DOCSLIB.ORG

Θc Βct Ct N Particle Nβ 1 Nv C

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Θc Βct Ct N Particle Nβ 1 Nv C SectionSection XX TheThe StandardStandard ModelModel andand BeyondBeyond The Top Quark The Standard Model predicts the existence of the TOP quark ⎛ u ⎞ ⎛c⎞ ⎛ t ⎞ + 2 3e ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎝d ⎠ ⎝ s⎠ ⎝b⎠ −1 3 e which is required to explain a number of observations. Example: Absence of the decay K 0 → µ+ µ− W − d µ − 0 0 + − −9 K u,c,t + ν B(K → µ µ )<10 W µ s µ + The top quark cancels the contributions from the u, c quarks. Example: Electromagnetic anomalies This diagram leads to infinities in the f γ theory unless Q = 0 γ f ∑ f f f γ where the sum is over all fermions (and colours) 2 1 ∑Q f = []3×()−1 + []3×3× 3 + [3×3×(− 3 )]= 0 244 f 0 At LEP, mt too heavy for Z → t t or W → tb However, measurements of MZ, MW, ΓZ and ΓW are sensitive to the existence of virtual top quarks b t t t W + W + Z 0 Z 0 Z 0 W t b t b Example: Standard Model prediction Also depends on the Higgs mass 245 The top quark was discovered in 1994 by the CDF experiment at the worlds highest energy p p collider ( s = 1 . 8 TeV ), the Tevatron at Fermilab, US. q b Final state W +W −bb g t W + Mass reconstructed in a − t W similar manner to MW at q LEP, i.e. measure jet/lepton b energies/momenta. mtop = (178 ± 4.3) GeV Most recent result 2005 246 The Standard Model c. 2006 MATTER: Point-like spin ½ Dirac fermions. Fermion Charge/e Mass Electron e− -1 0.511 MeV st 1 Generation Electron neutrino νe 0 0? Down quark d -1/3 0.35 GeV Up quark u +2/3 0.35 GeV Muon µ- -1 0.106 GeV Muon neutrino 0 0? 2nd Generation νµ Strange quark s -1/3 0.5 GeV Charm quark c +2/3 1.5 GeV Tau τ -1 1.8 GeV 3rd Generation Tau neutrino ντ 0 0? Bottom quark b -1/3 4.5 GeV and Top quark t +2/3 178 GeV ANTI-PARTICLES 247 FORCES: Mediated by spin 1 bosons Force Particle(s) Mass Electromagnetic Photon 0 Strong 8 Gluons 0 Weak (CC) W± 80.4 GeV Weak (NC) Z0 91.2 GeV ¾ The Standard Model also predicts the existence of a spin 0 HIGGS BOSON which gives all particles their masses via its interactions. ¾ The Standard Model successfully describes ALL existing particle physics data, with the exception of one ⇒ Neutrino Oscillations ⇒ Neutrinos have mass First indication of physics BEYOND THE STANDARD MODEL 248 Atmospheric Neutrino Oscillations In 1998 the Super-Kamiokande experiment announced convincing evidence for NEUTRINO OSCILLATIONS implying that neutrinos have mass. Cosmic Ray π π → µ ν DOWN π µ π → e ν ν e µ µ µ µ e- e- e- N ν µ UP νµ ν νµ ν ν νµ ν νµ ν Expect ≈ 2 µ e µ e e N ν e Super-Kamiokande results indicate a deficit of νµ from the upwards direction. ¾ Interpreted as ν µ → ν τ OSCILLATIONS ¾ Implies neutrino MIXING and neutrinos have MASS 249 Detecting Neutrinos Neutrinos are detected by observing the lepton produced in CHARGED CURRENT interactions with nuclei. − + e.g. νe + N → e + X ν µ + N → µ + X Size Matters: ¾ Neutrino mean free path in water ~ light-years. ¾ Require very large mass, cheap and simple detectors ¾ Water Cherenkov detection Cherenkov radiation ¾ Light is emitted when a charged particle traverses a dielectric medium ¾ A coherent wavefront forms when the velocity of a charged particle exceeds c/n (n = refractive index) ¾ Cherenkov radiation is emitted in a cone i.e. at fixed angle with respect to Cerenkov the particle. ct ring n Particle θ β c 1 c ct cosϑ = = ν e- C e nv nβ ν e 250 Super-Kamiokande Super-Kamiokande is a water Cherenkov detector sited in Kamioka, Japan ¾ 50,000 tons of water ¾ Surrounded by 11,146, 50 cm diameter, photo-multiplier tubes 251 Example of events: − − νe + N → e + X ν µ + N → µ + X 252 sub-GeV multi-GeV 250 50 DOWN75 e-like e-like e-like > < > 200 pe -like 0.4 GeV/c 40 p 2.5 GeV/c 60 p 2.5 GeV/c θ 150 30 45 100 20 30 50 10 UP 15 0 0 0 300 100Expect 125 µ-like µ-like Partially Contained > ¾ Isotropic (flat) distributions in cosθ 240 pµ -like 0.4 GeV/c 80 100 ¾ N (νµ) ∼ 2 N (νe) 180 60 75 120 40Observe 50 ¾ Deficit of νµ from BELOW 60 20 25 Interpretation 0 0 0 0.61 -1 -0.6 -0.2 0.2 0.6 1 -1 -0.6 -0.2 0.2 0.6 1 -1 -0.6 -0.2 0.2 0.6 1 Θ ¾ νµ→ντ OSCILLATIONSΘ Θ cos cosθ cos cos ¾ Neutrinos have MASS 253 Neutrino Mixing The quark states which take part in the WEAK interaction (d’, s’) are related to the flavour (mass) states (d, s) ′ Weak Eigenstates ⎛d ⎞ ⎛ cosϑC sinϑC ⎞ ⎛d ⎞ Mass Eigenstates ⎜ ⎟ = ⎜ ⎟ ⎜ ⎟ ⎝ s′ ⎠ ⎝− sinϑC cosϑC ⎠ ⎝ s ⎠ ϑC = Cabibbo angle Assume the same thing happens for neutrinos. Consider only the first two generations. ⎛ νe ⎞ ⎛ cosϑ sinϑ⎞ ⎛ ν ⎞ Mass Eigenstates Weak Eigenstates ⎜ ⎟ = ⎜ ⎟ ⎜ 1 ⎟ ⎜ν ⎟ ⎜ ⎟ ⎜ ⎟ ϑ = Mixing angle ⎝ µ ⎠ ⎝− sinϑ cosϑ⎠ ⎝ν2 ⎠ + + ¾ e.g. in π decay produce µ and νµ i.e. the state that couples to the weak interaction. The νµ corresponds to a linear combination of the states with definite mass, ν1 and ν2 νe = +cosϑ ν1 + sinϑν2 ν = −sinϑ ν + cosϑν µ 1 2 254 or expressing the mass eigenstates in terms of the weak eigenstates ν1 = +cosϑ νe − sinϑνµ ν2 = +sinϑ νe + cosϑνµ Suppose a muon neutrino with momentum pv is produced in a WEAK + + decay, e.g. π → µ νµ At t = 0, the wavefunction v v v v ψ()p,t = 0 = νµ (p)(= cosϑν2 p)− sinϑν1 (p) The time dependent parts of the wavefunction are given by v v −iE1 t ν1 (p,t) = ν1 (p)e v v −iE2 t ν2 ()p,t = ν2 (p)e After time t, v v −iE2 t v −iE1 t ψ()p,t = cosϑν2 (p)e − sinϑν1 (p)e v v −iE2 t v v −iE1 t = cosϑ[]sinϑνe ()p + cosϑνµ ()p e − sinϑ[]cosϑνe ()p − sinϑνµ ()p e 2 −iE2 t 2 −iE1 t v −iE2 t −iE1 t v = []cos ϑe + sin ϑe νµ ()p + []sinϑcosϑ()e − e νe ()p v v = cµνµ ()p + ceνe ()p 255 Probability of oscillating into νe 2 2 −iE2 t −iE1 t P()νe = ce = [sinϑcosϑ(e − e )] 1 = sin2 2ϑ()e−iE2 t − e−iE1 t (eiE2 t − eiE1 t ) 4 1 = sin2 2ϑ()2 − ei()E2 −E1 t − e−i()E2 −E1 t 4 2 2 ⎡()E2 − E1 t ⎤ = sin 2ϑsin ⎢ ⎥ ⎣ 2 ⎦ 1 1 ⎛ m2 ⎞ 2 m2 E = p2 + m2 2 = p⎜1+ ⎟ ≈ p + But () ⎜ 2 ⎟ for m << E ⎝ p ⎠ 2p m2 − m2 m2 − m2 E ()p − E ()p ≈ 2 1 ≈ 2 1 2 1 2p 2E 2 2 2 2 ⎡(m2 − m1 )t ⎤ P()νµ → νe = sin 2ϑsin ⎢ ⎥ ⎣ 4E ⎦ 256 Equivalent expression for νµ → ντ 2 2 2 2 ⎡1.27 ()m3 − m2 L⎤ P()νµ → ντ = sin 2ϑsin ⎢ ⎥ ⎣ Eν ⎦ 2 2 2 where L is the distance travelled in km, ∆ m = m 3 − m 2 is the mass 2 difference in (eV) and Eν is the neutrino energy in GeV. Interpretation of Super-Kamiokande Results E =1GeV For ν µ (typical of atmospheric neutrinos) DOWN UP 257 Results are consistent with ν µ → ν τ oscillations: 2 2 −3 2 m3 − m2 ~ 2.5×10 eV sin 2 2θ ≈1 Comments: ¾ Neutrinos almost certainly have mass ¾ Neutrino oscillation only sensitive to mass differences ¾ More evidence for neutrino oscillations Solar neutrinos (SNO experiment) See nuclear physics Reactor neutrinos (KamLand) 2 2 −5 2 suggest m2 − m1 ≈10 eV ¾ IF mass states ν 3 > ν 2 > ν 1 , then m ~ 2.5×10−3 eV ~ 0.05 eV ν3 m ~ 10−5 eV ~ 0.003 eV ν2 258 Problems with the Standard Model The Standard Model successfully describes ALL existing particle physics data (with the exception of neutrino oscillations). BUT: many input parameters: Quark and lepton masses Quark charges 2 Couplings αem , sin ϑW ,αs Quark generation mixing AND: many unanswered questions: ¾ Why so many free parameters ? ¾ Why only 3 generations of quarks and leptons ? ¾ Where does mass come from ? (Higgs boson?) ¾ Why is the neutrino mass so small and the top quark mass so large ? ¾ Why are the charges of the p and e identical ? ¾ What is responsible for the observed matter-antimatter asymmetry ? ¾ How can we include gravity ? etc 259 The Higgs Mechanism The Higgs mechanism introduces a NEW (Higgs) field into the vacuum which interacts with particles that propagate through it. Classical Vacuum Massless particle Boundary conditions at ±∞ Higgs Vacuum Particle induces currents in the Higgs xxx xxx xxx xxx xxx xxx xxx xxx field which modifies the form of the xxx xxx xxx xxx xxx xxx xxx xxx particle wavefunction and hence its xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx propagation. Particle appears to have xxx xxx xxx xxx xxxHiggsxxx xxx Fieldxxx MASS due to interaction. xxx xxx xxx xxx xxx xxx xxx xxx Local boundary conditions. The combined massless particle + Higgs system behaves identically to a MASSIVE particle in a classical vacuum. 260 The Higgs Potential Higgs Potential At HIGH temp, average Higgs field in vacuum is zero. Massless particles.
Load more

Recommended publications
  • The Particle World
    The Particle World ² What is our Universe made of? This talk: ² Where does it come from? ² particles as we understand them now ² Why does it behave the way it does? (the Standard Model) Particle physics tries to answer these ² prepare you for the exercise questions. Later: future of particle physics. JMF Southampton Masterclass 22–23 Mar 2004 1/26 Beginning of the 20th century: atoms have a nucleus and a surrounding cloud of electrons. The electrons are responsible for almost all behaviour of matter: ² emission of light ² electricity and magnetism ² electronics ² chemistry ² mechanical properties . technology. JMF Southampton Masterclass 22–23 Mar 2004 2/26 Nucleus at the centre of the atom: tiny Subsequently, particle physicists have yet contains almost all the mass of the discovered four more types of quark, two atom. Yet, it’s composite, made up of more pairs of heavier copies of the up protons and neutrons (or nucleons). and down: Open up a nucleon . it contains ² c or charm quark, charge +2=3 quarks. ² s or strange quark, charge ¡1=3 Normal matter can be understood with ² t or top quark, charge +2=3 just two types of quark. ² b or bottom quark, charge ¡1=3 ² + u or up quark, charge 2=3 Existed only in the early stages of the ² ¡ d or down quark, charge 1=3 universe and nowadays created in high energy physics experiments. JMF Southampton Masterclass 22–23 Mar 2004 3/26 But this is not all. The electron has a friend the electron-neutrino, ºe. Needed to ensure energy and momentum are conserved in ¯-decay: ¡ n ! p + e + º¯e Neutrino: no electric charge, (almost) no mass, hardly interacts at all.
    [Show full text]
  • First Determination of the Electric Charge of the Top Quark
    First Determination of the Electric Charge of the Top Quark PER HANSSON arXiv:hep-ex/0702004v1 1 Feb 2007 Licentiate Thesis Stockholm, Sweden 2006 Licentiate Thesis First Determination of the Electric Charge of the Top Quark Per Hansson Particle and Astroparticle Physics, Department of Physics Royal Institute of Technology, SE-106 91 Stockholm, Sweden Stockholm, Sweden 2006 Cover illustration: View of a top quark pair event with an electron and four jets in the final state. Image by DØ Collaboration. Akademisk avhandling som med tillst˚and av Kungliga Tekniska H¨ogskolan i Stock- holm framl¨agges till offentlig granskning f¨or avl¨aggande av filosofie licentiatexamen fredagen den 24 november 2006 14.00 i sal FB54, AlbaNova Universitets Center, KTH Partikel- och Astropartikelfysik, Roslagstullsbacken 21, Stockholm. Avhandlingen f¨orsvaras p˚aengelska. ISBN 91-7178-493-4 TRITA-FYS 2006:69 ISSN 0280-316X ISRN KTH/FYS/--06:69--SE c Per Hansson, Oct 2006 Printed by Universitetsservice US AB 2006 Abstract In this thesis, the first determination of the electric charge of the top quark is presented using 370 pb−1 of data recorded by the DØ detector at the Fermilab Tevatron accelerator. tt¯ events are selected with one isolated electron or muon and at least four jets out of which two are b-tagged by reconstruction of a secondary decay vertex (SVT). The method is based on the discrimination between b- and ¯b-quark jets using a jet charge algorithm applied to SVT-tagged jets. A method to calibrate the jet charge algorithm with data is developed. A constrained kinematic fit is performed to associate the W bosons to the correct b-quark jets in the event and extract the top quark electric charge.
    [Show full text]
  • Muon Neutrino Mass Without Oscillations
    The Distant Possibility of Using a High-Luminosity Muon Source to Measure the Mass of the Neutrino Independent of Flavor Oscillations By John Michael Williams [email protected] Markanix Co. P. O. Box 2697 Redwood City, CA 94064 2001 February 19 (v. 1.02) Abstract: Short-baseline calculations reveal that if the neutrino were massive, it would show a beautifully structured spectrum in the energy difference between storage ring and detector; however, this spectrum seems beyond current experimental reach. An interval-timing paradigm would not seem feasible in a short-baseline experiment; however, interval timing on an Earth-Moon long baseline experiment might be able to improve current upper limits on the neutrino mass. Introduction After the Kamiokande and IMB proton-decay detectors unexpectedly recorded neutrinos (probably electron antineutrinos) arriving from the 1987A supernova, a plethora of papers issued on how to use this happy event to estimate the mass of the neutrino. Many of the estimates based on these data put an upper limit on the mass of the electron neutrino of perhaps 10 eV c2 [1]. When Super-Kamiokande and other instruments confirmed the apparent deficit in electron neutrinos from the Sun, and when a deficit in atmospheric muon- neutrinos likewise was observed, this prompted the extension of the kaon-oscillation theory to neutrinos, culminating in a flavor-oscillation theory based by analogy on the CKM quark mixing matrix. The oscillation theory was sensitive enough to provide evidence of a neutrino mass, even given the low statistics available at the largest instruments. J. M. Williams Neutrino Mass Without Oscillations (2001-02-19) 2 However, there is reason to doubt that the CKM analysis validly can be applied physically over the long, nonvirtual propagation distances of neutrinos [2].
    [Show full text]
  • PSI Muon-Neutrino and Pion Masses
    Around the Laboratories More penguins. The CLEO detector at Cornell's CESR electron-positron collider reveals a clear excess signal of photons from rare B particle decays, once the parent upsilon 4S resonance has been taken into account. The convincing curve is the theoretically predicted spectrum. could be at the root of the symmetry breaking mechanism which drives the Standard Model. PSI Muon-neutrino and pion masses wo experiments at the Swiss T Paul Scherrer Institute (PSI) in Villigen have recently led to more precise values for two important physics quantities - the masses of the muon-type neutrino and of the charged pion. The first of these experiments - B. Jeckelmann et al. (Fribourg Univer­ sity, ETH and Eidgenoessisches Amt fuer Messwesen) was originally done about a decade ago. To fix the negative-pion mass, a high-precision crystal spectrometer measured the energy of the X-rays emitted in the 4f-3d transition of pionic magnesium atoms. The result (JECKELMANN 86 in the graph, page 16), with smaller seen in neutral kaon decay. can emerge. Drawing physics conclu­ errors than previous charged-pion CP violation - the disregard at the sions from the K* example was mass measurements, dominated the few per mil level of a invariance of therefore difficult. world average. physics with respect to a simultane­ Now the CLEO group has collected In view of more recent measure­ ous left-right reversal and particle- all such events producing a photon ments on pionic magnesium, a re- antiparticle switch - has been known with energy between 2.2 and 2.7 analysis shows that the measured X- for thirty years.
    [Show full text]
  • Neutrino Vs Antineutrino Lepton Number Splitting
    Introduction to Elementary Particle Physics. Note 18 Page 1 of 5 Neutrino vs antineutrino Neutrino is a neutral particle—a legitimate question: are neutrino and anti-neutrino the same particle? Compare: photon is its own antiparticle, π0 is its own antiparticle, neutron and antineutron are different particles. Dirac neutrino : If the answer is different , neutrino is to be called Dirac neutrino Majorana neutrino : If the answer is the same , neutrino is to be called Majorana neutrino 1959 Davis and Harmer conducted an experiment to see whether there is a reaction ν + n → p + e - could occur. The reaction and technique they used, ν + 37 Cl e- + 37 Ar, was proposed by B. Pontecorvo in 1946. The result was negative 1… Lepton number However, this was not unexpected: 1953 Konopinski and Mahmoud introduced a notion of lepton number L that must be conserved in reactions : • electron, muon, neutrino have L = +1 • anti-electron, anti-muon, anti-neutrino have L = –1 This new ad hoc law would explain many facts: • decay of neutron with anti-neutrino is OK: n → p e -ν L=0 → L = 1 + (–1) = 0 • pion decays with single neutrino or anti-neutrino is OK π → µ-ν L=0 → L = 1 + (–1) = 0 • but no pion decays into a muon and photon π- → µ- γ, which would require: L= 0 → L = 1 + 0 = 1 • no decays of muon with one neutrino µ- → e - ν, which would require: L= 1 → L = 1 ± 1 = 0 or 2 • no processes searched for by Davis and Harmer, which would require: L= (–1)+0 → L = 0 + 1 = 1 But why there are no decays µµµ →→→ e γγγ ? 2 Splitting lepton numbers 1959 Bruno Pontecorvo
    [Show full text]
  • Neutrino-Electron Scattering: General Constraints on Z 0 and Dark Photon Models
    Neutrino-Electron Scattering: General Constraints on Z 0 and Dark Photon Models Manfred Lindner,a Farinaldo S. Queiroz,b Werner Rodejohann,a Xun-Jie Xua aMax-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany bInternational Institute of Physics, Federal University of Rio Grande do Norte, Campus Univer- sitário, Lagoa Nova, Natal-RN 59078-970, Brazil E-mail: [email protected], [email protected], [email protected], [email protected] Abstract. We study the framework of U(1)X models with kinetic mixing and/or mass mixing terms. We give general and exact analytic formulas and derive limits on a variety of U(1)X models that induce new physics contributions to neutrino-electron scattering, taking into account interference between the new physics and Standard Model contributions. Data from TEXONO, CHARM-II and GEMMA are analyzed and shown to be complementary to each other to provide the most restrictive bounds on masses of the new vector bosons. In particular, we demonstrate the validity of our results to dark photon-like as well as light Z0 models. arXiv:1803.00060v1 [hep-ph] 28 Feb 2018 Contents 1 Introduction 1 2 General U(1)X Models2 3 Neutrino-Electron Scattering in U(1)X Models7 4 Data Fitting 10 5 Bounds 13 6 Conclusion 16 A Gauge Boson Mass Generation 16 B Cross Sections of Neutrino-Electron Scattering 18 C Partial Cross Section 23 1 Introduction The Standard Model provides an elegant and successful explanation to the electroweak and strong interactions in nature [1].
    [Show full text]
  • Masses of the Sub-Nuclear Particles Fit Into One Equation
    Masses of the Sub-Nuclear Particles Theodore M. Lach The masses of the quarks and leptons are for the most part a mystery to particle physicists. Currently there seems to be no correlation between the masses of the elementary particles. This paper is an attempt to formulate a theory that would begin to explain the relationship between the sub-nuclear particle masses. A key premise of the Standard Model is that there are 3 and only 3 generations of quarks and leptons. The currently accepted masses of these elementary particles are: (1) Table 1. Generation # 1 Generation # 2 Generation # 3 Up quark = 3 MeV, (1-5) Charmed quark = 1.25+0.1 GeV Top quark = 175 +5 GeV Down quark = 6 MeV Strange quark = 100 MeV Bottom quark = 4.2 GeV (3-9 MeV) (75-170 MeV) + 0.2 GeV Electron = 0.5109989MeV Muon = 105.6583 MeV Tau = 1777.1 MeV The neutrino masses in the standard model are still a hotly debated issue, yet arXiv:nucl-th/0008026 14 Aug 2000 most current references put the upper bound of the three neutrinos at: Table 2. Electron neutrino = 10 ev (5 – 17 ev) Muon neutrino = 270 KeV (200 – 270 KeV) Tau neutrino = 31 MeV (20 – 35 MeV) In an attempt to determine why the quark masses predicted in the CBM (2), Checker Board Model of the nucleus, do not fit into the standard model, I will deviate from the S.M. and assume that my quark masses in table 3 are correct and that there are more than 3 generations.
    [Show full text]
  • Feynman Diagrams (Pdf)
    PRIMARY SCHOOL anti-muon (+1) or anti-electron (+1) or electron (-1) anti-tau (+1) photon (0) muon (-1) anti-electron (+1) or electron (-1) or tau (-1) Dr Maria Pavlidou, Prof Cristina Lazzeroni HIGH SCHOOL anti-muon (……...) or anti-electron (……..) or electron (…….) anti-tau (……...) ………...…... (…...) muon (…….) anti-electron (……...) or electron (…….) or tau (……..) Dr Maria Pavlidou, Prof Cristina Lazzeroni PRIMARY SCHOOL anti-up (-2/3) or anti-down (+1/3) or anti-strange (+1/3) or anti-beauty (+1/3) or anti-top (-2/3) or charm quark (+2/3) anti-charm (-2/3) gluon (0) up (+2/3) or down (-1/3) anti-charm quark (-2/3) or strange (-1/3) or beauty (-1/3) or top (+2/3) or charm (+2/3) Dr Maria Pavlidou, Prof Cristina Lazzeroni HIGH SCHOOL anti-up (……….) or anti-down (……...) or anti-strange (……...) or anti-beauty (……...) or anti-top (……...) or charm quark (……...) anti-charm (……...) ………...…... (…...) up (……...) or down (……...) or anti-charm quark (……..) strange (……...) or beauty (……...) or top (……...) or charm (……...) Dr Maria Pavlidou, Prof Cristina Lazzeroni PRIMARY SCHOOL anti-up (-2/3) or anti-charm (-2/3) muon (-1) W minus (-1) down (-1/3) muon neutrino (0) or strange (-1/3) or beauty (-1/3) Dr Maria Pavlidou, Prof Cristina Lazzeroni HIGH SCHOOL anti-up (……...) or anti-charm (……...) muon (……...) ………...…... (…...) down (……...) muon neutrino (……...) or strange (……...) or beauty (……...) Dr Maria Pavlidou, Prof Cristina Lazzeroni PRIMARY SCHOOL electron neutrino (0) or muon neutrino (0) or tau neutrino (0) tau (-1) Z (0) electron anti-neutrino (0) anti-tau (+1) or muon anti-neutrino (0) or tau anti-neutrino (0) Dr Maria Pavlidou, Prof Cristina Lazzeroni HIGH SCHOOL electron neutrino (……...) or muon neutrino (……...) or tau neutrino (……...) tau (……...) ………….
    [Show full text]
  • ELEMENTARY PARTICLES in PHYSICS 1 Elementary Particles in Physics S
    ELEMENTARY PARTICLES IN PHYSICS 1 Elementary Particles in Physics S. Gasiorowicz and P. Langacker Elementary-particle physics deals with the fundamental constituents of mat- ter and their interactions. In the past several decades an enormous amount of experimental information has been accumulated, and many patterns and sys- tematic features have been observed. Highly successful mathematical theories of the electromagnetic, weak, and strong interactions have been devised and tested. These theories, which are collectively known as the standard model, are almost certainly the correct description of Nature, to first approximation, down to a distance scale 1/1000th the size of the atomic nucleus. There are also spec- ulative but encouraging developments in the attempt to unify these interactions into a simple underlying framework, and even to incorporate quantum gravity in a parameter-free “theory of everything.” In this article we shall attempt to highlight the ways in which information has been organized, and to sketch the outlines of the standard model and its possible extensions. Classification of Particles The particles that have been identified in high-energy experiments fall into dis- tinct classes. There are the leptons (see Electron, Leptons, Neutrino, Muonium), 1 all of which have spin 2 . They may be charged or neutral. The charged lep- tons have electromagnetic as well as weak interactions; the neutral ones only interact weakly. There are three well-defined lepton pairs, the electron (e−) and − the electron neutrino (νe), the muon (µ ) and the muon neutrino (νµ), and the (much heavier) charged lepton, the tau (τ), and its tau neutrino (ντ ). These particles all have antiparticles, in accordance with the predictions of relativistic quantum mechanics (see CPT Theorem).
    [Show full text]
  • What Is a Muon?
    What is a Muon? A muon is a type of subatomic particle. The name is pronounced “myoo-on,” and comes from the Greek letter µ, which we spell “mu” and pronounce “myoo.” A muon is a type of particle very much like an electron. In fact, it is exactly the same as an electron – except heavier. The mass of a muon is 207 times the mass of an electron. You can remember or look up (or take our word for it) that the mass of a proton, by contrast, is about 1,800 times the mass of an electron. So a muon has all the properties of an electron, but is more similar in mass to the big clunkiness (in relative terms) of a proton or other nuclear particle. A muon, however, is not made up of any other particles. It is not a bag of electrons or of anything else, but appears to be its own elementary or fundamental particle. It’s just a heavier version of an ordinary electron. If the existence of the muon seems strange and unnecessary to you, you are in good company. The world-famous physicist I. I. Rabi, when first told of the discovery of the muon, said in response, “Who ordered that?” There’s a good reason why the muon is such an unfamiliar particle: muons are radioactive, and they decay with a half-life of 1.52 microseconds. That’s 1.52 x 10-6 seconds, or 1.52 millionths of a second. Not 5,700 years, like 14C, but 1.52 millionths of a second! Muons don’t stick around long enough for anything ordinary to be made out of them.
    [Show full text]
  • Some Considerations on Neutrinos and on the Measurement of Their Velocity
    Some Considerations on Neutrinos and on the Measurement of their Velocity Giorgio Giacomelli University of Bologna and INFN Section of Bologna [email protected] Provincial Science Conference, Department of Physics and Astronomy(DIFA), Bologna, 11/11/2012 Abstract. In this report are recalled in a simple form some of the main concepts about neutrinos, starting from their discovery and classifying them in the Standard Model of the Microcosm. Then are presented the main natural sources of neutrinos, emphasizing the enormous number of neutrinos in the Universe. Some information on neutrinos produced by nuclear reactors and by particle accelerators are then considered. In the second part is discussed the neutrino beam sent from CERN to Gran Sasso and the measurement of their velocity performed by the OPERA experiment, underlying some errors made, their corrections, and the final results, which represent precision measurements. 1. Introduction The neutrinos are completely outside our every day ordinary experience, and among all the objects present in the Universe are the smallest, the most abundant and the most elusive. They come from all directions of space, and, every second, thousand billions of them traverse us, but their probability of interacting with ordinary matter is extremely small. The very many neutrinos coming from our Sun arrive during the day from the top and during the night from the bottom. The neutrinos are part of the family of the smallest constituents of matter, have zero electric charge and a very small mass. The neutrino was “invented” in 1930 by the german theoretical physicist W. Pauli, in a letter sent to a conference, a short time before going to a “dance party”.
    [Show full text]
  • Direct Measurement of the Top Quark Decay Width in the Muon+Jets Channel Using the CMS Experiment at the LHC
    Vrije Universiteit Brussel Faculteit Wetenschappen en Bio-ingenieurswetenschappen Departement Natuurkunde Direct measurement of the top quark decay width in the muon+jets channel using the CMS experiment at the LHC Lieselotte Moreels Promotor Prof. Dr. Petra Van Mulders Co-promotor Prof. Dr. Jorgen D’Hondt Proefschrift ingediend met het oog op het behalen van de academische graad Doctor in de Wetenschappen April 2018 Doctoral examination commission: Prof. Dr. Nick van Eijndhoven (Vrije Universiteit Brussel, chair ) Prof. Dr. Alberto Mariotti (Vrije Universiteit Brussel, secretary ) Prof. Dr. Petra Van Mulders (Vrije Universiteit Brussel, supervisor ) Prof. Dr. Jorgen D’Hondt (Vrije Universtiteit Brussel, advisor ) Prof. Dr. Dirk Ryckbosch (Universiteit Gent) Dr. Ivan Marchesini (Vrije Universiteit Brussel) Dr. Rebeca Gonzalez Suarez (University of Nebraska, USA) Prof. Dr. Philippe Claeys (Vrije Universiteit Brussel) Cover illustration: Fisheye view of the CMS detector. The barrel (front) and one of the endcaps (back) are connected by the beam pipe. Picture taken from CMS-doc-13419-v1. Cover kindly designed by Isis Van Parijs. ISBN: 978 94 923 1271 6 NUR: 924, 926 c 2018 Lieselotte Moreels All rights reserved. No parts of this book may be reproduced or transmitted in any form or by any means, electronic, mechanical, pho- tocopying, recording, or otherwise, without the prior written permission of the author. Contents Introduction 1 1 The Particle Universe 3 1.1 The Standard Model . .4 1.1.1 Particles and forces . .4 1.1.2 Mathematical framework . .7 1.1.3 Open questions . 10 1.2 The Top Quark Sector . 12 1.2.1 Production and decay . 13 1.2.2 Top quark mass .
    [Show full text]