Overview of the RFX Fusion Science Program

With a program well-balanced among the goal of exploring the fusion potential of the reversed field pinch (RFP) and that of contributing to the solution of key science and technology prob- lems in the roadmap to ITER, the European RFX-mod device has produced a set of high-quality results since the last 2010 Fusion Energy Conference. RFX-mod is a 2 MA RFP, which can also be operated as a tokamak and where advanced confinement states have 3D features studied with stellarator tools. Self-organized equilibria with a single helical axis and improved confinement (SHAx) have been deeply investigated and a more profound understanding of their physics has been achieved. First wall conditioning with Lithium provides a tool to operate RFX at higher density than before, and application of helical magnetic boundary conditions favour stationary SHAx states. The correlation between the quality of helical states and the reduction of magnetic field errors acting as seed of magnetic chaos has been robustly proven. Helical states provide a unique test-bed for numerical codes conceived to deal with 3D effects in all magnetic configura- tions. In particular the stellarator equilibrium codes VMEC and V3FIT have been successfully adapted to reconstruct RFX-mod equilibria with diagnostic input. The border of knowledge has been significantly expanded also in the area of feedback control of MHD stability. Non-linear dynamics of tearing modes and their control has been modelled, allowing for optimization of feedback models. An integrated dynamic model of the RWM control system has been developed integrating the plasma response to multiple RWMs with active and passive conducting structures (CarMa model) and with a complete representation of the control system. RFX has been oper- ated as a tokamak with safety factor kept below 2, with complete active stabilization of the p2, 1q Resistive Wall Mode (RWM). This opens the exploration of a broad and interesting operational range otherwise excluded to standard tokamaks. Control experiments and modelling led to the design of a significant upgrade of the RFX-mod feedback control system to dramatically enhance computing power and reduce system latency. The possibility of producing D-shaped plasmas is being explore

Branching fraction and CP asymmetries of B0→KS0KS0KS0

We present measurements of the branching fraction and time-dependent CP-violating asymmetries in B0→K0SK0SK0S decays based on 227×106 Υ(4S)→BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We obtain a branching fraction of (6.9+0.9−0.8±0.6)×10−6, and CP asymmetries C=−0.34+0.28−0.25±0.05 and S=−0.71+0.38−0.32±0.04, where the first uncertainties are statistical and the second systematic

Evidence for b→dγb \to d \gamma Transitions From a Sum of Exclusive Final States in the Hadronic Final State Mass Range 1.0GeV/c2<M(Xd)<1.8GeV/c21.0 {GeV}/c^2< M(X_d)<1.8 {GeV}/c^2

16 pages, 7 postscript figures, contributed to the XXIIIrd International Symposium on Lepton and Photon Interactions at High Energies, 8/13 – 8/18/2007, Daegu, KoreaWe present preliminary results of a search for $B\to X_d\gamma$ decays with a hadronic mass 1.0 GeV/$c^

Branching fraction and CP asymmetries of B0→KS0KS0KS0

We present measurements of the branching fraction and time-dependent CP-violating asymmetries in B0→K0SK0SK0S decays based on 227×106 Υ(4S)→BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We obtain a branching fraction of (6.9+0.9−0.8±0.6)×10−6, and CP asymmetries C=−0.34+0.28−0.25±0.05 and S=−0.71+0.38−0.32±0.04, where the first uncertainties are statistical and the second systematic

Measurement of the B0→Xu−ℓ+νℓB^0\to X_{u}^- \ell^+ {\nu_\ell} decays near the kinematic endpoint of the lepton spectrum and search for violation of isospin symmetry

17 pages, 8 postscript figures, submitted to Lepton Photon 2007 - Contributed to the XXIIIrd International Symposium on Lepton and Photon Interactions at High Energies, 8/13 – 8/18/2007, Daegu, KoreaWe present the first measurement of the $B^0\to X_{u}^- \ell^+ {\nu_\ell}$ partial branching fraction in the end-point region of the lepton momentum spectrum, above the threshold for $B\to X_c\ell {\nu_\ell}$ decays. The analysis is based on a sample of 383 million $\Upsilon(4S)$ decays into $B{\bar B}$ pairs collected with the {\sc BaBar} detector at the PEP-II $e^+e^-$ storage rings. We select $B^0{\bar B}^0$ events by partially reconstructing one \B meson via the ${\bar B}^0\to D^{*+} \ell^- \bar{\nu}_\ell$ decays then select $B^0\to X_{u}^- \ell^+ {\nu_\ell}$ decays identifying a second high momentum lepton. In the momentum interval ranging from 2.3 to 2.6 GeV/c we measure the partial branching fraction $\Delta{\cal B}(B^0\to X_u\ell\nu)=(1.30\pm0.21_{stat}\pm0.07_{syst})\times 10^{-4}$ where the first error is statistical and the second is systematic. By comparing this measurement with the one obtained from untagged B decays we obtain $R^{+/0}=\Delta{\cal B}(B^0\to X_u\ell\nu)/\Delta{\cal B}(B^+\to X_u\ell\nu)= 1.18 \pm 0.35_{stat} \pm 0.17_{syst}$. Using this measurement we extract a limit on the contributions from processes breaking isospin symmetry in charmless semileptonic B decays

Measurement of the Branching Fractions of Exclusive \barB \to D/D*/D(*) \pi \ell^- \bar{\nu}_{\ell} Decays in Events Tagged by a Fully Reconstructed B Meson

19 pages, 3 postscript figures, submitted to XXIIIrd International Symposium on Lepton and Photon Interactions at High Energies, 8/13 -- 8/18/2007, Daegu, KoreaWe present a measurement of the branching fractions for anti-B -> D/D*/D(*) pi l^- anti-nu_l decays based on 341.1 fb-1 of data collected at the Upsilon(4S) resonance with the BaBar detector at the pep-II e^+e^- storage rings. Events are tagged by fully reconstructing one of the B mesons in a hadronic decay mode. We obtain BF (B^- -> D^0 l^- anti-nu_l) = (2.33 +/- 0.09(stat.) +/- 0.09(syst.))%, BF (B^- -> D^*0 l^- anti-nu_l) = (5.83 +/- 0.15(stat.) +/- 0.30(syst.))%, BF (B0bar -> D^+ l^- anti-nu_l) = (2.21 +/- 0.11(stat.) +/- 0.12(syst.))%, BF (B0bar -> D^*+ l^- anti-nu_l) = (5.49 +/- 0.16(stat.) +/- 0.25(syst.))%, BF (B^- -> D^+ pi^- l^- anti-nu_l) = (0.42 +/- 0.06(stat.) +/- 0.03(syst.))%, BF (B^- -> D^*+ pi^- l^- anti-nu_l) = (0.59 +/- 0.05(stat.) +/- 0.04(syst.))%, BF (B0bar -> D^0 pi^+ l^- anti-nu_l) = (0.43 +/- 0.08(stat.) +/- 0.03(syst.))% and BF (B0bar -> D^*0 pi^+ l^- anti-nu_l) = (0.48 +/- 0.08(stat.) +/- 0.04(syst.))%

Improved Measurement of the Cabibbo-Kobayashi-Maskawa Angle α Using B0(B¯)→ρ+ρ- Decays

We present results from an analysis of B0(B̅ 0)→ρ+ρ- using 232×106 Υ(4S)→BB̅ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We measure the longitudinal polarization fraction fL=0.978±0.014(stat)+0.021/-0.029(syst) and the CP-violating parameters SL=-0.33±0.24(stat)+0.08/-0.14(syst) and CL=-0.03±0.18(stat)±0.09(syst). Using an isospin analysis of B→ρρ decays, we determine the unitarity triangle parameter α. The solution compatible with the standard model is α=(100±13)°

Improved measurement of the Cabibbo-Kobayashi-Maskawa angle α using B0(B)→p+p- decays

We present results from an analysis of B0(B¯¯¯0)→ρ+ρ− using 232×106 Υ(4S)→BB¯¯¯ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We measure the longitudinal polarization fraction fL=0.978±0.014(stat)+0.021−0.029(syst) and the CP-violating parameters SL=−0.33±0.24(stat)+0.08−0.14(syst) and CL=−0.03±0.18(stat)±0.09(syst). Using an isospin analysis of B→ρρ decays, we determine the unitarity triangle parameter α. The solution compatible with the standard model is α=(100±13)°

Measurement of the CP violating asymmetry amplitude sin 2beta

We present results on time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 88 million Y(4S) --> B Bbar decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We study events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B0 or B0bar from its decay products. The amplitude of the CP-violating asymmetry, which in the Standard Model is proportional to sin2beta, is derived from the decay-time distributions in such events. We measure sin2beta = 0.741 +/- 0.067 (stat) +/- 0.034 (syst) and |lambda| = 0.948 +/- 0.051 (stat) +/- 0.030 (syst). The magnitude of lambda is consistent with unity, in agreement with the Standard Model expectation of no direct CP violation in these modes.Comment: 7 pages, 2 postscript figures, submitted to PR

Search for strange-pentaquark production in e+e− annihilation at √s=10.58 GeV

We search for strange pentaquark states that have been previously reported by other experiments -- the Θ(1540)+, Ξ5(1860)−−, and Ξ5(1860)0 -- in 123 fb−1 of data recorded with the BaBar detector at the PEP-II e+e− storage ring. We find no evidence for these states and set 95% confidence level upper limits on the number of Θ(1540)+ and Ξ5(1860)−− pentaquarks produced per e+e− annihilation event that are about eight and four times lower than the rates measured for ordinary baryons of similar mass