Wed·Jan 31, 2018Wednesday·January 31, 2018

1. 01*

   Nucleon Resonance Structure from Exclusive Meson Electroproduction with CLAS

   Victor I. Mokeev🇺🇸

   Studies of the nucleon resonance electroexcitation amplitudes in a wide range of photon virtualities offer unique information on many facets of strong QCD behind the generation of all prominent excited nucleon states. Advances in the evaluation of resonance electroexcitation amplitudes from the data measured with the CLAS detector and the future extension of these studies with the CLAS12 detector at Jefferson Lab are presented. For the first time, analyses of ${\pi }^{0}p$, ${\pi }^{+}n$, $\eta p$, and ${\pi }^{+}{\pi }^{-}p$ electroproduction off proton channels have provided electroexcitation amplitudes of most resonances in the mass range up to 1.8 GeV and at photon virtualities $Q^2<5$~GeV${}^2$.Studies of the resonance electroexcitation amplitudes revealed the $N^{\ast }$ structure as a complex interplay between the inner core of three dressed quarks and the external meson-baryon cloud. The successful description of the $\Delta (1232)3/2^{+}$ and $N(1440)1/2^{+}$ electrocouplings achieved within the Dyson-Schwinger Equation approach under a traceable connection to the QCD Lagrangian and supported by the novel light front quark model demonstrated the relevance of dressed quarks with dynamically generated masses as an active structural component in baryons. Future experiments with the CLAS12 detector will offer insight into the structure of all prominent resonances at the highest photon virtualities, $Q^2<12$~GeV${}^2$, ever achieved in exclusive reactions, thus addressing the most challenging problems of the Standard Model on the nature of hadron mass, quark-gluon confinement, and the emergence of nucleon resonance structures from QCD. A search for new states of hadronic matter, the so-called hybrid-baryons with glue as a structural component, will complete the long term efforts on the resonance spectrum exploration.

   nucl-exhep-phFew Body Syst.(2018)·26 citations
2. 02*

   N* Experiments and their Impact on Strong QCD Physics

   Volker D. Burkert🇺🇸

   I give a brief overview of experimental studies of the spectrum and the structure of the excited states of the nucleon and what we learn about their internal structure. The focus is on the effort to obtain a more complete picture of the light-quark baryon excitation spectrum employing electromagnetic beams, and on the study of the transition form factors and helicity amplitudes and their dependence on the magnitude of the photon virtuality $Q^2$, especially for some of the most prominent resonances. The results were obtained in pion and eta electroproduction experiments off proton targets. They strengthen the connection of experiment and new results from modeling sQCD in DSE and Light Cone SR approaches. They also point to the nature of these states as 3-quark excitations at the core.

   nucl-exhep-phnucl-thFew Body Syst.(2018)·21 citations
3. 03*

   What does the matter created in high multiplicity proton-nucleus collisions teach us about the 3-D structure of the proton?

   K. Dusling🇺🇸 · M. Mace🇺🇸 · R. Venugopalan🇺🇸

   The study of multiparticle correlations and collectivity in the hot and dense matter created in collisions of heavy-ions as well as those of smaller systems such as proton--heavy-ion collisions has progressed to the point where detailed knowledge of the three-dimensional structure of the proton is needed to confront experimental data. We discuss results from a simple proof-of-principle initial state parton model which reproduces many features of the data on proton--heavy-ion collisions that are often ascribed to hydrodynamic flow. We outline how this model can be further improved with particular emphasis on missing elements in our understanding of the dynamical spatial and momentum structure of the proton.

   ↳ hep-phnucl-exnucl-thPoS(2018)·7 citations
4. 04*

   $N^{\ast }$ Production from $e^{+}{e}^{-}$ Annihilations

   Bing-Song Zou🇨🇳

   Up to now, the $N^{\ast }$ production from $e^{+}{e}^{-}$ annihilations has been studied only around charmonium region. Charmonium decays to $N^{\ast }$s are analogous to (time-like) EM form factors in that the charm quark annihilation provides a nearly pointlike (ggg) current. Complementary to other sources, such as $\pi N$, $eN$ and $\gamma N$ reactions, this new source for $N^{\ast }$ spectroscopy has a few advantages, such as an isospin filter and a low spin filter. The experimental results on $N^{\ast }$ from $e^{+}{e}^{-}$ annihilations and their phenomenological implications are reviewed. Possible new sources on $N^{\ast }$ production from $e^{+}{e}^{-}$ annihilations are discussed.

   ↳ hep-phhep-exnucl-exnucl-th5 citations
5. 05*

   Direct dark matter search by annual modulation with 2.7 years of XMASS-I data

   XMASS Collaboration: K. Abe🇯🇵 · K. Hiraide🇯🇵 · K. Ichimura🇯🇵 · Y. Kishimoto🇯🇵 · K. Kobayashi🇯🇵 · M. Kobayashi🇯🇵 · S. Moriyama🇯🇵 · M. Nakahata🇯🇵 · T. Norita🇯🇵 · H. Ogawa🇯🇵 · K. Sato🇯🇵 · H. Sekiya🇯🇵 and 29 other authors

   An annual modulation signal due to the Earth orbiting around the Sun would be one of the strongest indications of the direct detection of dark matter. In 2016, we reported a search for dark matter by looking for this annual modulation with our single-phase liquid xenon XMASS-I detector. That analysis resulted in a slightly negative modulation amplitude at low energy. In this work, we included more than one year of additional data, which more than doubles the exposure to 800 live days with the same 832 kg target mass. When we assume weakly interacting massive particle (WIMP) dark matter elastically scattering on the xenon target, the exclusion upper limit for the WIMP-nucleon cross section was improved by a factor of 2 to 1.9$\times$10${}^{-41}$cm${}^2$ at 8 GeV/c${}^2$ at 90\% confidence level with our newly implemented data selection through a likelihood method. For the model-independent case, without assuming any specific dark matter model, we obtained more consistency with the null hypothesis than before with a $p$-value of 0.11 in the 1$-$20 keV energy region. This search probed this region with an exposure that was larger than that of DAMA/LIBRA. We also did not find any significant amplitude in the data for periodicity with periods between 50 and 600 days in the energy region between 1 to 6 keV.

   ↳ astro-ph.COhep-exnucl-exPRD(2018)·47 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.