14834850
Architecture of the ATLAS online physics-selection software at LHC
Given the extremely high bunch crossing rate foreseen at the Large Hadron Collider (LHC) and the general-purpose nature of the ATLAS particle physics experiment, after the hardware-based first level trigger, an efficient and flexible trigger software is needed for the online selection of events. This filtering of events is organized in two levels: the second level trigger and the event filter. Both levels are referred together as High Level Trigger (HLT). A coherent approach to event selection across the HLT has been taken. Thus a common core software framework has been designed to maximise the usage of offline interfaces and software components, whilst allowing sufficient flexibility to meet the different interfaces and requirements of the two different levels, notably those of performance and robustness. This paper describes the architecture and high level design of the selection software and shows how the implementation meets the challenges of the ATLAS environment.
197518332
Performance of missing transverse momentum reconstructionin proton-proton collisions at √s = 7 TeV with ATLAS
The measurement of missing transverse momentum in the ATLAS detector, described in this paper, makes use of the full event reconstruction and a calibration based on reconstructed physics objects. The performance of the missing transverse momentum reconstruction is evaluated using data collected in pp collisions at a centre-of-mass energy of 7 TeV in 2010. Minimum bias events and events with jets of hadrons are used from data samples corresponding to an integrated luminosity of about 0.3 nb^(−1) and 600 nb^(−1) respectively, together with events containing a Z boson decaying to two leptons (electrons or muons) or a W boson decaying to a lepton (electron or muon) and a neutrino, from a data sample corresponding to an integrated luminosity of about 36 pb^(−1). An estimate of the systematic uncertainty on the missing transverse momentum scale is presented.
209835401
Search for events with large missing transverse momentum, jets, and at least two tau leptons in 7 TeV proton–proton collision data with the ATLAS detector
A search for events with large missing transverse momentum, jets, and at least two tau leptons has been performed using 2 fb(-1) of proton-proton collision data at root s = 7 TeV recorded with the ...
55159826
Full supersymmetry simulation for ATLAS in DC1
This note reports results from a simulation of 100k events for one example of a minimal SUGRA supersymmetry case at the LHC using full simulation of the ATLAS detector. It was carried out as part ATLAS Data Challenge 1.
121553628
Calibration of the Yangbajing Air-shower Core detector using the test beam of BEPCII
Yangbajing Air shower Core detector(YAC) has been developed for the next phase of Tibet air-shower experiment to measure the chemical composition of cosmic rays in “knee” region. A preparation is made for calibration of the linearity of the dynamic range and position dependence of light yield of YAC using test beam of BEPCII. A scraper will be used to attenuate the electron beam intensity from about 10 10 /pulse to 10 2 –10 6 /pulse. A Faraday cup, a thick ionization chamber and a thin ionization chamber are being manufactured to monitor the beam intensity covering dynamic range from 10 2 /pulse to 10 10 /pulse.
206324074
Determination of the branching ratio of the decay pi 0-->e+e-
Employing the decay chain K + →π + p 0 , π 0 →e + e - we have observed the decay π 0 →e + e - . With a signal sample of ≃21 events we measure the branching ratio for π 0 →e + e - to be (6.9±2.3±0.6)×10 -8 , normalized to the decay K + →π + p 0 , π 0 →e + e - γ. This result is consistent with the unitarity lower bound and the published 90% confidence level upper limit of 13×10 -8
119257183
Observation of the decay $\psi(3686)$ $\rightarrow$ $\Lambda\bar\Sigma^{\pm}\pi^{\mp}+c.c.$
Using a sample of $1.06\times10^{8}$ $\psi(3686)$ events collected with the BESIII detector, we present the first observation of the decays of $\psi(3686)$ $\rightarrow$ $\Lambda\bar\Sigma^{+}\pi^{-}+c.c.$ and $\psi(3686)$ $\rightarrow$ $\Lambda\bar\Sigma^{-}\pi^{+}+c.c.$. The branching fractions are measured to be $\mathcal{B}(\psi(3686) \rightarrow \Lambda\bar\Sigma^{+}\pi^{-} + c.c.)=(1.40\pm 0.03 \pm 0.13)\times10^{-4}$ and $\mathcal{B}(\psi(3686) \rightarrow \Lambda\bar\Sigma^{-}\pi^{+}+c.c.)=(1.54\pm 0.04 \pm 0.13)\times10^{-4}$, where the first errors are statistical and the second ones systematic.
119274043
Partial wave analysis of $J/\psi \to \gamma \eta \eta$
Based on a sample of $2.25\times 10^{8}$ $J/\psi$ events collected with the BESIII detector at BEPCII, a full partial wave analysis on $J/\psi\to\gamma\eta\eta$ was performed using the relativistic covariant tensor amplitude method. The results show that the dominant $0^{++}$ and $2^{++}$ components are from the $f_0(1710)$, $f_0(2100)$, $f_0(1500)$, $f_2'(1525)$, $f_2(1810)$ and $f_2(2340)$. The resonance parameters and branching fractions are also presented.
120632182
Direct measurements of the branching fractions for inclusive K± and inclusive semileptonic decays of D+ and D0 mesons
Abstract With singly-tagged D ¯ samples selected from the data collected at and around 3.773 GeV with the BESII detector at the BEPC collider, we have measured the branching fractions for the inclusive K ± decays of D + and D 0 mesons, which are BF ( D + → K − X ) = ( 24.7 ± 1.3 ± 1.2 ) % , BF ( D + → K + X ) = ( 6.1 ± 0.9 ± 0.4 ) % , BF ( D 0 → K − X ) = ( 57.8 ± 1.6 ± 3.2 ) % and BF ( D 0 → K + X ) = ( 3.5 ± 0.7 ± 0.3 ) % , respectively. We have also measured the branching fractions for the inclusive semileptonic decays of D + and D 0 mesons to be BF ( D + → e + X ) = ( 15.2 ± 0.9 ± 0.8 ) % and BF ( D 0 → e + X ) = ( 6.3 ± 0.7 ± 0.4 ) % . These yield the ratio of their partial widths to be Γ ( D + → e + X ) / Γ ( D 0 → e + X ) = 0.95 ± 0.12 ± 0.07 .
118073401
Observation of $\eta_{c}$ decay into $\Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$ final states
Using a data sample of $2.25\times10^{8}$ $J/\psi$ events collected with the BESIII detector, we present the first observation of the decays of $\eta_{c}$ mesons to $\Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$. The branching fractions are measured to be $(2.11\pm0.28_{\rm stat.}\pm0.18_{\rm syst.}\pm0.50_{\rm PDG})\times10^{-3}$ and $(0.89\pm0.16_{\rm stat.}\pm0.08_{\rm syst.}\pm0.21_{\rm PDG})\times10^{-3}$ for $\eta_{c} \to \Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$, respectively. These branching fractions provide important information on the helicity selection rule in charmonium-decay processes.
119218964
Coherence and broadening effects in medium induced gluon radiation
Abstract Interferences between different emitters in the multi-parton shower is the building block of QCD jet physics in vacuum. The presence of a hot medium made of quarks and gluons is expected to alter this interference pattern. To study such effects, we derive the gluon emission spectrum off an “asymptotic quark” traversing a hot and dense QCD medium at first order in the medium density. The resulting induced gluon distribution gets modified when the new interference terms between the initial and final quark are included. We comment on the possible phenomenological consequences of this new contribution for jet observables in heavy-ion collisions.