Nuclear Theory·nucl-th

Tuesday·December 19, 2017

24 papers—17 primary·7 cross-listed

18
An exact solution to the Bertsch problem and the non-universality of the Unitary Fermi Gas
E. Ruiz Arriola🇪🇸 · S. Szpigel🇧🇷 · V. S. Timoteo🇧🇷
We analyze the universality of the Unitary Fermi Gas in its ground state from a Wilsonian renormalization point of view and compute the effective range dependence of the Bertsch parameter $ξ$ exactly. To this end we construct an effective block-diagonal two-body separable interaction with the Fermi momentum as a cut-off which reduces the calculation to the mean field level. The interaction is separable in momentum space and is determined by Tabakin's inverse scattering formula. For a vanishing effective range we get $ξ = \frac{176}{9 π} - \frac{17}{3} = 0.56$ . By using phase-equivalent similarity transformations we can show that there is a class of exact solutions with any value in the range $0.56 \geq ξ \geq - 1/3$ .
↳ cond-mat.quant-gashep-phnucl-th2 citations
19
The Impact of Nuclear Reaction Rate Uncertainties On The Evolution of Core-Collapse Supernova Progenitors
C. E. Fields · F. X. Timmes · R. Farmer · I. Petermann · William M. Wolf · S. M. Couch
We explore properties of core-collapse supernova progenitors with respect to the composite uncertainties in the thermonuclear reaction rates by coupling the reaction rate probability density functions provided by the STARLIB reaction rate library with $MESA$ stellar models. We evolve 1000 15 $M_{⊙}$ models from the pre main-sequence to core O-depletion at solar and subsolar metallicities for a total of 2000 Monte Carlo stellar models. For each stellar model, we independently and simultaneously sample 665 thermonuclear reaction rates and use them in a $MESA$ in situ reaction network that follows 127 isotopes from $^{1}$ H to $^{64}$ Zn. With this framework we survey the core mass, burning lifetime, composition, and structural properties at five different evolutionary epochs. At each epoch we measure the probability distribution function of the variations of each property and calculate Spearman Rank-Order Correlation coefficients for each sampled reaction rate to identify which reaction rate has the largest impact on the variations on each property. We find that uncertainties in $^{14}$ N $(p, γ)^{15}$ O, triple- $α$ , $^{12}$ C $(α, γ)^{16}$ O, $^{12}$ C( $^{12}$ C, $p$ ) $^{23}$ Na, $^{12}$ C( $^{16}$ O, $p$ ) $^{27}$ Al, $^{16}$ O( $^{16}$ O, $n$ ) $^{31}$ S, $^{16}$ O( $^{16}$ O, $p$ ) $^{31}$ P, and $^{16}$ O( $^{16}$ O, $α$ ) $^{28}$ Si reaction rates dominate the variations of the properties surveyed. We find that variations induced by uncertainties in nuclear reaction rates grow with each passing phase of evolution, and at core H-, He-depletion are of comparable magnitude to the variations induced by choices of mass resolution and network resolution. However, at core C-, Ne-, and O-depletion, the reaction rate uncertainties can dominate the variation causing uncertainty in various properties of the stellar model in the evolution towards iron core-collapse.
↳ astro-ph.SRastro-ph.HEnucl-exnucl-thAstrophys.J.Suppl.(2018)·34 citations
20
Relativistic corrections to exclusive $χ_{c J} + γ$ production from $e^{+} e^{-}$ annihilation
Nora Brambilla🇩🇪 · Wen Chen🇨🇳 · Yu Jia🇨🇳 · Vladyslav Shtabovenko🇩🇪 · Antonio Vairo🇩🇪
We calculate in the non-relativistic QCD (NRQCD) factorization framework all leading relativistic corrections to the exclusive production of $χ_{c J} + γ$ in $e^{+} e^{-}$ annihilation. In particular, we compute for the first time contributions induced by octet operators with a chromoelectric field. The matching coefficients multiplying production long distance matrix elements (LDMEs) are determined through perturbative matching between QCD and NRQCD at the amplitude level. Technical challenges encountered in the non-relativistic expansion of the QCD amplitudes are discussed in detail. The main source of uncertainty comes from the not so well known LDMEs. Accounting for it, we provide the following estimates for the production cross sections at $s = 10.6 GeV$ : $σ (e^{+} e^{-} \to χ_{c 0} + γ) = (1.3 \pm 0.4) fb$ , $σ (e^{+} e^{-} \to χ_{c 1} + γ) = (15.4 \pm 6.7) fb$ , and $σ (e^{+} e^{-} \to χ_{c 2} + γ) = (4.7 \pm 2.6) fb$ .
↳ hep-phhep-exnucl-thPRD(2018)·22 citations
21
Hydrodynamic Excitations from Chiral Kinetic Theory and the Hydrodynamic Frames
Navid Abbasi🇮🇷 · Kiarash Naderi🇮🇷 · Farid Taghinavaz🇮🇷
In the framework of chiral kinetic theory (CKT), we consider a system of right- and left-handed Weyl fermions out of thermal equilibrium in a homogeneous weak magnetic field. We show that the Lorentz invariance implies a modification in the definition of the momentum current in the phase space, compared to the case in which the system is in global equilibrium. Using this modified momentum current, we derive the linearized conservation equations from the kinetic equation up to second order in the derivative expansion. It turns out that the eigenmodes of these equations, namely the hydrodynamic modes, differ from those obtained from the hydrodynamic in the Landau-Lifshitz (LL) frame at the same order. We show that the modes of the former case may be transformed to the corresponding modes in the latter case by a global boost. The velocity of the boost is proportional to the magnetic field as well as the difference between the right- and left-handed charges susceptibility. We then compute the chiral transport coefficients in a system of non-Abelian chiral fermions in the no-drag frame and by making the above boost, obtain the well-known transport coeffiecients of the system in the LL frame. Finally by using the idea of boost, we reproduce the AdS/CFT result for the chiral drag force exerted on a quark at rest in the rest frame of the fluid, without performing any holographic computations.
↳ hep-thnucl-thJHEP(2018)·10 citations
22
Two Gluon Emission from MHV: Two Particle Correlations and the Deviation from Poisson
A. N. Rasoanaivo🇿🇦 · W. A. Horowitz🇿🇦
We derive the momentum distribution for two soft and collinear gluons emitted from an off-shell quark, modeled by a $q γ \to q g g$ scattering process and computed using the maximal helicity violating (MHV) technique. We find the explicit non-Abelian corrections to the independent emission Poisson distribution in QED and demonstrate the efficiency of the MHV technique in perturbative QCD calculations. The gluonic two particle correlation function is highly suggestive of that measured in high-multiplicity $pp$ and $p A$ collisions, with a tight correlation in angle but broad correlation in rapidity. Further, the autocorrelation generated by the non-Abelian correlation can provide a significant non-hydrodynamical source of $v_{2}$ in these high multiplicity $pp$ and $p A$ collisions. Finally, these two gluon correlations can be used to calibrate Monte Carlo shower codes for a more accurate description of QCD processes in $pp$ collisions.
↳ hep-phnucl-th2 citations
23
Holographic three flavor baryon in the Witten-Sakai-Sugimoto model with the D0-D4 background
Wenhe Cai🇨🇳 · Si-wen Li🇨🇳
With the construction of the Witten-Sakai-Sugimoto model in the D0-D4 background, we systematically investigate the holographic baryon spectrum in the case of three flavors. The background geometry in this model is holographically dual to $U (N_{c})$ Yang-Mills theory in large $N_{c}$ limit involving an excited state with a nonzero $θ$ angle or glue condensate $⟨ Tr F \land F ⟩ = 8 π^{2} N_{c} κ ~$ , which is proportional to the charge density of the smeared D0-branes through a parameter $b$ or $κ ~$ . The classical solution of baryon in this model can be modified by embedding the Belavin-Polyakov-Schwarz-Tyupkin (BPST) instanton and we carry out the quantization of the collective modes with this solution. Then we extend the analysis to include the heavy flavor and find that the heavy meson is always bound in the form of the zero mode of the flavor instanton in strong coupling limit. The mass spectrum of heavy-light baryons in the situation with single- and double-heavy baryon is derived by solving the eigen equation of the quantized collective Hamiltonian. Afterwards we obtain that the constraint of stable baryon states has to be $1 < b < 3$ and the difference in the baryon spectrum becomes smaller as the D0 charge increases. It indicates that quarks or mesons can not form stable baryons if the $θ$ angle or glue condensate is sufficiently large. Our work is an extension of the previous study of this model and also agrees with those conclusions.
↳ hep-thnucl-thEPJC(2018)·5 citations
24
Accessing Quark Helicity through Dihadron Studies
Hrayr H. Matevosyan🇦🇺 · Aram Kotzinian🇦🇲 · Anthony W. Thomas🇦🇺
We present a new proposal to study the helicity-dependent dihadron fragmentation functions (DiFF), which describe the correlations of the longitudinal polarization of a fragmenting quark with the transverse momenta of the produced hadron pair. Recent experimental searches for this DiFF via azimuthal asymmetries in back-to-back hadron pair production in $e^{+} e^{-}$ annihilation by the $BELLE$ Collaboration did not yield a signal. Here we propose a new way to access this DiFF in $e^{+} e^{-}$ annihilation, motivated by the recently recalculated cross section of this reaction, which explains why there was in fact no signal for the $BELLE$ Collaboration to see. In this new approach the azimuthal asymmetry is weighted by the virtual photon's transverse momentum square multiplying sine and cosine functions of difference of azimuthal angles of relative and total momentum for each pair. The integration over the virtual photon's transverse momentum has the effect of separating the convolution between the helicity-dependent DiFFs in the quark and antiquark jets and results in a nonzero collinear expression containing Fourier moments of helicity-dependent DiFFs. A second new measurement is also proposed for two-hadron production in semi-inclusive deep inelastic scattering, where the asymmetry is weighted in a similar way for a single pair. This results in a collinear factorized form of the asymmetry, which includes the quark helicity parton distribution function and the same helicity-dependent DiFF as in $e^{+} e^{-}$ production and will allow us to check the universality of this DiFF.
↳ hep-phhep-exnucl-thPRL(2018)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE

An exact solution to the Bertsch problem and the non-universality of the Unitary Fermi Gas

The Impact of Nuclear Reaction Rate Uncertainties On The Evolution of Core-Collapse Supernova Progenitors

Relativistic corrections to exclusive χcJ​+γ production from e+e− annihilation

Hydrodynamic Excitations from Chiral Kinetic Theory and the Hydrodynamic Frames

Two Gluon Emission from MHV: Two Particle Correlations and the Deviation from Poisson

Holographic three flavor baryon in the Witten-Sakai-Sugimoto model with the D0-D4 background

Accessing Quark Helicity through Dihadron Studies

Affiliations

Relativistic corrections to exclusive $χ_{c J} + γ$ production from $e^{+} e^{-}$ annihilation