Wed·Feb 14, 2018Wednesday·February 14, 2018

1. 01*

   $\eta$ and $\omega$ mesons as new degrees of freedom in the intranuclear cascade model INCL

   J.-C. David🇫🇷 · A. Boudard🇫🇷 · J. Cugnon🇧🇪 · J. Hirtz🇫🇷 · S. Leray🇫🇷 · D. Mancusi🇫🇷 · J. L. Rodriguez-Sanchez🇫🇷

   The intranuclear cascade model INCL (Liège Intranuclear Cascade) is now able to simulate spallation reactions induced by projectiles with energies up to roughly 15 GeV. This was made possible thanks to the implementation of multipion emission in the NN, $\Delta$N and $\pi$N interactions. The results obtained with reactions on nuclei induced by nucleons or pions gave confidence in the model. A next step will be the addition of the strange particles, $\Lambda$, $\Sigma$ and Kaons, in order to not only refine the high-energy modeling, but also to extend the capabilities of INCL, as studying hypernucleus physics. Between those two versions of the code, the possibility to treat the $\eta$ and $\omega$ mesons in INCL has been performed and this is the topic of this paper. Production yields of these mesons increase with energy and it is interesting to test their roles at higher energies. More specifically, studies of $\eta$ rare decays benefit from accurate simulations of its production. These are the two reasons for their implementation. Ingredients of the model, like elementary reaction cross sections, are discussed and comparisons with experimental data are carried out to test the reliability of those particle productions.

   nucl-exnucl-thEur.Phys.J.Plus(2018)·13 citations
2. 02*

   The P2 Experiment - A future high-precision measurement of the electroweak mixing angle at low momentum transfer

   Dominik Becker · Razvan Bucoveanu · Carsten Grzesik · Ruth Kempf · Kathrin Imai · Matthias Molitor · Alexey Tyukin · Marco Zimmermann · David Armstrong · Kurt Aulenbacher · Sebastian Baunack · Rakitha Beminiwattha and 33 other authors

   This article describes the future P2 parity-violating electron scattering facility at the upcoming MESA accelerator in Mainz. The physics program of the facility comprises indirect, high precision search for physics beyond the Standard Model, measurement of the neutron distribution in nuclear physics, single-spin asymmetries stemming from two-photon exchange and a possible future extension to the measurement of hadronic parity violation. The first measurement of the P2 experiment aims for a high precision determination of the weak mixing angle to a precision of 0.14% at a four-momentum transfer of Q^2 = 4.5 10^{-3} GeV^2. The accuracy is comparable to existing measurements at the Z pole. It comprises a sensitive test of the standard model up to a mass scale of 50 TeV, extendable to 70 TeV. This requires a measurement of the parity violating cross section asymmetry -39.94 10^{-9} in the elastic electron-proton scattering with a total accuracy of 0.56 10^-9 (1.4 %) in 10,000 h of 150 \micro A polarized electron beam impinging on a 60 cm liquid H_2 target allowing for an extraction of the weak charge of the proton which is directly connected to the weak mixing angle. Contributions from gamma Z-box graphs become small at the small beam energy of 155 MeV. The size of the asymmetry is the smallest asymmetry ever measured in electron scattering with an unprecedented goal for the accuracy. We report here on the conceptual design of the P2 spectrometer, its Cherenkov detectors, the integrating read-out electronics as well as the ultra-thin, fast tracking detectors. There has been substantial theory work done in preparation of the determination of the weak mixing angle. The further physics program in particle and nuclear physics is described as well.

   nucl-exhep-exhep-phphysics.ins-detEPJA(2018)·234 citations
3. 03*

   Exclusive vector meson photoproduction in fixed - target collisions at the LHC

   V. P. Goncalves🇧🇷 · M. M. Jaime🇧🇷

   The exclusive $\rho$, $\omega$ and $J/\Psi$ photoproduction in fixed - target collisions at the LHC is investigated. We estimate, for the first time, the rapidity and transverse momentum distributions of the vector meson photoproduction in $pHe$, $pAr$, $PbHe$ and $PbAr$ fixed - target collisions at the LHC using the STARlight Monte Carlo and present our results for the total cross sections. Predictions for the kinematical range probed by the LHCb detector are also presented. Our results indicate that the experimental analysis of this process in fixed - target collisions at the LHC is feasible. Such future analysis will probe the QCD dynamics in a kinematical range complementary to that studied in the collider mode.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2018)·15 citations
4. 04*

   Heavy Ion Collisions: The Big Picture, and the Big Questions

   Wit Busza🇺🇸 · Krishna Rajagopal🇺🇸 · Wilke van der Schee🇺🇸

   Heavy ion collisions quickly form a droplet of quark-gluon plasma (QGP) with a remarkably small viscosity. We give an accessible introduction to how to study this smallest and hottest droplet of liquid made on earth and why it is so interesting. The physics of heavy ions ranges from highly energetic quarks and gluons described by perturbative QCD to a bath of strongly interacting gluons at lower energy scales. These gluons quickly thermalize and form QGP, while the energetic partons traverse this plasma and end in a shower of particles called jets. Analyzing the final particles in a variety of different ways allows us to study the properties of QGP and the complex dynamics of multi-scale processes in QCD which govern its formation and evolution, providing what is perhaps the simplest form of complex quantum matter that we know of. Much remains to be understood, and throughout the review big open questions will be encountered.

   ↳ hep-phhep-thnucl-exnucl-thAnn.Rev.Nucl.Part.Sci.(2018)·1140 citations
5. 05*

   One-proton emission from the ${}_{\Lambda }^6$Li hypernucleus

   Tomohiro Oishi🇮🇹

   One-proton (1p) radioactive emission under the influence of the ${\Lambda }^0$-hyperon inclusion is discussed. I investigate the hyper-1p emitter, ${}_{\Lambda }^6$Li, with a time-dependent three-body model. Two-body interactions for $\alpha$-proton and $\alpha$-${\Lambda }^0$ subsystems are determined consistently to their resonant and bound energies, respectively. For a proton-${\Lambda }^0$ subsystem, a contact interaction, which can be linked to the vacuum-scattering length of the proton-${\Lambda }^0$ scattering, is employed. A noticeable sensitivity of the 1p-emission observables to the scattering length of the proton-${\Lambda }^0$ interaction is shown. The ${\Lambda }^0$-hyperon inclusion leads to a remarkable fall of the 1p-resonance energy and width from the hyperon-less $\alpha$-proton resonance. For some empirical values of the proton-${\Lambda }^0$ scattering length, the 1p-resonance width is suggested to be of the order of $0.1-0.01$ MeV. Thus, the 1p emission from ${}_{\Lambda }^6$Li may occur in the timescale of $10^{-20}-10^{-21}$ seconds, which is sufficiently shorter than the self-decay lifetime of ${\Lambda }^0$, $10^{-10}$ seconds. By taking the spin-dependence of the proton-${\Lambda }^0$ interaction into account, a remarkable split of the $J^{\pi }=1^{-}$ and $2^{-}$ 1p-resonance states is predicted. It is also suggested that, if the spin-singlet proton-${\Lambda }^0$ interaction is sufficiently attractive, the 1p emission from the $1^{-}$ ground state is forbidden. From these results, I conclude that the 1p emission can be a suitable phenomenon to investigate the basic properties of the hypernuclear interaction, for which a direct measurement is still difficult.

   ↳ nucl-thnucl-exPRC(2018)·3 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.