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Published byRandolph Rodgers Modified over 2 years ago
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Salvatore Fiore University of Rome La Sapienza & INFN Roma1 for the KLOE collaboration LNF Spring School “Bruno Touscheck”, Frascati, 15-19 May 2006 CP/CPT tests at KLOE
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2 Neutral kaons at a -factory e + e b S = m = 1019.4 MeV BR( K 0 K 0 ) ~ 34% ~10 6 neutral kaon pairs per pb -1 produced in an antisymmetric quantum state with J PC = 1 K L K S 10 6 /pb -1 ; p* = 110 MeV/c S = 6 mm K S decays near interaction point L = 3.4 m Large detector to keep reasonable acceptance for K L decays (~0.3 L ) K + K - 1.5 10 6 /pb -1 p* = 127 MeV/c ± = 95 cm
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3 Neutral kaons at a -factory: tagging p K = 110 MeV/c S = 6 mm L = 3.5 m The detection of a kaon at large (small) times tags a K S (K L ) K L,S K S,L t1t1 t2t2 t=t 1 - t 2 f2f2 f1f1 not possible at fixed target possibility to select a pure K S beam (unique at a - factory, not possible at fixed target experiments) The decay at rest provides monochromatic and pure beam of kaons Tagging: observation of K S,L signals presence of K L,S - precision measurement of absolute BR’s
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4 DA NE: the Frascati -factory W = m (1019.4 MeV) L design 5 10 32 cm -2 s -1 Data taking finished last March L peak = 1.3 × 10 32 cm s L tot 2.5 fb -1 2001 170 pb -1 2002 280 pb -1 2004 734 pb -1 2005 1256 pb -1
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5 Be beam pipe (spherical, 10 cm , 0.5 mm thick) + instrumented permanent magnet quadrupoles (32 PMT’s) Drift chamber (4 m 3.75 m, CF frame) Gas mixture: 90% He + 10% C 4 H 10 12582 stereo sense wires almost squared cells Electromagnetic calorimeter lead/scintillating fibers (1 mm ), 15 X 0 4880 PMT’s 98% solid angle coverage Superconducting coil (B = 0.52 T) The KLOE design was driven by the measurement of direct CP through the double ratio: R = (K L + ) (K S 0 0 ) / (K S + ) (K L 0 0 ) KLOE experiment
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6 KLOE detector specifications E /E 5.7% / E(GeV) t 54 ps / E(GeV) 50 ps vtx ( ) ~ 1.5 cm ( from K L ) p /p 0.4 % (tracks with > 45°) x hit 150 m (xy), 2 mm (z) x vertex ~1 mm (M ) ~1 MeV
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7 K S tagged by K L interaction in EmC Efficiency ~ 30% (largely geometrical) K S angular resolution: ~ 1° (0.3 in ) K S momentum resolution: ~ 2 MeV K L “crash” = 0.22 (TOF) K S e K S e K L tagged by K S vertex at IP Efficiency ~ 70% (mainly geometrical) K L angular resolution: ~ 1° K L momentum resolution: ~ 2 MeV KS KS KS KS KL 2KL 2KL 2KL 2 K S and K L tagging
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8 BR K L CP Violation CP violating decay Related to K using K L beam tagged by K S → 328 pb -1 ’01+’02 data Selection K L vertex reconstructed in DC PID using decays kinematics Fit with MC spectra including radiative processes Normalization using K L events in the same data set
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9 Preliminary result BR(K L )= (1.963 0.012 0.017) 10 -3 in agreement with KTeV [PRD70 (2004),092006] BR=(1.975 0.012) confirm the discrepancy (4 standard deviations) with PDG04 BR=(2.090 0.025) PDG2004 KTeV KLOE preliminary BR(K L ) 10 -3 Using BR(K S ) and L from KLOE and S from PDG04 | = (2.216 0.013) 10 -3 | | PDG04 = (2.280 0.013) 10 -3 BR K L CP Violation (II) 1.5 with respect to prediction from Unitarity Triangle
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10 K S K L observables Measurements of K S K L observables can be used for these tests: K S 00 K S K S kl3 S L B(K L l3) Re Re y i( Im Im x ) S L B(K L l3) (A S +A L )/4 i( Im Im x ) S L K L S L K L CPT test: the Bell-Steinberger relation Exact relation: phase convention independent, no approx, in the CPT limit Looking at Im( ) 0 as CPTV signal
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11 K S K S K S K L K L l K S K L K S SW = (0.759±0.001) CPT test: inputs to the Bell-Steinberger relation S 0.08958 ± 0.00006 ns L = 50.84 ± 0.23ns A L A S K L K L =0.757 ± 0.012 = 0.763 ± 0.014 Im x + = (0.8 ± 0.7) 10 -2 Im x from a combined fit of KLOE + CPLEAR data
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12 We get the following results (error contours) on each term of the sum K S 00 K S K S S L B(K L l3) A S +A L )/4 i Im x S L K L S L K L 10 -4 Im Re CPT test: accuracy on i
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13 Re Im CPLEAR: Re Im CPT test: B-S KLOE result KLOE preliminary: Re Im
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