Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal

Measurement of the production of a W boson in association with a charm quark in pp collisions at √s = 7 TeV with the ATLAS detector

The production of a W boson in association with a single charm quark is studied using 4.6 fb−1 of pp collision data at s√ = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96+0.26−0.30 at Q 2 = 1.9 GeV2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio σ(W + +c¯¯)/σ(W − + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s−s¯¯¯ quark asymmetry

Measurement of χ c1 and χ c2 production with s√ = 7 TeV pp collisions at ATLAS

The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at s√ = 7 TeV with the ATLAS detector at the LHC using 4.5 fb−1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ −) where photons are reconstructed from γ → e + e − conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured

Measurement of the flavour composition of dijet events in pp collisions at root s=7 TeV with the ATLAS detector

This paper describes a measurement of the flavour composition of dijet events produced in pp collisions at √s=7 TeV using the ATLAS detector. The measurement uses the full 2010 data sample, corresponding to an integrated luminosity of 39 pb−1. Six possible combinations of light, charm and bottom jets are identified in the dijet events, where the jet flavour is defined by the presence of bottom, charm or solely light flavour hadrons in the jet. Kinematic variables, based on the properties of displaced decay vertices and optimised for jet flavour identification, are used in a multidimensional template fit to measure the fractions of these dijet flavour states as functions of the leading jet transverse momentum in the range 40 GeV to 500 GeV and jet rapidity |y|<2.1. The fit results agree with the predictions of leading- and next-to-leading-order calculations, with the exception of the dijet fraction composed of bottom and light flavour jets, which is underestimated by all models at large transverse jet momenta. The ability to identify jets containing two b-hadrons, originating from e.g. gluon splitting, is demonstrated. The difference between bottom jet production rates in leading and subleading jets is consistent with the next-to-leading-order predictions

Evidence for the h_b(1P) meson in the decay Upsilon(3S) --> pi0 h_b(1P)

Using a sample of 122 million Upsilon(3S) events recorded with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we search for the $h_b(1P)$ spin-singlet partner of the P-wave chi_{bJ}(1P) states in the sequential decay Upsilon(3S) --> pi0 h_b(1P), h_b(1P) --> gamma eta_b(1S). We observe an excess of events above background in the distribution of the recoil mass against the pi0 at mass 9902 +/- 4(stat.) +/- 2(syst.) MeV/c^2. The width of the observed signal is consistent with experimental resolution, and its significance is 3.1sigma, including systematic uncertainties. We obtain the value (4.3 +/- 1.1(stat.) +/- 0.9(syst.)) x 10^{-4} for the product branching fraction BF(Upsilon(3S)-->pi0 h_b) x BF(h_b-->gamma eta_b).Comment: 8 pages, 4 postscript figures, submitted to Phys. Rev. D (Rapid Communications

Search for a CP-odd Higgs boson decaying to Zh in pp collisions at √s=8TeV with the ATLAS detector

A search for a heavy, CP-odd Higgs boson, A, decaying into a Zboson and a 125GeV Higgs boson, h, with the ATLAS detector at the LHC is presented. The search uses proton–proton collision data at a centre-of-mass energy of 8TeV corresponding to an integrated luminosity of 20.3fb−1. Decays of CP-even hbosons to ττor bbpairs with the Zboson decaying to electron or muon pairs are considered, as well as h →bbdecays with the Zboson decaying to neutrinos. No evidence for the production of an Aboson in these channels is found and the 95% confidence level upper limits derived for σ(gg→A) ×BR(A →Zh) ×BR(h →f¯f)are 0.098–0.013pb for f=τand 0.57–0.014pb for f=bin a range of mA=220–1000GeV. The results are combined and interpreted in the context of two-Higgs-doublet models. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 8 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three leptons and missing transverse momentum is presented. The analysis is based on 20.3 fb−1 of s√ = 8 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with the Standard Model expectations and limits are set in R-parity-conserving phenomenological Minimal Supersymmetric Standard Models and in simplified supersymmetric models, significantly extending previous results. For simplified supersymmetric models of direct chargino (χ˜±1) and next-to-lightest neutralino (χ˜02) production with decays to lightest neutralino (χ˜01) via either all three generations of sleptons, staus only, gauge bosons, or Higgs bosons, (χ˜±1) and (χ˜02) masses are excluded up to 700 GeV, 380 GeV, 345 GeV, or 148 GeV respectively, for a massless (χ˜01

Observation of top-quark pair production in association with a photon and measurement of the ttγ production cross section in pp collisions at √s = 7 TeV using the ATLAS detector

A search is performed for top-quark pairs (tt) produced together with a photon (γ) with transverse energy greater than 20 GeV using a sample of tt candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The data set used corresponds to an integrated luminosity of 4.59 fb −1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. In total, 140 and 222 ttγ candidate events are observed in the electron and muon channels, to be compared to the expectation of 79 +/- 26 and 120 +/- 39 non-ttγ background events, respectively. The production of ttγ events is observed with a significance of 5.3 standard deviations away from the null hypothesis. The ttγ production cross section times the branching ratio (BR) of the single-lepton decay channel is measured in a fiducial kinematic region within the ATLAS acceptance. The measured value is σ (fid/tty) × BR = 63 +/- 8(stat) (+17/-13)(syst) +/- 1 lumi fb per lepton flavor, in good agreement with the leading-order theoretical calculation normalized to the next-to-leading-order theoretical prediction of 48 +/- 10 fb

Membaca Pengadilan Hubungan Industrial di Indonesia: Penelitian Putusan Mahkamah Agung pada Lingkup Pengadilan Hubungan Industrial 2006-2013

Akhirnya langkah panjang dan inisiasi kami untuk mewujudkan adanya indeks putusan Pengadilan serta Penelitian terhadap Putusan-putusan Pengadilan Hubungan Industrial ini bisa diselesaikan. Penelitian ini muncul sebagai concern LBH Jakarta terhadap advokasi perburuhan, khususnya advokasi melalui Pengadilan Hubungan Industrial (PHI). Praktik PHI menyisakan banyak problem, diantaranya konsep hukum publik yang menempatkan buruh sebagai kelompok lemah yang harus dilindungi, menjadi hukum privat yang mengasumsikan kedudukan buruh setara dengan pengusaha. Selain itu, atas putusan-putusan PHI masih banyak menyisakan persoalan eksekusi yang harus ditempuh buruh melalui mekanisme perdata lain di pengadilan negeri. Pun masih menyisakan persoalan lagi dengan kualitas putusan yang di dalamnya ditemui pengurangan-pengurangan hak yang seharusnya secara riil diperoleh oleh buruh. Namun karena kondisinya yang lemah, mau tidak mau buruh menempuh mekanisme PHI sebagai satu-satunya jalan untuk meminta hak-haknya kepada pengusaha. Karena itulah LBH Jakarta berinisiatif mengadakan penelitian ini untuk membaca pengadilan hubungan industrial di Mahkamah Agung sebagai muara atas seluruh kasus PHI di Indonesia