Search for diphoton events with large missing transverse energy with 36 pb−1 of 7 TeV proton–proton collision data with the ATLAS detector
Making use of 36 pb−1 of proton–proton collision data at $\sqrt{s} =7$ TeV, the ATLAS Collaboration has performed a search for diphoton events with large missing transverse energy. Observing no excess of events above the Standard Model prediction, a 95% Confidence Level (CL) upper limit is set on the cross section for new physics of σ<0.38−0.65 pb in the context of a generalised model of gauge-mediated supersymmetry breaking (GGM) with a bino-like lightest neutralino, and of σ<0.18−0.23 pb in the context of a specific model with one universal extra dimension (UED). A 95% CL lower limit of 560 GeV, for bino masses above 50 GeV, is set on the GGM gluino mass, while a lower limit of 1/R>961 GeV is set on the UED compactification radius R. These limits provide the most stringent tests of these models to date.

title: The ATLAS High Level Trigger Steering
abstract: The High Level Trigger (HLT) of the ATLAS experiment at the Large Hadron Collider receives events which pass the LVL1 trigger at ~75 kHz and has to reduce the rate to ~200 Hz while retaining the most interesting physics. It is a software trigger and performs the reduction in two stages: the LVL2 trigger and the Event Filter (EF). At the heart of the HLT is the Steering software. To minimise processing time and data transfers it implements the novel event selection strategies of seeded, step-wise reconstruction and early rejection. The HLT is seeded by regions of interest identified at LVL1. These and the static configuration determine which algorithms are run to reconstruct event data and test the validity of trigger signatures. The decision to reject the event or continue is based on the valid signatures, taking into account pre-scale and pass-through. After the EF, event classification tags are assigned for streaming purposes. Several powerful new features for commissioning and operation have been added: comprehensive monitoring is now built in to the framework; for validation and debugging, reconstructed data can be written out; the steering is integrated with the new configuration (presented separately), and topological and global triggers have been added. This paper will present details of the final design and its implementation, the principles behind it, and the requirements and constraints it is subject to. The experience gained from technical runs with realistic trigger menus will be described.

title: Measurement of $\cos_{2beta}$ in $B^0 \to D^{(*)}$ 0 h0 decays with a time-dependent Dalitz plot analysis of $D^0 \to K^0_{s} \pi^{+} \pi^{-}$
abstract: We report a preliminary measurement of $\cos2\beta$ in $B^0\to D^{(*)0}h^0$ decays with a time-dependent Dalitz plot analysis of $D^0\to K_S\pi^+\pi^-$, where $h^0$ is a light neutral meson such as $\pi^0$, $\eta$, $\eta'$ or $\omega$. The strong phase variation on the Dalitz plot allows the access to the angle $\beta$ with only a two-fold ambiguity ($\beta+\pi$). Using $311\times 10^{6}$ $B\bar{B}$ pairs collected at the Babar detector, we obtain $\cos2\beta = 0.54 \pm 0.54 \pm 0.08 \pm 0.18$, $\sin2\beta = 0.45 \pm 0.36 \pm 0.05 \pm 0.07$, and $|\lambda| = 0.975^{+0.093}_{-0.085} \pm 0.012 \pm 0.002 $, where the first errors are statistical, the second are experimental systematic uncertainties, and the third are the signal Dalitz model uncertainties. This measurement favors the solution of $\beta= 22^\circ$ over $68^\circ$ at an 87% confidence level.

title: Evidence for the $B^0 \to \rho^0 \rho^0$ decay and implications for the CKM angle $\alpha$
abstract: We search for the decays B0->rho0rho0, B0->rho0f0, and B0->f0f0 in a sample of about 348 million Upsilon(4S)->BBbar decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We find evidence for B0->rho0rho0 with 3.0 sigma significance and measure the branching fraction B = (1.16 +0.37-0.36 +-0.27) 10^{-6} and longitudinal polarization fraction f_L = 0.86 +0.11-0.13 +-0.05. As a consequence, the uncertainty on the CKM unitarity angle alpha due to penguin contributions in B->rhorho decays is estimated to be 18 degrees at 1 sigma level. We also set upper limits on the B0->rho0f0 and B0->f0f0 decay rates. All results are preliminary.

title: Measurement of moments of the hadronic-mass and energy spectrum in inclusive semileptonic anti-B ---> X(c) l- anti-nu decays

title: Search for quark contact interactions in dijet angular distributions in pp collisions at s=7 TeV measured with the ATLAS detector
abstract: Dijet angular distributions from the first LHC pp collisions at center-of-mass energy sqrt(s) = 7 TeV have been measured with the ATLAS detector. The dataset used for this analysis represents an integrated luminosity of 3.1 pb-1. Dijet $\chi$ distributions and centrality ratios have been measured up to dijet masses of 2.8 TeV, and found to be in good agreement with Standard Model predictions. Analysis of the $\chi$ distributions excludes quark contact interactions with a compositeness scale $\Lambda$ below 3.4 TeV, at 95% confidence level, significantly exceeding previous limits.

title: Partial wave analysis using graphics processing units
abstract: Partial wave analysis is an important tool for determining resonance properties in hadron spectroscopy. For large data samples however, the un-binned likelihood fits employed are computationally very expensive. At the Beijing Spectrometer (BES) III experiment, an increase in statistics compared to earlier experiments of up to two orders of magnitude is expected. In order to allow for a timely analysis of these datasets, additional computing power with short turnover times has to be made available. It turns out that graphics processing units (GPUs) originally developed for 3D computer games have an architecture of massively parallel single instruction multiple data floating point units that is almost ideally suited for the algorithms employed in partial wave analysis. We have implemented a framework for tensor manipulation and partial wave fits called GPUPWA. The user writes a program in pure C++ whilst the GPUPWA classes handle computations on the GPU, memory transfers, caching and other technical details. In conjunction with a recent graphics processor, the framework provides a speed-up of the partial wave fit by more than two orders of magnitude compared to legacy FORTRAN code.

title: The Mu3e Experiment
abstract: The Mu3e experiment is designed to search for charged lepton flavour violation in the process μ + → e + e − e + with a branching ratio sensitivity of 10 − 16 . This requires a detector capable of coping with rates of up to 2  9 muons/s whilst being able to reduce backgrounds from accidental coincidences and the process μ + → e + e − e + ν ¯ μ ν e to below the 10 − 16 level. The use of 50 μ m thin high-voltage monolithic active pixel sensors in conjunction with an innovative tracking concept provide the momentum and position resolution necessary, whilst the timing resolution is provided by a combination of scintillating fibres and tiles. The recently approved Mu3e experiment will be located at the Paul Scherrer Institute in Switzerland and is currently preparing for detector construction.

title: Measurement of diffractive Φ meson photoproduction at HERA with the H1 fast track trigger
abstract: A new measurement of diffractive φ meson photoproduction is performed with the H1 experiment at the electron-proton collider HERA. In the kinematic range 30 < Wγp < 90 GeV and 0.2 < |t| < 1.5 GeV, cross sections are determined double differentially in Wγp and t. From these data, the pomeron trajectory in elastic φ meson photoproduction is determined to be α(t) = 1.15 ± 0.05(stat. A combined fit with data from fixed target experiments and the ZEUS collaboration yields the most precise trajectory measurement using φ mesons to date, α(t) = 1.122 ± 0.008 + t · (0.150 ± 0.017) GeV. The spin density matrix elements, which provide information on the helicity structure of the interaction, are extracted using measurements of angular distributions of the φ meson decay products and are found to be in agreement with expectations from s-channel helicity conservation. The presented cross section measurement was made possible by the Fast Track Trigger (FTT). This new trigger based on signals from selected wire layers of the H1 central drift chamber provides information to the first three trigger levels of the H1 experiment. The first level performs a coarse two-dimensional track reconstruction within 2 μs, whilst the second trigger level reconstructs the event vertex along the beam line, performs a precise three-dimensional track fit and determines invariant masses of track pairs in 20 μs. The third trigger level reconstructs final states from up to 48 tracks and allows for particle identification using information from the calorimeter and the muon system within 100 μs. Zusammenfassung Mit dem H1-Experiment am Elektron-Proton-Beschleuniger HERA wird eine neue Messung diffraktiver φ-Meson-Photoproduktion durchgeführt. Im kinematischen Bereich 30 < Wγp < 90 GeV und 0.2 < |t| < 1.5 GeV werden Wirkungsquerschnitte doppeltdifferenziell in Wγp und t gemessen. Aus diesen Daten bestimmt sich die PomeronTrajektorie in elastischer φ-Meson-Photoproduktion zu α(t) = 1.15 ± 0.05(stat. Eine gemeinsame Anpassung mit Daten von Experimenten mit ruhendem Target und der ZEUS-Kollaboration liefert die bisher genaueste Messung der Trajektorie mit Hilfe von φ-Mesonen: α(t) = 1.122 ± 0.008 + t · (0.150 ± 0.017) GeV. Aus der Messung der Winkelverteilung der φ-Meson-Zerfallsprodukte werden drei Elemente der Spindichtematrix bestimmt. Diese sind verträglich mit s-Kanal-Helizitätserhaltung. Die vorliegende Messung wurde durch den schnellen Spurtrigger (Fast Track Trigger, FTT) ermöglicht. Dieser neue Trigger leitet aus Signalen von ausgewählten Drahtlagen der zentralen Spurkammer von H1 Informationen für die ersten drei Triggerstufen des H1 Experimentes ab. Auf der ersten Stufe wird innert 2 μs eine grobe, zweidimensionale Spurrekonstruktion durchgeführt. In 20 μs rekonstruiert die zweite Stufe den EreignisVertex entlang der Strahllinie, führt eine präzise, dreidimensionale Spuranpassung durch und bestimmt die invariante Masse von Spurpaaren. Auf der dritten Stufe werden innert 100 μs aus bis zu 48 Spuren Endzustände rekonstruiert und mit Hilfe von Informationen aus dem Kalorimeter und dem Myon-System Teilchen identifiziert.

title: Inclusive Hadronic Results at BaBar: ISR and Pentaquark Searches
abstract: We present recent measurements of hadronic cross-sections from the BaBar experiment and report preliminary results on searches for pentaquark states. Studies of hadronic cross-sections using initial-state radiation offer promising prospects at BaBar. Many exclusive channels have already been measured, and more are in progress. A fully inclusive analysis should also offer a precise measurement of {Delta}{alpha}{sub QED}{sup Had}. Searches for pentaquark states have so far been negative, but they have served to highlight the potential for the study of charmed and non-charmed baryons at high-luminosity e{sup +}e{sup -} colliders.