phenomena. To investigate this further, an event-shape dependent analysis of Bose-Einstein correlations for pion pairs is performed in this work. By categorizing the events by their transverse sphericity $S_{\mathrm{T}}$ into spherical $(S_{\text{T}}>0.7)$ and jet-like $(S_{\text{T}}<0.3)$ events a method was developed that allows for the determination of source radii for much larger values of $k_{\mathrm{T}}$ for the first time. Spherical events demonstrate little or no background correlations while jet-like events are dominated by them. This observation agrees with the hypothesis of a mini-jet origin of the non-femtoscopic background correlations and gives new insight into the physics interpretation of the $k_{\mathrm{T}}$ dependence of the radii. The emission source size in spherical events shows a substantially diminished $k_{\mathrm{T}}$ dependence, while jet-like events show indications of a negative trend with respect to $k_{\mathrm{T}}$ in the highest multiplicity events. Regarding the emission source shape, the correlation functions for both event sphericity classes show good agreement with an exponential shape, rather than a Gaussian one.

   nucl-exhep-exJHEP(2019)·24 citations
2. 02*

   Measurement of directed flow of $D^0$ and $\overline{D^0}$ mesons in 200 GeV Au+Au collisions at RHIC using the STAR detector

   Liang He (for the STAR Collaboration)🇺🇸

   Charm quarks, owing to their large mass, are produced predominantly in the initial hard scatterings in heavy-ion collisions, and therefore can be a valuable tool for studying the early time dynamics of these collisions. The rapidity-odd directed flow at mid-rapidity in heavy-ion collisions originates from a tilt in the reaction plane of the thermalized medium caused by the asymmetry between the number of participants from projectile and target nuclei as a function of rapidity. Recently, it has been predicted that the slope of the directed flow at mid-rapidity for $D^0$ mesons, arising from the transport of charm quarks in the tilted medium, can be several times larger than that of light flavor hadrons. The magnitude of the slope is expected to be sensitive to the magnitude of the tilt and the charm quark drag coefficient in the medium. It has also been predicted that the transient electromagnetic field generated at early time can induce a much larger directed flow for heavy quarks than for light quarks. In these proceedings, we will report on the first measurement of the directed flow for the $D^0$ and ${\bar{D}}^0$ mesons as a function of rapidity in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 200 GeV using high statistics data collected with the Heavy Flavor Tracker in 2014 and 2016 RHIC runs.

   nucl-exhep-exhep-phnucl-thPoS(2019)·3 citations
3. 03*

   Experimental Evidence for Transverse Wobbling in ${}^{105}$Pd

   J. Timár🇭🇺 · Q. B. Chen🇩🇪 · B. Kruzsicz🇭🇺 · D. Sohler🇭🇺 · I. Kuti🇭🇺 · S. Q. Zhang🇨🇳 · J. Meng🇨🇳 · P. Joshi🇬🇧 · R. Wadsworth🇬🇧 · K. Starosta🇨🇦 · A. Algora🇪🇸 · P. Bednarczyk🇵🇱 and 16 other authors

   New rotational bands built on the $\nu$$(h_{11/2})$ configuration have been identified in ${}^{105}$Pd. Two bands built on this configuration show the characteristics of transverse wobbling: the $\Delta$$I$=1 transitions between them have a predominant E2 component and the wobbling energy decreases with increasing spin. The properties of the observed wobbling bands are in good agreement with theoretical results obtained using constrained triaxial covariant density functional theory and quantum particle rotor model calculations. This provides the first experimental evidence for transverse wobbling bands based on a one-neutron configuration, and also represents the first observation of wobbling motion in the $A$$\sim$100 mass region.

   nucl-exnucl-thPRL(2019)·73 citations
4. 04*

   Optimizing the relativistic energy density functional with nuclear ground state and collective excitation properties

   E. Yuksel🇹🇷 · T. Marketin🇭🇷 · N. Paar🇭🇷

   We introduce a new relativistic energy density functional constrained by the ground state properties of atomic nuclei along with the isoscalar giant monopole resonance energy and dipole polarizability in ${}^{208}$Pb. A unified framework of the relativistic Hartree-Bogoliubov model and random phase approximation based on the relativistic density-dependent point coupling interaction is established in order to determine the DD-PCX parameterization by ${\chi }^2$ minimization. This procedure is supplemented with the co-variance analysis in order to estimate statistical uncertainties in the model parameters and observables. The effective interaction DD-PCX accurately describes the nuclear ground state properties including the neutron-skin thickness, as well as the isoscalar giant monopole resonance excitation energies and dipole polarizabilities. The implementation of the experimental data on nuclear excitations allows constraining the symmetry energy close to the saturation density, and the incompressibility of nuclear matter by using genuine observables on finite nuclei in the ${\chi }^2$ minimization protocol, rather than using pseudo-observables on the nuclear matter, or by relying on the ground state properties only, as it has been customary in the previous studies.

   ↳ nucl-thnucl-exPRC(2019)·81 citations
5. 05*

   Rapidity dependent transverse momentum spectra of heavy quarkonia produced in small collision systems at the LHC

   Li-Na Gao🇨🇳 · Fu-Hu Liu🇨🇳 · Bao-Chun Li🇨🇳

   The rapidity dependent transverse momentum spectra of heavy quarkonia (J/psi and Upsilon mesons) produced in small collision systems such as proton-proton (pp) and proton-lead (p-Pb) collisions at center-of-mass energy (per nucleon pair) 5-13 TeV are described by a two-component statistical model which is based on the Tsallis statistics and inverse power-law. The experimental data measured by the LHCb Collaboration at the Large Hadron Collider (LHC) are well fitted by the model results. The related parameters are obtained and the dependences of parameters on rapidity are analyzed.

   ↳ hep-phhep-exnucl-exnucl-thAdv.High Energy Phys.(2019)·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.