Nuclear Theory·nucl-th

Tuesday·June 30, 2015

16 papers—11 primary·5 cross-listed

01
Null-test signal for T-invariance violation in $p d$ scattering
Yuriy Uzikov🇷🇺 · Azamat Temerbayev🇰🇿
The integrated proton-deuteron cross section $σ$ for the case of the incident proton vector polarization $p_{y}^{p}$ and tensor polarization $P_{x z}$ of the deuteron target provides a null test signal for time-reversal invariance violating but P-parity conserving (TVPC) effects. We study the null-test observable $σ$ within the Glauber theory of the double-polarized $p d$ scattering. Full spin dependence of the ordinary strong $pN$ scattering amplitudes and different types of the hypothetical TVPC pN-amplitudes are taken into account. We show that the contribution from the exchange of the lowest-mass meson allowed in the TVPC interaction, i.e. the $ρ$ -meson, to the null-test observable $σ$ is zero. The axial $h_{1}$ meson exchange makes a non-zero contribution. We find that inclusion of the Coulomb interaction does not lead to divergence of the cross section $σ$ and calculate its energy dependence at the proton beam energy 100-1000 MeV.
nucl-thPRC(2015)·38 citations
02
Combustion of a hadronic star into a quark star: the turbulent and the diffusive regimes
Alessandro Drago🇮🇹 · Giuseppe Pagliara🇮🇹
We argue that the full conversion of a hadronic star into a quark or a hybrid star occurs within two different regimes separated by a critical value of the density of the hadronic phase $n_{h}$ . The first stage, occurring for $n_{h} > n_{h}$ , is characterized by turbulent combustion and lasts typically a few ms. During this short time-scale neutrino cooling is basically inactive and the star heats up thanks to the heat released in the conversion. In the second stage, occurring for $n_{h} < n_{h}$ , turbulence is not active anymore, and the conversion proceeds on a much longer time scale (of the order of tens of seconds), with a velocity regulated by the diffusion and the production of strange quarks. At the same time, neutrino cooling is also active. The interplay between the heating of the star due to the slow conversion of its outer layers (with densities smaller than $n_{h}$ ) and the neutrino cooling of the forming quark star leads to a quasi-plateau in the neutrino luminosity which, if observed, would possibly represent a unique signature for the existence of quark matter inside compact stars. We will discuss the phenomenological implications of this scenario in particular in connection with the time structure of long gamma-ray-bursts.
nucl-thastro-ph.SRPRC(2015)·42 citations
03
Impact of pairing correlations on the orientation of the nuclear
P. W. Zhao🇺🇸 · S. Q. Zhang🇨🇳 · J. Meng🇨🇳
For the first time, the tilted axis cranking covariant density functional theory with pairing correlations has been formulated and implemented in a fully self-consistent and microscopic way to investigate the evolution of the spin axis and the pairing effects in rotating triaxial nuclei. The measured energy spectrum and transition probabilities for the Nd-135 yrast band are reproduced well without any ad hoc renormalization factors when pairing effects are taken into account. A transition from collective to chiral rotation has been demonstrated. It is found that pairing correlations introduce additional admixtures in the single-particle orbitals, and, thus, influence the structure of tilted axis rotating nuclei by reducing the magnitude of the proton and neutron angular momenta while merging their direction.
nucl-thPRC(2015)·53 citations
04
Analysis of the effect of core structure upon dineutron correlation using antisymmetrized molecular dynamics
Fumiharu Kobayashi · Yoshiko Kanada-En'yo
We extend the method of antisymmetrized molecular dynamics to investigate dineutron correlation. We apply this method to $^{10}$ Be as an example and investigate the motion of two neutrons around a largely deformed $^{8}$ Be core by analyzing the two-neutron overlap function around the core. We show that the core structure plays an important role in dineutron formation and expansion from the core and that the present framework is effective for the studies of dineutron correlation.
nucl-thPRC(2016)·7 citations
05
High $Q^{2}$ behavior of the electromagnetic form factors in the relativistic hypercentral CQM
E. Santopinto🇮🇹 · A. Vassallo🇮🇹 · M.M. Giannini🇮🇹 · M. De Sanctis🇨🇴
The ratio $R_{p}$ between the electric and magnetic proton form factors has been recently measured at JLab up to $Q^{2} = 8.5 G e V^{2}$ . We have extended the calculation of the nucleon form factors with the hypercentral Constituent Quark Model and compared them with the data on $R_{p}$ and on the $Q^{2}$ behavior of the ratio $Q^{2} F_{2} / F_{1}$ . In both cases the theoretical curves agree with the experimental points.
nucl-thPRC(2010)·32 citations
06
The preformation probability inside Alpha-emitters having different ground state spin-parity than daughters
W. M. Seif · M. M. Botros · A. I. Refaie
The ground-state spin and parity of a formed daughter in the radioactive Alpha-emitter is expected to influence the preformation probability of the Alpha and daughter clusters inside it. We investigate the Alpha and daughter preformation probability inside odd-A and doubly-odd radioactive nuclei when the daughter and parent are of different spin and/or parity. We consider only the ground-state to ground-state unfavored decays. This is to extract precise information about the effect of the difference in the ground states spin-parity of the involved nuclei far away any influences from the excitation energy if the decays are coming from isomeric states. The calculations are done for 161 Alpha-emitters, with Z=65-112 and N=84-173, in the framework of the extended cluster model, with WKB penetrability and assault frequency. We used a Hamiltonian energy density scheme based on Skyrme-SLy4 interaction to compute the interaction potential. The Alpha plus cluster preformation probability is extracted from the calculated decay width and the experimental half-life time. We discussed in detailed steps the effect of angular momentum of the emitted Alpha-particle on the various physical quantities involved in the unfavored decay process and how it is finally increases the half-life time. We found that if the ground states spin and/or parity of parent and daughter nuclei are different, then the preformation probability of the Alpha-cluster inside parent is less than it would be if they have similar spin-parity. We modified the formula that gives the Alpha preformation probability in terms of the numbers of protons and neutrons outside the shell closures of parent, to account for this hindrance in the preformation probability for the unfavored decays between ground states.
nucl-thPRC(2015)·55 citations
07
$0 ν β β$ and $2 ν β β$ nuclear matrix elements in the interacting boson model with isospin restoration
J. Barea🇨🇱 · J. Kotila🇺🇸 · F. Iachello🇺🇸
We introduce a method for isospin restoration in the calculation of nuclear matrix elements (NME) for $0 ν β β$ and $2 ν β β$ decay within the framework of interacting boson model (IBM-2). With this method, we calculate NME for all processes of interest in $0 ν β^{-} β^{-}$ , $2 ν β^{-} β^{-}$ , and in $0 ν β^{+} β^{+}$ , $0 ν β^{+} E C^{+}$ , $R 0 ν E C E C$ , $2 ν β^{+} β^{+}$ , $2 ν β^{+} E C$ , and $2 ν E C E C$ . With this method, the Fermi (F) matrix elements for $2 ν β β$ vanish, and those for $0 ν β β$ are considerably reduced.
nucl-thPRC(2015)·413 citations
08
Limits on the neutrino mass from neutrinoless double- $β$ decay
J. Barea🇨🇱 · J. Kotila🇺🇸 · F. Iachello🇺🇸
Neutrinoless double- $β$ decay is of fundamental importance for the determining neutrino mass. By combining a calculation of nuclear matrix elements within the framework of the microscopic interacting boson model (IBM-2) with an improved calculation of phase space factors, we set limits on the average light neutrino mass and on the average inverse heavy neutrino mass (flavor violating parameter).
nucl-thPRL(2012)·162 citations
09
Elastic nucleon form factors
M. De Sanctis🇮🇹 · M.M. Giannini🇮🇹 · E. Santopinto🇮🇹 · A. Vassallo🇮🇹
The relativized hypercentral Constituent Quark Model is used for the calculation of the elastic electromagnetic form factors of the nucleon. The results are compared with the recent measurements at Jlab.
nucl-thNPA(2007)·6 citations
10
Electromagnetic form factors in the Hypercentral Constituent Quark Model
M. De Sanctis🇮🇹 · M.M. Giannini🇮🇹 · E. Santopinto🇮🇹 · A. Vassallo🇮🇹
We discuss the recent experimental results on the ratio bertween the electric and magnetic proton form factors and how they can be described by the hypercentral Constituent Quark Model.
nucl-thNPA(2005)·26 citations
11
Drag induced radiative loss from semi-hard heavy quarks
Raktim Abir🇺🇸 · Abhijit Majumder🇺🇸
The case of gluon bremsstrahlung off a heavy quark in extended nuclear matter is revisited within the higher twist formalism. In particular, the in-medium modification of "semi-hard" heavy quarks is studied, where the momentum of the heavy quark is larger but comparable to the mass of the heavy quark ( $p ≳ M$ ). In contrast to all prior calculations, where the gluon emission spectrum is entirely controlled by the transverse momentum diffusion parameter ( $q^$ ), both for light and heavy quarks, in this work, we demonstrate that the gluon emission spectrum for a heavy quark (unlike that for flavors) is also sensitive to $e^$ , which so far has been used to quantify the amount of light-cone drag experienced by a parton. This mass dependent effect, due to the non-light-like momentum of a semi-hard heavy-quark, leads to an additional energy loss term for heavy-quarks, while resulting in a negligible modification of light flavor (and high energy heavy flavor) loss. This result can be used to estimate the value of this sub-leading non-perturbative jet transport parameter ( $e^$ ) from heavy flavor suppression in ultra-relativistic heavy-ion collisions.
nucl-thhep-phPRC(2016)·33 citations
12
New generation low-energy probes for ultralight axion and scalar dark matter
Yevgeny V. Stadnik🇦🇺 · Victor V. Flambaum🇩🇪
We present a brief overview of a new generation of high-precision laboratory and astrophysical measurements to search for ultralight (sub-eV) axion, axion-like pseudoscalar and scalar dark matter, which form either a coherent condensate or topological defects (solitons). In these new detection methods, the sought effects are linear in the interaction constant between dark matter and ordinary matter, which is in stark contrast to traditional searches for dark matter, where the sought effects are quadratic or higher order in the underlying interaction constants (which are extremely small).
↳ hep-phastro-ph.COnucl-thphysics.atom-phMod.Phys.Lett.A(2017)·17 citations
13
Electromagnetic currents induced by color fields
Naoto Tanji🇩🇪
The quark production in classical color fields is investigated with a focus on the induction of an electromagnetic current by produced quarks. We show that the color SU(2) and the SU(3) theories lead significantly different results for the electromagnetic current. In uniform SU(2) color fields, the net electromagnetic current is not generated, while in SU(3) color fields the net current is induced depending on the color direction of background fields. Also the numerical study of the quark production in inhomogeneous color fields is done. Motivated by gauge field configurations provided by the color glass condensate framework, we introduce an ensemble of randomly distributed color electric fluxtubes. The spectrum of photons emitted from the quarks by a classical process is shown.
↳ hep-phnucl-thPRD(2015)·18 citations
14
Collective neutrino oscillations and spontaneous symmetry breaking
Huaiyu Duan (UNM)🇺🇸
Neutrino oscillations in a hot and dense astrophysical environment such as a core-collapse supernova pose a challenging, seven-dimensional flavor transport problem. To make the problem even more difficult (and interesting), neutrinos can experience collective oscillations through nonlinear refraction in the dense neutrino medium in this environment. Significant progress has been made in the last decade towards the understanding of collective neutrino oscillations in various simplified neutrino gas models with imposed symmetries and reduced dimensions. However, a series of recent studies seem to have "reset" this progress by showing that these models may not be compatible with collective neutrino oscillations because the latter can break the symmetries spontaneously if they are not imposed. We review some of the key concepts of collective neutrino oscillations by using a few simple toy models. We also elucidate the breaking of spatial and directional symmetries in these models because of collective oscillations.
↳ hep-phastro-ph.HEnucl-thIJMPE(2015)·30 citations
15
Energy bursts from deconfinement in high-mass twin stars
D. E. Alvarez-Castillo🇵🇱 · M. Bejger🇵🇱 · D. Blaschke🇵🇱 · P. Haensel🇵🇱 · L. Zdunik🇵🇱
We estimate the energy reservoir available in the deconfinement phase transition induced collapse of a neutron star to its hybrid star mass twin on the "third family" branch, using a recent equation of state of dense matter. The available energy corresponding to the mass-energy difference between configurations is comparable with energies of the most violent astrophysical burst processes. An observational outcome of such a dynamical transition might be fast radio bursts, specifically a recent example of a FRB with a double-peak structure in its light curve.
↳ astro-ph.HEhep-phnucl-th9 citations
16
Evolution of heavy quark distribution function in quark-gluon plasma: using the Iterative Laplace Transform Method
Sharareh Mehrabi Pari🇮🇷 · Kurosh Javidan🇮🇷 · Fatemeh Taghavi Shahri🇮🇷
The "Iterative Laplace Transform Method" is used to solve the Fokker-Planck equation for finding the time evolution of the heavy quarks distribution functions such as charm and bottom in quark gluon plasma. These solutions will lead us to calculation of nuclear suppression factor RAA. The results have good agreement with available experiment data from the PHENIX collaboration.
↳ hep-phnucl-thEPJ Web Conf.(2016)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE