Nuclear Theory·nucl-th

Wednesday·October 19, 2016

8 papers—1 primary·7 cross-listed

02
Coupled-channel Dalitz plot analysis of $D^{+} \to K^{-} π^{+} π^{+}$ decay
Satoshi X. Nakamura (Osaka Univ.)🇯🇵
We demonstrate that partial wave amplitudes extracted from $D^{+} \to K^{-} π^{+} π^{+}$ Dalitz plot with a unitary coupled-channel model are significantly different from those obtained with an isobar model. The unitary coupled-channel model takes account of hadronic rescattering mechanisms involving all three mesons that have been missed in conventioanl isobar model analyses. The rescattering mechanisms contribute largely, and can triplicate the $D^{+} \to K^{-} π^{+} π^{+}$ decay width within our analysis. These findings deliver a warning that analysis results obtained with isobar models should be looked with a caution. The determination of the CKM angle $γ / ϕ_{3}$ is a highly relevant problem.
↳ hep-phhep-exnucl-thPoS(2016)·0 citations
03
Towards an automated tool to evaluate the impact of the nuclear modification of the gluon density on quarkonium, D and B meson production in proton-nucleus collisions
Jean-Philippe Lansberg🇫🇷 · Hua-Sheng Shao🇨🇭
We propose a simple and model-independent procedure to account for the impact of the nuclear modification of the gluon density as encoded in nuclear collinear PDF sets on two-to-two partonic hard processes in proton-nucleus collisions. This applies to a good approximation to quarkonium, D and B meson production, generically referred to H. Our procedure consists in parametrising the square of the parton scattering amplitude, A_{gg -> H X} and constraining it from the proton-proton data. Doing so, we have been able to compute the corresponding nuclear modification factors for J/psi, Upsilon and D^0 as a function of y and P_T at sqrt(s_NN)=5 and 8 TeV in the kinematics of the various LHC experiments in a model independent way. It is of course justified since the most important ingredient in such evaluations is the probability of each kinematical configuration. Our computations for D mesons can also be extended to B meson production. To further illustrate the potentiality of the tool, we provide --for the first time-- predictions for the nuclear modification factor for eta_c production in pPb collisions at the LHC.
↳ hep-phhep-exnucl-exnucl-thEPJC(2017)·644 citations
04
Pseudo Nambu-Goldstone modes in neutron stars
Toru Kojo🇨🇳
If quarks and gluons are either gapped or confined in neutron stars (NSs), the most relevant light modes are Nambu-Goldstone (NG) modes. We study NG modes within a schematic quark model whose parameters at high density are constrained by the two-solar mass constraint. Our model has the color-flavor-locked phase at high density, with the effective couplings as strong as in hadron physics. We find that strong coupling effects make NG modes more massive than in weak coupling predictions, and would erase several phenomena caused by the stressed pairings in mismatched Fermi surfaces. For instance, we found that charged kaons, which are dominated by diquark and anti-diquark components, are not light enough to condense at strong coupling. Implications for gravitational wave signals for NS-NS mergers are also briefly discussed.
↳ hep-phastro-ph.HEnucl-thPLB(2017)·6 citations
05
Monte Carlo Implementation of Polarized Hadronization
Hrayr H. Matevosyan🇦🇺 · Aram Kotzinian🇦🇲 · Anthony W. Thomas🇦🇺
We study the polarized quark hadronization in a Monte Carlo (MC) framework based on the recent extension of the quark-jet framework, where a self-consistent treatment of the quark polarization transfer in a sequential hadronization picture has been presented. Here, we first adopt this approach for MC simulations of hadronization process with finite number of produced hadrons, expressing the relevant probabilities in terms of the eight leading twist quark-to-quark transverse momentum dependent (TMD) splitting functions (SFs) for elementary $q \to q^{'} + h$ transition. We present explicit expressions for the unpolarized and Collins fragmentation functions (FFs) of unpolarized hadrons emitted at rank two. Further, we demonstrate that all the current spectator-type model calculations of the leading twist quark-to-quark TMD SFs violate the positivity constraints, and propose quark model based ansatz for these input functions that circumvents the problem. We validate our MC framework by explicitly proving the absence of unphysical azimuthal modulations of the computed polarized FFs, and by precisely reproducing the earlier derived explicit results for rank two pions. Finally, we present the full results for pion unpolarized and Collins FFs, as well as the corresponding analyzing powers from high statistics MC simulations with a large number of produced hadrons for two different model input elementary SFs. The results for both sets of input functions exhibit the same general features of opposite signed Collins function for favored and unfavored channels at large $z$ , and at the same time demonstrate the flexibility of the quark-jet framework by producing significantly different dependences of the results at mid- to low- $z$ for the two model inputs.
↳ hep-phhep-exnucl-thPRD(2017)·15 citations
06
Production and Distribution of $^{44}$ Ti and $^{56}$ Ni in a Three-dimensional Supernova Model Resembling Cassiopeia A
A. Wongwathanarat (1,2)🇯🇵 · H.-Th. Janka (2)🇩🇪 · E. Mueller (2)🇩🇪 · E. Pllumbi (2,3)🇩🇪 · S. Wanajo (4,5) ((1) RIKEN, ABB Lab, (2) MPI Astrophysics, (3) Physik Dept., TUM, (4) RIKEN, iTHES Research Group)🇯🇵
The spatial and velocity distributions of nuclear species synthesized in the innermost regions of core-collapse supernovae can yield important clues about explosion asymmetries and the operation of the still disputed explosion mechanism. Recent observations of radioactive $^{44}$ Ti with high-energy satellite telescopes (Nuclear Spectroscopic Telescope Array [NuSTAR], INTEGRAL) have measured gamma-ray line details, which provide direct evidence of large-scale explosion asymmetries in SN 1987A and in Cassiopeia A (Cas A) even by mapping of the spatial brightness distribution (NuSTAR). Here we discuss a 3D simulation of a neutrino-driven explosion, using a parameterized neutrino engine, whose $^{44}$ Ti distribution is mostly concentrated in one hemisphere pointing opposite to the neutron star (NS) kick velocity. Both exhibit intriguing resemblance to the observed morphology of the Cas A remnant, although neither the progenitor nor the explosion was fine-tuned for a perfect match. Our results demonstrate that the asymmetries observed in this remnant can, in principle, be accounted for by a neutrino-driven explosion, and that the high $^{44}$ Ti abundance in Cas A may be explained without invoking rapid rotation or a jet-driven explosion, because neutrino-driven explosions generically eject large amounts of high-entropy matter. The recoil acceleration of the NS is connected to mass ejection asymmetries and is opposite to the direction of the stronger explosion, fully compatible with the gravitational tugboat mechanism. Our results also imply that Cas A and SN 1987A could possess similarly "one-sided" Ti and Fe asymmetries, with the difference that Cas A is viewed from a direction with large inclination angle to the NS motion, whereas the NS in SN 1987A should have a dominant velocity component pointing toward us.
↳ astro-ph.HEastro-ph.SRhep-phnucl-thApJ(2017)·166 citations
07
Pion Electromagnetic Form Factor at Lower and Higher Momentum Transfer
J. P. B. C. de Melo🇧🇷 · Rômulo Moreira Moita🇧🇷 · Kazuo Tsushima (Laboratório de Física Teórica e Computacional, LFTC, Universidade Cruzeiro do Sul)🇧🇷
The pion electromagnetic form factor is calculated at lower and higher momentum transfer in order to explore constituent quark models and the differences among those models. In particular, the light-front constituent quark model is utilized here to calculate the pion electromagnetic form factor at lower and higher energies. The matrix elements of the electromagnetic current, are calculated with both "plus" and "minus" components of the electromagnetic current in the light-front. Further, the electromagnetic form factor is compared with other models in the literature and experimental data.
↳ hep-phhep-exnucl-th1 citation
08
Metastable pions in dense media
Marcelo Loewe🇨🇱 · Alfredo Raya🇲🇽 · Cristian Villavicencio🇨🇱
We study the leptonic decay of charged pions in a compact star environment. Considering leptons as a degenerated Fermi system, pions are tightly constrained to decay into these particles because their Fermi levels are occupied. Thus, pion decay is only possible through thermal fluctuations. Under these circumstances, pion lifetime is larger and hence can be considered to reach a metastable state. We explore restrictions under which such a metastability is possible. We also study conditions under which pions and leptons already in chemical equilibrium can reach simultaneously the thermal equilibrium, and obtain the neutrino emissivity from metastable pions. Scenarios that favor this metastable state are protoneutron stars.
↳ hep-phastro-ph.HEnucl-thPRD(2017)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE

Coupled-channel Dalitz plot analysis of D+→K−π+π+ decay

Towards an automated tool to evaluate the impact of the nuclear modification of the gluon density on quarkonium, D and B meson production in proton-nucleus collisions

Pseudo Nambu-Goldstone modes in neutron stars

Monte Carlo Implementation of Polarized Hadronization

Production and Distribution of 44Ti and 56Ni in a Three-dimensional Supernova Model Resembling Cassiopeia A

Pion Electromagnetic Form Factor at Lower and Higher Momentum Transfer

Metastable pions in dense media

Affiliations

Coupled-channel Dalitz plot analysis of $D^{+} \to K^{-} π^{+} π^{+}$ decay

Production and Distribution of $^{44}$ Ti and $^{56}$ Ni in a Three-dimensional Supernova Model Resembling Cassiopeia A