Search

The cross section for b{bar b} production in 800 GeV/c pN interactions has been measured in Fermilab experiment E771 to be 43{sup +27}{sub {minus}17}(stat){sup +7}{sub {minus}7}(syst) nb per nucleon from the observation of events in which both the b and the {bar b} decay semimuonically or a B decays into a J/{psi} followed by J/{psi}{r_arrow}{mu}{sup +}{mu}{sup {minus}} . {copyright} {ital 1998} {ital The American Physical Society}

We have searched for the flavor changing neutral current decay Do + p-l+p”in the dimuon data obtained by the E771 experiment conducted at Fermilab. No evidence is found. A branching ratio of (-1.0 ‘A:,’ f 0.2) x 10v6 is obtained, corresponding to a 90% confidence level upper limit of 3.3 x 10m6. This new upper limit is about three times more sensitive than the best published limit. (Submitted to Physical Review Letters)

The asymmetry in the {bar p} angular distribution in the sequential decay {bar {Omega}}{sup +} {yields} {bar {Lambda}}K{sup +} {yields} {bar p}{pi}{sup +}K{sup +} has been measured to be {bar {alpha}}{sub {Omega}}{bar {alpha}}{sub {Lambda}} = [+1.16{+-}0.18(stat){+-}0.17(syst)]x10{sup -2} using 1.89x10{sup 6} unpolarized {bar {Omega}}{sup +} decays recorded by the Hyper CP (E871) experiment at Fermilab. Using the known value of {alpha}{sub {Lambda}}, and assuming that {bar {alpha}}{sub {Lambda}} = -{alpha}{sub {Lambda}}, {bar {alpha}}{sub {Omega}} = [-1.81{+-}0.28(stat){+-}0.26(syst)]x10{sup -2}. A comparison between this measurement of {bar {alpha}}{sub {Omega}}{bar {alpha}}{sub {Lambda}} and recent measurements of {alpha}{sub {Omega}}{alpha}{sub {Lambda}} made by HyperCP shows no evidence of a violation of CP symmetry.

The asymmetry in the rho angular distribution in the sequential decay Omega+--LamdaKappa+--rhopi+Kappa+. has been measured to be alphaOmegaalphaLamda=[+1.16+/-0.18(stat)+/-0.17(syst)]x10(-2) using 1.89x10(6) unpolarized Omega+ decays recorded by the HyperCP (E871) experiment at Fermilab. Using the known value of alphaLamda, and assuming that alphaLamda=-alphaLamda, alphaOmega=[-1.81+/-0.28(stat)+/-0.26(syst)]x10(-2). A comparison between this measurement of alphaOmegaalphaLamda and recent measurements of alphaOmegaalphaLamda made by HyperCP shows no evidence of a violation of CP symmetry.

We report the first evidence for the decay ∑+ → pμ+ μ- from data taken by the HyperCP (E871) experiment at Fermilab. Based on three observed events, the branching ratio is B(∑+ → pμ+ μ-) = [8.6 -5.4 +6.6(stat) ± 5.5(syst)] × 10 -8. The narrow range of dimuon masses may indicate that the decay proceeds via a neutral intermediate state, ∑+ rarr; pp0, p0 → μ+ μ- with a P0 mass of 214.3 ± 0.5 MeV/c 2 and branching ratio B(∑+ rarr; pp 0, p0 → μ+ μ-) = [3.1-1.9 -2.4(stat) ± 1.5(syst)] × 10 -8. © 2005 The American Physical Society.

The novel sources of CP violation observed in charged χ and λ hyperon decays were investigated. A comparison of the p and p angular distributions in the hyperon decays was made using a subset of the data from the HyperCP experiment (E871) at Fermilab. A possible source of bias was found to be a momentum-dependent differential loss of events due to interactions of the χ- and χ+ decay products. The obtained result was observed to be stable with respect to time, χ momentum, and secondary-beam intensity, The results show that differences between the χ- and χ+ production angles could cause a bias due to production polarization differences.

A sensitive search for the lepton-number-violating decay Xi(-)--pmu(-)mu(-) has been performed using a sample of approximately 10(9) Xi(-) hyperons produced in 800 GeV/c p-Cu collisions. We obtain B(Xi(-)--pmu(-)mu(-))4.0x10(-8) at 90% confidence, improving on the best previous limit by 4 orders of magnitude.

A sensitive search for the rare decays Omega(-)--Lambdapi(-) and Xi(0)--ppi(-) has been performed using data from the 1997 run of the HyperCP (Fermilab E871) experiment. Limits on other such processes do not exclude the possibility of observable rates for |DeltaS| = 2 nonleptonic hyperon decays, provided the decays occur through parity-odd operators. We obtain the branching-fraction limits B(Omega(-)--Lambdapi(-))2.9 x 10(-6) and B(Xi(0)--ppi(-))8.2 x 10(-6), both at 90% confidence level.

We report the first evidence for the decay Sigma(+)--pmu(+)mu(-) from data taken by the HyperCP (E871) experiment at Fermilab. Based on three observed events, the branching ratio is B(Sigma(+)--pmu(+)mu(-))=[8.6(+6.6)(-5.4)(stat)+/-5.5(syst)]x10(-8). The narrow range of dimuon masses may indicate that the decay proceeds via a neutral intermediate state, Sigma(+)--pP(0),P0--mu(+)mu(-) with a P0 mass of 214.3+/-0.5 MeV/c(2) and branching ratio B(Sigma(+)--pP(0),P0--mu(+)mu(-))=[3.1(+2.4)(-1.9)(stat)+/-1.5(syst)]x10(-8).

We have compared the p and p angular distributions in 117 x 10(6) Xi- --Lambdapi- --ppi-pi- and 41 x 10(6) Xi+ --Lambda pi+ --p pi+pi+ decays using a subset of the data from the HyperCP experiment (E871) at Fermilab. We find no evidence of CP violation, with the direct-CP-violating parameter AXiLambda identical with (alphaXialphaLambda-alpha Xialpha Lambda)/(alphaXialphaLambda+alphaXialphaLambda)=[0.0+/-5.1(stat)+/-4.4(syst)] x 10(-4).

A study on the measurement of φ≡ using a sample of 144×106 ≡- →λπ- decays having an average polarization of 3.7% was presented. The polarized ≡-'s were produced by directing an 800 geV÷c proton beam onto a 2 mm ×2 mm× 60 mm cu target at angles of +3 and -3 mrad. The results were shown to be a 2.9× improvement over the best previous mesurements. It was shown that CP violation in charged ≡→λπ decays are not suppressed by a vanishing final phase shift difference.

Using data collected with the HyperCP (E871) spectrometer during the 1997 fixed-target run at Fermilab, we report the first observation of the decay K--->pi(-)mu(+)mu(-) and new measurements of the branching ratios for K+/--->pi(+/-)mu(+)mu(-). By combining the branching ratios for the decays K+-->pi(+)mu(+)mu(-) and K--->pi(-)mu(+)mu(-), we measure Gamma(K+/--->pi(+/-)mu(+)mu(-))/Gamma(K+/--->all) = (9.8+/-1.0+/-0.5)x10(-8). The CP asymmetry between the rates of the two decay modes is [Gamma(K+-->pi(+)mu(+)mu(-))-Gamma(K--->pi(-)mu(+)mu(-))]/[Gamma(K+-->pi(+)mu(+)mu(-))+Gamma(K--->pi(-)mu(+)mu(-))] = -0.02+/-0.11+/-0.04.

Using data collected with the HyperCP (E871) spectrometer during the 1997 fixed-target run at Fermilab, we report the first observation of the decay K---pi(-)mu(+)mu(-) and new measurements of the branching ratios for K+/---pi(+/-)mu(+)mu(-). By combining the branching ratios for the decays K+--pi(+)mu(+)mu(-) and K---pi(-)mu(+)mu(-), we measure Gamma(K+/---pi(+/-)mu(+)mu(-))/Gamma(K+/---all) = (9.8+/-1.0+/-0.5)x10(-8). The CP asymmetry between the rates of the two decay modes is [Gamma(K+--pi(+)mu(+)mu(-))-Gamma(K---pi(-)mu(+)mu(-))]/[Gamma(K+--pi(+)mu(+)mu(-))+Gamma(K---pi(-)mu(+)mu(-))] = -0.02+/-0.11+/-0.04.