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Matter-Antimatter Oscillations

Matter-Antimatter Oscillations. Matthew Herndon, October 2006 University of Wisconsin Wayne State University Physics Colloquium. Introduction to flavor physics Tevatron and CDF B s Oscillations Conclusion. BEACH 04. J. Piedra. 1. The Standard Model.

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Matter-Antimatter Oscillations

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  1. Matter-Antimatter Oscillations Matthew Herndon, October 2006 University of Wisconsin Wayne State University Physics Colloquium • Introduction to flavor physics • Tevatron and CDF • BsOscillations • Conclusion BEACH 04 J. Piedra 1

  2. The Standard Model Weak force is the force of interest today • What is the Standard Model? • Comprehensive theory • Explains the hundreds of common particles: atoms - protons, neutrons and electrons • Explains the interactions between them • Basic building blocks • 6 quarks: up, down… • 6 leptons: electrons… • Bosons: force carrier particles • All common matter particles are composites of the quarks and leptons and interact by exchange of the bosons Wayne State Colloquium M. Herndon 2

  3. If not the Standard Model, What? Standard Model fails to answer many fundamental questions Look for new physics that would explain these mysteries: SUSY, Excited Bosons, Extra Dimensions… • Gravity not a part of the SM • What is the very high energy behaviour? • At the beginning of the universe? • Grand unification of forces? • Dark Matter? • Astronomical observations of indicate that there is more matter than we see • Where is the Antimatter? • Why is the observed universe mostly matter? • Standard Model predictions validated to high precision, however Wayne State Colloquium M. Herndon 3

  4. Searches For New Physics Tevatron is a flavor factory allowing study of rare processes such as matter-antimatter oscillations • How do you search for new physics at a collider? • Direct searches for production of new particles • Particle-antiparticle annihilation • Example: the top quark • Indirect searches for evidence of new particles • Within a complex process new particles can occur virtually • Tevatron is at the energy frontier and a data volume frontier: 2 billion events on tape • So much data that we can look for some very unusual processes • Where to look • Many weak flavor physics processes are very low probability • Look for enhancements from other low probability processes – Non Standard Model Wayne State Colloquium M. Herndon 4

  5. A Little History d s Rich ground for studying new physics K0 • Everything started with kaons • Flavor physics is the study of quarks • Our tool is the bound states of quarks • Kaon: Discovered using a cloud chamber in 1947 by Rochester and Butler • Could decay to pions and had a very long lifetime: 10-10 sec • Bound state of up or down quarks with with a new particle: the strange quark! • Needed the weak force to understand it’s interactions • Neutral kaons were some of the most interesting kaons Wayne State Colloquium M. Herndon 5

  6. Physics of Neutral Mesons Weak force violated C and P, thought to conserve CP • New physics(at the time) of neutral particles and antiparticles • K0 and K0 • Interacted differently with weak and strong force. Different eigenstates • Strong force quark eigenstates: K0 and K0 • Weak force mass and CP eigenstates: K0S and K0L • The Schrödinger equation • H not diagonal • K0 and K0not mass eigenstates - - - Wayne State Colloquium M. Herndon 6

  7. Physics of Neutral Mesons • Treat the particle and anti-particle as one two state system (Gell-Mann, Pais) • New states mass eigenstates • Weak force mass and CP eigenstates: K0S and K0L • m = 2M12 mass difference • But we’ve seen this type of system before Wayne State Colloquium M. Herndon 7

  8. Classical Analogue Energy Eigenstates: Normal Modes An oscillation or mixing from one state to the other • Coupled spring system • Start the system with one spring moving and over time it will evolve to a state where the other spring is moving. Wayne State Colloquium M. Herndon 8

  9. Oscillations m is the coupling strength and gives the oscillation frequency - A K0 component exists! • Time dependence • Given a pure K0 state at t = 0 • Then at time t Wayne State Colloquium M. Herndon 9

  10. Why? K0 K0 The Weak force is the cause! • The flavor changing weak interaction is necessary to get from K0 to K0 • The weak force provides the coupling between the states that leads to the oscillations • Also the CP eigenstates KS and KL are not changed by the weak force making them the weak force eigenstates - Wayne State Colloquium M. Herndon 10

  11. Neutral Kaons PR 103, 1901 (1956) 1964: CP Violation Observed 1956: CP Eigenstates Observed 1954: Mixing Predicted 1957: Mixing Observed 840 MHz 1980 Nobel Prize Wayne State Colloquium M. Herndon 11

  12. CKM Physics CP violating phase Also in higher order terms Unitarity relationship for b quarks • Our knowledge of the flavor physics can be expressed in the CKM matrix • Translation between strong and weak eigenstantes • Sets magnitude of flavor changing decays: Strange type kaons type type pions • Several unitarity relationships to preserve probability • b quark relationship the most interesting • Largest CP violating parameter • Best place to look for explanations for mater-antimatter asymmetry Wayne State Colloquium M. Herndon 12

  13. Bs and CKM Physics Most poorly understood side of the triangle • B quark unitarity relationship • Can be expressed as triangle in the complex plane • Mixing strength set by Vts parameter Pierini, et al., Wayne State Colloquium M. Herndon 13

  14. New Physics and the Bs Meson Z' sm value Many possibilities for new physics in the Bs system • Look at processes that are suppressed in the SM • Bs Oscillations a.k.a Mixing • SM: Loop level box diagram: Extra weak vertices lead to a suppression • Oscillation frequency can be calculated using electroweak SM physics and lattice QCD • NP can enhance the oscillation process, higher frequencies Harnik et al., Phys. Rev. D 69 094024, 2004 - Barger et al., PL B596 229, 2004 Wayne State Colloquium M. Herndon 14

  15. Neutral B Mesons d s b b First evidence for the Bs meson - Also could tell it oscillated fast! 79 GHz ?? • The B0 and Bs meson • Very interesting place to look for new physics(in our time) Higgs physics couples to mass so B mesons are interesting • Same program: Oscillations , CP violation • First evidence for B meson oscillations How the Bs meson was found • 1987: UA1 Integrated mixing measurement • : Compare charges of leptons from two B decays: opposite(unmixed) same(mixed) • 1987: Argus measured B0 meson mixing frequency • UA1 and Argus measurements disagreed! - Wayne State Colloquium M. Herndon 15

  16. Bs Oscillations ms > 14.4 ps-1 95% CL expected limit (sensitivity) Run 2 Tevatron and CDF built to meet this challenge > 2.3 THz • With the first evidence of the Bs meson we knew it oscillated fast. • How fast has been a challenge for a generation of experiments. Amplitude method: Fourier scan for the mixing frequency Wayne State Colloquium M. Herndon 16

  17. The Rival: DØ Results Another tantalizing hint! Limits: 17-21ps-1 @90CL PRL 97, 021802 2006 Wayne State Colloquium M. Herndon 17

  18. The Tevatron Bs physics benefits from more data - • 1.96TeV pp collider • Excellent performance and improving each year • Record peak luminosity in 2006: 2.4x1032sec-1cm-2 • Average beam crossing 1.7MHz • CDF Integrated Luminosity • ~1fb-1 with good run requirements through 2005 • All critical systems operating including silicon • Doubled data in 2005, predicted to double again in 2006 Wayne State Colloquium 18

  19. The CDF Detector EXCELLENT TRACKING: MASS and VERTEX RESOLUTION Bs Mixing analysis uses more of the capabilities of the CDF detector than any other analysis to date • CDF Tracker • 8 layer , 90cm long, rL00 =1.3 - 1.6cm, ~1 million channel solid state device! • 96 layer drift chamber 44 to 132cm • Dedicated systems for electron and muon finding • Particle Identification • Time of Flight • dE/dx in drift chamber Wayne State Colloquium M. Herndon 19

  20. The Real CDF Detector Wisconsin Colloquium M. Herndon 20

  21. The Trigger 1 Billion B and Charm Events served TRIGGERS ARE CRITICAL • Hadron collider: high production rate of B hadrons • QCD Backgrounds ~ 4 orders of magnitude higher • The solution: a displaced track trigger: trigger on long B lifetime • Find tracks of interest at 1.7MHz • Read out and interpret our silicon detector at 25KHz Wayne State Colloquium M. Herndon 21

  22. Bs Mixing: Overview - • Measurement of the rate of conversion from matter to antimatter: Bs Bs • Determine b meson flavor at production, how long it lived, and flavor at decay to see if it changed! tag Bs p(t)=(1 ± D cos mst) Wayne State Colloquium M. Herndon 22

  23. Bs Mixing: A Real Event Precision measurement of Positions by our silicon detector Charge deposited particles in our drift chamber Momentum from curvature in magnetic field Hits in muon system B flight distance • CDF event display of a mixing event Bs Ds-+, where Ds--,   K+K- Wayne State Colloquium M. Herndon 23

  24. Bs Mixing: Signals • Fully reconstructed decays: Bs Ds-+(2), where Ds--, K*K-, 3 • Partially reco. hadronic decays: Bs Ds-*+and Bs Ds-+, where Ds-* Ds-,+ +0/ • Semileptonic decays: Bs Ds-l+X, where l = e, • Identified using kinematic, lifetime and PID information Wayne State Colloquium M. Herndon 24

  25. More Signals Only experiment with large samples of fully reconstructed events Also largest sample of semileptonic events Wayne State Colloquium M. Herndon 25

  26. Bs Mixing: Flavor Tagging As if we only had this percentage of correctly tagged events • OST: Opposite side tags Jet with b vertex, kaon and lepton tags • SST: Same side tag: Kaon PID and kinematic information • Employ two techniques to get maximum performance • Identify situations in which tagger works best and weight these events more highly: Example a high momentum lepton is more likely a lepton from semileptonic B decay and correctly identifies the flavor. • Use situations in which multiple taggers give flavor information. • Taggers calibrated in data where possible • OST tags calibrated using B+ • SST calibrated using MC and kaon finding performance validated in data Wayne State Colloquium M. Herndon 26

  27. Bs Mixing: Proper Time Resolution • Measurement critically dependent on proper time resolution • Full reconstructed events have excellent proper time resolution • Semileptonic events have worse resolution • Momentum necessary to convert from decay length to proper time Wayne State Colloquium M. Herndon 27

  28. Bs Mixing: Results March 2005 April 2006: Use 1fb-1 Data Nov 2005: Add Ds-3 and lower momentum Ds-l+ March 2006: Add L00 and SST Wayne State Colloquium 28

  29. Example Improvement Expected CDF Sensitivity A Without L00 Improved time resolution by 20%! With L00 was able to reach 3 95% CL sensitivity 3 sensitivity With L00 ms • Including L00 • Silicon sensors mounted directly on the beam vacuum pipe as close as possible to interaction region - Sensors have to be radiation damage resistant • Used CMS prototype sensors - half a dozen different types - donated for free • Detector very difficult to calibrate for physics Wayne State Colloquium M. Herndon 29

  30. Bs Mixing: Results 0.2% is >3 evidence Not good enough yet! PRL 97, 062003 2006 • Add PID to selection: Many kaons in decay chains • Take advantage of tagger correlations Wayne State Colloquium M. Herndon 30

  31. Bs Mixing: Results A >5 Observation! Can we see the oscillation? 2.8THz Submitted to PRL Wayne State Colloquium M. Herndon 31

  32. Bs Mixing: CKM Triangle CDF |Vtd| / |Vts| = 0.2060  0.0007 (stat + syst) +0.0081(lat. QCD) -0.0060 ms = 17.77  0.10 (stat)  0.07 (syst) ps-1 32

  33. Bs Oscillations Conclusion One of the major goals of the Tevatron accomplished! |Vtd| / |Vts| = 0.2060  0.0007 (stat + syst) +0.0081(lat. QCD) -0.0060 • 2 decade long quest to measure the Bs Oscillation frequency done • Oscillations observed directly with >5 significance -0.18 ms = 17.77  0.10 (stat)  0.07 (syst) ps-1 Wayne State Colloquium M. Herndon 33

  34. Bs Results - New Physics • Many new physics models that predict observable effects in flavor physics • Consider a SUSY GFV model: general rather than minimal flavor violation • Makes predictions for Non Standard model BF(Bs→μ+μ-) and ms • Basically corrects quark mass terms with squark-gluino loop terms in a general way • Size of effects depends on tan and mA hep-ph/0604121 Wayne State Colloquium M. Herndon 34 M. Herndon

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