The possibility of measuring the proton electromagnetic form factors in the time-like region at FAIR with the \PANDA detector is discussed. Detailed simulations on signal efficiency for the ...annihilation of $\bar p +p $ into a lepton pair as well as for the most important background channels have been performed. It is shown that precision measurements of the differential cross section of the reaction $\bar p +p \to e^++ e^-$ can be obtained in a wide angular and kinematical range. The individual determination of the moduli of the electric and magnetic proton form factors will be possible up to a value of momentum transfer squared of $q^2\simeq 14$ (GeV/c)$^2$. The total $\bar p +p\to e^++e^-$ cross section will be measured up to $q^2\simeq 28$ (GeV/c)$^2$. The results obtained from simulated events are compared to the existing data. Sensitivity to the two photons exchange mechanism is also investigated.
We present a measurement of the time-dependent CP-violating asymmetries in $B^0 \to K^{*0}\gamma (K^{*0}\to K_S^0 \pi^0)$ decays based on 124 million $\Upsilon(4S)\to B^0\bar{B}^0$ decays collected ...with the BaBar detector at the PEP-II asymmetric-energy $B$ Factory at the Stanford Linear Accelerator Center. In a sample containing $105\pm 14$ signal decays, we measure $S_{K^{*0}} = 0.25 \pm 0.63 \pm 0.14$ and $S_{K^{*0}} = -0.57 \pm 0.32 \pm 0.09$, where the first error is statistical and the second systematic.
The possibility of measuring the proton electromagnetic form factors in the time-like region at FAIR with the
ANDA detector is discussed. Detailed simulations on signal efficiency for the ...annihilation of
+
p
into a lepton pair as well as for the most important background channels have been performed. It is shown that precise measurements of the differential cross-section of the reaction
+
p
e
-
+
e
+
can be obtained in a wide kinematical range. The determination of the ratio
R
of the moduli of the electric and magnetic proton form factors will be possible up to a value of momentum transfer squared of
q
2
≃ 14 (GeV/
c
)^2 with absolute precision from 0.01 to 0.5 (for
R
∼ 1 . The total
+
p
e
-
+
e
+
cross-section will be measured up to
q
2
≃ 28 (GeV/
c
)^2. The results obtained from simulated events are compared to the existing data. Sensitivity to the two-photon exchange mechanism is also investigated.
We present measurements of branching fractions and charge asymmetries for six B -meson decay modes with an η or η ′ meson in the final state. The data sample corresponds to 232 × 10 6 B ¯¯¯ B pairs ...collected with the BABAR detector at the PEP-II asymmetric-energy e + e − B Factory at SLAC. We measure the branching fractions (in units of 10 − 6 ): B ( B + → η π + ) = 5.1 ± 0.6 ± 0.3 , B ( B + → η K + ) = 3.3 ± 0.6 ± 0.3 , B ( B 0 → η K 0 ) = 1.5 ± 0.7 ± 0.1 ( < 2.5 at 90% C.L.), B ( B + → η ρ + ) = 8.4 ± 1.9 ± 1.1 , B ( B 0 → η ω ) = 1.0 ± 0.5 ± 0.2 ( < 1.9 at 90% C.L.), and B ( B + → η ′ π + ) = 4.0 ± 0.8 ± 0.4 , where the first uncertainty is statistical and second systematic. For the charged modes we also determine the charge asymmetries, all found to be compatible with zero.
We search for the factorization-suppressed decays B → χ c 0 K ( * ) and B → χ c 2 K ( * ) , with χ c 0 and χ c 2 decaying into J / ψ γ , using a sample of 124 × 10 6 B ¯¯¯ B events collected with the ...BABAR detector at the PEP-II storage ring of the Stanford Linear Accelerator Center. We find no significant signal and set upper bounds for the branching fractions.
Using a data sample corresponding to an integrated luminosity of 342 $fb^{-1}$ collected with the BABAR detector at the SLAC PEP-II electron-positron storage ring operating at a center-of-mass energy ...near 10.58 GeV, we measure ${\cal{B}} (\tau^- \to \pi^- \pi^- \pi^+ \nu_\tau) = (8.83 \pm 0.01 \pm 0.13) %$, ${\cal{B}} (\tau^- \to K^- \pi^- \pi^+ \nu_\tau) = (0.273\pm 0.002\pm 0.009)%$, ${\cal{B}} (\tau^- \to K^- \pi^- K^+ \nu_\tau) = (0.1346\pm 0.0010 \pm 0.0036)%$ and ${\cal{B}} (\tau^- \to K^- K^- K^+ \nu_\tau) = (1.58\pm 0.13 \pm 0.12)\times 10^{-5}$, where the uncertainties are statistical and systematic, respectively. Events where the $\pi^+\pi^-$ pair is consistent with coming from a $K^0_S$ are excluded. These are significant improvements over previous measurements, with the ${\cal{B}} (\tau^- \to K^- K^- K^+ \nu_\tau)$ result being the first resonant plus non-resonant measurement of this mode. We also report a first measurement of ${\cal{B}} (\tau^- \to \phi\pi^- \nu_\tau) = (3.42\pm 0.55 \pm 0.25)\times 10^{-5}$ and a new measurement of ${\cal{B}} (\tau^- \to \phi K^- \nu_\tau) = (3.39\pm 0.20 \pm 0.28)\times 10^{-5}$.