Kaon physics at KLOE. M.Palutan. Frascati for the KLOE collaboration Moriond-EW 2006

Transcript

1 Kaon physics at KLOE M.Palutan Palutan,, INFN/Frascati Frascati for the KLOE collaboration Moriond-EW

2 The DAΦNE e + e collider Collisions at c.m. energy around the φ mass: s ~ MeV Angle between the beams at crossing: α crs 12.5 mrad Residual laboratory momentum of φ: p φ ~ 13 MeV/c Cross section for φ peak: σ φ ~ 3.1 µb Grand total (2001/5): L = 2.5 fb -1 L peak = cm -2 s -1 Results presented in this talk from 2001/2 data: L = 450 pb -1 2 KLOE plots: end 2005

3 K physics at KLOE - tagging The φ decay at rest provides monochromatic and pure beam of kaons pure J PC = 1 state K S, K + φ K L, K BR 1 2 ( K, p K, p K, p K, p ) L S L S φ decay mode K + K 49.1% K S K L 34.1% Tagging: observation of K S,L signals presence of K L,S ; K + signals K K S beam unique!! absolute branching ratio measurement: BR = (N sig /N tag )(1/ε sig ) Kaon momentum is measured with 1 MeV resolution (e.g. p(k L ) = p(φ)- p(k S )) 3 K + K /pb -1 p* = 127 MeV/c λ ± = 95 cm K L K S 10 6 /pb -1 p* = 110 MeV/c λ S = 6 mm; λ L = 3.4 m

4 The KLOE detector Large cylindrical drift chamber 4m, 3.75m length, carbon-fiber He/IsoC4H10 90/10 σp/p = 0.4 % (tracks with θ > 45 ) σxhit = 150 µm (xy), 2 mm (z) σxvertex ~1 mm Lead/scintillating-fiber calorimeter σe/e = 5.7% / E(GeV) σt = 54 ps / E(GeV) 50 ps σl(γγ) ~ 2 cm (π0 from KL π+π π0) Superconducting coil: 0.52 T field 4

5 Outline CPT test in semileptonic K S -K L decays Measurement of K S πeν charge asymmetry A S CP/CPT test from unitarity UL on BR(K S π 0 π 0 π 0 ) A S BR(K L π + π ) preliminary V us and CKM unitarity BR(K S πeν) and form factor slope BR(K L πlν) and τ L K L e3 form factor slopes BR(K ± π 0 l ± ν) and τ ± BR(K + µ + ν) preliminary 5

6 K S πeν: CPT test Sensitivity to CPT violating effects through charge asymmetry _ Γ(K S,L π - e + ν) Γ(K S,L π + e - ν) A S,L = _ Γ(K S,L π - e + ν) + Γ(K S,L π + e - ν) A S = 2(Re ε + Re δ Re y + Re x ) A L = 2(Re ε Re δ Re y Re x ) CP CPT in mixing CPT in decay ΔS ΔQ and CPT A S A L 0 implies CPT δ = 1 2 M 11 M 22 i(γ 11 Γ 22 )/2 m S m L i(γ S Γ L )/2 6 A L = (3.322 ± ± 0.047) 10-3, KTeV 2002

7 K S πeν: BR and A S TOF e/π ID, fit to E miss p miss spectrum Normalize to π + π counts Branching ratio BR(πeν) = (7.046±0.077±0.049 ) 10 4 signal fractional error: 1.3% = 1.1% stat 0.7% syst Charge asymmetry A S = ( 1.5 ± 9.6 ± 2.9 ) 10 3 bkg first measurement δa S ~ with 2.5 fb -1 K Se3 form factor slope λ + = ( 33.9 ± 4.1 ) 10 3 first meas., compatible with K L 7 hep-ex/ , accepted by PLB

8 K S πeν: CPT test 1) Re x : CPT viol. and ΔS ΔQ A S A L = 4 ( Re x + Re δ ) A L KTeV σ= Re δ CPLEAR σ= Re Re x = (( 0.8 ± 2.5) Factor 5 improvement w.r.t. current most precise measurement (CPLEAR, σ= ) 2) Re y: CPT viol. and ΔS=ΔQ A S +A L = 4 (Re ε Re y) Comparable Re Re y = (( ± 2.5) Re ε from PDG not assuming CPT with best result (CPLEAR from unitarity, σ= ) 8

9 CPT test: the Bell-Steinberger relation Measurements of K S K L observables can be used for the CPT test from unitarity : 1 (1 + i tan φ SW ) [Re ε i Im δ] = A*(K S f ) A(K L f ) Σ Γ f S = Σ f α f α kl3 = 2τ S /τ L B(K L l3) [Re ε Re y i( Im δ + Im x + )] = 2τ S /τ L B(K L l3) [(A S +A L )/4 i( Im δ + Im x + )] α + = η + Β(K S π + π ) α 00 = η 00 Β(K S π 0 π 0 ) α + γ = η + Β(K S π + π γ) α + 0 = τ S /τ L η + 0 Β(K L π + π π 0 ) α 000 = τ S /τ L η 000 Β(K L π 0 π 0 π 0 ) 9 (more details from M.Testa)

10 CPT test: result Im δ Im δ Re ε KLOE preliminary: Re ε = (160.2 ± 1.3) 10 5 Im δ =(1.2 ± 1.9) 10 5 CPLEAR: Re ε = (164.9 ± 2.5) 10 5 Im δ =(2.4 ± 5.0) Uncertainty on Imδ is now dominated by φ + and φ 00 - Semileptonic sector contributes by ~ 10%

11 Unitarity test of CKM matrix: V us, V us /V ud Unitarity test from 1 st row: V ud 2 + V us 2 + V ub 2 ~ V ud 2 + V us 2 1 Δ Can test if Δ = 0 at 10-3 level: from super-allowed nuclear β-decays: 2 V ud δv ud = from semileptonic kaon decays: 2 V us δv us = Extract V us from K l3 decays Γ(K πlν(γ)) V us f + (0) 2 I(λ t ) S EW (1 + δ ΕΜ + δ SU(2) ) theory uncertainty: 0.8% on f + (0) Extract V us / V ud from Γ(K ± µν(γ))/γ(π ± µν(γ)) Γ(π µν(γ)) V ud 2 f π αc π Γ(K µν(γ) V us 2 f K αc K theory uncertainty: 1.3% on f K /f π 11 KLOE can measure all experimental inputs: BR, τ, λ

12 BR(K L πlν) and τ L K L πeν, πµν: K L vertex reconstructed in DC Fit to p miss E miss spectrum (7% of the sample) Absolute BR: (N sig /N tag ) 1/ε sig the error on geometric acceptance is dominated by τ L Using the constraint BR(K L ) = 1: min(p miss E miss ) in πµ or µπ hyp. BR(K L πeν) = ± stat ± syst BR(K L πµν) = ± stat ± syst τ L = (50.72 ± 0.17 stat ± 0.33 syst ) ns precision 12 PLB 632 (2006)

13 τ L from K L π 0 π 0 π 0 Excellent lever arm for lifetime measurement (P K = 110 MeV) K L momentum known from tag Uniform reconstruction efficiency with respect to L K 10 2 Events/0.3 ns ns cm 0.37 λ L τ L = ± 0.17 stat ± 0.25 syst ns PLB 626 (2005) σ rel ~ L/βγc (ns) 13 Average with result from K L BR s: τ L = ± 0.23 ns σ rel ~ Vosburg, 72 τ L = ± 0.44 ns

14 K Le3 form factor slopes Momentum transfer t= (p K p π ) 2 is measured Fit to t-spectrum with different hypothesis on t- dependence of the form factor hep-ex/ accepted by PLB Linear: 1 + λ + t λ + = (28.6 ± 0.5 ± 0.4) 10 3 Quadratic: 1 + λ + t/m π+ + 1/2 λ + (t/m π+ ) 2 λ + = (25.5 ± 1.5 ± 1.0) 10 3 λ + = ( 1.4 ± 0.7 ± 0.4) 10 3 ρ(λ +, λ + ) = 0.95 Pole model: M V2 /(M V2 t), Taylor exp. λ + =(m π /M V ) 2, λ + =2 λ 2 + m V = (870 ± 7) MeV Quadratic (*) ISTRA+ m π± /m π0 correction 14 Phase space integral I(λ) depends on the parameterization: I Pole - I Quad KLOE KTeV Pole model

15 K ± lifetime Tag events with K ± µ ± ν decay Identify a kaon decay vertex on the opposite side 1 st method: obtain τ ± from the K decay length Measure the kaon decay length taking into account the energy loss: τ K = i ΔL i /(β i γ i c) Tag(Kµ2) τ ± = ± stat ± syst ns preliminary 2 nd method: obtain τ ± from the K decay time Use only K ± π ± π 0 decays Measure the kaon decay time: τ K = (t γ R γ /c)/γ K, using the π 0 clusters 15

16 BR(K ± π 0 l ± v) K + π 0 l + ν decays are tagged by K µ ν and K π π 0 (and viceversa) K ± π 0 e ± ν and K ± π 0 µ ± ν are separated by fitting the lepton mass spectrum, obtained from TOF: t decay K = t lept -L lept /β(m lept )c = t γ -L γ /c Ev/(14MeV) 2 K ± e3 K ± µ3 K nucl.int. Kππ 0 π 0 Kππ 0 Preliminary results: BR(K ± e3 ) = (5.047 ± stat ± syst-stat ± syst ) 10-2 BR(K ± µ3 ) = (3.310 ± stat ± syst-stat ± syst ) 10-2 σ syst under evaluation 16

17 V us f + (0) from KLOE results BR τ K Le3 K Lµ (15) (15) 50.84(23) ns K Se (91)_ (6) ps K ± e3 K ± µ (46) (40) (24) ns Slopes λ + = (30) λ + = (3) (Pole model: KLOE, KTeV, and NA48 ) λ 0 = (95) (KTeV, Istra+) Unitarity band: V us f + (0) = (22) f + (0)=0.961(8) Leutwyler and Roos 1984 V ud = (27) Marciano and Sirlin CKM unitarity test Δ = 0.001±0.001 χ 2 /dof = 1.9/4

18 BR(K + µ + ν(γ)) Tag from K µ ν Subtraction of π + π 0, π 0 l + ν background Count events in (225,400) MeV window of the momentum distribution in K rest frame BR(K + µ + ν(γ)) = ± stat. ± syst. 18 PLB 632 (2006)

19 The V us V ud plane Using f K /f π =1.198(3)( ) MILC Coll we get V us /V ud = ± V us = ± K l3 KLOE, using f + (0)=0.961(8) V ud = ± Marciano and Sirlin Phys.Rev.Lett ,2006 unitarity Fit of the above results: V us = ± V ud = ± P(χ 2 ) = 0.66 Fit assuming unitarity: V us = ± P(χ 2 ) =

20 Conclusions 1) KLOE impact on kaon decays made a considerable step during 2005: a) we published: UL on BR(K S π 0 π 0 π 0 ), τ L, BR(K L ), BR(K Se3 ) and A S, BR(K + µ2), K Le3 ff b) we have final results on: BR(K L π + π ), Γ(K S π + π )/Γ(K S π 0 π 0 ) c) we have preliminary results on: BR(K ± π 0 l ± ν), τ(k ± ) 2) Results on K Se3 allow to improve the present limits on CPT violation in semileptonic kaon decays 3) We improved the present limit on CPT violation through the Bell-Steinberger relation by a factor of 2.5 4) CKM matrix unitarity is tested through determination of V us from semileptonic kaon decays (5 different channels) V us /V ud from K + leptonic decay 5) KLOE data taking will stop on March 16th: L TOT ~ 2.7 fb 1 20

21 21 Spares slides

22 Tagged K L and K S beams K L crash β= = 0.22 (TOF) K S π + π K L 2π 0 K S π e + ν 22 K L tagged by K S π + π vertex at IP Efficiency ~ 70% (mainly geometrical) K L angular resolution: ~ 1 K L momentum resolution: ~ 1 MeV ~ tagged K L K S tagged by K L interaction in EmC Efficiency ~ 30% (largely geometrical) K S angular resolution: ~ 1 K S momentum resolution: ~ 1 MeV ~ tagged K S

23 K S πeν: CPT test K S πeν amplitudes π + e υ H W K 0 = a + b π e + υ H W K 0 = a * b * π e + υ H W K 0 = c + d π + e υ H W K 0 = c * d * b=d=0 if CPT holds c=d=0 if ΔS=ΔQ holds Sensitivity to CPT violating effects through charge asymmetry A S = 2(Re ε + Re δ Re y + Re x ) A L = 2(Re ε Re δ Re y Re x ) CP CPT in mixing CPT in decay ΔS ΔQ and CPT 23 δ = 1 2 M 11 M 22 i(γ 11 Γ 22 )/2 m S m L i(γ S Γ L )/2 Re y = Re b/a Re x = Re d * /a

24 ΔS ΔQ ΔS = ΔQ CPT holds = Re(c /a) = Re(x + ) = K S πeν: test of ΔS=ΔQ 1 2 Γ(K S πeν) Γ(K L πeν) Γ(K S πeν) + Γ(K L πeν) SM expectation: x ~ , no ΔS ΔQ transitions at first order Re(x + ) + ) = ((-0.5 ± 3.6) Factor 2 improvement w.r.t. current most precise measurement (CPLEAR, σ= ) BR(K Le3 ) BR(K S πeν) KLOE τ(k S ) PDG τ(k L ) KLOE BR(K L πeν) KLOE 0.40 KTeV 04 KLOE 05 from KLOE BR(K S πeν) assuming ΔS = ΔQ 0.39 PDG 04 24

25 Γ(K S π + π (γ))/γ(k S π 0 π 0 ) Statistical abundance allows to perform 17 independent measurements with few per mill accuracy R ππ vs. running period ± stat ± syst-stat ± syst accuracy 3 improvement respect to KLOE 2002 (2.236 ± stat ± statsyst ± syst ) χ 2 /dof = 0.86 [P(χ 2 )=0.62] KLOE average: ± hep-ex/

26 CPT test: inputs Im x + = (0.8 ± 0.7) 10-2 from a combined fit of KLOE-KTeV (A S A L ) and CPLEAR (A δ ) data: accur. 3 Β(K S π + π )/Β(K S π 0 π 0 )=2.2549± Β(K S π + π γ)< Β(K S π + π π 0 )=(3.2±1.2) 10 7 Β(K S π 0 π 0 π 0 )< Β(K L πlν)=0.6705± Β(K L π + π π 0 )=0.1263± Β(K L π + π )=(1.963 ± ) 10 3 Β(K L π + π γ)=(29±1) 10 6 Β(K L π 0 π 0 )=(8.65 ±0.10) 10 4 τ S = ± ns τ L = ± 0.23ns A L =(3.32±0.06) 10 3 A S =(1.5±10.0) 10 3 φ SW = (0.759±0.001) φ + =0.757 ± φ 00 = ± φ 000 = φ + 0 = φ + γ =[0,2π] 26 (KLOE measurements)

27 K S π 0 π 0 π 0 : direct search Observation of K S 3π 0 signals CP violation in mixing and/or in decay: SM prediction: Γ S = Γ L ε +ε 000 2, => BR(K S 3π 0 ) ~ Previous results: BR(K S 3π 0 ) < (direct search, SND, 99) BR(K S 3π 0 ) < (interference, NA48, 04) γ counting kinematic fit in the 2π 0 and 3π 0 hypothesis ζ 2 2π ζ 2 3π PLB 619 (2005) BR( K S 3π 3π 00 )) < % CL η 000 < at 90% CL 27

28 BR(K L π + π ) PID using decay kinematics Normalize to K L πµν events preliminary BR = (1.963±0.012±0.017) 10-3 σ rel : 1.1% = 0.6% stat 0.9% syst in agreement with KTeV 2004 BR = (1.975 ± 0.012) 10 3 it confirms the 4 σ discrepancy with PDG04 = (2.080 ± 0.025) 10-3 we get: η + = (2.216 ± 0.013) 10-3 [ BR(K S ππ) and τ L from KLOE, τ S from PDG04] PDG04: ε = (2.280 ±0.013) E ( ππ ) + 2 miss p miss (MeV)

29 CPT test: accuracy on α i We get the following accuracies on each term of the sum: 10-4 α + = η + Β(K S π + π ) Im 2τ S /τ L B(K L l3) [ (A S +A L )/4 i Im x + ] α 00 = η 00 Β(K S π 0 π 0 ) Re α + 0 = τ S /τ L η + 0 Β(K L π + π π 0 ) α + γ = η + Β(K S π + π γ) α 000 = τ S /τ L η 000 Β(K L π 0 π 0 π 0 ) 29

30 CPT test: m(k)-m(k) GeV GeV CPLEAR KLOE Γ(K)-Γ(K) Γ(K)-Γ(K) m(k)-m(k) m(k)-m(k) GeV GeV δ = 1 2 M 11 M 22 i(γ 11 Γ 22 )/2 m S m L i(γ S Γ L )/2 σ(δm) ~ GeV σ(δγ) ~ GeV 30

31 Dominant K L BR s and τ L K L πeν, πµν, π + π - π 0 : K L vertex reconstructed in DC Fit to p miss E miss spectrum K L π 0 π 0 π 0 : Photon vertex reconstructed by TOF (7% of the sample) Absolute BR: (N sig /N tag ) 1/ε sig ε geo dominated by error on τ L Using the constraint BR(K L ) = 1: min(p miss E miss ) in πµ or µπ hyp. 31 BR(K L πeν) = ± stat ± syst BR(K L πµν) = ± stat ± syst BR(K L 3π 0 ) = ± stat ± syst BR(K L π + π π 0 ) = ± stat ± syst τ L = (50.72 ± 0.17 stat ± 0.33 syst ) ns precision

32 K Le3 form factor slopes: fit Divide data into 20 bins ( 3 < t < +7) N i = N 0 Σ 20 j =1 A ij ε j ρ j (λ +, λ + ) F j FSR A ij ε j ρ j F FSR j Smearing matrix (MC) Reconstruction efficiency Bare K e3 decay density FSR correction λ + Obtained from MC generator, affect mainly at low t Data divided into 14 periods Good stability of results Good agreement for e + π, π e + bare ρ(t) MC K e3 γ λ + = 0.03 λ + = 0 t 32

33 Linear fit: λ K Le3 form factor slopes: result χ 2 /dof e + π 28.7 ± /181 π + e 28.5 ± /181 All 28.6 ± /363 λ + = (28.6 ± 0.5 ± 0.4) 10 3 Quadratic fit: λ λ χ 2 /dof e + π 24.6 ± ± /180 π + e 26.4 ± ± /180 All 25.5 ± ± /362 λ + = (25.5 ± 1.5 ± 1.0) 10 3 λ + = ( 1.4 ± 0.7 ± 0.4) 10 3 Correlation: ρ(λ +, λ + ) = 0.95 Pole model: m V = 870(7) MeV Pole model versus Quadratic parameterization: 0.5 per mil difference in phase space integral, I e. 33 (*) ISTRA+ m π± /m π0 correction

34 K S πµν: first observation Measurement never done before More difficult than K Se3 : 1) Lower BR: expect ) Background events from K S ππ, π µν: same PIDs of the signal Event counting from the fit to E miss (πµ) P miss distribution: 3% stat error Efficiency estimate from K Lµ3 early decays and from MC + data control samples Data K S µ π + ν + ππγ + ππ E miss (πµ) P miss (MeV) 34