Cpp observation of large cp violation in the neutral b meson system
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The document describes the Belle detector at the KEKB asymmetric-energy collider. It consists of several sub-detectors including a silicon vertex detector to measure decay positions, a drift chamber to reconstruct particle paths, aerogel counters for Cherenkov radiation, time-of-flight counters, CsI crystals for electromagnetic calorimetry, and a KL and muon detection system. The Belle detector is used to fully reconstruct B mesons and observe CP violation by measuring asymmetries in the time intervals between decays of neutral B mesons into CP eigenstates.
Cpp observation of large cp violation in the neutral b meson system
- 1. OBSERVATION OF LARGE CP VIOLATION IN THE NEUTRAL B M ESON SYSTEM PHYSICAL REVIEW LETTERS VOL. 87, Nº9 27 AUG 2001
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- 4. BELLE DETECTOR AT THE KEKB ASYMMETRIC-ENERGY 4
- 5. BELLE SILICON VERTEX DETECTO R 5 a large-solid-angle magnetic spectrometer that consists of a three-layer silicon vertex detector (SVD) the time difference between the two B-meson decays can be determined by measuring the difference of the decay vertex positions. Since the average distance between the two vertices is 200 mm; the vertex detector must be capable of measuring the distance between them with a precision of 100 mm
- 6. CENTRAL DRIFT CHAMBER 6 a 50-layer central drift chamber (CDC) If one also precisely measures the timing of the current pulses of the wires and takes into account that the ions need some time to drift to the nearest wire, one can infer the distance at which the particle passed the wire. This greatly increases the accuracy of the path reconstruction and is known as a drift chamber. The current CDC has 8,464 sense wires and 25,392
- 7. NOVEL CHERENKOV DETECTOR 7 a mosaic of aerogel threshold Cherenkov counters (ACC) Low-refractive-index silica aerogel is a convenient radiator for threshold-type Cherenkov counters. The total volume of aerogel needed for the ACC is about 2.0 m3.
- 8. TIME-OF-FLIGHT SCINTILLATION COUNTERS 8 time-of-flight scintillation counters (TOF) The TOF serves to a) be a fast trigger to the experiment for traversal of a particle across the bore of Cryomagnet and Silicon Tracker, b) measure the particles traversing the detector to a resolution sufficient to distinguish between upward and downward traveling particles and c) measure the absolute charge of the particle. Particles that pass through the scintillators generate photons as they pass through the counter paddles, these events detected by groups of two or three sensitive photomultiplier tubes (PMT) on either end of the detector element, the counter paddles.
- 9. ELECTROMAGNETIC CALORIMETRY : CSI(TL ) SCINTILLATING CRYSTALS 9 An array of CsI(Tl) crystals (ECL) located inside a superconducting solenoid coil that provides a 1.5 T magnetic field.
- 10. KL AND MUON DETECTION SYSTEM, KLM & DETECTOR SOLENOID AND IRON STRUCTURE : IRON FLUX RETURN 10 located outside of the coil is instrumented to detect KL mesons and to identify muons (KLM).
- 11. 11 Leptons, charged pions, and kaons that are not associated with a reconstructed CP eigenstate decay are used to identify the flavor of the accompanying B meson
- 12. B MESON IS FULLY RECONSTRUCTED 12
- 13. 13 The shapes are derived from Monte Carlo(MC) simulations, and the normalization and peak position of signal are allowed to vary
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- 15. ASYMMETRY IN THE DISTRIBUTION OF THE TIME INTERVALS BETWEEN THE TWO B MESON DECAY POINTS 15
- 16. 16 The curves are the results of the fit applied separately to the individual data samples
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Editor's Notes
- #2: Contexto O efeito do transformação entre partículas em antipartículas, a assim chamada conjugação de C arga, e a inversão das coordenadas espaciais, a P aridade. A violação da simetria CP, ou violação CP, é uma das três condições necessárias para explicar a assimetria matéria-antimatéria observada no Universo. Descoberta do decaimento do mesão neutro K valeu a James Cronin e a Val Fitch o Prémio Nobel de Física em 1980.
- #4: Teoria: No modelo padrão das partículas fundamentais, a matriz CKM (matriz de Cabibbo–Kobayashi–Maskawa) é uma matriz unitária que contém informações acerca da probabilidade de mudança de sabor de um quark causada pela interação fraca. Estas informações são essenciais para o entendimento da violação de simetria CP.
- #5: Detectores: The Belle experiment operated at the KEKB accelerator, the world's highest luminosity machine.
- #6: Precise vertex information is useful in reducing the level of such backgrounds in the B %B sample. covers the angular range 23oyo139 where y is the angle from the beam axis. The radii of the three layers are 30; 45:5 and 60:5 mm: Fig. 1 shows the geometrical configuration of the SVD. There are 8/10/14 ladders along f in layers 1/2/3, All the ladders are made of identical double-sided silicon strip detectors (DSSDs) with identical alu minum nitride ceramic hybrid preamplifier cards. Signals from the z strips are routed to the hybrids at the ends of the detector using a double metal layer method; a thin insulator layer whose thickness is about 0:5 mm covers the z strip layer, and over the insulator layer, there is a layer of the metal readout lines which are perpendicular to the z strips. The sensor size is 57:5 33:5 mm2: The strip pitch is 25 mm on the f-side and 42 mm on the z-side. A bias voltage of 75 V is supplied on the nðzÞ-side.
- #7: The CDC detects charged particles using wires. When particles pass through a helium based gas mixture inside the chamber, they ionize the gas molecules, knocking out electrons. An electric field is created by applying high voltage on ‘sense wires’ strung across the chamber. The field causes electrons to accelerate towards the wires. These electrons knock out additional electrons from the gas as they travel. A number of electrons and ions produced move speedily near the sense wire. The sense wire senses the motion and creates a pulse signal. The signal is then sent to the data acquisition (DAQ) system.
- #8: good pion–kaon separation at the momenta range from 100 MeV/c till few GeV/c (provided by a)
- #10: few-percent precision electromagnetic calorimetry (CsI(Tl ) scintillating crystals) allow for many other scientific searches apart from CP-violation.
- #12: Fonte: Meson B In particle physics, B mesons are mesons composed of a bottom antiquark and either an up (B+), down (B0), strange (B0s) or charm quark (B+c). The combination of a bottom antiquark and a top quark is not thought to be possible because of the top quark's short lifetime. The combination of a bottom antiquark and a bottom quark is not a B meson, but rather bottomonium.
- #16: Analise: