Nuclear Theory·nucl-th

Friday·March 20, 2015

10 papers—3 primary·7 cross-listed

04
Supporting the existence of the QCD critical point by compact star observations
David E. Alvarez-Castillo🇷🇺 · David Blaschke🇷🇺
In order to prove the existence of a critical end point (CEP) in the QCD phase diagram it is sufficient to demonstrate that at zero temperature $T = 0$ a first order phase transition exists as a function of the baryochemical potential $μ$ , since it is established knowledge from ab-initio lattice QCD simulations that at $μ = 0$ the transition on the temperature axis is a crossover. We present the argument that the observation of a gap in the mass-radius relationship for compact stars which proves the existence of a so-called third family (aka "mass twins") will imply that the $T = 0$ equation of state of compact star matter exhibits a strong first order transition with a latent heat that satisfies $Δ ϵ / ϵ_{c} > 0.6$ . Since such a strong first order transition under compact star conditions will remain first order when going to symmetric matter, the observation of a disconnected branch (third family) of compact stars in the mass-radius diagram proves the existence of a CEP in QCD. For the equation of state of the twins the quark matter description is based on a QCD-motivated chiral approach with higher-order quark interactions in the Dirac scalar and vector coupling channels. For hadronic matter we select a relativistic mean-field equation of state with density-dependent couplings. Since the nucleons are treated in the quasi-particle framework, an excluded volume has been included for the nuclear equation of state at super-saturation density that takes into account the finite size of the nucleons. Furthermore we show results of a Bayesian analysis (BA) using disjunct M-R constraints for extracting probability measures for cold, dense matter equations of state. This study reveals that measuring the radii of neutron star twins has the potential to support the existence of a first order phase transition for compact star matter.
↳ astro-ph.HEhep-phnucl-thPoS(2015)·6 citations
05
New measurement of the excited states in $^{11}$ B via the elastic resonance scattering of $^{10}$ Be + p
Y. D. Liu · H. W. Wang · Y. G. Ma · X. G. Cao · G. Q. Zhang · D. Q. Fang · M. Lyu · W. B. He · Z. T. Dai · C. Li · C. L. Zhou · S. Q. Ye and 12 other authors
The elastic resonance scattering protons decayed from $^{11}$ B to the ground state of $^{10}$ Be were measured using the thick-target technique in inverse kinematics at the Heavy Ion Research Facility in Lanzhou (HIRFL). The obtained excitation functions were well described by a multichannel R-matrix procedure under the kinematics process assumption of resonant elastic scattering. The excitation energy of the resonant states ranges from 13.0 to 17.0 MeV, and their resonant parameters such as the resonant energy E $_{x}$ , the spin-parity J $^{π}$ , and the proton-decay partial width $Γ_{p}$ were determined from R-matrix fits to the data. Two of these states around E $_{x}$ = 14.55 MeV [J $^{π}$ = (3/2 $^{+}$ , 5/2 $^{+}$ ), $Γ_{p}$ = 475 $\pm$ 80 keV] and E $_{x}$ = 14.74 MeV [J $^{π}$ = 3/2 $^{-}$ , $Γ_{p}$ = 830 $\pm$ 145 keV], and a probably populated state at E $_{x}$ = 16.18 MeV [J $^{π}$ =(1/2 $^{-}$ , 3/2 $^{-}$ ), $Γ_{p}$ $<$ 60 keV], are respectively assigned to the well-known states in $^{11}$ B at 14.34 MeV, 15.29 MeV, and 16.43 MeV. The isospin of these three states were previously determined to be T = 3/2, but discrepancies exist in widths and energies due to the current counting statistics and energy resolution. We have compared these states with previous measurements, and the observation of the possibly populated resonance is discussed.
↳ nucl-exnucl-thPRC(2015)·2 citations
06
Different mechanism of two-proton emission from proton-rich nuclei $^{23}$ Al and $^{22}$ Mg
Y.G. Ma🇨🇳 · D.Q. Fang🇨🇳 · X.Y. Sun🇨🇳 · P. Zhou🇨🇳 · Y. Togano🇯🇵 · N. Aoi🇯🇵 · H. Baba🇯🇵 · X.Z. Cai🇨🇳 · X.G. Cao🇨🇳 · J.G. Chen🇨🇳 · Y. Fu🇨🇳 · W. Guo🇨🇳 and 34 other authors
Two-proton relative momentum ( $q_{pp}$ ) and opening angle ( $θ_{pp}$ ) distributions from the three-body decay of two excited proton-rich nuclei, namely $^{23}$ Al $\to$ p + p + $^{21}$ Na and $^{22}$ Mg $\to$ p + p + $^{20}$ Ne, have been measured with the projectile fragment separator (RIPS) at the RIKEN RI Beam Factory. An evident peak at $q_{pp} \sim 20$ MeV/c as well as a peak in $θ_{pp}$ around 30 $^{\circ}$ are seen in the two-proton break-up channel from a highly-excited $^{22}$ Mg. In contrast, such peaks are absent for the $^{23}$ Al case. It is concluded that the two-proton emission mechanism of excited $^{22}$ Mg is quite different from the $^{23}$ Al case, with the former having a favorable diproton emission component at a highly excited state and the latter dominated by the sequential decay process.
↳ nucl-exnucl-thPLB(2015)·41 citations
07
Quantum Field Theoretic Treatment of Pion Production via Proton Synchrotron Radiation in Strong Magnetic Fields: Effects of Landau Levels
Tomoyuki Maruyama🇯🇵 · Myung-Ki Cheoun🇰🇷 · Toshitaka Kajino🇯🇵 · Yongshin Kwon🇰🇷 · Grant J. Mathews🇺🇸 · Chung-Yeol Ryu🇰🇷
We study pion production from proton synchrotron radiation in the presence of strong magnetic fields. We derive the exact proton propagator from the Dirac equation in a strong magnetic field by explicitly including the anomalous magnetic moment. In this exact quantum-field approach the magnitude of pion synchrotron emission turns out to be much smaller than that obtained in the semi-classical approach. However, we also find that the anomalous magnetic moment of the proton greatly enhances the production rate about by two order magnitude.
↳ astro-ph.HEhep-phnucl-thPRD(2015)·17 citations
08
Light Quarkonium - Glueball Mixing from a Holographic QCD
Takashi Yamaguchi🇯🇵 · Shinya Matsuzaki🇯🇵
We study the mixing structure of isospin-singlet scalars, the light quarkonium $(q ˉ q)$ and glueball $(g g)$ in two-flavor QCD, based on a holographic model of bottom-up hard-wall type. In the model the pure quarkonium and glueball states are unambiguously defined in terms of the different $U (1)_{A}$ charges in the restoration limit of the chiral $U (2)_{L} \times U (2)_{R}$ symmetry, in which the quarkonium gets massless as the chiral partner of the pion. Hence the $q ˉ q$ - $g g$ mixing arises in the presence of the nonzero chiral condensate or pion decay constant. At the realistic point where the pion decay constant and other hadron masses reach the observed amount, we predict the tiny mixing between the lightest quarkonia and glueball: The smallness of the mixing is understood by the slightly small ratio of the chiral and gluon condensate scales. The low-lying two scalar masses are calculated to be $≃ 1.25$ GeV and $≃ 1.77$ GeV, which are compared with masses of $f_{0} (1370)$ and $f_{0} (1710)$ . Our result implies that $f_{0} (1710)$ predominantly consists of glueball.
↳ hep-phhep-latnucl-thPRD(2015)·1 citation
09
Evidence for $Δ (2200) 7/ 2^{-}$ from photoproduction and consequence for chiral-symmetry restoration at high mass
A.V. Anisovich🇩🇪 · V. Burkert🇺🇸 · J. Hartmann🇩🇪 · E. Klempt🇩🇪 · V.A. Nikonov🇩🇪 · E. Pasyuk🇺🇸 · A.V. Sarantsev🇩🇪 · S. Strauch🇺🇸 · U. Thoma🇩🇪
We report a partial-wave analysis of new data on the double-polarization variable $E$ for the reactions $γ p \to π^{+} n$ and $γ p \to π^{0} p$ and of further data published earlier. The analysis within the Bonn-Gatchina (BnGa) formalism reveals evidence for a poorly known baryon resonance, the one-star $Δ (2200) 7/ 2^{-}$ . This is the lowest-mass $Δ^{*}$ resonance with spin-parity $J^{P} = 7/ 2^{-}$ . Its mass is significantly higher than the mass of its parity partner $Δ (1950) 7/ 2^{+}$ which is the lowest-mass $Δ^{*}$ resonance with spin-parity $J^{P} = 7/ 2^{+}$ . It has been suggested that chiral symmetry might be restored in the high-mass region of hadron excitations, and that these two resonances should be degenerate in mass. Our findings are in conflict with this prediction.
↳ nucl-exnucl-thPLB(2017)·32 citations
10
Broad resonances and beta-decay
K. Riisager · H.O.U. Fynbo · S. Hyldegaard · A.S. Jensen
Beta-decay into broad resonances gives a distorted lineshape in the observed energy spectrum. Part of the distortion arises from the phase space factor, but we show that the beta-decay matrix element may also contribute. Based on a schematic model for p-wave continuum neutron states it is argued that beta-decay directly to the continuum should be considered as a possible contributing mechanism in many decays close to the driplines. The signatures in R-matrix fits for such decays directly to continuum states are discussed and illustrated through an analysis of the beta-decay of $^{8}$ B into $2^{+}$ states in $^{8}$ Be.
↳ nucl-exnucl-thNPA(2015)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE

Supporting the existence of the QCD critical point by compact star observations

New measurement of the excited states in 11B via the elastic resonance scattering of 10Be + p

Different mechanism of two-proton emission from proton-rich nuclei 23Al and 22Mg

Quantum Field Theoretic Treatment of Pion Production via Proton Synchrotron Radiation in Strong Magnetic Fields: Effects of Landau Levels

Light Quarkonium - Glueball Mixing from a Holographic QCD

Evidence for Δ(2200)7/2− from photoproduction and consequence for chiral-symmetry restoration at high mass

Broad resonances and beta-decay

Affiliations

New measurement of the excited states in $^{11}$ B via the elastic resonance scattering of $^{10}$ Be + p

Different mechanism of two-proton emission from proton-rich nuclei $^{23}$ Al and $^{22}$ Mg

Evidence for $Δ (2200) 7/ 2^{-}$ from photoproduction and consequence for chiral-symmetry restoration at high mass