Nuclear physics. B, Proceedings, supplements最新文献

The BaBar collaboration has nearly completed a program of precise measurements of the cross sections for the dominant channels of $e^{+}{e}^{-}\to \mathrm{hadrons}$ from threshold to an energy of 3–5 GeV using the initial-state radiation (ISR) method, i.e. the measurement of the cross sections $e^{+}{e}^{-}\to \gamma \mathrm{hadrons}$ with the energetic γ detected at large angle to the beams. These data are used as input to vacuum polarization dispersion integrals, in particular the hadronic contribution to the muon $g-2$ anomaly. In addition to the recently measured ${\pi }^{+}{\pi }^{-}$ cross section, giving the dominant contibution, many multihadronic channels have been investigated, with some recent examples presented here. We give preliminary results for the process $e^{+}{e}^{-}\to K^{+}{K}^{-}\left(\gamma \right)$ using $232{\text{fb}}^{-1}$ of data collected with the BaBar detector at $e^{+}{e}^{-}$ center-of-mass energies near 10.6 GeV. The lowest-order contribution to the hadronic vacuum polarization term in the muon magnetic anomaly is obtained for this channel: $a_{\mu }^{KK,LO}=(22.95\pm {0.14}_{\text{(stat)}}\pm {0.22}_{\text{(syst)}})\times {10}^{-10}$, which is about a factor of three more precise than the previous world average value.

The progress on the detector and accelerator in the Belle II experiment is presented. The B factories have successfully accumulated the experimental data at $\Upsilon \left(4S\right)$ and achieved the world highest sensitivity on the search for lepton flavor violating tau decays and other new physics searches. The Belle II experiment will obtain 50 times larger data samples compared to the Belle experiment and improve the detector sensitivity. The construction of the detector and accelerator is in progress. The commissioning will start in 2014 and the expected integrated luminosity is 50ab⁻¹ by 2022.

Results are presented from the ATLAS and CMS searches for charged Higgs bosons, supersymmetry, and exotica with tau leptons in the final state. The analyses discussed use a dataset corresponding to 5 fb⁻¹ of integrated luminosity from $\sqrt{s}=7\text{TeV}$ proton–proton collisions at the LHC in 2011.

We review our recent determination of the strong coupling ${\alpha }_s$ from the OPAL data for non-strange hadronic tau decays. We find that ${\alpha }_s\left(m_{\tau }^2\right)=0.325\pm 0.018$ using fixed-order perturbation theory, and ${\alpha }_s\left(m_{\tau }^2\right)=0.347\pm 0.025$ using contour-improved perturbation theory. At present, these values supersede any earlier determinations of the strong coupling from hadronic tau decays, including those from ALEPH data.

We present the results of a partial upgrade to the Monte Carlo event generator TAUOLA using Resonance Chiral Theory for the two and three meson final states. These modes account for 88% of total hadronic width of the tau meson. The first results of the model parameters have been obtained using Preliminary BaBar data for 3π mode.

The importance of tau leptons in new physics searches at the LHC led the CMS collaboration to design a specific algorithm, the Hadron Plus Strip (HPS) algorithm, for the reconstruction and identification of taus decaying hadronically (${\tau }_{\mathrm{had}}$). The HPS algorithm makes use of a particle description of the event to identify hadronic decay modes of τ leptons through the reconstruction of intermediate resonances. It also provides discriminators against potentially large backgrounds from quarks, gluons and light leptons (electrons and muons). Moreover, thanks to the particle event reconstruction avalaible in CMS, a fast online hadronic tau reconstruction can be performed allowing the development of efficient tau trigger selections which allow to perform a broad range of physics analysis. This report describes the ${\tau }_{\mathrm{had}}$ reconstruction and identification of the HPS algorithm and its performances, studied in simulated $Z\to \tau \tau$ events and in samples of proton-proton collision data collected during 2011 and 2012 data-taking at $\sqrt{s}=7\mathrm{TeV}\text{and}8\mathrm{TeV}$, respectively. Finally, the performance of the tau trigger selections is presented.

Using as an input the data obtained by the L3 and OPAL Collaborations for the reaction $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}\gamma$ at the $Z_1$-pole, we obtained bounds on the electromagnetic and weak dipole moments of the tau-lepton in the context of a 331 model. Our bounds on the electromagnetic moments are consistent with the bounds obtained by the L3 and OPAL Collaborations for the reaction $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}\gamma$. We also obtained bounds on the tau weak dipole moments which are consistent with the bounds obtained recently by the DELPHI, ALEPH and BELLE Collaborations from the reaction $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}$. Our work complements other studies on the electromagnetic and weak dipole moments of the tau-lepton.

The lifetime of the τ-lepton is measured using the process $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}$, where both τ-leptons decay to $3\pi \nu$. The preliminary result based on 711 fb⁻¹ of data collected on the $\Upsilon \left(4S\right)$ resonance and in the nearby continuum is ${\tau }_{\tau }=(290.18\pm 0.54(\text{stat.})\pm 0.33(\text{syst.}\left)\right)\times {10}^{-15}\text{s}$.

The IceCube Neutrino Observatory at the geographic South Pole was designed with the primary goal of discovering high energy neutrinos from astrophysical objects such as active galactic nuclei and gamma ray bursts. IceCube completed construction in 2010 and has been collecting data throughout the construction phase. IceCube is sensitive to all three flavors of neutrinos, each of which has a distinct topological signature within the detector. At sufficiently high energies, the tau neutrino signature is a “double bang” from the charged current interaction of the neutrino and the decay of the tau lepton. At high energies, the tau neutrino has negligible background and would be an intriguing astrophysical signature. A dedicated search for ultra-high energy tau neutrinos (340 TeV–200 PeV) was performed using data from the partial IceCube detector, yielding a 90% CL upper limit of $E_{\nu }^2{\Phi }_{90}\left({\nu }_x\right)<16.3\times {10}^{-8}\text{GeV}{\text{cm}}^{-2}{\text{sr}}^{-1}{\text{s}}^{-1}$ on a diffuse astrophysical flux of UHE neutrinos.