Wed·Jul 8, 2015Wednesday·July 8, 2015

1. 01*

   The isospin structure of photoproduction of pi-eta pairs from the nucleon in the threshold region

   A. Käser🇨🇭 · J. Ahrens🇩🇪 · J.R.M. Annand🇬🇧 · H.J. Arends🇩🇪 · K. Bantawa🇺🇸 · P.A. Bartolome🇩🇪 · R. Beck🇩🇪 · V. Bekrenev🇷🇺 · H. Berghäuser🇩🇪 · A. Braghieri🇮🇹 · D. Branford🇬🇧 · W.J. Briscoe🇺🇸 and 62 other authors

   Photoproduction of $\pi \eta$-pairs from nucleons has been investigated from threshold up to incident photon energies of $\approx$~1.4~GeV. The quasi-free reactions $\gamma p\to p{\pi }^0\eta$, $\gamma n\to n{\pi }^0\eta$, $\gamma p\to n{\pi }^{+}\eta$, and $\gamma n\to p{\pi }^{-}\eta$ were for the first time measured from nucleons bound in the deuteron. The corresponding reactions from a free-proton target were also studied to investigate final-state interaction effects (for neutral pions the free-proton results could be compared to previous measurements; the $\gamma p\to n{\pi }^{+}\eta$ reaction was measured for the first time). For the ${\pi }^0\eta$ final state coherent production via the $\gamma d\to d{\pi }^0\eta$ reaction was also investigated. The experiments were performed at the tagged photon beam of the Mainz MAMI accelerator using an almost $4\pi$ coverage electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. The total cross sections for the four different final states obey the relation $\sigma (p{\pi }^0\eta )$ $\approx$ $\sigma (n{\pi }^0\eta )$ $\approx$ $2\sigma (p{\pi }^{-}\eta )$ $\approx$ $2\sigma (n{\pi }^{+}\eta )$ as expected for a dominant contribution from a ${\Delta }^{\star }\to \eta \Delta (1232)\to \pi \eta N$ reaction chain, which is also supported by the shapes of the invariant-mass distributions of nucleon-meson and $\pi$-$\eta$ pairs. The experimental results are compared to the predictions from an isobar reaction model.

   nucl-exPLB(2015)·21 citations
2. 02*

   The road to precision: Extraction of the specific shear viscosity of the quark-gluon plasma

   Chun Shen🇺🇸 · Ulrich Heinz🇺🇸

   Recent progress in extracting the specific shear viscosity of the Quark-Gluon Plasma from phenomenological studies is highlighted.

   ↳ nucl-thhep-phnucl-exNucl.Phys.News(2015)·69 citations
3. 03*

   Universality of multiplicity distribution in proton-proton and electron-positron collisions

   Adam Bzdak🇵🇱

   It is argued that the multiplicity distribution in proton-proton ($pp$) collisions, which is often parameterized by the negative binomial distribution, may result from the multiplicity distribution measured in electron-positron ($e^{+}{e}^{-}$) collisions, once the fluctuating energy carried by two leading protons in $pp$ is taken into account.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2017)·5 citations
4. 04*

   Searching for observable effects induced by anomalous triangle singularities

   Xiao-Hai Liu🇯🇵 · Makoto Oka🇯🇵 · Qiang Zhao🇨🇳

   We investigate the anomalous triangle singularity (ATS) and its possible manifestations in various processes. We show that the ATS should have important impact on our understanding of the nature of some newly observed threshold states. Discussions on how to distinguish the ATS phenomena from genuine dynamic pole structures are presented.

   ↳ hep-phhep-exnucl-exnucl-thPLB(2016)·146 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.