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Mayda M.Velasco Northwestern University Oct. 1, 2004

40 Years after Discovery of Strangeness, Parity and CP violations – Why are we still working on Kaon Physics?. Mayda M.Velasco Northwestern University Oct. 1, 2004. From the biased point of view from a member of NA48@CERN.

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Mayda M.Velasco Northwestern University Oct. 1, 2004

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  1. 40 Years after Discovery of Strangeness, Parity and CP violations – Why are we still working on Kaon Physics? Mayda M.Velasco Northwestern University Oct. 1, 2004 From the biased point of view from a member of NA48@CERN

  2. In order to put the subject in context, let’s look at the main question of the particle physics community… • Where did the anti-matter go? … What caused the matter-antimatter asymmetry of the Universe? • Can we explain the matter and energy composition of the Universe? • Why are there so many particles? … What causes their masses to be so different? • Where does mass come from? • Do all known forces unify as some large E scale? • Are there extra dimensions of space?  None of the above can be fully answered by the SM 2

  3. qq Nevertheless we have a successful Model Puzzles brought & answered by strange Kaon & Hyperon physics has revealed many aspects of “TODAY’s” Standard Model of Particle Physics  More to come… qqq 3

  4. Original Puzzles from Kaon decays • 1944-47: Strangeness  quark model 4

  5. s u Puzzle #1 -- Strange particles observed:Long lifetimes & Heavy Strangeness - produced by strong interaction - conserved by strong interactions  these strange particles produced in pairs d g s u u d 5

  6. Original Puzzles from Kaon decays • 1944-47: Strangeness  quark model  Basis for QCD  gluon • 1956: Parity violation 6

  7. Invariance under Lorentz transformation implies  CPT invariance • Therefore… big impact on the foundation of the theory, if interactions behave in different ways under: • Charge conjugation(C): reverses the electric charge & all the internal quantum numbers. • Parity (P): space inversion; reversal of the space coordinates. • Time reversal (T): replacing t by -t. This reverses time derivatives like momentum and angular momentum. • Particles and antiparticles have identical masses and lifetimes. This arises from CPT invariance of physical theories and is used experimentally to test CPT. 7

  8. K0 = d s K+ = u s S = +1 • K0 = d s K- = u s S = -1 Puzzle #2 – Parity violating Decays:V-A Theoryof Weak Interactions (WI) • Kaons are mesons (Spin = 0; Parity = -1): • K+ p+p0 P=(-1)(-1) Even  p+p-p+ P=(-1)(-1)(-1) Odd t - q Puzzle • Strangeness not conserved WI Extra confidence in the V-A theory (Spin-Flip)  BR = 63% Helicity suppressed due to low mass of e+  BR = 0.0015% 8

  9. Puzzels from Kaon decays Original Puzzles from Kaon decays • 1944-47: Strangeness  quark model  Basis for QCD • 1956: Parity violation  Chiral nature of weak interactions • 1964: Suppression of FCNC 9

  10. m- m- d d W- W- KL KL nm nm c u _ _ W+ W+ m+ m+ s s Puzzle #3 – Low rate of KLm+m-:Predicts no mixing with Z0 boson & existence of Charm Quark Consistent with observed rate ~10-5 If possible should represent ~ 60% of the decays  Not Observed FCNC not allowed Extra u like quark needed to get proper rate Charm 10

  11. Original Puzzles from Kaon decays • 1944-47: Strangeness  quark model  Basis for QCD • 1956: Parity violation  Chiral nature of weak interactions • 1964: Suppression of FCNC  Properties of the weak neutral currents  Suggested charm quark • 1964: CP violation 11

  12. Puzzle #4 – CP violating Decays (CP):K0 reveals a more intricate picture • Flavor Eigenstate K0 - K0 oscillations d s - W- K0 K0 u, c, t u, c, t _ _ W+ d s s d u, c, t - _ W+ W- _ _ K0 K0 _ _ u, c, t d s 12

  13. K0 - K0 Oscillation quantified from leptonic decay Get positron: Kaon Interferometry G+ >> G- G+ ≈ Dm Orelectron: 13

  14. Puzzle #4 – CP violating Decays (CP):K0 reveals a more intricate picture • Flavor Eigenstate K0 - K0 oscillations • CP Eigenstate d s - W- K0 K1oo K1+- K2+-o K2ooo K0 u, c, t u, c, t _ CP=+1 _ W+ d s s d u, c, t - _ W+ W- _ _ K0 CP=-1 K0 _ _ u, c, t d s • Mass Eigenstate  Before observation of CP violation  = 0.9 x 10-10 s  = 5.2 x 10-8 s 14

  15. g, p0 Puzzle #4 – CP …Continues KL pp observed!  Violation of CP 1st:Indirect – 1964 1-2 per mil effect 2nd:Direct NA48/KTEV Re(e’/e) 15

  16. MIXING or INDIRECT DIRECT CP violation in the decay amplitute CP eigenstates ≠ mass eigenstates INTERFERENCE CP violation from interference of “DIRECT and MIXING” DIRECT CP firmly established after more than 30 years Re(e’/e) = (16.7±2.3)x10-4 Re(e’/e)(10-3) Puzzle #4 -- CP: clasification e Re(e’/e) 16

  17. Original Puzzles from Kaon decays • 1944-47: Strangeness  quark model  Basis for QCD • 1956: Parity violation  Chiral nature of weak interactions • 1964: Suppression of FCNC  Suggested charm quark  Properties of the neutral currents • 1964: CP violation  Subtle connection to 3-generation structure of matter 17

  18. CP If V*tdVts is complex CP is violated.. In shorthand: in Kaons required a 3rd generation of quarks to maintain Unitarity 3X3 a complex phase possible Without giving up Unitarity 18

  19. Summary of “s” puzzles and their contribution to the SM • 1944-47: Strangeness  quark model  Basis for QCD • 1956: Parity violation  Chiral nature of weak interactions • 1964: Suppression of FCNC  Suggested charm quark  Properties of the neutral currents • 1964: CP violation  Subtle connection to 3-generation structure of matter  Absolute matter-antimatter asymmetry… 19

  20. Why Puzzle #4 was so interesting? Potential Solution to the Baryon Asymmetry in the Early Universe +  2g 10,000,000,001 10,000,000,000  They basically have all annihilated away except a tiny difference between them 20

  21. Baryon Asymmetry in the Current Universe Baryon Asymmetry in the Current Universe us 1 …This is us TODAY!!! … After 30 years of studying CP-violation in the quark sector: Now we know that the effect is too small to be source of the Baryon Asymmetry 21

  22. Summary of “s” puzzles and their contribution to the SM • 1944-47: Strangeness  quark model  Basis for QCD • 1956: Parity violation  Chiral nature of weak interactions • 1964: Suppression of FCNC  Suggested charm quark  Properties of the neutral currents • 1964: CP violation  Absolute matter-antimatter asymmetry…  Subtle connection to 3-generation structure of matter > 30 Years Later > 30 Years Later 22

  23. So…What is currently going on in Kaon physics?  Let’s use NA48@CERN as an example 23

  24. Basics of Kaon Experiments like NA48 • 450 GeV protons from the CERN SPS hit a Be-target to produce the particles from which we make our beam line. • Neutral particles – not much can be done without destroying them. • Charged particles – can be momentum selected, transported and accelerated, if needed. • p • p (n) X1,X2,X3,X4,… @ NA48 we study the decay of both neutrals and charged Kaons 24

  25. Is there anything interesting in our NA48 neutral kaon beam lines? Bent Crystal 25

  26. Apyan,Velasco Beam instrumentation development based on aligned crystals Our NA59-Northwestern group used coherent phenomena & birefringence in aligned crystals to make: polarimeters l/4 plates for 100 GeV g Polarized positron sources 26

  27. Relevant Beam lines in 2002 & 2003-4 KS beam line K±beam line 27

  28. Decay region:Join HE Physics & you might find your self doing “archeological” work Our decay tank is not a passive device Northwestern: measure unexpected magnetic fields inside this vacuum tank Remember the Gargamelle experiment?  The ghost is still in our experimental hall 28

  29. and stay fit…while fixing the reconstruction of the charged tracks Gargamelle magnet was around this location! 29

  30. NA48 Detector Muon system: s(t)  350 ps M(00) ~ 2.5 MeV M(+-) ~ 2.5 MeV Spectrometer: pT kick ~250 MeV/c (P)/P  0.48%  0.009 P[GeV/c]% LKr Calorimeter: (E)/E  3.2%/√E  9%/E  0.42% s(t)  265 ps for 50 GeV e- 30

  31. Liquid Krypton Calorimeter (LKr) > 13,000 cells of 2X2 cm2 filled with ~10 m3 of liquid Krypton Northwestern responsibility - readout - calibration - corresponding trigger Electron / pion separation: E(LKr)/Momentum track (spectrometer) 31

  32. So… What are the new puzzles & what are we doing to understand them? • Anomalous B decay rates • Enhance weak penguins? Physics beyond the SM  Teresa’s thesis (NA48 data 2002, KS) • Violation of unitarity? • More than 3 generations  Physics beyond the SM  Anne’s Thesis (NA48 data 2003, K±) • Anomalous p+ p0e+ne rate • Tensor interactions  Physics beyond the SM  NA48 took special data sample this summer… (new students welcome !) 32

  33. g, n, (l+) n, (l+) Note on penguin diagrams Example, KL pp Not a good mode to look for New Physics… gluon hard to calculate! n, (l-) Z, (g) Example, KLp n n p m+m- p e+e- n, (l-) Z, (g) ??? • Z0 penguin diagrams well • understood, therefore a better mode to look for deviations from the SM. ? 33

  34. 1st puzzle: New Physics(NP) in KLp0ll ? Not only Kpnn ! NP sensitivity of KLp0ll system : Buras,Fleisher,Recksiegel, Schwab : hep-ph/0402112 Based on our Teresa’s results 34

  35. CPC Indirect CPV Direct CPV S→  0llmust be measured before looking for NP inL→  0ll J=2: Br(KLp0ee) < 3x10-12 J=0: Br(KLp0mm) ~ 5.2x10-12 ? Br(KLp0ee) = 5x10-12 Br(KLp0mm) = 1x10-12 35

  36. 7 signal events 6 signal events MK(GeV) Mgg(GeV) Mgg(GeV) Mmmp(GeV) Teresa’s thesis: First observation ofKSp 0 l +l - [PLB576 (2003)] CERN-PH-EP/2004-025 KSp0e+e- KSp0m+m- BR(KS p 0 e+e-) = BR(KS p 0 m +m -) = 36

  37. Implications for KL   l l BR(KL 0 ee)CPV × 1012 = Destructive Constructive BR(KL0 ll)CPV × 1012 BR(KL0 ll)CPV × 1012 BR(KLp0 e+ e-)SM x 1011= (3.1 or 1.3) ±1.0 BR(KLp0 m+ m-)SM x 1011= (1.8 or 1.2) ±0.3 37

  38. CPC Indirect CPV Direct CPV So can we look for NP inL→  0ll? OK! OK! ? Now we check for NP in the EW Penguins 38

  39. Recent rearches for KLp 0l+l- ?  Answer 1st puzzle Accessible from data currently being taken in Japan KTeV results BR(KL → p0 ee ) < 2.8 × 10-10 @ 90%CL Interf (-) 1 event (1 expected background) BR(KL→ p0 mm) < 3.8 × 10-10 @90%CL Interf (+) 2 event (0.87 expected background) 39

  40. 2nd Puzzle: CKM matrix – Unitary Problem? • Unitarity of CKM matrix requires: |Vud|2 +|Vus|2+ |Vub|2 = 1 • PDG 2004 data: |Vud| = 0.9738 ± 0.0005 - Neutron b-decay |Vub| = (3.67 ± 0.47).10-3 - ( |Vub|2 ≈ 10-5negligible) • SM prediction |Vus| = 0.2274 ± 0.0021 • Experimental value (begining 2003) |Vus| = 0.2200 ± 0.0026  |Vus|= 0.0074 ± 0.0033 ~2.2  discrepancy • 1 % Measurement needed • (limited by theory) 40

  41. Anne’s Thesis: Precise measurement of Vus 16 π3/2 Γ(Ke3)1/2 |Vus| |f+(0)| = ———————— GF MK5/2 SEW1/2 I1/2 Ke3 Br measurement: • Normalize Ke3 events to π ±π0 events • Br(π ±π0) = 0.2113±0.0014 • Selected Events: • Ke3+ ..... 59k Ke3- ..... 33k • π ±π0 .... 468k π ±π0....260k

  42. ICHEP 2004, Beijing -- John Ellis Conference Summary New Determinations of Vus Anne’s Thesis Vus x f+(0) 2nd Analysis Also from NU Michal Szleper • PDG02 42 CKM unitarity ‘crisis’ has disappeared

  43. So what was wrong? Radiative Corrections Ginsberg (Phys. Rev. 162, 1570 (1967) Phys. Rev. 187, 2280 (1969)) Data/MC Data/MC Without radiative corrections With corrections 43

  44. Physics misconceptions cleared… EXAMPLE BASED ON NEUTRAL KAONS – T. Andre Ke3 Km3 Ke3g Km3g 44

  45. Fine! Kaon Physics is still producing interesting results… What is next? 45

  46. Original list  new era to open up with the LHC program • Where did the anti-matter go? … What caused the matter-antimatter asymmetry of the Universe? • Can we explain the matter and energy composition of the Universe? • Why are there so many particles? … What causes their masses to be so different? • Where does mass come from? • Do all known forces unify as some large E scale? • Are there extra dimensions of space? 46

  47. We are already getting ready for theLarge Hadron Collider (LHC) • PP collisions at • s = 14 TeV • 4 experiments • 25 ns bunch spacing •  2835 bunches • 1011 p/bunch • Design Luminosity: • 1033cm-2s-1 (1034cm-2s-1) • 10 (100) fb-1/year 23 inelastic events per bunch crossing In LEP/LHC tunnel (circonf. 26.7 km) Planned Startup in April 2007 47

  48. However the LHC program will probably will not be enough… Rocky Kolb: "physicists have long known that "empty" space is not empty; it is filled by a field that gives quarks and leptons their mass. In the Standard Model, this field is called the Higgs... Dark energy may have relationships to both supersymmetry and the Higgs sector, implying a new emphasis on the quantum consistency of Higgs physics, including Higgs self-interactions." Cosmologies  abundance Particle Physics  properties 48 We will probably need a Multi-TeV e+e- ASAP 2015

  49. CLIC Dual beam scheme – Only viable multi-TeV Technology • With superconducting cavities: • Requires 33 km for 0.5 TeV • Cannot go beyond 0.8 TeV CLIC150 MV/m 3TeV vs 0.5TeV CLIC vs TESLA 49

  50. Aiming at having a design by 2008-10 50

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