Search for axion-like particles using a variable baseline photon regeneration technique

We report the first results of the GammeV experiment, a search for milli-eV mass particles with axion-like couplings to two photons. The search is performed using a "light shining through a wall" technique where incident photons oscillate into new weakly interacting particles that are able to pass through the wall and subsequently regenerate back into detectable photons. The oscillation baseline of the apparatus is variable, thus allowing probes of different values of particle mass. We find no excess of events above background and are able to constrain the two-photon couplings of possible new scalar (pseudoscalar) particles to be less than 3.1x10^{-7} GeV^{-1} (3.5x10^{-7} GeV^{-1}) in the limit of massless particles.Comment: 5 pages, 4 figures. This is the version accepted by PRL and includes updated limit

Examining CP Symmetry in Strange Baryon Decays

Non-conservation of CP symmetry can manisfest itself in non-leptonic hyperon decays as a difference in the decay parameter between the strange-baryon decay and its charge conjugate. By comparing the decay distribution in the $\Lambda$ helicity frame for the decay sequence $\Xi^{-} \to \Lambda \pi^{-}$, $\Lambda \to p \pi^{-}$ with that of $\bar{\Xi}^{+}$ decay, E756 at Fermilab did not observe any CP-odd effect at the $10^{-2}$ level. The status of a follow-up experiment, HyperCP (FNAL E871), to search for CP violation in charged $\Xi-\Lambda$ decay with a sensitivity of $10^{-4}$ is also presented.Comment: 9 pages, 4 figures, invited talk presented at the Third International Conference on B Physics and CP Violation, 3-7 Dec 1999, Taipei, Taiwa

Proposed New Antiproton Experiments at Fermilab

Fermilab operates the world's most intense source of antiprotons. Recently various experiments have been proposed that can use those antiprotons either parasitically during Tevatron Collider running or after the Tevatron Collider finishes in about 2010. We discuss the physics goals and prospects of the proposed experiments.Comment: 6 pages, 2 figures, to appear in Proceedings of IXth International Conference on Low Energy Antiproton Physics (LEAP'08), Vienna, Austria, September 16 to 19, 200

Measurement of the Alpha Asymmetry Parameter for the Omega- to Lambda K- Decay

We have measured the alpha parameter of the Omega- to Lambda K- decay using data collected with the HyperCP spectrometer during the 1997 fixed-target run at Fermilab. Analyzing a sample of 0.96 million Omega- to Lambda K^-, Lambda to p pi- decays, we obtain alpha_Omega*alpha_Lambda = [1.33+/-0.33(stat)+/-0.52(syst)] x 10^{-2}. With the accepted value of alpha_Lambda, alpha_Omega is found to be [2.07+/-0.51(stat)+/-0.81(syst)] x 10^{-2}.Comment: 5 pages, 4 figures, to be appeared as a Rapid Communication in Phys. Rev.

Evidence for the Decay Sigma+ -> p mu+ mu-

We report the first evidence for the decay Sigma+ -> p mu+ mu- from data taken by the HyperCP experiment(E871) at Fermilab. Based on three observed events, the branching ratio is B(Sigma+ -> p,mu+,mu-) = [8.6 +6.6,-5.4(stat) +/-5.5(syst)] x 10**-8. The narrow range of dimuon masses may indicate that the decay proceeds via a neutral intermediate state, Sigma+ -> p P0, P0 -> mu+ mu-, with a P0 mass of 214.3 +/- 0.5 MeV/c**2 and branching ratio B(Sigma+ -> p P0; P0 -> mu+ mu-) = [3.1 +2.4,-1.(stat) +/-1.5(syst)] x 10**-8.Comment: As published in PR

Search for the Lepton-Number-Violating Decay Ξ−→pμ−μ−\Xi^- \to p \mu^- \mu^-

A sensitive search for the lepton-number-violating decay $\Xi^-\to p \mu^-\mu^-$ has been performed using a sample of $\sim10^9$ $\Xi^-$ hyperons produced in 800 GeV/$c$ $p$-Cu collisions. We obtain $\mathcal{B}(\Xi^-\to p \mu^-\mu^-)< 4.0\times 10^{-8}$ at 90% confidence, improving on the best previous limit by four orders of magnitude.Comment: 9 pages, 5 figures, to be published in Phys. Rev. Let