AION/Magis

Abstract:

String theories with topologically complex compactification manifolds suggest the simultaneous presence of many unbroken U(1)'s without any light matter charged under them. The gauge bosons associated with these U(1)'s do not have direct observational consequences. However, in the presence of low energy supersymmetry the gauge fermions associated with these U(1)'s, the "photini", mix with the Bino and extend the MSSM neutralino sector. This leads to novel signatures at the LHC. The lightest ordinary supersymmetric particle (LOSP) can decay to any one of these photini. In turn, photini may transition into each other, leading to high lepton and jet multiplicities. Both the LOSP decays and inter-photini transitions can lead to displaced vertices. When the interphotini decays happen outside the detector, the cascades can result in different photini escaping the detector leading to multiple reconstructed masses for the invisible particle. If the LOSP is charged, it stops in the detector and decays out-of-time to photini, with the possibility that the produced final photini vary from event to event. Observation of a plenitude of photini at the LHC would be evidence that we live in a string vacuum with a topologically rich compactification manifold.

Abstract:

We report on a search for the process pp̄→γ+W/Z with W/Z→qq̄ in events containing two jets and a photon at the center-of-mass energy s=1.96TeV, using 184pb-1 of data collected by the CDF II detector. A neural network event selection has been developed to optimize the rejection of the large QCD production background; it is shown that this method gives a significant improvement in both signal-to-noise ratio and signal sensitivity, as compared with an event selection based on conventional cuts. An upper limit is presented for the γ+W/Z production cross section with the W and Z decaying hadronically. © 2009 The American Physical Society.

Abstract:

Using e+e-→Ds-Ds*+ and Ds*-Ds+ interactions at 4170 MeV collected with the CLEO-c detector, we investigate the semileptonic decays Ds+→f0(980)e+ν and Ds+→e+ν. By examining the decay rates as functions of the four-momentum transfer squared q2, we measure the ratio [dBdq2(Ds+→f0(980)e+ν)B(f0→π+π-)]/[dBdq2(Ds+→e+ν) B(→K+K-)] at q2 of zero to be (42±11)%. This ratio has been predicted to equal the rate ratio [B(Bs→J/ψf0)B(f0→π+π-)]/ [B(Bs→J/ψ)B(→K+K-)], thus indicating that the CP eigenstate J/ψf0 could be useful for measuring CP violation via Bs mixing. Assuming a simple pole model for the form factor |f+(q2)| in the f0e+ν decay, we find a pole mass of (1.7-0.7+4.5±0.2)GeV. We also determine the f0 mass and width as (977-9+11±1) and (91-22+30±3)MeV, respectively. In addition, we present updated results for B(Ds+→f0(980)e+ν) B(f0→π+π-)=(0.20±0.03±0.01)% and B(Ds+→e+ν)=(2. 36±0.23±0.13)%. Assuming that the f0 wave function is a combination of strange and nonstrange quark-antiquark components, we use our measurement for B(Ds+→f0(980)e+ν) to extract a value of the mixing angle that we find consistent with s̄s dominance, adding to the mystery as to why the f0 decays predominantly to two pions rather than two kaons. © 2009 The American Physical Society.

Abstract:

We measure the absolute branching fractions of Ds semileptonic decays where the hadron in the final state is one of φ, η, η′, KS0, K 0, and f0, using 2.8×105 e+e-→DsDs decays collected in the CLEO-c detector at a center-of-mass energy close to 4170 MeV. We obtain B(Ds+→e+νe)=(2.29±0.37±0.11)%, B(Ds+→ηe+νe)= (2.48±0.29±0.13)%, B(Ds+→η′e+νe)=(0.91±0. 33±0.05)%, where the first uncertainties are statistical and the second are systematic. We also obtain B(Ds+→K0e+νe)=(0.37±0.10±0. 02)%, and B(Ds+→K0e+νe)=(0.18±0.07±0.01)%, which are the first measurements of Cabibbo suppressed exclusive Ds semileptonic decays, and, B(Ds+→f0e+νe)×B(f0→π+π-)=(0.13±0.04±0.01) %. This is the first absolute product branching fraction determination for a semileptonic decay including a scalar meson in the final state. © 2009 The American Physical Society.