Nuclear Theory·nucl-th

Tuesday·December 20, 2016

19 papers—7 primary·12 cross-listed

08
Recent progress on intrinsic charm
T. J. Hobbs🇺🇸
Over the past $\sim 10$ years, the topic of the nucleon's nonperturbative or $intrinsic$ charm (IC) content has enjoyed something of a renaissance, largely motivated by theoretical developments involving quark modelers and PDF fitters. In this talk I will briefly describe the importance of intrinsic charm to various issues in high-energy phenomenology, and survey recent progress in constraining its overall normalization and contribution to the momentum sum rule of the nucleon. I end with the conclusion that progress on the side of calculation has now placed the onus on experiment to unambiguously resolve the proton's intrinsic charm component.
↳ hep-phhep-exnucl-thEPJ Web Conf.(2017)·3 citations
09
EPPS16: Nuclear parton distributions with LHC data
Kari J. Eskola🇫🇮 · Petja Paakkinen🇫🇮 · Hannu Paukkunen🇪🇸 · Carlos A. Salgado🇪🇸
We introduce a global analysis of collinearly factorized nuclear parton distribution functions (PDFs) including, for the first time, data constraints from LHC proton-lead collisions. In comparison to our previous analysis, EPS09, where data only from charged-lepton-nucleus deep inelastic scattering (DIS), Drell-Yan (DY) dilepton production in proton-nucleus collisions and inclusive pion production in deuteron-nucleus collisions were the input, we now increase the variety of data constraints to cover also neutrino-nucleus DIS and low-mass DY production in pion-nucleus collisions. The new LHC data significantly extend the kinematic reach of the data constraints. We now allow much more freedom for the flavour dependence of nuclear effects than in other currently available analyses. As a result, especially the uncertainty estimates are more objective flavour by flavour. The neutrino DIS plays a pivotal role in obtaining a mutually consistent behaviour for both up and down valence quarks, and the LHC dijet data clearly constrain gluons at large momentum fraction. Mainly for insufficient statistics, the pion-nucleus DY and heavy gauge boson production in proton-lead collisions impose less visible constraints. The outcome - a new set of next-to-leading order nuclear PDFs called EPPS16 - is made available for applications in high-energy nuclear collisions.
↳ hep-phhep-exnucl-exnucl-thEPJC(2017)·745 citations
10
What is the magnetic field distribution for the equation of state of magnetized neutron stars?
V. Dexheimer🇺🇸 · B. Franzon🇩🇪 · R. O. Gomes🇧🇷 · R. L. S. Farias🇧🇷 · S. S. Avancini🇧🇷 · S. Schramm🇩🇪
In this Letter, we report a realistic calculation of the magnetic field profile for the equation of state inside strongly magnetized neutron stars. Unlike previous estimates, which are widely used in the literature, we find that magnetic fields increase relatively slowly with increasing baryon chemical potential (or baryon density) of magnetized matter. More precisely, the increase is polynomial instead of exponential, as previously assumed. Through the analysis of several different realistic models for the microscopic description of stellar matter (including hadronic, hybrid and quark models) combined with general relativistic solutions endowed with a poloidal magnetic field obtained by solving Einstein-Maxwell's field equations in a self-consistent way, we generate a phenomenological fit for the magnetic field distribution in the stellar polar direction to be used as input in microscopic calculations.
↳ astro-ph.HEastro-ph.SRgr-qcnucl-thPLB(2017)·57 citations
11
Photons from the Color Glass Condensate in p+A collisions
Sanjin Benic🇯🇵 · Kenji Fukushima🇯🇵 · Oscar Garcia-Montero🇩🇪 · Raju Venugopalan🇺🇸
We report on a first NLO computation of photon production in p+A collisions at collider energies within the Color Glass Condensate framework, significantly extending previous LO results. At central rapidites, our result is the dominant contribution and probes multi-gluon correlators in nuclei. At high photon momenta, the result is directly sensitive to the nuclear gluon distribution. The NLO result contains two processes, the annihilation process and the process with $q q ˉ$ pair and a photon in the final state. We provide a numerical evaluation of the photon spectrum from the annihilation process.
↳ hep-phnucl-thEPJ Web Conf.(2017)·0 citations
12
Productions of $η$ , $ρ^{0}$ and $ϕ$ at large transverse momentum in Heavy ion Collisions
Wei Dai🇨🇳 · Ben-Wei Zhang🇨🇳
The suppression of the productions of the $η$ meson in relativistic heavy-ion collisions and its ratio of $η / π^{0}$ are computed theoretically in the framework of the perturbative QCD(pQCD) to confront the experimental data which matches well. We explore how the hadron production ratios as $η / π^{0}$ would further disclose the informations of the production suppressions due to the energy loss of the energetic jet that propagating though the QGP medium. Also, we present our further studies on vector mesons such as $ρ^{0}$ and $ϕ$ within the same framework. The theoretical predictions based on pQCD are thus firstly given which give a decent description on the experimental measurements. It paved the way to the uniformly understanding of the strong suppression of single hadron productions at large transverse momentum which is a convincing evidence of the jet quenching effect.
↳ hep-phnucl-thNucl.Part.Phys.Proc.(2017)·2 citations
13
Time Dependent $q^$ from AdS/CFT
W. A. Horowitz🇿🇦
We present the first ever AdS/CFT calculation of $q^$ for a light quark jet as a function of position or, equivalently, time. Our result does not suffer from the gamma factor blow up of the usual time-independent AdS/CFT heavy quark setup and is qualitatively similar to, but differs by $\sim O (1)$ factor from, the light flavor result of Liu, Rajagopal, and Wiedemann. Our findings can be immediately implemented into any $q^$ -based energy loss model. Our $q^$ derivation relies on our calculation of the average distance squared, $s^{2} (t)$ , travelled by the endpoint of a string falling in an AdS $_{3}$ -Schwarzschild spacetime. The early time behavior is ballistic, $s^{2} (t) \sim t^{2}$ , but the late time behavior is the usual diffusive Brownian motion, $s^{2} (t) \sim t$ . These late time dynamics are universal and depend only on the near-horizon physics, which allows us to generalize our results to arbitrary dimensions and thus make contact with the physics explored by RHIC and LHC. Additionally, we find that AdS/CFT predicts angular ordering for radiation in medium, just as in vacuum, and in contradistinction to weak-coupling, with its anti-angular ordering prediction. Finally, our results also imply, sensibly, that AdS/CFT predicts a smooth interpolation between the angular correlations of open heavy flavor and light flavor observables.
↳ hep-phhep-thnucl-thJ.Phys.Conf.Ser.(2017)·0 citations
14
The analytic properties of the quark propagator from an effective infrared interaction model
Andreas Windisch🇺🇸
In this paper I investigate the analytic properties of the quark propagator Dyson-Schwinger equation (DSE) in the Landau gauge. In the quark self-energy, the combined gluon propagator and quark-gluon vertex is modeled by an effective interaction (the so-called Maris-Tandy interaction), where the ultraviolet term is neglected. This renders the loop integrand of the quark self-energy analytic on the cut-plane -Pi < arg(x) < Pi of the square of the external momentum. Exploiting the simplicity of the truncation, I study solutions of the quark propagator in the domain x in [-5.1,0] GeV^2 X i[0,10.2] GeV^2. Because of a complex conjugation symmetry, this region fully covers the parabolic integration domain for Bethe-Salpeter equations (BSEs) for bound state masses of up to 4.5 GeV. Employing a novel numerical technique that is based on highly parallel computation on graphics processing units (GPUs), I extract more than 6500 poles in this region, which arise as the bare quark mass is varied over a wide range of closely spaced values. The poles are grouped in 23 individual 'trajectories', that capture the movement of the poles in the complex region as the bare mass is varied. The raw data of the pole locations and -residues is provided as supplemental material, which can be used to parametrize solutions of the complex quark propagator for a wide range of bare mass values and for large bound state masses. This study is a first step towards an extension of previous work on the analytic continuation of perturbative one-loop integrals, with the long-term goal of establishing a framework that allows for the numerical extraction of the analytic properties of the quark propagator with a truncation that extends beyond the rainbow by making adequate adjustments in the contour of the radial integration of the quark self-energy.
↳ hep-phnucl-thPRC(2017)·47 citations
15
Generation of strong magnetic fields in hybrid and quark stars driven by the electroweak interaction of quarks
Maxim Dvornikov (IZMIRAN, Tomsk State University)🇷🇺
We study the generation of strong large scale magnetic fields in compact stars containing degenerate quark matter with unbroken chiral symmetry. The magnetic field growth is owing to the magnetic field instability driven by the electroweak interaction of quarks. In this system we predict the enhancement of the seed magnetic field $1 0^{12} G$ to the strengths $(1 0^{14} - 1 0^{15}) G$ . In our analysis we use the typical parameters of the quark matter in the core of a hybrid star or in a quark star. We also apply of the obtained results to model the generation of magnetic fields in magnetars.
↳ hep-phastro-ph.HEnucl-thJ.Phys.Conf.Ser.(2017)·0 citations
16
Effective particles in quantum field theory
Stanislaw D. Glazek🇺🇸 · Arkadiusz P. Trawinski🇵🇱
The concept of effective particles is introduced in the Minkowski space-time Hamiltonians in quantum field theory using a new kind of the relativistic renormalization group procedure that does not integrate out high-energy modes but instead integrates out the large changes of invariant mass. The new procedure is explained using examples of known interactions. Some applications in phenomenology, including processes measurable in colliders, are briefly presented.
↳ hep-phhep-thnucl-thFew Body Syst.(2017)·7 citations
17
Exclusive heavy vector meson photoproduction in hadronic collisions at the LHC: predictions of the Color Glass Condensate model for Run 2 energies
V. P. Goncalves🇧🇷 · B. D. Moreira🇧🇷 · F. S. Navarra🇧🇷
In this letter we update our predictions for exclusive $J /Ψ$ and $Υ$ photoproduction in proton-proton and nucleus - nucleus collisions at the Run 2 LHC energies obtained with the color dipole formalism and considering the impact parameter Color Glass Condensate model (bCGC) for the forward dipole - target scattering amplitude. A comparison with the LHCb data on rapidity distributions and photon - hadron cross sections is presented. Our results demonstrate that the current data can be quite well described by the bCGC model, which takes into account nonlinear effects in the QCD dynamics and reproduces the very precise HERA data, without introducing any additional effect or free parameter.
↳ hep-phhep-exnucl-exnucl-thPRD(2017)·29 citations
18
Correlated wounded hot spots in proton-proton interactions
Javier L. Albacete🇪🇸 · Hannah Petersen🇩🇪 · Alba Soto-Ontoso🇪🇸
We investigate the effect of non-trivial spatial correlations between proton constituents, considered in this work to be gluonic hot spots, on the initial conditions of proton-proton collisions from ISR to LHC energies, i.e. $s = 52.6, 7000, 13000$ GeV. The inclusion of these correlations is motivated by their fundamental role in the description of a recently observed new feature of $pp$ scattering at $s = 7$ TeV, the hollowness effect. Our analysis relies on a Monte-Carlo Glauber approach including fluctuations in the hot spot positions and their entropy deposition in the transverse plane. We explore both the energy dependence and the effect of spatial correlations on the number of wounded hot spots, their spatial distribution and the eccentricities, $ε_{n}$ , of the initial state geometry of the collision. In minimum bias collisions we find that the inclusion of short range repulsive correlations between the hot spots reduces the value of the eccentricity ( $ε_{2}$ ) and the triangularity ( $ε_{3}$ ). In turn, upon considering only the events with the highest entropy deposition i.e. the ultra-central ones, the probability of having larger $ε_{2, 3}$ increases significantly in the correlated scenario. Finally, the eccentricities show a quite mild energy dependence.
↳ hep-phnucl-exnucl-thPRC(2017)·22 citations
19
On electrodynamics of chiral matter
Zebin Qiu🇨🇳 · Gaoqing Cao🇨🇳 · Xu-Guang Huang🇨🇳
Many-body systems with chiral fermions can exhibit novel transport phenomena that violate parity and time reversal symmetries, such as the chiral magnetic effect, the anomalous Hall effect, and the anomalous generation of charge. Based on the Maxwell-Chern-Simons electrodynamics, we examine some electromagnetic and optical properties of such systems including the electrostatics, the magnetostatics, the propagation of electromagnetic waves, the novel optical effects, etc.
↳ cond-mat.mes-hallhep-phnucl-thphysics.plasm-phPRD(2017)·74 citations

Affiliations

first authorsco-authorsvia INSPIRE