DOCSLIB.ORG

Lattice QCD Calculations of Hadron Spectra and Spectral Functions In

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Lattice QCD Calculations of Hadron Spectra and Spectral Functions In Lattice QCD Calculations of Hadron Sp ectra and Sp ectral Functions in the Vacuum and in a Thermal Heat Bath Dissertation zur Erlangung des Doktorgrades at fur Physik an der Fakult at Bielefeld der Universit vorgelegt von Ines Wetzorke Septemb er Contents Intro duction QCD and the Phase Diagram Quantum Chromo Dynamics Phenomena at Finite Temp erature Phases at Finite Density Strange Matter and the HDibaryon Lattice Gauge Theory Lattice Regularization Gluonic Part of the Action Fermionic Part of the Action Continuum Limit Monte Carlo Integration Inversion of the Fermion Matrix Gauge Fixing Error Analysis Contents Strange Hadron Sp ectrum Hadron Multiplets Hadron Op erators and Correlation Functions Extracting Masses from Correlation Functions Extrap olation to the Physical Point Improvement through the Fuzzing Technique Hadron Sp ectrum Strange Particle Masses HDibaryon Stability Hadron Sp ectral Functions Sp ectral Functions in QCD Principles of the Maximum Entropy Metho d Details of the Algorithm Dep endence on Input Parameters Meson Sp ectral Functions Diquark Sp ectral Functions Thermal Sp ectral Functions Free Meson Sp ectral Functions in the Continuum Free Meson Sp ectral Functions on the Lattice Meson Sp ectral Functions at Finite Temp erature Conclusions A Conventions B Numerical Results List of Figures Schematic QCD phase diagram U and chiral symmetry restoration of pseudoscalar mesons A Theoretical predictions of the Hdibaryon mass 1 Multiplet structure for pseudoscalar vector mesons and spin baryons 2 Multiplet structure for antitriplet and sextet diquark states Fuzzed fermion op erator with radius R Fuzzing for mesons baryons and dibaryons Inuence of the fuzzing technique on the Hdibaryon correlation function and the eective masses Strange hadron and Hdibaryon masses at physical mass ud Dierence of Hdibaryon and *lamb da masses for all lattice sizes Dierence of Hdibaryon and *lamb da masses for dierent input Relative error of Hdibaryon and lamb da correlation functions Sharply p eaked p osterior distribution P jD m Inuence of the input parameters on the sp ectral function at T Inuence of the input parameters on the sp ectral function at T Correlation functions and corresp onding sp ectral functions for the zero tem p erature pseudoscalar and vector meson at List of Figures Sp ectral functions for the pseudoscalar and the vector meson at dierent values Comparison of the MEM results with conventional twoexp onential t results Inuence of the fuzzing technique on the sp ectral functions Correlation functions and corresp onding sp ectral functions for the zero tem p erature diquarks Inuence of the covariance matrix smo othing pro cedure Comparison of the MEM results with exp ts for the color antitriplet and sextet diquarks Discretized free thermal meson correlation function and reconstructed sp ec tral functions Cuto and nite volume eects on the free meson correlation function Reconstructed free lattice sp ectral functions Fuzzing of the free sp ectral function Meson sp ectral functions at T c Meson masses at T obtained with MEM and twoexp onential ts the c band indicates the range obtained for the dierent data sets c Finite size eects on the pseudoscalar sp ectral function b elow the critical temp erature Sp ectral functions of the pseudoscalar and vector meson for several tem p eratures Meson correlation and sp ectral functions ab ove T c Ratio of meson and free thermal meson correlator on the lattice Restauration of the chiral symmetry b etween the scalar and pseudoscalar meson Intro duction Two asp ects of the strong interaction b etween quarks and gluons are investigated in the present thesis On the one hand it covers the exploration of the Hdibaryon stability a six quark state with equal content of the light u d and s quarks In cold and dense matter this particle may b e formed as a condensate of two baryons due to strong attractive interactions b etween quarks with maximal symmetry in the avor spin and color quantum numb ers On the other hand changes of meson prop erties in a thermal medium are investigated for a large temp erature range This constitutes the rst application of the Maximum Entropy Metho d in the sp ectral analysis of thermal meson correlators The phase diagram of QCD at vanishing baryon density is already well explored by lattice simulations Starting at low temp erature in the conned hadronic phase and increasing the temp erature a phase transition to the deconned quarkgluon plasma QGP phase can b e observed Recent exp eriments at CERN SPS gave rst evidence that such a new state of almost freely propagating quarks and gluons might exist In the near future the colliders RHIC in Bro okhaven and LHC at CERN will hop efully op en the p ossibility to explore the features of this plasma phase in more detail Exp erimental signatures at high temp erature like dilepton pro duction rates are directly related to meson sp ectral functions in this case to the vector channel The sp ectral analysis of meson correlation functions b ecame recently accessible with the Maximum Entropy Metho d MEM which p ermits to study the temp erature dep endent mo dications of the sp ectral shap e from rst principles A similarly detailed theoretical understanding of the high density region of the QCD phase diagram at low temp erature is of physical relevance in heavy ion collisions as well as in astrophysics An interesting phase structure is exp ected to arise in this case from quantum statistic eects which eg favor b osonic forms of matter over fermionic states At high densities the SU color symmetry might b e sp ontaneously broken giving rise to a color sup erconducting phase characterized by the formation of diquark condensates Furthermore dibaryons or even larger quark clusters may play an imp ortant role as Bose condensates in hyp ernuclear matter at increasing density In the current analysis previ ously obtained diquark correlators are explored more precisely with the Maximum Entropy Metho d whereas the stability of larger quark clusters is examined in a detailed analysis of the smallest ob ject of this kind the Hdibaryon Introduction The investigation of these phenomena in lattice QCD is at present restricted to simulations at an average baryon density of zero since the probabilistic interpretation of the QCD partition function in the path integral representation breaks down for nonzero chemical p otential Such calculations provide nevertheless an insight to the dominant quarkquark interactions in this region In the rst chapter QCD is describ ed as SU gauge theory in the Euclidean path integral formalism The current knowledge ab out the QCD phase diagram at nite temp erature and density is summarized with the fo cus on the changes of hadronic prop erties at the dierent phase b oundaries After a short intro duction to the relevant asp ects of strange matter in the cold and dense region of the phase diagram the previous exp erimental and theoretical searches for a stable Hdibaryon are reviewed The second chapter describ es the lattice regularization of the Euclidean path integral which includes the sp ecication of the improved discretizations of the gauge and fermion action used for the Monte Carlo simulation in the present thesis In the following some numerical details of the lattice calculation are explained which includes the generation of gauge eld congurations the inversion of the fermion matrix the gauge xing pro cedure for gaugevariant observables as well as the error analysis for correlated data sets The lattice study of the strange hadron sp ectrum and the investigation on the stability of the Hdibaryon is the content of the third chapter After a few general considerations ab out the hadron multiplet structure and the underlying interactions b etween quarks the lattice setup is illustrated with the appropriate observables for the investigated hadron channels Moreover the extrap olation of the particle masses to physical quark masses is explained Finally results obtained on four dierent lattice sizes are presented for several strange hadron masses as well as for the Hdibaryon mass The fourth
Load more

Recommended publications
  • Quasiparticle Anisotropic Hydrodynamics in Ultra-Relativistic
    QUASIPARTICLE ANISOTROPIC HYDRODYNAMICS IN ULTRA-RELATIVISTIC HEAVY-ION COLLISIONS A dissertation submitted to Kent State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy by Mubarak Alqahtani December, 2017 c Copyright All rights reserved Except for previously published materials Dissertation written by Mubarak Alqahtani BE, University of Dammam, SA, 2006 MA, Kent State University, 2014 PhD, Kent State University, 2014-2017 Approved by , Chair, Doctoral Dissertation Committee Dr. Michael Strickland , Members, Doctoral Dissertation Committee Dr. Declan Keane Dr. Spyridon Margetis Dr. Robert Twieg Dr. John West Accepted by , Chair, Department of Physics Dr. James T. Gleeson , Dean, College of Arts and Sciences Dr. James L. Blank Table of Contents List of Figures . vii List of Tables . xv List of Publications . xvi Acknowledgments . xvii 1 Introduction ......................................1 1.1 Units and notation . .1 1.2 The standard model . .3 1.3 Quantum Electrodynamics (QED) . .5 1.4 Quantum chromodynamics (QCD) . .6 1.5 The coupling constant in QED and QCD . .7 1.6 Phase diagram of QCD . .9 1.6.1 Quark gluon plasma (QGP) . 12 1.6.2 The heavy-ion collision program . 12 1.6.3 Heavy-ion collisions stages . 13 1.7 Some definitions . 16 1.7.1 Rapidity . 16 1.7.2 Pseudorapidity . 16 1.7.3 Collisions centrality . 17 1.7.4 The Glauber model . 19 1.8 Collective flow . 21 iii 1.8.1 Radial flow . 22 1.8.2 Anisotropic flow . 22 1.9 Fluid dynamics . 26 1.10 Non-relativistic fluid dynamics . 26 1.10.1 Relativistic fluid dynamics .
    [Show full text]
  • Energy-Dependent Kinetic Model of Photon Absorption by Superconducting Tunnel Junctions
    Energy-dependent kinetic model of photon absorption by superconducting tunnel junctions G. Brammertz Science Payload and Advanced Concepts Office, ESA/ESTEC, Postbus 299, 2200AG Noordwijk, The Netherlands. A. G. Kozorezov, J. K. Wigmore Department of Physics, Lancaster University, Lancaster, United Kingdom. R. den Hartog, P. Verhoeve, D. Martin, A. Peacock Science Payload and Advanced Concepts Office, ESA/ESTEC, Postbus 299, 2200AG Noordwijk, The Netherlands. A. A. Golubov, H. Rogalla Department of Applied Physics, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands. Received: 02 June 2003 – Accepted: 31 July 2003 Abstract – We describe a model for photon absorption by superconducting tunnel junctions in which the full energy dependence of all the quasiparticle dynamic processes is included. The model supersedes the well-known Rothwarf-Taylor approach, which becomes inadequate for a description of the small gap structures that are currently being developed for improved detector resolution and responsivity. In these junctions relaxation of excited quasiparticles is intrinsically slow so that the energy distribution remains very broad throughout the whole detection process. By solving the energy- dependent kinetic equations describing the distributions, we are able to model the temporal and spectral evolution of the distribution of quasiparticles initially generated in the photo-absorption process. Good agreement is obtained between the theory and experiment. PACS numbers: 85.25.Oj, 74.50.+r, 74.40.+k, 74.25.Jb To be published in the November issue of Journal of Applied Physics 1 I. Introduction The development of superconducting tunnel junctions (STJs) for application as photon detectors for astronomy and materials analysis continues to show great promise1,2.
    [Show full text]
  • Vortices and Quasiparticles in Superconducting Microwave Resonators
    Syracuse University SURFACE Dissertations - ALL SURFACE May 2016 Vortices and Quasiparticles in Superconducting Microwave Resonators Ibrahim Nsanzineza Syracuse University Follow this and additional works at: https://surface.syr.edu/etd Part of the Physical Sciences and Mathematics Commons Recommended Citation Nsanzineza, Ibrahim, "Vortices and Quasiparticles in Superconducting Microwave Resonators" (2016). Dissertations - ALL. 446. https://surface.syr.edu/etd/446 This Dissertation is brought to you for free and open access by the SURFACE at SURFACE. It has been accepted for inclusion in Dissertations - ALL by an authorized administrator of SURFACE. For more information, please contact [email protected]. Abstract Superconducting resonators with high quality factors are of great interest in many areas. However, the quality factor of the resonator can be weakened by many dissipation chan- nels including trapped magnetic flux vortices and nonequilibrium quasiparticles which can significantly impact the performance of superconducting microwave resonant circuits and qubits at millikelvin temperatures. Quasiparticles result in excess loss, reducing resonator quality factors and qubit lifetimes. Vortices trapped near regions of large mi- crowave currents also contribute excess loss. However, vortices located in current-free areas in the resonator or in the ground plane of a device can actually trap quasiparticles and lead to a reduction in the quasiparticle loss. In this thesis, we will describe exper- iments involving the controlled trapping of vortices for reducing quasiparticle density in the superconducting resonators. We provide a model for the simulation of reduc- tion of nonequilibrium quasiparticles by vortices. In our experiments, quasiparticles are generated either by stray pair-breaking radiation or by direct injection using normal- insulator-superconductor (NIS)-tunnel junctions.
    [Show full text]
  • Coupling Experiment and Simulation to Model Non-Equilibrium Quasiparticle Dynamics in Superconductors
    Coupling Experiment and Simulation to Model Non-Equilibrium Quasiparticle Dynamics in Superconductors A. Agrawal9, D. Bowring∗1, R. Bunker2, L. Cardani3, G. Carosi4, C.L. Chang15, M. Cecchin1, A. Chou1, G. D’Imperio3, A. Dixit9, J.L DuBois4, L. Faoro16,7, S. Golwala6, J. Hall13,14, S. Hertel12, Y. Hochberg11, L. Ioffe5, R. Khatiwada1, E. Kramer11, N. Kurinsky1, B. Lehmann10, B. Loer2, V. Lordi4, R. McDermott7, J.L. Orrell2, M. Pyle17, K. G. Ray4, Y. J. Rosen4, A. Sonnenschein1, A. Suzuki8, C. Tomei3, C. Wilen7, and N. Woollett4 1Fermi National Accelerator Laboratory 2Pacific Northwest National Laboratory 3Sapienza University of Rome 4Lawrence Livermore National Laboratory 5Google, Inc. 6California Institute of Technology 7University of Wisconsin, Madison 8Lawrence Berkeley National Laboratory 9University of Chicago 10University of California, Santa Cruz 11Hebrew University of Jerusalem 12University of Massachusetts, Amherst 13SNOLAB 14Laurentian University 15Argonne National Laboratory 16Laboratoire de Physique Therique et Hautes Energies, Sorbornne Universite 17University of California, Berkeley August 31, 2020 Thematic Areas: (check all that apply /) (CF1) Dark Matter: Particle Like (CF2) Dark Matter: Wavelike (IF1) Quantum Sensors (IF2) Photon Detectors (IF9) Cross Cutting and Systems Integration (UF02) Underground Facilities for Cosmic Frontier (UF05) Synergistic Research ∗Corresponding author: [email protected] 1 Abstract In superconducting devices, broken Cooper pairs (quasiparticles) may be considered signal (e.g., transition edge sensors, kinetic inductance detectors) or noise (e.g., quantum sensors, qubits). In order to improve design for these devices, a better understanding of quasiparticle production and transport is required. We propose a multi-disciplinary collaboration to perform measurements in low-background facilities that will be used to improve modeling and simulation tools, suggest new measurements, and drive the design of future improved devices.
    [Show full text]
  • SL Paper 3 Markscheme
    theonlinephysicstutor.com SL Paper 3 This question is about leptons and mesons. Leptons are a class of elementary particles and each lepton has its own antiparticle. State what is meant by an Unlike leptons, the meson is not an elementary particle. State the a. (i) elementary particle. [2] (ii) antiparticle of a lepton. b. The electron is a lepton and its antiparticle is the positron. The following reaction can take place between an electron and positron. [3] Sketch the Feynman diagram for this reaction and identify on your diagram any virtual particles. c. (i) quark structure of the meson. [2] (ii) reason why the following reaction does not occur. Markscheme a. (i) a particle that cannot be made from any smaller constituents/particles; (ii) has the same rest mass (and spin) as the lepton but opposite charge (and opposite lepton number); b. Award [1] for each correct section of the diagram. correct direction ; correct direction and ; virtual electron/positron; Accept all three time orderings. @TOPhysicsTutor facebook.com/TheOnlinePhysicsTutor c. (i) / up and anti-down; theonlinephysicstutor.com (ii) baryon number is not conserved / quarks are not conserved; Examiners report a. Part (a) was often correct. b. The Feynman diagrams rarely showed the virtual particle. c. A significant number of candidates had a good understanding of quark structure. This question is about fundamental interactions. The kaon decays into an antimuon and a neutrino as shown by the Feynman diagram. b.i.Explain why the virtual particle in this Feynman diagram must be a weak interaction exchange particle. [2] c. A student claims that the is produced in neutron decays according to the reaction .
    [Show full text]
  • Wave-Whirl-Particle Gudrun Kalmbach H.E University of Ulm, MINT Verlag, Germany
    OSP Journal of Nuclear Science Short Communication Wave-Whirl-Particle Gudrun Kalmbach H.E University of Ulm, MINT Verlag, Germany Corresponding Author: Gudrun Kalmbach H.E, University of Ulm, MINT Verlag, Germany Received: December 19, 2019; Accepted: December 26, 2019; Published: January 02, 2019 In earlier articles the author suggested to extend the wave For dark energy and matter are suggested a pinched and a particle duality of physics to a triple, adding whirls. Whirls Horn torus with a singularity. Below are two models for this: are mathematically computed differently than waves. Parti- dark energy has inverted frequency helix lines inside and cles can be considered as a kind of bubble formation in other aggregate phase state. Wave equations have a double Minkowski cone. They have higher speeds than light 1-dimensional space expansion in direction where a wave is their cylindrical location is closed at projective infinity by a travelling. Harmonic waves for a vibrating string miss this are inverted at the Schwarzschild radius to 1-dimensional coordinate. Sound expands through pressure on the other lemniscates,inside the pinched drawn torus.with twoIn figure red or 1 greenis shown or bluethat quarkswings. hand in a sound cone. Measured is its power as intensity per All quarks are joined in this kind of pinched torus at their free carrying one of the three olor charges r, g, b,in nucle- area (figure 1). center as the Horn torus singularity. (figure 2) They are set - onsons, arebut whirls,confined often in nucleons drawn as by stretchable the two color springs charged between gluon twoquasiparticles quarks as (fieldend points; quantums) different as an geometries energy exchange.
    [Show full text]
  • "Normal-Metal Quasiparticle Traps for Superconducting Qubits"
    Normal-Metal Quasiparticle Traps For Superconducting Qubits: Modeling, Optimization, and Proximity Effect Von der Fakultät für Mathematik, Informatik und Naturwissenschaften der RWTH Aachen University zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften genehmigte Dissertation vorgelegt von Amin Hosseinkhani, M.Sc. Berichter: Universitätsprofessor Dr. David DiVincenzo, Universitätsprofessorin Dr. Kristel Michielsen Tag der mündlichen Prüfung: March 01, 2018 Diese Dissertation ist auf den Internetseiten der Universitätsbibliothek online verfügbar. Metallische Quasiteilchenfallen für supraleitende Qubits: Modellierung, Optimisierung, und Proximity-Effekt Kurzfassung: Bogoliubov Quasiteilchen stören viele Abläufe in supraleitenden Elementen. In supraleitenden Qubits wechselwirken diese Quasiteilchen beim Tunneln durch den Josephson- Kontakt mit dem Phasenfreiheitsgrad, was zu einer Relaxation des Qubits führt. Für Tempera- turen im Millikelvinbereich gibt es substantielle Hinweise für die Präsenz von Nichtgleichgewicht- squasiteilchen. Während deren Entstehung noch nicht einstimmig geklärt ist, besteht dennoch die Möglichkeit die von Quasiteilchen induzierte Relaxation einzudämmen indem man die Qu- asiteilchen von den aktiven Bereichen des Qubits fernhält. In dieser Doktorarbeit studieren wir Quasiteilchenfallen, welche durch einen Kontakt eines normalen Metalls (N) mit der supraleit- enden Elektrode (S) eines Qubits definiert sind. Wir entwickeln ein Modell, das den Einfluss der Falle auf die Quasiteilchendynamik beschreibt,
    [Show full text]
  • Charmed Baryon Spectroscopy in a Quark Model
    Charmed baryon spectroscopy in a quark model Tokyo tech, RCNP A,RIKEN B, Tetsuya Yoshida,Makoto Oka , Atsushi HosakaA , Emiko HiyamaB, Ktsunori SadatoA Contents Ø Motivation Ø Formalism Ø Result ü Spectrum of single charmed baryon ü λ-mode and ρ-mode Ø Summary Motivation Many unknown states in heavy baryons ü We know the baryon spectra in light sector but still do not know heavy baryon spectra well. ü Constituent quark model is successful in describing Many unknown state baryon spectra and we can predict unknown states of heavy baryons by using the model. Σ Difference from light sector ΛC C ü λ-mode state and ρ-mode state split in heavy quark sector ü Because of HQS, we expect that there is spin-partner Motivation light quark sector vs heavy quark sector What is the role of diquark? How is it in How do spectrum and the heavy quark limit？ wave function change? heavy quark limit m m q Q ∞ λ , ρ mode ü we can see how the spectrum and wave-funcon change ü Is charm sector near from heavy quark limit (or far) ? Hamiltonian ij ij ij Confinement H = ∑Ki +∑(Vconf + Hhyp +VLS ) +Cqqq i i< j " % " % 2 π 1 1 brij 2α (m p 2m ) $ ' (r) $ Coul ' Spin-Spin = ∑ i + i i + αcon ∑$ 2 + 2 'δ +∑$ − ' i 3 i< j # mi mj & i< j # 2 3rij & ) # &, 2αcon 8π 3 2αten 1 3Si ⋅ rijS j ⋅ rij + + Si ⋅ S jδ (rij )+ % − Si ⋅ S j (. ∑ 3 % 2 ( Coulomb i< j *+3m i mj 3 3mimj rij $ rij '-. the cause of mass spliPng Tensor 1 2 2 4 l s C +∑αSO 2 3 (ξi +ξ j + ξiξ j ) ij ⋅ ij + qqq i< j 3mq rij Spin orbit ü We determined the parameter that the result of the Strange baryon will agree with experimental results .
    [Show full text]
  • Coupled Wire Model of Z4 Orbifold Quantum Hall States
    Coupled Wire Model of Z4 Orbifold Quantum Hall States Charles L. Kane Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 Ady Stern Department of Condensed Matter Physics, The Weizmann Institute of Science, Rehovot 76100, Israel We introduce a coupled wire model for a sequence of non-Abelian quantum Hall states that generalize the Z4 parafermion Read Rezayi state. The Z4 orbifold quantum Hall states occur at filling factors ν = 2=(2m − p) for odd integers m and p, and have a topological order with a neutral sector characterized by the orbifold conformal field theory with central charge c = 1 at radius p R = p=2. When p = 1 the state is Abelian. The state with p = 3 is the Z4 Read Rezayi state, and the series of p ≥ 3 defines a sequence of non-Abelian states that resembles the Laughlin sequence. Our model is based on clustering of electrons in groups of four, and is formulated as a two fluid model in which each wire exhibits two phases: a weak clustered phase, where charge e electrons coexist with charge 4e bosons and a strong clustered phase where the electrons are strongly bound in groups of 4. The transition between these two phases on a wire is mapped to the critical point of the 4 state clock model, which in turn is described by the orbifold conformal field theory. For an array of wires coupled in the presence of a perpendicular magnetic field, strongly clustered wires form a charge 4e bosonic Laughlin state with a chiral charge mode at the edge, but no neutral mode and a gap for single electrons.
    [Show full text]
  • Thermodynamics of Hot Hadronic Gases at Finite Baryon Densities
    Thermodynamics of Hot Hadronic Gases at Finite Baryon Densities A THESIS SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY Michael Glenn Albright IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Doctor of Philosophy Joseph Kapusta, Advisor November, 2015 c Michael Glenn Albright 2015 ALL RIGHTS RESERVED Acknowledgements First, I would like to express my sincerest appreciation to my advisor, Joseph Kapusta, for all of his guidance and assistance throughout my time as a graduate student at the University of Minnesota. I would also like to thank Clint Young, my research collaborator, for his helpful suggestions. I would also like to thank my parents, Chris and Glenn, and my sister Jaime. Your love and support throughout the years made this possible. Finally, I thank the members of my thesis committee: Marco Peloso, Roberta Humphreys, and Roger Rusack. This work was supported by the School of Physics and Astronomy at the University of Minnesota, by a University of Minnesota Graduate School Fellowship, and by the US Department of Energy (DOE) under Grant Number DE-FG02-87ER40328. I also acknowledge computational support from the University of Minnesota Supercomputing Institute. Programming their supercomputers was a fun and memorable experience. i Dedication To my parents, Chris and Glenn, and my sister Jaime|thanks. ii Abstract In this thesis we investigate equilibrium and nonequilibrium thermodynamic prop- erties of Quantum Chromodynamics (QCD) matter at finite baryon densities. We begin by constructing crossover models for the thermodynamic equation of state. These use switching functions to smoothly interpolate between a hadronic gas model at low energy densities to a perturbative QCD equation of state at high energy densities.
    [Show full text]
  • Quasi-Dirac Monopoles
    research highlights Defective yet strong fundamental particle, the magnetic polymeric film, the researchers embedded Nature Commun. 5, 3186 (2014) monopole, with non-zero magnetic silver nanoparticles that have a localized monopole charge, has grasped the attention surface plasmon resonance in the blue With a tensile strength of over 100 GPa, of many. The existence of magnetic spectral range; the fabricated film therefore a pristine graphene layer is the strongest monopoles is now not only supported by the scatters this colour while being almost material known. However, most graphene work of Dirac, but by both the grand unified completely transparent in the remaining fabrication processes inevitably produce theory and string theory. However, both visible spectral range. The researchers a defective layer. Also, structural defects theories realize that magnetic monopoles suggest that dispersion in a single matrix of are desirable in some of the material’s might be too few and too massive to be metallic nanoparticles with sharp plasmonic technological applications, as defects allow detected or created in a lab, so physicists resonances tuned at different wavelengths for the opening of a bandgap or act as pores started to explore approaches to obtain will lead to the realization of multicoloured for molecular sieving, for example. Now, by such particles using condensed-matter transparent displays. LM tuning the exposure of graphene to oxygen systems. Now, Ray and co-workers report plasma to control the creation of defects, the latest observation of a Dirac monopole Ardavan Zandiatashbar et al. show that a quasiparticle (pictured), this time in a Facet formation Adv. Mater. http://doi.org/rb5 (2014) single layer of graphene bearing sp3-type spinor Bose–Einstein condensate.
    [Show full text]
  • Ask a Scientist Answers
    Ask a scientist answers. GN I quote the beginning of the question, then my answer: Q11: “Since beta decay is when …” A11: Good question. The weak force is responsible for changing one quark into another, in this case a d-quark into a u-quark. Because the electric charge must conserved one needs to emit a negative charge (the neutron is neutral, the proton is +1, so you need a -1- type particle). In principle there could be other -1 particles emitted (say a mu-) but nature is lazy and will go with the easiest to come by (as in the “lowest possible energy” needed to do the job) particle, an electron. Of course, because we have an electron in the final state now we also need a matching anti-neutrino, as the lepton number (quantum number that counts the electrons, neutrinos, and their kind – remember the slide with the felines in my presentation) needs to be conserved as well. Now, going back to your original question “…where they come from?” the energy of the original nucleus. Remember E=m * c^2. That is a recipe for creating particles (mass) if one has enough initial energy. In this case in order for the beta decay to occur (naturally) you need the starting nucleus to have a higher sum of the energies of the daughter nucleus one gets after decay and the energies of the electron and antineutrino combined. That energy difference can then be “spent” in creating the mass of the electron and antineutrino (and giving them, and the daughter nucleus some kinetic energy, assuming there are energy leftovers).
    [Show full text]