Mon·Jun 13, 2016Monday·June 13, 2016

1. 01*

   Parametrizations of the ${\gamma }^{\ast }N\to \Delta (1232)$ quadrupole form factors and Siegert's theorem

   G. Ramalho🇧🇷

   The large $N_c$ limit provides relations that can be used to calculate the ${\gamma }^{\ast }N\to \Delta (1232)$ quadrupole form factors at low and intermediate $Q^2$ under the assumption of the pion cloud dominance. There are two limitations in those parametrizations. First, the parametrization of the Coulomb quadrupole form factor underestimate the low $Q^2$ data. Second, when extrapolated for the timelike region, the form factors violate Siegert's theorem by terms of the order $1/N_c^2$. We propose here corrections to the parametrization of the electric quadrupole form factor, which violate Siegert's theorem only by terms of the order $1/N_c^4$. Combining the improved large $N_c$ pion cloud parametrizations with the valence quark contributions based on a covariant quark model for the quadrupole transition form factors, we obtain an extrapolation to the timelike region consistent with Siegert's theorem, and accomplish also a very good description of the data.

   ↳ hep-phhep-latnucl-exnucl-thPRD(2016)·29 citations
2. 02*

   Dependence of two-proton radioactivity on nuclear pairing models

   Tomohiro Oishi🇮🇹 · Markus Kortelainen🇫🇮 · Alessandro Pastore🇬🇧

   Sensitivity of two-proton emitting decay to nuclear pairing correlation is discussed within a time-dependent three-body model. We focus on the ${}^6$Be nucleus assuming $\alpha +p+p$ configuration, and its decay process is described as a time-evolution of the three-body resonance state. For a proton-proton subsystem, a schematic density-dependent contact (SDDC) pairing model is employed. From the time-dependent calculation, we observed the exponential decay rule of a two-proton emission. It is shown that the density dependence does not play a major role in determining the decay width, which can be controlled only by the asymptotic strength of the pairing interaction. This asymptotic pairing sensitivity can be understood in terms of the dynamics of the wave function driven by the three-body Hamiltonian, by monitoring the time-dependent density distribution. With this simple SDDC pairing model, there remains an impossible trinity problem: it cannot simultaneously reproduce the empirical $Q$ value, decay width, and the nucleon-nucleon scattering length. This problem suggests that a further sophistication of the theoretical pairing model is necessary, utilizing the two-proton radioactivity data as the reference quantities.

   ↳ nucl-thnucl-exPRC(2017)·29 citations
3. 03*

   Theoretical estimate on tensor-polarization asymmetry in proton-deuteron Drell-Yan process

   S. Kumano🇯🇵 · Qin-Tao Song🇯🇵

   Tensor-polarized parton distribution functions are new quantities in spin-one hadrons such as the deuteron, and they could probe new quark-gluon dynamics in hadron and nuclear physics. In charged-lepton deep inelastic scattering (DIS), they are studied by the twist-two structure functions $b_1$ and $b_2$. The HERMES collaboration found unexpectedly large $b_1$ values than a naive theoretical expectation based on the standard deuteron model. The situation should be significantly improved in the near future by an approved experiment to measure $b_1$ at JLab (Thomas Jefferson National Accelerator Facility). There is also an interesting indication in the HERMES result that finite antiquark tensor polarization exists. It could play an important role in solving a mechanism on tensor structure in the quark-gluon level. The tensor-polarized antiquark distributions are not easily determined from the charged-lepton DIS; however, they can be measured in a proton-deuteron Drell-Yan process with a tensor-polarized deuteron target. In this article, we estimate the tensor-polarization asymmetry for a possible Fermilab Main-Injector experiment by using optimum tensor-polarized PDFs to explain the HERMES measurement. We find that the asymmetry is typically a few percent. If it is measured, it could probe new hadron physics, and such studies could create an interesting field of high-energy spin physics. In addition, we find that a significant tensor-polarized gluon distribution should exist due to $Q^2$ evolution, even if it were zero at a low $Q^2$ scale. The tensor-polarized gluon distribution has never been observed, so that it is an interesting future project.

   ↳ hep-phhep-exhep-latnucl-ex+1PRD(2016)·30 citations
4. 04*

   Understanding the internal structures of the $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$

   Hua-Xing Chen🇨🇳 · Er-Liang Cui🇨🇳 · Wei Chen🇨🇦 · Xiang Liu🇨🇳 · Shi-Lin Zhu🇨🇳

   We investigate the newly observed $X(4500)$ and $X(4700)$ based on the diquark-antidiquark configuration within the framework of QCD sum rules. Both of them may be interpreted as the $D$-wave $cs\bar{c}\bar{s}$ tetraquark states of $J^P=0^{+}$, but with opposite color structures, which is remarkably similar to the result obtained in Ref.~\cite{Chen:2010ze} that the $X(4140)$ and $X(4274)$ can be both interpreted as the $S$-wave $cs\bar{c}\bar{s}$ tetraquark states of $J^P=1^{+}$, also with opposite color structures. However, the extracted masses and these suggested assignments to these $X$ states do depend on these running quark masses where $m_s(2\text{mbox}GeV)=95\pm 5$ MeV and $m_c(m_c)=1.23\pm 0.09$ GeV. As a byproduct, the masses of the hidden-bottom partner states of the $X(4500)$ and $X(4700)$ are extracted to be both around 10.64 GeV, which can be searched for in the ${\rm Y}\varphi$ invariant mass distribution.

   ↳ hep-phhep-exhep-latnucl-exEPJC(2017)·71 citations
5. 05*

   HYDRO + JETS (HYDJET++) event generator for Pb+Pb collisions at LHC

   L. Bravina🇳🇴 · B.H. Brusheim Johansson🇳🇴 · J. Crkovská🇫🇷 · G. Eyyubova🇷🇺 · V. Korotkikh🇷🇺 · I. Lokhtin🇷🇺 · L. Malinina🇷🇺 · E. Nazarova🇷🇺 · S. Petrushanko🇷🇺 · A. Snigirev🇷🇺 · E. Zabrodin🇳🇴

   The Monte Carlo event generator HYDJET++ is one of the few generators, designed for the calculations of heavy-ion collisions at ultrarelativistic energies, which combine treatment of soft hydro-like processes with the description of jets traversing the hot and dense partonic medium. The model is employed to study the azimuthal anisotropy phenomena, dihadron angular correlations and event-by-event (EbyE) fluctuations of the anisotropic flow in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. The interplay of soft and hard processes describes the violation of the mass hierarchy of meson and baryon elliptic and triangular flows at p_T > 2 GeV/c, the fall-off of the flow harmonics at intermediate transverse momenta, and the worsening of the number-of-constituent-quark (NCQ) scaling of elliptic/triangular flow at LHC compared to RHIC energies. The cross-talk of v_2 and v_3 leads to emergence of higher order harmonics in the model and to appearance of the ridge structure in dihadron angular correlations in a broad pseudorapidity range. HYDJET++ possesses also the dynamical EbyE fluctuations of the anisotropic flow. The model results agree well with the experimental data.

   ↳ hep-phnucl-exnucl-thJ.Phys.Conf.Ser.(2016)·4 citations
6. 06*

   Broadband Neutron Interferometer

   Dmitry A. Pushin · Dusan Sarenac🇨🇦 · Dan Hussey · Houxun Miao🇨🇳 · Muhammad Arif · David G. Cory🇨🇦 · Michael G. Huber · David Jacobson · Jacob LaManna · Joseph D. Parker · Taken Shinohara · Wakana Ueno · Han Wen

   We demonstrate a two phase-grating, multi-beam neutron interferometer by using a modified Ronchi setup in a far-field regime. The functionality of the interferometer is based on the universal \moire effect that was recently implemented for X-ray phase-contrast imaging in the far-field regime. Interference fringes were achieved with monochromatic, bichromatic, and polychromatic neutron beams; for both continuous and pulsed beams. This far-field neutron interferometry allows for the utilization of the full neutron flux for precise measurements of potential gradients, and expands neutron phase-contrast imaging techniques to more intense polycromatic neutron beams.

   ↳ physics.ins-detnucl-exphysics.opticsquant-phPRA(2017)·14 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.