Thu·Feb 15, 2018Thursday·February 15, 2018

1. 01*

   Three-body correlations in direct reactions: Example of ${}^6$Be populated in $(p,n)$ reaction

   V. Chudoba (1,2) · L. V. Grigorenko (1,3,4) · A. S. Fomichev (1) · A. A. Bezbakh (1) · I. A. Egorova (5,6) · S. N. Ershov (5) · M. S. Golovkov (1) · A. V. Gorshkov (1) · V. A. Gorshkov (1) · G. Kaminski (1,7) S. A. Krupko (1) · I. Mukha (8) · E. Yu. Nikolskii (4, 1) and 9 other authors

   The ${}^6$Be continuum states were populated in the charge-exchange reaction ${}^1$H(${}^6$Li,${}^6$Be)$n$ collecting very high statistics data ($\sim 5\times 10^6$ events) on the three-body $\alpha$+$p$+$p$ correlations. The ${}^6$Be excitation energy region below $\sim 3$ MeV is considered, where the data are dominated by contributions from the $0^{+}$ and $2^{+}$ states. It is demonstrated how the high-statistics few-body correlation data can be used to extract detailed information on the reaction mechanism. Such a derivation is based on the fact that highly spin-aligned states are typically populated in the direct reactions.

   nucl-exPRC(2018)·6 citations
2. 02*

   Axial Charge Fluctuation and Chiral Magnetic Effect from Stochastic Hydrodynamics

   Shu Lin🇨🇳 · Li Yan🇨🇦 · Gui-Rong Liang🇨🇳

   The amount of axial charge produced in heavy ion collisions is one of the key quantities in understanding chiral magnetic effect. Current phenomenological studies assume large axial charge chemical potential ${\mu }_5$ produced in Glasma phase and assume the conservation of axial charge throughout the evolution, which is valid in the long relaxation time limit. Based on the solution of stochastic hydrodynamics with phenomenological parameters, our study suggests that the situation of heavy ion collisions may be close to the opposite limit, in which axial charge fluctuation approaches thermodynamic limit. Using ${\mu }_5$ set by the thermodynamic limit for chiral magnetic effect and a background from parity-even $v_1$, we obtain a reasonable description of the centrality dependence of charged particle correlation measured in experiment.

   ↳ nucl-thhep-phnucl-exPRC(2018)·22 citations
3. 03*

   Hadronic Paschen-Back effect

   Sachio Iwasaki🇯🇵 · Makoto Oka🇯🇵 · Kei Suzuki🇯🇵 · Tetsuya Yoshida🇯🇵

   We find a novel phenomenon induced by the interplay between a strong magnetic field and finite orbital angular momenta in hadronic systems, which is analogous to the Paschen-Back effect observed in the field of atomic physics. This effect allows the wave functions to drastically deform. We discuss anisotropic decay from the deformation as a possibility to measure the strength of the magnetic field in heavy-ion collision at LHC, RHIC and SPS, which has not experimentally been measured. As an example we investigate charmonia with a finite orbital angular momentum in a strong magnetic field. We calculate the mass spectra and mixing rates. To obtain anisotropic wave functions, we apply the cylindrical Gaussian expansion method, where the Gaussian bases to expand the wave functions have different widths along transverse and longitudinal directions in the cylindrical coordinate.

   ↳ hep-phhep-exnucl-exnucl-th+1PLB(2019)·17 citations
4. 04*

   Virtual depth by active background suppression: Revisiting the cosmic muon induced background of GERDA Phase II

   C. Wiesinger🇩🇪 · L. Pandola🇮🇹 · S. Schönert🇩🇪

   In-situ production of long-lived isotopes by cosmic muon interactions may generate a non-negligible background for deep underground rare event searches. Previous Monte Carlo studies for the GERDA experiment at LNGS identified the delayed decays of ${}^{77}$Ge and its metastable state ${}^{77m}$Ge as dominant cosmogenic background in the search for neutrinoless double beta decay of ${}^{76}$Ge. This might limit the sensitivity of next generation experiments aiming for increased ${}^{76}$Ge mass at background-free conditions and thereby define a minimum depth requirement. A re-evaluation of the ${}^{77(m)}$Ge background for the GERDA experiment has been carried out by a set of Monte Carlo simulations. The obtained ${}^{77(m)}$Ge production rate is (0.21$\pm$0.01) nuclei/(kg$\cdot$yr). After application of state-of-the-art active background suppression techniques and simple delayed coincidence cuts this corresponds to a background contribution of (2.7$\pm$0.3)$\cdot 10^{-6}$ cts/(keV$\cdot$kg$\cdot$yr). The suppression achieved by this strategy equals an effective muon flux reduction of more than one order of magnitude. This virtual depth increase opens the way for next generation rare event searches.

   ↳ hep-exnucl-exphysics.ins-detEPJC(2018)·27 citations
5. 05*

   Dynamical and statistical bimodality in nuclear fragmentation

   S.Mallik🇮🇳 · G. Chaudhuri🇮🇳 · F. Gulminelli🇫🇷

   The origin of bimodal behavior in the residue distribution experimentally measured in heavy ion reactions is reexamined using Boltzmann-Uehling-Uhlenbeck simulations. We suggest that, depending on the incident energy and impact parameter of the reaction, both entrance channel and exit channel effects can be at the origin of the observed behavior. Specifically, fluctuations in the reaction mechanism induced by fluctuations in the collision rate, as well as thermal bimodality directly linked to the nuclear liquid-gas phase transition are observed in our simulations. Both phenomenologies were previously proposed in the literature, but presented as incompatible and contradictory interpretations of the experimental measurements. These results indicate that heavy ion collisions at intermediate energies can be viewed as a powerful tool to study both bifurcations induced by out-of-equilibrium critical phenomena, as well as finite size precursors of thermal phase transitions.

   ↳ nucl-thnucl-exPRC(2018)·14 citations
6. 06*

   First Extraction of Transversity from a Global Analysis of Electron-Proton and Proton-Proton Data

   Marco Radici🇮🇹 · Alessandro Bacchetta🇮🇹

   We present the first extraction of the transversity distribution in the framework of collinear factorization based on the global analysis of pion-pair production in deep-inelastic scattering off transversely polarized targets and in proton-proton collisions with one transversely polarized proton. The extraction relies on the knowledge of di-hadron fragmentation functions, which are taken from the analysis of electron-positron annihilation data. For the first time, the chiral-odd transversity is extracted from a global analysis similar to what is usually done for the chiral-even spin-averaged and helicity distributions. The knowledge of transversity is important for, among other things, detecting possible signals of new physics in high-precision low-energy experiments.

   ↳ hep-phhep-exnucl-exnucl-thPRL(2018)·145 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.