DOCSLIB.ORG

Pionium As a Source of False Events in the K→Πνν Decays

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Pionium As a Source of False Events in the K→Πνν Decays PHYSICAL REVIEW D 102, 113005 (2020) Pionium as a source of false events in the K → πνν¯ decays Peter Lichard Institute of Physics and Research Centre for Computational Physics and Data Processing, Silesian University in Opava, 746 01 Opava, Czech Republic and Institute of Experimental and Applied Physics, Czech Technical University in Prague, 128 00 Prague, Czech Republic (Received 1 June 2020; revised 3 November 2020; accepted 20 November 2020; published 18 December 2020) We suggest that the decay modes of kaons with a pion and a pionium (πþπ− atom) in the final state can constitute a not yet considered background to the very rare decay K → πνν¯. In fact, a part of pioniums may escape the decay region before decaying into two π0s (or to π0π0γ in the case of excited pionium). To illustrate the importance of this background, we show that it may even explain, under some assumptions, the unexpected KL decay events that appeared in the KOTO experiment. DOI: 10.1103/PhysRevD.102.113005 Two important experiments investigating the rare kaon this surprising result. The analysis performed in Ref. [9] decays in flight are currently running. The main aim of both shows that if the four events in the KOTO signal region were is to test the Standard Model and to constrain new physics real, it would mean a branching fraction of the underlying theories by precisely measuring the very rare kaon decays mechanism equal to into a pion and two neutrinos. The NA62 experiment at the CERN Super Proton Synchrotron [1–4] deals with pos- B K → π0νν¯ 2 1þ2.0ðþ4.1Þ 10−9 ð L ÞKOTO ¼ . −1.1 −1.7 × ð3Þ itively charged kaons Kþ and aims to collect enough ð Þ Kþ → πþνν¯ events to get a signal to background ratio at the 68(95)% confidence level. 10∶1 þ − of . The Standard Model predicts the branching The π π atom, pionium (usually denoted as A2π), was fraction [5] for this decay [6], discovered in 1993 at the Institute of High Energy Physics at Serpukhov, Russia [12] and intensively studied in the B Kþ → πþνν¯ 8 4 1 0 10−11: ð Þ¼ð . Æ . Þ × ð1Þ Dimeson Relativistic Atomic Complex (DIRAC) experi- ment [13] at the CERN Proton Synchrotron. In these The KOTO experiment [7] is being conducted at the Hadron experiments, the pioniums were produced by the proton Experimental Facility at the Japan Proton Accelerator beam impinging on a target. In the same target, the Research Complex. It was designed to observe the decay pioniums broke-up into their constituents with approxi- K → π0νν¯ L of long-lived neutral kaons. The theoretical mately equal energies and small relative momenta. branching fraction [6] is The decay of pionium to two neutral pions is dominant 0 −11 and the measured lifetime is [13] BðKL → π νν¯Þ¼ð3.4 Æ 0.6Þ × 10 : ð2Þ þ0.28 −15 τ1 ¼ 3.15−0 26 × 10 s: ð4Þ Until recently, both rare kaon decay experiments proceeded s . as expected, slowly pushing down the upper bounds The NA48=2 Collaboration at the CERN SPS [14] studied of branching fractions. However, in September 2019, KÆ → πÆπ0π0 decays and found an anomaly in the π0π0 Satoshi Shinohara (on behalf of the KOTO Collaboration) invariant mass distribution in the vicinity of 2mπþ that can be [8] announced the presence of four events in the signal interpreted as the production of pioniums in the kaon decays 0 10 0 02 region in the situation where mere . Æ . events and their subsequent two-π0 decay. For our later consid- were expected. Very soon, several papers appeared, e.g., 48=2 – erations, it is important that the NA Collaboration in Refs. [9 11], aimed at finding new physics interpretations of their seminal paper [14] determined the branching ratio Æ Æ ΓðK → π A2πÞ R ¼ ¼ð1.61 Æ 0.66Þ × 10−5: ð5Þ Published by the American Physical Society under the terms of Γ KÆ → πÆπþπ− the Creative Commons Attribution 4.0 International license. ð Þ Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, Another important discovery concerns the exited pio- and DOI. Funded by SCOAP3. nium. The DIRAC Collaboration observed [15] so-called 2470-0010=2020=102(11)=113005(5) 113005-1 Published by the American Physical Society PETER LICHARD PHYS. REV. D 102, 113005 (2020) πþπ− 1 long-lived atoms, which are the 2p atomic states E EEà Ppà ; 0 PC −− aÆ ¼ ð a Æ aÞ (A2π) with quantum numbers J ¼ 1 . Its lifetime was M measured in Ref. [15] with the result where M, E, and P are the mass, energy, and momentum K Eà M2 m2 = 2M pà τ 0 45þ1.08 10−11 : of the L, respectively, a ¼ð þ aÞ ð Þ, a ¼ 2p ¼ . −0.30 × s ð6Þ 2 2 ðM − maÞ=ð2MÞ. Numerically, Ea− ¼ 0.497 GeV and Ea ¼ 1.456 GeV. Such a long lifetime is caused by the fact that the decay þ To simplify the consideration further [17], we will modes to the positive C-parity states π0π0 and γγ are now assume that all pioniums have the same laboratory momen- forbidden and the slow 2p → 1s transition dominates. After tum, given as the mean value, reaching the 1s state, a decay to two π0s quickly follows: 0 0 0 Z qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi → 2πγ → π π γ Ea A2π A . 1 þ 2 2 1 The decay of the charged kaons into excited pionium A0 pa ¼ E − madE ¼ 2π Ea − Ea− E 2ðEa − Ea−Þ has not been reported yet. Neither has been the neutral kaon þ a− þ E p decay into any pionium. E p − E p − m2 aþ þ aþ ; × aþ aþ a− a− a log ð9Þ In order to show that the pioniums may contribute to the Ea− þ pa− background in the K → πνν¯ experiments by important pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi p E2 −m2 p 0 880 = amount, we will estimate it in the KOTO experiment. To where aÆ ¼ aÆ a. Numerically, a ¼ . GeV c. this end, we need at least a crude estimate of the branching The probability that pionium travels the path s without 0 fraction of decay KL → π A2π. We assume that the branch- decaying is given by ing ratio SðsÞ¼expf−s=lg; 0 ΓðKL → π A2πÞ R˜ l ¼ 0 þ − where is the mean decay length of pionium, ΓðKL → π π π Þ paτ l ¼ ; ð10Þ has the same value as that for charged kaons (5). Then we ma can write the branching-fraction estimate τ being the pionium mean lifetime. For the two types of B K → π0 R B K → π0πþπ− l 2 98þ0.27 μ l 4 2þ10.2 ð L A2πÞ¼ × ð L Þ pioniums, we get 1s ¼ . −0.25 m and 2p ¼ . −2.8 mm. L ≈ 2 × 10−6; ð7Þ If we denote the length of the signal region as , the mean survival probability of pionium at the point where it leaves the signal region is where we have also consulted Ref. [16]. Z We will also consider possibility that the pionium that 1 L l S¯ S L − z z 1 − −L=l : appears in the kaon decays is not the ground state (1s) ¼ L ð Þd ¼ L ½ expf g ð11Þ pionium, but its excited (2p) partner and that the corre- 0 sponding branching fraction are the same, Numerical values for two kinds of pionium are [18] 0 0 −6 BðKL → π A2πÞ ≈ 2 × 10 : ð8Þ S¯ 1 75þ0.16 10−6; 1s ¼ . −0.15 × S¯ 2 5þ6.0 10−3: In what follows, we will pursue those two alternatives in 2p ¼ . −1.7 × parallel. To simplify the reasoning, we will ignore the momentum Multiplying these numbers by the assumed branching fractions (7) and (8), we obtain the branching fractions of spread of the KL beam in the KOTO experiment and will K → π0 K → π0 0 use its peak value P 1.4 GeV=c [7]. The length of the L A2π and L A2π events that look like the ¼ 0 KOTO signal region is L ¼ 1.7 m. Another quantity that KL → π νν¯ events because pioniums left the KOTO decay enters the game is the pionium mass. It is given by volume undecayed, ma ¼ 2mπþ − b, where b is the binding energy. We will B 3 50þ0.32 10−12; take its coulombic value, which can be calculated from the 1s ¼ . −0.30 × ð12Þ hydrogen-atom-like formula. One obtains b ¼ 1.86 keV b 0 464 B 5 0þ12.0 10−9: for the pionium ground state and ¼ . keV for the 2p ¼ . −3.4 × ð13Þ excited 2p state. The laboratory energy of pionium with mass ma is Branching fraction (12) is by 3 orders of magnitude smaller uniformly distributed in an interval, the bounds of which than branching fraction (3), which characterizes the pres- are given by the formula ence of unexpected events in the KOTO signal region. 113005-2 PIONIUM AS A SOURCE OF FALSE EVENTS IN THE … PHYS. REV. D 102, 113005 (2020) Therefore, we will not follow the 1s pionium option any m2 − m2 p K π 230 5 =c: Tmax;νν ¼ ¼ . MeV longer. 2mK A comparison of (13) with (3) suggests that the anoma- 0 lous events in the KOTO experiment could be explained as Given a pT cut, we can restrict the masses of X s that can undecayed 2p pioniums. But to make a realistic compari- be detected as son, we must take into account that the experimental rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi K → π0νν¯ K → π0 0 qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi efficiencies for the L and L A2π are differ- 2 2 2 2 m 0 < m m − 2m m p : ent.
Load more

Recommended publications
  • Mesons Modeled Using Only Electrons and Positrons with Relativistic Onium Theory Ray Fleming [email protected]
    All mesons modeled using only electrons and positrons with relativistic onium theory Ray Fleming [email protected] All mesons were investigated to determine if they can be modeled with the onium model discovered by Milne, Feynman, and Sternglass with only electrons and positrons. They discovered the relativistic positronium solution has the mass of a neutral pion and the relativistic onium mass increases in steps of me/α and me/2α per particle which is consistent with known mass quantization. Any pair of particles or resonances can orbit relativistically and particles and resonances can collocate to form increasingly complex resonances. Pions are positronium, kaons are pionium, D mesons are kaonium, and B mesons are Donium in the onium model. Baryons, which are addressed in another paper, have a non-relativistic nucleon combined with mesons. The results of this meson analysis shows that the compo- sition, charge, and mass of all mesons can be accurately modeled. Of the 220 mesons mod- eled, 170 mass estimates are within 5 MeV/c2 and masses of 111 of 121 D, B, charmonium, and bottomonium mesons are estimated to within 0.2% relative error. Since all mesons can be modeled using only electrons and positrons, quarks and quark theory are unnecessary. 1. Introduction 2. Method This paper is a report on an investigation to find Sternglass and Browne realized that a neutral pion whether mesons can be modeled as combinations of (π0), as a relativistic electron-positron pair, can orbit a only electrons and positrons using onium theory. A non-relativistic particle or resonance in what Browne companion paper on baryons is also available.
    [Show full text]
  • The Muon G-2 Discrepancy: Errors Or New Physics?
    The muon g-2 discrepancy: errors or new physics? † M. Passera∗, W. J. Marciano and A. Sirlin∗∗ ∗Istituto Nazionale Fisica Nucleare, Sezione di Padova, I-35131, Padova, Italy †Brookhaven National Laboratory, Upton, New York 11973, USA ∗∗Department of Physics, New York University, 10003 New York NY, USA Abstract. After a brief review of the muon g 2 status, we discuss hypothetical errors in the Standard Model prediction that could explain the present discrepancy with the− experimental value. None of them looks likely. In particular, an hypothetical + increase of the hadroproduction cross section in low-energy e e− collisions could bridge the muon g 2 discrepancy, but is shown to be unlikely in view of current experimental error estimates. If, nonetheless, this turns out to− be the explanation of the discrepancy, then the 95% CL upper bound on the Higgs boson mass is reduced to about 130 GeV which, in conjunction with the experimental 114.4 GeV 95% CL lower bound, leaves a narrow window for the mass of this fundamental particle. Keywords: Muon anomalous magnetic moment, Standard Model Higgs boson PACS: 13.40.Em, 14.60.Ef, 12.15.Lk, 14.80.Bn SM 11 INTRODUCTION aµ = 116591778(61) 10− . The difference with the EXP× 11 experimental value aµ = 116592080(63) 10− [1] The anomalousmagnetic momentof the muon, aµ ,isone EXP SM 11 × is ∆aµ = aµ aµ =+302(88) 10− , i.e., 3.4σ (all of the most interesting observables in particle physics. errors were added− in quadrature).× Similar discrepan- Indeed, as each sector of the Standard Model (SM) con- HLO cies are found employing the aµ values reported in tributes in a significant way to its theoretical prediction, Refs.
    [Show full text]
  • Arxiv:2009.05616V2 [Hep-Ph] 18 Oct 2020 ± ± Bution from the Decays K → Π A2π (Considered in [1]) 2 0 0 Mrα Followed by the Decay A2π → Π Π [7]
    Possible manifestation of the 2p pionium in particle physics processes Peter Lichard Institute of Physics and Research Centre for Computational Physics and Data Processing, Silesian University in Opava, 746 01 Opava, Czech Republic and Institute of Experimental and Applied Physics, Czech Technical University in Prague, 128 00 Prague, Czech Republic 0 We suggest a few particle physics processes in which excited 2p pionium A2π may be observed. They include the e+e− ! π+π− annihilation, the V 0 ! π0`+`− and K± ! π±`+`− (` = e; µ) decays, and the photoproduction of two neutral pions from nucleons. We analyze available exper- imental data and find that they, in some cases, indicate the presence of 2p pionium, but do not provide definite proof. I. INTRODUCTION that its quantum numbers J PC = 1−− prevent it from decaying into the positive C-parity π0π0 and γγ states. The first thoughts about an atom composed of a pos- It must first undergo the 2p!1s transition to the ground state. The mean lifetime of 2p pionium itive pion and a negative pion (pionium, or A2π in the present-day notation) appeared almost sixty years ago. τ = 0:45+1:08 × 10−11 s: (1) Uretsky and Palfrey [1] assumed its existence and ana- 2p −0:30 lyzed the possibilities of detecting it in the photoproduc- is close to the value which comes for the π+π− atom tion off hydrogen target. Up to this time, such a process assuming a pure Coulomb interaction [8]. After reaching has not been observed. They also hypothesized about the 0 0 the 1s state, a decay to two π s quickly follows: A2π ! possibility of decay K+ ! π+A , which has recently 0 0 2π A2π + γ ! π π γ.
    [Show full text]
  • Sub Atomic Particles and Phy 009 Sub Atomic Particles and Developments in Cern Developments in Cern
    1) Mahantesh L Chikkadesai 2) Ramakrishna R Pujari [email protected] [email protected] Mobile no: +919480780580 Mobile no: +917411812551 Phy 009 Sub atomic particles and Phy 009 Sub atomic particles and developments in cern developments in cern Electrical and Electronics Electrical and Electronics KLS’s Vishwanathrao deshpande rural KLS’s Vishwanathrao deshpande rural institute of technology institute of technology Haliyal, Uttar Kannada Haliyal, Uttar Kannada SUB ATOMIC PARTICLES AND DEVELOPMENTS IN CERN Abstract-This paper reviews past and present cosmic rays. Anderson discovered their existence; developments of sub atomic particles in CERN. It High-energy subato mic particles in the form gives the information of sub atomic particles and of cosmic rays continually rain down on the Earth’s deals with basic concepts of particle physics, atmosphere from outer space. classification and characteristics of them. Sub atomic More-unusual subatomic particles —such as particles also called elementary particle, any of various self-contained units of matter or energy that the positron, the antimatter counterpart of the are the fundamental constituents of all matter. All of electron—have been detected and characterized the known matter in the universe today is made up of in cosmic-ray interactions in the Earth’s elementary particles (quarks and leptons), held atmosphere. together by fundamental forces which are Quarks and electrons are some of the elementary represente d by the exchange of particles known as particles we study at CERN and in other gauge bosons. Standard model is the theory that laboratories. But physicists have found more of describes the role of these fundamental particles and these elementary particles in various experiments.
    [Show full text]
  • Relationship of Pionium Lifetime with Pion Scattering Lengths In
    RELATIONSHIP OF PIONIUM LIFETIME WITH PION SCATTERING LENGTHS IN GENERALIZED CHIRAL PERTURBATION THEORY H. SAZDJIAN Groupe de Physique Th´eorique, Institut de Physique Nucl´eaire, Universit´eParis XI, F-91406 Orsay Cedex, France E-mail: [email protected] The pionium lifetime is calculated in the framework of the quasipotential-constraint theory approach, including the sizable electromagnetic corrections. The framework of generalized chiral perturbation theory allows then an analysis of the lifetime value as a function of the ππ S-wave scattering lengths with isospin I = 0, 2, the latter being dependent on the quark condensate value. The DIRAC experiment at CERN is expected to measure the pionium lifetime with a 10% accuracy. The pionium is an atom made of π+π−, which decays under the effect of strong interactions into π0π0. The physical interest of the lifetime is that it gives us information about the ππ scattering lengths. The nonrelativistic formula of the lifetime was first obtained by Deser et al. 1: 0 2 2 1 16π 2∆mπ (a0 − a0) 2 =Γ0 = 2 |ψ+−(0)| , ∆mπ = mπ+ − mπ0 , (1) τ0 9 s mπ+ mπ+ where ψ+−(0) is the wave function of the pionium at the origin (in x-space) 0 2 and a0, a0, the S-wave scattering lengths with isospin 0 and 2, respectively. The evaluation of the relativistic corrections to this formula can be done in a systematic way in the framework of chiral perurbation theory (χPT ) 2, in the presence of electromagnetism 3. There arise essentially two types of correction. arXiv:hep-ph/0012228v1 18 Dec 2000 (i) The pion-photon radiative corrections, which are similar to those met in conventional QED.
    [Show full text]
  • A Pionic Hadron Explains the Muon Magnetic Moment Anomaly
    A Pionic Hadron Explains the Muon Magnetic Moment Anomaly Rainer W. Schiel and John P. Ralston Department of Physics and Astronomy University of Kansas, Lawrence, KS 66045 Abstract A significant discrepancy exists between experiment and calcula- tions of the muon’s magnetic moment. We find that standard formu- las for the hadronic vacuum polarization term have overlooked pio- + nic states known to exist. Coulomb binding alone guarantees π π− states that quantum mechanically mix with the ρ meson. A simple 2-state mixing model explains the magnetic moment discrepancy for 2 a mixing angle of order α 10− . The relevant physical state is pre- ∼ + dicted to give a tiny observable bump in the ratio R( s ) of e e− an- nihilation at a low energy not previously searched. The burden of proof is reversed for claims that conventional physics cannot explain the muon’s anomalous moment. 1. Calculations of the muon’s magnetic moment do not currently agree arXiv:0705.0757v2 [hep-ph] 1 Oct 2007 with experiment. The discrepancy is of order three standard deviations and quite important. Among other things, uncertainties of the anomalous moment feed directly to precision tests of the Standard Model, including the Higgs mass, as well as providing primary constraints on new physics such as supersymmetry. In terms of the Land´e g factor, the “anomaly” aµ = ( g 2 )/2 experimentally observed in muons has become the quintessen- tial precision− test of quantum electrodynamics ( QED ). The current world average for aµ is [1, 2]: experimental 10 a = ( 11659208.0 6.3 ) 10− . µ ± × 1 The Standard Model theoretical prediction [3] for aµ is theory 10 a = ( 11659180.4 5.1 ) 10− .
    [Show full text]
  • Decay Widths and Energy Shifts of Ππ and Πk Atoms
    Physics Letters B 587 (2004) 33–40 www.elsevier.com/locate/physletb Decay widths and energy shifts of ππ and πK atoms J. Schweizer Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland Received 20 January 2004; accepted 2 March 2004 Editor: W.-D. Schlatter Abstract + − ± ∓ We calculate the S-wave decay widths and energy shifts for π π and π K atoms in the framework of QCD + QED. The evaluation—valid at next-to-leading order in isospin symmetry breaking—is performed within a non-relativistic effective field theory. The results are of interest for future hadronic atom experiments. 2004 Published by Elsevier B.V. PACS: 03.65.Ge; 03.65.Nk; 11.10.St; 12.39.Fe; 13.40.Ks Keywords: Hadronic atoms; Chiral perturbation theory; Non-relativistic effective Lagrangians; Isospin symmetry breaking; Electromagnetic corrections 1. Introduction [4–6] and with the results from other experiments [7]. Particularly interesting is the fact that one may deter- × Nearly fifty years ago, Deser et al. [1] derived the mine in this manner the nature of the SU(2) SU(2) formulae for the decay width and strong energy shift spontaneous chiral symmetry breaking experimentally of pionic hydrogen at leading order in isospin symme- [8]. New experiments are proposed for CERN PS and try breaking. Similar relations also hold for π+π− [2] J-PARC in Japan [9]. In order to determine the scat- and π−K+ atoms, which decay predominantly into tering lengths from such experiments, the theoretical 2π0 and π0K0, respectively. These Deser-type rela- expressions for the decay width and the strong en- tions allow to extract the scattering lengths from mea- ergy shift must be known to an accuracy that matches surements of the decay width and the strong energy the experimental precision.
    [Show full text]
  • Possible Manifestation of the 2P Pionium in Particle Physics Processes
    PHYSICAL REVIEW D 102, 073004 (2020) Possible manifestation of the 2p pionium in particle physics processes Peter Lichard Institute of Physics and Research Centre for Computational Physics and Data Processing, Silesian University in Opava, 746 01 Opava, Czech Republic and Institute of Experimental and Applied Physics, Czech Technical University in Prague, 128 00 Prague, Czech Republic (Received 11 September 2020; accepted 29 September 2020; published 16 October 2020) 0 We suggest a few particle physics processes in which excited 2p pionium A2π may be observed. They include the eþe− → πþπ− annihilation, the V0 → π0lþl− and KÆ → πÆlþl− (l ¼ e, μ) decays, and the photoproduction of two neutral pions from nucleons. We analyze available experimental data and find that they, in some cases, indicate the presence of 2p pionium, but do not provide definite proof. DOI: 10.1103/PhysRevD.102.073004 I. INTRODUCTION The DIRAC collaboration recently discovered [8] so- πþπ− The first thoughts about an atom composed of a positive called long-lived atoms. These objects are apparently excited 2p states of the ground-state pionium A2π. The pion and a negative pion (pionium, or A2π in the present- day notation) appeared almost sixty years ago. Uretsky discovery was enabled by modifying the original DIRAC and Palfrey [1] assumed its existence and analyzed the setup by adding a Pt foil downstream of the production Be possibilities of detecting it in the photoproduction off target. The breakup of the long-lived states happened in that hydrogen target. Up to this time, such a process has not foil, placed at a distance of 96 mm behind the target.
    [Show full text]
  • Jhep02(2018)125
    Published for SISSA by Springer Received: December 11, 2017 Revised: February 7, 2018 Accepted: February 9, 2018 Published: February 20, 2018 Non-resonant and electroweak NNLO correction to JHEP02(2018)125 the e+e− top anti-top threshold M. Beneke,a A. Maier,b T. Rauhb and P. Ruiz-Femen´ıac aPhysik Department T31, Technische Universit¨atM¨unchen, James-Franck-Straße 1, 85748 Garching, Germany bIPPP, Department of Physics, University of Durham, Durham, DH1 3LE, U.K. cDepartamento de F´ısica Te´orica and Instituto de F´ısica Te´orica UAM-CSIC, Universidad Aut´onomade Madrid, E-28049 Madrid, Spain E-mail: [email protected], [email protected], [email protected], [email protected] Abstract: We determine the NNLO electroweak correction to the e+e− b¯bW +W −X ! production cross section near the top-pair production threshold. The calculation includes non-resonant production of the final state as well as electroweak effects in resonant top anti-top pair production with non-relativistic resummation, and elevates the theoretical prediction to NNNLO QCD plus NNLO electroweak accuracy. We then study the impact of the new contributions on the top-pair threshold scan at a future lepton collider. Keywords: Effective Field Theories, Heavy Quark Physics, Perturbative QCD, Quark Masses and SM Parameters ArXiv ePrint: 1711.10429 Open Access, c The Authors. https://doi.org/10.1007/JHEP02(2018)125 Article funded by SCOAP3. Contents 1 Introduction1 2 Setup of the computation3 2.1 Resonant and non-resonant separation in unstable particle
    [Show full text]
  • DIRAC Latest Results
    DIRAC latest results Mikhail Zhabitsky on behalf of the DIRAC collaboration[1] Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, RU141980, Russia The goal of the DIRAC experiment at CERN (PS212) is to measure the π+π− atom lifetime with 10% precision. Such a measurement would yield a precision of 5% on the value of the S-wave ππ scattering lengths combination |a0 − a2|. Based on part of the collected data we present a first result on the +0.49 × −15 lifetime, τ = 2.91 −0.62 10 s, and discuss the major systematic errors. | − | +0.033 −1 This lifetime corresponds to a0 a2 =0.264 −0.020 mπ . This article is a short version of the work [2]. 1 Introduction The aim of the DIRAC experiment at CERN [3] is to measure the lifetime of pionium, + − an atom consisting of a π and a π meson (A2π). The lifetime is dominated by the charge-exchange scattering process (π+π− → π0π0) 1 and is thus related to the relevant scattering lengths [5]. The partial decay width of the atomic ground state (principal quantum number n = 1, orbital quantum number l = 0) is [4, 6, 7] 1 2 3 2 Γ1S = = α p |a0 − a2| (1 + δ)(1) τ1S 9 0 with τ1S the lifetime of the atomic ground state, α the fine-structure constant, p the π momentum in the atomic rest frame, and a0 and a2 the S-wave ππ scattering lengths for isospin 0 and 2, respectively. The term δ accounts for QED and QCD corrections [7].
    [Show full text]
  • Magnetic Corrections to Π-Π Scattering Lengths in the Linear Sigma Model
    PHYSICAL REVIEW D 97, 056023 (2018) Magnetic corrections to π-π scattering lengths in the linear sigma model † ‡ M. Loewe,1,2,3,* L. Monje,1, and R. Zamora4,5, 1Instituto de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile 2Centre for Theoretical and Mathematical Physics and Department of Physics, University of Cape Town, Rondebosch 7700, South Africa 3Centro Científico Tecnológico de Valparaíso-CCTVAL, Universidad T´ecnica Federico Santa María, Casilla 110-V, Vaparaíso, Chile 4Instituto de Ciencias Básicas, Universidad Diego Portales, Casilla 298-V, Santiago, Chile 5Centro de Investigación y Desarrollo de Ciencias Aeroespaciales (CIDCA), Fuerza A´erea de Chile, Santiago 8020744, Chile (Received 5 January 2018; published 27 March 2018) In this article, we consider the magnetic corrections to π-π scattering lengths in the frame of the linear sigma model. For this, we consider all the one-loop corrections in the s, t, and u channels, associated to the insertion of a Schwinger propagator for charged pions, working in the region of small values of the magnetic field. Our calculation relies on an appropriate expansion for the propagator. It turns out that the leading scattering length, l ¼ 0 in the S channel, increases for an increasing value of the magnetic field, in the isospin I ¼ 2 case, whereas the opposite effect is found for the I ¼ 0 case. The isospin symmetry is valid because the insertion of the magnetic field occurs through the absolute value of the electric charges. The channel I ¼ 1 does not receive any corrections. These results, for the channels I ¼ 0 and I ¼ 2, are opposite with respect to the thermal corrections found previously in the literature.
    [Show full text]
  • “Unmatter,” As a New Form of Matter, and Its Related “Un-Particle,” “Un-Atom,” “Un-Molecule”
    “Unmatter,” as a new form of matter, and its related “un-particle,” “un-atom,” “un-molecule” Florentin Smarandache has introduced the notion of “unmatter” and related concepts such as “unparticle,” “unatom,” “unmolecule” in a manuscript from 1980 according to the CERN web site, and he uploaded articles about unmatter starting with year 2004 to the CERN site and published them in various journals in 2004, 2005, 2006. In short, unmatter is formed by matter and antimatter that bind together. The building blocks (most elementary particles known today) are 6 quarks and 6 leptons; their 12 antiparticles also exist. Then unmatter will be formed by at least a building block and at least an antibuilding block which can bind together. Keywords: unmatter, unparticle, unatom, unmolecule Abstract. As shown, experiments registered unmatter: a new kind of matter whose atoms include both nucleons and anti-nucleons, while their life span was very short, no more than 10-20 sec. Stable states of unmatter can be built on quarks and anti-quarks: applying the unmatter principle here it is obtained a quantum chromodynamics formula that gives many combinations of unmatter built on quarks and anti-quarks. In the last time, before the apparition of my articles defining “matter, antimatter, and unmatter”, and Dr. S. Chubb’s pertinent comment on unmatter, new development has been made to the unmatter topic in the sense that experiments verifying unmatter have been found.. 1. Definition of Unmatter. In short, unmatter is formed by matter and antimatter that bind together. The building blocks (most elementary particles known today) are 6 quarks and 6 leptons; their 12 antiparticles also exist.
    [Show full text]