Tue·Apr 17, 2018Tuesday·April 17, 2018

1. 01*

   Measurements of the ${\gamma }_{v}p\to p^{\prime }{\pi }^{+}{\pi }^{-}$ cross section with the CLAS detector for $0.4$ GeV${}^2$ $<Q^2<$ $1.0$ GeV${}^2$ and $1.3$ GeV $<W<$ $1.825$ GeV

   G.V. Fedotov · Iu.A. Skorodumina · V.D. Burkert · R.W. Gothe · K. Hicks · V.I. Mokeev · the CLAS Collaboration

   New results on the single-differential and fully-integrated cross sections for the process ${\gamma }_{v}p\to p^{\prime }{\pi }^{+}{\pi }^{-}$ are presented. The experimental data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the kinematic region of the reaction invariant mass $W$ from 1.3 to 1.825 GeV and the photon virtuality $Q^2$ from 0.4 to 1.0 GeV${}^2$. The cross sections were obtained in narrow $Q^2$ bins (0.05 GeV${}^2$) with the smallest statistical uncertainties achieved in double-pion electroproduction experiments to date. The results were found to be in agreement with previously available data where they overlap. A preliminary interpretation of the extracted cross sections, which was based on a phenomenological meson-baryon reaction model, revealed substantial relative contributions from nucleon resonances. The data offer promising prospects to improve knowledge on the $Q^2$-evolution of the electrocouplings of most resonances with masses up to $\sim$1.8 GeV.

   nucl-exhep-exPRC(2018)·29 citations
2. 02*

   Scaling behavior of anisotropic flow harmonics in the far from equilibrium regime

   Nicolas Borghini🇩🇪 · Steffen Feld🇩🇪 · Nina Kersting🇩🇪

   We consider the development of anisotropic flow in an expanding system of particles undergoing very few rescatterings, using a kinetic-theoretical description with a nonlinear collision term. We derive the scaling behaviors of the harmonic coefficients $v_n$ with the initial-state eccentricities and the mean number of rescatterings, and argue that hexagonal flow $v_6$ should follow a nontrivial behavior, different from that of the lower harmonics. Our findings should be observable in experimental data for small systems.

   ↳ nucl-thhep-phnucl-exEPJC(2018)·28 citations
3. 03*

   Further studies of multiplicity derivative in models of heavy ion collision at intermediate energies as a probe for phase transition

   S Das Gupta · S. Mallik🇮🇳 · G. Chaudhuri🇮🇳

   In conjunction with models, the experimental observable total multiplicity can be used to check if the data contain the signature of phase transition and if it is first order. Two of the models reach similar conclusions. The third one is quite different.

   ↳ nucl-thnucl-exPRC(2018)·14 citations
4. 04*

   The novel photon detectors based on MPGD technologies for the upgrade of COMPASS RICH-1

   J.Agarwala🇮🇹 · M.Alexeev🇮🇹 · C.D.R.Azevedo🇵🇹 · R.Birsa🇮🇹 · F.Bradamante🇮🇹 · A.Bressan🇮🇹 · C.Chatterjee🇮🇹 · M.Chiosso🇮🇹 · A.Cicuttin🇮🇹 · P.Ciliberti🇮🇹 · M.L.Crespo🇮🇹 · S.Dalla Torre🇮🇹 and 23 other authors

   The RICH-1 Detector of the COMPASS experiment at CERN SPS has undergone an important upgrade in 2016. Four new photon detectors, based on MPGD technology and covering a total active area larger than 1.2~$m^2$ have replaced the previously used MWPC-based photon detectors. The new detector architecture, resulting from a dedicated, eight years long, R\&D program, consists in a hybrid MPGD combination of two THGEMs and a Micromegas stage; the first THGEM, coated with a CsI layer, acts as a reflective photocathode. The signals are extracted from the anode pads by capacitive coupling and read-out by analog front-end electronics based on the APV25 chip. The new COMPASS RICH-1 photon detectors are described in detail: the detector design, the engineering aspects, the mass production, and the quality assessment are discussed. The assembly of the MPGD components and the installation of the new detectors are illustrated together with the main aspects of the commissioning. Preliminary indication of performance results are also presented.

   ↳ physics.ins-dethep-exnucl-exPoS(2019)·0 citations
5. 05*

   Demonstration of sensitivity increase in mercury free-spin-precession magnetometers due to laser-based readout for neutron electric dipole moment searches

   G. Ban🇫🇷 · G. Bison🇨🇭 · K. Bodek🇵🇱 · M. Daum🇨🇭 · M. Fertl🇨🇭 · B. Franke🇨🇭 · Z. D. Grujić🇨🇭 · W. Heil🇩🇪 · M. Horras🇨🇭 · M. Kasprzak🇨🇭 · Y. Kermaidic🇫🇷 · K. Kirch🇨🇭 and 22 other authors

   We report on a laser based ${}^{199}$Hg co-magnetometer deployed in an experiment searching for a permanent electric dipole moment of the neutron. We demonstrate a more than five times increased signal to-noise-ratio in a direct comparison measurement with its ${}^{204}$Hg discharge bulb-based predecessor. An improved data model for the extraction of important system parameters such as the degrees of absorption and polarization is derived. Laser- and lamp-based data-sets can be consistently described by the improved model which permits to compare measurements using the two different light sources and to explain the increase in magnetometer performance. The laser-based magnetometer satisfies the magnetic field sensitivity requirements for the next generation nEDM experiments.

   ↳ physics.ins-dethep-exnucl-exphysics.atom-phNucl.Instrum.Meth.A(2018)·16 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.