Measurement Definitions Based on Truth Particles Tancredi Carli Fabio Cossuti
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The Five Common Particles
The Five Common Particles The world around you consists of only three particles: protons, neutrons, and electrons. Protons and neutrons form the nuclei of atoms, and electrons glue everything together and create chemicals and materials. Along with the photon and the neutrino, these particles are essentially the only ones that exist in our solar system, because all the other subatomic particles have half-lives of typically 10-9 second or less, and vanish almost the instant they are created by nuclear reactions in the Sun, etc. Particles interact via the four fundamental forces of nature. Some basic properties of these forces are summarized below. (Other aspects of the fundamental forces are also discussed in the Summary of Particle Physics document on this web site.) Force Range Common Particles It Affects Conserved Quantity gravity infinite neutron, proton, electron, neutrino, photon mass-energy electromagnetic infinite proton, electron, photon charge -14 strong nuclear force ≈ 10 m neutron, proton baryon number -15 weak nuclear force ≈ 10 m neutron, proton, electron, neutrino lepton number Every particle in nature has specific values of all four of the conserved quantities associated with each force. The values for the five common particles are: Particle Rest Mass1 Charge2 Baryon # Lepton # proton 938.3 MeV/c2 +1 e +1 0 neutron 939.6 MeV/c2 0 +1 0 electron 0.511 MeV/c2 -1 e 0 +1 neutrino ≈ 1 eV/c2 0 0 +1 photon 0 eV/c2 0 0 0 1) MeV = mega-electron-volt = 106 eV. It is customary in particle physics to measure the mass of a particle in terms of how much energy it would represent if it were converted via E = mc2. -
Decays of the Tau Lepton*
SLAC - 292 UC - 34D (E) DECAYS OF THE TAU LEPTON* Patricia R. Burchat Stanford Linear Accelerator Center Stanford University Stanford, California 94305 February 1986 Prepared for the Department of Energy under contract number DE-AC03-76SF00515 Printed in the United States of America. Available from the National Techni- cal Information Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, Virginia 22161. Price: Printed Copy A07, Microfiche AOl. JC Ph.D. Dissertation. Abstract Previous measurements of the branching fractions of the tau lepton result in a discrepancy between the inclusive branching fraction and the sum of the exclusive branching fractions to final states containing one charged particle. The sum of the exclusive branching fractions is significantly smaller than the inclusive branching fraction. In this analysis, the branching fractions for all the major decay modes are measured simultaneously with the sum of the branching fractions constrained to be one. The branching fractions are measured using an unbiased sample of tau decays, with little background, selected from 207 pb-l of data accumulated with the Mark II detector at the PEP e+e- storage ring. The sample is selected using the decay products of one member of the r+~- pair produced in e+e- annihilation to identify the event and then including the opposite member of the pair in the sample. The sample is divided into subgroups according to charged and neutral particle multiplicity, and charged particle identification. The branching fractions are simultaneously measured using an unfold technique and a maximum likelihood fit. The results of this analysis indicate that the discrepancy found in previous experiments is possibly due to two sources. -
Lepton Flavor and Number Conservation, and Physics Beyond the Standard Model
Lepton Flavor and Number Conservation, and Physics Beyond the Standard Model Andr´ede Gouv^ea1 and Petr Vogel2 1 Department of Physics and Astronomy, Northwestern University, Evanston, Illinois, 60208, USA 2 Kellogg Radiation Laboratory, Caltech, Pasadena, California, 91125, USA April 1, 2013 Abstract The physics responsible for neutrino masses and lepton mixing remains unknown. More ex- perimental data are needed to constrain and guide possible generalizations of the standard model of particle physics, and reveal the mechanism behind nonzero neutrino masses. Here, the physics associated with searches for the violation of lepton-flavor conservation in charged-lepton processes and the violation of lepton-number conservation in nuclear physics processes is summarized. In the first part, several aspects of charged-lepton flavor violation are discussed, especially its sensitivity to new particles and interactions beyond the standard model of particle physics. The discussion concentrates mostly on rare processes involving muons and electrons. In the second part, the sta- tus of the conservation of total lepton number is discussed. The discussion here concentrates on current and future probes of this apparent law of Nature via searches for neutrinoless double beta decay, which is also the most sensitive probe of the potential Majorana nature of neutrinos. arXiv:1303.4097v2 [hep-ph] 29 Mar 2013 1 1 Introduction In the absence of interactions that lead to nonzero neutrino masses, the Standard Model Lagrangian is invariant under global U(1)e × U(1)µ × U(1)τ rotations of the lepton fields. In other words, if neutrinos are massless, individual lepton-flavor numbers { electron-number, muon-number, and tau-number { are expected to be conserved. -
Muon Decay 1
Muon Decay 1 LIFETIME OF THE MUON Introduction Muons are unstable particles; otherwise, they are rather like electrons but with much higher masses, approximately 105 MeV. Radioactive nuclear decays do not release enough energy to produce them; however, they are readily available in the laboratory as the dominant component of the cosmic ray flux at the earth’s surface. There are two types of muons, with opposite charge, and they decay into electrons or positrons and two neutrinos according to the rules + + µ → e νe ν¯µ − − µ → e ν¯e νµ . The muon decay is a radioactiveprocess which follows the usual exponential law for the probability of survival for a given time t. Be sure that you understand the basis for this law. The goal of the experiment is to measure the muon lifetime which is roughly 2 µs. With care you can make the measurement with an accuracy of a few percent or better. In order to achieve this goal in a conceptually simple way, we look only at those muons that happen to come to rest inside our detector. That is, we first capture a muon and then measure the elapsed time until it decays. Muons are rather penetrating particles, they can easily go through meters of concrete. Nevertheless, a small fraction of the muons will be slowed down and stopped in the detector. As shown in Figure 1, the apparatus consists of two types of detectors. There is a tank filled with liquid scintillator (a big metal box) viewed by two photomultiplier tubes (Left and Right) and two plastic scintillation counters (flat panels wrapped in black tape), each viewed by a photomul- tiplier tube (Top and Bottom). -
Baryon Resonances and Pentaquarks on the Lattice ✩
Nuclear Physics A 754 (2005) 248c–260c Baryon resonances and pentaquarks on the lattice ✩ F.X. Lee a,b,∗, C. Bennhold a a Center for Nuclear Studies, George Washington University, Washington, DC 20052, USA b Jefferson Lab, 12000 Jefferson Avenue, Newport News, VA 23606, USA Received 17 December 2004; accepted 22 December 2004 Available online 21 January 2005 Abstract We review recent progress in computing excited baryons and pentaquarks in lattice QCD. 2004 Elsevier B.V. All rights reserved. 1. QCD primer Quantum Chromodynamics (QCD) is widely accepted as the fundamental theory of the strong interaction. The QCD Lagrangian density can be written down simply in one line (in Euclidean space) 1 L = Tr F F µν +¯q γ µD + m q, (1) QCD 2 µν µ q where Fµν = ∂Aµ − ∂Aν + g[Aµ,Aν] is the gluon field strength tensor and Dµ = ∂µ + gAµ is the covariant derivative which provides the interaction between the gluon and quark terms. The action of QCD is the integral of the Lagrangian density over space– 4 time: SQCD = LQCD d x. QCD is a highly non-linear relativistic quantum field theory. It is well known that the theory has chiral symmetry in the mq = 0 limit and the symmetry is spontaneously broken in the vacuum. At high energies, it exhibits asymptotic freedom, ✩ Based on plenary talk by F.X. Lee at HYP2003, JLab. * Corresponding author. E-mail address: [email protected] (F.X. Lee). 0375-9474/$ – see front matter 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysa.2004.12.072 F.X. -
1.1. Introduction the Phenomenon of Positron Annihilation Spectroscopy
PRINCIPLES OF POSITRON ANNIHILATION Chapter-1 __________________________________________________________________________________________ 1.1. Introduction The phenomenon of positron annihilation spectroscopy (PAS) has been utilized as nuclear method to probe a variety of material properties as well as to research problems in solid state physics. The field of solid state investigation with positrons started in the early fifties, when it was recognized that information could be obtained about the properties of solids by studying the annihilation of a positron and an electron as given by Dumond et al. [1] and Bendetti and Roichings [2]. In particular, the discovery of the interaction of positrons with defects in crystal solids by Mckenize et al. [3] has given a strong impetus to a further elaboration of the PAS. Currently, PAS is amongst the best nuclear methods, and its most recent developments are documented in the proceedings of the latest positron annihilation conferences [4-8]. PAS is successfully applied for the investigation of electron characteristics and defect structures present in materials, magnetic structures of solids, plastic deformation at low and high temperature, and phase transformations in alloys, semiconductors, polymers, porous material, etc. Its applications extend from advanced problems of solid state physics and materials science to industrial use. It is also widely used in chemistry, biology, and medicine (e.g. locating tumors). As the process of measurement does not mostly influence the properties of the investigated sample, PAS is a non-destructive testing approach that allows the subsequent study of a sample by other methods. As experimental equipment for many applications, PAS is commercially produced and is relatively cheap, thus, increasingly more research laboratories are using PAS for basic research, diagnostics of machine parts working in hard conditions, and for characterization of high-tech materials. -
Neutrino Opacity I. Neutrino-Lepton Scattering*
PHYSICAL REVIEW VOLUME 136, NUMBER 4B 23 NOVEMBER 1964 Neutrino Opacity I. Neutrino-Lepton Scattering* JOHN N. BAHCALL California Institute of Technology, Pasadena, California (Received 24 June 1964) The contribution of neutrino-lepton scattering to the total neutrino opacity of matter is investigated; it is found that, contrary to previous beliefs, neutrino scattering dominates the neutrino opacity for many astro physically important conditions. The rates for neutrino-electron scattering and antineutrino-electron scatter ing are given for a variety of conditions, including both degenerate and nondegenerate gases; the rates for some related reactions are also presented. Formulas are given for the mean scattering angle and the mean energy loss in neutrino and antineutrino scattering. Applications are made to the following problems: (a) the detection of solar neutrinos; (b) the escape of neutrinos from stars; (c) neutrino scattering in cosmology; and (d) energy deposition in supernova explosions. I. INTRODUCTION only been discussed for the special situation of electrons 13 14 XPERIMENTS1·2 designed to detect solar neu initially at rest. · E trinos will soon provide crucial tests of the theory In this paper, we investigate the contribution of of stellar energy generation. Other neutrino experiments neutrino-lepton scattering to the total neutrino opacity have been suggested as a test3 of a possible mechanism of matter and show, contrary to previous beliefs, that for producing the high-energy electrons that are inferred neutrino-lepton scattering dominates the neutrino to exist in strong radio sources and as a means4 for opacity for many astrophysically important conditions. studying the high-energy neutrinos emitted in the decay Here, neutrino opacity is defined, analogously to photon of cosmic-ray secondaries. -
1 the LOCALIZED QUANTUM VACUUM FIELD D. Dragoman
1 THE LOCALIZED QUANTUM VACUUM FIELD D. Dragoman – Univ. Bucharest, Physics Dept., P.O. Box MG-11, 077125 Bucharest, Romania, e-mail: [email protected] ABSTRACT A model for the localized quantum vacuum is proposed in which the zero-point energy of the quantum electromagnetic field originates in energy- and momentum-conserving transitions of material systems from their ground state to an unstable state with negative energy. These transitions are accompanied by emissions and re-absorptions of real photons, which generate a localized quantum vacuum in the neighborhood of material systems. The model could help resolve the cosmological paradox associated to the zero-point energy of electromagnetic fields, while reclaiming quantum effects associated with quantum vacuum such as the Casimir effect and the Lamb shift; it also offers a new insight into the Zitterbewegung of material particles. 2 INTRODUCTION The zero-point energy (ZPE) of the quantum electromagnetic field is at the same time an indispensable concept of quantum field theory and a controversial issue (see [1] for an excellent review of the subject). The need of the ZPE has been recognized from the beginning of quantum theory of radiation, since only the inclusion of this term assures no first-order temperature-independent correction to the average energy of an oscillator in thermal equilibrium with blackbody radiation in the classical limit of high temperatures. A more rigorous introduction of the ZPE stems from the treatment of the electromagnetic radiation as an ensemble of harmonic quantum oscillators. Then, the total energy of the quantum electromagnetic field is given by E = åk,s hwk (nks +1/ 2) , where nks is the number of quantum oscillators (photons) in the (k,s) mode that propagate with wavevector k and frequency wk =| k | c = kc , and are characterized by the polarization index s. -
Review of Lepton Universality Tests in B Decays
January 4, 2019 Review of Lepton Universality tests in B decays Simone Bifani∗, S´ebastienDescotes-Genony, Antonio Romero Vidalz, Marie-H´el`ene Schunex Abstract Several measurements of tree- and loop-level b-hadron decays performed in the recent years hint at a possible violation of Lepton Universality. This article presents an experimental and theoretical overview of the current status of the field. arXiv:1809.06229v2 [hep-ex] 3 Jan 2019 Published in Journal of Physics G: Nuclear and Particle Physics, Volume 46, Number 2 ∗University of Birmingham, School of Physics and Astronomy Edgbaston, Birmingham B15 2TT, United Kingdom yLaboratoire de Physique Th´eorique(UMR 8627), CNRS, Universit´eParis-Sud, Universit´eParis-Saclay, 91405 Orsay, France zInstituto Galego de F´ısicade Altas Enerx´ıas(IGFAE), Universidade de Santiago de Compostela, Santiago de Compostela, Spain xLaboratoire de l'Acc´el´erateurLin´eaire,CNRS/IN2P3, Universit´eParis-Sud, Universit´eParis-Saclay, 91440 Orsay, France Contents 1 Introduction 1 2 Lepton Universality in the Standard Model 2 3 Overview of Lepton Universality tests beyond the B sector 3 3.1 Electroweak sector . .4 3.2 Decays of pseudoscalar mesons . .5 3.3 Purely leptonic decays . .7 3.4 Quarkonia decays . .7 3.5 Summary . .7 4 Theoretical treatment of b-quark decays probing Lepton Universality 8 4.1 Effective Hamiltonian . .8 4.2 Hadronic quantities . 10 4.3 Lepton Universality observables . 13 5 Experiments at the B-factories and at the Large Hadron Collider 13 5.1 B-factories . 13 5.2 Large Hadron Collider . 16 5.3 Complementarity between the B-factories and the LHC . -
Ghost-Free Scalar-Fermion Interactions
PHYSICAL REVIEW D 98, 044043 (2018) Ghost-free scalar-fermion interactions † ‡ Rampei Kimura,1,2,* Yuki Sakakihara,3, and Masahide Yamaguchi2, 1Waseda Institute for Advanced Study, Waseda University, 1-6-1 Nishi-Waseda, Shinjuku, Tokyo 169-8050, Japan 2Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan 3Department of Physics, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan (Received 15 June 2018; published 28 August 2018) We discuss a covariant extension of interactions between scalar fields and fermions in a flat space-time. We show, in a covariant theory, how to evade fermionic ghosts appearing because of the extra degrees of freedom behind a fermionic nature even in the Lagrangian with first derivatives. We will give a concrete example of a quadratic theory with up to the first derivative of multiple scalar fields and a Weyl fermion. We examine not only the maximally degenerate condition, which makes the number of degrees of freedom correct, but also a supplementary condition guaranteeing that the time evolution takes place properly. We also show that proposed derivative interaction terms between scalar fields and a Weyl fermion cannot be removed by field redefinitions. DOI: 10.1103/PhysRevD.98.044043 I. INTRODUCTION scalar-tensor theories [4–6,13–20], vector-tensor theories [21–29], and form fields [30–32]. Construction of general theory without ghost degrees of On the other hand, generic theory with fermionic d.o.f. freedom (d.o.f.) has been discussed for a long time. has not yet been investigated well. If we could find such According to Ostrogradsky’s theorem, a ghost always appears in a higher (time) derivative theory as long as it fermionic theories which have not been explored, some is nondegenerate [1] (see also Ref. -
The Ghost Particle 1 Ask Students If They Can Think of Some Things They Cannot Directly See but They Know Exist
Original broadcast: February 21, 2006 BEFORE WATCHING The Ghost Particle 1 Ask students if they can think of some things they cannot directly see but they know exist. Have them provide examples and reasoning for PROGRAM OVERVIEW how they know these things exist. NOVA explores the 70–year struggle so (Some examples and evidence of their existence include: [bacteria and virus- far to understand the most elusive of all es—illnesses], [energy—heat from the elementary particles, the neutrino. sun], [magnetism—effect on a com- pass], and [gravity—objects falling The program: towards Earth].) How do scientists • relates how the neutrino first came to be theorized by physicist observe and measure things that cannot be seen with the naked eye? Wolfgang Pauli in 1930. (They use instruments such as • notes the challenge of studying a particle with no electric charge. microscopes and telescopes, and • describes the first experiment that confirmed the existence of the they look at how unseen things neutrino in 1956. affect other objects.) • recounts how scientists came to believe that neutrinos—which are 2 Review the structure of an atom, produced during radioactive decay—would also be involved in including protons, neutrons, and nuclear fusion, a process suspected as the fuel source for the sun. electrons. Ask students what they know about subatomic particles, • tells how theoretician John Bahcall and chemist Ray Davis began i.e., any of the various units of mat- studying neutrinos to better understand how stars shine—Bahcall ter below the size of an atom. To created the first mathematical model predicting the sun’s solar help students better understand the neutrino production and Davis designed an experiment to measure size of some subatomic particles, solar neutrinos. -
Arxiv:1908.02416V2 [Hep-Th] 21 Aug 2019
ACFI-T19-08 Unitarity, stability and loops of unstable ghosts John F. Donoghue∗ Department of Physics, University of Massachusetts Amherst, MA 01003, USA Gabriel Menezesy Department of Physics, University of Massachusetts Amherst, MA 01003, USA and Departamento de F´ısica, Universidade Federal Rural do Rio de Janeiro, 23897-000, Serop´edica, RJ, Brazil We present a new understanding of the unstable ghost-like resonance which appears in theories such as quadratic gravity and Lee-Wick type theories. Quantum corrections make this resonance unstable, such that it does not appear in the asymptotic spectrum. We prove that these theories are unitary to all orders. Unitarity is satisfied by the inclusion of only cuts from stable states in the unitarity sum. This removes the need to consider this as a ghost state in the unitarity sum. However, we often use a narrow-width approximation where we do include cuts through unstable states, and ignore cuts through the stable decay products. If we do this with the unstable ghost resonance at one loop, we get the correct answer only by using a contour which was originally defined by Lee and Wick. The quantum effects also provide damping in both the Feynman and the retarded propagators, leading to stability under perturbations. 1. INTRODUCTION Theories such as quadratic gravity [1{19] and Lee-Wick theories [20{28] have propagators which contain both quadratic and quartic momentum dependence. In addition to the pole at q2 = 0, this combination will produce a high mass pole, via 1 1 1 = − : (1) 2 q4 q2 q2 − µ2 q − µ2 The negative sign for the second term implies that this pole is ghost-like, i.e.