Fri·May 25, 2018Friday·May 25, 2018

1. 01*

   The Role of Tensor Force in Heavy-Ion Fusion Dynamics

   Lu Guo🇨🇳 · Cedric Simenel🇦🇺 · Long Shi · Chong Yu

   The tensor force is implemented into the time-dependent Hartree-Fock (TDHF) theory so that both exotic and stable collision partners, as well as their dynamics in heavy-ion fusion, can be described microscopically. The role of tensor force on fusion dynamics is systematically investigated for ${}^{40}\mathrm{Ca}+{}^{40}\mathrm{Ca}$, ${}^{40}\mathrm{Ca}+{}^{48}\mathrm{Ca}$, ${}^{48}\mathrm{Ca}+{}^{48}\mathrm{Ca}$, ${}^{48}\mathrm{Ca}+{}^{56}\mathrm{Ni}$, and ${}^{56}\mathrm{Ni}+{}^{56}\mathrm{Ni}$ reactions which vary by the total number of spin-unsaturated magic numbers in target and projectile. A notable effect on fusion barriers and cross sections is observed by the inclusion of tensor force. The origin of this effect is analyzed. The influence of isoscalar and isovector tensor terms is investigated with the T$IJ$ forces. These effects of tensor force in fusion dynamics are essentially attributed to the shift of low-lying vibration states of colliding partners and nucleon transfer in the asymmetric reactions. Our calculations of above-barrier fusion cross sections also show that tensor force does not significantly affect the dynamical dissipation at near-barrier energies.

   ↳ nucl-thnucl-exPLB(2018)·54 citations
2. 02*

   The cathode tube effect: heavy quarks probing the Glasma in p-Pb collisions

   Marco Ruggieri🇨🇳 · Santosh K. Das🇨🇳

   We study the propagation of charm quarks in the early stage of high energy proton-lead collision, considering the interaction of these quarks with the evolving Glasma by means of the Wong equations. Neglecting quantum fluctuations at the initial time the Glasma is made of longitudinal fields, but the dynamics leads to a quick formation of transverse fields; we estimate such a formation time as $\Delta t\approx 0.1$ fm/c which is of the same order of the formation time of heavy quark pairs $t_{\mathrm{formation}}\approx 1/(2m)$. Limiting ourselves to the simple case of a static longitudinal geometry, we find that heavy quarks are accelerated by the strong transverse color fields in the early stage and this leads to a tilting of the $c-$quarks spectrum towards higher $p_T$ states. This average acceleration can be understood in terms of drag and diffusion of $c-$quarks in a hot medium and appears to be similar to the one felt by the electrons ejected by the electron cannon in a cathode tube: we dub this effect as {\it cathode tube effect}. The tilting of the spectrum affects the nuclear modification factor, $R_{\mathrm{pPb}}$, suppressing this below one at low $p_T$ and making it larger than one at intermediate $p_T$. We compute $R_{\mathrm{pPb}}(p_T)$ after the evolution of charm quarks in the gluon fields and we find that its shape is in qualitative agreement with the measurements of the same quantity for $D-$mesons in proton-lead collisions.

   ↳ nucl-thhep-phnucl-exPRD(2018)·55 citations
3. 03*

   Gauge Properties of Hadronic Structure of Nucleon in Neutron Radiative Beta Decay to Order O(alpha/pi) in Standard V - A Effective Theory with QED and Linear Sigma Model of Strong Low--Energy Interactions

   A. N. Ivanov🇦🇹 · R. Höllwieser🇦🇹 · N. I. Troitskaya🇦🇹 · M. Wellenzohn🇦🇹 · Ya. A. Berdnikov🇷🇺

   Within the standard V - A theory of weak interactions, Quantum Electrodynamics (QED) and the linear sigma-model (LsM) of strong low-energy hadronic interactions we analyse gauge properties of hadronic structure of the neutron and proton in the neutron radiative beta-decay. We show that the Feynman diagrams, describing contributions of hadronic structure to the amplitude of the neutron radiative beta-decay in the tree-approximation for strong low-energy interactions in the LsM, are gauge invariant. In turn, the complete set of Feynman diagrams, describing the contributions of hadron-photon interactions in the one-hadron-loop approximation, is not gauge invariant. In the infinite limit of the scalar sigma-meson, reproducing the current algebra results (Weinberg, Phys. Rev. Lett. 18, 188 (1967)), and to leading order in the large nucleon mass expansion the Feynman diagrams, violating gauge invariance, do not contribute to the amplitude of the neutron radiative beta-decay in agreement with Sirlin's analysis of strong low-energy interactions in neutron beta decays. We assert that the problem of appearance of gauge non-invariant Feynman diagrams of hadronic structure of the neutron and proton is related to the following. The vertex of the effective V-A weak interactions does not belong to the combined quantum field theory including the LsM and QED. We argue that gauge invariant set of Feynman diagrams of hadrons, coupled to real and virtual photons in neutron beta decays, can be obtained within the combined quantum field theory including the Standard Electroweak Model (SEM) and the LsM, where the effective V-A vertex of weak interactions is a result of the W^- - electroweak boson exchange.

   ↳ hep-phgr-qcnucl-exInt.J.Mod.Phys.A(2018)·8 citations
4. 04*

   Longitudinal Double-Spin Asymmetries for Dijet Production at Intermediate Pseudorapidity in Polarized $pp$ Collisions at $\sqrt{s}$ = 200 GeV

   J. Adam🇺🇸 · L. Adamczyk🇵🇱 · J. R. Adams🇺🇸 · J. K. Adkins🇺🇸 · G. Agakishiev🇷🇺 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · N. N. Ajitanand🇺🇸 · I. Alekseev🇷🇺 · D. M. Anderson🇺🇸 · R. Aoyama🇯🇵 · A. Aparin🇷🇺 and 337 other authors

   We present the first measurements of the longitudinal double-spin asymmetry $A_{LL}$ for dijets with at least one jet reconstructed within the pseudorapidity range $0.8<\eta <1.8$. The dijets were measured in polarized $pp$ collisions at a center-of-mass energy $\sqrt{s}$ = 200 GeV. Values for $A_{LL}$ are determined for several distinct event topologies, defined by the jet pseudorapidities, and span a range of parton momentum fraction $x$ down to $x\sim$ 0.01. The measured asymmetries are found to be consistent with the predictions of global analyses that incorporate the results of previous RHIC measurements. They will provide new constraints on $\Delta g(x)$ in this poorly constrained region when included in future global analyses.

   ↳ hep-exnucl-exPRD(2018)·44 citations
5. 05*

   Longitudinal Double-Spin Asymmetries for ${\pi }^0$s in the Forward Direction for 510 GeV Polarized $pp$ Collisions

   J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · N. N. Ajitanand · I. Alekseev · D. M. Anderson · R. Aoyama · A. Aparin and 337 other authors

   The STAR Collaboration reports measurements of the longitudinal double-spin asymmetry, $A_{LL}$, for neutral pions produced at forward directions in polarized proton-proton collisions, at a center-of-mass energy of $510$ GeV. Results are given for transverse momenta in the range $2<p_T<10$ GeV/$c$ within two regions of pseudorapidity that span $2.65<\eta <3.9$. These results are sensitive to the polarized gluon parton distribution function, $\Delta g(x)$, down to the region of Bjorken $x\sim 10^{-3}$. The asymmetries observed are less than $\pm 5\cdot 10^{-3}$ in magnitude, and will help constrain the contribution to the spin of the proton from polarized gluons at low $x$, when combined with other measurements as part of a global analysis.

   ↳ hep-exnucl-exPRD(2018)·35 citations
6. 06*

   Quarkonium radiative decays from the hadronic Paschen-Back effect

   Sachio Iwasaki🇯🇵 · Kei Suzuki🇯🇵

   We study the radiative (E1 and M1) decays of P-wave quarkonia in a strong magnetic field based on the Lagrangian of potential nonrelativistic QCD. To investigate their properties, we implement a polarized wave function basis justified in the Paschen-Back limit. In a magnetic field stronger than the spin-orbit coupling, the wave functions of the P-wave quarkonia are drastically deformed by the Hadronic Paschen-Back effect. Such deformation leads to the anisotropy of the direction of decays from the P-wave quarkonia. The analytic formulas for the radiative decay widths in the nonrelativistic limit are shown, and the qualitative decay properties are discussed.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2018)·13 citations
7. 07*

   Calculation of francium hyperfine anomaly

   E.A. Konovalova🇷🇺 · Yu.A. Demidov🇷🇺 · M.G. Kozlov🇷🇺 · A.E. Barzakh🇷🇺

   The Dirac-Hartree-Fock plus many-body perturbation theory (DHF+MBPT) method has been used to calculate hyperfine structure constants for Fr. Calculated hyperfine structure anomaly for hydrogen-like ion has been shown to be in good agreement with analytical expressions. It has been shown that the ratio of the anomalies for $s$ and $p_{1/2}$ states is weakly dependent on the principal quantum number. Finally, we estimate Bohr--Weisskopf corrections for several Fr isotopes. Our results may be used to improve experimental accuracy for the nuclear $g$ factors of short-lived isotopes.

   ↳ physics.atom-phnucl-exnucl-thAtoms(2018)·11 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.