1. 15 January 2005University of Chicago NSF Site Visit Chicago CP Group: KTeV and Braidwood Overview of group Status of KTeV analysis Braidwood Neutrino Experiment Ed Blucher

2. Current group members (KTeV + Braidwood): Faculty: Ed Blucher Senior research associate: Rick Kessler* (25% for 2005, 0% after) Postdoc: Matt Worcester, ongoing search Grad students: Erin Abouzaid, Elizabeth Worcester* Undergraduate students: Abby Kaboth, Jennifer Seger, David Underwood Recent departures: Sasha Glazov (postdoc); now at DESY Val Prasad (Blucher student): now at Yale Colin Bown (Blucher/Winstein student): now at UT Austin Jim Graham (Blucher student): now at Catalyst * only KTeV + Kelby Anderson, Jim Pilcher on Braidwood

3. Charged particle momentum resolution 8 GeV/c; momentum scale known to 0.01% from K    . CsI energy resolution < 1% for E  > 3 GeV; energy scale known to 0.1% from K  e. The KTeV Experiment E832:  /  to 10 -4 E799: rare K L decays to 10 -11 (data taking:1996-2000) Chicago NSF: CsI calorimeter, trigger, online and offline software

4. Chicago group physics analyses:  + neutral K parameters (  m,  S,  + ,  00  +  ) (Elizabeth Worcester dissertation) |V us |: K L branching fractions, semileptonic form factors, radiative semileptonic decays  0  e + e   branching fraction (Erin Abouzaid dissertation) Semileptonic charge asymmetry  mass K* mass K L  +    0 and K L  0  0  0 form factors

5. To distinguish between direct and indirect CP violation, compare K L,S    ,     :  /   0 direct CP violation K L ~ K odd +  K even  “Direct” in decay process “Indirect” from asymmetric mixing   : Indirect vs. Direct CP Violation: (Blucher,Glazov,Graham,Kessler,Prasad,Worcester)

6. KTeV Result: Re(  ) = (20.7  1.5(stat)  2.4(syst))  10 -4 = (20.7  2.8)  10 -4 World average: Re(  ) = (16.6   6)    (confidence level = 10%) A. Alavi-Harati et al (KTeV), Measurements of Direct CP Violation, CPT Symmetry, and Other Parameters in the Neutral Kaon System, Phys. Rev. D 67, 012005 (2003).

7. K L - K S Interference Downstream of Regenerator KTeV Results:

8. History of K S Lifetime and  m Measurements

9. Current  Analysis Improvement in systematics needed to take advantage of increase in statistics. Better treatment of nearby and overlapping clusters: E scale, E nonlinearity Better modeling of fringe field: calorimeter calibration, E nonlinearity Improved drift chamber alignment: calorimeter calibration, E nonlinearity Improved simulation of delta rays: p t distribution, neutral background estimate Better drift chamber performance (99) and track reconstruction: mass resolution improved by ~10%. Full treatment of photon angles in simulation and reconstruction: E scale, E nonlinearity All improvements implemented; detailed data-MC comparisons underway.

10. K  +   Analysis: Full data sample K  0  0 Analysis: “Seed block” energy distribution Data/MC Ratio Clusters / 0.5 GeV 2005 Analysis 2002 Analysis (published) Data MC

11. “Bench Tests” with prototype drift chamber (DC) and full KTeV electronics to study pathologies observed in DC resolution. DC wire

12. A New Determination of |V us | For first row, PDG quotes 2.2  deviation from unitarity: Interesting to revisit K L measurements (PDG fit values based on averages of many old experiments with large errors) Recent K + measurement from BNL E865 consistent with unitarity. Motivation: (Blucher, Glazov, Kessler)

13. Determination of |V us | in Semileptonic K L Decays KTeV measures B(K L  e ) and B(K L  ) KTeV measures form factors needed to calculate phase space integrals Rad. Corrections (theory) Form factor at t=0 (theory)

14. To determine the semileptonic widths, we measure the following 5 ratios: These six decay modes account for 99.93% of K L decays, so ratios may be combined to determine branching fractions. E.g.,

15. Features of Branching Fraction Analysis Each ratio measured in statistically independent data sample collected with a single trigger (samples sizes are 10 5 to 10 6 per decay mode) Each ratio measured in two data samples: “high intensity” (same data used for  analysis) “low intensity” (no regenerator and  10 lower intensity) Result for each ratio based on sample with lower total uncertainty Monte Carlo simulation is used to correct for acceptance difference between pair of modes Simulation includes inner bremsstrahlung contributions for all decay modes with charged particles, so branching fractions include radiated photons. For K L , we do not use muon system. For K L      , we do not reconstruct the    decay.

16. Neutral Decay Modes 4 or 6 photon-like clusters are paired to reconstruct two or three neutral pions consistent with a single decay vertex. (Analysis almost identical to  analysis.)

17. Comparison of data and Monte Carlo kaon energy distributions Monte Carlo spectrum was tuned using K L  +   events For partially reconstructed modes, high energy solution is plotted

18. Data – MC Comparison for Radiative Photon Candidates K e3(  ) and K  3(  ) : KLOR written by T. Andre. Includes virtual and real photons. K  (  ) : PHOTOS K  (  ) : KTeV generator includes IB, but ignores direct emission. Radiation changes K e3 acceptance by 3%; effect on other modes is < 0.5%.

19. ModesPartial Width Ratio  K  3 /  Ke3 0.6640  0.0014  0.0022  000 /  Ke3 0.4782  0.0014  0.0053   0 /  Ke3 0.3078  0.0005  0.0017   /  Ke3 (4.856  0.017  0.023)  10  3  00 /  000 (4.446  0.016  0.019)  10  3 Measured Partial Width Ratios

20. Comparison of KTeV and PDG Branching Fractions

21. Determination of |  +  | Using B(K L  ) KTeV: K L -K S Interference

22. Semileptonic Form Factor Measurements (to determine I K integrals) I K depends on the two independent semileptonic FFs: We use the following parametrization for f + and f 0 :

23. Parameter Value (   ) + 20.64  1.75 +  3.20  0.69 0 13.72  1.31 Form Factor Results

24. Semileptonic Form Factors: 0  5 more precise than PDG

25. Summary of Vus Changes from KTeV Measurements  Ke3 increases by 5%  K  3 doesn’t change Compared to PDG: I e decreases by 1.7% I  decreases by 4.2% (both include -1% shift from +  )

26. |V us | Results |V us | = 0.2252  0.0008 KTeV  0.0021 ext KTeV error: branching fractions, form factors Ext error: f + (0), K L lifetime, radiative corrections For K L  e : |V us | = 0.2253  0.0023 For K L  : |V us | = 0.2250  0.0023 Averaging these results (accounting for correlations):

27. Comparison with Unitarity  theory A 5 sigma difference!

28. “V us ” Publications T. Alexopoulos et al (KTeV), A Determination of the CKM Parameter |V us |, Phys. Rev. Lett. 93, 181802 (2004). T. Alexopoulos et al (KTeV), Measurements of K L Branching Fractions and the CP Violation Parameter |  +  |, Phys. Rev. D 70, 092006 (2004). T. Alexopoulos et al (KTeV), Measurements of Semileptonic K L Decay Form Factors, Phys. Rev. D 70, 092006 (2004). T. Alexopoulos et al (KTeV), Measurements of the Branching Fractions and Decay Distributions for K L  and K L  e , Phys. Rev. D 71, 012001 (2005). + Chicago Sun Times, Science Blog, Newswise, ScienceDaily, etc. T. C. Andre, Radiative Corrections in Decays, hep-ph/0406006, submitted to Eur. Phys. J. C.

29. Neutrino Oscillations During last few years, oscillations among different flavors of neutrinos have been established; physics beyond the S.M. Mass eigenstates and flavor eigenstates are not the same (similar to quarks): mass eigenstates flavor eigenstates Raises many interesting questions including possibility of CP violation in neutrino oscillations. CP violation in neutrino sector could be responsible for the matter-antimatter asymmetry. MNSP matrix

30.  12 ~ 30°  23 ~ 45°sin 2 2  13 < 0.2 at 90% CL What is e component of 3 mass eigenstate? What do we know? normal inverted

31. What is value of  13 ? What is mass hierarchy? Do neutrino oscillations violate CP symmetry? Value of   3 central to these questions; it sets the scale for experiments needed to resolve mass hierarchy and search for CP violation. Key questions Why are quark and neutrino mixing matrices so different?

32. DNP, DPF, DAP, DPB Joint Neutrino Study on the Future of Neutrino Physics (2004) We recommend, as a high priority, a comprehensive U.S. program to complete our understanding of neutrino mixing, to determine the character of the neutrino mass spectrum, and to search for CP violation among neutrinos. This program should have the following components: An expeditiously deployed multi-detector reactor experiment with sensitivity to disappearance down to sin 2 2   = 0.01, an order of magnitude below present limits. A timely accelerator experiment with comparable sin 2 2   = 0.01 sensitivity and sensitivity to the mass hierarchy through matter effects. A proton driver in the megawatt class or above and neutrino superbeam with an appropriate very large detector capable of observing CP violation and measuring the neutrino mass-squared differences and mixing parameters with high precision. (G. Barenboim and E. Blucher, co-leaders of Reactor Working Group) Recommendation 2 (of 3):

33. Methods to measure sin 2 2  13 Accelerators: Appearance (   e ) Reactors: Disappearance ( e  e ) Use fairly pure, accelerator produced  beam with a detector a long distance from the source and look for the appearance of e events T2K: = 0.7 GeV, L = 295 km NO A: = 2.3 GeV, L = 810 km Use reactors as a source of e ( ~3.5 MeV) with a detector 1-2 kms away and look for non-1/r 2 behavior of the e rate Reactor experiments provide the only clean measurement of sin 2 2   : no matter effects, no CP violation, almost no correlation with other parameters. (In combination with accelerator experiments, can resolve  23 degeneracy.)

34. 90% CL exluded regions with no osc.signal 90% CL allowed regions with osc.signal Reactor and accelerator sensitivities to sin 2 2   sin 2 2θ 13 = 0.05, δ CP =0, Δm 2 = 2.5×10 -3 eV 2 (3 yr reactor, 5 yr T2K) δ CP =0, Δm 2 = 2.5×10 -3 eV 2 (3 yr reactor, 5 yr Nova)

35. ~200 m~1300 m How to improve on previous reactor experiments? (Chooz limit: sin 2 2   < 0.15 for  m 2 =2.5  10  3 eV 2 )  Add an identical near detector Eliminate dependence on reactor flux; only relative acceptance of detectors needed  Optimize baseline (1500 m)  Larger detectors (5 ton  50 tons)  Reduce backgrounds (Go deeper 100m  150 to 300m) Past reactor measurements:

36. The Braidwood Experiment Features of Braidwood site: 2  3.6 GW reactors – 7.17 GW maximum power Flat: flexibility, equal overburden at near and far sites, surface transportation of detectors Favorable geology (dolomitic limestone): good for excavation, low radioactivity (order of magnitude lower U, Th than granite)

37. Braidwood Collaboration  Argonne Nat. Lab.: M. Goodman, V. Guarino, L. Price, D. Reyna  Brookhaven Nat. Lab.: R. Hahn, M. Yeh, A Garnov, Z. Chang, C. Musikas  U. of Chicago: E. Abouzaid, K. Anderson, E. Blucher,* M. Hurowitz, A. Kaboth, D. McKeen, E. Pod, J. Pilcher, J. Seger, M. Worcester  Columbia: J. Conrad, Z. Djurcic, J. Link, K. McConnel, M. Shaevitz,* G. Zeller  Fermilab: L. Bartoszek, D. Finley, H. Jostlein, C. Laughton, R. Stefanski  Kansas State: T. Bolton, C. Borjas, J. Foster, G. Horton-Smith, N. Kinzie, J. Kondikas, D. Onoprienko, N. Stanton, D. Thompson  U. of Michigan: B. Roe  MIT: P. Fisher, R. Cowan, L. Osborne, G. Sciolla, S. Sekula, F. Taylor, T. Walker, R. Yamamoto  Oxford: G. Barr, S. Biller, N. Jelley, G. Orebi-Gann, S. Peeters, N. Tagg  U. of Pittsburgh: D. Dhar, N. Madison, D. Naples, V. Paolone, C. Pankow  St. Mary’s University: P. Nienaber  Sussex: L. Harris  U. of Texas: A. Anthony, M. Huang, J. Jerz, J. Klein, A. Rahman, S. Seibert  U. of Washington: J. Formaggio spokesperson

38. Goals: Flexibility, redundancy, cross checks 4 identical 65 ton fiducial mass detectors; 2 at near site, 2 at far site “Two zone detectors”: inner zone with Gd-loaded LS and r=2.6 m; outer zone with mineral oil and r=3.5 m. Movable detectors with surface transport for cross- calibration; vertical shaft access to detector halls Oscillation measurements using both rate and energy spectrum Full detector construction above ground Near and far detectors at same depth of 450 mwe with flat overburden; deep near detector will allow measurement of sin 2  W. Braidwood Baseline Design

39. Detectors and analysis strategy designed to minimize relative acceptance differences 6 meters Shielding Central zone with Gd-loaded scintillator surrounded by buffer regions; fiducial mass determined by volume of Gd-loaded scintillator Events selected based on coincidence of e + signal (E vis >0.5 MeV) and  s released from n+Gd capture (E vis >6 MeV). No position reconstruction; little sensitivity to E requirements. To reduce backgrounds: depth + active and passive shielding Neutrino detection by

40. Braidwood Experiment Projected Uncertainties and Sensitivity 3 year run

41. Baseline Cost and Schedule Estimates Civil Construction (Hilton and Assoc. consulting firm, using U of C seed money) Detectors (Bartozek engineering, ANL) Schedule 2004 Engineering/R&D proposal submitted 2005 Full proposal submission 2007 Project approval; construction start 2009 Start datataking Four detectors with veto system + EDIA $18M Contingency$5M Construction + EDIA $34M Contingency$8.5M $42.5M $23M

42. Braidwood Engineering / R&D Proposal Exelon Letter of support: - Enthusiastic about project - No security and site access problems foreseen - 1 st step was MOU on bore holes Multi-institution proposal submitted to NSF and DOE (PI: Blucher, CO-PIs: Shaevitz, Bolton, Klein, Fisher) Proposal requests funding to complete the design and engineering of the baseline project: Civil engineering design leading to RFP for a “Design and Build” Detector engineering leading to full “Design Report” Final development of stable Gd loaded scintillator Budget: Civil Engineering$525k Detector Engineering$408k Liquid Scint.$28k Education and Outreach$78k Total$1039k

43. Using seed money ($100k) from University of Chicago, we’ve drilled bore holes to full depth (200m) at the near and far shaft positions. Detailed information on geology, ground water, radioactivity, density, etc. Bore hole study provides information needed for underground construction design; reduces required contingency Demonstrates willingness of Exelon to allow construction on their site. First construction at Braidwood site (December 2004)

44. Chicago Braidwood Group Activities Software development and detector optimization studies - Matt Worcester co-leads the Braidwood Software and Background Group (with Tim Bolton) Front-end electronics, DAQ, trigger development - Jim Pilcher leads the Braidwood Electronics Group Liquid scintillator test cell Detector mechanical engineering (Pod): Calibration system and phototube support Braidwood site investigation

45. Small liquid scintillator test cell Instrumented with CAMAC ADCs,TDCs, NIM electronics + ATLAS Tile Calorimeter electronics system We’ve performed initial studies with cosmics and radioactive sources: Co, AmBe, Cf. Gd Loaded Scintillator Phototube

46. 60” 20” Large test cell with 100 liter Gd-loaded central region under construction ACRYLIC CYLINDER END PLATES MATCH DETECTOR VESSEL THICKNESS

47. Student training: KTeV and Braidwood experiments have provided exceptional opportunities for training graduate and undergraduate students. Examples: Val Prasad: 2002 Fermilab Dissertation of the Year award. Now doing atomic physics at Yale. Peter Shawhan: 1999 Fermilab Dissertation of the Year award. Working on LIGO at Caltech. Abby Kaboth (current undergrad): Working on liquid scintillator studies for Braidwood. Goldwater scholarship winner. David Underwood (current undergrad): Performing measurement of semileptonic charge asymmetry, K L attenuation for  analysis Jennifer Seger (current undergrad): Reactor experiment sensitivity studies; KTeV CsI energy calibration

48. CP Group Summary Group is completing KTeV analysis program and starting new program in neutrino oscillation physics. We play a leading role in both experiments. We have concentrated group’s efforts on small number of important physics topics that have an extremely broad impact in particle physics. Both KTeV and Braidwood experiments provide exceptional training opportunities for undergraduates, grad students, postdocs, and faculty.