BEACH 04J. Piedra1 Matter-Antimatter Oscillations Introduction to flavor physics Tevatron and CDF B s Oscillations Conclusion Matthew Herndon, October 2006 University of Wisconsin Wayne State University Physics Colloquium

2 The Standard Model 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 M. HerndonWayne State Colloquium Weak force is the force of interest today

3 If not the Standard Model, What? Standard Model predictions validated to high precision, however Look for new physics that would explain these mysteries: SUSY, Excited Bosons, Extra Dimensions… M. Herndon 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 fails to answer many fundamental questions Wayne State Colloquium

4 Searches For New Physics 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 a flavor factory allowing study of rare processes such as matter-antimatter oscillations M. Herndon 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

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: sec 5 A Little History Rich ground for studying new physics 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 s d K0K0 M. HerndonWayne State Colloquium

6 Physics of Neutral Mesons M. Herndon Weak force violated C and P, thought to conserve CP New physics(at the time) of neutral particles and antiparticles K 0 and K 0 Interacted differently with weak and strong force. Different eigenstates Strong force quark eigenstates: K 0 and K 0 Weak force mass and CP eigenstates: K 0 S and K 0 L The Schrödinger equation H not diagonal K 0 and K 0 not mass eigenstates Wayne State Colloquium

7 Physics of Neutral Mesons New states mass eigenstates Weak force mass and CP eigenstates: K 0 S and K 0 L  m = 2M 12 mass difference But we’ve seen this type of system before M. Herndon Treat the particle and anti-particle as one two state system (Gell-Mann, Pais) Wayne State Colloquium

8 Classical Analogue M. Herndon 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. Energy Eigenstates: Normal Modes An oscillation or mixing from one state to the other Wayne State Colloquium

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

10 Why? M. Herndon The flavor changing weak interaction is necessary to get from K 0 to K 0 The weak force provides the coupling between the states that leads to the oscillations Also the CP eigenstates K S and K L are not changed by the weak force making them the weak force eigenstates K0K0 K0K0 - The Weak force is the cause! Wayne State Colloquium

11 Neutral Kaons 1964: CP Violation Observed PR 103, 1901 (1956) 1954: Mixing Predicted 1956: CP Eigenstates Observed1957: Mixing Observed 1980 Nobel Prize 840 MHz M. HerndonWayne State Colloquium

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 12 CKM Physics Unitarity relationship for b quarks CP violating phase Also in higher order terms M. Herndon 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

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

14 New Physics and the B s Meson Look at processes that are suppressed in the SM B s 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 , Barger et al., PL B , 2004 M. Herndon Z' sm value Many possibilities for new physics in the B s system Wayne State Colloquium

The B 0 and B s 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 15 Neutral B Mesons First evidence for B meson oscillations How the B s meson was found 1987: UA1 Integrated mixing measurement  : Compare charges of leptons from two B decays: opposite(unmixed) same(mixed) 1987: Argus measured B 0 meson mixing frequency UA1 and Argus measurements disagreed! b d b s - First evidence for the B s meson - Also could tell it oscillated fast! M. Herndon 79 GHz ?? Wayne State Colloquium

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

17 The Rival: DØ Results Key FeaturesResult Sen: 95%CL16.5ps -1 Sen:  A -1 ) 0.7 A/  A 1.6 Prob. Fluctuation8% Peak value:  m s 19ps -1 Limits: 17-21ps M. Herndon PRL 97, Another tantalizing hint! Wayne State Colloquium

1.96TeV pp collider Excellent performance and improving each year Record peak luminosity in 2006: 2.4x10 32 sec -1 cm -2 Average beam crossing 1.7MHz 18 The Tevatron 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 B s physics benefits from more data Wayne State Colloquium

CDF Tracker 8 layer, 90cm long, r L00 = cm, ~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 19 The CDF Detector EXCELLENT TRACKING: MASS and VERTEX RESOLUTION M. Herndon B s Mixing analysis uses more of the capabilities of the CDF detector than any other analysis to date Wayne State Colloquium

20 The Real CDF Detector M. HerndonWisconsin Colloquium

21 The Trigger 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 TRIGGERS ARE CRITICAL 1 Billion B and Charm Events served M. HerndonWayne State Colloquium

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

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

24 B s Mixing: Signals M. Herndon Fully reconstructed decays: B s  D s -  + (2  ), where D s -   -, K*K -, 3  Partially reco. hadronic decays: B s  D s -*  + and B s  D s -  +, where D s -*  D s - ,  +   +  0 /  Semileptonic decays: B s  D s - l + X, where l = e,  DecayCandidates B s  D s  (2  ) 5600 B s  D s -*  +, B s  D s -  B s  D s lX61,500 Identified using kinematic, lifetime and PID information Wayne State Colloquium

25 More Signals M. Herndon DecayCandidates B s  D s  (2  ) 5600 B s  D s -*  +, B s  D s -  B s  D s lX61,500 Only experiment with large samples of fully reconstructed events Also largest sample of semileptonic events Wayne State Colloquium

26 B s Mixing: Flavor Tagging M. Herndon 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 Tag Performance(  D 2 ) OST1.8% SST3.7%(4.8%) As if we only had this percentage of correctly tagged events Wayne State Colloquium

27 B s 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 M. HerndonWayne State Colloquium

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

29 Example Improvement 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 M. Herndon Improved time resolution by 20%! With L00 was able to reach 3  Expected CDF Sensitivity With L00 Without L00 95% CL sensitivity 3  sensitivity  ms AA Wayne State Colloquium

30 B s Mixing: Results M. Herndon Key FeaturesResult Sen: 95%CL25.8ps -1 Sen:  A -1 ) 0.28 A/  A 3.7 Prob. Fluctuation0.2% Peak value:  m s 17.3ps % is >3  evidence PRL 97, Not good enough yet! Add PID to selection: Many kaons in decay chains Take advantage of tagger correlations Wayne State Colloquium

31 B s Mixing: Results M. Herndon Key FeaturesResult Sen: 95%CL31.3ps -1 Sen:  A -1 ) 0.2 A/  A 6 Prob. Fluctuation8x10 -8 Peak value:  m s 17.75ps -1 A >5  Observation! Submitted to PRL Can we see the oscillation? 2.8THz Wayne State Colloquium

CDF 32 B s Mixing: CKM Triangle |V td | / |V ts | =  (stat + syst) (lat. QCD)  m s =  0.10 (stat)  0.07 (syst) ps -1

33 B s Oscillations Conclusion M. Herndon 2 decade long quest to measure the B s Oscillation frequency done Oscillations observed directly with >5  significance |V td | / |V ts | =  (stat + syst) (lat. QCD)  m s =  0.10 (stat)  0.07 (syst) ps -1 One of the major goals of the Tevatron accomplished! Wayne State Colloquium

34 B s Results - New Physics M. Herndon 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(B s →  μ  μ - ) and  m s Basically corrects quark mass terms with squark-gluino loop terms in a general way Size of effects depends on tan  and m A M. Herndon hep-ph/ Wayne State Colloquium