121204919
Construction, assembly and tests of the ATLAS electromagnetic barrel calorimeter
The construction and assembly of the two half barrels of the ATLAS central electromagnetic calorimeter and their insertion into the barrel cryostat are described. The results of the qualification tests of the calorimeter before installation in the LHC ATLAS pit are given.
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.
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.
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
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 ...
125000747
Search for the rare decays J/psi ---> D-(s) e+ nu(e), J/psi ---> anti-D0 e+ e-
Abstract We report on a search for the decays J / ψ → D s − e + ν e + c.c. , J / ψ → D − e + ν e + c.c. , and J / ψ → D 0 ¯ e + e − + c.c. in a sample of 5.8 × 10 7 J / ψ events collected with the BESII detector at the BEPC. No excess of signal above background is observed, and 90% confidence level upper limits on the branching fractions are set: B ( J / ψ → D s − e + ν e + c.c. ) 4.9 × 10 −5 , B ( J / ψ → D − e + ν e + c.c. ) 1.2 × 10 −5 , and B ( J / ψ → D 0 ¯ e + e − + c.c. ) 1.1 × 10 −5 .
118664066
Medium-induced multi-photon radiation
We study the spectrum of multi-photon radiation off a fast quark in medium in the BDMPS/ASW approach. We reproduce the medium-induced one-photon radiation spectrum in dipole approximation, and go on to calculate the two-photon radiation in the Moliere limit. We find that in this limit the LPM effect holds for medium-induced two-photon ladder emission.
120036551
Recent Results at BESIII
The BESIII detector operating at the BEPCII e+e− collider collected 2.25 × 108J/ψ events, 1.06 × 108 ψ(3686) events, 2.9 fb−1 data at $${\sqrt s}$$ = 3.773 GeV and 477 pb−1 data at $${\sqrt s}$$ = 4.01 GeV, respectively, by the end of 2011. We report some recent results on light hadron spectroscopy, charmonium spectroscopy and charm physics, which are obtained by analyses of these data.
118484384
Study of $J/\psi\to p\bar{p}$ and $J/\psi\to n\bar{n}$
The decays $J/\psi\to p\bar{p}$ and $J/\psi\to n\bar{n}$ have been investigated with a sample of 225.2 million $J/\psi$ events collected with the BESIII detector at the BEPCII $e^+e^-$ collider. The branching fractions are determined to be $\mathcal{B}(J/\psi\to p\bar{p})=(2.112\pm0.004\pm0.031)\times10^{-3}$ and $\mathcal{B}(J/\psi\to n\bar{n})=(2.07\pm0.01\pm0.17)\times10^{-3}$. Distributions of the angle $\theta$ between the proton or anti-neutron and the beam direction are well described by the form $1+\alpha\cos^2\theta$, and we find $\alpha=0.595\pm0.012\pm0.015$ for $J/\psi\to p\bar{p}$ and $\alpha=0.50\pm0.04\pm0.21$ for $J/\psi\to n\bar{n}$. Our branching-fraction results suggest a large phase angle between the strong and electromagnetic amplitudes describing the $J/\psi\to N\bar{N}$ decay.
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.