Fri·Aug 14, 2015Friday·August 14, 2015

1. 01*

   Exclusive ${\rho }^0$ Meson Photoproduction with a Leading Neutron at HERA

   H1 Collaboration

   A first measurement is presented of exclusive photoproduction of ${\rho }^0$ mesons associated with leading neutrons at HERA. The data were taken with the H1 detector in the years $2006$ and $2007$ at a centre-of-mass energy of $\sqrt{s}=319$ GeV and correspond to an integrated luminosity of $1.16$ pb${}^{-1}$. The ${\rho }^0$ mesons with transverse momenta $p_T<1$ GeV are reconstructed from their decays to charged pions, while leading neutrons carrying a large fraction of the incoming proton momentum, $x_L>0.35$, are detected in the Forward Neutron Calorimeter. The phase space of the measurement is defined by the photon virtuality $Q^2<2$ GeV${}^2$, the total energy of the photon-proton system $20<W_{\gamma p}<100$ GeV and the polar angle of the leading neutron ${\theta }_n<0.75$ mrad. The cross section of the reaction $\gamma p\to {\rho }^{0}n{\pi }^{+}$ is measured as a function of several variables. The data are interpreted in terms of a double peripheral process, involving pion exchange at the proton vertex followed by elastic photoproduction of a ${\rho }^0$ meson on the virtual pion. In the framework of one-pion-exchange dominance the elastic cross section of photon-pion scattering, ${\sigma }^{\mathrm{el}}(\gamma {\pi }^{+}\to {\rho }^0{\pi }^{+})$, is extracted. The value of this cross section indicates significant absorptive corrections for the exclusive reaction $\gamma p\to {\rho }^{0}n{\pi }^{+}$.

   ↳ hep-exhep-phnucl-exnucl-thEPJC(2016)·25 citations
2. 02*

   Survival rate of initial azimuthal anisotropy in a multi-phase transport model

   Liang Zhang🇨🇳 · Feng Liu🇨🇳 · Fuqiang Wang🇺🇸

   We investigate the survival rate of an initial momentum anisotropy ($v_2^{ini}$), not spatial anisotropy, to the final state in a multi-phase transport (AMPT) model in Au+Au collisions at $\sqrt{s_{NN}}$=200~GeV. It is found that both the final-state parton and charged hadron $v_2$ show a linear dependence versus $v_2^{ini}\{\mathrm{PP}\}$ with respect to the participant plane (PP). It is found that the slope of this linear dependence (referred to as the survive rate) increases with transverse momentum ($p_T$), reaching~$\sim$100\% at $p_T$$\sim$2.5 GeV/c for both parton and charged hadron. The survival rate decreases with collision centrality and energy, indicating decreasing survival rate with increasing interactions. It is further found that a $v_2^{ini}\{\mathrm{Rnd}\}$ with respect to a random direction does not survive in $v_2\{\mathrm{PP}\}$ but in the two-particle cumulant $v_2\{2\}$. The dependence of $v_2\{2\}$ on $v_2^{ini}\{\mathrm{Rnd}\}$ is quadratic rather than linear.

   ↳ nucl-thnucl-exPRC(2015)·2 citations
3. 03*

   Long-Term Stability of Underground Operated CZT Detectors Based on the Analysis of Intrinsic ${}^{113}$Cd \beta${}^{-}$-Decay

   J. Ebert🇩🇪 · C. Goessling🇩🇪 · D. Gehre🇩🇪 · C. Hagner🇩🇪 · N. Heidrich🇩🇪 · R. Klingenberg🇩🇪 · K. Kroeninger🇩🇪 · C. Nitsch🇩🇪 · C. Oldorf🇩🇪 · T. Quante🇩🇪 · S. Rajek🇩🇪 · H. Rebber🇩🇪 and 8 other authors

   The COBRA collaboration operates a demonstrator setup at the underground facility LNGS (Laboratori Nazionali del Gran Sasso, located in Italy) to prove the technological capabilities of this concept for the search for neutrinoless double beta-decay. The setup consists of 64 $(1\times 1\times 1)$ cm${}^3$ CZT detectors in CPG configuration. One purpose of this demonstrator is to test if reliable long-term operation of CZT-CPG detectors in such a setup is possible. The demonstrator has been operated under ultra low-background conditions since more than three years and collected data corresponding to an exposure of 218 kg$\cdot$days. The presented study focuses on the long-term stability of CZT detectors by analyzing the intrinsic, fourfold forbidden non-unique ${}^{113}$Cd single beta-decay. It can be shown that CZT detectors can be operated stably for long periods of time and that the ${}^{113}$Cd single beta-decay can be used as an internal monitor of the detector performance during the runtime of the experiment.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2016)·9 citations
4. 04*

   Melting Hadrons, Boiling Quarks

   Johann Rafelski🇺🇸

   In the context of the Hagedorn temperature half-centenary I describe our understanding of the hot phases of hadronic matter both below and above the Hagedorn temperature. The first part of the review addresses many frequently posed questions about properties of hadronic matter in different phases, phase transition and the exploration of quark-gluon plasma (QGP). The historical context of the discovery of QGP is shown and the role of strangeness and strange antibaryon signature of QGP illustrated. In the second part I discuss the corresponding theoretical ideas and show how experimental results can be used to describe the properties of QGP at hadronization. The material of this review is complemented by two early and unpublished reports containing the prediction of the different forms of hadron matter, and of the formation of QGP in relativistic heavy ion collisions, including the discussion of strangeness, and in particular strange antibaryon signature of QGP.

   ↳ nucl-thhep-exhep-phnucl-ex+1EPJA(2015)·61 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.