Matter-Antimatter Transformations at 3 Trillion Hertz Prof. Joseph Kroll University of Pennsylvania Fall 2006

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 2 Executive Summary (1) At the beginning of ‘06 this is what was known at least 3.5 cycles per lifetime

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 3 Executive Summary (2) Measure asymmetry A as a function of proper decay time t “unmixed”: particle decays as particle For a fixed value of  m s, data should yield Amplitude “A” is 1, at the true value of  m s Amplitude “A” is 0, otherwise “mixed”: particle decays as antiparticle

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 4 Start 2006: Published Results on  m s Results from LEP, SLD, CDF I  m s > 14.5 ps -1 95% CL see Amplitude method: H-G. Moser, A. Roussarie, NIM A384 p. 491 (1997)

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 5 March 2006: Result DØ Collaboration 17 <  m s < 21 ps 90% CL 1 st reported direct experimental upper bound Probability “Signal” is random fluctuation is 5% V. M. Abazov et al., Phys. Rev. Lett. Vol. 97, (2006)

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 6 April 2006: Result from the CDF Collaboration Probability “Signal” is random fluctuation is 0.2% Under signal hypothesis: measure  m s V. M. Abulencia et al., Phys. Rev. Lett. Vol. 97, (2006)

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 7 Outline Neutral Weakly Decaying Mesons Neutral Meson Matter-Antimatter Transformations The Weak Interaction History of Flavor Oscillations (Mixing) B Physics at Hadron Colliders Outline of the Measurement Strategy Measuring B 0 s Oscillations at CDF Results & Outlook

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 8 Quarks and Hadrons Quarks: 3 Families Hadrons: colorless combinations of quarks Three colors q q q Mesons: Baryons: Aside: other exotic combinations predicted: e.g., Pentaquarks Electric charge

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 9 Weakly Decaying Neutral Mesons Mass units: m electron = MeV/c 2, m proton = GeV/c MeV/c 2 = 9.11 £ kg

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 10 Neutral Meson Flavor Oscillations (Mixing) Due to phase space suppression: K 0 L very long-lived: 5.2 £ s (K 0 S : £ s) 1954: over 50 years ago

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 11 Long-Lived Neutral Kaon Discovered by Ken Lande et al., (now at Penn) in 1956 Led to discovery of CP Violation in 1964 (Nobel Prize in 1980) BF(K 0 L !  +  - ) = 0.2% Christenson, Cronin, Fitch, Turlay, Phys. Rev. Lett. 13, 138 (1964)

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 12 Neutral Meson Mixing (Continued)

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 13 Neutral B Meson Flavor Oscillations  = 1/  = 1.6 psec Units: [  m] = ~ ps -1. We use ~ =1 and quote  m in ps -1 To convert to eV multiply by £ 10 -4

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 14 The Weak Interaction: Leptons Muon decay:

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 15 Weak Interaction: Quarks & the Cabibbo Angle Pion Decay: Kaon Decay:

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 16 The Cabibbo Angle: = sin  C

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 17 texpoint test

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 18 The Flavor Parameters (CKM Matrix) mass eigenstates ≠ weak eigen. weak mass related by Cabibbo-Kobayashi-Maskawa Matrix V is unitary: V y V = 1Measurements + Unitarity assuming 3 generations PDG: S. Eidelman et al. Phys. Lett. B 592, 1 (2004) Ranges are 90% CL These fundamental parameters must be measured

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 19 Wolfenstein Parametrization Illustrates Hierarchy Original reference: L. Wolfenstein, PRL, 51, p (1983) Reference for this slide: A. Höcker et al., Eur. Phys. J. C21, p. 225 (2001); ibid, hep-ph/ from hep-ph/ Expand matrix in small parameter:  = V us = sin  Cabibbo » £ 3 complex unitary matrix: 3 real & 1 imag. parameters ≡ 3 angles, 1 phase

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 20 B Meson Decay – Predominantly to Charm }{ }{ } Semileptonic (not completely reconstructed – missing p ) Hadronic phase space factor V cb = (41.3 § 1.5) £ Small V cb means Small  Long  (lifetime)

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 21 Small V cb Means Long B Lifetime Nigel Lockyer (Penn), Bill Ford, Jim Jaros2006 APS Panofsky Prize see also E. Fernandez et al. Phys. Rev. Lett (1983) Long B lifetime  possible to see B 0 s particle-antiparticle transitions

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 22 Neutral B Meson Flavor Oscillations Flavor oscillations occur through 2 nd order weak interactions e.g. Same diagrams and formula for  m s for B s except replace “d” with “s” All factors known well except “bag factor” £ “decay constant”  m d = § ps -1 (1%) (PDG 2006) from Lattice QCD calculations – see Okamoto, hep-lat/ From measurement of  m d derive |V * tb V td | 2

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 23 B Meson Flavor Oscillations (cont) If we measure  m s then we would know the ratio  m s /  m d Many theoretical quantities cancel in this ratio, we are left with Ratio measures |V td /V ts | This is why  m s is high priority in Run II Using measured  m d & B masses, expected |V ts /V td | Predict  m s » 18 ps -1 We know what to expect

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 24 Why is this Interesting? Probe of New Physics Supersymmetric particles4 th Generation Additional virtual particles increase  m s Measured value can be used to restrict parameters in models e.g., Harnik et al. Phys. Rev. D (2004) e.g., W. Huo Eur. Phys. J. C (2002)

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 25 Tevatron Performance Key performance number is Integrated Luminosity Cross-section: [  ] = Area Luminosity: [L] = 1/Area 1/time Rate: [  L] = 1/time Integrated Lum. [∫Ldt] = 1/Area Number:  ∫Ldt Collison rate: 2.5 MHz t quark production  = 6pb t quark cm -2 s -1 = 0.6 mHz Typical L = cm -2 s -1 Projected ∫Ldt = 4-8 fb -1 Barn: b = cm 2 pb = cm 2, pb -1 = cm -2 ∫Ldt = 2 fb -1

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 26 Silicon tracking Drift chamber Lumi monitor Hadronic Calorimetry Muon systems Iron shielding Solenoid and TOF Electromagnetic Calorimetry CDF II Front-end elec. & DAQ: 7.6 MHz clock (132 ns)

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 27 CDF II Installation of Silicon Tracking Device Fall 2000 CDF rolls in to collision hall – Winter 2001 At the energy frontier at the Fermilab Tevatron (p-antip) TOF Detector (Penn Electronics) Penn COT Electronics

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 28 B Physics at Hadron Machines Strong interaction produces bb pairs Example of lowest order (LO)  s 2 Example of next leading order (NLO)  s 3 NLO contribution comparable to LO contribution see P. Nason, S. Dawson, R. K. Ellis Nucl. Phys. B273, p. 49 (1988) called “flavor creation” “gluon splitting” “flavor excitation” b pairs produced close in y

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 29 B Physics at Hadron Machines (cont.) b quarks then fragment to B hadrons B factories running on Y(4S) only produce lightest B mesons Hadron colliders (and e + e - colliders running above Y(4S)) produce other B’s fragmentation is hard: B hadron gets large fraction of b quark E Many unique B measurements at hadron colliders e.g.,  m s, B s rare decays, observation B c,  b lifetime

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 30 B Production at Tevatron The inclusive b cross-section is enormous: on the order of 100  b For L = cm -2 s -1 (10 32 )   £ L = 1kHz (10kHz) Much of this not useful (trigger, acceptance, analysis selection criteria) The useful cross-section is order 10  b This is still well above production cross-section at B Factories, Z pole The CDF Collaboration, D. Acosta et al., Phys. Rev. D65, (2002) B factory rate: L = cm -2 s -1   £ L = 10 Hz  £ L » 100 Hz

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 31 Characteristics of B Production and Decay  b large, but  inelastic » 10 3 larger Trigger & analysis strategy: Exploit unique aspects b production & decay UA1 showed it was possible: b !  X, b !  X, b mixing Then CDF fully reconstructed B B - ! J/  K -, J/  !  +  - F. Abe et al., PRL 68, 3403 (1992) CDF “Run 0” 2.6 § 0.2 pb -1

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 32 Experimental Steps for Measuring B s Mixing 1. Extract B 0 s signal – decay mode must identify b-flavor at decay (TTT) Examples: 2. Measure decay time (t) in B rest frame (L = distance travelled) (L00) 3. Determine b-flavor at production “flavor tagging” (TOF) “unmixed” means production and decay flavor are the same “mixed” means flavor at production opposite flavor at decay Flavor tag quantified by dilution D = 1 – 2w, w = mistag probability

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 33 Schematic

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 34 Event Display

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 35 Measuring B s Mixing (cont.) 4. Measure asymmetry these formulas assume perfect resolution for t Asymmetry is conceptual: actually perform likelihood fit to expected “unmixed” and “mixed” distributions

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 36 Measurement of Oscillation What about experimental issues? “Right Sign” “Wrong Sign”

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 37 Realistic Effects flavor tagging power, background displacement resolution momentum resolution mis-tag rate 40%  L) ~ 50  m  p)/p = 5%

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 38 All Effects Together

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 39 1 st Evidence: Time Integrated Mixing:   is the time integrated mixing probability In principle, a measurement of  determines  m - 1 st B d mixing measurements were  measurements -  d = § (PDG 2004) - this does not work for B s :  s = 0.5 (the limit as x !1 ) Inclusive measurements at hadron colliders yield 1987

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 40 Discovery of Neutral B Flavor Oscillations Implications: m top >50 GeV/c 2 Top quark is heavier than expected Ellis, Hagelin, Rudaz, Phys. Lett. B 192, 201 (1987) UA1 1987: Evidence for B 0 & B 0 s mixing Followed up by observation of B 0 mixing by ARGUS: H. Albrecht et al., (25 June 87) Phys. Lett. B 192, 245 (1987)

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 41 State of the Art Measurement of  m d B. Aubert et al. Phys. Rev. Lett. 88, (2002)

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 42 Measuring  m s at CDF: Signal Decay sequence Four charged particles in final state: K + K -  +  - Complete reconstruction:  p B negligable

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 43 Lifetime Measurement production vertex 25  m £ 25  m Decay position Decay time in B rest frame

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 44 Decay Time Resolution = 86 £ s ¼ period for  m s = 18 ps -1 Oscillation period for  m s = 18 ps -1 Maximize sensitivity: use candidate specific decay time resolution Superior decay time resolution gives CDF sensitivity at much larger values of  m s than previous experiments

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 45 B Flavor Tagging We quantify performance with efficiency  and dilution D  = fraction of signal with flavor tag D = 1-2w, w = probability that tag is incorrect (mistag) Statistical error  A on asymmetry A (N is number of signal) statistical error scales with  D 2

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 46 Two Types of Flavor Tags Opposite side Same sideBased on fragmentation tracks or B ** + Applicable to both B 0 and B 0 s − other b not always in the acceptance − Results for B + and B 0 not applicable to B 0 s + better acceptance for frag. tracks than opp. side b Reminder: for limit on  m s must know D Produce bb pairs: find 2 nd b, determine flavor, infer flavor of 1 st b

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 47 Types of Opposite Side Flavor Tags Lepton tags Jet charge tag Kaon tag mistags from Run II: for muons:  D 2 = (0.66 § 0.19)% jet from b (b) has negative (positive) charge on average Run II:  D 2 = (0.419 § 0.024)% expect comparable for elec. low  high D high  low D Largest  D B factories Run II: no useful tag yet (have seen D,  too low) TOF

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 48 Same Side Flavor Tags Based on correlation between charge of fragmentation particle and flavor of b in B meson TOF Critical (dE/dx too) Both due to PENN

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 49 Time of Flight Detector (TOF) 216 Scintillator bars, 2.8 m long, 4 £ 4 cm 2 R=140 cm read out both ends with fine mesh PMT (operates in 1.4 T B field – gain down ~ 400) anticipated resolution  TOF =100 ps (limited by photostatistics) Kaon ID for B physics Measured quantities: s = distance travelled t = time of flight p = momentum Derived quantities: v = s/t m = p/  v

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 50 Recent Penn CDF group Ph. D.s Designed & built electronics for CDF TOF Successfully defends thesis on Charm meson production cross-sections: First PRL from Tevatron Run II Chunhui Chen now PD at Maryland

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 51 Recent Penn CDF Group Ph. D.s Used TOF to measure types of particles produced in association with B mesons. First such results from hadron collider Crucial for B 0 s oscillations Denys Usynin: Now at JP Morgan Contributions to several TOF electronic components & PMT assembly

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 52 Kaons Produced in Vicinity of B’s Larger fraction of Kaons near B 0 s compared to B 0, B +, as expected Ph. D. Thesis, Denys Usynin

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 53 Contributions to CDF Trigger Trigger selects in real time interesting collisions Crucial for successful physics program Kristian Hahn made major contributions to 2 nd Level upgrade Fritz Stabenau spent one year with us working on 2 nd Level upgrade

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 54 Flavor Tagging Summary Opposite-side tags:  D 2 = 1.5% Same-side kaon tag:  D 2 = 4.0% Same-side kaon tag increases effective statistics £ 4 Penn played the lead role in Run I CDF analysis to develop these tags: Ph. D. Thesis, Owen Long Penn played the lead role in proposing and building TOF Measured kaons near B’s: Ph. D. Thesis, Denys Usynin

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 55 Results: Amplitude Scan A/  A = 3.5 Sensitivity 25.3 ps -1

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 56 Results: Amplitude Scan A/  A = 6.1 Sensitivity 31.3 ps -1

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 57 Measured Value of  m s - log(Likelihood) Hypothesis of A=1 compared to A=0

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 58 Measured Value of  m s - log(Likelihood) Hypothesis of A=1 compared to A=0

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 59 Significance: Probability of Fluctuation Probability of random fluctuation determined from data Probability = 0.5% (2.8  ) Below threshold to claim “observation” Continue improving analysis to increase potential significance

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 60 Significance: Probability of Fluctuation Probability of random fluctuation determined from data Probability = 8 £ 10  8  (5.4  ) Have exceeded standard threshold to claim observation 28 of 350 million random trials have L <

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 61

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 62 Determination of |V td /V ts | Previous best result: D. Mohapatra et al. (Belle Collaboration) PRL (2006) CDF

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 63 Summary of CDF Results on B 0 s Mixing First direct measurement of  m s Precision: 2.4% Probability of random fluctuation: 0.5% Most precise measurement of |V td /V ts | All results are preliminary ( 2.76 THz, eV)

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 64 Some Final Words Mixing in Neutral Kaons –led to discovery of violation of combination of fundamental symmetry operations: C & P –CP Violation:necessary condition for matter antimatter asymmetry in Universe. Mixing in B 0 mesons led to possibility of observing CP Violation in another system –validated that SM mechanism for CP Violation is dominant mechanism. The discovery of B 0 mixing pointed to a much heavier top quark: –Results on B 0 s mixing could point to heavier new particles. Establishing B 0 s mixing sets the stage for the next step: –measuring CP asymmetries in B 0 s decays –could produce unambiguous signals of new physics. We are coming to the end of a long story: –a 20 year quest to measure  m s –a tremendous technical achievement –allows precise measurement of fundamental parameters Penn Physicists played a leadership role –in pioneering techniques in Run I –in establishing the measurement as a key goal for the Tevatron in Run II –in contributing to the critical detector elements –in playing a leading role in the data analysis

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 65 Additional Slides for Reference

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 66 Different Parameterizations of CKM Matrix L. L. Chau, W. Y. Keung Phys. Rev. Lett. 53, p (1984) - used by PDG 3 £ 3 complex unitary matrix: 3 real & 1 imag. parameters ≡ 3 angles, 1 phase notation: c ij ´ cos  ij & s ij ´ sin  ij, i, j = 1 st, 2 nd, 3 rd generation Advantages of this parameterization: 1.Satisfies unitarity exactly 2.If  ij = 0, generations i & j decouple 3.If  13 =  23 = 0, 3 rd generation decouples,  12 is Cabibbo angle 4.Same formulation used for lepton mixing matrix U with ( £ diag[e i  1 /2,e i  2 /2, 1 ])

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 67 Wolfenstein Parametrization Illustrates Hierarchy Original reference: L. Wolfenstein, PRL, 51, p (1983) Reference for this slide: A. Höcker et al., Eur. Phys. J. C21, p. 225 (2001); ibid, hep-ph/ valid to O( 6 ) ¼ 0.01%, = V us = sin  Cabibbo » 0.2 Define: from hep-ph/

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 68 Example of B s Oscillations Example of Asymmetry with lots of statistics  m s = 20 ps -1 Illustrated are - tagging reduces statistics dilution reduces amplitude - decay length resolution damps amplitude further - momentum uncertainty damps amplitude more as decay time t increases Large  m s : B s ! D s l no good need fully reconstructed decays e.g., B s ! D s  Figures courtesy M. Jones (Penn/Purdue)

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 69 Some More Detail Aside: Total  D 2 ¼ 30% at the B factories

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 70 Amplitude Scan

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 71 The Unitarity Triangles V is unitarity  geometric representation: triangle in complex plane Im Re V i1 V * k1 V i2 V * k2 V i3 V * k3 There are 6 triangles Kaon UT Beauty UT flat n.b. these triangles are rescaled by one of the sides i = 1 is previous page

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 72 The Beauty Unitary Triangle  of Chau & Keung parametrization is 

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 73 How Do Measurements Constrain Triangle? Figure courtesy of CKM Fitter group: ckmfitter.in2p3.fr – as were all of the formulas on previous slides B 0 flavor oscillations (  m d ) constrains one side How do B 0 s oscillations (  m s ) fit in this picture? Why is  m s considered one of the most important Run II measurements? Aside: a key issue is to pick experimental quantities that can be related to CKM para. without large theory errors

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 74

Fall 2006 Colloquium Joseph Kroll - University of Pennsylvania 75