Wed·Jun 6, 2018Wednesday·June 6, 2018

1. 01*

   First results on nucleon resonance photocouplings from the $\gamma p\to {\pi }^{+}{\pi }^{-}p$ reaction

   CLAS Collaboration: E. Golovatch🇷🇺 · V. D. Burkert🇺🇸 · D. S. Carman🇺🇸 · R. W. Gothe🇺🇸 · K. Hicks🇺🇸 · B. S. Ishkhanov🇷🇺 · V.I. Mokeev🇺🇸 · E. Pasyuk🇺🇸 · S. Adhikari🇺🇸 · Z. Akbar🇺🇸 · M. J. Amaryan🇺🇸 · H. Avakian🇺🇸 and 117 other authors

   We report the first experimental measurements of the nine 1-fold differential cross sections for the $\gamma p\to {\pi }^{+}{\pi }^{-}p$ reaction, obtained with the CLAS detector at Jefferson Laboratory. The measurements cover the invariant mass range of the final state hadrons from 1.6~GeV~$<W<$~2.0~GeV. For the first time the photocouplings of all prominent nucleon resonances in this mass range have been extracted from this exclusive channel. Photoproduction of two charged pions is of particular importance for the evaluation of the photocouplings for the $\Delta (1620)1/2^{-}$, $\Delta (1700)3/2^{-}$, $N(1720)3/2^{+}$, and $\Delta (1905)5/2^{+}$ resonances, which have dominant decays into the $\pi \pi N$ final states rather than the more extensively studied single meson decay channels.

   nucl-exPLB(2019)·47 citations
2. 02*

   Estimation of the freeze-out parameters reachable in the AFTER@LHC project

   Viktor Begun🇵🇱 · Daniel Kikoła🇵🇱 · Volodymyr Vovchenko🇩🇪 · Daniel Wielanek🇵🇱

   Estimation of the freeze-out parameters as the function of rapidity in Pb+Pb collisions at $\sqrt{s_{NN}}=72$ GeV in the AFTER@LHC project is performed. The conventional hadron resonance gas model is used for the analysis of the events generated by the UrQMD model. The results indicate that one may obtain at least $2.5$ times increase of baryon chemical potential ${\mu }_B$ in the forward rapidity range as compared to the mid-rapidity. The ${\mu }_B$ values in the rapidity range of $0<y<4.5$ for AFTER@LHC are comparable to that covered by the RHIC Beam Energy Scan program. Thus, a rapidity scan in the AFTER@LHC project provides a complementary approach to study the QCD phase diagram.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2018)·17 citations
3. 03*

   Trigger and Timing Distributions using the TTC-PON and GBT Bridge Connection in ALICE for the LHC Run 3 Upgrade

   Jubin Mitra🇮🇳 · Erno David🇭🇺 · Eduardo Mendez🇨🇭 · Shuaib Ahmad Khan🇮🇳 · Tivadar Kiss🇭🇺 · Sophie Baron🇨🇭 · Alex Kluge🇨🇭 · Tapan Nayak🇮🇳

   The ALICE experiment at CERN is preparing for a major upgrade for the third phase of data taking run (Run 3), when the high luminosity phase of the Large Hadron Collider (LHC) starts. The increase in the beam luminosity will result in high interaction rate causing the data acquisition rate to exceed 3 TB/sec. In order to acquire data for all the events and to handle the increased data rate, a transition in the readout electronics architecture from the triggered to the trigger-less acquisition mode is required. In this new architecture, a dedicated electronics block called the Common Readout Unit (CRU) is defined to act as a nodal communication point for detector data aggregation and as a distribution point for timing, trigger and control (TTC) information. TTC information in the upgraded triggerless readout architecture uses two asynchronous high-speed serial links connections: the TTC-PON and the GBT. We have carried out a study to evaluate the quality of the embedded timing signals forwarded by the CRU to the connected electronics using the TTC-PON and GBT bridge connection. We have used four performance metrics to characterize the communication bridge: (a)the latency added by the firmware logic, (b)the jitter cleaning effect of the PLL on the timing signal, (c)BER analysis for quantitative measurement of signal quality, and (d)the effect of optical transceivers parameter settings on the signal strength. Reliability study of the bridge connection in maintaining the phase consistency of timing signals is conducted by performing multiple iterations of power on/off cycle, firmware upgrade and reset assertion/de-assertion cycle (PFR cycle). The test results are presented and discussed concerning the performance of the TTC-PON and GBT bridge communication chain using the CRU prototype and its compliance with the ALICE timing requirements.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2019)·7 citations
4. 04*

   Coupling charge-exchange vibrations to nucleons in a relativistic framework: effect on Gamow-Teller transitions and beta-decay half-lives

   Caroline Robin🇺🇸 · Elena Litvinova🇺🇸

   The nuclear response theory for isospin-transfer modes in the relativistic particle-vibration coupling framework is extended to include coupling of single nucleons to isospin-flip (charge-exchange) phonons, in addition to the usual neutral vibrations. This new coupling introduces dynamical pion and rho-meson exchange, beyond the Hartree-Fock approximation, up to infinite order. We investigate the impact of this new mechanism on the Gamow-Teller response of a few doubly-magic neutron-rich nuclei, namely ${}^{48}$Ca, ${}^{78}$Ni, ${}^{132}$Sn and ${}^{208}$Pb. It is found that the coupling to isospin-flip vibrations can have a non negligible impact on the strength distribution and quenching of the giant resonance, globally improving the agreement with the experimental data. The corresponding beta-decay half-lives of ${}^{78}$Ni and ${}^{132}$Sn are also calculated, and found to be decreased by a factor $\sim 2$ by the inclusion of the new phonons.

   ↳ nucl-thnucl-exPRC(2018)·38 citations
5. 05*

   Toward simulation of quark and diquark fragmentations in the Quark-Gluon String Model (QGSM)

   V. Uzhinsky🇷🇺 · A. Galoyan🇷🇺

   Within the Quark-Gluon String Model A.B. Kaidalov found a behaviour of quark and diquark fragmentation functions for $z\to 0$ and $z\to 1$, and proposed interpolation formulae for the functions in the whole region of $z$. These functions must be a solution of the well-known system of the integral equations. A simplified Monte Carlo estimation of the functions, based on usage of the fragmentation functions at $z\to 1$ as the kernel functions of the system, does not reproduce Kaidalov's results. An improvement of the Monte Carlo simulations is proposed in this paper. It can be implemented in Monte Carlo event generators such as Los Alamos QGSM, QGSJet-II and the Geant4 QGS model. It will improve a description of experimental data in the models, especially, the description of the latest NA61/SHINE Collaboration data on $\pi \mathrm{C}$ interactions. Description of the data is a problem in DPMJet, QGSJet, EPOS and Sibyll models.

   ↳ hep-phhep-exnucl-exPhys.Part.Nucl.Lett.(2019)·1 citation
6. 06*

   Two-photon exchange correction in elastic lepton-proton scattering

   Oleksandr Tomalak🇩🇪

   We present the dispersion relation approach based on unitarity and analyticity to evaluate the two-photon exchange contribution to elastic electron-proton scattering. The leading elastic and first inelastic $\pi N$ intermediate state contributions are accounted for in the region of small momentum transfer $Q^2<1{\mathrm{GeV}}^2$ based on the available data input. The novel methods of analytical continuation allow us to exploit the MAMI form factor data and the MAID parameterization for the pion electroproduction amplitudes as input in the calculation. The results are compared to the recent CLAS, VEPP-3 and OLYMPUS data as well as to the full two-photon exchange correction in the near-forward approximation, which is based on the Christy and Bosted unpolarized structure functions fit. Additionally, predictions are given for a forthcoming muon-proton scattering experiment.

   ↳ hep-phnucl-exnucl-thFew Body Syst.(2018)·15 citations
7. 07*

   Semiclassical calculations of complete and incomplete fusion in collisions of weakly bound nuclei

   G.D. Kolinger · L.F. Canto🇧🇷 · R. Donangelo🇧🇷 · S.R. Souza🇧🇷

   We use an improved version of the semiclassical method described in Refs. [1,2,3] to evaluate fusion cross sections in collisions of weakly bound nuclei. This version takes into account the static effects of the low breakup threshold, uses better bin states in the discretization of the continuum and avoids the excitation of closed channels. The population of these channels is a consequence of the violation of energy conservation, which is inherent in the semiclassical method. The method is employed to evaluate complete fusion and total fusion cross section in collisions of the weakly bound 6,7Li projectiles with 159Tb and 197Au targets, for which data is available. The overall agreement between theory and experiment is fairly good.

   ↳ nucl-thnucl-exPRC(2018)·18 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.