Nuclear Theory·nucl-th

Tuesday·March 3, 2015

15 papers—6 primary·9 cross-listed

01
Neutral current quasielastic (anti)neutrino scattering beyond the Fermi gas model at MiniBooNE and BNL kinematics
M.V. Ivanov🇪🇸 · A.N. Antonov🇧🇬 · M.B. Barbaro🇮🇹 · C. Giusti🇮🇹 · A. Meucci🇮🇹 · J.A. Caballero🇪🇸 · R. Gonzalez-Jimenez🇪🇸 · E. Moya de Guerra🇪🇸 · J.M. Udias🇪🇸
Neutral current quasielastic (anti)neutrino scattering cross sections on a $^{12}$ C target are analyzed using a realistic spectral function $S (p, E)$ that gives a scaling function in accordance with the ( $e, e^{'}$ ) scattering data. The spectral function accounts for the nucleon-nucleon (NN) correlations by using natural orbitals (NOs) from the Jastrow correlation method and has a realistic energy dependence. The standard value of the axial mass $M_{A} = 1.032$ GeV is used in all calculations. The role of the final-state interaction (FSI) on the spectral and scaling functions, as well as on the cross sections is accounted for. A comparison of the calculations with the empirical data of the MiniBooNE and BNL experiments is performed. Our results are analyzed in comparison with those when NN correlations are not included, and also with results from other theoretical approaches, such as the relativistic Fermi gas (RFG), the relativistic mean field (RMF), the relativistic Green's function (RGF), as well as with the SuperScaling Approach (SuSA) based on the analysis of quasielastic electron scattering.
nucl-thPRC(2015)·17 citations
02
Neutron-proton effective mass splitting in neutron-rich matter and its impacts on nuclear reactions
Bao-An Li🇺🇸 · Lie-Wen Chen🇨🇳
The neutron-proton effective mass splitting in neutron-rich nucleonic matter reflects the space-time nonlocality of the isovector nuclear interaction. It affects the neutron/proton ratio during the earlier evolution of the Universe, cooling of protoneutron stars, structure of rare isotopes and dynamics of heavy-ion collisions. While there is still no consensus on whether the neutron-proton effective mass splitting is negative, zero or positive and how it depends on the density as well as the isospin-asymmetry of the medium, significant progress has been made in recent yeas in addressing these issues. We first recall the connections among the neutron-proton effective mass splitting, the momentum dependence of the isovector potential and the density dependence of the symmetry energy. We then make a few observations about the progress in calculating the neutron-proton effective mass splitting using various nuclear many-body theories and its effects on the isospin-dependence of in-medium nucleon-nucleon cross sections. Perhaps, our most reliable knowledge so far about the neutron-proton effective mass splitting at saturation density of nuclear matter comes from optical model analyses of huge sets of nucleon-nucleus scattering data accumulated over the last five decades. The momentum dependence of the symmetry potential from these analyses provide a useful boundary condition at saturation density for calibrating nuclear many-body calculations. Several observables in heavy-ion collisions have been identified as sensitive probes of the neutron-proton effective mass splitting in dense neutron-rich matter based on transport model simulations. We review these observables and comment on the latest experimental findings.
nucl-thastro-ph.SRnucl-exMod.Phys.Lett.A(2015)·32 citations
03
Hydrodynamic modeling of 3He-Au collisions at sqrt(sNN)=200 GeV
Piotr Bozek🇵🇱 · Wojciech Broniowski🇵🇱
Collective flow and femtoscopy in ultrarelativistic 3He-Au collisions are investigated within the 3+1-dimensional (3+1D) viscous event-by-event hydrodynamics. We evaluate elliptic and triangular flow coefficients as functions of the transverse momentum. We find the typical long-range ridge structures in the two-particle correlations in the relative azimuth and pseudorapidity, in the pseudorapidity directions of both Au and 3He. We also make predictions for the pionic interferometric radii, which decrease with the transverse momentum of the pion pair. All features found hint on collectivity of the dynamics of the system formed in 3He-Au collisions, with hydrodynamics leading to quantitative agreement with the up-to-now released data.
nucl-thnucl-exPLB(2015)·29 citations
04
Constraining supernova equations of state with equilibrium constants from heavy-ion collisions
Matthias Hempel🇨🇭 · Kris Hagel🇺🇸 · Joseph Natowitz🇺🇸 · Gerd Röpke🇩🇪 · Stefan Typel🇩🇪
Cluster formation is a fundamental aspect of the equation of state (EOS) of warm and dense nuclear matter such as can be found in supernovae (SNe). Similar matter can be studied in heavy-ion collisions (HIC). We use the experimental data of Qin et al. [Phys. Rev. Lett. 108, 172701 (2012)] to test calculations of cluster formation and the role of in-medium modifications of cluster properties in SN EOSs. For the comparison between theory and experiment we use chemical equilibrium constants as the main observables. This reduces some of the systematic uncertainties and allows deviations from ideal gas behavior to be identified clearly. In the analysis, we carefully account for the differences between matter in SNe and HICs. We find that, at the lowest densities, the experiment and all theoretical models are consistent with the ideal gas behavior. At higher densities ideal behavior is clearly ruled out and interaction effects have to be considered. The contributions of continuum correlations are of relevance in the virial expansion and remain a difficult problem to solve at higher densities. We conclude that at the densities and temperatures discussed mean-field interactions of nucleons, inclusion of all relevant light clusters, and a suppression mechanism of clusters at high densities have to be incorporated in the SN EOS.
nucl-thastro-ph.SRnucl-exPRC(2015)·56 citations
05
The domain of validity of fluid dynamics and the onset of cavitation in ultrarelativistic heavy ion collisions
Gabriel S. Denicol🇨🇦 · Charles Gale🇨🇦 · Sangyong Jeon🇨🇦
If the bulk viscosity of QCD matter is large, the effective pressure of the hot and dense matter created in ultrarelativistic heavy ion collisions can become negative, leading to instabilities in the evolution of the plasma. In the context of heavy ion collisions, this effect is sometimes referred to as cavitation. In this contribution we discuss the onset of cavitation in event-by-event hydrodynamic simulations of ultrarelativistic heavy ion collisions at LHC energies. We estimate how large the bulk viscosity of the QGP has to be in the QCD (pseudo) phase transition region in order for the effective pressure of the system to actually become negative.
nucl-thhep-phPoS(2015)·18 citations
06
Toward relativistic mean-field description of $N ˉ$ -nucleus reactions
T. Gaitanos🇬🇷 · M. Kaskulov🇩🇪
In this work we study the antinucleon-nucleus optical potential in the framework of the non-linear derivative (NLD) model with momentum dependent mean-fields. We apply the NLD model to interaction of antinucleons ( $N ˉ$ ) in nuclear matter and, in particular, to antiproton scattering on nuclei. In nuclear matter a strong suppression of the $N ˉ$ -optical potential at rest and at high kinetic energies is found and caused by the momentum dependence of relativistic mean-fields. The NLD results are consistent with known empirical $N ˉ$ -nucleus observations and agree well with antiproton-nucleus scattering data. This makes the NLD approach compatible with both, nucleon and antinucleon Dirac phenomenologies. Furthermore, in nuclear matter an effective mass splitting between nucleons and antinucleons is predicted.
nucl-thNPA(2015)·29 citations
07
Effect of event selection on jetlike correlation measurement in $d$ +Au collisions at $s_{NN} = 200$ GeV
STAR Collaboration: L. Adamczyk🇵🇱 · J. K. Adkins🇺🇸 · G. Agakishiev🇷🇺 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · I. Alekseev🇷🇺 · J. Alford🇺🇸 · A. Aparin🇷🇺 · D. Arkhipkin🇺🇸 · E. C. Aschenauer🇺🇸 · G. S. Averichev🇷🇺 · A. Banerjee🇮🇳 and 320 other authors
Dihadron correlations are analyzed in $s_{_{NN}} = 200$ GeV $d$ +Au collisions classified by forward charged particle multiplicity and zero-degree neutral energy in the Au-beam direction. It is found that the jetlike correlated yield increases with the event multiplicity. After taking into account this dependence, the non-jet contribution on the away side is minimal, leaving little room for a back-to-back ridge in these collisions.
↳ nucl-exnucl-thPLB(2015)·42 citations
08
Real-Time Dynamics of an Impurity in an Ideal Bose Gas in a Trap
A. G. Volosniev · H.-W. Hammer · N. T. Zinner
We investigate the behavior of a harmonically trapped system consisting of an impurity in a dilute ideal Bose gas after the boson-impurity interaction is suddenly switched on. As theoretical framework, we use a field theory approach in the space-time domain within the T-matrix approximation. We establish the form of the corresponding T-matrix and address the dynamical properties of the system. As a numerical application, we consider a simple system of a weakly interacting impurity in one dimension where the interaction leads to oscillations of the impurity density. Moreover, we show that the amplitude of the oscillations can be driven by periodically switching the interaction on and off.
↳ cond-mat.quant-gasnucl-thquant-phPRA(2015)·47 citations
09
Collisions in Chiral Kinetic Theory
Jing-Yuan Chen🇺🇸 · Dam T. Son🇺🇸 · Mikhail A. Stephanov🇺🇸
Using a covariant formalism, we construct a chiral kinetic theory Lorentz invariant to order $O (ℏ)$ which includes collisions. We find a new contribution to the particle number current due to the side jumps required by the conservation of angular momentum during collisions. We also find a conserved symmetric stress-energy tensor as well as the $H$ -function obeying Boltzmann's $H$ -theorem. We demonstrate their use by finding a general equilibrium solution and the values of the anomalous transport coefficients characterizing chiral vortical effect.
↳ hep-thcond-mat.mes-hallnucl-thPRL(2015)·171 citations
10
The Higgs Transverse Momentum Distribution at NNLL and its Theoretical Errors
Duff Neill🇺🇸 · Ira Z. Rothstein🇺🇸 · Varun Vaidya🇺🇸
In this letter, we present the NNLL-NNLO transverse momentum Higgs distribution arising from gluon fusion. In the regime $p_{⊥} ≪ m_{H}$ we include the resummation of the large logs at next to next-to leading order and then match on to the $α_{s}^{2}$ fixed order result near $p_{⊥} \sim m_{h}$ . By utilizing the rapidity renormalization group (RRG) we are able to smoothly match between the resummed, small $p_{⊥}$ regime and the fixed order regime. We give a detailed discussion of the scale dependence of the result including an analysis of the rapidity scale dependence. Our central value differs from previous results, in the transition region as well as the tail, by an amount which is outside the error band. This difference is due to the fact that the RRG profile allows us to smoothly turn off the resummation.
↳ hep-phhep-thnucl-thJHEP(2015)·70 citations
11
Deconfinement Transition at High Isospin Chemical Potential and Low Temperature
Thomas D. Cohen🇺🇸 · Srimoyee Sen🇺🇸
We consider QCD with two degenerate flavors of light quarks(up and down) at asymptotically high isospin chemical potential with zero baryon chemical potential and calculate for the first time a quantitative expression for the critical temperature of the deconfinement transition in this regime. At high isospin chemical potential and sufficiently low temperatures this theory becomes equivalent to a pure Yang-Mills theory and accordingly has a first order deconfinement phase transition. Although this was conjectured in a seminal paper by Son and Stephanov in the year 2001, the critical temperature of this deconfinement phase transition was not computed. This paper computes the energy scale associated with this transition as a function of the isospin chemical potential by relating the parameters of the equivalent Yang-Mills theory to those of the underlying theory. We also relate the equation of state in one strongly interacting regime of QCD namely at finite isospin density to that in pure Yang-Mills, with the latter being amenable to straightforward numerical calculation. Our results for the critical temperature of deconfinement transition can be compared with future lattice calculations.
↳ hep-phhep-thnucl-thNPA(2015)·35 citations
12
Lorentz Coherence and the Proton Form Factor
Young S. Kim🇺🇸
The dipole cutoff behavior for the proton form factor has been and still is one of the major issues in high-energy physics. It is shown that this dipole behavior comes from the coherence between the Lorentz contraction of the proton size and the decreasing wavelength of the incoming photon signal. The contraction rates are the same for both cases. This form of coherence is studied also in the momentum-energy space. The coherence effect in this space can be explained in terms of two overlapping wave functions.
↳ hep-phnucl-thquant-phPhys.Scripta(2015)·0 citations
13
Photoproduction of $Λ (1405)$ with the two-pole structure
Seung-il Nam🇰🇷 · Hyun-Kyu Jo🇰🇷
We investigate the $Λ (1405, 1/ 2^{-}) \equiv Λ^{*}$ photoproduction off the proton target, i.e. $γ p \to K^{+} Λ^{*}$ , considering explicitly its two-pole structure, the higher ( $Λ_{H}^{*} : 1430 MeV$ ) and lower ( $Λ_{L}^{*} : 1390 MeV$ ) mass-pole contributions, suggested by the chiral-unitary model (ChUM) approaches. For this purpose, we construct a two-body process model, which mimics the Dalitz process, $γ p \to K^{+} π Σ$ , assuming that the mass of $Λ^{*}$ as the invariant mass of $π$ and $Σ$ , i.e. $M_{Λ^{*}} \sim M_{π Σ}$ . We employ the effective Lagrangian method with the tree-level Born approximation, using the gauge-invariant prescription for the phenomenological form factors. We provide the numerical results for the energy and angular dependences, $π$ - $Σ$ invariant-mass distribution, and so on. It turns out that the model parameters determined from ChUM reproduce the experimental data qualitatively well, supporting the two-pole structure. Moreover, the nucleon resonance contribution near the threshold plays an important role to describe the data.
↳ hep-phnucl-th9 citations
14
Analysing powers and spin correlations in deuteron-proton charge exchange at 726 MeV
S. Dymov🇩🇪 · T. Azaryan🇷🇺 · Z. Bagdasarian🇩🇪 · S. Barsov🇷🇺 · J. Carbonell🇫🇷 · D. Chiladze🇬🇪 · R. Engels🇩🇪 · R. Gebel🇩🇪 · K. Grigoryev🇩🇪 · M. Hartmann🇩🇪 · A. Kacharava🇩🇪 · A. Khoukaz🇩🇪 and 27 other authors
The charge exchange of vector polarised deuterons on a polarised hydrogen target has been studied in a high statistics experiment at the COSY-ANKE facility at a deuteron beam energy of Td = 726 MeV. By selecting two fast protons at low relative energy E_{pp}, the measured analysing powers and spin correlations are sensitive to interference terms between specific neutron-proton charge-exchange amplitudes at a neutron kinetic energy of Tn ~ 1/2 Td =363 MeV. An impulse approximation calculation, which takes into account corrections due to the angular distribution in the diproton, describes reasonably the dependence of the data on both E_{pp} and the momentum transfer. This lends broad support to the current neutron-proton partial-wave solution that was used in the estimation.
↳ nucl-exnucl-thPLB(2015)·2 citations
15
Deeply virtual Compton scattering at small- $x$ in future Electron - Ion Colliders
V. P. Goncalves🇧🇷 · D. S. Pires🇧🇷
The study of exclusive processes in the future electron-ion ( $e A$ ) colliders will be an important tool to investigate the QCD dynamics at high energies as they are in general driven by the gluon content of the target which is strongly subject to parton saturation effects. In this paper we compute the coherent and incoherent cross sections for the deeply virtual Compton scattering (DVCS) process relying on the color dipole approach and considering different models for the dipole - proton scattering amplitude. The dependencies of the cross sections with the energy, photon virtuality, nuclear mass number and squared momentum transfer are analysed in detail. We demonstrate that the ratio between the incoherent and coherent cross sections decreases at smaller values of $Q^{2}$ and increases at smaller values of $A$ . We show that the coherent cross section dominates at small $t$ and exhibits the typical diffractive pattern, with the number of dips in the range $∣ t ∣ \leq 0.3$ GeV $^{2}$ increasing with the mass atomic number. Our results indicate that the position of the dips are independent of the model used to treat the dipole - proton interaction as well as of the center-of-mass energy.
↳ hep-phhep-exnucl-exnucl-thPRC(2015)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE