DOCSLIB.ORG

LINE SHAPES of the EXOTIC C¯C MESONS X(3872)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
LINE SHAPES of the EXOTIC C¯C MESONS X(3872) LINE SHAPES OF THE EXOTIC cc¯ MESONS X(3872) AND Z±(4430) DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Meng Lu, B.S., M.S. ***** The Ohio State University 2008 Dissertation Committee: Approved by Eric Braaten, Adviser Richard J. Furnstahl Adviser Klaus Honscheid Graduate Program in Junko Shigemitsu Physics c Copyright by Meng Lu 2008 ABSTRACT The B-factory experiments have recently discovered a series of new cc¯ mesons, including the X(3872) and the first manifestly exotic meson Z±(4430). The prox- 0 0 imity of the mass of the X to the D∗ D¯ threshold has motivated its identification as a loosely-bound hadronic molecule whose constituents are a superposition of the 0 0 0 0 charm mesons pairs D∗ D¯ and D D¯ ∗ . Factorization formulas for its line shapes are derived by taking advantage of the universality of S-wave resonances near a 2-particle threshold and by including the effects from the nonzero width of D∗ meson and the inelastic scattering channels of the charm mesons. The best fit to the line shapes of + 0 0 0 X in the J/ψπ π− and D D¯ π channels measured by the Belle Collaboration corre- 0 0 sponds to the X being a bound state whose mass is just below the D∗ D¯ threshold. The differences between the line shapes of X produced in B+ decays and B0 decays as + + 0 0 0 0 well as in decay channels J/ψπ π−,J/ψπ π−π , and D D¯ π are further derived by taking into account the effects from the closeby channel composed of charged charm mesons. A more speculative application of the universality of S-wave resonances near a 2-particle threshold is to the Z±(4430), which is interpreted as a charm meson + ¯ 0 + ¯ 0 molecule composed of a superposition of D1 D∗ and D∗ D1. The small ratio of the + binding energy of the Z to the width of its constituent D1 is exploited to obtained + simple predictions for its line shapes in the channels ψ(2S)π and D∗D¯ ∗π. ii To my family iii ACKNOWLEDGMENTS It is difficult to overstate my gratitude to my advisor Dr. Eric Braaten for his guidance, advice, support, encouragement, and patience, which all together have made this dissertation possible. He has not only educated me with physics knowledge and techniques but also inspired me by his insight, rigor, enthusiasm, and focusing on physics research. It has been an honor and privilege to work with him. I would like to thank Dr. Jungil Lee, Dr. Masaoki Kusunoki, Dr. Dongqing Zhang, Daekyoung Kang, Huichao Song, Anastasios Taliotis, Evan S. Frodermann, and James C. Stapleton for collaborations and discussions. In particular, I am in debt to Dr. Masaoki Kusunoki, for his earlier research results on the X(3872) particle, and to Dr. Jungil Lee, for the collaboration on the research project on meson molecules. I would also like to thank all my teachers, friends, and classmates in Ohio State and Fudan for providing a stimulating and enjoyable environment in which I have learned and grown. My deepest gratitude goes to my parents Yuliang Lu and Yaqin Dong for their constant love and support. Last but not the least, I would like to thank Yuan Zhang for her love, understanding, and belief in me. This research was supported in part by the Department of Energy under grant DE-FG02- 91-ER4069. iv VITA June 4th, 1981 ............................. Born - Xuanhua, Hebei, China 2003 ........................................B.S. Fudan University 2006 ........................................M.S. The Ohio State University 2003-2004 ..................................University Fellow, The Ohio State University 2004-2006 ..................................Graduate Teaching Associate, The Ohio State University. 2006-current ................................Graduate Research Associate, The Ohio State University. PUBLICATIONS Research Publications E. Braaten and M. Lu, “Line Shapes of the Z(4430)”, arXiv:0712.3885 [hep-ph]. E. Braaten and M. Lu, “The Effects of Charged Charm Mesons on the Line Shapes of the X(3872)”, Phys. Rev. D, 77, 014029 (2008). E. Braaten and M. Lu, “Line Shapes of the X(3872)”, Phys. Rev. D, 76, 094028 (2007). E. Braaten and M. Lu, “Weakly-bound hadronic molecule near a 3-body threshold”, Phys. Rev. D, 76, 054010 (2007). E. Braaten and M. Lu, “Operator product expansion in the production and decay of the X(3872)”, Phys. Rev. D, 74, 054020 (2006). v Y. Xu, M. Lu and R. K. Su, “Extended Wronskian determinant approach and iterative solutions of one-dimensional Dirac equation”, Commun. Theor. Phys., 41, 859 (2004) FIELDS OF STUDY Major Field: Physics vi TABLE OF CONTENTS Page Abstract....................................... ii Dedication...................................... iii Acknowledgments.................................. iv Vita ......................................... v LIST OF TABLES x LIST OF FIGURES xi Chapters: 1. Introduction 1 1.1 Fundamental Particles and Their Interactions . ..... 1 1.2 OrdinaryHadrons............................. 5 1.3 ExoticHadrons .............................. 9 1.4 HadronicMolecules............................ 10 1.5 Recently Discovered cc¯ Mesons...................... 11 1.6 X(3872).................................. 17 vii 1.7 Z±(4430) ................................. 22 2. Charm Mesons 24 2.1 Isospin................................... 24 2.2 Charge Conjugation and G Parity.................... 26 2.3 MassesofCharmMesons. .. .. 29 2.4 Decay Widths of D∗ Mesons....................... 30 2.5 Energy-Dependent Width of Virtual D∗ ................. 33 3. Charm Meson Scattering 36 3.1 BasicScatteringFormalism . 36 3.2 Universality of S-wave Resonances Near Thresholds . 39 3.3 Scattering Channels for D∗D¯ ...................... 42 3.4 Scattering channels for D1D¯ ∗ ...................... 46 3.5 Single Neutral Scattering Channel . .. 48 3.6 Coupled Neutral and Charged Scattering Channels . .... 51 3.7 ConstraintsfromIsospinSymmetry . 54 0 0 4. Line shapes of X(3872) near D D¯ ∗ Threshold 60 4.1 Factorization Formulas with Neutral Channel . .... 60 4.2 The Mass and Width of the X(3872) .................. 65 4.3 Short Distance Decay of X(3872) .................... 66 4.4 Line Shapes of X(3872) in B Decays .................. 68 4.5 Fitstotheenergydistributions . 71 4.5.1 Experimentaldata ........................ 72 4.5.2 Theoreticalmodel. .. .. 75 viii 4.5.3 Fittingprocedure . .. .. 78 5. Line Shapes of X(3872) in DD¯ ∗ Threshold Region 81 5.1 Factorization Formulas with Coupled Neutral and Charged Channels 81 5.2 Constraintsfromisospinsymmetry . 85 5.3 Current-current factorization and heavy-quark symmetry....... 89 5.4 Line Shapes of X(3872) in B Decays .................. 90 5.5 RatiosofDecayRates .......................... 96 6. Line Shapes of Z±(4430) 100 6.1 Low-energycharmmesonscattering . 100 6.2 Lineshapes ................................ 102 7. Conclusion 107 Appendices: A. Universal Transition Amplitude for Particles with a Large Scat- tering Length 112 A.1 ThemodelandFeynmanrules. 112 A.2 Propagation for D1D2 betweeninteractions. 114 A.3 Universal Transition Amplitude f(E).................. 117 BIBLIOGRAPHY 120 ix LIST OF TABLES Table Page 1.1 Basic properties of some particles appearing in the thesis....... 8 1.2 Charmoniadiscoveredby1978. 13 1.3 New cc¯ mesons discovered since 2003 . 16 2.1 Basicpropertiesofcharmmesons. 25 + 4.1 Belle data on the J/ψπ π− energydistribution . 73 4.2 Belle data on the D0D¯ 0π0 energydistribution . 75 4.3 Parameters of line shapes determined by fitting Belle data ...... 79 x LIST OF FIGURES Figure Page + 1.1 Line shape of X(3872) in J/ψπ π− channel .............. 18 0 0 0 0 0 1.2 Line shape of X(3872) in D D¯ π and D∗ D¯ channels . 21 1.3 Line shape of Z±(4430) in ψ(2S) π± channel .............. 23 2.1 Energy-dependent widths of virtual D∗ mesons............. 35 3.1 Cartoons of the imaginary parts of 2-body scattering amplitude f(E) 43 4.1 Energy dependence of the short-distance decay rate of X(3872) ΓC (E) 67 4.2 Line shape of X(3872)inshort-distance decay mode. 69 4.3 Line shape of X(3872) in long-distance decay mode . 70 4.4 Smeared line shapes of X(3872)..................... 71 4.5 Data fitting for line shape of X(3872) in short-distance decay modes . 74 4.6 Data fitting for line shape of X(3872) in short-distance decay modes . 76 4.7 χ2 analysis of the fitting parameters for the line shapes . .. 78 5.1 Line shape of X(3872) in D0D¯ 0π0 channel ............... 92 + 0 5.2 Line shape of X(3872) in J/ψπ π−π channel............. 93 + 5.3 Line shape of X(3872) in J/ψπ π− channel .............. 95 5.4 Ratio of decay rates R as a function of scattering parameter 1/γ1 .. 99 xi 6.1 Line shapes of the Z+ .......................... 104 A.1 1-loop Feynman diagram for D D D D .............. 114 1 2 → 1 2 A.2 Geometricseriesofone-loopdiagrams. ... 117 xii CHAPTER 1 INTRODUCTION 1.1 Fundamental Particles and Their Interactions The modern theory for describing the elementary particles and their interactions is the standard model of particle physics. It is a relativistic quantum field theory, which means that it incorporates both quantum mechanics and special relativity and it is formulated in terms of quantum field operators that create and annihilate elementary particles. It is also a gauge theory with the gauge group SU(3) SU(2) U(1), which × × characterizes the symmetry properties of the interactions between the elementary particles. In the standard model of particle physics, the elementary particles that form matter in nature are classified into quarks and leptons. There are six types or flavors of quarks: up (u), down (d), strange (s), charm (c), bottom (b), and top (t) quark. Each quark has an antiparticle partner; they are labelledu ¯, d¯,s ¯,c ¯, ¯b, and t¯. The two lightest quarks u and d and their antiparticles are called light quarks in this thesis. The term heavy quarks is used to refer to c and b and their antiparticles in this thesis, although t is actually much heavier than b and c.
Load more

Recommended publications
  • Qt7r7253zd.Pdf
    Lawrence Berkeley National Laboratory Recent Work Title RELATIVISTIC QUARK MODEL BASED ON THE VENEZIANO REPRESENTATION. II. GENERAL TRAJECTORIES Permalink https://escholarship.org/uc/item/7r7253zd Author Mandelstam, Stanley. Publication Date 1969-09-02 eScholarship.org Powered by the California Digital Library University of California Submitted to Physical Review UCRL- 19327 Preprint 7. z RELATIVISTIC QUARK MODEL BASED ON THE VENEZIANO REPRESENTATION. II. GENERAL TRAJECTORIES RECEIVED LAWRENCE RADIATION LABORATORY Stanley Mandeistam SEP25 1969 September 2, 1969 LIBRARY AND DOCUMENTS SECTiON AEC Contract No. W7405-eng-48 TWO-WEEK LOAN COPY 4 This is a Library Circulating Copy whIch may be borrowed for two weeks. for a personal retention copy, call Tech. Info. Dlvislon, Ext. 5545 I C.) LAWRENCE RADIATION LABORATOR SLJ-LJ UNIVERSITY of CALIFORNIA BERKELET DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California.
    [Show full text]
  • Hadrons and Nuclei Abstract
    Hadrons and Nuclei William Detmold (editor),1 Robert G. Edwards (editor),2 Jozef J. Dudek,2, 3 Michael Engelhardt,4 Huey-Wen Lin,5 Stefan Meinel,6, 7 Kostas Orginos,2, 3 and Phiala Shanahan1 (USQCD Collaboration) 1Massachusetts Institute of Technology 2Jefferson Lab 3College of William and Mary 4New Mexico State University 5Michigan State University 6University of Arizona 7RIKEN BNL Research Center Abstract This document is one of a series of whitepapers from the USQCD collaboration. Here, we discuss opportunities for lattice QCD calculations related to the structure and spectroscopy of hadrons and nuclei. An overview of recent lattice calculations of the structure of the proton and other hadrons is presented along with prospects for future extensions. Progress and prospects of hadronic spectroscopy and the study of resonances in the light, strange and heavy quark sectors is summarized. Finally, recent advances in the study of light nuclei from lattice QCD are addressed, and the scope of future investigations that are currently envisioned is outlined. 1 CONTENTS Executive summary3 I. Introduction3 II. Hadron Structure4 A. Charges, radii, electroweak form factors and polarizabilities4 B. Parton Distribution Functions5 1. Moments of Parton Distribution Functions6 2. Quasi-distributions and pseudo-distributions6 3. Good lattice cross sections7 4. Hadronic tensor methods8 C. Generalized Parton Distribution Functions8 D. Transverse momentum-dependent parton distributions9 E. Gluon aspects of hadron structure 11 III. Hadron Spectroscopy 13 A. Light hadron spectroscopy 14 B. Heavy quarks and the XYZ states 20 IV. Nuclear Spectroscopy, Interactions and Structure 21 A. Nuclear spectroscopy 22 B. Nuclear Structure 23 C. Nuclear interactions 26 D.
    [Show full text]
  • Discovery Potential for the Lhcb Fully Charm Tetraquark X(6900) State Via P¯P Annihilation Reaction
    PHYSICAL REVIEW D 102, 116014 (2020) Discovery potential for the LHCb fully charm tetraquark Xð6900Þ state via pp¯ annihilation reaction † ‡ Xiao-Yun Wang,1,* Qing-Yong Lin,2, Hao Xu,3 Ya-Ping Xie,4 Yin Huang,5 and Xurong Chen4,6,7, 1Department of physics, Lanzhou University of Technology, Lanzhou 730050, China 2Department of Physics, Jimei University, Xiamen 361021, China 3Department of Applied Physics, School of Science, Northwestern Polytechnical University, Xi’an 710129, China 4Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China 5School of Physical Science and Technology, Southwest Jiaotong University, Chendu 610031, China 6University of Chinese Academy of Sciences, Beijing 100049, China 7Guangdong Provincial Key Laboratory of Nuclear Science, Institute of Quantum Matter, South China Normal University, Guangzhou 510006, China (Received 2 August 2020; accepted 16 November 2020; published 18 December 2020) Inspired by the observation of the fully-charm tetraquark Xð6900Þ state at LHCb, the production of Xð6900Þ in pp¯ → J=ψJ=ψ reaction is studied within an effective Lagrangian approach and Breit-Wigner formula. The numerical results show that the cross section of Xð6900Þ at the c.m. energy of 6.9 GeV is much larger than that from the background contribution. Moreover, we estimate dozens of signal events can be detected by the D0 experiment, which indicates that searching for the Xð6900Þ via antiproton-proton scattering may be a very important and promising way. Therefore, related experiments are suggested to be carried out. DOI: 10.1103/PhysRevD.102.116014 I. INTRODUCTION Γ ¼ 168 Æ 33 Æ 69 MeV; ð2Þ In recent decades, more and more exotic hadron states have been observed [1].
    [Show full text]
  • Chiral Extrapolations and Exotic Meson Spectrum
    Physics Letters B 526 (2002) 72–78 www.elsevier.com/locate/npe Chiral extrapolations and exotic meson spectrum Anthony W. Thomas a, Adam P. Szczepaniak b a Special Research Centre for the Subatomic Structure of Matter and Department of Physics and Mathematical Physics, Adelaide University, Adelaide SA 5005, Australia b Department of Physics and Nuclear Theory Center, Indiana University, Bloomington, IN 47405, USA Received 15 June 2001; received in revised form 10 December 2001; accepted 18 December 2001 Editor: H. Georgi Abstract We examine the chiral corrections to exotic meson masses calculated in lattice QCD. In the soft pion limit we find that corrections from virtual, closed channels lead to strong non-linear behavior which has been found in other hadronic systems. We find the resulting mass shifts to be as large as 100 MeV and therefore large corrections to the predictions of exotic meson masses based on linear extrapolations to the chiral limit are expected. Furthermore, by considering a class of phenomenologically successful hybrid meson models we show that this behavior is not altered by contributions from open decay channels. 2002 Published by Elsevier Science B.V. One of the biggest challenges in hadronic physics is with glueballs—they have regular quantum numbers to understand the role of gluonic degrees of freedom. and therefore cannot be unambiguously identified as Even though there is evidence from high energy purely gluonic excitations. On the other hand, the ex- experiments that gluons contribute significantly to istence of mesons with exotic quantum numbers (com- hadron structure, for example, to the momentum and binations of spin, parity and charge conjugation, J PC, spin sum rules, there is a pressing need for direct which cannot be attributed to valence quarks alone), observation of gluonic excitations at low energies.
    [Show full text]
  • Observation of Structure in the J/Ψ-Pair Mass Spectrum
    EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN) CERN-EP-2020-115 LHCb-PAPER-2020-011 CERN-EP-2020-115June 30, 2020 22 June 2020 Observation of structure in the J= -pair mass spectrum LHCb collaborationy Abstract p Using proton-proton collision data at centre-of-mass energies of s = 7, 8 and 13 TeV recorded by the LHCb experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 9 fb−1, the invariant mass spectrum of J= pairs is studied. A narrow structure around 6:9 GeV/c2 matching the lineshape of a resonance and a broad structure just above twice the J= mass are observed. The deviation of the data from nonresonant J= -pair production is above five standard deviations in the mass region between 6:2 and 7:4 GeV/c2, covering predicted masses of states composed of four charm quarks. The mass and natural width of the narrow X(6900) structure are measured assuming a Breit{Wigner lineshape. Submitted to Science Bulletin c 2020 CERN for the benefit of the LHCb collaboration. CC BY 4.0 licence. yAuthors are listed at the end of this paper. ii 1 1 Introduction 2 The strong interaction is one of the fundamental forces of nature and it governs the 3 dynamics of quarks and gluons. According to quantum chromodynamics (QCD), the 4 theory describing the strong interaction, quarks are confined into hadrons, in agreement 5 with experimental observations. The quark model [1,2] classifies hadrons into conventional 6 mesons (qq) and baryons (qqq or qqq), and also allows for the existence of exotic hadrons 7 such as tetraquarks (qqqq) and pentaquarks (qqqqq).
    [Show full text]
  • Model-Independent Evidence for Exotic Hadron Contributions To#[Subscript B][Superscript 0]→J/#Pπ−Decays
    Model-Independent Evidence for Exotic Hadron Contributions to#[subscript b][superscript 0]→J/#pπ−Decays The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Aaij, R., C. Abellán Beteta, B. Adeva, M. Adinolfi, Z. Ajaltouni, S. Akar, J. Albrecht, et al. "Model-Independent Evidence for Exotic Hadron Contributions toΛ[subscript b][superscript 0]→J/ψpπ−Decays." Physical Review Letters 117, 082002 (August 2016): 1-9 © 2016 CERN for the LHCb Collaboration As Published http://dx.doi.org/10.1103/PhysRevLett.117.082002 Publisher American Physical Society Version Final published version Citable link http://hdl.handle.net/1721.1/110294 Terms of Use Creative Commons Attribution Detailed Terms http://creativecommons.org/licenses/by/3.0 week ending PRL 117, 082002 (2016) PHYSICAL REVIEW LETTERS 19 AUGUST 2016 0 − Model-Independent Evidence for J=ψp Contributions to Λb → J=ψpK Decays R. Aaij et al.* (LHCb Collaboration) (Received 19 April 2016; published 18 August 2016) 0 − The data sample of Λb → J=ψpK decays acquired with the LHCb detector from 7 and 8 TeV pp collisions, corresponding to an integrated luminosity of 3 fb−1, is inspected for the presence of J=ψp or J=ψK− contributions with minimal assumptions about K−p contributions. It is demonstrated at more than 0 − − nine standard deviations that Λb → J=ψpK decays cannot be described with K p contributions alone, and that J=ψp contributions play a dominant role in this incompatibility. These model-independent results þ support the previously obtained model-dependent evidence for Pc → J=ψp charmonium-pentaquark states in the same data sample.
    [Show full text]
  • Exotic Hadronic States
    Exotic Hadronic States Jeff Wheeler May 1, 2018 Abstract Background: The current model of particle physics predicts all hadronic ​ matter in nature to exist in one of two families: baryons or mesons. However, the laws do not forbid larger collections of quarks from existing. Tetraquark and ​ pentaquark particles have long been postulated. Purpose: Advance the particle ​ ​ landscape into a regime including more complex systems of quarks. Studying these systems could help physicists gain greater insight into the nature of the strong force. Methods: Many different particle colliders and detectors of varying ​ ​ energies and sensitivities were used to search for evidence of four- or five-quark states. Results: After a few false alarms, evidence for the existence of both ​ ​ tetraquark and pentaquark was obtained from multiple experiments. Conclusion: ​ Positive results from around the world have shown exotic hadronic states of matter to exist, and extended research will continue to test the leading theories of today and help further our understanding of the laws of physics. I. Introduction Since the discovery of atomic particles, scientists have attempted to determine their individual properties and produce a systematic method of grouping based on those properties. In the early days of particle physics, little was known besides the mere existence of protons and neutrons. With the advent of particle colliders and detectors, however, the collection of known particles grew rapidly. It wasn’t until 1961 that a successful classification system was produced independently by American physicist Murray Gell-Mann and Israeli physicist Yuval Ne’eman. This method was built upon the symmetric representation group SU(3).
    [Show full text]
  • Multiquark Hadrons - Current Status and Issues
    Multiquark Hadrons - Current Status and Issues Ahmed Ali ∗ Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany ∗E-mail: [email protected] DOI: http://dx.doi.org/10.3204/DESY-PROC-2016-04/Ali Multiquark states having four and five valence quarks, called tetraquarks and pentaquarks, respectively, are now firmly established experimentally, with the number of such indepen- dent states increasing steadily over the years. They represent a new facet of QCD, but the underlying dynamics is currently poorly understood. I review some selected aspects of data and discuss several competing phenomenological models put forward to accommodate them. 1 Introduction Ever since the discovery of the state X(3872) by Belle in 2003 [1], a large number of multi- quark states has been discovered in particle physics experiments, conducted at the electron- positron and hadron colliders. They are exotic, having J PC quantum numbers not allowed for qq¯ states, or have too small a decay width for their mass, and, in some cases, their de- cay distributions have unfamiliar features not seen before. Most of them are quarkonium-like states, in that they have a (cc¯) or a (b¯b) component in their Fock space. A good fraction of them are electrically neutral but some are singly-charged. Examples are X(3872)(J PC = 1++), PC P + P + Y (4260)(J = 1−−), Zc(3900)±(J = 1 ), Pc(4450)±(J = 5/2 ), in the hidden charm P + P + sector, and Zb(10610)±(J = 1 ) and Zb(10650)±(J = 1 ), in the hidden bottom sector. P + The numbers in the parentheses are their masses in MeV.
    [Show full text]
  • Chiral Extrapolations and Exotic Meson Spectrum
    IUNTC 01-02 ADP-01-18/T453 May 2001 CHIRAL EXTRAPOLATIONS AND EXOTIC MESON SPECTRUM Anthony W. Thomasa and Adam P. Szczepaniakb a Special Research Centre for the Subatomic Structure of Matter and Department of Physics and Mathematical Physics, Adelaide University, Adelaide SA 5005, Australia a Department of Physics and Nuclear Theory Center Indiana University, Bloomington, IN 47405, USA We examine the chiral corrections to exotic meson masses calculated in lattice QCD. In particular, we ask whether the non-linear chiral behavior at small quark masses, which has been found in other hadronic systems, could lead to large cor- rections to the predictions of exotic meson masses based on linear extrapolations to the chiral limit. We find that our present understanding of exotic meson decay dy- namics suggests that open channels may not make a significant contribution to such non-linearities whereas the virtual, closed channels may be important. arXiv:hep-ph/0106080v1 7 Jun 2001 1. Introduction. One of the biggest challenges in hadronic physics is to understand the role of gluonic degrees of freedom. Even though there is evidence from high energy experiments that gluons contribute significantly to hadron structure, for example to the momentum and spin sum rules, there is a pressing need for direct observation of gluonic excitations at low energies. In particular, it is expected that glue should manifest itself in the meson spectrum and reflect on the nature of confinement. In recent years a few candidates for glueballs and hybrid mesons have been re- ported. For example, there are two major glueball candidates, the f0(1500) and f0(1710), scalar-isoscalar mesons observed inpp ¯ annihilation, in central production as well as in J/ψ (f0(1710)) decays [1].
    [Show full text]
  • Group Theoretic Classification of Pentaquarks and Numerical Predictions of Their Masses
    DEGREE PROJECT IN TECHNOLOGY, FIRST CYCLE, 15 CREDITS STOCKHOLM, SWEDEN 2019 Group Theoretic Classification of Pentaquarks and Numerical Predictions of Their Masses PONTUS HOLMA KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ENGINEERING SCIENCES EXAMENSARBETE INOM TEKNIK, GRUNDNIVÅ, 15 HP STOCKHOLM, SVERIGE 2019 Gruppteoretisk klassificering av pentakvarkar och numeriska förutsägelser av deras massor PONTUS HOLMA KTH SKOLAN FÖR ARKITEKTUR OCH SAMHÄLLSBYGGNAD Abstract In this report we investigate the exotic hadrons known as pentaquarks. A brief overview of relevant concepts and theory is initially presented in order to aid the reader. There- after, the history of this field with regards to theory and experiments is discussed. In particular, a group theoretic classification of these states is studied. A simple mass for- mula for pentaquark states is examined and predictions are subsequently made about the composition and mass of possible pentaquark states. Furthermore, this mass formula is modified to examine and predict additional pentaquark states. A number of numerical fits concerning the masses of pentaquarks are performd and studied. Future research is explored with regards to the information presented in this thesis. Sammanfattning I denna uppsats unders¨oker vi de exotiska hadronerna k¨andasom pentakvarkar. En kort ¨overblick av relevanta koncept och teorier ¨arpresenterade med syfte att underl¨atta f¨orl¨asaren. Historia i detta omr˚ademed avseende p˚ab˚adeteori och experiment ¨ar presenterad. Specifikt ing˚aren unders¨okningav gruppteoretisk klassificering av dessa tillst˚and.En enkel formel f¨ormassan hos pentakvarkar unders¨oksoch anv¨andsf¨oratt f¨orutsp˚amassorna och uppbyggnaden av m¨ojligapentakvarktillst˚and. Dessutom modi- fieras denna formel f¨oratt studera och f¨orutsp˚aytterligare pentakvarktillst˚and.Ett antal numeriska anpassningar relaterade till massorna hos pentakvarkarna genomf¨orsoch un- ders¨oks.Framtida forskning unders¨oksi koppling med material presenterat i uppsatsen.
    [Show full text]
  • Exotic Hadron Spectroscopy
    EPJ Web of Conferences 72, 00020 ( 2014) DOI: 10.1051/epjconf/20147200020 C Owned by the authors, published by EDP Sciences, 2014 Exotic Hadron Spectroscopy Alessandro Pilloni1,a 1Dipartimento di Fisica and INFN, “Sapienza” Università di Roma P.le Aldo Moro 2 - I-00185 Roma (Italy) Abstract. Since ten years ago experiments have been observing a host of exotic states decaying into heavy quarkonia. The interpretation of most of them still remains uncertain and, in some cases, controversial. Notwith- standing, a considerable progress has been made on the quality of the experimental information available and a number of ideas and models have been put forward to explain the observations. We will review the most promis- ing theoretical interpretations of exotic states, in particular we will discuss the nature of the charmonium-like resonances in the region 3850−4050 MeV, and propose a new mechanism to explain prompt X(3872) production cross section at hadron colliders. Finally, the phenomenology of doubly charmed states is commented. 1 Introduction • Tetraquarks: a quark pair (diquark) in the 3¯c (attrac- tive) configuration, neutralizing its color with an anti- Heavy quarkonium sector has proved to be extremely use- quark pair [6, 7]. A full nonet of states is predicted for ful for the understanding of QCD. In the limit mQ →∞, each spin-parity, i.e. a large number of states are ex- the gauge field dynamics can be simplified in terms of ef- pected. There is no need for these states to be close to fective potential models [1], or in terms of effective the- any threshold.
    [Show full text]
  • Evidence of Exotic Meson Particle Discovered At
    Vol. 51 - No. 37 September 19, 1997 BROOKHAVEN NATIONAL LABORATORY Evidence of Exotic Meson Particle Discovered at AGS Researchers at BNL’s Alternating mass of 1.4 GeV after years of select- Gradient Synchrotron (AGS) accelera- ing and analyzing data from products tor have found evidence of a new and of billions of particle collisions made rare subatomic particle called an “ex- during the experiment’s 1994 run. otic” meson. The result was presented to par- This finding at AGS Experiment ticipants of the Seventh International 852, described in the September 1 Conference on Hadron Spectroscopy, issue of Physical Review Letters, helps held at BNL August 25-30 (see story validate the standard model, the cen- on page 2). At the conference, confir- tral theory of modern physics. mation of the E852 result was re- Also, the finding could improve un- ported by what is called the Crystal derstanding of how matter binds to- Barrel collaboration at CERN, the gether at the relatively low energy European particle physics laboratory. level of 18 billion electron volts (GeV). “In some sense, we’ve discovered a The E852 team of 51 scientists, new form of matter,” said Chung. “This graduate students and undergradu- particle had been hypothesized [in ates includes researchers from: BNL, the late 1970s], but it’s never, never Northwestern University, Rensselaer been pinned down. Polytechnic Institute, the University “To find evidence of a particle that of Massachusetts, Dartmouth College, has never been detected before, one and Russia’s Institute for High En- that’s so important to our understand- ergy Physics and the Moscow State ing of elementary particles, is hugely University.
    [Show full text]