The European Physical Journal C

List of Papers (Total 2,687)

Automating dipole subtraction for QCD NLO calculations

In this publication the construction of an automatic algorithm to subtract infrared divergences in real QCD corrections through the Catani–Seymour dipole subtraction method [1,2] is reported. The resulting computer code has been implemented in the matrix element generator AMEGIC++ [3]. This will allow for the automatic generation of dipole subtraction terms and their integrals over ...

ATLAS sensitivity to Wtb anomalous couplings in top quark decays

We study the sensitivity of the ATLAS experiment to Wtb anomalous couplings in top pair production with semileptonic decay, pp→tt̄→W+bW-b̄ with one of the W bosons decaying leptonically and the other hadronically. Several observables are examined, including the W helicity fractions and new quantities recently introduced, such as the ratios of helicity fractions and some angular ...

Vector and axial nucleon form factors: A duality constrained parameterization

We present new parameterizations of vector and axial nucleon form factors. We maintain an excellent descriptions of the form factors at low momentum transfers, where the spatial structure of the nucleon is important, and use the Nachtman scaling variable ξ to relate elastic and inelastic form factors and impose quark–hadron duality constraints at high momentum transfers where the ...

First experience and adaptation of existing tools to ATLAS distributed analysis

The ATLAS production system has been successfully used to run production of simulation data at an unprecedented scale in ATLAS. Up to 10000 jobs were processed on about 100 sites in one day. The experiences obtained operating the system on several grid flavours was essential to perform a user analysis using grid resources. First tests of the distributed analysis system were then ...

Large-angle production of charged pions by 3-12.9 GeV/c protons on beryllium, aluminium and lead targets

Measurements of the double-differential π± production cross-section in the range of momentum 100 MeV/c≤pHARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12.9 GeV/c hitting a target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was ...

Studies of spin effects in charged Higgs boson production with an iterative discriminant analysis at the Tevatron and LHC

We report on detailed Monte Carlo comparisons of selection variables to separate tbH± signal events from the standard model tt̄ background using an iterative discriminant analysis (IDA) method. While kinematic differences exist between the two processes whenever $m_{H^\pm}{\ne}m_{W^\pm}$ , the exploration of the spin difference between the charged Higgs and the W± gauge boson ...

Search for a standard model Higgs boson in CMS via vector boson fusion in the H→WW→lνlν channel

We present the potential for discovering the standard model Higgs boson produced via the vector-boson fusion mechanism. We considered the decay of Higgs bosons to the W+W- final state, with both W-bosons subsequently decaying leptonically. The main background is tt̄ produced in association with one or more jets. This study is based on a full simulation of the CMS detector. The ...

Hadronic final states with a hard isolated photon are studied using data taken at centre-of-mass energies around the mass of the Z boson with the OPAL detector at LEP. The strong coupling αs is extracted by comparing data and QCD predictions for event shape observables at average reduced centre-of-mass energies ranging from 24 GeV to 78 GeV, and the energy dependence of αs is ...

Large-angle production of charged pions by 3 GeV/c–12 GeV/c protons on carbon, copper and tin targets

A measurement of the double-differential π± production cross-section in proton–carbon, proton–copper and proton–tin collisions in the range of pion momentum 100 MeV/c≤pc and angle 0.35 rad≤θHARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12 GeV/c hitting a target with a thickness of 5% of a nuclear ...

Study of charmonia in four-meson final states produced in two-photon collisions

We report measurements of charmonia produced in two-photon collisions and decaying to four-meson final states, where the meson is either a charged pion or a charged kaon. The analysis is based on a 395 fb-1 data sample accumulated with the Belle detector at the KEKB electron–positron collider. We observe signals for the three C-even charmonia ηc(1S), χc0(1P) and χc2(1P) in the ...

QUAERO@H1: an interface to high- $p_{\text{T}}$ HERA event data

Distributions from high-$p_{\text{T}}$ HERA event data analyzed in a general search for new physics at H1 have been incorporated into QUAERO, an algorithm designed to automate tests of specific hypo-theses with high energy collider data. The use of QUAERO@H1 to search for leptoquarks, R-parity violating supersymmetry, and excited quarks provides examples to develop intuition for ...

Independent measurement of the top quark mass and the light- and bottom-jet energy scales at hadron colliders

A method for the simultaneous determination of the energy scales for bottom-quark jets and light jets, the jet energy resolution, and the top quark mass at hadron colliders is presented. The method exploits the unique kinematics of events with top-antitop pair production, where one of the top quarks involves a leptonic and one a hadronic $W$boson decay. The paper shows a ...

Possible implications of the channeling effect in NaI(Tl) crystals

The channeling effect of low energy ions along the crystallographic axes and planes of NaI(Tl) crystals is discussed in the framework of corollary investigations on WIMP dark matter candidates. In fact, the modeling of this existing effect implies a more complex evaluation of the luminosity yield for low energy recoiling Na and I ions. In the present paper related phenomenological ...

Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions

We compare different procedures for combining fixed-order tree-level matrix-element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW and MLM schemes using different matrix-element generators and different parton cascades. We find that although similar results are obtained in all ...

In an earlier paper [1], the background for Ke3 was over estimated due to an erroneous calculation of the electron identification efficiency. The correct ratios of the partial widths involving this channel are $\mathcal{R}_{K e 3 / K2\pi} = 0.2470\pm0.0009\, ({\text{stat}})\pm0.0004\, ({\text{syst}})$ and $\mathcal{R}_{K \mu3 / Ke3} = ... Study of direct photon plus jet production in CMS experiment at \(\sqrt{s}$ = 14 TeV

We present simulation results of γ+jet analysis using CMS (compact muon solenoid) object-oriented software at the large hadron collider (LHC) center of mass energy $\sqrt{s}$ = 14 TeV. The study of direct photon production helps in validating the perturbative quantum chromodynamics (pQCD) and providing information on the gluon distribution in the nucleons. Direct photon processes ...

Study of J/ψ decaying into ωpp̄

The decay J/ψ→ωpp̄ is studied using a 5.8×107 J/ψ event sample accumulated with the BES II detector at the Beijing Electron–Positron Collider. The decay branching fraction is measured to be B(J/ψ→ωpp̄)=(9.8±0.3±1.4)×10-4. No significant enhancement near the pp̄ mass threshold is observed, and an upper limit of B(J/ψ→ωX(1860))B(X(1860)→pp̄)-5 is determined at the 95% confidence ...

Design, performance, and calibration of CMS forward calorimeter wedges

We report on the test beam results and calibration methods using high energy electrons, pions and muons with the CMS forward calorimeter (HF). The HF calorimeter covers a large pseudorapidity region ( $3\leq|\eta|\leq5$ ), and is essential for a large number of physics channels with missing transverse energy. It is also expected to play a prominent role in the measurement of ...

Annihilation-in-flight of polarised positrons with polarised electrons as an analyser of the positron polarisation from muon decay

The use of annihilation-in-flight of arbitrarily polarised positrons with arbitrarily polarised electrons as an analyser for the positron polarisation from muon decay is discussed. Analysing powers for the longitudinal and the two transverse positron polarisation components are derived and algorithms for the simulation of polarised muon decay and of annihilation-in-flight are given.

The reaction np→ppπ- from threshold up to 570 MeV

Due to a coding error, the previous paper quoted incorrect values for the differential cross sections dσ/dMpp and dσ/dΩπ * of the process np→ppπ-.