Rare Kaon Decays: Progress and Prospects. Douglas Bryman University of British Columbia

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1 Rare aon Decays: Progress and Prospects Douglas Bryman University of British Columbia

2 Overview of Rare aon Decays State of the art: single event sensitivity, 1-12 Exotic Searches µ e π + + f FV " Axions". < SM Parameters and BSM Physics ow Energy QCD Chiral Perturbation Theory + µ µ π νν + + V V + π e e CPviolation π ν ν CP violation + γ l l l = e, µ e e + π l l td td... Radiative decays 1-8 : 62 events 1-1 : 2 events 1-11 : 4 events

3 Standard Model CP Violation "Jarlskog invariant" JCP 2 2 Im * λ A = VV ts td λ 1! 2 Four super-clean processes will challenge the Standard Model: Κ d x x s d π + + Κ νν π νν Β ψ Κ S * VtsVtd 9 4 9, C M Im ( V * ts td ) O PIO sin(2 β ) BABAR, BEE, CDF,D V V ts td V E CDF, D, H C B, BTEV

4 πνν in the Standard Model + π + ν ν π ν ν Top Quark Dependence λ t = V ts V td Im(λ t )=Im(V ts V td) SM BR (1 11 ) 7.2 ± ± 1.2 Est. Theory Uncertainty 7% (charm) 2% Negligible long distance effects (1 13 ). Hadronic matrix elements from isospin analog + π e + ν e.

5 Standard Mode l ( Buras): Im λ=imv V = ηa 2 Im t x λ = X x 5 t R( 1 ) ( ) λ x1 Aη = 2.6 ± 1.2 x1 11 πνν πνν R( + + ) 1. 1 * 2 5 ts td 4 2 x 1 A η + ( ρ ρ ) 2 = 7.2 ± 2.1x1 11 t λ ittenberg

6 .5 B ψ S and πνν Differences sensitive to new physics virtually free of uncertainties. Γ( π νν) + Γ( π + νν) aπνν SM Candidates: * ow energy SUSY * Minimal Flavor Violation * Multiple Higgs * New Physics in B * New Physics in s d νν d B d a ψs CP asymmetry in B ψ S (Nir and Worrah, Phys. ett. B )

7 Comparison of Precision from Future and B Measurements σ ( V cb ) =±.2(.1) πνν B-Factory Era (Buras,1999) HCB/BTEV σ ( V td ) ± 1%(9%) ± 5.5%(3.5%) ± 5%(2.5%) σ ( ρ) ±.16(.12) ±.3 ±.1 ση ( ) ±.4(.3) ±.4 ±.1 σ (sin 2 β ) ±.5 ±.6 ±.2 (Im ) σ λ t ±5% ± 14%(11%) ± 1%(6%)

8 BN E787(E949) Measurement of + πνν +

9 Special Features of Measuring + πνν + Background processes may exceed signal by >1 1 Arbitrary Unit + π π π (.17) π π π (.56) + µ π ν (.32) e π ν (.48) + + µ ν (.63) π π (.21) Momemtum (MeV/c) Determine everything possible about the + and π + * π + /µ + particle ID better than 1 6 ( π + -µ + -e + ) Eliminate events with extra charged particles or photons * π inefficiency < 1-6 Suppress backgrounds well below the expected signal (S/N~1) * Predict backgrounds from data: dual independent cuts * Use Blind analysis techniques * Test predictions with outside-the-box measurements Evaluate candidate events with S/N function + π ν ν Search Region

10 Background Processes: Range vs. Momentum Signal Box

11 γ π + + π Background Suppression Dual cuts: γ Veto and inematics (P,R,E...) Veto Reversed γ Veto Applied Range vs. Energy Momentum Max. γ veto Check for correlations

12 E787 Background Estimates Source Events µν.4 ± π π ± + + Beam π.2 ±.2 Charge exch..3± Total.15 ± Efficiency 3 N = 5.9 x 1 ε = 2 x 1 +

13 E787 22: Two + πνν + Candidates R (cm) π + Range vs. Energy E (MeV) Event P (MeV/c) R (cm) E (MeV) S/N N + = 5.9 x 12 Efficiency 3 1 ε = 2 x 1 Estimated Background:.15±. 5 events

14 Branching Ratio B( ) = 1.57± x1 + πνν Consistent with SM: (.72±.21)x1-1 Estimated probability of being due to background only :.2% imits on * t ts td 4 4 t Re( t ) < (68%..) (9 (Independent of B system, 2.9 x1 < λ < 1.2 x 1 (68% C..) x < λ x C Im( λ ) < t λ V x V % C..) ε, ε ')

15 D Ambrosio and Isidori, 22 hep-ph/ Impact of E787 and E949 on Flavor Physics sin(2β) 1 η.8.6 M / M d s πνν E949 at the E787 BR 1 η ρ ρ Figure 2: Allowed region in the ρ η plane using only theoretically clean observables: 9% C.. interval imposed by sin(2β) (dashed); 9% C.. limit from the upper bound on M Bd / M Bs (full); 9% C.. limit from the lower bound on B( + π + ν ν) (dotted). For comparison the 68% and 9% C.. ellipses from the global fit in Fig. 1 are also shown. E787 and other clean observables (9% C) Figure 3: Allowed region in the ρ η plane with the inclusion of B( + π + ν ν) and without B d B d data. The two external contours denotes 68% and 9% confidence intervals; the inner (dotted) one is the 68% confidence interval under the assumption that experimental error in (1) is reduced by a factor two. Possible E949 result favoring Non-SM

16 + πνν + Future Prospects BN E949 (22- ) Upgrade of E787 detector Improved photon vetos truly hermetic coverage Access to the low momentum region Sensitivity goal: <1-11 Order of magnitude improvement beyond E787 Factor 5-1 below the SM prediction E949 at 6 2x rate + 5 µ + Momentum from µ + ν of 4 E Muon momentum (MeV/c)

17 + + πνν FNA CM (~27- ) New in-flight technique - RF-separated beam Particle ID : RICH Sensitivity goal: <1-12 Beam Time Stamp aon RICH.7 atm CF 4 aon Entrance Angle Tracker CM Apparatus Vacuum Veto Exit Time Plane Forward Veto Pion RICH 1 atm Neon u c t C M d s b Conversion Veto Plane BM19 Magnet Hole Veto Momentum simulation: RICH vs Tracking π π + + Upstream Magnetic Spectrometer 5 MHz Separated + Beam 22 GeV/c Beam Interaction Veto Downstream Magnetic Spectrometer Muon Veto Beam Dump M 2 missing

18 CM Goal: 1 events with S/N>7 Effective BR Background source ( 1 12 ) +! μ + νμ < :4 +! ß + ß 3:7 +! μ + νmufl < :9 + A! X;! ß + e νe < :14 + A! ß + X in trackers < 4: + A! ß + X in residual gas < 2:1 Accidentals (2 + decays :51 Total < 1:6

19 + + π νν Measurements vs. Year CM

20

21 imits on π X Familon / Axion mass Branching Ratio vs. mx 9 percent C.. Branching Ratio imit Previous E787 New s.e.s M X (MeV/c 2 )

22 Probing CP Violation with Rare aon Decays π πνν + e e Difficult to get at short distance physics due to long distance strong interaction effects and other complications. Progress is being made. The Golden Mode! but can it be measured? M edicti n 1 A = ± 1.2 x1 11 S πνν η 4 2 Pr o :R( ) 4.1x1 2.6

23 π + e e B e e x FNA E + 1 exp ( π ) < ( ) CP conserving part - two photon intermediate state. Can' t be calculated reliably now. Need π γγ CP violating parts - single photon intermediate states # Direct CP violation -- the goal! R( π e e ) CPV dir 6.7 x1 Aη = 4x1 + # Mixing - Need S π e e π e e CPV Mix ε S π e e τ S πνν : τ R( ) R( ) Background : Same diagrams as γγ e + e

24 π + e e CP conserving part: two-photon intermediate state. NA48 Preliminary results (22): B( πγγ) = (1.36 ±.3 ±.3 ±.3 ) x 1 TEV 6 stat syst norm 1999 :1.68 ±.1) x 1 V 6 (a =-.72 ±.5 ±.6 ) x TEV 6 CHPT : 1.5 1, shape par.: a V ~.7 NA48 π γγ B( ).6 1 γγ a =-.46 ±.3 ±.3 ±.2 V NA48 8 πγγ < x m [3,11] y [,2] B( ) CPC ( ) x 1 13 π ee + = ±

25 π + e e CP violating part due to mixing: + CHPT 2 R( 9 S π e e ) CPV Mix 5.2( as ) x1, as ~ B( S π ee) < 1.4 x1 NA48 (21): Use CHPT, a <5.2: B( π e e ) < 4.4 x Background s : + γγ ee CPV Mix B( π ee) ~3x1 Greenlee γγ ee [ ]

26 NA48/1 Rare Decay Studies (22- ) The and S beams Upgraded detectors and beamline. 1 x intensity Improved S target S.E.S~ 1-1

27 NA48/1 -Motivation S π l + l, l=e, µ Bound Indirect CP Violation in the πdecay l + l to < 1-12 Search for CPV in S decays S 3π, S π + π - π Study of time dependent CPV asymmetry in S, π+ π γ* Test of Chiral Perturbation Theory S γγ, S π γγ, S π π γγ Study S Dalitz and semi -leptonic decays Semi-leptonic and radiative neutral hyperon Ξ Σ + e - ν, Ξ Σ + µ - ν, Ξ Σ γ, Ξ Λγ R. Sacco (22)

28 Experiments seeking πνν imit based on isospin and πνν : < x [ Grossman, Nir ] TEV (FNA) result: R ( πνν) < 5.9x1 Γ( all) E E391a OPIO (BN) Γ( goal goal : s.e.s. πνν) 1 : s.e.s < 1, >5 events Primary Background: ππ R( ππ ) ~ 1 3

29 Photon Vetoing E Photonuclear E787 2 ε γ ~ 1 (2-1 MeV) 4 ~ 1 (1-22 MeV) επ < 1 6 Photon vetoing & inematics: Suppress events with low energy photons ππ Missing mass (2E1 miss E2 miss cosθ 12 ) vs. Missing energy (E1 miss + E2 miss ) ε π < (1 )(1 ) = 1 πνν

30 Charged Particle Vetoing + Example Background: π e νγ ε Plastic Scintillator PSI Measurement π π + (Preliminary) MC Data Momentum (MeV/c) E: 1 GeV/c Particle OPIO Goal + 4 e π e + 5 NIM A359, 478 (1995) (3.2 ±.9) x1 < 1.6x1 < 1.3x1 4 4 π (6. ±.6) x 1 ε

31 E PS Features: * Pencil Beam * Pilot Project for JHF * High acceptance * Test reliance on extreme * High P T selection photon veto efficiency

32 E Neutral Beam Measurements H. Watanabe (22) Neutrons

33 OPIO: Measurement of π ν ν CONCEPTS Measure as much as possible: Energy, position and ANGE of each photon. Work in the C.M. system : Use TOF to get the momentum. Maximize Photon Veto Efficiency Maximize Intensity of Microbunched Beam

34 Shashlyk calorimeter PM tube 5 m steel tapes Paper + lead + paper Scintillator Beam γ veto 2 X Preradiator Parameter Minimal Expected Requirement Performance E γ resolution 3.5%/ E 2.7%/ E θ γ resolution (25MeV) (25 3) mr 23 mr t γ resolution 1ps/ E 5ps/ E x γ,y γ resolution(25mev) 1mm < 1mm µ-bunch width 3ps 2ps γ-veto inefficiency ɛ E787.3ɛ E787

35 inematic suppression of backgrounds Goal: >5 Events with S/N>2 E vs. E E * * * π γ1 γ 2 πνν ππ

36 Summary and Outlook + + πνν: 2 events seen B( + πν + ν ) = 1.57 ±.82 x1 (E787) Prospects: E949 ( 1 events) and CM (1 events) π E391a JHF? νν Prospects < 9 (s.e.s. 1 ) and O (5 : OPI events). Exotics: New results on π x, πγ (E787) Soon, πµ e, others (TEV/E799, BN E865)

37 Summary and Outlook Radiative and semi-rare decays: New results on S + + πγγ, πee, S + πγγ(na48), π ee(e799), π µµ (HYPER-CP), π e ν(oe) + ± S Soon, others (TEV/E799, BN E865, NA48, OE) New Experiments: NA48/1: Rare decays of 's and hyperons, CPV in decays S OE : ε'/ ε, CPT, rare decays, test of CHPT