A. Alavi-Harati, T. Alexopoulos, M. Arenton, K. Arisaka, S. Averitte, R.F. Barbosa, A.R. Barker, M. Barrio, L. Bellantoni, A. Bellavance, J. Belz, R. Ben-David, D.R. Bergman, E. Blucher, G.J. Bock, C. Bown, S. Bright, E. Cheu, S. Childress, R. Coleman, M.D. Corcoran, G. Corti, B. Cox, M.B. Crisler, A.R. Erwin, R. Ford, A. Glazov, A. Golossanov, G. Graham, J. Graham, K. Hagan, E. Halkiadakis, J. Hamm, K. Hanagaki, S. Hidaka, Y.B. Hsiung, V. Jejer, D.A. Jensen, R. Kessler, H.G.E. Kobrak, J. LaDue, A. Lath, A. Ledovskoy, P.L. McBride, P. Mikelsons, E. Monnier, T. Nakaya, K.S. Nelson, H. Nguyen, V. O’Dell, M. Pang, R. Pordes, V. Prasad, X.R. Qi, B. Quinn, E.J. Ramberg, R.E. Ray, A. Roodman, M. Sadamoto, S. Schnetzer, K. Senyo, P. Shanahan, P.S. Shawhan, J. Shields, W. Slater, N. Solomey, S.V. Somalwar, R.L. Stone, E.C. Swallow, S.A. Taegar, R.J. Tesarek, G.B. Thomson, P.A. Toale, A. Tripathi, R. Tschirhart, S.E. Turner, Y.W. Wah, J. Wang, H.B. White, J. Whitmore, B. Winstein, R. Winston, T. Yamanaka, E.D. Zimmerman

We present a series of measurements based on K -> pi+pi- and K -> pi0pi0 decays collected in 1996-1997 by the KTeV experiment (E832) at Fermilab. We compare these four K -> pipi decay rates to measure the direct CP violation parameter Re(e'/e) = (20.7 +- 2.8) x 10^-4. We also test CPT symmetry by measuring the relative phase between the CP violating and CP conserving decay amplitudes for K->pi+pi- (phi+-) and for K -> pi0pi0 (phi00). We find the difference between the relative phases to be Delta-phi = phi00 - phi+- = (+0.39 +- 0.50) degrees and the deviation of phi+- from the superweak phase to be phi+- - phi_SW =(+0.61 +- 1.19) degrees; both results are consistent with CPT symmetry. In addition, we present new measurements of the KL-KS mass difference and KS lifetime: Delta-m = (5261 +- 15) x 10^6 hbar/s and tauS = (89.65 +- 0.07) x 10^-12 s.

We present a measurement of the charge asymmetry delta(L) in the mode K(L)-->pi(+/-)e(-/+)nu based on 298 x 10(6) analyzed decays. We measure a value of delta(L) = [3322+/-58(stat)+/-47(syst)]x10(-6), in good agreement with previous measurements and 2.4 times more precise than the current best published result. The result is used to place more stringent limits on CPT and DeltaS = DeltaQ violation in the neutral kaon system.

The recent discovery of a large CP violating asymmetry in KL-->pi+pi-e+e- mode has prompted us to seach for the associated KL-->pi 0 pi 0 e+e- decay mode in the KTeV-E799 experiment at Fermilab. In 2.7 x 10(11) K(L) decays, one candidate event has been observed with an expected background of 0.3 event, resulting in an upper limit for the KL-->pi 0 pi 0 e+e- branching ratio of 6.6 x 10(-9) at the 90% C.L.

We use K(L)'s in the 100-200 GeV energy range to produce 147 candidate events of the axial vector pair K1(1270)-K1(1400) in the nuclear Coulomb field of a Pb target and determine the radiative widths Gamma(K1(1400)-->K0+gamma)=280.8+/-23.2(stat)+/-40.4(syst) keV and Gamma(K1(1270)-->K0+gamma)=73.2+/-6.1(stat)+/-28.3(syst) keV. These first measurements appear to be lower than the quark-model predictions. We also place upper limits on the radiative widths for K(*)(1410) and K(*)(2)(1430) and find that the latter is vanishingly small in accord with SU(3) invariance in the naive quark model.

We have studied the rare weak radiative hyperon decay Cascade0-->Sigma0/gamma in the KTeV experiment at Fermilab. We have identified 4045 signal events over a background of 804 events. The dominant Cascade0-->Lambda/pi0 decay, which was used for normalization, is the only important background source. An analysis of the acceptance of both modes yields a branching ratio of BR(Cascade0-->Sigma0/gamma)=(3.34 +/- 0.05 +/- 0.09) x 10^(-3). By analyzing the final state decay distributions, we have also determined that the Sigma0 emission asymmetry parameter for this decay is alpha = -0.63 +/- 0.09.

We have studied the rare weak radiative hyperon decay Xi degrees -->Sigma degrees gamma in the KTeV experiment at Fermilab. We have identified 4045 signal events over a background of 804 events. The dominant Xi degrees -->Lambdapi degrees decay, which was used for normalization, is the only important background source. An analysis of the acceptance of both modes yields a branching ratio of B(Xi degrees -->Sigma degrees gamma)/B(Xi degrees -->Lambdapi degrees ) = (3.34+/-0.05+/-0.09)x10(-3). By analyzing the final state decay distributions, we have also determined that the Sigma degrees emission asymmetry parameter for this decay is alpha(XiSigma) = -0.63+/-0.09.

A. Alavi-Harati,12 T. Alexopoulos,12,* M. Arenton,11 K. Arisaka,2 S. Averitte,10 A. R. Barker,5 L. Bellantoni,7 A. Bellavance,9 J. Belz,10,† R. Ben-David,7 D. R. Bergman,10 E. Blucher,4 G. J. Bock,7 C. Bown,4 S. Bright,4 E. Cheu,1 S. Childress,7 R. Coleman,7 M. D. Corcoran,9 G. Corti,11 B. Cox,11 M. B. Crisler,7 A. R. Erwin,12 R. Ford,7 A. Glazov,4 A. Golossanov,11, G. Graham,4,‡ ,§ J. Graham,4 K. Hagan,11 E. Halkiadakis,10 J. Hamm,1 K. Hanagaki,8,k S. Hidaka,8 Y. B. Hsiung,7 V. Jejer,11 D. A. Jensen,7 R. Kessler,4 H. G. E. Kobrak,3 J. LaDue,5 A. Lath,10 A. Ledovskoy,11 P. L. McBride,7 P. Mikelsons,5 E. Monnier,4,¶ T. Nakaya,7,** K. S. Nelson,11 H. Nguyen,7 V. O’Dell,7 M. Pang,7 R. Pordes,7 V. Prasad,4 B. Quinn,4 E. J. Ramberg,7 R. E. Ray,7 A. Roodman,4,†† M. Sadamoto,8 S. Schnetzer,10 K. Senyo,8,‡‡ P. Shanahan,7 P. S. Shawhan,4,§§ J. Shields,11 W. Slater,2 N. Solomey,4 S. V. Somalwar,10 R. L. Stone,10 I. Suzuki,8,‡ E. C. Swallow,4,6 S. A. Taegar,1 R. J. Tesarek,10,‡ G. B. Thomson,10 P. A. Toale,5 A. Tripathi,2 R. Tschirhart,7 S. E. Turner,2 T. Uchizawa,1 Y. W. Wah,4 J. Wang,1 H. B. White,7 J. Whitmore,7 B. Winstein,4 R. Winston,4 T. Yamanaka,8 and E. D. Zimmerman4,kk

We report on the analysis of the rare decay K(L)-->mu(+)mu(-)gamma the 1997 data from the KTeV experiment at Fermilab. A total of 9327 candidate events are observed with 2.4% background, representing a factor of 40 increase in statistics over the current world sample. We find that B(K(L)-->mu(+)mu(-)gamma) = (3.62 +/- 0.04(stat) +/- 0.08(syst)) x 10(-7). The form factor parameter alpha(K*) is measured to be alpha(K*) = -0.160(+0.026)(-0.028). In addition, we make the first measurement of the parameter alpha from the D'Ambrosio-Isidori-Portolés form factor, finding alpha = -1.54 +/- 0.10. In that model, this alpha measurement limits the Cabibbo-Kobayashi-Maskawa parameter rho>-0.2.

We have collected a 43 event sample of the decay K(L)-->e(+)e(-)mu(+)mu(-) with negligible backgrounds and measured its branching ratio to be (2.62+/-0.40+/-0.17)x10(-9). We see no evidence for CP violation in this decay. In addition, we set the 90% confidence upper limit on the combined branching ratios for the lepton flavor violating decays K(L)-->e(+/-)e(+/-)mu(-/+)mu(-/+) at B(K(L)-->e(+/-)e(+/-)mu(-/+)mu(-/+))< or =1.23x10(-10), assuming a uniform phase space distribution.

A. Alavi-Harati,12 T. Alexopoulos,12 M. Arenton,11 K. Arisaka,2 S. Averitte,10 A. R. Barker,5 L. Bellantoni,7 A. Bellavance,9 J. Belz,10,* R. Ben-David,7 D. R. Bergman,10 E. Blucher,4 G. J. Bock,7 C. Bown,4 S. Bright,4 E. Cheu,1 S. Childress,7 R. Coleman,7 M. D. Corcoran,9 G. Corti,11 B. Cox,11 M. B. Crisler,7 A. R. Erwin,12 R. Ford,7 A. Glazov,4 A. Golossanov,11 G. Graham,4 J. Graham,4 K. Hagan,11 E. Halkiadakis,10 J. Hamm,1 K. Hanagaki,8 S. Hidaka,8 Y. B. Hsiung,7 V. Jejer,11 D. A. Jensen,7 R. Kessler,4 H. G. E. Kobrak,3 J. LaDue,5 A. Lath,10 A. Ledovskoy,11 P. L. McBride,7 P. Mikelsons,5 E. Monnier,4 T. Nakaya,7 K. S. Nelson,11 H. Nguyen,7 V. O’Dell,7 M. Pang,7 R. Pordes,7 V. Prasad,4 B. Quinn,4 E. J. Ramberg,7 R. E. Ray,7 A. Roodman,4 M. Sadamoto,8 S. Schnetzer,10 K. Senyo,8 P. Shanahan,7 P. S. Shawhan,4 J. Shields,11 W. Slater,2 N. Solomey,4 S. V. Somalwar,10 R. L. Stone,10 I. Suzuki,8 E. C. Swallow,4,6 S. A. Taegar,1 R. J. Tesarek,10 G. B. Thomson,10 P. A. Toale,5 A. Tripathi,2 R. Tschirhart,7 S. E. Turner,2 Y. W. Wah,4 J. Wang,1 H. B. White,7 J. Whitmore,7 B. Winstein,4 R. Winston,4 T. Yamanaka,8 and E. D. Zimmerman4

A. Alavi-Harati,12 T. Alexopoulos,12 M. Arenton,11 K. Arisaka,2 S. Averitte,10 R. F. Barbosa,7,* A. R. Barker,5 M. Barrio,4 L. Bellantoni,7 A. Bellavance,9 J. Belz,10 R. Ben-David,7 D. R. Bergman,10 E. Blucher,4 G. J. Bock,7 C. Bown,4 S. Bright,4 E. Cheu,1 S. Childress,7 R. Coleman,7 M. D. Corcoran,9 G. Corti,11 B. Cox,11 M. B. Crisler,7 A. R. Erwin,12 R. Ford,7 A. Glazov,4 A. Golossanov,11 G. Graham,4 J. Graham,4 K. Hagan,11 E. Halkiadakis,10 J. Hamm,1 K. Hanagaki,8 S. Hidaka,8 Y. B. Hsiung,7 V. Jejer,11 D. A. Jensen,7 R. Kessler,4 H. G. E. Kobrak,3 J. LaDue,5 A. Lath,10, A. Ledovskoy,11 P. L. McBride,7 P. Mikelsons,5 E. Monnier,4, T. Nakaya,7 K. S. Nelson,11 H. Nguyen,7 V. O’Dell,7 M. Pang,7 R. Pordes,7 V. Prasad,4 B. Quinn,4 X. R. Qi,7 E. J. Ramberg,7 R. E. Ray,7 A. Roodman,4 M. Sadamoto,8 S. Schnetzer,10 K. Senyo,8 P. Shanahan,7 P. S. Shawhan,4 J. Shields,11 W. Slater,2 N. Solomey,4 S. V. Somalwar,10 R. L. Stone,10 E. C. Swallow,4,6 S. A. Taegar,1 R. J. Tesarek,10 G. B. Thomson,10 P. A. Toale,5 A. Tripathi,2 R. Tschirhart,7 S. E. Turner,2 Y. W. Wah,4 J. Wang,1 H. B. White,7 J. Whitmore,7 B. Winstein,4 R. Winston,4 T. Yamanaka,8 and E. D. Zimmerman4 (KTev Collaboration) 1University of Arizona, Tucson, Arizona 85721 2University of California at Los Angeles, Los Angeles, California 90095 3University of California at San Diego, La Jolla, California 92093 4The Enrico Fermi Institute, The University of Chicago, Chicago, Illinois 60637 5University of Colorado, Boulder, Colorado 80309 6Elmhurst College, Elmhurst, Illinois 60126 7Fermi National Accelerator Laboratory, Batavia, Illinois 60510 8Osaka University, Toyonaka, Osaka 560-0043, Japan 9Rice University, Houston, Texas 77005 10Rutgers University, Piscataway, New Jersey 08854 11The Department of Physics and Institute of Nuclear and Particle Physics, University of Virginia, Charlottesville, Virginia 22901 12University of Wisconsin, Madison, Wisconsin 53706 (Received 14 March 2001; published 22 August 2001) We have collected a 43 event sample of the decay KL ! eemm with negligible backgrounds and measured its branching ratio to be 2.62 6 0.40 6 0.17 3 1029. We see no evidence for CP violation in this decay. In addition, we set the 90% confidence upper limit on the combined branching ratios for the lepton flavor violating decays KL ! eemm at B KL ! eemm # 1.23 3 10210, assuming a uniform phase space distribution.